Relative Effects of Bronchial Drainage and Exercise for In-Hospital Care of Patients with Cystic Fibrosis

Bronchial hygiene therapy is a standard part of the treatment of patients with cys­tic fibrosis (CF). Coughing alone promotes sputum expectoration and is probably the primary effective component of standard bronchial hygiene therapy. The pur­pose of this study was to determine whether substituting regular exercise, which also promotes coughing for two of three daily bronchial hygiene treatments would affect the expected improvements in pulmonary function and exercise response in hospitalized patients with CF. Seventeen patients with CF hospitalized ( length of stay = 130 ± 2.6 days) for an acute exacerbation of their pulmo­nary disease participated in the study. The patients were randomly assigned to either a group that participated in two cycle ergometer exercise sessions and one bronchial hygiene treatment session per day (EX Group[n = 9]) or a group that participated in three bronchial hygiene treatment sessions per day (PD Group [n =8]). Pulmonary functions and responses to a progressive, incremental cycle ergometer exercise test were measured on admission and before discharge. Bron­chial hygiene therapy consisted of postural drainage, in six positions, with chest percussion and vibration. Therapeutic exercise was of moderate intensity and was individually adjusted based on the patient's heart rate and arterial oxygen satura­tion response to the admission exercise test. Coughing was encouraged during and after all treatments. Pulmonary function and exercise response were signifi­cantly improved over the period of hospitalization in both groups; the improve­ments were the same in the two groups. These results indicate that, in some hospi­talized patients with CF, exercise therapy may be substituted for at least part of the standard protocol of bronchial hygiene therapy. [Cerny FJ: Relative effects of bron­chial drainage and exercise for in-hospital care of patients with cystic fibrosis. Phys Ther 69:633-639, 1989]

Key Words: Cystic fibrosis; Pediatrics, evaluation; Percussion; Pulmonary, bron­chial drainage.

Frank J Cerny

Chest physical therapy, including bronchial hygiene techniques consist­ing of postural drainage, chest percus­sion, vibration, forced expiration, and

coughing, has been a standard part of the treatment for children with cystic fibrosis (CF).1-3 The objectives of bronchial hygiene therapy are to

mobilize pulmonary secretions and promote sputum expectoration. Increased short-term sputum expecto­ration and improved lung function have been reported after bronchial hygiene therapy4-11 The patient-parent time and effort required for two to four daily bronchial hygiene sessions often result in noncompli­ance and have led to a search for alternate means of producing the same effects. Studies that have exam­ined the effects of the individual com­ponents of bronchial hygiene therapy suggest that coughing alone may be

F Cerny, PhD, is Assistant Professor, Department of Pediatrics, Division of Pulmonary Disease, Chil­dren's Hospital, 219 Bryant St, Buffalo, NY 14222, and Department of Physical Therapy and Exercise Science, State University of New York at Buffalo, 411 Kimball Tower, Buffalo, NY 14214. Address correspondence to Department of Physical Therapy and Exercise Science, State University of New York at Buffalo, 411 Kimball Tower, Buffalo, NY 14214 (USA).

This study was supported in part by NIH Grants 5R01AM24066 and RR-05493 and by The Buffalo Foundation.

This article was submitted October 12, 1988; was with the author for revision for five weeks, and was accepted March 3, 1989.

Physical Therapy/Volume 69, Number 8/August 1989 633/11

Table. Physical Characteristics of Patients

Groupa

EX (n = 9)

PD (n = 8)

Age (yr)

15.4

15.9

s

4.9

4.9

Height (cm)

149.5

151.6

s

14.6

14.2

Weight (kg)

Admission

35.9 38.4

s

10.5

14.4

Discharge

36.9

39.4

s

11.1

14.6

PFSb

Admission

12.2

14.9

s

1.3

0.9

Discharge s

9.8 1.1

12.3 1.0

the primary effective element in stim­ulating sputum expectoration.12-18

Mellins observed that in many patients exercise induced coughing, suggesting that exercise may be an alternative therapeutic modality for facilitating sputum expectoration in selected patients with lung disease.19

In support of this suggestion, regular physical activity has been shown to result in improvements in lung func­tion in patients with CF.20-24 It is unknown how incorporation of exer­cise into the physical therapy program of patients with CF hospitalized for an acute exacerbation of their lung dis­ease will affect the changes in lung function and exercise capacity occur­ring during the inpatient time period. This report describes the effects of replacing two of three daily bronchial hygiene sessions with vigorous exer­cise on lung function and exercise adaptation in hospitalized patients with CF.

Method

Subjects

Patients in the study were admitted to the hospital for treatment of an acute exacerbation of their pulmonary dis­ease. Admission was based on symp­toms of increased shortness of breath, coughing, and sputum production and decreased lung function. Subjects who were able to perform pulmonary

function tests and who gave written informed consent were randomly assigned to either a group that partici­pated in two cycle ergometer exercise sessions and one bronchial hygiene treatment session per day (EX Group [n = 9]) or a group that participated in three bronchial hygiene treatment sessions per day (PD Group [n = 8]). No attempt was made to match patients for disease severity. Patient characteristics are shown in the Table. Discharge was based on improvement in one or more of the following: pul­monary function test results, chest radiograph, shortness of breath, and elimination of fever.

Procedure

Pulmonary function tests. Patients performed pulmonary function and exercise tests on the morning after admission and on the morning of dis­charge. The first pulmonary function test was performed two hours after the first bronchial hygiene treatment. All patients had previously performed both pulmonary function and exercise tests on multiple occasions. Forced vital capacity (FVC), expiratory reserve volume (ERV), inspiratory capacity (IC), forced expiratory volume in one second (FEV1), and forced expiratory flow between 25% and 75% of FVC (FEF25%_75%) were measured by spirometry; functional residual capac­ity (FRC) and airway resistance (Raw)

were measured by body plethys­mography.25,26 Residual volume (RV = FRC - ERV), total lung capacity (TLC = FRC + IC), and specific air­ways conductance (SGAW = 1/Raw x FRC-1) were calculated. Percentage of arterial oxygen saturation (Sao2) was estimated with an ear oximeter.*

Pulmonary functions, with the excep­tion of Sao2, were expressed as a per­centage of predicted value.2728 In addition, a pulmonary function score (PFS), based on the deviation from the predicted values for six pulmo­nary functions tests (FVC, FEV1, FEF25%_75%, RV, SGAW, and Sao2), was calculated.29 Test results within two standard deviations of the expected value received a score of 0. Scores of 1,2, and 3 were assigned for values greater than two, three, and four stan­dard deviations from the normal mean, respectively. A total PFS of 0 to <3 was considered normal, and scores of 3 to 7, 8 to 12, and 12 to 18 were indicative of mild, moderate, and severe lung dysfunction, respec­tively. This score has been shown to correlate well with other clinical scores29 and is used as an indicator of general lung function.

Exercise test The exercise test was performed on a cycle ergometer.†

The initial load of 0.3 W/kg was increased by 0.3 W/kg every 2 min­utes. Exercise was stopped when the subjects could no longer continue despite encouragement or when Sao2 had decreased by >15% or to less than 75% of the baseline level. Arte­rial oxygen saturation, electrocardio-

aEX Group participated in two cycle ergometer exercise sessions and one bronchial hygiene treatment session per day; PD Group participated in three bronchial drainage treatment sessions per day, except for one patient who received four treatments per day. bPFS = pulmonary function score.26

*Hewlett-Packard Co, Waltham Div, 175 Wyman St, Waltham, MA 02154-9030. †Quinton Instrument Co, 2121 Terry Ave, Seattle, WA 98121.

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graphic activity, and heart rate (HR) were monitored continuously. Sub­jects breathed from a low-dead space (50 mL), one-way valve to allow mea­surement of exhaled minute ventila­tion (VE) in a Tissot gasometer for the last 30 seconds of each work load.

Treatment All patients were treated similarly with intravenous antibiotics, inhaled bronchodilators, pancreatic enzymes, and water-soluble vitamins A and E and multivitamin prepara­tions. Physical therapy was given between 8 and 9:30 AM, 3 and 4:30 PM, and 7 and 9 PM. The PD Group received postural drainage with chest percussion and vibration in six posi­tions for 20 to 40 minutes three times daily, with the exception of one patient who received two afternoon treatments for a total of four treat­ments per day. The postural drainage was preceded by inhaled β2-receptor agonist bronchodilators. The EX Group exercised during the first two sessions and received postural drain­age during the third session. Cough­ing was encouraged during and after all therapy sessions. Coughs were counted for 15 minutes following each therapy session.

Exercise therapy was performed on a cycle ergometer. The ear oximeter was worn at all times. Exercise inten­sity was adjusted to attain a target HR established as a percentage of the heart rate reserve (HRR = peak exer­cise HR - resting HR)30 so that target HR = HRR x percentage desired + resting HR Resting HR was measured in the laboratory after the patient had been sitting quietly for 10 minutes. Work loads in the first two days were set to elicit a HR of 25% to 40% of the HRR. This was a level that could be tolerated for 5 to 10 minutes and would not result in arterial oxygen desaturation (Sao2 = >2%), except in two patients who received supple­mental oxygen at a level to maintain Sao2 above 90% on Days 1 and 2. After 3 to 4 days, all subjects were able to exercise at a work level that elicited a HR of at least 40% of their peak HRR. From Day 4 to discharge, exercise time was increased to a tar­get duration of 15 to 20 minutes. By

the end of the hospitalization, each patient was able to work at an inten­sity of between 45% and 65% of the HRR.

To determine the immediate effects of exercise or bronchial hygiene therapy on pulmonary functions, spirometry was performed each day immediately before the morning treatment, 15 minutes after the morning treatment, and every hour for 5 hours after the morning treatment. Daily sputum vol­ume expectorated was determined by measuring and summing the amounts of sputum accumulated during the following time intervals: from the time of awakening (7-8 AM) to the beginning of treatment, during and for one-half hour following treatment, from 9:30 to 11:30 AM, from 11:30 AM to 2:30 PM, from 2:30 to 8:30 PM, and from 8:30 PM to wake-up. Sputum volume, wet weight, and dry weight (after 4 days of drying in an oven) were recorded and expressed in units per hour.

Data Analysis

Significance of within-group changes in each measurement of pulmonary function and exercise adaptation, from admission to discharge, was determined using paired Student's t tests. In addition, to determine whether the extent of these changes was different between the groups, a Delta value for each pulmonary func­tion test and measure of exercise adaptation was calculated (Delta value = discharge value - admission value) and averaged for each group. Between-group comparisons of these Delta values were made using the unpaired Student's t test. Between-group statistical comparisons for the pulmonary function changes over the five hours following physical therapy were made on Days 1 and 7 using an analysis of variance for repeated measures.31 Significance was accepted at the .05 level.

Results

The mean duration of the hospitaliza­tion was 13 days (s = 3) for the EX Group and 13 days (s = 2.6) for the

PD Group. Results of the pulmonary function tests on admission and at discharge are shown in Figure 1. There were no PFS differences between the EX and PD Groups at admission or discharge. Compared with the EX Group, the admission FEV1 and FEF25%_75% were signifi­cantly lower in the PD Group (p < .05). The PFS, FVC, and FEF1 improved significantly in both groups, whereas FEF25%_75% improved only in the PD Group. Within-group changes in the other pulmonary function tests were not statistically significant. There were no significant differences in the Delta values, indicating that the extent of the changes in all tests was the same for both groups.

Results of the exercise tests performed on admission and at dis­charge are shown in Figure 2. On admission, no significant between-group differences were observed in any of the exercise variables. Peak load (p < .02) and peak HR (p < .05) improved from admission to discharge in both groups. To adjust peak VE and peak HR values for potential changes in the load at which they were attained, the ratios for peak VE to peak load and peak HR to peak load were calculated and compared. The peak HR-to-peak load ratio improved (p < .05) only in the EX Group. The between-group compari­son of admission to discharge Delta values revealed no significant differences.

All postural drainage treatments were completed as required for the study, and 96% of the scheduled exercise therapy sessions were completed. Both treatments induced a productive cough and an equal number of coughs. An acute (15 minutes post-treatment), but not statistically signifi­cant, improvement in pulmonary functions, which lasted over the 5-hour follow-up period, was noted after 85% of the treatment sessions (Fig. 3). These trends were the same on Day 1, the first full day of treat­ment, as on Day 7 of the treatment protocol, with no significant differ­ences between groups (Fig. 3). There were no differences in 24-hour spu-

Physical Therapy/Volume 69, Number 8/August 1989 635/13

turn volume and dry weight; the greatest volume was collected after the morning treatment, with no differ­ences between the PD and EX Groups.

Discussion

Some form of bronchial hygiene has been part of the treatment program for patients with CF since 1959 when Doyle suggested that it may enhance mobilization and expectoration of sputum.32 Exercise may have similar pulmonary hygiene effects.19 In this study, hospitalized patients who sub­stituted exercise for two of three bronchial hygiene treatments showed improvements in lung function and exercise adaptation comparable to patients who received the usual three daily bronchial hygiene treatments.

Comparisons of the PD and EX Groups are valid only if clinical status was similar at admission. Although between-group differences in admis­sion FEV1 and FEF25%_75% were observed, clinical status, as indicated by the PFS,29 was the same in both groups. Nickerson et al have shown that individual pulmonary function tests in patients with CF are signifi­cantly more variable than in healthy subjects such that the assessment of pulmonary status on the basis of a single test could be artifactual.33 For this reason, a combination of mea­sures, such as the PFS, can be a more reliable indicator of clinical status.34

Also supporting the suggestion that the groups in this study were similar in status is the fact that published reports of improvement in pulmonary function35"37 and exercise adaptation37

during a hospitalization and in pul­monary function immediately follow­ing treatment5,6,8,11 were qualitatively the same as those in this study for either group.

It could be argued that the equivalent changes in lung function in the EX Group were due to the single evening bronchial hygiene treatment. Des­mond et al reported that a single bronchial hygiene treatment given after a three-week no-treatment period resulted in significant

Fig. 1. Means and standard deviations of changes (in percentage of predicted value) in lung function during hospitalization in patients with cystic fibrosis. The PD Group (n = 8) received three bronchial drainage treatments per day, except for one patient who received four treatments per day; the EX Group (n = 9) participated in two cycle ergometry exercise sessions and one bronchial hygiene treatment session per day. Delta shows change for each group over period of hospitalization. (FVC —forced vital capacity; FEV1 = forced expiratory volume in one second; FEF25%_75% = forced expira­tory flow between 25% and 75% of FVC; FRC = functional residual capacity.)

increases in FVC and rate of airflow at 60% of TLC (Vmax 60 TLC), but not FEF25%_75%.11 They also reported that FVC and Vmax 60 TLC, but not FEF25%_75%, after this single treatment were "similar" to values measured prior to cessation of treatment. It is unclear from these results as to what the effects of a single, daily treatment might be. The sputum data from the present study do not support the idea that the single evening bronchial hygiene session could account for the similarity in the groups. Sputum vol­umes collected in this study were greatest after the first treatment in the morning, regardless of whether the treatment was postural drainage or exercise, and daily volumes were the same for both groups. These data would suggest that a single bronchial hygiene treatment, although having some positive effect on lung function, would not account for the lack of dif­ferences between the groups.

Early studies suggested that lung func­tion was improved after postural drainage.4-6,9,13 More recent studies showed no short-term changes in pul­monary function in patients with chronic obstructive pulmonary dis­ease (COPD)8 or CF.11 It is difficult to compare these studies because a vari­ety of pulmonary function tests were used for evaluation, the severity of disease was dissimilar between stud­ies, and the patients were not homoge­neous within studies. Desmond et al's study emphasizes the effect that previ­ous therapy history might have on the effectiveness of the therapy session being evaluated.11

Studies examining the effectiveness of bronchial hygiene therapy have con­firmed an enhanced sputum expecto­ration or rate of mucus clearance as a result of treatment.4,10-18 Others have reported that coughing was the pri­mary effective component of bron-

14/636 Physical Therapy/Volume 69, Number 8/August 1989

chial hygiene therapy in patients with CF15,17 and COPD.18 Because coughing was common to both types of therapy in this investigation, the similarity of the five-hour posttreatment response in pulmonary function would support the suggestion that coughing is the important element in bronchial hygiene therapy, regardless of how it is elicited.

Regular exercise has been shown to result in improvements in lung func­tion in nonhospitalized patients with CP. 20-24 These improvements were attributed to ventilatory muscle train­ing but may also be explained, in part, by exercise-induced coughing or acceleration of ciliary mucus clearing.38 This suggestion is in agree­ment with Oldenberg et al,18 who showed that exercise was more effec­tive than postural drainage but less effective than directed coughing in the removal of sputum. The EX Group did not receive bronchodilator therapy before the exercise therapy session. It is unknown how pretreat-ment with bronchodilators affects the effectiveness of subsequent standard bronchial hygiene treatments, and therefore this issue cannot be addressed.

Although the EX Group in this study did show greater improvement in several exercise variables than the PD Group, these changes were small. The short time of training (less than 13 days) and the low level of exercise in the first seven days after admission were below those levels required to elicit a significant conditioning effect.30

Conclusion

Substitution of exercise treatments for two of three daily bronchial hygiene treatment sessions over a nearly two-week hospitalization in this study pro­duced similar benefits in lung func­tion and exercise capacity, suggesting that postural drainage and exercise were equally effective in promoting

Fig. 2 . Means and standard deviations of changes in measures of exercise adapta­tion during hospitalization inpatients with cystic fibrosis. The PD Group (n = 8) received three bronchial drainage treatments per day, except for one patient who received four treatments per day; the EX Group (n = 9) participated in two cycle ergo-meter exercise sessions and one bronchial hygiene treatment session per day. Delta shows change for each group over period of hospitalization. (VE = exhaled minute ven­tilation; HR = heart rate.)

pulmonary hygiene. This study made no attempt to isolate the effects of coughing alone on lung function or exercise response over the period of hospitalization. In view of the avail­able evidence, it is suggested that under all conditions where sputum expectoration should be promoted, coughing must be encouraged. Because exercise can be carried out only when patients feel reasonably well, standard bronchial hygiene or other methods of inducing coughing may be required to promote sputum expectoration under certain condi­tions. This study found no negative effects of exercise therapy performed by inpatients. A limited, individualized exercise program offers an opportu­nity for patients with CF to improve their functional exercise capacity and lung function with no apparent nega­

tive consequences. In selected inpa­tients, exercise should be considered an adjunct to, or substitute for, tradi­tional physical therapy. Guidelines for exercise testing and exercise prescrip­tion for patients with CF are available from either the Cystic Fibrosis Foundation* or the author.

Acknowledgments

I acknowledge the support of Dr GJA Cropp and the technical assistance of Pat Dolan.

References

1 Guide to the Diagnosis and Management of Cystic Fibrosis. Atlanta, GA, Cystic Fibrosis Foundation, 1971 2 Rochester DF, Goldberg SK: Techniques of respiratory physical therapy. Am Rev Respir Dis 122:133-146, 1980 3 Tecklin JS: Physical therapy for children with chronic lung disease. Phys Ther 61:1774-1782, 1981 4 Lorin ML, Denning CR: Evaluation of pos­tural drainage by measurement of sputum vol-‡Cystic Fibrosis Foundation, 6931 Arlington Rd, Bethesda, MD 20814.

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ume and consistency. Am J Phys Med 50:215-219, 1971 5 Motoyama EK: Assessment of lower airway obstruction in cystic fibrosis. In Mangos JA, Talamo RC (eds): Fundamental Problems of Cystic Fibrosis and Related Disorders. New York, NY, Intercontinental Medical Book Corp, 1973, pp 335-343 6 TecklinJS, Holsclaw DS: Evaluation of bron­chial drainage in patients with cystic fibrosis. Phys Ther 55:1081-1084, 1975 7 Holsclaw DS, Tecklin JS: A critical evaluation of bronchial hygiene in pediatric pulmonary disease. Pediatr Ann 6:550-556, 1977 8 Newton DAG, Stephenson A: Effect of phys­iotherapy on pulmonary function. Lancet 2:228-230, 1978 9 Feldman J, Traver GA, Taussig LM: Maximal expiratory flows after postural drainage. Am Rev Respir Dis 119:239-245, 1979 10 Bateman JRM, Newman SP, Daunt KM, et al: Regional lung clearance of excessive bron­chial secretions during chest physiotherapy in patients with stable chronic airways obstruc­tion. Lancet 1:294-297, 1979 11 Desmond KJ, Schwenk WF, Thomas E, et al: Immediate and long-term effects of chest physiotherapy in patients with cystic fibrosis. J Pediatr 103:538-542, 1983 12 Denton R: Bronchial secretions in cystic fibrosis: The effects of treatment with mechani­cal percussion vibration. Am Rev Respir Dis 86:41-48, 1962 13 Wong JW, Keens TG, Wannamaker EM, et al: The effects of gravity on tracheal mucus transport rates in normal subjects and in patients with cystic fibrosis. Pediatrics 60:146-152, 1977 14 Pryor JA, Webber BA, Hodson ME, et al: Evaluation of the forced expiration technique as an adjunct to postural drainage in treatment of cystic fibrosis. Br Med J 2:417-418, 1979 15 DeBoeck C, Zinman R: Cough versus chest physiotherapy. Am Rev Respir Dis 129:182-184, 1984 16 Pryor JA, Parker RA, Webber BA: A compar­ison of mechanical and manual percussion as adjuncts to postural drainage in the treatment of cystic fibrosis in adolescents and adults. Physiotherapy 67:140-141, 1981 17 Rossman CM, Waldes R, Sampson D, et al: Effect of chest physiotherapy on the removal of mucous in patients with cystic fibrosis. Am Rev Respir Dis 126:131-135, 1982 18 Oldenberg FA, Dolovich MB, Montgomery JM, et al: Effects of postural drainage, exercise and cough on mucus clearance in chronic bronchitis. Am Rev Respir Dis 120:739-745, 1979 19 Mellins RB: Pulmonary physiotherapy in the pediatric age group. Am Rev Respir Dis 110(Suppl 2):137-142, 1974 20 Zach MS, Purrer B, Oberwaldner B: Effect of swimming on forced expiration and sputum clearance in cystic fibrosis. Lancet 2:1201-1203, 1981 21 Zach MS, Oberwaldner B, Hausler F: Cystic fibrosis: Physical exercise versus chest physio­therapy. Arch Dis Child 57:587-589, 1982 22 Blomquist M, Freyschuss U, Wiman L-G, et al: Physical activity and self treatment in cystic fibrosis. Arch Dis Child 61:362-367, 1986 23 Andreasson B, Jonson B, Kornfalt R, et al: Long-term effects of physical exercise on work-

Fig. 3 . Changes (in percentage of amount recorded on admission) in forced vital capacity (FVC), forced expiratory volume in one second (FEV1)/FVC, and forced expira­tory flow between 25% and 75% of FVC (FEF25%_75%). The PD Group (n = 8) received three bronchial drainage treatments per day, except for one patient who received four treatments per day; the EX Group (n = 9) participated in two cycle ergometer exercise sessions and one bronchial hygiene treatment session per day. Measures of lung func­tion were assessed immediately before morning treatment, 15 minutes after morning treatment, and at 1-hour intervals for 5 hours after morning treatment Data presented were obtained on first full day of treatment (solid line) and on seventh day after hospi­tal admission (dashed line).

ing capacity and pulmonary function in cystic fibrosis. Acta Paediatr Scand 76:70-75, 1987 24 Orenstein DM, Franklin BA, Doershuk CF, et al: Exercise conditioning and cardio­pulmonary fitness in cystic fibrosis: The effects of a three-month supervised running program. Chest 80:392-398, 1981 25 DuBois AB, Botelho SV, Bedell GN, et al: A rapid plethysmographic method for measuring thoracic gas volume: A comparison study with a nitrogen method for measuring functional residual capacity in normal subjects. J Clin Invest 35:322-326, 1956 26 DuBois AB, Botelho SV, Comroe JH: A new method for measuring airway resistance in man using a body plethysmograph: Values in

normal subjects and in patients with respira­tory disease. J Clin Invest 35:327-335, 1956 27 Polgar G, Promadhat V: Pulmonary Func­tion Testing in Children: Techniques and Stan­dards. Philadelphia, PA, W B Saunders Co, 1971 28 Morris JF: Spirometry in the evaluation of pulmonary function. West J Med 125:110-118, 1976 29 Cropp GJA, Pullano TP, Cerny FJ, et al: Exercise tolerance and cardiorespiratory adjustments at peak work capacity in cystic fibrosis. Am Rev Respir Dis 126:211-216, 1982 30 American College of Sports Medicine: Guidelines for Exercise Testing and Prescrip­tion, ed 3. Philadelphia, PA, Lea & Febiger, 1986

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31 Snedecor GW, Cochran WG: Statistical Methods. Ames, IA, Iowa State University Press, 1967 32 Doyle B: Physical therapy in the treatment of cystic fibrosis. Phys Ther Rev 39:24-27, 1959 33 Nickerson BG, Lemen RJ, Gerdes CB, et al: Within-subject variability and percent change for significance of spirometry in normal sub­jects and in patients with cystic fibrosis. Am Rev Respir Dis 122:859-866,1980

34 Taussig LM, Kattwinkel J, Friedenwald WT, et al: A new prognostic score and clinical eval­uation system for cystic fibrosis. J Pediatr 82:380-388, 1973 35 Strieder DJ, Kahw KT, Simpser M, et al: In-hospital treatment of chronic lung disease in cystic fibrosis: Improved lung function. In: Proceedings of the Seventh International Con­ference on Cystic Fibrosis, 1978, pp 411-415 36 Redding GJ, Restuccia R, Cotton EK, et al: Serial changes in pulmonary function in chil­

dren with cystic fibrosis. Am Rev Respir Dis 126:31-36, 1982 37 Cerny FJ, Cropp GJA, Bye MR: Hospital therapy improves exercise tolerance and lung function in cystic fibrosis. Am J Dis Child 138:261-265, 1984 38 Saketkhoo K, Kaplan I, Sackner MA: Effect of exercise on nasal mucus velocity and nasal airflow resistance in normal subjects. J Appl Physiol: Respirat Environ Exercise Physiol 46:369-371, 1979

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