Effects of Inspiratory Muscle Training Using An Electronic Device On Patients Undergoing Cardiac Surgery: A Randomized Controlled Trial
Effects of Inspiratory Muscle Training Using An Electronic Device On Patients Undergoing Cardiac Surgery: A Randomized Controlled Trial
Effects of Inspiratory Muscle Training Using An Electronic Device On Patients Undergoing Cardiac Surgery: A Randomized Controlled Trial
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ORIGINAL ARTICLE
Abstract
Background: Cardiac surgery causes pathophysiological changes that favor the occurrence of pulmonary and
functional complications.
Objective: To investigate the effects of inspiratory muscle training (IMT) with an electronic device on patients
undergoing cardiac surgery.
Methods: A randomized controlled trial was conducted with 30 adult patients undergoing elective cardiac surgery.
A control group (CG) received conventional physical therapy care, and an intervention group (IG) received IMT
using the POWERbreathe K5® electronic device. Two daily sessions of physical therapy were performed at the
intensive care unit and one daily session at the ward until the sixth postoperative day. The following variables were
measured preoperatively and on the sixth postoperative day, in both groups: inspiratory muscle strength, dynamic
inspiratory muscle strength, and peak inspiratory flow. Data distribution was evaluated by the Shapiro-Wilk test.
Analysis of variance was used, and the results were considered statistically significant when p < 0.05.
Results: Maximal inspiratory pressure (71.7 ± 17.1 cmH2O vs 63.3 ± 21.3 cmH2O; p = 0.11], S-index (52.61 ± 18.61 vs
51.08 ± 20.71), and peak inspiratory flow [(2.94 ± 1.09 vs 2.79 ± 1.26)] were maintained in the IG but had a significant
reduction in the CG.
Conclusion: IMT performed with an electronic device was effective at maintaining inspiratory muscle strength,
dynamic inspiratory muscle strength, and peak inspiratory flow when compared to conventional physical therapy.
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Keywords: Respiratory Tract Diseases/complications; Cardiac Surgery/complications; Breathing Exercises; Muscle
Strength; Physiotherapy; Rehabilitation.
DOI: https://doi.org/10.36660/ijcs.20190093 Manuscript received on May 26, 2019; reviewed on May 14, 2020; accepted on May 16, 2020.
Int J Cardiovasc Sci. 2020; [online].ahead print, PP.0-0 Fortes et al.
Original Article Inspiratory Muscle Training After Cardiac Surgery
Inspiratory muscle dynamics: was measured using the underwent 30 respiratory cycles using a MIP load of
POWERbreathe K5® electronic device (POWERbreathe 30% on the first postoperative day.18 A new evaluation
International Ltd., Warwickshire, England). Dynamic was performed to redefine the MIP load on the third
inspiratory muscle strength (S-index) and PIF were postoperative day.19
assessed according to Lee et al.6 and Minahan et al.16 The conventional physical therapy protocol for both
groups was provided as recommended by Mendes
Protocols and Borghi-Silva,20 with the following instructions:
adequate posture, deep inspiration, protection of the
Patients were randomized by a simple drawing, after
chest, stimulation of the return of functional activities,
CICU admission, and divided into a control group (CG),
encouragement to cough, pulmonary re-expansion
which received conventional physical therapy care,
techniques, diaphragmatic breathing, timed breathing
and an intervention group (IG), which received IMT in
exercises, active range-of-motion exercises involving the
addition to conventional care.
limbs, active-assistive or active range-of-motion exercises
Patients initiated IMT 6 hours after extubation, usually (depending on each patient’s condition) involving
on the first postoperative day. In the CICU, the patients the elbows, shoulders, hips, and knees, early removal
remained in semi-Fowler's position at 45º17 or, if possible, from the bed and from sedation, reduced ambulation
were placed on a chair with their feet flat on the floor (according to each patient's condition), and oxygen
and their back against the back of the chair for support therapy, when necessary.
(Figure 1). The seated position was also used in patients Inspiratory muscle strength, inspiratory muscle
who were hospitalized but not in the CICU.5 In both dynamics, and PIF were reassessed on the sixth
situations, patients were instructed to exhale calmly, postoperative day, and the data were compared. All
followed by a maximal forced inspiration to total lung patients received the same analgesia protocol with
capacity using a mouthpiece and a nasal clip as an aid intravenous morphine (2–5 mg every 4 hours).
to prevent air leaks.17 Interventions were performed by junior and
IMT was performed in two daily sessions during senior physiotherapists. However, baseline and
the patients' stay in the CICU. Other hospitalized outcome assessments were conducted by a blinded
patients performed only one daily session. The patients senior physiotherapist.
Figure 1 – Participant in semi-Fowler’s position undergoing an IMT session on the first postoperative day.
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Original Article Inspiratory Muscle Training After Cardiac Surgery
Statistical Analysis using Fisher's exact test. The results were considered
statistically significant when p < 0.05.
The collected data were analyzed using Stata/SE
software, version 12.1 (Statacorp, College Station, Texas,
Results
USA). The Shapiro-Wilk test was used to assess the
normality of the groups. Quantitative variables with The 30 patients included in the study had a mean age
normal distribution are presented as mean and standard of 59.2 ± 13.1 years and were divided into two groups,
deviation, while continuous variables with non-normal as shown in Figure 1. Other demographic and clinical
distribution are described as median and interquartile variables are detailed in Table 1. None of the analyzed
variables differed significantly between the two groups,
range. Their differences were determined using paired
indicating that the sample was homogeneous. There were
and unpaired Student's t-test and Mann-Whitney test. no significant differences in surgical data, mechanical
Categorical variables are presented as absolute numbers ventilation duration, length of CICU stay, and length of
and percentages, and their association was assessed hospital stay between the two groups (Table 2).
Excluded (n = 7)
• Death (n = 3)
• Mechanical ventilation > 24 horas (n = 2)
• Impossibility to reassess (n = 2)
Randomized (n = 30)
Gender 0.99a
Male 12 11
Female 3 4
Comorbidities
Hypertension 10 11 0.99a
Smoking 4 9 0.14a
Dyslipidemia 4 4 0.99a
AMI 3 7 0.15a
Ejection fraction
Reduced (< 40%) 2 2
0.99a
Mid-range (40-49%) 2 1
Preserved (> 50%) 11 12
InsCor
Low risk 12 9
0.21a
Medium risk 2 6
High risk 1 0
Surgery
CABG 9 8
0.99a
Valve 5 6
CABG + valve 1 1
BMI: body mass index; WHR: waist-hip ratio; AMI: acute myocardial infarction; InsCor: mortality risk in cardiac surgery; CABG: coronary artery
bypass grafting. aFisher’s exact test. bUnpaired Student’s t-test.
Table 2 - Surgical data, mechanical ventilation duration, and length of CICU and hospital stay, per group, in patients
undergoing cardiac surgery
Surgery time (minutes) 202 (184.5; 255) 210 (201.5; 269) 0.33a
MV: mechanical ventilation; CICU: cardiology intensive care unit. aMann-Whitney test. bUnpaired Student’s t-test.
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Original Article Inspiratory Muscle Training After Cardiac Surgery
MIP (cmH2O)
Preoperative 80.2 ± 33.7 71.7 ± 17.1
0.35
POD 6 56.5 ± 20.4 63.3 ± 21.3
0.53
p 0.007 0.11
MIP: maximal inspiratory pressure; POD: postoperative day. Data showed as mean ± standard deviation. Paired Student’s t-test (intragroup) and
unpaired Student’s t-test (intergroup).
S-index (cmH2O)
Preoperative 50.71 ± 24.34 52.61 ± 18.61
0.95
POD 6 34.51 ± 16.62 51.08 ± 20.71
0.04
p < 0.0001 0.79
PIF (L/s)
Preoperative 2.81 ± 1.40 2.94 ± 1.09
0.96
POD 6 1.86 ± 1.00 2.79 ± 1.26
0.03
p < 0.0001 0.69
POD: postoperative day; PIF: peak inspiratory flow. Data showed as mean ± standard deviation. Paired Student’s t-test (intragroup) and unpaired
Student’s t-test (intergroup).
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Inspiratory Muscle Training After Cardiac Surgery Original Article
Cordeiro et al.28 evaluated 50 patients divided into two PIF measure has been associated with respiratory
groups. One group underwent IMT using the Threshold® muscle strength.34 Nemopuceno et al.,17 when analyzing 10
device twice a day, with 3 sets of 10 repetitions, and the individuals who underwent IMT twice a day for a period of
other group received only conventional ICU care, both until 4 weeks after prolonged hospitalization, observed that these
hospital discharge. The authors observed that the Threshold® patients had increased PIF at the end of training. Weiner et
group maintained its MIP values when compared to the al.35 found that patients who underwent IMT presented a
other group. This is consistent with the results of this study, significant increase in MIP and PIF. These authors observed
in which training lasted only until the sixth day. that inspiratory muscle strength played an essential role
The literature has emphasized the importance of in the generation of PIF. However, no studies to date have
performing IMT in the preoperative period. Some provided reference ranges for this parameter.
systematic reviews and meta-analyses show that when
started in this period, IMT helps maintaining MIP, Study Limitations
reduces the risk of postoperative complications, and
decreases the length of hospital stay.8,22 In this study, To our knowledge, this is the first study to investigate
we investigated the effects of IMT only on inspiratory the effects of IMT on cardiac surgery patients using a
muscle strength. new electronic device until the 6th postoperative day.
However, there are limitations regarding the small
IMT can be performed with linear pressure resistors
number of patients and the number of training sessions
such as Threshold®, which has been on the market for
(only six). Most studies with IMT after cardiac surgery
a long time and has already shown its effectiveness for
perform training until hospital discharge. Another
gaining respiratory muscle strength. Recently, electronic
limitation of the present study was the non-reevaluation
load-adjusting devices such as the POWERbreathe
of inspiratory muscle strength (MIP and S-index) and PIF
K-series® (K1-K5) have been used. These devices adjust
on the day of discharge, so that there was a comparison
to the load imposed on respiratory muscles in proportion
with the sixth postoperative day values. For these
to the flow; the higher the flow, the greater the resistance,
reasons, further randomized controlled trials with larger
so the flow decreases the resistance, also providing
greater comfort to the patient.31,32 samples are needed to compare their results with those
of the present study.
In another study, Charususin et al. 33 used IMT
with POWERbreathe® associated with pulmonary
rehabilitation in patients with chronic obstructive Conclusion
pulmonary disease who had respiratory muscle
IMT performed with an electronic device was found to
weakness. At the end of the study, they observed
be effective at maintaining inspiratory muscle strength,
increased endurance and improved dyspnea sensation
dynamic inspiratory muscle strength, and PIF when
in the patients.
compared to conventional physical therapy.
The S-index can be measured using the POWERbreathe
K-series® and is used to assess dynamic inspiratory
muscle strength.29 While MIP is obtained by maximal Acknowlegments
static inspiratory effort, the S-index is measured during a The authors are thankful to physiotherapists of the
dynamic unobstructed inspiratory maneuver. Moreover, Cardiology Intensive Care Unit and Ward of Hospital
when MIP cannot be used to measure inspiratory muscle Universitário – Campus Presidente Dutra at the
strength, the S-index appears to be a reliable alternative Universidade Federal do Maranhão.
assessment.11 However, no studies to date have provided
reference ranges for this variable. Minahan et al. 11,29
reported that S-index values could not be compared to Author Contributions
MIP values obtained using respiratory pressure meters. Conception and design of the research: Fortes JVS.
In the present study, the group that received IMT Acquisition of data: Fortes JVS, Borges MGB, Marques
maintained their baseline S-index and PIF in the MJS, Oliveira RL, Rodrigues LR, Castro EM. Analysis
postoperative period; in the control group, these values and interpretation of the data: Borges MGB, Borges DL.
were lower in the postoperative period. This effect may Statistical analysis: Borges DL. Writing of the manuscript:
be due to IMT because clinical and surgical variables Fortes JVS. Critical revision of the manuscript for
were homogeneous in the study groups. intellectual content: Esquivel MS, Borges DL.
Int J Cardiovasc Sci. 2020; [online].ahead print, PP.0-0 Fortes et al.
Original Article Inspiratory Muscle Training After Cardiac Surgery
Potential Conflict of Interest Maria Jhany da Silva Marques, Rafaella Lima Oliveira,
No potential conflict of interest relevant to this article Liana da Rocha Rodrigues, Érica Miranda de Castro,
was reported. Mateus Souza Esquivel, Daniel Lago Borges.
Sources of Funding Ethics Approval and Consent to Participate
There were no external funding sources for this study. The study was approved by the Brazilian Registry of
Clinical Trials (REBEC) (identification no. RBR-8SWGC3)
Study Association and by the Research Ethics Committee at our institution
This study is part of the conclusion work of a (Consolidated Opinion no. 1.573.419), as recommended
multiprofessional residency in health by the authors: João by Brazilian National Board of Health (CNS) Resolution
Vyctor Silva Fortes, Mayara Gabrielle Barbosa Borges, no. 466/12.
References
1. Matheus GB, Dragosavac D, Trevisan P, Costa CE, Lopes MM, Riberio 14. American Thoracic Society/European Respiratory Society. ATS/ERS
GCA. Inspiratory muscle training improves tidal volume and vital statement on respiratory muscle testing. Am J Respir Crit Care Med.
capacity after CABG surgery. Rev Bras Cir Cardiovasc. 2012;27(3):362-9. 2002;166(4):518-624.
2. Cavenaghi S, Ferreira LL, Marino LHC, Lamari NM. Respiratory 15. Mejía OAV, Lisboa LAF, Puig LB, Moreira LFP, Dallan LAO, Pomerantzeff
physiotherapy in the pre and postoperative myocardial revascularization PMA, et al. InsCor: a simple and accurate method for risk assessment in
surgery. Rev Bras Cir Cardiovasc. 2011;26(3):455-61. heart surgery. Arq Bras Cardiol. 2013;100(3):246-54.
3. Chen P-C, Liaw MY, Wang LY, Tsai YC, Hsin YJ, Chen YC, et al. 16. Minahan C, Sheehan B, Doutreband R, Kirkwood T, Reeves D, Cross T.
Inspiratory muscle training in stroke patients with congestive heart Repeated-sprint cycling does not induce respiratory muscle fatigue in
failure: a CONSORT-compliant prospective randomized single-blind active adults: measurements from the powerbreathe inspiratory muscle
controlled trial. Medicine. 2016;95(37):e4856. trainer. J Sports Sci Med. 2015;14(1):233-8.
4. Charususin N, Gosselink R, Decramer M, McConnell A, Saey D, Maltais 17. Nemopuceno Júnior BRV, Oliveira PRB, Pires TQ, Martinez BP, Gomes
F, et al. Inspiratory muscle training protocol for patients with chronic Neto MG. Effect of inspiratory muscle training associated with physical
obstructive pulmonar disease (IMTCO study): a multicenter randomised rehabilitation after prolonged hospitalization: case series. Rev Pesq
controlled trial. BMJ Open. 2013;3(8):e003101. Fisioter. 2015;5(3):237-44.
5. Ferreira JB, Plentz RDM, Stein C, Casali KR, Arena R, Lago PD. 18. Souza LC, Campos JF, Daher LP, Silva PF, Ventura A, Prado PZ, et al.
Inspiratory muscle training reduces blood pressure and sympathetic Mechanical ventilation weaining in inclusion body myositis: feasibility
activity in hypertensive patients: a randomized controlled trial. Int J of isokinetic inspiratory muscle training as an adjunct therapy. Case Rep
Cardiol. 2013;166(1):61-7. Crit Care. 2014;2014:902541.
6. Lee KB, Kim MK, Jeong JR, Lee WH. Reability of an eletronic inspiratory 19. Borja RO, Campos TF, Oliveira KTS, Freitas DA, Mendonça KMPP.
loading device for assessing pulmonary function in post-stroke patients. Protocol for preoperative inspiratory muscle training in elective cardiac
Med Sci Monit. 2016 Jan 19;22:191-6. surgery: pilot study. ConScientiae Saude. 2012;11(2):265-73.
7. Valkenet K, Heer F, Backx FJG, Trappenburg JCA, Hulzebos EHJ, Kwant 20. Mendes RG; Borhi-Silva, A. Efficacy of physiotherapy intervention
S, et al. Effect of inspiratory muscle training before cardiac surgery in associated to intermittent positive pressure breathing after cardiac
routine care. Phys Ther. 2013;93(5):611-9. surgery with cardiopulmonary bypass. Fisioter Mov. 2006;19(4):73-82.
8. Gomes Neto M, Martinez BP, Reis HFC, Carvalho VO. Pre and 21. Hulzebos EH, Smit Y, Helders PPJM, Meeteren NLU. Preoperative
postoperative inspiratory muscle training in patients undergoing physical therapy for elective cardiac surgery patients. Cochrane Database
cardiac surgery: systematic review and meta-analysis. Clin Rehabil. Syst Rev. 2012 Nov 14;11:CD010118.
2017;31(4):454-64.
22. Katsura M, Kuriyama A, Takeshima T, Fukuhara S, Furukawa TA.
9. Kodric M, Trevisan R, Torregiani C, Cifaldi R, Longo C, Cantarutti F, et Preoperative inspiratory muscle training for postoperative pulmonary
al. Inspiratory muscle training for diaphragm dysfunction after cardiac complications in adults undergoing cardiac and major abdominal
surgery. J Thorac Cardiovasc Surg. 2013;145(3):819-23. surgery. Cochrane Database Syst Rev. 2015;5(10):CD010356.
10. Medeiros AIC, Fuzari HKB, Rattesa C, Brandão DC, Marinho PEM. 23. Ortiz LDN, Schaan CW, Leguisamo CP, Tremarin K, Mattos WLLD,
Inspiratory muscle training improves respiratory muscle strength, Kalil AK, et al. Incidence of pulmonary complications in myocardial
functional capacity and quality of life in patients with chronic kidney revascularization. Arq Bras Cardiol. 2010;95(4):441-7.
disease: a systematic review. J Physiother. 2017;63(2):76-83.
24. Ferreira PEG, Rodrigues AJ, Évora PRB. Effects of an inspiratory muscle
11. Langer D, Jacome C, Charusin N, Scheers H, McConnell A, Decramer rehabilitation program in the postoperative period of cardiac surgery.
M, et al. Measurement validity of an eletronic inspiratory loading device Arq Bras Cardiol. 2009;92(4):275-82.
during a loaded breathing task in patients with COPD. Respir Med.
2013;107(4):633-5. 25. Schnaider J, Karsten M, Carvalho T, Lima WC. Influence of preoperative
respiratory muscle strenght on clinical evolution after myocardial
12. Nemopuceno Júnior BRV; Gómez TB, Gomes Neto M. Use of revascularization surgery. Fisioter Pesqui. 2010;17(1):52-7.
powerbreathe in inspiratory muscle training for athletes: systematic
review. Fisioter Mov. 2016;29(4):821-30. 26. Kendall F, Olveira J, Peleteiro B, Pinho P, Bastos PT. Inspiratory muscle
training is effective to reduce postoperative pulmonary complications
13. McConnel A. Treinamento respiratório para um desempenho superior. and length of hospital stay: a systematic review and meta analysis. Disabil
Barueri: Manole; 2013. Rehabil. 2018;40(8):864-82.
Fortes et al. Int J Cardiovasc Sci. 2020; [online].ahead print, PP.0-0
Inspiratory Muscle Training After Cardiac Surgery Original Article
27. Savci S, Degirmenci B, Saglam M, Arikan H, Ince DI, Turan HN, et 31. Gosselink R, Vos JD, Heuvel SP, Segers J, Decramer M, Kwakkel G.
al. Short-term effcts of inspiratory mucle training in coronary artery Impact of inspiratory muscle training in patients with COPD: what is
bypass graft surgery: a randomized controlled trial. Scand Cardiovasc the evidence? Eur Respir J. 2011;37(2):416-25.
J. 2011;45(5):286-93.
32. Langer D, Charususin N, Jácome C, Hoffman M, McConnell A, Decramer
28. Cordeiro ALL, Melo TA, Neves D, Luna J, Esquivel MS, Guimarães ARF, M, et al. Efficacy of a novel method for inspiratory muscle training
et al. Inspiratory muscle training and functional capacity in patients in people with chronic obstructive pulmonary disease. Phys Ther.
undergoing cardiac surgery. Braz J Cardiovasc Surg. 2016;31(2):140-4. 2015;95(9):1264-73.
29. Silva PE, Carvalho KL, Frazão M, Maldaner V, Daniel CR, Gomes-Neto 33. Charususin N, Gosselink R, Decramer M, McConnell A, Saey D,
M. Assesment of maximum dynamic inspiratory pressure. Respir Care. Maltais F, et al. Inspiratory muscle training protocol for patients with
2018;63(10):1231-8. chronic obstructive pulmonary disease. (IMTCO study): a multicentre
randomised controlled trial. BMJ Open. 2013;3(8):e003101.
30. Hulzebos EH, Meeteren NLU, Buijs BJWM, Bie RA, Riviere AB,
Helders PJM. Feasibility of preoperative inspiratory muscle training in 34. Mahler DA. Peak inspiratory flow rate as a criterion for dry powder
patients undergoing coronary artery bypass surgery with a high risk of inhaler use in chronic obstructive pulmonary disease. Ann Am Thorac
postoperative pulmonary complications: a randomized controlled pilot Soc. 2017;14(7):1103-7.
study. Clin Rehabil. 2006;20(11):949-59.
35. Weiner P, Weiner M. Inspiratory muscle training may increase peak
inspiratory flow in chronic obstructive pulmonary disease. Respiration.
2006;73(2): 151-6.
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