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Comparison of manual and mechanical chest percussion in hospitalized patients with cystic fibrosis
Comparison of manual and mechanical chest percussion in hospitalized patients with cystic fibrosis Martin L. Bauer, MD, Julie M c D o u g a l , MAE, RRT, a n d Robert A. S c h o u m a c h e r , MD From the Pediatric Pulmonary Section, Universityof Alabama at Birmingham and Children's Hospital of Alabama, Birmingham
We compared the efficacy of manual and mechanical chest percussion during hospitalization for acute exacerbations of cystic fibrosis by evaluating changes in spirometry values. Fifty-one participants were randomly assigned to receive manual or mechanical chest percussion three times a day. Twenty-two participated during one subsequent admission and were assigned to the opposite form of chest percussion. The two groups were equal in severity of illness (mean National Institutes of Health score [_+SEM]: manual = 66.7 ± 2.2; mechanical = 65.8 ± 2.2; p = not significant). Mean improvement in forced expiratory volume at I second, forced vital capacity, and forced expiratory flow between 25% and 75% of forced vital capacity (±SEM) for manual percussion was 32.6% ± 7%, 27.2% ± 5%, and 38.1% ± 10%, and for mechanical percussion was 28.5% ± 4%, 28.7% ± 4%, and 25.1% ± 8%, respectively; p = not significant. Our participants did not prefer mechanical chest percussion. Although equal efficacy of outpatient therapy remains to be proved, this study suggests that patients can be encouraged to use the form of chest percussion that they prefer. (J PEDIATR1994;124:250-4)
The combination of chest percussion and postural drainage reduces the rate of deterioration in lung function in patients with cystic fibrosis.i, 2 Unfortunately, compliance with daily percussion and postural drainage is less than optimal because percussion can be time-consuming and uncomfortable, and it requires assistance. It has been suggested that mechanical percussion provides greater comfort and independence than manual percussion, thus improving patient compliance.3, 4 Many centers use both manual and mechanical percussion 1, 3, 4; others, including our own, have taught that manual percussion is superior. No reports support either the equivalence of manual and mechanical percussion Submitted for publication March 23, 1992; accepted Oct. 1, 1993. Reprint requests: Martin L. Bauer, MD, Children's Mercy Hospital, 2401 Gillham Rd., Kansas City, MO 64108. Copyright © 1994 by Mosby-Year Book, Inc. 0022-3476/94 $3.00 + 0 9/20/51812
250
or the superiority of one over the other. Furthermore, no report objectively assesses patient preference or compliance with mechanical percussion. Three studies have attempted to compare manual and mechanical percussion in cystic fibrosis,3-5 but they evaluated the effect of only one session of each. The report by Desmond et al. 6 indicates that, rather than comparing the effect of the two techniques, these articles more accurately FEV1
Forced expiratory volume at 1 second
describe patient compliance during the 3 weeks before the study. To determine whether manual percussion and mechanical chest percussion are equivalent, we compared the therapeutic efficacy of manual percussion and mechanical percussion in patients hospitalized for an acute exacerbation of cystic fibrosis by measuring spirometry, weight gain, and
The Journal of Pediatrics Volume 124, Number 2
duration of hospitalization. We also evaluated patient preference by questionnaire and interview. METHODS
Before initiation of this study, a postcard questionnaire was mailed to every patient of our cystic fibrosis center. The patients were asked to circle yes or no in response to the following two questions: Have you ever used a mechanical percussor? Do you presently use a mechanical percussor? They could check a box for "manual percussion," "mechanical percussion," or "no preference" in response to the question, Do you hav e a preference? Space was provided to respond to a request: Please explain your preference or lack of preference. Several months after the returned postcard questionnaires were evaluated, a letter describing this study was mailed to each patient registered with our cystic fibrosis center. The study was further explained and questions were answered during routine visits. From August 1989 through February 1992, at the time of admission for an acute exacerbation of cystic fibrosis or as soon after admission as possible, all patients were screened for their ability to cooperate with spirometrY and willingness to participate in the study. Those who could perform adequate spirometry and who signed consent forms were randomly assigned to receive either manual or mechanical percussion for the entire hospitalization. A participant admitted to th e hospital twice during the course of the study was allowed to participate a second time but was nonrandomly assigned to receive the form of percussion not received during the first participation. No patient was allowed to participate more than twice. On entrance into the study, patients were interviewed by the principal investigator to obtain baseline clinical and historical information and were asked about their use of mechanical and manual percussion and their preference, as described above. Percussion was performed three times a day by hospitalemployed respiratory care practitioners who recorded each session in the hospital chart, noting time, positions, cough and secretion assessments, oximetry readings, and complications. Each percussion session was performed i n two upright positions (upper portion of the back and upper anterior portion of the chest), four flat positions (mid portion of the chest, anterior portion of the back, left and right sides), and four Trendelenburg positions (lower portion of the chest, anterior portion of the back, left and right sides). Total duration of each percussion session was approximately 30 minutes. Manual percussion was performed by practitioners with cupped hands. Mechanical percussion was provided by practitioners with a Vibracare percussor (General
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Physiotherapy, St. Louis, Mo.) or a model 9000 percussor (Puritan-Bennett Corp., Overland Park, Kan.) at a frequency of 25 to 35 Hz, 7 with pressure to the chest wall sufficient to PrOduce vibration of the participant's voice. 8 Registered respiratory car e practitioners trained in pediatric pulmonary function studies and dedicated to the pulmonary function laboratory supervised all spirometry, which was performed in accordance with the American Thoracic Society guidelines. 9 Participants performed spirometry on a CDX Spiro automate d spirometer (model 110; CDX Corp., Aurora, Colo.) in the morning on Mondays, Wednesdays, and Fridays during hospitalization. Most participants also performed spir0metrY on the day of admission. Spirometry values were recorded as the percentage of the predicted value; predicted values were calculated according to the formulas of Knudson et al. 1° Participants were weighed daily. National Institutes of Health scores 11 were determined on the date of admission. All other diagnostic and therapeutic interventions were determined at the discretion of the attending physician, a pediatric pulmonoiogist on staff at Children's Hospital of Alabama. Medication given to each participant during each admission was documented and tabulated by chart review after discharge from the hospital. We attempted to contact all participants by telephone after discharge from the hospital to ask whether they had a preference between manual and mechanical percussion and, if so, on what factors the preference was based. Statistical analysis. Our study was designed to provide a power of 90% to detect a 10% difference in improvement in forced expiratory volume at 1 second between the two groups, assuming an effect size of one or greater for a twosided test of significance, a standard deviation in FEV1 of 6% of the predicted value (extrapolated from reported spirometry values in hospitalized patients with cystic fibrosisl2"14), andan a of 0.05.15 Improvement in spirometry was calculated by the following formula: 100 * (Discharge spirometry - Admission spirometry) Admission spirometry and expressed as the percentage o f improvement. Comparisons between groups were analyzed by unpaired t test on clinical data, paired t test on percentage of improvement, and linear regression analysis of spirometry values. Twotailed Fisher Exact Test was applied to the comparison of medications between groups. 16, 17 Approval. The study protocol was approved by the institutional review board of the University of Alabama Birmingham and Children's Hospital of Alabama before initiation of the study. All participants gave informed consent.
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Table I. Clinical features
n All participants 36 37 Crossover group 22 22
Treatment group (percussion)
NIH score
Hospital days
Age (yr)
Sex (M/F)
Manual Mechanical
66.7 ± 2.2 65.8 + 2.2
12.5 ± 0.5 11.4 ___0.5
17.0 ± 1.4 15.9 ± 1.4
18/18 19/18
Manual Mechanical
63.5 + 2.7 63.8 ___2.7
12.4 _+ 0.6 11.0 _+ 0.5
17.5 --- 2.1 17.5 + 2.0
12/10 12/10
Values are expressed as mean _+ SEM. p = not significant for all comparisons. NIH, National Institutes of Health.
Table II. Effect of severity of illness on pulmonary function improvement NIH score
FEVI
FVC
FEF25.75
Table III. Linear regression analysis of spirometry during hospitalization n
>50
28 ± 4
27 ± 3
26 ± 7
62
--<50
47 ± 10
31 ± 7
60 + 15
11
Values (except NIH scores) are expressed as percentage (_+SEM) of improvementbetweenadmission and dischargevalues,p > 0.05 for all comparisons. NIH, National Institutes of Health; FVC, forced vital capacity; FEF2~-75, forced expiratory flow between 25% and 75% of FVC. RESULTS Between Aug. 9, 1989, and Feb. 9, 1992, there were 246 admissions for cystic fibrosis to Children's Hospital of Alabama; 189 of these admissions were of 66 patients more than 6 years of age. O f these 66 patients, 54 agreed to participate in this study. Three dropped out: one was dismissed after only 2 days of hospitalization, one was not compliant with the protocol, and one complained that manual percussion was painful. Therefore 51 patients participated fully in the study, providing the data for analysis. Of the 51 participants, 27 were admitted a second time during the study and agreed to participate in the opposite arm of the study. O f these 27 participants, five were excluded: two were dismissed early, one was noncompliant, and two, assigned to mechanical percussion, requested to return to manual percussion because of personal preference. Therefore 22 patients (crossover group) participated fully in both arms of the study. A total of 37 participants received mechanical percussion and 36 received manual percussion. There was no difference in National Institutes of Health scores or duration of hospitalization between the groups, either in the total population of participants or in the crossover group. Sex and age distributions were equivalent (Table I). There was no difference between groups in medication given during hospitalization (data not shown). Patients with more severe manifestations of cystic fibrosis, as defined by lower Na-
Spirometry value FEV1 FVC FEF25-75
Treatment group (percussion) Manual Mechanical Manual Mechanical Manual Mechanical
Baseline
Rate of change
42.5 39.5 62.0 59.8 20.8 18.0
1.0 1.3 1.3 2.0 0.6 0.6
+ 3.4 + 2.7 _+ 3.2 _+ 3.2 + 3.5 ± 2.3
+ 0.2 ± 0.2 +_ 0.2 _+ 0.3 ___0.2 + 0.2
Comparison of mean difference( _+SEM) in rate of improvementwith time. FEVb FVC, and FEF25_75baselinevalues are expressedas percentageof the predictedvalue.Rate of change is rate of improvementin spirometryper day of hospitalization, p = not significant for all comparisons. FVC, Forced vital capacity; FEF25-zs,forced expiratory flowbetween 25% and 75% FVC.
tional Institutes of Health scores, had greater improvement in lung function during hospitalization (Table II). There was no difference in weight gain during hospitalization between the groups. In the total group, mean weight gain ( + S E M ) was 1.0 ___ 0.2 kg and 0.9 + 0.2) kg for manual and mechanical percussion groups, respectively. In the crossover group, respective weight gain was 0.8 + 0.4 kg and 1.0 _+ 0.2 kg. Linear regression analysis of spirometry values during hospitalization revealed no difference between manual and mechanical percussion (Table III). A comparison of improvement in spirometry values between admission and discharge revealed no difference between manual and mechanical percussion (Table IV). This remained true when we analyzed the crossover group separately. Prestudy questionnaire cards were sent to all 168 patients in our registry in July 1989. Fifty-seven patients responded; 16% preferred mechanical percussion, 3 3% preferred manual percussion, and 51% either had no preference or could not compare the two because they had not used mechanical percussion. Three patients claimed that they had never used a mechanical percussor but preferred mechanical percus-
The Journal of Pediatrics Volume 124, Number 2
sion: two thought it sounded as though mechanical percussion would work better, and one who did not receive assistance from any caregiver thought that a mechanical percussor would be helpful. Of the 21 respondents who had ever used a mechanical percussor, 29% preferred mechanical percussion, 48% preferred manual percussion, and 24% had no preference. Seventeen of the respondents were using a mechanical percussor for at least some of their therapy at the time of their response. We obtained follow-up telephone responses from 38 of the 51 participants. Before participation, 26% preferred mechanical percussion, 37% preferred manual percussion, and 37% had no preference or were unable to make a comparison because they had never used a mechanical percussor. After participation, 47% preferred mechanical percussion, 26% preferred manual percussion, and 26% had no preference. Of the 28 respondents who received mechanical percussion during participation in the study, 57% preferred mechanical percussion, 11% preferred manual percussion, and 32% had no preference. DISCUSSION As a group, our patients did not report a preference for mechanical percussors. This finding conflicts with suggestions that the mechanical percussor is preferred by patients.3, 4 Before the study, the patients in our practice were told that manual percussion was preferable to mechanical percussion, so it is not surprising that only 16% of our patients expressed preference for mechanical percussion at that time. After completion of this study, the availability of mechanical percussion was considered advantageous by almost half of our patients with cystic fibrosis. This represents a significant change in perception. On the other hand, only slightly more than half of our participants who experienced mechanical percussion preferred mechanical percussion after the study, indicating that although experience with the percussor was favorable, it was not overwhelmingly so. Only three patients dropped out of the study because of dissatisfaction with the mechanical percussor, one because mechanical percussion was painful, and two because of perceived lack of benefit. These data do not support a general preference for one form of percussion over the other. Rather, preference is subject to significant individual variability and probably depends on a combination of perceived comfort, convenience, and benefit. The observed change in patient perception of the value of mechanical percussion might have been either the result of objective evaluations by patients who had previously avoided mechanical percussion because of advice from physicians in our group or the result of the change in attitude of the center's physicians and staff concerning the use of mechanical percussion.
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253
Table IV. Improvement in spirometry
n
Treatment group (percussion)
FEV1
FVC
FEF25.7s
All participants 36 Manual 32.6 ___7 27.2 _+ 5 38.1 _+ 10 37 Mechanical 28.5 + 4 28.7 + 4 25.1 ~ 8 Crossover group 22 Manual 35.6 ___9 32.4 + 6 38.1 _+ 14 22 Mechanical 30.3 _+ 6 27.5 + 5 33.4 _+ 11 Change in spirometryvaluebetweenadmissionand dischargeexpressedas percentage (_+SEM) of increaseabovebaseline,p = not significantfor all comparisons. FVC, Forcedvital capacity;FEF2s-75,forcedexpiratoryflowbetween 25% and 75% FVC. The observed improvement in pulmonary function in our patient population is comparable to that reported by Smith et a1.,12 even though our patients were admitted with better lung function and discharged after fewer hospital days than in their study. Improvement in our patients was somewhat less than that reported by Redding et al. 13 and by Cerny et al., 14 but these investigators studied fewer patients with lower lung function on admission and longer hospitalization. The three cited studies conflict in their reports of improvement in pulmonary function when severely ill patients are compared with those who are less sick. Redding et al. 13 demonstrated less improvement in the sicker patients, whereas Smith et alJ 2 and Cerny et alJ 4 demonstrated greater improvement in the sicker patients. Our data agree with the latter finding. Patients with greater severity of illness already have lower function and thus require less absolute improvement to yield a greater percentage of improvement. The fact that our patients were not as ill on admission but demonstrated improvement comparable to that in previous studies suggests that our patients achieved optimal benefit from their hospital treatment, and validates our data base for analysis. We found no significant difference in therapeutic efficacy between mechanical and manual chest percussion in hospitalized patients with cystic fibrosis. Our study design allows us to conclude that, if our data failed to detect a difference in improvement in spirometry that does in fact exist, the difference is less than 10%. According to Nickerson, the percentage of predicted change within subjects required for significance lies between 13% and 23%. 18 Therefore the difference that our data might fail to detect is of no clinical consequence, and our conclusion of no difference between mechanical and manual percussion is clinically significant. The effiCacy of mechanical percussors during prolonged outpatient chest physiotherapy for patients with cystic fibrosis was not addressed by this study. The advantages of studying the question in the inpatient population (enforced
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compliance and sequential spirometry) would be difficult to duplicate in an outpatient study. The decision to study hospitalized patients with cystic fibrosis caused selection of patients with more severe lung disease. This is not without clinical relevance because many centers do not initiate chest percussion until their patients have signs of pulmonary involvement. The extrapolation of our results to the outpatient setting is hypothetical but not without support. Reisman et al. 1 demonstrated the benefits of chest percussion with either manual or mechanical percussion. Review of their data did not demonstrate a difference between manual and mechanical percussion (personal communication, 1990). However, their study was not designed to differentiate between the two. The definitive answer to the question of relative efficacy of mechanical and manual percussion for the longterm care of cystic fibrosis could be obtained o n l y by a long-term comparative study. We have confirmed the therapeutic equivalence of manual and mechanical chest percussion when correctly applied. Patients may be encouraged to select a percussion technique based on their personal perceptions of comfort, convenience, and benefit. The hospital setting of this study precludes any conclusions about compliance with mechanical percussion. We assume that preferential selection will improve compliance and therefore optimize therapeutic efficacy of chest percussion. REFERENCES
1. Reisman J J, Rivington-Law B, Corey M, et al. Role of conventional physiotherapy in cystic fibrosis. J PEDIATR1988; 113:632-6. 2. Patterson JM, Budd J, Goetz D, Warwick WJ. Family correlates of a 10-year pulmonary health trend in cystiC fibrosis. Pediatrics 1993;91:383-9. 3. Maxwell M, Redmond A. Comparative tria! Of manual and mechanical percussion technique with gravity-assisted bronchial drainage in patients with cystic fibrosis. Arch Dis Child 1979;54:542-4.
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4, Hartsell MB. Chest physiotherapy and mechanical vibration. J Pediatr Nurs 1987;2:135-7. 5. Rossman D, Waldes R, Sampson D, Newhouse M. Effect of chest physiotherapy on the removal of mucus in patients with cystic fibrosis. Am Rev Respir Dis 1982;126:131-5. 6. Desmond KJ, Schwenk F, Thomas E, Beaudry PH, Coates AL. Immediate and long-term effects of chest physiotherapy in patients with cystic fibrosis. J PEDIATR1983;103:538-42. 7. Radford R, Barutt J, Billingsley JG, Hiss W, Lawson WH, Willich W. A rational basis for percussion-augmented mucociliary clearance. Respir Care 1982;27:556-63. 8. Flower KA, Eden RI, Lomax L, et al. New mechanical aid to physiotherapy in cystic fibrosis. BMJ 1979;2:630-1. 9. Gardner RM, Baker CD, Broennle AM Jr, et al. ATS [American Thoracic Society] statement. (Snowbird workshop on standardization of spirometry. ) Am Rev Respir Dis 1979; 119:831-8. 10. Knudson R J, Slatin RC, Lebowitz MD, Burrows B. The maximal expiratory flow-volume curve. Am Rev Respir Dis 1976;112:5874600. 11. Taussig LM, Kattwinkel J, Friedewald WT, et al. A new prognostic score and clinical evaluation system for cystic fibrosis. J PEDIATR1973;82:380-90. 12. Smith AL, Redding G, Doershuk C, et al. Sputum changes associated with therapy for endobronchial exacerbation in cystic fibrosis. J PEDIATR1988;112:547-54. 13. Redding G J, Restuccia R, Cotton EK, Brooks JG. Serial changes in pulmonary functions in children hospitalized with cystic fibrosis. Am Rev Respir Dis 1982;126:31-6. 14. Cerny F J, Cropp JA, Bye MR. Hospital therapy improves exercise tolerance and lung function in cystic fibrosis. Am J Dis Child 1984;138:261-5. 15. Cohen J. Statistical power analysis for the behavioral sciences. Hillsdale: Lawrence Erlbaum Associates, 1988:19-74. 16. Daniel WW. Biostatistics: a foundation for analysis in the health sciences. New York: John Wiley & Sons, 1991. 17. Glantz SA. Primer of biostatistics. New york: McGraw-Hill, 1992. 18. Nickerson BG, Lemen RJI Gerdes CB, Wegmann M J, Robertson G. Within-subject variability and percent change for significance of spirometry in normal subjects and in patients with cystic fibrosis. Am Rev Respir Dis 1980;122:859-66.
We compared the efficacy of manual and mechanical chest percussion during hospitalization for acute exacerbations of cystic fibrosis by evaluating changes in spirometry values. Fifty-one participants were randomly assigned to receive manual or mechanical chest percussion three times a day. Twenty-two participated during one subsequent admission and were assigned to the opposite form of chest percussion. The two groups were equal in severity of illness (mean National Institutes of Health score [_+SEM]: manual = 66.7 ± 2.2; mechanical = 65.8 ± 2.2; p = not significant). Mean improvement in forced expiratory volume at I second, forced vital capacity, and forced expiratory flow between 25% and 75% of forced vital capacity (±SEM) for manual percussion was 32.6% ± 7%, 27.2% ± 5%, and 38.1% ± 10%, and for mechanical percussion was 28.5% ± 4%, 28.7% ± 4%, and 25.1% ± 8%, respectively; p = not significant. Our participants did not prefer mechanical chest percussion. Although equal efficacy of outpatient therapy remains to be proved, this study suggests that patients can be encouraged to use the form of chest percussion that they prefer. (J PEDIATR1994;124:250-4)
The combination of chest percussion and postural drainage reduces the rate of deterioration in lung function in patients with cystic fibrosis.i, 2 Unfortunately, compliance with daily percussion and postural drainage is less than optimal because percussion can be time-consuming and uncomfortable, and it requires assistance. It has been suggested that mechanical percussion provides greater comfort and independence than manual percussion, thus improving patient compliance.3, 4 Many centers use both manual and mechanical percussion 1, 3, 4; others, including our own, have taught that manual percussion is superior. No reports support either the equivalence of manual and mechanical percussion Submitted for publication March 23, 1992; accepted Oct. 1, 1993. Reprint requests: Martin L. Bauer, MD, Children's Mercy Hospital, 2401 Gillham Rd., Kansas City, MO 64108. Copyright © 1994 by Mosby-Year Book, Inc. 0022-3476/94 $3.00 + 0 9/20/51812
250
or the superiority of one over the other. Furthermore, no report objectively assesses patient preference or compliance with mechanical percussion. Three studies have attempted to compare manual and mechanical percussion in cystic fibrosis,3-5 but they evaluated the effect of only one session of each. The report by Desmond et al. 6 indicates that, rather than comparing the effect of the two techniques, these articles more accurately FEV1
Forced expiratory volume at 1 second
describe patient compliance during the 3 weeks before the study. To determine whether manual percussion and mechanical chest percussion are equivalent, we compared the therapeutic efficacy of manual percussion and mechanical percussion in patients hospitalized for an acute exacerbation of cystic fibrosis by measuring spirometry, weight gain, and
The Journal of Pediatrics Volume 124, Number 2
duration of hospitalization. We also evaluated patient preference by questionnaire and interview. METHODS
Before initiation of this study, a postcard questionnaire was mailed to every patient of our cystic fibrosis center. The patients were asked to circle yes or no in response to the following two questions: Have you ever used a mechanical percussor? Do you presently use a mechanical percussor? They could check a box for "manual percussion," "mechanical percussion," or "no preference" in response to the question, Do you hav e a preference? Space was provided to respond to a request: Please explain your preference or lack of preference. Several months after the returned postcard questionnaires were evaluated, a letter describing this study was mailed to each patient registered with our cystic fibrosis center. The study was further explained and questions were answered during routine visits. From August 1989 through February 1992, at the time of admission for an acute exacerbation of cystic fibrosis or as soon after admission as possible, all patients were screened for their ability to cooperate with spirometrY and willingness to participate in the study. Those who could perform adequate spirometry and who signed consent forms were randomly assigned to receive either manual or mechanical percussion for the entire hospitalization. A participant admitted to th e hospital twice during the course of the study was allowed to participate a second time but was nonrandomly assigned to receive the form of percussion not received during the first participation. No patient was allowed to participate more than twice. On entrance into the study, patients were interviewed by the principal investigator to obtain baseline clinical and historical information and were asked about their use of mechanical and manual percussion and their preference, as described above. Percussion was performed three times a day by hospitalemployed respiratory care practitioners who recorded each session in the hospital chart, noting time, positions, cough and secretion assessments, oximetry readings, and complications. Each percussion session was performed i n two upright positions (upper portion of the back and upper anterior portion of the chest), four flat positions (mid portion of the chest, anterior portion of the back, left and right sides), and four Trendelenburg positions (lower portion of the chest, anterior portion of the back, left and right sides). Total duration of each percussion session was approximately 30 minutes. Manual percussion was performed by practitioners with cupped hands. Mechanical percussion was provided by practitioners with a Vibracare percussor (General
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251
Physiotherapy, St. Louis, Mo.) or a model 9000 percussor (Puritan-Bennett Corp., Overland Park, Kan.) at a frequency of 25 to 35 Hz, 7 with pressure to the chest wall sufficient to PrOduce vibration of the participant's voice. 8 Registered respiratory car e practitioners trained in pediatric pulmonary function studies and dedicated to the pulmonary function laboratory supervised all spirometry, which was performed in accordance with the American Thoracic Society guidelines. 9 Participants performed spirometry on a CDX Spiro automate d spirometer (model 110; CDX Corp., Aurora, Colo.) in the morning on Mondays, Wednesdays, and Fridays during hospitalization. Most participants also performed spir0metrY on the day of admission. Spirometry values were recorded as the percentage of the predicted value; predicted values were calculated according to the formulas of Knudson et al. 1° Participants were weighed daily. National Institutes of Health scores 11 were determined on the date of admission. All other diagnostic and therapeutic interventions were determined at the discretion of the attending physician, a pediatric pulmonoiogist on staff at Children's Hospital of Alabama. Medication given to each participant during each admission was documented and tabulated by chart review after discharge from the hospital. We attempted to contact all participants by telephone after discharge from the hospital to ask whether they had a preference between manual and mechanical percussion and, if so, on what factors the preference was based. Statistical analysis. Our study was designed to provide a power of 90% to detect a 10% difference in improvement in forced expiratory volume at 1 second between the two groups, assuming an effect size of one or greater for a twosided test of significance, a standard deviation in FEV1 of 6% of the predicted value (extrapolated from reported spirometry values in hospitalized patients with cystic fibrosisl2"14), andan a of 0.05.15 Improvement in spirometry was calculated by the following formula: 100 * (Discharge spirometry - Admission spirometry) Admission spirometry and expressed as the percentage o f improvement. Comparisons between groups were analyzed by unpaired t test on clinical data, paired t test on percentage of improvement, and linear regression analysis of spirometry values. Twotailed Fisher Exact Test was applied to the comparison of medications between groups. 16, 17 Approval. The study protocol was approved by the institutional review board of the University of Alabama Birmingham and Children's Hospital of Alabama before initiation of the study. All participants gave informed consent.
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Table I. Clinical features
n All participants 36 37 Crossover group 22 22
Treatment group (percussion)
NIH score
Hospital days
Age (yr)
Sex (M/F)
Manual Mechanical
66.7 ± 2.2 65.8 + 2.2
12.5 ± 0.5 11.4 ___0.5
17.0 ± 1.4 15.9 ± 1.4
18/18 19/18
Manual Mechanical
63.5 + 2.7 63.8 ___2.7
12.4 _+ 0.6 11.0 _+ 0.5
17.5 --- 2.1 17.5 + 2.0
12/10 12/10
Values are expressed as mean _+ SEM. p = not significant for all comparisons. NIH, National Institutes of Health.
Table II. Effect of severity of illness on pulmonary function improvement NIH score
FEVI
FVC
FEF25.75
Table III. Linear regression analysis of spirometry during hospitalization n
>50
28 ± 4
27 ± 3
26 ± 7
62
--<50
47 ± 10
31 ± 7
60 + 15
11
Values (except NIH scores) are expressed as percentage (_+SEM) of improvementbetweenadmission and dischargevalues,p > 0.05 for all comparisons. NIH, National Institutes of Health; FVC, forced vital capacity; FEF2~-75, forced expiratory flow between 25% and 75% of FVC. RESULTS Between Aug. 9, 1989, and Feb. 9, 1992, there were 246 admissions for cystic fibrosis to Children's Hospital of Alabama; 189 of these admissions were of 66 patients more than 6 years of age. O f these 66 patients, 54 agreed to participate in this study. Three dropped out: one was dismissed after only 2 days of hospitalization, one was not compliant with the protocol, and one complained that manual percussion was painful. Therefore 51 patients participated fully in the study, providing the data for analysis. Of the 51 participants, 27 were admitted a second time during the study and agreed to participate in the opposite arm of the study. O f these 27 participants, five were excluded: two were dismissed early, one was noncompliant, and two, assigned to mechanical percussion, requested to return to manual percussion because of personal preference. Therefore 22 patients (crossover group) participated fully in both arms of the study. A total of 37 participants received mechanical percussion and 36 received manual percussion. There was no difference in National Institutes of Health scores or duration of hospitalization between the groups, either in the total population of participants or in the crossover group. Sex and age distributions were equivalent (Table I). There was no difference between groups in medication given during hospitalization (data not shown). Patients with more severe manifestations of cystic fibrosis, as defined by lower Na-
Spirometry value FEV1 FVC FEF25-75
Treatment group (percussion) Manual Mechanical Manual Mechanical Manual Mechanical
Baseline
Rate of change
42.5 39.5 62.0 59.8 20.8 18.0
1.0 1.3 1.3 2.0 0.6 0.6
+ 3.4 + 2.7 _+ 3.2 _+ 3.2 + 3.5 ± 2.3
+ 0.2 ± 0.2 +_ 0.2 _+ 0.3 ___0.2 + 0.2
Comparison of mean difference( _+SEM) in rate of improvementwith time. FEVb FVC, and FEF25_75baselinevalues are expressedas percentageof the predictedvalue.Rate of change is rate of improvementin spirometryper day of hospitalization, p = not significant for all comparisons. FVC, Forced vital capacity; FEF25-zs,forced expiratory flowbetween 25% and 75% FVC.
tional Institutes of Health scores, had greater improvement in lung function during hospitalization (Table II). There was no difference in weight gain during hospitalization between the groups. In the total group, mean weight gain ( + S E M ) was 1.0 ___ 0.2 kg and 0.9 + 0.2) kg for manual and mechanical percussion groups, respectively. In the crossover group, respective weight gain was 0.8 + 0.4 kg and 1.0 _+ 0.2 kg. Linear regression analysis of spirometry values during hospitalization revealed no difference between manual and mechanical percussion (Table III). A comparison of improvement in spirometry values between admission and discharge revealed no difference between manual and mechanical percussion (Table IV). This remained true when we analyzed the crossover group separately. Prestudy questionnaire cards were sent to all 168 patients in our registry in July 1989. Fifty-seven patients responded; 16% preferred mechanical percussion, 3 3% preferred manual percussion, and 51% either had no preference or could not compare the two because they had not used mechanical percussion. Three patients claimed that they had never used a mechanical percussor but preferred mechanical percus-
The Journal of Pediatrics Volume 124, Number 2
sion: two thought it sounded as though mechanical percussion would work better, and one who did not receive assistance from any caregiver thought that a mechanical percussor would be helpful. Of the 21 respondents who had ever used a mechanical percussor, 29% preferred mechanical percussion, 48% preferred manual percussion, and 24% had no preference. Seventeen of the respondents were using a mechanical percussor for at least some of their therapy at the time of their response. We obtained follow-up telephone responses from 38 of the 51 participants. Before participation, 26% preferred mechanical percussion, 37% preferred manual percussion, and 37% had no preference or were unable to make a comparison because they had never used a mechanical percussor. After participation, 47% preferred mechanical percussion, 26% preferred manual percussion, and 26% had no preference. Of the 28 respondents who received mechanical percussion during participation in the study, 57% preferred mechanical percussion, 11% preferred manual percussion, and 32% had no preference. DISCUSSION As a group, our patients did not report a preference for mechanical percussors. This finding conflicts with suggestions that the mechanical percussor is preferred by patients.3, 4 Before the study, the patients in our practice were told that manual percussion was preferable to mechanical percussion, so it is not surprising that only 16% of our patients expressed preference for mechanical percussion at that time. After completion of this study, the availability of mechanical percussion was considered advantageous by almost half of our patients with cystic fibrosis. This represents a significant change in perception. On the other hand, only slightly more than half of our participants who experienced mechanical percussion preferred mechanical percussion after the study, indicating that although experience with the percussor was favorable, it was not overwhelmingly so. Only three patients dropped out of the study because of dissatisfaction with the mechanical percussor, one because mechanical percussion was painful, and two because of perceived lack of benefit. These data do not support a general preference for one form of percussion over the other. Rather, preference is subject to significant individual variability and probably depends on a combination of perceived comfort, convenience, and benefit. The observed change in patient perception of the value of mechanical percussion might have been either the result of objective evaluations by patients who had previously avoided mechanical percussion because of advice from physicians in our group or the result of the change in attitude of the center's physicians and staff concerning the use of mechanical percussion.
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Table IV. Improvement in spirometry
n
Treatment group (percussion)
FEV1
FVC
FEF25.7s
All participants 36 Manual 32.6 ___7 27.2 _+ 5 38.1 _+ 10 37 Mechanical 28.5 + 4 28.7 + 4 25.1 ~ 8 Crossover group 22 Manual 35.6 ___9 32.4 + 6 38.1 _+ 14 22 Mechanical 30.3 _+ 6 27.5 + 5 33.4 _+ 11 Change in spirometryvaluebetweenadmissionand dischargeexpressedas percentage (_+SEM) of increaseabovebaseline,p = not significantfor all comparisons. FVC, Forcedvital capacity;FEF2s-75,forcedexpiratoryflowbetween 25% and 75% FVC. The observed improvement in pulmonary function in our patient population is comparable to that reported by Smith et a1.,12 even though our patients were admitted with better lung function and discharged after fewer hospital days than in their study. Improvement in our patients was somewhat less than that reported by Redding et al. 13 and by Cerny et al., 14 but these investigators studied fewer patients with lower lung function on admission and longer hospitalization. The three cited studies conflict in their reports of improvement in pulmonary function when severely ill patients are compared with those who are less sick. Redding et al. 13 demonstrated less improvement in the sicker patients, whereas Smith et alJ 2 and Cerny et alJ 4 demonstrated greater improvement in the sicker patients. Our data agree with the latter finding. Patients with greater severity of illness already have lower function and thus require less absolute improvement to yield a greater percentage of improvement. The fact that our patients were not as ill on admission but demonstrated improvement comparable to that in previous studies suggests that our patients achieved optimal benefit from their hospital treatment, and validates our data base for analysis. We found no significant difference in therapeutic efficacy between mechanical and manual chest percussion in hospitalized patients with cystic fibrosis. Our study design allows us to conclude that, if our data failed to detect a difference in improvement in spirometry that does in fact exist, the difference is less than 10%. According to Nickerson, the percentage of predicted change within subjects required for significance lies between 13% and 23%. 18 Therefore the difference that our data might fail to detect is of no clinical consequence, and our conclusion of no difference between mechanical and manual percussion is clinically significant. The effiCacy of mechanical percussors during prolonged outpatient chest physiotherapy for patients with cystic fibrosis was not addressed by this study. The advantages of studying the question in the inpatient population (enforced
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compliance and sequential spirometry) would be difficult to duplicate in an outpatient study. The decision to study hospitalized patients with cystic fibrosis caused selection of patients with more severe lung disease. This is not without clinical relevance because many centers do not initiate chest percussion until their patients have signs of pulmonary involvement. The extrapolation of our results to the outpatient setting is hypothetical but not without support. Reisman et al. 1 demonstrated the benefits of chest percussion with either manual or mechanical percussion. Review of their data did not demonstrate a difference between manual and mechanical percussion (personal communication, 1990). However, their study was not designed to differentiate between the two. The definitive answer to the question of relative efficacy of mechanical and manual percussion for the longterm care of cystic fibrosis could be obtained o n l y by a long-term comparative study. We have confirmed the therapeutic equivalence of manual and mechanical chest percussion when correctly applied. Patients may be encouraged to select a percussion technique based on their personal perceptions of comfort, convenience, and benefit. The hospital setting of this study precludes any conclusions about compliance with mechanical percussion. We assume that preferential selection will improve compliance and therefore optimize therapeutic efficacy of chest percussion. REFERENCES
1. Reisman J J, Rivington-Law B, Corey M, et al. Role of conventional physiotherapy in cystic fibrosis. J PEDIATR1988; 113:632-6. 2. Patterson JM, Budd J, Goetz D, Warwick WJ. Family correlates of a 10-year pulmonary health trend in cystiC fibrosis. Pediatrics 1993;91:383-9. 3. Maxwell M, Redmond A. Comparative tria! Of manual and mechanical percussion technique with gravity-assisted bronchial drainage in patients with cystic fibrosis. Arch Dis Child 1979;54:542-4.
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4, Hartsell MB. Chest physiotherapy and mechanical vibration. J Pediatr Nurs 1987;2:135-7. 5. Rossman D, Waldes R, Sampson D, Newhouse M. Effect of chest physiotherapy on the removal of mucus in patients with cystic fibrosis. Am Rev Respir Dis 1982;126:131-5. 6. Desmond KJ, Schwenk F, Thomas E, Beaudry PH, Coates AL. Immediate and long-term effects of chest physiotherapy in patients with cystic fibrosis. J PEDIATR1983;103:538-42. 7. Radford R, Barutt J, Billingsley JG, Hiss W, Lawson WH, Willich W. A rational basis for percussion-augmented mucociliary clearance. Respir Care 1982;27:556-63. 8. Flower KA, Eden RI, Lomax L, et al. New mechanical aid to physiotherapy in cystic fibrosis. BMJ 1979;2:630-1. 9. Gardner RM, Baker CD, Broennle AM Jr, et al. ATS [American Thoracic Society] statement. (Snowbird workshop on standardization of spirometry. ) Am Rev Respir Dis 1979; 119:831-8. 10. Knudson R J, Slatin RC, Lebowitz MD, Burrows B. The maximal expiratory flow-volume curve. Am Rev Respir Dis 1976;112:5874600. 11. Taussig LM, Kattwinkel J, Friedewald WT, et al. A new prognostic score and clinical evaluation system for cystic fibrosis. J PEDIATR1973;82:380-90. 12. Smith AL, Redding G, Doershuk C, et al. Sputum changes associated with therapy for endobronchial exacerbation in cystic fibrosis. J PEDIATR1988;112:547-54. 13. Redding G J, Restuccia R, Cotton EK, Brooks JG. Serial changes in pulmonary functions in children hospitalized with cystic fibrosis. Am Rev Respir Dis 1982;126:31-6. 14. Cerny F J, Cropp JA, Bye MR. Hospital therapy improves exercise tolerance and lung function in cystic fibrosis. Am J Dis Child 1984;138:261-5. 15. Cohen J. Statistical power analysis for the behavioral sciences. Hillsdale: Lawrence Erlbaum Associates, 1988:19-74. 16. Daniel WW. Biostatistics: a foundation for analysis in the health sciences. New York: John Wiley & Sons, 1991. 17. Glantz SA. Primer of biostatistics. New york: McGraw-Hill, 1992. 18. Nickerson BG, Lemen RJI Gerdes CB, Wegmann M J, Robertson G. Within-subject variability and percent change for significance of spirometry in normal subjects and in patients with cystic fibrosis. Am Rev Respir Dis 1980;122:859-66.