Manual Hyperinflation Improves Alveolar Recruitment in Difficult-to-Wean Patients
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Manual Hyperinflation Improves Alveolar Recruitment in Difficult-to-Wean Patients Suh-Hwa Maa, Tzong-Jen Hung, Kuang-Hung Hsu, Ya-I Hsieh, Kwua-Yun Wang, Chun-Hua Wang and Horng-Chyuan Lin Chest 2005;128;2714-2721 DOI 10.1378/chest.128.4.2714 The online version of this article, along with updated information and services can be found online on the World Wide Web at: http://chestjournal.org/cgi/content/abstract/128/4/2714 CHEST is the official journal of the American College of Chest Physicians. It has been published monthly since 1935. Copyright 2007 by the American College of Chest Physicians, 3300 Dundee Road, Northbrook IL 60062. All rights reserved. No part of this article or PDF may be reproduced or distributed without the prior written permission of the copyright holder (http://www.chestjournal.org/misc/reprints.shtml). ISSN: 0012-3692. Downloaded from chestjournal.org on September 19, 2007 Copyright © 2005 by American College of Chest Physicians
Manual Hyperinflation Improves
Alveolar Recruitment in Difficult-to-
Wean Patients*
Suh-Hwa Maa, DSN; Tzong-Jen Hung, MD; Kuang-Hung Hsu, PhD;
Ya-I Hsieh, MS; Kwua-Yun Wang, MS; Chun-Hua Wang, MD; and
Horng-Chyuan Lin, MD
Study objectives: To investigate the effect of manual hyperinflation (MH) in patients with
atelectasis associated with ventilation support.
Design: Patients were randomized to either an experimental group or a control group.
Setting: Pulmonary ICUs from two hospitals.
Patients: Twenty-three patients with atelectasis associated with ventilation support.
Interventions: The MH technique was at a rate of 8 to 13 breaths/min for a period of 20 min each
session, three times per day for 5 days. The control group received their standard prescribed
mechanical ventilation without supplemental MH. Sputum contents (wet/dry weight ratio,
viscosity), respiratory system capacity (spontaneous tidal volume [VT], maximal inspiratory
pressure, rapid shallow breathing index [f/VT], chest radiograph signs, and PaO2/fraction of
inspired oxygen [FIO2]) were measured just prior to the MH at day 0 as baseline, and at day 3 and
day 6 of the study.
Measurements and results: There were significant improvements in scores over the 6-day study in
the experimental group compared to the control group in spontaneous VT (p ⴝ 0.035) and chest
radiograph signs (p ⴝ 0.040), and a trend toward improvement of f/VT (p ⴝ 0.066) and PaO2/FIO2
(p ⴝ 0.061) after adjustment for covariates. Other outcome variables did not differ significantly
between the experimental and control groups.
Conclusions: MH performed on patients with atelectasis from ventilation support significantly
improved alveolar recruitment. (CHEST 2005; 128:2714 –2721)
Key words: alveolar recruitment; atelectasis; difficult to wean; manual hyperinflation
Abbreviations: ANOVA ⫽ analysis of variance; Fio2 ⫽ fraction of inspired oxygen; f/Vt ⫽ rapid shallow breathing
index; MH ⫽ manual hyperinflation; OR ⫽ odds ratio; Pimax ⫽ maximal inspiratory pressure; Vt ⫽ tidal volume
M echanical ventilation is indicated in acute re-
versible respiratory failure. However, patients
pneumonia,1,2 making ventilation weaning more dif-
ficult3 and resulting in excess morbidity and mortal-
receiving mechanical ventilation may have an in- ity. The cost of maintaining patients on prolonged
creased risk of sputum retention, atelectasis, and ventilation in the ICUs of acute care hospitals are
high.4 Thus, every effort should be made to deter-
*From the School of Nursing (Dr. Maa), Department of Business mine which patients can be rapidly extubated so as to
Administration (Dr. Hsu), Department and Graduate Institute of
Health Care Management, and Department of Thoracic Medi- keep the weaning period to a minimum. Previous
cine II (Drs. C-H Wang and Lin), Chang Gung University, evidence suggests that manual hyperinflation (MH)
Tao-Yuan; Department of Thoracic Medicine (Dr. Hung), Wei
Gong Memorial Hospital, Miao-Li; Department of Nursing (Ms. can mobilize pulmonary secretions, reverse atelec-
Hsieh), Taipei Veterans General Hospital, Taipei; and School of tatic alveoli, and increase alveolar oxygenation. Many
Nursing (Ms. K-Y Wang), National Defense Medical Center, clinical studies have reported the short-term benefits
Taipei, Taiwan.
This study was supported by the National Science Council of of MH on sputum clearance,3,5 reexpansion of atel-
Taiwan, contract No. NSC 90 –2314-B-182– 062. ectasis,5– 8 improvement of dynamic compliance,9
Manuscript received February 2, 2005; revision accepted May 3, and oxygenation.10 –12 However, the lack of standard-
2005.
Reproduction of this article is prohibited without written permission ized methods for the delivery of MH makes the
from the American College of Chest Physicians (www.chestjournal. synthesis and interpretation of the findings difficult.
org/misc/reprints.shtml). The variability in the types of MH circuit (self-
Correspondence to: Suh-Hwa Maa, DSN, School of Nursing,
Chang Gung University, 259, Wen-Hwa First Rd, Kwei-San, inflating manual resuscitation bags vs oxygen-pow-
Tao-Yuan, Taiwan, ROC; e-mail: shmaa@mail.cgu.edu.tw ered, manual resuscitation bags), the method of MH
2714 Clinical Investigations in Critical Care
Downloaded from chestjournal.org on September 19, 2007
Copyright © 2005 by American College of Chest Physiciansdelivery (technique of pausing at full inspiration vs MH, is thought to maintain these pressure gradients
pressing half of the resuscitator), and the variability for an appropriate length of time. This technique
in the dosage of MH (ie, duration) all point toward may influence the distribution of the ventilation25
the need for further development of the knowledge and allow time for alveolar inflation or enlargement,
base in order to guide best practice. as well as the recruitment or unfolding of interde-
Manual hyperinflation is defined as inflating the pendent atelectatic alveoli. Finally, a pressure ma-
lungs using oxygen and manual compression to nometer can improve the performance of MH and
provide a tidal volume (Vt) exceeding baseline Vt, optimize both the safety and the effectiveness of the
and using a Vt that is 50% greater than that treatment.31 Although there is no consensus about
delivered by the ventilator, requiring a peak inspira- specific safe upper limits for peak airway pressure,
tory pressure of from 20 to 40 cm H2O.13 Four barotraumas manifest at peak airway pressures of 26
factors are considered important in performing the to 64 cm H2O as demonstrated by several animal
MH technique: the application of larger-than-nor- studies.20 Therefore, it is reasonable and prudent to
mal Vt breaths,14,15 use of a slow inspiratory flow minimize the peak airway pressure as much as
rate,16,17 an inspiratory pause,18,19 and a pressure possible during MH or any other ventilatory support
manometer.20,21 In addition, the quick release of procedure.32
pressure on expiration leading to a rapid flow of air This study examines the effect of MH in patients
can simulate the effect of a cough.11,22,23 with atelectasis associated with ventilation support.
Even though no comprehensive studies have been The foundation for the practice of MH in this study
done that incorporate and evaluate all four of the is based on the best evidence available from clinical
important MH techniques, there is support from and research literature, and incorporates all four
clinical and research literature on the theoretical factors of MH technique considered to be important,
foundations and effectiveness of each of the factors as described above. The hypothesis of this study is
separately. First, the use of larger-than-normal Vt is that those in the experimental group should have
based on the hypothesis that by delivering a larger- improved sputum contents (wet/dry weight ratio,
volume breath over time, MH may increase the viscosity), respiratory system capacity (spontaneous
expiratory flow rate and assist in moving secretions Vt), maximal inspiratory pressure (Pimax), an im-
toward more proximal airways, where they can be proved rapid shallow breathing index (f/Vt), as well
cleared by suctioning.24 Second, the rate of inflation as improved chest radiograph signs and oxygenation
of the lung as a whole is a function of inflation ratio (Pao2/Fio2).
pressure, compliance, and airway resistance. Nunn25
described the response to passive inflation of the
lungs by the development of a constant airway Materials and Methods
pressure. If a constant inflation pressure is main-
tained, an alveolus with half the compliance but Patient Selection
twice the resistance of another alveolus will increase
in volume by half the volume change of the other Thirty-three patients with atelectasis due to ventilatory support
alveolus. Thus, the relative distribution of gas be- were recruited at the pulmonary ICUs from two hospitals; of
these 33 patients, 23 completed all of the study procedures. This
tween the two alveoli is independent of the rate or study was a two-group, prospective, randomized study lasting 6
duration of inflation. In addition, using both hands to days. Patients were assigned to one of two groups: standard care
compress the bag can produce a Vt that is 50% with supplemental MH (experimental group, n ⫽ 10) or standard
greater than that delivered by the ventilator.26 Fur- care only (control group, n ⫽ 13). The Institutional Ethical
thermore, the rate at which the bag is compressed, Committee approved the study protocol, and all patients gave
informed written consent. The inclusion criteria consisted of the
rather than the resistance of the circuit itself, is the following: age ⱖ 40 years; ventilation support ⬎ 7 days and a
main influence on the peak inspiratory flow positive end-expiratory pressure from 6 to 8 cm H2O; pulmonary
rate.16,17,27 A fast inflation rate that does not allow atelectasis; excessive secretions (⬎ 30 mL/d); and spontaneous
the reservoir bag to fill adequately, and reduces the Vt ⬍ 250 mL and/or Pimax ⬍ 25 cm H2O and/or Vt ⬍ 400 mL
fraction of the inspired oxygen (Fio2).28,29 Moreover, under ventilator assistance. Pulmonary atelectasis was diagnosed
using the following: (1) chest radiography showing increased
delivering an increased Vt via MH may generate infiltration, and (2) physical examination revealing weakness or
adequate transpulmonary pressure gradients to over- muteness of the sounds in the involved area. The structural
come alveolar atelectasis. Atelectatic alveoli do not changes that develop in atelectasis increase the density of the
reexpand immediately when the ventilator cycles lungs. The increase in lung density resists radiograph penetration
with the inspiratory phase because a variable period and is revealed on radiograph films as increased opacity (ie,
whiter in appearance). Thus, the more severe the atelectasis, the
of time is required before the alveolar critical open- denser the lungs, and the whiter the radiograph film. Patients
ing pressure is reached.30 Therefore, the third im- were assessed clinically and with a chest radiograph at recruit-
portant factor, the use of an inspiratory hold during ment to ensure the absence of a Fio2 ⱖ 0.6 requirement,
www.chestjournal.org CHEST / 128 / 4 / OCTOBER, 2005 2715
Downloaded from chestjournal.org on September 19, 2007
Copyright © 2005 by American College of Chest Physicianspulmonary pathology (for example, ARDS), active infection, unidirectional expiratory valve pressure-manometer was con-
acute cardiovascular dysfunction, or other systemic diseases. The nected to the endotracheal tube or tracheostomy, the port was
trial took place between January 2001 and June 2001. There were occluded at end-expiration for 20 s, and after three spontaneous
three different types of ventilation systems used throughout this maximal inspiratory efforts the Pimax was recorded.33,34 The f/Vt
study (models 7200, 740, or 760; Nellcor Puritan Bennett; score was measured during mechanical ventilation as a calcula-
Temecula, CA). tion of the ratio of the respiratory rate per minute (frequency) to
the Vt setting (liters) from the display on the ventilation. A
portable radiograph machine was used, and a staff radiologist
Standard Care
reported the chest radiograph findings each morning. Scores
All subjects were asked to continue any current prescribed were given as 1 (improved) or 2 (not improved).
medication (such as anticholinergic inhaled agents, inhaled cor- Nurses also recorded the ventilator volume and measured the
ticosteroids, theophylline, prednisolone, or erythromycin) and cuff pressure (Control-inflator; VBM Medizintechnik; Sulz am
chest physiotherapy (such as chest percussion, positioning, and Neckar, Germany) at least once or twice daily for patients with
suction) throughout the experiment. For the control group, these tracheostomy. The volume needed to attain a full seal should be
were the only prescribed treatments. None of the subjects recorded at least once or twice daily. The need for increasingly
received any sedation or narcotics. larger volumes indicates an expanding trachea. The pressure was
kept at levels ⬍ 20 mm Hg. If there was an air leak in the cuff or
cuff inflation system, nurses reinflated the cuff via a stopcock. If
MH the ventilator could be set to compensate for the leak, the patient
was not reintubated. If significant aspiration or inadequate
To ensure that uniform and correct techniques were employed,
ventilation was present, a new tube was inserted.
MH was administered by only one investigator. A 2.0-L reusable
manual resuscitator (model 2153 MR100 plus; Galemed Corpo-
ration; Taipei, Taiwan) was used to deliver the MH breaths, and Oxygenation Ratio
was connected to a flow of 100% oxygen at 15 L/min (calibrated
with an oxygen analyzer). A force meter (Inspiratory Force Pao2/Fio2 was measured during mechanical ventilation as
Meter; Boehringer Laboratories; Norristown, PA) was connected derived from arterial blood gas analysis and the Fio2 on days 0
between the resuscitator and the patient. Patients received MH (baseline) and 6 of the study. A calibrated blood gas analyzer
to a peak airway pressure of 20 cm H2O by use of the resuscitator. (model 278; Ciba-Corning; Medfield, MA) was used for arterial
The resuscitator was slowly compressed with both hands, and an blood gas analysis, and the Fio2 was read from the display on the
inspiratory breath was maintained for 3 to 5 s at the end of ventilator obtained just prior to MH.
pressing half of the resuscitator, and then completely pressing the
resuscitator. Expiration was passive and unobstructed to facilitate Statistical Analysis
expiratory flow with no positive end-expiratory pressure applied.
Sufficient time was allowed for the resuscitator to fill completely Statistical software (version 10.0; SPSS; Chicago, IL) was used
prior to the next breath. Airway suctioning of the endotracheal for data analysis. 2 test and Fisher Exact Test were used to assess
tube was performed using size 14 catheters (Pahsco; Pacific the success of the randomization process in achieving two
Hospital Supply; Taipei, Taiwan) at the end of the MH proce- comparable groups. A t test was performed to establish the
dure. The MH procedure was carried out at a rate of 8 to 13 baseline stability of the dependent variables. A repeated-mea-
breaths/min for a period of 20 min for each session tid (at 7:40 sures analysis of variance (ANOVA) was performed to compare
am, 11:40 am, and 3:40 pm) for 5 days on days 1 to 5 of the study. scores over time between the experimental and the control
groups on each of the seven dependent variables measured at
each of the three time points: day 0 (baseline), day 3, and day 6
Sputum Sampling
of the study. This method accounted for six covariates: sex (male,
Nurses were instructed to collect and record the total amount female), age, setting (medical center, local hospital), intubation
of daily sputum (milliliters per 24 h) throughout the study. An (endotracheotomy, endointubation), logarithm of length of ven-
aliquot of sputum from each patient’s total amount of daily tilation prior to enrolment, and logarithm of total sputum
sputum was freeze-dried (at – 80°C, at a negative pressure of 40 amount.35 The null hypothesis is that there is no interaction
cm H2O) overnight to measure the wet/dry weight ratio. between group and study duration, ie, the 5 days of treatment
The viscosity of the sputum was measured using a viscometer with repeated measures on days 0, 3, and 6. There is a gradual
at room temperature (25°C) with distilled water as a control, increase in treatment effect if there is interaction between the
using sputum sampled by nurses at 7 am on days 0 (baseline), 3, group and the duration of the treatment. The Mantel-Haenszel
and 6 of the study. After receiving chest percussion, the sputum 2 test for categorical data, adjusted odds ratio (OR), and
was collected by airway suctioning of the endotracheal tube into multiple logistic regression were performed on the chest radio-
a sterile pot. graph scores. The OR was calculated as the odds in favor of
clinical improvement in the treatment group divided by the odds
in favor of clinical improvement in the control group. Signifi-
Measurement of Respiratory System Capacity cance was indicated at p ⬍ 0.05.
Respiratory system capacity measurements were obtained 30
min after sputum sampling and just prior to the 7:40 am MH on
days 0 (baseline), 3, and 6 of the study. The spontaneous Vt score Results
was measured during ventilation disconnection (Haloscale
Wright Respirometer; Ferraris Medical Limited; Middlesex, UK) Sample
by a respiratory therapist as spontaneous respiratory volume
(milliliters) per minute divided by respiratory rate per minute. Initially, 33 patients agreed to participate in this
The Pimax was measured during ventilation disconnection with investigation; of these, 10 patients withdrew. Twen-
the inspiratory force meter by the respiratory therapist. A ty-three patients (n ⫽ 23) completed the full course
2716 Clinical Investigations in Critical Care
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Copyright © 2005 by American College of Chest Physiciansof treatment. The attrition rate in this experiment Table 2 shows the actual values of the outcome
was high (30%), perhaps because of the characteris- variables in all patients at baseline. Differences in
tics of respiratory failure from mechanical ventilator baseline values between the two groups were not
support. Of the 10 patients who dropped out, 3 died statistically significant except for the sputum
(1 from the experimental group and 2 from the amount. The logarithm of the total sputum amount
control group), 4 withdrew voluntarily (3 from the was used as covariates in the repeated-measures
experimental group and 1 from the control group), ANOVA model; therefore, the data from all the
and 3 received oxygen content ⬎ 50% during the study subjects were included in the analyses.
period (1 from the experimental group and 2 from the
control group). As most of the withdrawals were for
medical reasons, there is reason to hypothesize that Outcome Measures
some of these patients might have benefited from MH. Outcome measure scores are compared in Table 3,
In addition, there were no statistically significant dif- and the mean scores and the p value for their
ferences in baseline demographics, clinical characteris- group ⫻ time interaction in repeated-measures ANO-
tics, or outcome measurements between those who VAs adjusted for covariates are listed. The spontaneous
withdrew and the remaining participants. Vt and chest radiograph scores show significant differ-
ences between the experimental and control groups,
Patient Characteristics and the f/Vt and Pao2/Fio2 scores show a trend toward
Table 1 lists the sample baseline demographic and improvement in the experimental group compared to
clinical characteristics including intubation, setting, the control group.
and length of ventilation prior to enrollment. There In the experimental group, spontaneous Vt scores
were no statistically significant differences between of 196.3 mL at baseline increased to 270.5 mL on
the subjects of the two groups. The sample contained day 6 (indicating an improvement) compared to the
more men (n ⫽ 17) than women (n ⫽ 6); 74% of the control group, which increased from 208.49 mL at
subjects were ⬎ 65 years of age, 100% were married, baseline to 220.14 mL on day 6 (p ⫽ 0.035; Fig 1).
and 74% had no history of smoking. All subjects were Furthermore, in the experimental group, f/Vt scores
receiving mechanical ventilation for at least 7 days of 216.59 at baseline decreased to 150.21 on day 6
prior to study entry. The average Fio2 was 35%; compared to the control group, which decreased
pneumonia was diagnosed in 17 persons, and lower- from 174.04 to 164.74 (p ⫽ 0.066; Fig 2). Moreover,
lobe atelectasis was found in 19 persons. in the experimental group, Pao2/Fio2 scores in-
creased from 222.07 at baseline to 264.45 on day 6
compared to the control group, which decreased
Table 1—Characteristics of Subjects* from 228.64 to 203.53 (p ⫽ 0.061; Fig 3). Further, in
the experimental group, chest radiograph scores
Experimental Control All p improved 15.55-fold (95% confidence interval, 1.14
Characteristics Group Group Subjects Value†
to 239.77; p ⫽ 0.040) after adjustment for covariates
Total subjects, No. 10 13 23
Sex 0.46
Male 8 (80) 9 (69) 17 (74)
Female 2 (20) 4 (31) 6 (26) Table 2—Comparison of Baseline Measurements
Age, yr 0.54 Between Groups (n ⴝ 23)*
ⱖ 65 7 (70) 10 (77) 17 (74)
ⱕ 64 3 (30) 3 (23) 6 (26) Experimental Control p
Cigarette history 0.20 Variables Group (n ⫽ 10) Group (n ⫽ 13) Value†
No 6 (60) 11 (85) 17 (74)
Sputum content
Yes 4 (40) 2 (15) 6 (26)
Intubation 0.51 Amount, mL/24 h 186.50 ⫾ 116.57 94.62 ⫾ 53.64 0.02
Tracheostomy 3 (30) 5 (39) 8 (35) Wet/dry weight 27.82 ⫾ 11.48 19.29 ⫾ 13.67 0.13
Endotracheal tube 7 (70) 8 (61) 15 (65) ratio, %
Setting 0.31 Viscosity, min 9.67 ⫾ 17.91 8.57 ⫾ 12.60 0.87
Medical center 8 (80) 8 (61) 16 (70) Respiratory system
Local hospital 2 (20) 5 (39) 7 (30) capacity
Length of ventilation prior 0.40 Spontaneous Vt, mL 196.30 ⫾ 80.87 208.49 ⫾ 54.56 0.67
to enrollment, d Pimax, cm H2O 27.00 ⫾ 16.87 20.92 ⫾ 10.46 0.30
7 5 (50) 3 (23) 8 (35) f/Vt 216.59 ⫾ 146.62 174.04 ⫾ 66.62 0.36
8 to 13 2 (20) 3 (23) 5 (22) Oxygenation ratio
ⱖ 14 3 (30) 7 (54) 10 (43) Pao2/Fio2 222.07 ⫾ 93.94 228.64 ⫾ 131.84 0.90
*Data are presented as No. (%) unless otherwise indicated. *Data are presented as mean ⫾ SD.
†2 and Fisher Exact Test. †t test.
www.chestjournal.org CHEST / 128 / 4 / OCTOBER, 2005 2717
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Copyright © 2005 by American College of Chest PhysiciansTable 3—Repeated-Measures ANOVA on Outcome Measures Between Experimental and Control Groups (n ⴝ 23)*
Outcome Measures Experimental Group (n ⫽ 10) Control Group (n ⫽ 13) p Value†
Sputum content
Sputum wet/dry ratio, % 0.831
Day 0 (baseline) 27.82 ⫾ 11.48 19.29 ⫾ 13.67
Day 1 28.36 ⫾ 11.32 19.38 ⫾ 12.65
Day 2 32.01 ⫾ 19.08 20.52 ⫾ 13.95
Day 3 25.83 ⫾ 9.25 20.27 ⫾ 18.00
Day 4 48.76 ⫾ 51.59 19.89 ⫾ 16.07
Day 5 37.22 ⫾ 35.99 18.87 ⫾ 14.28
Sputum viscosity, min 0.145
Day 0 (baseline) 9.67 ⫾ 17.91 8.57 ⫾ 12.60
Day 3 5.85 ⫾ 4.98 13.01 ⫾ 21.08
Day 6 5.49 ⫾ 5.35 24.60 ⫾ 23.95
Respiratory system capacity
Spontaneous Vt, mL 0.035
Day 0 (baseline) 196.30 ⫾ 80.87 208.49 ⫾ 54.56
Day 3 287.07 ⫾ 120.03 223.61 ⫾ 63.26
Day 6 270.50 ⫾ 98.65 220.14 ⫾ 79.34
Pimax, cm H2O 0.194
Day 0 (baseline) 27.00 ⫾ 16.87 20.92 ⫾ 10.46
Day 3 30.30 ⫾ 10.26 17.92 ⫾ 9.54
Day 6 36.10 ⫾ 16.16 18.38 ⫾ 8.14
f/Vt 0.066
Day 0 (baseline) 216.59 ⫾ 146.62 174.04 ⫾ 66.62
Day 3 133.67 ⫾ 84.08 144.22 ⫾ 65.55
Day 6 150.21 ⫾ 66.12 164.74 ⫾ 101.50
Chest radiographs 0.040
Improved/not improved, No. 9/1 6/7
Adjusted OR 16.56 1.00
95% confidence interval for OR 1.14–239.77
Oxygenation ratio
Pao2/Fio2 0.061
Day 0 (baseline) 222.07 ⫾ 93.94 228.64 ⫾ 131.84
Day 6 264.45 ⫾ 113.41 203.53 ⫾ 96.17
*Data are presented as mean ⫾ SD unless otherwise indicated.
†Treatment ⫻ time interaction in repeated-measures ANOVA, adjusted for sex, age, setting, intubation, logarithm of length of ventilation prior
to enrollment, and logarithm of total sputum amount.
Figure 1. Mean values of spontaneous Vt in both groups;
horizontal bars ⫽ ⫹ 1 SD. p ⫽ 0.035 refers to differences be- Figure 2. Mean values of f/Vt in both groups; horizontal
tween groups over time, with changes only on day 3 and day 6 bars ⫽ ⫹ 1 SD. p ⫽ 0.066 refers to differences between groups
while adjusting for sex, age, setting, intubation, logarithm of over time, with changes only on day 3 and day 6 while adjusting
length of ventilation prior to enrollment, and logarithm of total for sex, age, setting, intubation, logarithm of length of ventilation
sputum amount. Higher spontaneous Vt values represent pa- prior to enrollment, and logarithm of total sputum amount.
tients with atelectasis associated with ventilation support-im- Lower f/Vt values represent patients with atelectasis associated
proved alveolar recruitment. with ventilation support-improved alveolar recruitment.
2718 Clinical Investigations in Critical Care
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Copyright © 2005 by American College of Chest Physiciansimprovement in respiratory system capacity and
oxygenation ratio, evidenced by the scores of spon-
taneous Vt and chest radiograph signs, and a trend
toward improvement of f/Vt and Pao2/Fio2 com-
pared to the control groups, after adjusting for the
effects of sex, age, setting, intubation, logarithm of
length of ventilation prior to enrolment, and loga-
rithm of total sputum amount. These results are not
consistent with the fact that the MH technique was
initially designed to enhance clearance of airway
secretions.27 Nevertheless, it supported the initial
hypothesis of this study, that MH improves alveolar
recruitment by delivering a larger-volume breath
over time,24 and by the development of a constant
airway pressure25 in patients with atelectasis from
mechanical ventilation. In addition, MH produced
no adverse events in the experimental group, as none
of the patients experienced pneumothorax, suffoca-
Figure 3. Mean values of Pao2/Fio2 in both groups; horizontal tion, or hypotension during or following MH.
bars ⫽ ⫹ 1 SD. p ⫽ 0.061 refers to differences between groups
over time, with changes only on day 6 while adjusting for sex, age, However, potential limitations of this investigation
setting, intubation, logarithm of length of ventilation prior to should be considered when interpreting the findings.
enrolment, and logarithm of total sputum amount. Higher Pao2/ These include the following: many of the outcome
Fio2 values represent patients with atelectasis associated with
ventilation support-improved alveolar recruitment. measures have a subjective component to them,
because the respiratory therapist who scored these
outcomes was not blinded; failure to obtain out-
come data of successfully weaned patients before
they completed this study; length of ventilation;
compared with the control group. Scores in sputum and the small sample size. In addition, this model
wet/dry weight ratio increased from 27.82% at base- did not account for cigarette consumption, length
line to 37.42% on day 6 in the experimental group of atelectasis, and the severity of the illness, all of
and decreased from 19.29 to 18.87% in the control which could account for group differences over
group; scores in sputum viscosity decreased from time. Future studies should incorporate such risk
9.67 min at baseline to 5.49 min on day 6 in the adjustment using standard severity of illness mea-
experimental group, and increased from 8.57 to sures as APACHE (acute physiology and chronic
24.60 min in the control group, Pimax scores of health evaluation)36 or sequential organ failure
27.00 cm H2O at baseline increased to 36.10 cm assessment37 scores.
H2O on day 6 in the experimental group, and Further study on the effects of MH should be
decreased from 20.92 to 18.38 cm H2O in the control conducted using different resuscitation circuits (such
group after adjustment for covariates compared with as MH to 30 or 35 cm H2O), different subject groups
the control group, even though these changes were (such as receiving ventilatory support for ⬍ 7 days,
not statistically significant. and differentiating between chronic and acute atel-
ectasis), and different operators (such as physiother-
apists, respiratory therapists, or nurses). Additional
Discussion studies are also needed to elucidate the long-term
outcomes such as time to extubation, time to dis-
To our knowledge, this is the first study to examine charge, ventilator-free days, and discharge status
the potential benefits of MH to 20 cm H2O by (home, long-term pulmonary care, death). Specifica-
oxygen-powered, manual resuscitation bag with an tions by the practitioner, and patient preferences for
inspiratory breath-hold of 3 to 5 s, while pressing half treatment duration and frequency should also be
of the resuscitator, in a group of intubated patients explored.
with atelectasis. In addition, this study employed
methodologic features that strengthened validity and
reliability of the findings, including the randomiza- Conclusion
tion of subjects to groups and multivariate analysis
controlling for known covariates. This study provides evidence that MH performed
Those receiving MH had statistically significant in a stable patient with atelectasis associated with
www.chestjournal.org CHEST / 128 / 4 / OCTOBER, 2005 2719
Downloaded from chestjournal.org on September 19, 2007
Copyright © 2005 by American College of Chest Physiciansventilation can improve spontaneous Vt and chest 11 Jones AYM, Hutchinson RC, Oh TE. Effects of bagging and
radiograph signs, and a trend toward improvement of percussion on total static compliance of the respiratory
system. Physiotherapy 1992; 78:661– 666
f/Vt and Pao2/Fio2. MH is a nursing intervention
12 Tweed WA, Phua WT, Chong KY, et al. Tidal volume, lung
that could be implemented without a physician’s hyperinflation and arterial oxygenation during general anaes-
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www.chestjournal.org CHEST / 128 / 4 / OCTOBER, 2005 2721
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Copyright © 2005 by American College of Chest PhysiciansManual Hyperinflation Improves Alveolar Recruitment in
Difficult-to-Wean Patients
Suh-Hwa Maa, Tzong-Jen Hung, Kuang-Hung Hsu, Ya-I Hsieh, Kwua-Yun
Wang, Chun-Hua Wang and Horng-Chyuan Lin
Chest 2005;128;2714-2721
DOI 10.1378/chest.128.4.2714
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