Coughing frequency in patients with persistent cough: assessment using a 24 hour ambulatory recorder

Abstract

C Co ou ug gh hi in ng g f fr re eq qu ue en nc cy y i in n p pa at ti ie en nt ts s w wi it th h p pe er rs si is st te en nt t c co ou ug gh h: : a as ss se es ss sm me en nt t u us si in ng g a a 2 24 4 h ho ou ur r a am mb bu ul la at to or ry y r re ec co or rd de er r ABSTRACT: Cough is an important symptom of many respiratory disorders. We determined the frequency and diurnal variation of cough in normal subjects and in patients with asthma or with persistent cough of unknown cause. We used a portable, solid-state, multiple-channel recorder to record cough sounds over a 24 h period. The audio-signal was recorded from a unidirectional microphone strapped over the chest wall, and electromyographic (EMG) signals from the lower respiratory muscles were simultaneously registered with surface electrodes. The recorded digital data were examined on an IBM-compatible computer, and the typical signals induced by cough (as assessed by voluntary or experimentally-induced cough) were counted.In 12 normal subjects, only 0-16 coughs were recorded over 24 h. In 21 stable asthmatics with a history of chronic cough ("asthma") the median number was 282 (ranges: 45-1,577), and in 14 patients with the predominant symptom of daily dry coughs ("chronic coughers") the median number was 794 (64-3,639). In both groups of patients, there was a diurnal variation of coughs, such that the least numbers occurred between 2 and 5 a.m. (<3% of total). In the asthma group, there was no significant correlation between forced expiratory volume in one second (FEV 1 ) (% predicted) or diurnal variation of peak expiratory flow and cough frequency. In the chronic coughers, there was a significant correlation between daytime cough numbers and daytime cough symptom scores but not for the night-time values.Our data show that cough frequency is not determined by the severity of asthma in relatively stable asthmatics on inhaled steroids, and is reduced during sleep in both asthmatics and chronic cough patients. This portable cough recorder may be useful in the assessment of drug therapy for chronic cough.

The effect of codeine on the Urge-to-Cough response to inhaled capsaicin

“…There was a direct relationship between both airflow and EMG measures of cough intensity and capsaicin concentration. While auditory cough counting score, and the number of expulsive events increased with for each cough priming inspiration and the counted number of "coughs" increased with increasing capsaicin concentration [6][7][8][9], unfortunately the increase in the number of counted coughs does not provide a measure of the intensity of the cough. Thus, the combination of the measurement of airflow pattern and EMG activity allows determination of the expulsive event intensity, and the sum of the expulsion intensities for each priming inspiration provides a measure of the cough intensity.…”

“…The incidence of expulsive events for each cough bout also increased such that there was a greater incidence of CR3, CR4 and CR5 as the concentration of capsaicin increased. The number of expulsive events is one measure of the intensity of a cough [6,7,9].…”

“…The cough motor pattern is characterized by lung inflation (the lung volume priming phase), closure of the glottis with the compression phase and a rapid expulsive phase followed by a sustained plateau of airflow [15]. However, the airflow expulsive phase of the cough is often interrupted by reclosure of the glottis [2,6,7,15,16]. This results in more than one expulsive event for an individual priming inflation.…”

“…It is also known that as capsaicin concentration increases, there is an increase in the number of coughs counted [3][4][5][6][7][8]. This cough number response to capsaicin concentration is one measure of cough sensitivity [9].…”

What is cough and what should be measured?

“…However the method is labour-intensive and probably impractical in ambulatory conditions. For these reasons automated audiometric methods have been devised [24][25][26]. These are dealt with in detail elsewhere in this Special Issue [27].…”