A Pilot Study of Change in Laryngeal Cough Threshold Sensitivity and PAS(Penetration Aspiration Scale) Score Within the Acute Stage
Thesis DisciplineSpeech and Language Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Background: Cough Reflex Testing (CRT) has been shown to be useful in the challenging task of identifying silent aspiration (aspiration without a cough response). With the emergence of the routine clinical use of CRT in the acute stroke population, the following clinical conundrum often arises: Does passing a previously failed CRT mean the risk of silent aspiration has resolved? The purpose of this study was to evaluate the association between change in laryngeal cough threshold sensitivity and change in PAS (Penetration Aspiration Scale) score within the acute stage post-stroke. Methods: This was a prospective longitudinal pilot study of 20 acute stroke patients utilizing a Cough Reflex Threshold Test (CRTT) at 0.4M, 0.6M and 0.8M citric acid concentrations and Fiberoptic Endoscopic Evaluation of Swallowing (FEES). A cough response threshold was obtained from the CRTT and a PAS (penetration aspiration scale) score from FEES. Inclusion criteria required a PAS score of 4 or above on preliminary FEES or impaired CRT threshold as defined by weak or failed cough test result at 0.8M citric acid concentration. Both test methods were repeated every four days for 20 days or until the participant no longer aspirated/penetrated and had a normal result on CRTT on two consecutive assessment sessions. Agreement between changes in the two tests was evaluated using the Cohen’s Kappa statistic. Results: Eighteen of the twenty participants in this study aspirated on initial assessment, ten of which were silent. One participant continued to aspirate at study completion. On initial assessment eleven participants had a C2 response threshold at 0.4M citric acid concentration and three participants failed to reach threshold at 0.8M citric acid concentration. At study completion, 18 participants had a C2 response threshold at 0.4M citric acid concentration and one participant failed to reach threshold at 0.8M citric acid concentration. During the study, sixty-six re-assessments took place; there were fifteen incidences of improved cough response threshold on re-assessment and thirty-one incidences of improved PAS score. There was no significant agreement between improved laryngeal cough reflex threshold and improved PAS score during the acute stage Kappa = 0.0598 (p <.0.574), 95% CI (- 0.1496- 0.2692). Conclusion: Significant limitations of this study included small data set and potential flooring effect of the CRT. Due to the limitations of this study, no conclusions can be made as to the appropriateness of reinstating oral intake based on passing a previously failed CRT.