Dan Emergency Oxygen Handbook v3
Dan Emergency Oxygen Handbook v3
Dan Emergency Oxygen Handbook v3
Student
Handbook
Divers Alert Network +1 919-684-2948
DAN Medical Information Line: +1 919-684-2948 ext. 6222
DAN Emergency Hotline: +1-919-684-9111
Contributors and Reviewers: Jim Chimiak, M.D.; Petar Denoble, M.D., D.Sc.;
Matias Nochetto, M.D.; Patty Seery, MHS, DMT; Jim Gunderson, BSc, BA; Brandon Brownell;
Robert Soncini; Doug Carlson; Vin Malkoski; Louise White; William Tong; Michael Steidley
This program meets the current (as of December 2020) consensus on Guidelines for Resuscitation from the
International Liaison Council on Resuscitation (ILCOR) and as issued by its member organizations including the
American Heart Association (AHA), the European Council on Resuscitation (ERC), the Heart and Stroke Foundation
of Canada (including the course requirements for CPR-C in Canada), Australia New Zealand Council on
Resuscitation (ANZCOR), the Resuscitation Council of South Africa, the InterAmerican Heart Foundation, and the
Resuscitation Council of Asia.
9th Edition, Rev 3.0, March 2021
©2021 Divers Alert Network
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any
form or by any means, electronic, mechanical, photocopying, or otherwise without prior written permission of Divers
Alert Network, 6 West Colony Place, Durham, NC 27705.
Eighth edition published December 2017; Seventh edition published March 2012; sixth edition, May 2006; fifth
edition, September 2002; fourth edition, February 1997; third edition, November 1994; second edition, April 1994;
first edition, November 1993.
Table of Contents
Summary ........................................................................ 64
Review Answers ............................................................ 65
Glossary .......................................................................... 66
References ..................................................................... 70
Chapter 1: Course Overview
Scuba diving injuries are rare and are often subtle when they occur. In the unlikely event of an
injury, being able to recognize the problem and initiate appropriate action can speed the diver’s
recovery and minimize lasting effects. Oxygen first aid is one of the initial responses for diving
injuries.
The Emergency Oxygen for Scuba Diving Injuries (EO2) course is an entry-level training program
that teaches participants common presentations of dive injuries and how to provide emergency
oxygen first aid.
During this course, participants will become familiar with the signs and symptoms associated
with decompression illness and nonfatal drowning and the proper administration of supplemental
oxygen. Proper assembly, disassembly and use of all component parts found in the DAN Oxygen
Unit are included in the skills section of this course.
Successful completion of the Emergency Oxygen for Scuba Diving Injuries course includes
demonstrating skill competency and passing a final knowledge assessment. Upon completion,
you will receive a provider card indicating that you have been trained in administration of oxygen
for scuba diving and drowning injuries.
After you have completed the required e-learning and the skills-development portion of the
course with your DAN Instructor, your instructor will process your credentials. You can find your
credential card(s), in your e-learning profile at dan.diverelearning.com under the “completed” tab,
by selecting the course you want. There you will see a grey ‘course record’ box with information
about your course. To the right of that grey box you will see your credential card. You can click
on that image and then either print it or save it as an image file. If your course is approved by the
United States Coast Guard, there will also be a wall certificate available.
Reading this handbook without instruction and practice will not make
someone competent to use oxygen in a diving emergency.
Prerequisites
A current certification in full cardiopulmonary resuscitation (CPR) is a prerequisite for this program.
Certification is accepted from any recognized organization. If you are not yet certified in CPR,
please talk with your EO2 Instructor about becoming CPR certified before starting this course.
There is no minimum age requirement to participate in this course. Some countries, states and
local municipalities may have minimum age stipulations for the use of emergency oxygen.
Scuba Certification
Scuba diving certification is not a course prerequisite. This course teaches scuba divers and
interested nondivers how to provide emergency oxygen first aid to injured divers. Familiarity with
diving equipment and diving terminology will make understanding the material easier. However,
interested and informed nondivers should be able to master the material.
Retraining
Emergency-response skills deteriorate with time. Retraining is required every two years to
maintain Emergency Oxygen for Scuba Diving Injuries Provider certification, and regular practice is
encouraged to retain proficiency. All skills performed in an emergency should be within the scope
of one’s training.
Continuing Education
Continuing education is encouraged in the form of additional training courses, supervised practice
sessions, reading current literature and refresher training. Your EO2 Instructor can provide
information about these programs.
Terminology
This student handbook introduces medical terms that may be unfamiliar to some readers.
Familiarity with basic medical terminology will enhance the quality of communication with
emergency and health care workers. A glossary of terms is provided in the back of this handbook.
Objectives
1. What is oxygen?
2. How much oxygen is in both inhaled and exhaled air as we breathe?
3. How is oxygen transported to body tissues?
4. What is carbon dioxide, and how is it eliminated from the body?
5. What is nitrogen?
6. What is carbon monoxide, and why is it dangerous?
The air we breathe is composed of many different gases. One is critical to our survival; others play
a significant role when we breathe under pressure while scuba diving. This chapter provides a
brief overview of some of these atmospheric gases and the role they may play under pressure.
Oxygen (O2)
Oxygen is a colorless, odorless, tasteless gas that composes approximately 21 percent of the
Earth’s atmosphere. It is a vital element for survival and is needed for cellular metabolism. We may
experience discomfort, unconsciousness or death within minutes when oxygen supplies are
inadequate (hypoxia) or absent (anoxia).
Inhaled oxygen is primarily transported from the alveolar capillaries throughout the body by red
blood cells (erythrocytes). Hemoglobin is the oxygen-carrying molecule within erythrocytes
responsible for binding both oxygen and carbon dioxide. At rest, humans consume approximately
5 percent of the available 21 percent of oxygen in the air. Exhaled air therefore contains about 16
percent oxygen. These percentages will vary somewhat by individual and level of activity, but they
provide a tangible example of oxygen utilization.
This fact has practical importance for rescue breathing, because our exhaled breath contains less
oxygen than normal air.
Advanced Concepts
During aerobic metabolism, our cells require oxygen to convert biochemical energy in the
form of nutrients (sugar, proteins and fatty acids) into the energy-storage molecule called
adenosine triphosphate (ATP). The production of ATP generates water, heat energy and
carbon dioxide.
In health care settings, blood oxygen levels are commonly measured with a pulse oximeter.
This device, which is often placed over the end of a finger, measures hemoglobin saturation
— the percent of hemoglobin binding sites occupied by oxygen — through a color shift
between oxygenated and deoxygenated blood states. Normal values while breathing air are
95-100 percent at low to moderate altitudes. Values below this warrant medical
attention. Hypoxemia (low levels of blood oxygenation) may necessitate prolonged
supplemental oxygen therapy to maintain values within normal levels.
The role of oxygen for diving injuries is to promote inert gas washout and enhance oxygen
delivery to compromised tissues. When providing supplemental oxygen to an injured
diver, a pulse oximeter is not used as a measure of oxygen treatment effectiveness or as an
assessment of inert gas washout.
Advanced Concepts
Advanced Concepts
Nitrogen (N2)
Nitrogen exists in different chemical forms. As a gas, nitrogen composes about 78 percent of the
Earth’s atmosphere and in this form is physiologically inert, meaning it is not involved in cellular
metabolism. In nondivers who remain at a constant ambient pressure, the concentration of
nitrogen in the exhaled air is also about 78 percent. In the case of divers who have been breathing
inert gas under pressure, the percentage of exhaled nitrogen would be expected to rise above
this level while offgassing. Because nitrogen is an inert gas, however, it does not interfere with
resuscitation efforts during rescue breathing.
Inert gas absorption (nitrogen and helium) is associated with decompression sickness (DCS).
DCS and the role of oxygen are discussed in the next chapter.
Advanced Concepts
Review Questions
Objectives
1. What is hypoxia?
2. Why is oxygen necessary for life?
3. Where does gas exchange occur in the body?
4. What body structures comprise the respiratory system?
5. What body structures are included in the cardiovascular system?
Oxygen (O2) is essential for life. Within minutes of experiencing severe oxygen deficiency (hypoxia)
or the absence of oxygen (anoxia), severe discomfort, unconsciousness or or death may occur.
Under normal circumstances, breathing ensures an adequate oxygen supply to tissues. The
respiratory system provides an effective interface between the bloodstream and the atmosphere
and facilitates gas exchange. Most critical to normal life is the intake of oxygen and removal of
carbon dioxide (CO2).
Carbon dioxide results from cellular metabolism and is transported by blood to the lungs, where
gas exchange across the alveolar-capillary membrane enables elimination in the exhaled breath.
In normal respiration, elevated levels of carbon dioxide, not low levels of oxygen, provide the
primary respiratory stimulus. The rapid elevation of dissolved carbon dioxide during short periods
of breath-holding provides quick insight into the power of its influence.
Air is drawn into the mouth and nose and passes into the pharynx. The pharynx divides into two
distinct passages: the trachea and the esophagus. The opening to the trachea is protected from
food (solids and liquids) during swallowing by a flexible flap of tissue called the epiglottis. The
esophagus, located behind the trachea, is a conduit for food and fluids en route to the stomach.
In contrast to solids and fluids, air travels from the pharynx through the larynx (voice box) and into
the trachea. The trachea consists of a series of semicircular cartilaginous rings that prevent
collapse. The trachea passes down into the chest cavity and branches into the right and left
bronchi, which enter the right and left lungs, respectively. The bronchi progressively divide into
smaller and smaller tubes and finally into the alveoli. This branching pattern is commonly referred
to as the bronchial tree.
The alveoli, located at the end of the smallest branches of the respiratory tree, have extremely thin
walls and are surrounded by the pulmonary capillaries. The alveoli have been likened to tiny
balloons or clusters of grapes.
Advanced Concepts
Potential Space: The double-layered pleural membrane is made up of the parietal layer,
which lines the thoracic cavity, and the visceral layer, which coats the organs.
These two layers normally remain closely adherent due to a slightly negative pressure that
keeps them from separating. Because there isn’t a separation between these membranes,
this area is known as a potential space and becomes a true space only if the membranes
are injured or rupture.
A pneumothorax forms from the entry of air between these layers (intrapleural space) and
may form from escaped alveolar air subsequent to pulmonary barotrauma.
Large areas of collapsed alveoli are known as atelectasis and may evolve into a pneumonic focus
(pneumonia) if they become infected. This is one reason why follow-up medical care is critical in
nonfatal drowning. Appropriate intervention can reduce or prevent complications associated with
drowning.
The average adult alveolus has an estimated diameter of 200-300 micrometers and is only a cell
layer thick. Alveoli lie adjacent to capillaries that are also one cell layer thick, and this proximity
enables the rapid exchange of carbon dioxide and oxygen. The thin alveolarcapillary membrane
separates the content of the lung from the bloodstream. If this membrane tears or becomes
compromised due to trauma from a lung-overexpansion injury (pulmonary barotrauma), it may
enable gas to pass out of the alveoli and into the bloodstream. Gas entering the vascular system
can travel throughout the body as an air embolism. This topic is discussed in more detail later in
this chapter.
The Heart
The heart is a hollow muscular organ
situated in the thoracic cavity between the
lungs in a space called the mediastinum. A
thin connective tissue sac called the
pericardium surrounds it. The pericardium
— like the pleural linings of the lungs —
reduces friction between the heart and
surrounding structures.
Blood Vessels
Blood leaves the left ventricle via the
aorta, which then branches into smaller
arteries to supply the head, arms, torso
and legs. The blood vessels make up the
vascular tree, with each branch heading to
progressively smaller branches, which give
rise to capillaries, the smallest of all blood
vessels. Through these thin capillary walls,
gases and nutrients are exchanged.
Functionally, the heart and large blood
vessels represent a pump-and-distribution
system for the capillaries, responsible for
supplying tissues with oxygen and nutrients
and removing carbon dioxide and other
metabolic waste products.
Fetal Circulation
Within the uterus, the fetus lives in a fluid-filled environment. As such, the lungs are not
used for gas exchange, and circulating blood is largely shunted away from pulmonary
tissue. In the fetus, gas exchange takes place in the placenta, drawing available oxygen
from the mother’s blood.
(Continued on the next page.)
The ductus arteriosus (a duct between two arteries) enables blood coming from the right
ventricle to directly enter the aorta and thus bypass the lungs. Once this passage closes,
blood is transported to the lungs, which are now needed for blood oxygenation. A vestige
(remnant) of the ductus will remain as a ligament bonding the aorta and the pulmonary
artery (ligamentum arteriosum or arterial ligament).
The foramen ovale (an oval-shaped hole) is a passage between the atria that allows blood
to shunt from the right atrium to the left, thus bypassing the nonfunctional lungs. At birth,
when the pressures in the left atrium increase, this passage usually closes, leaving only a
depression in the wall, known as the fossa ovalis. Closure of the foramen is incomplete in
approximately 25-30 percent of the population, thus leaving a patent (open) foramen ovale
(PFO). The PFO is not physiologically relevant in many persons, but it may predispose a
small number of people to certain medical issues.
Advanced Concepts
Blood is a specialized fluid (actually a distinct organ system) that links the respiratory
system to the rest of the body. Approximately 55 percent of our circulating blood volume
is comprised of plasma, the visible fluid fraction of blood. While mostly water, plasma also
contains proteins, glucose, minerals, nutrients, waste products and dissolved gases. The
cellular constituents of blood include erythrocytes (red blood cells, or RBC), which
transport oxygen and carbon dioxide, and leukocytes (white blood cells, or WBC), which
play a critical role in infection control and inflammatory responses. The third constituent is
platelets, which are cell fragments responsible for initiating the clotting process.
Objectives
1. What are the most important initial actions in responding to diving accidents?
2. What is decompression illness (DCI)?
3. What is the primary cause of decompression sickness (DCS)?
4. What are the primary symptoms of DCS?
5. What is arterial gas embolism (AGE)?
6. What is the primary risk factor for AGE?
7. Why is it important to seek medical evaluation when DCI is suspected?
8. What are the most prevalent symptoms of DCI?
9. What are the typical onset times of DCS and AGE symptoms?
The term decompression illness (DCI) describes signs and symptoms arising either during or
subsequent to decompression, and it encompasses two different but potentially linked processes:
Note:
While the underlying cause of these two conditions may be different, the initial medical
management (first aid) is the same. The most important initial actions performed in diving
accidents are early recognition and the use of supplemental oxygen.
While the effects of bubbles have an impact on us on a systemic level, specific signs and
symptoms are thought to result from either bubble accumulation or its impact on specific areas.
Examples include joint pain, motor or sensory dysfunctions and skin rash.
The mild or ambiguous nature of some DCS symptoms may result in denial on the part of some
injured divers. The assessments and tools offered during this course may help with motivation for
providers as well as injured divers to pursue first aid care and follow-up treatment.
DCS is generally only life-threatening with extreme exposures. Early treatment with high
concentrations of oxygen (as close to 100 percent as possible) has been shown to speed
symptom resolution and optimize the impact of recompression therapy.4 Though symptom
resolution is a desired effect of oxygen first aid, it is important to emphasize that it should not be
considered a definitive treatment or arbitrarily stopped when symptoms resolve.
• Symptom onset occurs after surfacing or, in some extreme exposures, well into ascent.
• Factors contributing to bubble formation include the degree of supersaturation (the amount
of excess inert gas), rapid ascent and decreasing ambient pressure (such as when flying or
driving to altitude after diving).
• The development of DCS symptoms may differ substantially among individuals; symptoms
may be subtle or obvious.
AGE is the most severe result of pulmonary barotrauma and often presents suddenly either near
or at the surface.
Depending on the location of gas collection, signs and symptoms may include chest pain,
changes in voice pitch, difficulty breathing or swallowing, gas bubbles felt under the skin (typically
around upper thorax, neck and/or face) and cyanosis (bluish coloration of the lips).
Advanced Concepts
A separate but related concern is AGE that occurs secondary to venous bubbles
bypassing the pulmonary filter and entering the arterial system directly. The process
through which blood passes from the right side of the circulatory system to the left and
bypasses the pulmonary filter is called shunting — in this case, right-to-left shunting.
Shunting may occur through a physiologically relevant PFO or passage through the lungs
(transpulmonary shunt). Regardless of the method, problems can occur when bubbles
enter the arterial circulation. Bubbles may affect the central nervous system (CNS) and
cause acute neurological symptoms. Symptom onset in this scenario could develop after a
longer interval than the 10-15 minutes typically described in cases of AGE since the source
of the arterialized bubbles is from the venous system and not pulmonary barotrauma. It is
important to note that while bubbles in the systemic circulation are undesirable, their
presence does not automatically cause symptoms. Bubbles have been visualized in the left
heart following decompression in subjects who have not developed symptomatic DCI.
Injured divers may have one or more of the following signs and symptoms. This list is ranked in
order of presentation frequency based on decompression illness of 2,346 recreational diving
incidents reported to Divers Alert Network from 1998 to 2004.
0 20 40 60 80 100
Occurrence (% of patients)
Classification and frequency distribution of initial and eventual manifestations of decompression illness
in 2,346 recreational diving accidents reported to Divers Alert Network from 1998 to 2004
• Lymphatic DCS: Identified as an initial symptom in only 0.3 percent of cases, it deserves
mention because this symptom does not immediately resolve with successful recompression
treatment. It is often characterized by localized swelling affecting the trunk and shoulders.
• Bowel and bladder issues: Spinal cord DCS may injure the nerves responsible for bladder
and bowel control. Urinary catheterization is often indicated to relieve injury to the bladder.
• Cardiovascular issues: Hypotension and/or chest pain caused by bubbles within the
chambers of the heart or extravascular bubbles around the heart can be the result of pulmonary
barotrauma as well as a compression or tension pneumothorax.
The occurrence of DCS varies by population. Based on DAN data, the per-dive rate among
recreational divers is 0.01-0.019 percent; among scientific divers it’s 0.015 percent; for U.S. Navy
divers it’s 0.030 percent; and for commercial divers it’s 0.095 percent.5,6
Previously published per-dive DCS rates based on 135,000 dives by 9,000 recreational divers
were 0.03 percent. This rate was higher in those who performed deep cold-water wreck dives
versus the group aboard warm-water liveaboards. The incidence of DCS from warm-water
liveaboards was 2/10,000 (0.0002) and among cold-water wreck divers in the North Sea
28/10,000 (0.0028).7
In contrast to DCS, AGE will typically show a more dramatic array of neurological symptoms, most
of which will show up immediately upon surfacing or within 15 minutes of the time of injury. As one
might expect, sudden neurological injury that leads to unconsciousness may result in drowning.
In some cases the use of oxygen leads to symptom resolution, which may prompt the decision to
forego medical assessment. DAN recommends seeking prompt medical evaluation in all cases of
suspected DCI regardless of the response to oxygen first aid. For those tempted to avoid medical
assessment, be advised that symptoms may recur, and the risk of recurrence may be reduced
with hyperbaric treatment.
Recompression Therapy
An injured diver may feel better or experience reduced symptom severity after receiving
emergency oxygen. Despite symptom improvement, and in some cases resolution, divers
should still seek medical evaluation. The primary medical concern is that symptoms (especially
neurological symptoms) may recur when supplemental oxygen therapy is stopped. This is one of
the reasons DAN recommends transportation to the nearest medical facility for evaluation and not
necessarily to the nearest hyperbaric chamber.
Every dive injury is unique, and crucial medical decisions must be made individually by a physician
trained in dive medicine. The decision about where to treat an injured diver can be made only
after a thorough medical evaluation and appropriate consultation. DAN is always available to
provide information to emergency medical staff regarding diving injuries and the potential benefit of
hyperbaric treatment. DAN also provides evacuation assistance and care coordination with
Residual Symptoms
Residual symptoms following hyperbaric oxygen treatment are not uncommon, especially in
severe cases or when considerable delays (sometimes measured in days) in treatment initiation
have occurred.
Divers who experience persistent symptoms following hyperbaric oxygen therapy should
remain under the care of a hyperbaric physician until symptoms have resolved or further therapy
is deemed either unnecessary or unlikely to provide further benefit. A decision to return to diving
should be made in consultation with a physician knowledgeable in dive medicine.
5. It is important to seek medical evaluation 10. Returning to diving following DCI should be
when DCI is suspected because done in conjunction with a physician
a. symptom resolution does not mean DCI knowledgeable in dive medicine.
is no longer present a. True
b. symptoms may recur b. False
c. risk of recurrence may be reduced
by hyperbaric treatment
d. all of the above
Objectives
1. What are the benefits of providing a high concentration of oxygen to an injured diver?
2. How does establishing a gas gradient help the injured diver?
3. What is the primary goal of emergency oxygen for injured divers?
4. What critical factors affect the percentage of oxygen delivery when using a demand
valve?
5. What is the initial flow rate for constant-flow oxygen-delivery systems?
6. What is the priority for oxygen delivery in remote areas?
7. What are the concerns for oxygen toxicity when delivering emergency oxygen first aid?
8. What are the symptoms of nonfatal drowning?
9. What is the first responder’s role in a nonfatal drowning?
The most common diving injuries for which oxygen use is recommended are AGE and DCS. In the
case of AGE, bubbles may enter the arterial system following lung overexpansion and lung-tissue
rupture. In the case of DCS, problems arise when gas dissolved in body tissues during a dive
comes out of solution in the form of bubbles during or after decompression. Bubbles may cause
tissue disruption, compromise blood flow, trigger inflammatory responses and/or cause other
problems.
Though most cases of DCS are mild and do not pose an immediate risk to life, impaired circulation
or function in vital areas such as the brain and spinal cord can result in severe neurological
symptoms. These can range from mild tingling and pain to weakness, paralysis, difficulty
breathing, unconsciousness and even death.
The Emergency Oxygen for Scuba Diving Injuries course emphasizes the use of oxygen for diving
injuries and nonfatal drowning but does not address other indications for oxygen treatment.
Nonfatal Drowning
Nonfatal drowning refers to a situation in which someone almost died from being submerged
underwater and was unable to breathe. In the case of prolonged asphyxia (not breathing) or
reduced cardiac and lung function due to submersion, oxygen therapy may be crucial. While
nonfatal-drowning victims may quickly revive, lung complications are common and require medical
attention. In addition, fluid and electrolyte imbalances may develop with the potential for delayed
symptom onset.12
Symptoms of nonfatal drowning may include difficulty breathing, bluish discoloration of the lips,
abdominal distention, chest pain, confusion, coughing up pink frothy sputum, irritability and
unconsciousness. Individuals may also be anxious or cold and would benefit from removal of wet
clothes and possible treatment for hypothermia.11
As a first responder, your primary role is to monitor vital signs, provide supplemental oxygen and
transport to the nearest medical facility as soon as possible.
Note:
Keep yourself safe. Avoid in-water rescue unless trained and properly equipped.
There are two variables that affect delivered oxygen concentrations: mask fit and flow rate
(measured in liters per minute or lpm). In the case of demand valves with oral resuscitation masks
(discussed in Chapter 16: Oxygen Delivery Systems and Components), proper fit and seal are
critical because the flow rate is not adjusted. When using constant-flow systems, mask fit is still
crucial because leaks result in decreased inspired fractions of oxygen (FiO2). Enhanced flow rates
are an inefficient way to compensate for a poor-fitting mask.
* May vary with respiratory rate **Less variation with changes in respiratory rate
+Delivery fractions vary with the equipment and techniques used. This table summarizes various oxygen-delivery systems and
potential values of inspired oxygen with their use.
Nasal cannulae are generally operated at relatively low flow rates of 2-4 lpm. Nasal cannulae are
the least-efficient method of oxygen delivery, typically delivering fractions no greater than 0.3 (30
percent). Simple face masks may deliver fractions of 0.5-0.6 at flow rates between 10-15 lpm.
Nonrebreather masks can deliver a higher fraction but probably still no greater than 0.8. Demand
valves are appropriate for conscious and spontaneously breathing divers and with careful mask
management may deliver fractions up to 0.9-0.95.
Accidents frequently occur in remote locations or far away from medical services, and oxygen
supplies are generally limited. Rescuers face the dilemma between maximizing inspired fractions
and limiting flow rates in an attempt to conserve oxygen supplies. The priority should always be to
maintain the highest inspired fractions possible.
As shown in the above table, the best solution is the demand valve (or manually triggered
ventilator used as a demand valve). If continuous-flow delivery is required or the only method
available, start at 10-15 lpm and increase or decrease in increments based on the needs of the
diver, ensuring that the reservoir bag remains full.
Flow rates above 10 lpm will not cause harm but will deplete oxygen supplies more quickly. If the
next level of care is accessible before the supply is exhausted, higher flow rates can be used to
maintain optimal oxygen fractions and enhance the injured diver’s comfort. Any perceived or
suspected worsening in a diver’s condition should prompt reassessment.
Breathing high concentrations of oxygen for prolonged periods at the surface can cause
pulmonary oxygen toxicity, which is quite distinct from CNS toxicity. In this setting, lung tissue may
become irritated when breathing elevated oxygen concentrations. The underlying mechanism for
this is the production of oxygen free radicals in a quantity that overwhelms our cellular antioxidant
defenses. Initial symptoms may include substernal (behind the sternum) irritation, burning
sensation with inspiration, and coughing.
The most severe symptoms may occur after about 12 to 16 hours of exposure at 1 ATA.13 The
time to initial symptom onset is expected to decrease at higher partial pressures (greater than 1
ATA). Symptoms may be seen from 8 to 14 hours at 1.5 ATA14 and from 3 to 6 hours at 2 ATA.13,14
At higher pressures, symptoms may occur more quickly but are often less severe due to limited
exposure times. The prevailing concern with oxygen partial pressure levels greater than 2.5 ATA is
CNS toxicity.12,14,15
CNS toxicity is not a concern for the oxygen provider rendering first aid. Pulmonary oxygen
toxicity is also not a significant concern for first responders delivering oxygen at maximal
concentrations on land or at sea level for less than 12-24 hours.
Advanced Concepts
Chemical oxygen systems deliver neither sufficient flow rates nor sufficient oxygen volume
to be effective. The average measured flow rates were 3 lpm (Pollock and Hobbs, 2002)
and less than 2 lpm (Pollock and Natoli, 2010) with total flow durations of little more than
15 minutes for one reactant set.
1. The primary goal of delivering the highest 6. The initial flow rate for constant-flow
concentration of oxygen possible to an oxygen delivery is
injured diver is to facilitate inert gas washout a. 2-4 lpm
and improve oxygen delivery to b. 10-15 lpm
compromised tissues. c. 20-25 lpm
a. True d. the rate the injured diver will tolerate
b. False
7. The percentage of oxygen delivered when
2. Providing a high concentration of oxygen to using a demand valve is influenced by
an injured diver may provide these benefits: a. flow rate
a. accelerate inert gas elimination b. mask fit
b. reduce bubble size c. mask seal
c. enhance oxygen delivery to tissues d. both b and c
d. reduce swelling
e. all of the above 8. In remote areas, the priority in oxygen
delivery is
3. Symptoms of nonfatal drowning may include a. to conserve oxygen supplies
a. difficulty breathing b. to maximize the highest inspired fraction
b. abdominal distension of oxygen
c. chest pain c. limit the flow of oxygen
d. hyperthermia
e. all but d 9. Oxygen toxicity, whether CNS or pulmonary,
is not a concern for oxygen first aid
4. In the event of an unresponsive drowning administered to an injured diver.
victim requiring CPR, begin with a. True
ventilations and follow the ABC protocols b. False
of CPR.
a. True
b. False
Objectives
1. What is the fire triangle, and how is oxygen involved?
2. What safety precautions should be implemented when handling and using oxygen
equipment?
3. What grade of oxygen should be used for diving first aid?
4. What documentation is required to receive an oxygen fill?
5. How should an oxygen unit be stored?
6. When should an oxygen unit’s components and cylinder pressure be checked?
7. When and how should reusable oxygen masks and removable plastic oxygen system
parts be cleaned?
Oxygen is not flammable, but all substances need oxygen to burn and
may burn violently in an environment of pure oxygen. The higher the
oxygen concentration, the greater the potential fire risk and
acceleration (CGA P45 section 4.1 2018). However, problems
associated with the use of properly maintained emergency-
oxygen devices are rare. Three elements — heat, fuel and
oxygen — are required for a fire to exist. This is commonly
called the fire triangle. Emergency oxygen systems will
always have at least one element: oxygen.
There are many grades of oxygen, but the three primary ones that oxygen providers need to
consider are
• Aviator-grade oxygen
• Medical-grade oxygen
• Industrial-grade oxygen
Each grade must be 99.5 percent pure oxygen; however, differences exist in how the cylinders are
filled, affecting the overall purity of the oxygen. For example, to prevent freezing at high altitudes,
aviator-grade oxygen has a lower moisture content than medical-grade oxygen.
The filling procedures for medical-grade oxygen require that an odor test be conducted and the
cylinder contents be evacuated before the fill. When odors are detected or damage to the valve
or cylinder is observed, medical-grade oxygen cylinders are either retired or cleaned before being
returned to use.
Industrial-grade oxygen is not recommended for use with dive injuries. Industrial-grade oxygen
guidelines allow for a certain percentage of impurities and other gases to be contained within the
cylinder. While both aviator- and medical-grade oxygen are suitable for breathing, industrial-grade
oxygen may not be. The procedures for filling industrial oxygen cylinders do not ensure that the
oxygen is free of contamination.
Another less common method is use of a prospective prescription, which allows a trained
individual to acquire oxygen for use in a diving injury. A physician trained in dive medicine may be
willing to provide this prescription.
Some countries, states and local governments have regulations that require that oxygen supply
companies document all medical-grade oxygen distillation, cylinder transfills and sales. These
governmental agencies routinely inspect the facility’s operations and documentation to verify
compliance with these regulations. Other areas have few or no regulations regarding the
distribution of oxygen.
Review Questions
1. Oxygen is one element of the fire triangle. 4. Methods for obtaining oxygen fills may
a. True include
b. False a. prescription
b. documentation of training in oxygen
2. Safety precautions to implement when delivery
using oxygen cylinders include c. prospective prescription
a. not allowing any oil or grease to come d. any of the above
in contact with oxygen cylinder
b. not exposing oxygen cylinders to high 5. When should an oxygen unit’s components
temperatures or allow smoking/open and cylinder pressure be checked?
flames around oxygen a. every two years
c. providing adequate ventilation when b. before every outing
using oxygen c. every week
d. using only equipment made for use d. annually
with oxygen
e. all of the above 6. An oxygen unit should be stored
a. with the valve closed
3. With what grade of oxygen should an b. in its protective case
oxygen cylinder for diving first aid be filled? c. assembled
a. aviator or industrial grade d. all of the above
b. medical grade only
c. medical or industrial grade 7. It is not necessary to clean oxygen parts
d. aviator or medical grade and masks.
a. True
b. False
Objectives
1. What are the components of an oxygen delivery system?
2. What are the hydrostatic testing requirements for an oxygen cylinder?
3 What two factors influence what cylinder size is appropriate?
4. When should the oxygen provider switch to a full cylinder?
5. Which oxygen regulator is preferred for diving first aid?
6. How often and by whom should an oxygen regulator be serviced?
7. Why is a demand valve the first choice for delivering oxygen to an injured diver?
8. What are the advantages and disadvantages of the following?
a) Manually triggered ventilator b) Bag valve mask
Any concerns by you or the fill station about the condition of the cylinder between hydrostatic
testing dates should prompt additional testing or inspections before filling the cylinder.
Capacity is the primary concern when choosing a cylinder. Enough oxygen should be available to
allow for continuous delivery to an injured diver from the time of injury at the farthest possible dive
site to the next level of emergency response (the nearest appropriate medical facility or point of
contact with EMS).
The duration of common portable oxygen cylinders varies based on the size of the oxygen
cylinder as well as oxygen flow, consumption rate and the type of delivery device. Common single
portable oxygen cylinders can last from 15 minutes to 60 minutes. Nonportable oxygen cylinders
can last up to eight hours or more. DAN Oxygen Units come with either an M9 (248 liters) or a
Jumbo-D (636 liters) oxygen cylinder.
A 15-minute oxygen supply may be all that is needed if diving from shore where EMS is available
and can respond quickly. A one- or two-hour supply may be required when diving from a
boat offshore. When diving farther offshore and assistance is hours away, consider carrying a
nonportable oxygen cylinder or multiple portable oxygen cylinders. Consult your Emergency
Oxygen Instructor about which cylinder size is most appropriate for your use.
The delivery device affects the duration of the oxygen supply. When using a constantflow
regulator (discussed later), the approximate duration of an oxygen cylinder can be determined
using this formula:
Capacity in liters ÷ flow in liters per minute = approximate delivery time
For example, if a cylinder holds 640 liters and the oxygen flow rate is 15 liters per minute, the
cylinder will last approximately 43 minutes. At 10 liters per minute, the same cylinder will last 64
minutes.
When a diver uses a demand inhalator valve (discussed later), it is more difficult to determine
an exact time of supply. The rate at which the oxygen is used will depend on the injured diver’s
breathing rate and volume. Generally, the average oxygen use on a demand valve is equivalent to
8 to 10 liters per minute. Demand-style delivery is preferred because no oxygen is wasted, and
usually the oxygen supply lasts longer.
A partially filled oxygen cylinder should be changed to a full one when the pressure drops
below 200 psi (14 bar). If only one cylinder is available, however, it should be used until the
oxygen supply is depleted.
Ask your Emergency Oxygen Instructor which connection systems for oxygen cylinders and
regulators are used in your region.
Oxygen delivery occurs via three common types of regulators regardless of how the regulator is
attached to the cylinder valve.
1. A constant-flow regulator can deliver a fixed or adjustable flow of oxygen.
2. A demand regulator functions like a scuba regulator and delivers oxygen when the demand
valve is activated.
3. A multifunction regulator combines the features of both the demand and constantflow
regulators.
A multifunction regulator is preferred over the other styles because it will allow a rescuer to provide
as close to 100 percent oxygen as possible to two injured divers simultaneously and permits
various mask options.
Regardless of the type of oxygen regulator used, it should be serviced every two years by a
factory-authorized service representative.
Oxygen system adapters are available commercially. To minimize the risk of fire and explosion,
they should be oxygen cleaned. Avoid homemade adapters and the use of scuba regulators with
high oxygen concentrations. It should be noted, however, that the CGA discourages use of
adapters.
Demand valve
DAN Oxygen Units contain a demand
inhalator valve (similar to a scuba regulator
second stage). When an injured diver begins
breathing through the mask and a proper seal
between the mask and the injured diver’s face
is maintained, the injured diver will receive the
highest oxygen concentration possible. With
the demand inhalator valve, oxygen flows only
when the injured diver inhales, and the
available oxygen supply will often last much
longer than with a constant-flow system. You
may use either an oronasal mask or an
oronasal resuscitation mask to fit the demand
valve to the injured diver’s face.
A nonrebreather mask is recommended for the breathing injured diver who does not tolerate the
demand inhalator valve or when multiple diving injuries require oxygen. An initial flow rate of 10-15
lpm is suggested when using the nonrebreather mask. Adjust the flow rate to the nonrebreather
mask so that the reservoir bag does not completely deflate during inhalations. If the reservoir bag
is continually deflated, check the seal of the mask, and adjust the flow rate accordingly, or switch
to a demand valve.
With a good fit and proper technique, the nonrebreather mask may deliver inspired oxygen
concentrations up to 80 percent.
Several other oxygen delivery devices, such as the partial rebreather mask, (missing one or
more one-way valves reducing percentage of oxygen delivery) the simple face mask and the
nasal cannula, are available and used in other settings. These devices do not deliver sufficient
percentages of oxygen and are not discussed in this course.
Current BVMs incorporate a tube connection for oxygen and a reserve bag that is usually
connected to the base of the resuscitation bag. Oxygen passes into both of them each time the
bag is compressed.
The bag and the mask are available in sizes suitable for adults, children and infants. Most adult
self-inflating bags have a volume of 1600 mL. A system for an adult should never be used on a
child because the bag can over expand a child’s lungs. Some systems include a mechanism for
preventing lung overexpansion.
The mechanics of the BVM make it a two-person skill. Many studies have clearly shown that, in
general, the technique as applied by a single rescuer produces very poor ventilations, even though
the rescuer may be well trained and conduct it perfectly. Therefore, it is recommended that the
BVM be used by a minimum of two trained rescuers to guarantee the optimal ventilation. One
rescuer manages the airway and keeps the mask sealed well, and the other compresses the
bag. BVMs are a good choice when two rescuers are available because it is less fatiguing than
providing ventilations.
Note:
Achieving a good seal while lifting the diver’s jaw with one hand and using the other to
compress the ventilation bag is very difficult for a single rescuer. The injured diver’s mouth
may remain closed beneath the mask or the tongue may create an obstruction due to poor
airway management. Leaks are difficult to prevent when attempted by a single rescuer.
Potential leaks are minimized with two rescuer delivery. On the other hand, if a good seal
is obtained on the injured diver’s face, the BVM can produce enough pressure to expand
the stomach and/or damage the lungs — hence the earlier recommendation to limit tidal
volume to 400-600 ml.
Tolerance valve. Depending on the manufacturer, this assembly contains two one-way valves.
The first is the “lip valve,” which opens when the gas exits from the ventilation bag and closes
when the gas goes in the opposite direction. This allows the gas contained in the ventilation bag
to be directed toward the injured diver and prevents the expired gas from reentering the bag. The
expired gas is directed from the assembly through a separate membrane or through the lip valve,
which rises to allow the gas to be dispersed. This membrane also prevents the air from returning
to the injured diver.
It can also function as a demand valve that can deliver maximum oxygen concentrations to the
breathing diver and minimize the gas waste.
Manually triggered ventilators offer several advantages. They deliver higher concentrations of
oxygen than manual ventilations with supplemental oxygen and are less tiring for the rescuers
delivering care. Manually triggered ventilators can deliver a flow greater than 40 lpm to a
nonbreathing or inadequately breathing injured diver, an amount that is significantly more than
what is required to satisfy the breathing requirements of an individual. Some older versions of
oxygen-powered ventilators even exceeded 160 lpm (normal inspiratory flow is 60-120 lpm) in
delivered oxygen. Previously it was thought that this amount was necessary to ventilate an injured
diver. However, such a high flow rate can easily cause distension of the stomach, which can
lead to regurgitation and the aspiration of stomach contents (which normally occurs when the
esophagus pressure is greater than 15-20 cm H2O). (normal esophageal pressure is 5-10 cm
H2O). In addition, a high flow rate can potentially damage the lungs, plus older models did not
allow for pressure release, possibly impeding exhalation.
The MTV-100, the model of manually triggered ventilators DAN uses as an option in its oxygen
units, is designed to terminate either the flow or the pressure if excessive pressure is detected in
the airways. It automatically limits the flow rate to 40 lpm. This corresponds with American Heart
Association recommendations to use a lower flow rate to reduce complications. It terminates the
flow completely when it detects a mounting pressure of greater than approximately 60 cm H2O.
Additionally, a redundant valve was added for use in the event that the first one failed.
Finally, some devices can stop providing gas prematurely without alerting the operator. This can
happen when the lungs of the injured diver present resistance or when there is a poor response
from the lungs as can happen when ventilating an individual with asthma or an injured diver
who has experienced a submersion incident. If the device does not have an alarm mechanism,
the operator may not become aware of the resistance during resuscitation, leading to an airway
obstruction or an undetected overexpansion of the lungs. The MTV-100 has an audible click that
alerts the operator of excessive levels of pressure in the airways.
MTVs, as well as demand valves, require a supply of oxygen to function therefore they can no
longer be used when the oxygen supply is exhausted.
Rescue Pak
The Rescue Pak is an affordable and compact oxygen system, ideal for areas where emergency
medical services exist nearby or the distance to the nearest medical facility is short. It includes the
following:
• Brass multifunction regulator
• Demand valve with hose
• M9 oxygen cylinder (248 liters)
• Nonrebreather mask with 6-foot tubing
• Oronasal resuscitation mask
• Waterproof case
• Optional MTV-100 with hose
Other DAN Oxygen Unit options (as well as first aid kits) are available. Check the DAN store at
DAN.org/Store for additional configurations.
1. Which of the following is not part of an 7. Oxygen regulators are fitted with a pin
oxygen delivery system: indexing system to prevent use on other
a. oxygen cylinder cylinder valves that may not contain oxygen.
b. pressure-reducing regulator a. True
c. lubricants to facilitate assembly b. False
d. oxygen hose
e. face mask 8. A demand valve flows only when the injured
diver inhales, allowing the oxygen to last
2. What is the primary consideration when longer.
choosing an oxygen cylinder? a. True
a. capacity b. False
b. number of injured divers
c. cylinder markings 9. A bag valve mask
a. is a self-inflating bag with a mask that
3. A multifunction regulator is preferred in aids in providing ventilations
emergency oxygen for scuba diving injuries b. has a manual trigger that initiates
because it can provide emergency oxygen oxygen flow
to two injured divers at the same time. c. is best used by two rescuers working
a. True together
b. False d. a and c
5. Oxygen cylinders are subject to periodic 11. A constant flow mask that is recommended
hydrostatic testing. when a breathing injured diver cannot
a. True activate the demand inhalator valve or when
b. False there is more than one injured diver is a:
a. nonrebreather mask
6. Oxygen cylinder marking colors are b. oronasal resuscitation mask
standardized throughout the world to avoid c. bag valve mask
confusion.
a. True
b. False
Review answers are on Page 65.
Objectives
For the skills included in this course, the oxygen provider will be able to:
1. Oxygen equipment identification, disassembly and assembly
• Identify the component parts of the DAN Oxygen Unit
• Disassemble and reassemble with minimal assistance the DAN Oxygen Unit or
equivalent
2. S-A-F-E
• List the steps in performing a scene safety assessment
• Perform a scene safety assessment in a scenario
• Use appropriate first aid barrier devices in a scenario
• Demonstrate a caring attitude toward a simulated diver who has become ill or injured
3. Initial assessment with basic life support (review only)
• Establish responsiveness of a simulated injured/ill diver
• Demonstrate current sequence of providing care with proper ventilations and
compression rates
4. Demand inhalator valve
• Provide emergency oxygen to a responsive breathing injured diver using the demand
inhalator valve and oronasal mask
5. Nonrebreather mask
• Provide emergency oxygen to a simulated unresponsive, breathing injured diver
using the nonrebreather mask
• Discern when options for oxygen delivery are not working adequately, and switch
to another as appropriate
Being able to provide emergency oxygen to an injured diver is more than just knowing what to do,
it is being able to do it. The following skills are essential elements to oxygen delivery. Your EO2
Instructor will guide you through this skill development section.
I J
M
Objectives:
• Identify the component parts of the DAN Oxygen Unit.
• Disassemble and reassemble with minimal assistance the DAN Oxygen Unit or equivalent.
Follow these simple steps to assemble and disassemble the DAN Oxygen Unit.
• Ensure oxygen unit is depressurized.
• Open constant-flow control.
• Check pressure gauge.
• Remove multifunction regulator from the oxygen cylinder valve.
• Secure oxygen cylinder.
• Remove oxygen washer from multifunction regulator.
– Note: Washer is different from standard scuba O-ring.
• Remove oxygen hose from multifunction regulator.
• If the fitting is too tight, use handwheel/wrench to unscrew the hose.
• Remove oxygen hose from demand inhalator valve.
– Note: Both ends of the oxygen hose are identical.
• Unscrew the plastic mask adapter from the demand inhalator valve.
• Remove inhalation/exhalation assembly.
• To assemble, repeat steps in reverse.
– Note: Check valves; ensure oxygen does not flow from threaded ports.
Objectives:
• List the steps in performing a scene safety assessment.
• Perform a scene safety assessment in a scenario.
• Use appropriate first aid barrier devices in a scenario.
• Demonstrate a caring attitude toward a simulated diver who has become ill or injured.
Remember S-A-F-E
Objectives:
• Establish responsiveness of a simulated
injured/ill diver.
• Demonstrate current sequence of providing
care with proper ventilations and
compression rates.
Remember S-A-F-E.
Assess responsiveness.
• State your name, training and desire
to help.
• Ask permission to help.
• If unresponsive,
• Tap on the collarbone.
• Shout, “Are you OK?”
• If no response, call for help and activate
emergency medical services (EMS).
Assess breathing.
• While you assess responsiveness,
determine if the diver is breathing normally.
If they are unresponsive and not breathing
normally, initiate CPR, beginning with 30
compressions.
Objectives:
• Provide emergency oxygen to a responsive, breathing injured diver using the demand inhalator
valve and oronasal mask.
Remember S-A-F-E.
Objectives:
• Provide emergency oxygen to an unresponsive, breathing injured diver using the nonrebreather
mask.
• Discern when options for oxygen delivery are not working adequately, and switch to another as
appropriate.
Remember S-A-F-E.
Objectives:
• Provide emergency oxygen to a nonbreathing or inadequately breathing injured diver using the
bag valve mask.
Follow these steps to ventilate a nonbreathing or inadequately breathing injured diver using a BVM.
This skill requires two rescuers.
Remember S-A-F-E.
Rescuer One
The first rescuer begins single-rescuer CPR
as soon as possible and continues while
the second rescuer prepares the oxygen
equipment. When the oxygen equipment is
ready, Rescuer One ventilates the injured diver
by compressing the bag about one-third of
the bag volume.
• Bag compressions should be slow and
gentle, lasting about one second for
the ventilation phase. Allow the chest to
fall completely before beginning each new
ventilation.
• Watch the stomach for signs of distension to prevent regurgitation.
• Each ventilation should last about one second. Deliver two ventilations.
• Deliver chest compressions between ventilations if used as part of CPR.
Rescuer Two
The second rescuer prepares the oxygen equipment, while the first rescuer performs CPR. When
the equipment is ready, the second rescuer should do the following:
• Connect the BVM tubing to the constant
flow barb on the oxygen regulator.
• Turn on constant flow to initial setting of 15
lpm, and allow the reservoir bag to inflate.
• Seal the mask in place using the head-tilt
chin-lift method, pulling the diver’s jaw up
and into the mask.
• Maintain the airway.
• Monitor the oxygen supply.
• Activate your emergency action plan.
• Call EMS and DAN.
Objectives:
• Provide emergency oxygen to a nonbreathing or inadequately breathing injured diver using an
MTV and oronasal mask.
Follow these steps to ventilate a nonbreathing or inadequately breathing injured diver using an
MTV. Two rescuers are required for this skill.
Remember S-A-F-E.
Rescuer One
The first rescuer begins single-rescuer CPR using an oronasal resuscitation mask as soon as
possible and continues while the second rescuer prepares the oxygen equipment. When the
oxygen equipment is ready, Rescuer One ventilates the injured diver by pressing the resuscitation
button carefully while observing the chest, releasing the button quickly.
• Watch for the chest and abdomen to rise.
– Ventilations should take about one second.
• Release the resuscitation button as soon as the
chest begins to rise. Deliver two ventilations.
– Leaving one hand gently on the center of the
chest can help to assess that ventilations are
adequate and not excessive.
• Watch for distension of the stomach.
• Deliver chest compressions between ventilations.
Rescuer Two
When the equipment is ready, the second rescuer
should do the following:
• Test the safety valve to ensure that it functions properly.
• Press the ventilation button, then block the oxygen outlet of the MTV with his or her hand. The
oxygen flow should stop, and the gas should be released.
NOTE: If the safety shutoff does not work, do not use the MTV.
• Connect the oronasal mask to the MTV adapter.
• Position the mask over the mouth and nose of the injured diver.
• Seal the mask in place using the head-tilt chin-lift method, pulling the diver’s jaw up and into the
mask.
• Maintain the airway, and hold the mask in place, while the first rescuer pushes the ventilation
button on the MTV and delivers chest compressions.
• Monitor the supply of oxygen attentively, and be prepared to resume mouth to mask ventilations
if the supply is exhausted.
• Activate your emergency action plan.
• Call EMS and DAN.
Objectives:
• List the components of an emergency assistance plan.
• Develop an emergency assistance plan for the local diving area.
The following information is critical in managing scuba diving injuries and illnesses.
Diver information
Name: Age:
DAN Member #
Address:
Phone:
Diving medical consultation information
Divers Alert Network (DAN): +1 (919) 684-9111*
*This number may be called collect in an emergency.
Other important information:
Phone:
Scuba diving is a safe and enjoyable sport, but on rare occasions injuries do happen. Providing
oxygen is the primary first aid action for scuba diving injuries when they occur.
Recognizing and responding to dive-related injuries is the first aid provider’s role. There are no
medical contraindications for providing emergency oxygen to an injured scuba diver, so always
provide the highest-possible concentration of oxygen for as long as possible or until a higher level
of medical care is available.
Remember, an injured diver’s condition can change rapidly, so never leave him or her alone or
unattended except to call for assistance. Maintain both your CPR and Oxygen Provider skills
to ensure you are prepared to handle an emergency should one occur. In the unlikely event a
diver becomes injured or shows signs of decompression illness, initiate emergency oxygen care,
activate emergency medical services and/or transport him or her to the nearest medical facility.
Contact DAN at +1 (919) 684-9111 after activating local EMS.
• Treat the injured diver and his or her family and friends with respect.
• Act in a decisive manner, and perform to the best of your abilities according to your knowledge
and skill level.
Chapter 5, Page 34
1. a
2. e
3. e
4. a
5. d
6. b
7. d
8. b
9. a
alveoli — microscopic air sacs in the lungs where gas exchange with the circulatory system
occurs
aorta — the largest artery in the circulatory system, from which the main arteries carrying
oxygenated blood branch out and subdivide into smaller and smaller vessels arterial gas
embolism (AGE) — gas bubbles in the arterial system generally caused by air passing through the
walls of the alveoli into the bloodstream
arterial gas embolism (AGE) — gas bubbles in the arterial system generally caused by air
passing through the walls of the alveoli into the bloodstream
atrium — chamber of the heart that provides access to another chamber called the ventricle
bronchiole — small branch of the bronchus that carries air to and from the alveoli
capillary — microscopic blood vessels where the gas exchange takes place between the
bloodstream and the tissues or the air in the lungs
carbon dioxide (CO2) — a waste gas produced by the metabolism of oxygen in the body
carbon monoxide (CO) — a highly poisonous, odorless, tasteless and colorless gas formed
when carbon material burns with restricted access to oxygen. It is toxic by inhalation since it
competes with oxygen in binding with the hemoglobin, thereby resulting in diminished availability
of oxygen in tissues.
cilia — long, slender microscopic hairs extending from cells and capable of rhythmic motion
decompression illness (DCI) — dysbaric injuries related to scuba diving; DCI includes both
decompression sickness (DCS) and arterial gas embolism (AGE).
decompression sickness (DCS) — a syndrome caused by bubbles of inert gas forming in the
tissues and bloodstream that can evolve from ascending too rapidly from compressedgas diving
Diameter Index Safety System (DISS) — intermediate pressure port where a hose attaches,
leading to demand valve or other apparatus
epiglottis — thin structure behind the tongue that shields the entrance of the larynx during
swallowing, preventing the aspiration of debris into the trachea and lungs
erythropoietin — a hormone that is synthesized mainly in the kidneys and stimulates red blood
cell formation
esophagus — portion of the digestive tract that lies between the back of the throat and stomach
fossa ovalis — oval depression in the wall of the heart remaining when the foramen ovale closes
at birth (See patent foramen ovale.)
intercostal muscles — the muscles between the ribs that contract during inspiration to increase
the volume of the chest cavity
larynx — the organ of voice production, also known as the voice box; the opening from the back
of the throat into the trachea (windpipe)
mediastinum — the space within the chest located between the lungs, containing the heart,
major blood vessels, trachea and esophagus
oxygen (O2) — a colorless, odorless, tasteless gas essential to life, making up approximately 21
percent of air
patent foramen ovale — a hole in the septum (wall) between the right and left atria of the heart
pericardium — a double-layered membranous sac surrounding the heart and major blood
vessels connected to it
pharynx — portion of the airway at the back of the throat, connecting mouth, nasal cavity and
larynx
platelet — a round or oval disk found in the blood of vertebrate animals that is involved with
blood clotting
pleura — membranes surrounding the outer surface of the lungs and the inner surface of the
chest wall and the diaphragm
prescription — a written order for dispensing drugs signed by a physician primary assessment
— assessment of the airway, breathing and circulation (pulse) in an ill or injured person; also
known as the ABCs
psi — pounds per square inch; a measurement of pressure respiratory arrest — cessation of
breathing
surfactant — a substance produced in the lungs to reduce surface tension in alveoli and
small airways
thorax — the upper part of the trunk (main part of the body) between the neck and the abdomen
that contains the heart, lungs, trachea and bronchi
trachea — the air passage that begins at the larynx and ends as the beginning of the principal
right and left bronchi
Valsalva maneuver — the forced inflation of the middle ear by exhaling with the mouth closed
and the nostrils pinched
venous gas emboli — inert gas bubbles in venous blood (that return to the heart and lungs)
ventilation — the exchange of gases between a living organism and its environment; the act of
breathing
ventricle — thick-walled, muscular chamber in the heart that receives blood from the atrium,
pumping it through to the pulmonary or systemic circulation
1. Pollock NW, ed. Annual Diving Report, 2008 edition. Durham, NC: Divers Alert Network, 2008.
2. Vann RD, Butler FK, Mitchell SJ, Moon RE. Decompression illness. Lancet 2011; 377: 153-64.
3. Vann RD, Denoble, P, Uguccioni D, et al. The risk of decompression sickness (DCS) is
influenced by dive conditions. In Godfrey J, Shumway, S, eds. Diving for Science 2005.
Proceedings of the American Academy of Underwater Sciences 24th Annual Symposium. AAUS
2005: 171-77.
4. Comroe JH Jr, Dripps RD, Dumke PR, Deming M. Oxygen toxicity: the effect of inhalation of
high concentrations of oxygen for twenty-four hours on normal men at sea level and at a simulated
altitude of 18,000 feet. JAMA 1945; 128:710-717.
5. Clark JM, Lambertsen CJ, Gelfand R, et al. Effects of prolonged oxygen exposure at 1.5, 2.0, or
2.5 ATA on pulmonary function in men (Predictive Studies V). J Appl Physiol 1999; 86:243-259.
6. Clark JM, Jackson RM, Lambertsen CJ, et al. Pulmonary function in men after oxygen
breathing at 3.0 ATA for 3.5h. J Appl Physiol 1991; 71:878-885.
7. Mayo Clinic. What’s a normal resting heart rate? Available at: http://www.mayoclinic.com/health/
heart-rate/AN01906.
8. Longphre JM, Denoble PJ, Moon RE, Vann RD, Freiberger JJ. First aid normobaric oxygen for
the treatment of recreational diving injuries. Undersea Hyperb Med 2007; 34:43–9.
9. Richards DB, Knaut AL. Drowning. In Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen’s
Emergency Medicine: Concepts and Clinical Practice, 7th ed. Philadelphia, Pa: Mosby Elsevier;
2009:chap 143.
Additional Reading
Bove A, Davis J. Bove and Davis’ Diving Medicine, 4th ed. Philadelphia, PA: Saunders; 2004.
Brubakk A, Neuman T, eds. Bennett and Elliott’s Physiology and Medicine of Diving, 5th ed.
London: Saunders; 2003.
Neuman T, Thom S. Physiology and Medicine of Hyperbaric Oxygen Therapy. Philadelphia, PA:
Saunders/Elsevier; 2008.
Among the services DAN provides to the diving public is the DAN Emergency Hotline
(+1 (919) 684-9111). This hotline is available 24 hours a day, seven days a week for anyone who
suspects a diving injury, requires assistance or needs to activate DAN TravelAssist® (an exclusive
benefit of DAN membership). Callers are connected directly with a member of DAN’s Medical
Services department, who can facilitate medical consultation with dive medicine specialists and
coordinate evacuation to ensure appropriate care.
DAN’s non-emergency safety resources include the DAN Medical Information Line
(+1 (919) 684-2948), the online Health & Diving libary (DAN.org/Health-Medicine) and Alert Diver
magazine, as well as Smart Guides, safety quizzes, and more.
Membership dues and insurance purchases support DAN’s nonprofit efforts. DAN members
enjoy benefits such as access to the DAN Dive Accident Insurance program, medical evacuation
support, print copies of Alert Diver magazine, free online seminars and more.
Your participation in this DAN training course demonstrates your commitment to dive safety.
Continue your education and your commitment by supporting the industry’s only
organization dedicated solely to improving dive safety. Join DAN today.
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