Introduction Cough is a complex manoeuvre, requiring coordinated action of the respiratory and upperairway 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 flowrate for voluntary cough (PCFR, secondary outcome) in stroke patients and healthy controls.
Methods 27patients and 30 healthy controls were studied. Stroke patients were within 2 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 spirometre. To measure PCFR, subjects wore a tight-fitting facemask and were asked to cough forcefully into the spirometre. During these measurements, the volume inspired before the cough manoeuvre was also recorded. Measurements were performed in a chair with the back reclined to 45°, mimicking patient position in hospital. FRC and PCFR data were expressed as % predicted.1
Results Patients' median NIHSS score was 4 (IQR 2–6) reflecting mild disability. FRC % predicted, the volume inspired before cough and PCFR were significantly reduced in patients. Both FRC and the volume inspired before cough were significant predictors of PCFR.
Conclusions FRC (% predicted), the volume inspired before cough 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, for example, continuous positive airway pressure and upright sitting may improve cough function in stroke patients.
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