Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, C103
Acute Hemispheric Stroke Patients Have Reduced Functional Residual Capacity and Cough Flow Rates
P. Rao1, K. Ward1, C. Reilly1, G. Rafferty1, J. Moxham1
1. King's College London, London, United Kingdom.
Cough is a complex manoeuvre, requiring coordinated action of the respiratory and upper airway musculature. The mechanisms of impaired cough following hemispheric stroke are unclear. Reduced functional residual capacity (FRC) may impair cough due to the effect of lung volume on the length and pressure generating capacity of the expiratory muscles. We compared FRC (primary outcome) and peak cough flow rate for voluntary cough (PCFR, secondary outcome) in stroke patients and healthy controls. 25 patients and 30 healthy controls were studied. Stroke patients were within two weeks of first-ever middle cerebral artery infarct. Stroke severity was scored by a clinician (NIHSS score, worst=31). FRC was measured by helium dilution using a dry rolling seal spirometer. To measure PCFR, subjects wore a tight-fitting facemask and were asked to cough forcefully into the spirometer. Measurements were performed in a chair with the back reclined to 45 degrees, mimicking patient position in hospital. FRC and PCFR data were expressed as % predicted1, as controls were younger. Table 1. Patients’ median NIHSS score was 4 (IQ range 3 to 7) reflecting mild disability. FRC % predicted and PCFR were significantly reduced in patients. Linear regression analysis showed FRC to be a significant predictor of PCFR, P=0.001.(Figure 1) FRC (% predicted) and PCFR were significantly reduced in acute hemispheric stroke patients. Higher peak cough flow rates are associated with greater lung volume prior to cough. Interventions that increase FRC eg continuous positive airway pressure and upright sitting may improve cough function in stroke patients.
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