Archives of Physical Medicine and Rehabilitation

journal homepage: www.archives-pmr.org

Archives of Physical Medicine and Rehabilitation 2021;102: 1457−64

ORIGINAL RESEARCH

Effectiveness of Continuous Chest Wall Vibration

With Concurrent Aerobic Training on Dyspnea and
Functional Exercise Capacity in Patients With
Chronic Obstructive Pulmonary Disease: A
Randomized Controlled Trial
Simone Pancera, MSc,a Riccardo Buraschi, PT,a Luca Nicola Cesare Bianchi, MD,a
Roberto Porta, MD,a Stefano Negrini, MD,b,c Chiara Arienti, PhDa
From the aIRCCS Fondazione Don Carlo Gnocchi, Milan; bDepartment of Biomedical, Surgical and Dental Sciences, University of Milan “La
Statale”, Milan; and cIRCCS Istituto Ortopedico Galeazzi, Milan, Italy.

Abstract
Objective: To investigate the effects of continuous chest wall vibration with concurrent aerobic training in addition to a 4-week pulmonary reha-
bilitation program on dyspnea and functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD).
Design: Randomized, single-blind, placebo-controlled trial.
Setting: The Cardiopulmonary Rehabilitation Unit of a tertiary referral subacute rehabilitation center.
Participants: A sample of 146 consecutive patients with COPD (Global Initiative for Chronic Obstructive Lung Disease II-III-IV) were assessed
for eligibility. The final sample of 40 patients (N=40) was randomized into 3 groups (intervention, sham intervention, control).
Interventions: All groups carried out 5 sessions per week for 4 weeks of standard pulmonary rehabilitation treatment. The 2 daily 30-minute ses-
sions included aerobic training and resistance training or airway clearance techniques. The intervention group performed the aerobic training with
the addition of continuous chest wall vibration applied during cycling, whereas the sham intervention group received continuous chest wall vibra-
tion as a placebo during cycling.
Main Outcome Measures: Six-minute walk distance (6MWD) and Barthel Index based on dyspnea (BID).
Results: A total of 36 participants completed the study (69§7 years; forced expiratory volume in 1 second percentage of predicted, 40.15%§
15.97%). Intention to treat analysis showed no significant differences between groups for 6MWD and BID. However, the increase in 6MWD was
a clinically important difference in the intervention group (42.57§43.87m, P=.003), with a moderate effect size (d=0.58).
Conclusions: Continuous chest wall vibration with concurrent aerobic training in addition to a standard pulmonary rehabilitation program might improve func-
tional exercise capacity compared with usual care, but there were no effects on dyspnea, respiratory muscle function, or quality of life in patients with COPD.
Archives of Physical Medicine and Rehabilitation 2021;102:1457−64
Ó 2021 by the American Congress of Rehabilitation Medicine

Chronic obstructive pulmonary disease (COPD) is a multisystemic of activities of daily living in the affected patients.1,2 Moreover,
disease characterized by a progressive worsening of lung function symptoms such as exertional dyspnea and early fatigability result
and extrapulmonary manifestations such as nutritional abnormali- in restricted participation and sedentary lifestyle in individuals
ties and skeletal muscle dysfunction, leading to severe limitation with COPD; however, these symptoms can be relieved with vari-
ous forms of exercise training during pulmonary rehabilitation pro-
Presented as an abstract to the European Respiratory Society (ERS), September 6−9, 2020,
grams.3 Among these exercise methods, little is known about the
virtual, in session “Respiratory viruses in the ‘pre COVID-19 era’ (Eur Respir J 2020;56[Suppl use of continuous chest wall vibration in individuals with COPD.
64]:1259). Vibratory devices have indeed been used in the rehabilitation set-
Clinical Trial Registration No.: NCT03644888.
Disclosures: none
tings for their role in muscle force enhancement,4 fatigue onset

0003-9993/$36 - see front matter Ó 2021 by the American Congress of Rehabilitation Medicine
https://doi.org/10.1016/j.apmr.2021.03.006
1458 S. Pancera et al

delay,5 and pain relief,6 and they were initially used during pulmo- Initiative for Chronic Obstructive Lung Disease stage II-III-IV),
nary rehabilitation programs as an airway clearance technique for defined as postbronchodilator forced expiratory volume in 1 sec-
chronic respiratory diseases.7 Only later was chest wall vibration ond (FEV1)/forced vital capacity (FVC)<0.7 and FEV1<80% pre-
used for ventilatory muscle stimulation and dyspnea reduction. For dicted,1 were identified through a hospitalization list and assessed
example, previous studies reporting specific applications of chest for eligibility, from September 2018-October 2019. Exclusion cri-
wall vibration on healthy participants hypothesized that vibration teria include (1) restrictive lung disease, unstable conditions,
could have a facilitating action on the inspiratory muscles, improv- recent exacerbation, infection, embolism, pneumothorax, thoracic
ing the respiratory drive and resulting in a decreased sensation of or abdominal surgery (<3mo before recruitment); (2) cardiologic
dyspnea and sense of effort associated with inspiration.8,9 conditions such as myocardial infarction (<6mo before recruit-
Three systematic reviews on airway clearance techniques ment), heart failure, or severe angina; and (3) inability to perform
included vibration among the various methods adopted.10-12 In a the cycle ergometer training (eg, orthopedic or urogenital condi-
review by Ides et al,10 only 1 study reported a significant reduction tions) or to understand the instructions required to carry out the
in dyspnea sensation due to “in-phase vibration” use,13 which tests.
means that mechanical vibration was given to the chest wall dur-
ing inspiration. However, conflicting results have emerged regard- Procedure
ing the use of chest wall vibration in the clinical setting and
during standard rehabilitation treatments for patients with A block randomization scheme was generated (www.randomiza
COPD.14 Moreover, it is still debated which application modes, tion.com) by a blinded external investigator before the start of the
frequencies, and stimulation volumes are most effective in the study. On the first day of hospitalization, demographic and clinical
application of chest wall vibration.13 characteristics of eligible patients were collected by a second
In our opinion, the combined effects of vibration, that is, neuro- investigator who, by opening sealed envelopes, randomly allo-
muscular facilitation and reduction of breathlessness, might allow cated participants into 1 of 3 different groups: vibration interven-
patients with COPD to train at higher intensities during aerobic train- tion protocol, vibration sham intervention protocol, or control
ing, especially for those participants who interrupt exercise or cannot group (CG). The second investigator was not blinded to the inter-
increase workload because of the early onset of dyspnea rather than ventions because it was not possible, but the primary objective
fatigue of the lower limb muscles. Therefore, the primary objective of outcome measurements were not likely to be influenced by lack of
this study was to investigate the effect of continuous chest wall vibra- blinding.15 Starting from the second day of hospitalization (day
tion with concurrent aerobic training in addition to a 4-week pulmo- 1=T0), participants were assessed for baseline measurements,
nary rehabilitation program on dyspnea and functional exercise which were repeated at the end of the study protocol (day 22=T1)
capacity in patients with COPD. The secondary objective of the study by the same investigator. Spirometry was not repeated at T1
was to evaluate the effect of continuous chest wall vibration on respi- because we assumed to see no change in pulmonary function
ratory muscle strength and quality of life in patients with COPD. results after treatment.
Patients underwent a total of 20 treatment days (4 weeks),
divided into 2 sessions per day for 5 sessions per week. Each ses-
sion lasted 30 minutes and included aerobic training in 1 session
Methods and resistance training or airway clearance techniques in the other
(supplemental appendix S1 for the detailed training procedure,
The protocol for this prospective, single-blind, randomized con-
available online only at http://www.archives-pmr.org/). Aerobic
trolled clinical trial was approved by the local Ethics Committee
training sessions and additional sessions were done in random
and complies with the Declaration of Helsinki. The study was reg-
order within the daily activities of the patients and were separated
istered on clinicaltrials.gov. All participants gave written informed
by at least 2 hours of rest. All patients used regular prescribed
consent.
medical treatment for COPD and oxygen therapy during effort.
Those experiencing an exacerbation during the study were
Participants excluded from the analysis.
Patients referred to the Cardiopulmonary Rehabilitation Unit of a
subacute rehabilitation center with diagnosis of COPD (Global Interventions
Patients assigned to the CG carried out both aerobic and resistance
List of abbreviations: training following international guidelines.3 Training load for the
BID Barthel Index based on dyspnea cycle ergometer was calculated using the 6-minute walk distance
BODE body mass index, airflow obstruction, dyspnea, and (6MWD) to estimate the peak work rate according to a previously
exercise capacity reported equation.16 The exercise intensity for the first training
CG control group session was calculated as 50% of the estimated peak work rate,
COPD chronic obstructive pulmonary disease and intensity was then increased during the following training ses-
FEV1 forced expiratory volume in 1 second sions according to the level of dyspnea and fatigue as previously
FVC forced vital capacity described.17 Each training session on the cycle ergometer started
ITT intention-to-treat with 3 minutes of warming up followed by 20 minutes of continu-
MCID minimal clinically important difference
ous exercise and finished with 2 minutes of cooling down. Resis-
MEP maximal expiratory pressure
MIP maximal inspiratory pressure
tance training was performed starting at 50% of the 1 repetition
6MWD 6-minute walk distance maximum for 2 sets and 20 repetitions and weekly increased up to
SGRQ St George’s Respiratory Questionnaire 10 repetitions for 3 sets at 70% of 1 repetition maximum. Resis-
tance training and airway clearance techniques were carried out

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Vibration and pulmonary rehabilitation 1459

on alternate days during the additional session. All sessions were percentage of 20%, we determined a sample size of 12 participants
guided by an expert physical therapist specifically trained for per group, for a total of 36 participants.
respiratory disease treatment.
Patients assigned to the vibration intervention protocol group
performed the same cycle ergometer training as the CG while
receiving continuous chest wall vibration for 20 minutes at a fre- Results
quency of 150 Hz.a The vibratory stimulus was delivered to the
cycling patient via 4 effectors positioned between the second and A total of 146 participants were assessed for eligibility into
third intercostal space and between the seventh and ninth intercos- the study, and a total of 40 patients (11 women, 29 men) were
tal space.9 Although higher frequencies are reported to be more included into this trial (fig 1). The mean age was 69 years.
effective in eliciting motor responses,18 we adopted a vibration Patients had a mean percentage predicted FEV1 of 40.2%, an
frequency of 150 Hz because exceeding this limit could create FVC of 82.1%, and an FEV1/FVC of 37.4. At baseline, the
excessive discomfort for patients and excessive noise in the clini- demographic (age, sex, height, weight, body mass index) and
cal setting. clinical (smoking habits, Global Initiative for Chronic Obstruc-
Patients assigned to the vibration sham intervention protocol tive Lung Disease stage, respiratory failure, pulmonary func-
group received usual care as the CG. In addition, they received a tion) characteristics of the participants were similar between
sham intervention as follows: after the same preparation procedure groups (table 1).
as described for the vibration intervention protocol group, the One patient in the CG missed a few sessions because of wors-
vibration device was started, but the effectors were not emitting ening of his clinical conditions, and 2 participants from the vibra-
vibrations. tion intervention protocol group and 1 patient from the vibration
sham intervention protocol group were removed early because of
Outcome measures clinical instability. Thirty-six patients completed the 20 training
sessions according to the study protocol. Compliance with the
Functional exercise capacity and dyspnea were the primary out- vibration intervention was excellent, and none of the patients com-
comes. The 6-minute walk testb was used to assess functional plained of any adverse event or discomfort or asked for discontin-
exercise capacity19 and the Barthel Index based on dyspnea uation of treatment.
(BID)20 to measure the level of dyspnea perceived during basic
daily living activities. ITT analysis
As secondary outcomes, we evaluated the maximal inspiratory
pressure (MIP) and maximal expiratory pressure (MEP)21,c; the ITT analysis showed that 6MWD significantly increased in the
quality of life collecting the St George’s Respiratory Question- vibration intervention protocol group (P=.003), and the percentage
naire (SGRQ)22; and the risk of death using the body mass index, predicted 6MWD increased in the same group (P=.002). Within-
airflow obstruction, dyspnea, and exercise capacity (BODE) group changes in 6MWD are showed in figure 2. The effect size in
index.23 For the extended description of outcome measures see the the vibration intervention protocol group showed a moderate
supplemental appendix S1 (available online only at http://www. effect (d=0.58 and d=0.54, respectively) for the 6MWD and
archives-pmr.org/). 6MWD% variables. No differences occurred within the other
groups or between study groups as reported in table 2.
Statistical analysis BID score diminished significantly in the 3 groups. A similar
reduction occurred in the vibration intervention protocol group
In this study, both intention-to-treat (ITT) and per protocol analy- (P<.001) and in the vibration sham intervention protocol group
sis were used to assess primary and secondary outcomes. After (P<.001), whereas the magnitude of change was less in the CG
evaluating the normality of the distribution with the Shapiro-Wilk (P=.023). The BID effect size was moderate (d=0.78) to small
test, 1-way analysis of variance was used to compare the baseline (d=0.44) for the vibration sham intervention protocol group and
data. For nonnormally distributed data, the Kruskal-Wallis analy- the CG, respectively, whereas a large effect was recorded for the
sis of variance on ranks was applied. The paired t test was used to vibration intervention protocol group (d=1.06).
compare within each group changes from pre- to postintervention. Respiratory muscle parameters (MIP, MEP, cmH2O, and per-
Where the distribution was not normal, data were analyzed with centage predicted) did not change significantly within or between
the Wilcoxon signed-rank test. Analysis of covariance was used to groups.
compare between groups for any variable. The SGRQ total score diminished significantly within the
The magnitude of the results was determined by calculating the vibration intervention protocol group (P=.018) and the vibration
effect size d. According to Cohen, d=0.2 is a small treatment sham intervention protocol group (P=.024) but not in the CG. The
effect, d=0.5 is a moderate effect, and d=0.8 is a large effect. Sta- SGRQ score statistically changed for the symptoms domain in the
tistical analysis was performed using a statistical software,d and vibration intervention protocol (P=.028) and the vibration sham
significance was set at P<.05. intervention protocol (P=.002) groups but not in the CG. The
SGRQ score for the activity domain varied within the vibration
Sample size sham intervention protocol group only (P=.006), whereas the
results of the impact domain changed only in the vibration inter-
The sample size was determined based on the primary outcome, vention protocol group (P=.009). The effect size for the SGRQ
that is, 6MWD, referring to a previous study24 whose effect size total score was small (d=0.36) in the vibration intervention proto-
(d) according to Cohen25 was large (d=0.8). Therefore, for the cal- col group and moderate (d=0.44) in the vibration sham interven-
culation of the sample size, 2 degrees of freedom were considered tion protocol group. For the impact domain, the effect size was
with a power (1-b) of 80% and a of 5%.26,e Considering a dropout small for the vibration intervention protocol group SGRQ

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1460 S. Pancera et al

Fig 1 Flow diagram with phases of the study. Abbreviations: VIP, vibration intervention protocol; VSIP, vibration sham intervention protocol.

(d=0.37) and the activity domain of the vibration sham interven- vibration sham intervention protocol group (d=0.46) and the CG
tion protocol group (d=0.45). (d=0.39).
The BODE index score significantly changed within groups but
to a greater extent in the vibration intervention protocol group
(P=.002; confidence interval,
1.59 to
0.55) compared with the Per protocol analysis
vibration sham intervention protocol group (P=.004) and CG
(P=.011). The BODE index effect size was moderate in the vibra- Per protocol analysis showed no differences in the results com-
tion intervention protocol group (d=0.54) and small in both the pared with the ITT analysis. Only the magnitude of results from

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Vibration and pulmonary rehabilitation 1461

Table 1 Baseline characteristics

VIP (n=14), VSIP (n=13), CG (n=13),
Parameters Mean § SD Mean § SD Mean § SD P Value
Age (y) 71.00§7.56 68.25§6.89 68.50§6.32 .57
Male; female (n) 9; 3 8; 4 8; 4 .88
Height (m) 1.66§0.07 1.70§0.08 1.65§0.09 .39
Weight (kg) 69.67§21.97 65.96§17.58 67.17§18.52 .89
BMI 24.91§6.95 22.87§5.48 24.19§4.38 .68
Pack-years 43.42§19.78 47.50§37.60 44.33§28.38 .94
GOLD .81
GOLD II 2 3 2
GOLD III 6 4 4
GOLD IV 4 5 6
LTOT (n) 7 5 5 .65
FVC (% predicted) 76.83§13.72 85.17§17.75 82.33§23.39 .55
FEV1 (L) 0.95§0.40 0.98§0.34 1.10§0.64 .92
FEV1 (% predicted) 38.75§16.15 38.83§15.50 42.08§16.23 .84
FEV1/FVC (%) 35.81§9.65 10.28§6.36 40.81§13.82 .52
RV (L) 4.88§2.38 4.14§2.48 3.79§1.21 .40
RV (% predicted) 207.25§109.18 179.25§91.82 163.75§58.70 .70
TLC (L) 7.75§2.87 7.16§2.35 6.47§0.91 .54
TLC (% predicted) 131.83§51.03 118.58§28.47 118.17§23.91 .76
NOTE. P values represent the mean differences between groups at baseline (T0). Statistical significance was set at P<.05.
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); GOLD, Global Initiative for Chronic
Obstructive Lung Disease; LTOT, long-term oxygen therapy; RV, residual volume; TLC, total lung capacity; VIP, vibration intervention protocol; VSIP,
vibration sham intervention protocol.

pre- to postintervention varied within groups. No significance was vibration.27 There were no effects on dyspnea, respiratory muscle
found in the between-group analysis. function, or quality of life.
These findings are in line with the open discussion in the litera-
ture about the effectiveness of chest wall vibration in patients with
COPD. In recent years, vibration has been used during rehabilita-
Discussion tion treatments as an airway clearance technique or with the aim
to stimulate the respiratory muscles, consequently reducing dys-
The main objective of this study was to assess the effects of con- pnea and improving exercise capacity, but its efficacy is still dis-
tinuous chest wall vibration on functional exercise capacity and cussed.
dyspnea rate in patients with COPD. The novelty of this study was In individuals with COPD, chest wall vibration in-phase with
the application of continuous chest wall vibration concurrent with inspiration was shown to improve exertional dyspnea in some
aerobic training in a rehabilitation clinical setting to enhance the studies but not in others.9,13,28 According to literature, increasing
effectiveness of the standard pulmonary rehabilitation treatment. the afferent feedback from the parasternal intercostal muscle spin-
Our results highlight a significant improvement in functional exer- dles with chest wall vibration may improve 1 or more of the fol-
cise capacity that reached a minimal clinically important differ- lowing possible contributory factors of dyspnea: (1) central
ence (MCID) in patients with COPD who underwent chest wall respiratory drive (as a result of pulmonary and extrapulmonary
receptor activation); (2) respiratory muscle activity (delaying the
onset of muscle fatigue); and (3) dissociation between efferent
output and afferent sensory inputs.29-31 However, unlike previous
studies, we applied chest wall vibration continuously during the
whole rehabilitation program, focusing mainly on dyspnea related
to functional activities and changes within rehabilitation treat-
ment. Therefore, the failure to improve dyspnea after chest wall
vibration compared with usual care could suggest that the vibra-
tory stimulus did not produce durable adaptations with respect to
the abovementioned mechanisms that contribute to the reduction
of dyspnea, but their acute effects could justify the positive effects
on functional exercise capacity found in our study and still not
explored in the literature.
Fig 2 Changes in 6MWD. Lighter gray represents T0, dark gray repre- Exercise intolerance in COPD indeed involves both respiratory
sents T1 in the timeline. Abbreviations: T0, day 1; T1, day 22; VIP, limitation and lower limb muscle dysfunction32; hence, an attenu-
vibration intervention protocol; VSIP, vibration sham intervention ation of breathlessness during aerobic exercise owing to the effect
protocol. *P<.05 vs baseline. of continuous chest wall vibration may have allowed patients in
 1462
Table 2 Changes in the outcome measures
VIP (n=14) VSIP (n=13) CG (n=13)
T0, T1, D T0-T1, T0, T1, D T0-T1, T0, T1, D T0-T1,
Variables Mean § SD Mean § SD Mean § SD Mean § SD Mean § SD Mean § SD Mean § SD Mean § SD Mean § SD
Functional exercise capacity
6MWD (m) 354.36§81.88 396.93§64.72 42.57§43.87* 345.00§97.14 373.33§110.38 28.33§49.33 376.33§88.06 395.92§100.79 19.58§45.96
6MWD (% predicted) 72.00§17.75 80.94§15.60 8.94§8.87* 70.92§22.09 75.77§23.39 4.84§9.02 75.00§17.11 78.72§19.64 3.72§8.81
Respiratory muscles function
MIP (cmH2O) 60.50 (32, 96)y 66.00 (32, 97)y 3.50 (−9, 53)y 65.39§12.09 66.00§18.61 0.62§14.65 69.43§21.90 70.05§17.87 0.62§12.18
MIP (% predicted) 65.05§27.99 69.75§29.20 4.70§14.10 70.56§16.95 71.18§22.54 0.62§15.44 70.63§22.42 71.30§18.06 0.67§12.72
MEP (cmH2O) 115.00 (67, 247)y 134.50 (73, 159)y 9.00 (−90, 80)y 115.00§21.56 119.15§24.88 4.15§19.82 116.46§39.91 119.57§44.93
3.11§21.67
MEP (% predicted) 65.46§23.13 69.42§15.56 3.96§17.84 66.41§17.06 67.34§11.12 0.94§12.19 69.12§23.47 70.19§22.46 1.07§15.57
Dyspnea rate
MRC 2.00 (0, 4)y 2.00 (0, 3)y
1.00 (
2, 0)*,y 2.00 (1, 4)y 2.00 (0, 4)y
1.00 (
3, 0)*,y 2.00 (1, 3)y 1.00 (0, 3)y
1.00 (
3, 0)*,y
BID 21.29§12.76 10.00§8.56
11.29§8.26z 23.46§14.37 11.85§15.29
11.62§9.45z 24.00 (0, 71)y 19.00 (0, 71)y
4.00 (
38, 5)*,y
SGRQ
Total 53.68§19.73 46.28§21.21
7.41§10.22* 59.83§17.02 52.25§17.74
7.58§10.61* 58.51§18.34 52.71§23.26
5.81§13.86
Symptoms 51.22§26.84 38.84§30.02
12.38§18.80* 60.14§21.05 32.37§18.10
27.76§25.20* 56.45§20.34 49.53§32.32
6.93§27.62
Activity 71.57§23.11 66.29§24.08
5.29§9.75 77.27§15.81 69.57§18.19
7.70§8.39y 71.68§16.49 67.27§20.83
4.41§10.65
Impact 44.02§22.22 35.63§23.31
8.38§10.25* 52.12§18.69 47.84§23.14
4.27§12.07 51.41§21.92 44.81§24.13
6.60§15.63
BODE index score 5.00 (0, 7) y 3.50 (0, 7)y
1.00 (
3, 0)*,y 5.00 (0, 8)y 4.00 (0, 8)y
1.00 (
2, 0)*,y 4.15§1.99 3.39§1.94
0.77§0.93*
NOTE. D values represent the difference between final (T1) and baseline (T0) results for each variable. Reduction in scores of MRC, BID, SGRQ, and BODE indicates improvement.
Abbreviations: MRC, Medical Research Council dyspnea scale; VIP, vibration intervention protocol; VSIP, vibration sham intervention protocol.
* Significant difference pre-post intervention within group (P<0.05).
y
Median (minimum, maximum) values are reported for nonnormally distributed data.
z
Significant difference pre-post intervention within group (P<.001).

S. Pancera et al
Vibration and pulmonary rehabilitation 1463

the intervention group to train at a higher intensity than the con- Conclusions
trols, leading to a greater improvement in functional exercise
capacity.33 Although we did not consider training intensity as Continuous chest wall vibration concurrent with aerobic training
an outcome measure, our data (not reported) supported this in addition to a standard pulmonary rehabilitation program might
hypothesis, showing that training intensity significantly provide benefits on functional exercise capacity compared with
improved within groups, with a larger effect size in the vibra- usual care and might be considered as a safe and well-tolerated
tion intervention protocol group. However, no significant dif- method by patients. Consequently, further studies are needed to
ference in training intensity was found between groups, not verify the effectiveness in patients with COPD and its applicability
allowing a definitive interpretation to the results. In contrast, in the clinical context.
the higher baseline 6MWD may have caused a ceiling effect
in the CG, in line with previous studies.34-36 Alternatively, the
CG may have failed to improve the 6MWD because of a
higher number of nonresponders unable to obtain a clinically
Suppliers
significant improvement in 6MWD.37 a. Vibra Plus; Eurtronik, Bologna, Italy.
Furthermore, chest wall vibration did not seem to provide addi- b. BlueNight Trainer; Sleepinnov Technology, Morains, France.
tional benefit on respiratory muscle function than usual care; nev- c. MicroRPM; Vyaire Medical, Mettawa, IL.
ertheless, a trend toward a greater improvement was observed in d. SigmaPlot, version 11; Systal Software, San Jose, CA.
the intervention group compared with the other groups. As seen e. G*Power, version 3.132; Heinrich-Heine Universit€at
before, respiratory muscle strengthening is 1 of the factors contrib- D€usseldorf, Germany.
uting to dyspnea relief, and therefore, the small improvement in
this outcome partly confirms the reasons why continuous chest
wall vibration did not reduce dyspnea, particularly within rehabili- Keywords
tation treatment. The reasons why respiratory muscle function did
not improve may be related to the specificity of the stimulus Dyspnea; Exercise therapy; Pulmonary disease, chronic obstruc-
required for this purpose38 and because the ventilatory load during tive; Rehabilitation; Respiratory muscles
cycle training may be of insufficient magnitude to confer muscle
gain in patients with COPD.39 Furthermore, changes in respiratory
muscle function may have been less marked because of the base-
line characteristics of our population that showed high MIP val-
Corresponding author
ues. Indeed, it has been suggested that patients with respiratory Simone Pancera, MSc, IRCCS Fondazione Don Carlo Gnocchi,
muscle weakness are better responders to respiratory muscle Via Capecelatro, 66, Milan 20148, Italy. E-mail address: s.
training.38 pancera002@unibs.it.
In spite of better functional exercise capacity in the interven-
tion group, there was no transfer to an additional improvement in
SGRQ or the BODE index. All the study groups exceeded the
MCID for the SGRQ total score; however, according to Dourado References
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