Poor cough flow in acute stroke patients is associated with reduced functional residual capacity and low cough inspired volume

Abstract

IntroductionEach year 7 million people die of stroke worldwide; most deaths are caused by chest infections. Patients with acute stroke have impaired voluntary cough flow, associated with increased risk of chest infections. Reduced functional residual capacity (FRC) could lead to impaired cough flow. We therefore compared FRC in acute hemiparetic stroke patients and controls and explored its relationship with volume inspired before cough and voluntary cough peak flow.Methods21 patients within 2 weeks of first-ever middle cerebral artery territory (MCA) infarct (mean (SD) age 68 (11) years, 10 females) and 30 controls (58 (11) years, 15 females) underwent FRC and voluntary cough testing (cough inspired volume and peak flow) while semirecumbent. FRC was expressed as % predicted; cough inspired volume was expressed as % predicted VC and cough peak flow as % predicted PEF. A clinician scored stroke severity using the National Institutes of Health Stroke Scale (NIHSS).ResultsPatients’ reclined FRC, voluntary cough peak flowand cough inspired volume were reduced compared with controls (p<0.01 for all): patients’ median (IQR) FRC 76 (67–90) % predicted, mean (SD) cough inspired volume 64 (20) % predicted and mean (SD) peak cough flow 61 (32) % predicted despite them having only mild stroke-related impairments: median NIHSS score 4 (IQR 2–6). Univariate linear regression analyses showed FRC predicted cough inspired volume (adjusted R2=0.45) and cough inspired volume predicted cough flow (adjusted R2=0.56); p<0.01 for both. Sitting patients upright increased their FRC by median 0.210 L.ConclusionsFRC and cough inspired volume in the reclined position are significantly reduced in acute hemiparetic stroke patients with mild impairments; both factors are associated with poor voluntary cough peak flow.

Global Physiology and Pathophysiology of Cough

“…With strong cough stimuli, the number of cough re-accelerations increases for each inspiratory volume [36,37]. The critical importance of high airflow velocity on shearing forces dislodging material from the wall of the airway results in the documented relevance of cough expiratory airflow volume acceleration and cough peak expiratory airflow velocity measurements for cough efficacy and strength [39][40][41][42].…”

Global Physiology and Pathophysiology of Cough

“…Although cough reflex thresholds at 3 months poststroke may be similar to those of healthy control subjects, 49 patients in the acute phase with a middle cerebral artery infarct demonstrated lower functional residual capacity, lower cough inspired volume, and lower voluntary CPF. 50 In a study of cough reflex testing with nebulized tartaric acid, conducted in 818 patients with acute stroke, 82 had weak or absent cough responses. Of these, 11% developed pneumonia compared with 3.5% of those who had a normal response to the cough challenge.…”

Clinical Significance of Cough Peak Flow and Its Non-Contact Measurement via Cough Sounds: A Narrative Review

“…Thus, the volume inspired before coughing (operating volume) and the function of the inspiratory muscles are essential for coughing [15]. The functional residual capacity is a strong and significant predictor of the operating volume (adjusted R 2 = 0.45, p < 0.01) [16]. In normal adults, the operating volume is approximately 3.4 L [16].…”

“…In normal adults, the operating volume is approximately 3.4 L [16]. In addition, the operating volume is an important determinant of the CPF [16,17], and the CPF has a significant positive association with the maximal inspiratory pressure, which is a marker of inspiratory muscle weakness in patients with cervical spinal cord injuries [18] and in males over 60 years old [19].…”