8 P H Y S I O T H E R A P Y JUNE, 1977 The In flu e n ce o f Posture on the E ffe ctive n e ss o f C oughing C U R R Y , L . I). A N D V A N E E D E N , C * *B.Sc. P hysiotherapy IV , U niversity o f Stellenbosch. “ Physiotherapy procedures, w hen one has a split ste rn u m , can be e x cru ciating ly p a in fu l. K n o w in g fu ll well that the physiotherapy was absolutely necessary (alm ost all patients have some basal atelectasis), that the procedure was scientific, an d that it was for my benefit, and at all tim es co-operating to the utm ost o f m y ab ility . I can recall the m o m e nta ry resentm ent l experienced every tim e the physio­ therapist entered the ward. H o w m u c h m ore m ust this resentm ent b u ild u p in the u ntrain e d m in d , w h ic h c a n n o t appreciate the necessity for this re­ fined, but vitally essential fo rm o f scientific ‘ to rtu re ’.” 1 T he im p o rtan c e o f effective c o u g h in g for the rem oval of secretions, o fte n a most p a in fu l procedure for the post-operative p atie n t, is k n o w n to every physiotherapist. H ow e v e r, very little research has been done on this vital aspect o f chest physiotherapy. M E T H O D T w enty p hysiotherapy students served as subjects for the investigation o f the effectiveness o f co u g h in g in nine different postures. T hey were e x am ine d by a physician an d no clin ica l ab n o rm a litie s were fo u n d w ith respect to the respiratory an d card iov ascu lar systems or the bony tho rax. F u rth e rm o re lu n g fu n c tio n sifting tests were n o rm a l for all subjects. T he positions chosen represent a good cross section o f those fo u n d in nu rsing and in physiotherapy tre atm e nt. T he fo llo w in g postures were selected: 1. S id cly ing , 2. H alf-sideiving w ith bo th arm s an te rio r, 3. H alf-sidelying w ith the lower arm posterior. 4. H alf-lying, legs extended. 5. H alf-lying, legs flexed, 6. Su p ine , legs extended. 7. Su p in e , legs flexed. 8. L o ng sitting am i 9. U prig h t sitting over the side o f the bed. C o u g h m easurem ents were taken fro m an Airflo- m e ter.' These readings are influenced by the flow-rate o f the exhaled air as well as by its vo lu m e , two im po rtan t co m p o ne nts o f a cough. The airflom e te r was held h o rizo n tally w hile the subject coughed into it thro u g h a m o uth pie ce . A nose c lip ensured no escape o f air th ro u g h the nasal passage. (Fig. 1.) T he n u m b e r o f readings for a given subject in each o f the positions varied fro m three to seven. R e ad ing s were only tab u late d w hen the subject was fa m ilia r w ith the use o f the A irflow 'm eter and ceased w hen readings reached a m a x im u m p lateau. T he highest value o b ta in ed in each p ositio n was tak en as the basis o f co m p arison seeing that it was ap p ro x im ate ly the best o f w hich the subject was capable. S U M M A R Y The influence o f different p o s tu re v on the effectiveness o j co u g hing was investigated. T wenty n o rm a l young w om en served as subjects rind the average airflow values were d e term ine d a n d stand ard ize d fo r each positio n. The best results were o b ta in e d in the u prig ht p ositio n and this correlated perfectly with the und e rlying physiology. Fig 1: The Airflowmeter R ESU L T S T he average airflow values an d the standard deviation as well as the 95 ;,, confidence lim its were calculated. The highest average airflow was ob tain ed in upright sitting an d the second highest in long sitting. T he value obtained in u prig ht sitting was statistically significantly superior on a I",, level. T he 20 subjects differed in vital capacity and th e re fo ^ the airflow values were standardized w ith the uprighl position taken as 100",,. (Fig. 2.) Effectiveness o f co u g h in g increased with the change in posture from side-lying to supine and from supine to a progressively m ore u prig ht position. In both the supine an d half-lying positions better results were ob­ tained w ith the legs flexed. F ro m the linear relation between the u prig ht and long sitting positions (F ig. 3). it is apparent that subjects coughed consistently, i.e. subjects w ho coughed well registered relatively higher readings in all the positions than those w ho coughed poorly. F ro m Fig. 2 we can see that the u prig ht sitting position is the o p tim u m posture for effective coughing. D IS C U S S IO N T he act o f co u g h in g can be analyzed into three phases:' (F ig . 4.) R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) JUNIE 1977 F I S I O T E R A P I E 9 ioo% A SID E- F L A T l SID E- S U P IN E S U P IN E 4 L Y IN G * L Y IN G L O N G U P R IG H T L Y IN G SID E L Y IN G LEGS LEGS LEGS LEGS S IT T IN G S IT T IN G L Y IN G LEGS E X T E N D E D F L E X E D E X T E N D E D F L E X E D F L E X E D " y a^c. N>\ — ^ —̂ - —L n Fig. 3 A IR F L O M E T E R U N I T S R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) 10 P H Y S I O T H E R A P Y JUNE, 1977 IN S P IR A T O R Y P H A S E C O M P R E S S IO N P H A S E Fig. 4 E X P U L S IO N P H A S E The inspiratory phase A deep breath is taken moving into the lungs the bulk of the inspiratory reserve volume. The compression phase The glottis is quickly and tightly closed while the expiratory intercostal and the accessory muscles of respiration, especially the abdom inal muscles, contract forcibly so that the intrathoracic and intra-abdominal pressures rise. The expulsion phase The glottis suddenly opens since the intra-abdominal pressure is now higher than the intrathoracic pressure and the diaphragm is pushed up, producing a violent, explosive movement o f the air from the lower to the upper respiratory tract. The large pressure difference between alveolar pressure and upper tracheal pressure (now atmospheric) results in a very rapid flow rate. !In addition, the high intrathoracic pressure causes the non-cartilaginous part of the intrathoracic trachea to be compressed and inverted to 16% of its original size. The air rushing through this greatly narrowed trachea has a high linear velocity (calculated to be 85% of the speed of sound),1 and this dislodges foreign material or mucous secretions and pushes them into the pharynx from where they are expectorated. The results obtained can be explained in terms of the following aspects of physiology: The effectiveness of coughing is closely related to the functional residual capacity (F R C ) at which it begins. (The F R C is the lung capacity which exists between the recoil o f the lung which tends to collapse and the elastic forces of the thorax which tends to expand). The F R C decreases by 1 000 ml with the change from the upright to the supine position.5 This volume decrease is effected by the upward shifting o f the diaphragm and the pres­ sure of the abdom inal contents as well as the increased size of the medial mediastinum as a result of the in­ creased venous flow.0 A decreased F R C causes the elastic recoil of the lung to decrease, which in its turn causes a retarded peak expiratory flow.7 Thus the m axim um peak expiratory flow (as found in a cough) will be decreased in a lying position and a less effective cough will be obtained. Decreased F R C is also experienced after anaesthesia and is further decreased by the supine position assumed post-operatively. Further, with diffuse obstructive pul­ monary airways syndrome (D .O .P .S.) where a situation o f increased “ trap gas” volume exists, supine postures lead to decreased F R C as well.8 W e can conclude that posture and lung pathology should be carefully evaluated for m axim um effectiveness of coughing. A C K N O W L E D G E M E N T S D r. J. C. V erm aak, M .B ., Ch.B ., M .M ed. (Anaes.L D r. J. B. de V aal, M .B ., C h.B ., M .M e d . (Int.) of t h l Respiratory U nit, the personnel o f the Lung function^ laboratories, Tygerberg Hospital, and Prof. P. A . Foster, M.B. Ch.B., F .F .A ., R .C .S .I., D .A . (D ublin), D.A. (Lond.), Head, Department of Anaesthetics, University of Stellenbosch and Tygerberg Hospital, Tiervlei, for their encouragement and help. R E F E R E N C E S 1. Schamroth, L. (1976): Personal experiences, S. Afr. M ed. J., 50, 297. 2. Friedm an, M . (1975): Assessment of Lung Function using an Airflowmeter, Lancet, 1, 7902. 3. K apandji, I. A. (1970): The Physiology of the Joints, 2nd ed., Edinburgh, Churchill Livingstone, 3, 164. 4. Comroe, J. H . (1965): Physiology o f Respiration, 2nd ed., Chicago, Year Book Medical Publishers Incorporated, p. 122. 5. N un n , J. F. (1969): Applied Respiratory Physiology, Great Britain, Butterworth & Co. (Publishers) Ltd., p. 90. 6. Hewlett, A . M ., Hulands, G . H ., N u n n , J. F., Heath, J. R . (1974): Functional Residual Capacity during Anaesthesia, Brit. J. of Anaesthesia, 46, 7, 479-485. R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. )