A novel reflex cough testing device

Kazunori Fujiwara,Satoshi Koyama,Takahiro Fukuhara,Hiromi Takeuchi,Katsuyuki Kawamoto,Yoko Shimizu,Hiroya Kitano,Hideyuki Kataoka

doi:10.1186/s12890-017-0365-y

Kazunori Fujiwara, Satoshi Koyama + Show 6 more

Open Access

https://doi.org/10.1186/s12890-017-0365-y

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Abstract

BackgroundThe reflex cough test is useful for detecting silent aspiration, a risk factor for aspiration pneumonia. However, assessing the risk of aspiration pneumonia requires measuring not only the cough reflex but also cough strength. Currently, no reflex cough testing device is available that can directly measure reflex cough strength. We therefore developed a new testing device that can easily and simultaneously measure cough strength and the time until the cough reflex, and verified whether screening with this new instrument is feasible for evaluating the risk of aspiration pneumonia.MethodsThis device consists of a special pipe with a double lumen, a nebulizer, and an electronic spirometer. We used a solution of prescription-grade L-tartaric acid to initiate the cough reflex. The solution was inhaled through a mouthpiece as a microaerosol produced by an ultrasonic nebulizer. The peak cough flow (PCF) of the induced cough was measured with the spirometer.The 70 patients who participated in this study comprised 49 patients without a history of pneumonia (group A), 21 patients with a history of pneumonia (group B), and 10 healthy volunteers (control group).ResultsWith the novel device, PCF and time until cough reflex could be measured without adverse effects. The PCF values were 118.3 ± 64.0 L/min, 47.7 ± 38.5 L/min, and 254.9 ± 83.8 L/min in group A, group B, and the control group, respectively. The PCF of group B was significantly lower than that of group A and the control group (p < 0.0001), while that of group B was significantly lower than that of the control group (p < 0.0001). The time until the cough reflex was 4.2 ± 5.9 s, 7.0 ± 7.0 s, and 1 s in group A, group B, and the control group, respectively. This duration was significantly longer for groups A and B than for the control group (A: p < 0.001, B: p < 0.001), but there was no significant difference between groups A and B (p = 0.0907).ConclusionOur newly developed device can easily and simultaneously measure the time until the cough reflex and the strength of involuntary coughs for assessment of patients at risk of aspiration pneumonia.

Highlights

The reflex cough test is useful for detecting silent aspiration, a risk factor for aspiration pneumonia
This paper describes the use of an objective examination system, called the modified reflex cough test (RCT), to quantify both a tartaric-acidstimulated involuntary cough and the time until the cough reflex
The 49 patients without previous pneumonia were classified as group A, and 21 with such a history comprised group B

Summary

Introduction

The reflex cough test is useful for detecting silent aspiration, a risk factor for aspiration pneumonia. Assessing the risk of aspiration pneumonia requires measuring the cough reflex and cough strength. We developed a new testing device that can and simultaneously measure cough strength and the time until the cough reflex, and verified whether screening with this new instrument is feasible for evaluating the risk of aspiration pneumonia. Pneumonia is a common event after strokes and is associated with morbidity and mortality in stroke patients. Several screening tests, including the water test, food test, and saliva swallowing test, cannot detect silent aspiration in patients without a cough reflex

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