Predicting aspiration in patients with ischemic stroke: comparison of clinical signs and aerodynamic measures of voluntary cough

Abstract

Background: Clinical signs often fail to identify stroke patients who are at increased risk of aspiration. We hypothesized that objective measure of voluntary cough would improve the accuracy of the clinical evaluation of swallow to predict those patients who are at risk.

Methods: A comprehensive diagnostic evaluation was completed for 96 consecutive stroke patients that included cognitive testing, a bedside clinical swallow examination, aerodynamic and sound pressure level measures of voluntary cough, and "gold standard" instrumental swallowing studies (ie, videofluoroscopic evaluation of swallow [VSE] or fiberoptic endoscopic evaluation of swallow [FEES]). Stroke severity was assessed retrospectively using the Canadian neurologic scale.

Results: Based on the findings of VSE/FEES, 33 patients (34%) were at high risk of aspiration and (66%) were nonaspirators. Clinical signs (eg, absent swallow, difficulty handling secretions, or reflexive cough after water bolus) had an overall accuracy of 74% with a sensitivity of 58% and a specificity of 83% for the detection of aspiration. Three objective measures of voluntary cough (expulsive phase rise time, volume acceleration, and expulsive phase peak flow) were each associated with an aspiration risk category (areas under the curves were 0.93, 0.92, and 0.86, respectively). Expulsive phase rise time > 55 m/s, volume acceleration < 50 L/s/s, and expulsive phase peak flow < 2.9 L/s had sensitivities of 91%, 91%, and 82%, respectively; and specificities of 81%, 92%, and 83%, respectively for the identification of aspirators.

Conclusion: Objective measures of voluntary cough can identify stroke patients who are at risk for aspiration and may be useful as an adjunct to the standard bedside clinical assessment.

Figure 1

ROC curves for objective cough measures. IPD = inspiration phase duration; IPV = inspiration phase volume; IPPF = inspiration phase peak flow; GCPD = glottic closure phase duration. Solid (dotted) curves are ROC curves unadjusted (adjusted) for CNSS score. Aspiration is defined as a PASS ≥ 5.

Figure 2

ROC curves for objective cough measures. EPPF = expulsive phase peak flow; EPRT = expulsive phase rise time; VA = volume acceleration (or EPPF/EPRT); SPL = sound pressure level; T+ = test positive; Sens = sensitivity; Spec = specificity. Solid (dotted) curves are ROC curves unadjusted (adjusted) for CNSS score. Aspiration is defined as a PASS ≥ 5.