[The Nocturnal Respiratory Rate in COPD Patients of Varying GOLD Severity with/without Nicotine Consumption: Calculation by Means of Breath Sound Analysis]

Respiratory rate is an important risk marker and enables early detection of critically ill and vulnerable patients in clinical routine. The aim of this pilot study with 31 patients (COPD severity levels II - IV) was to determine the mean nocturnal respiratory rate based on breath sound recordings and to investigate the dependence of respiratory rate on COPD severity level and smoker status. The mean respiratory rate of the total collective was 19/min. For the COPD-GOLD severity levels, no significant differences in mean respiratory rate could be observed. When nicotine consumption is taken into account, active smokers showed a significantly higher mean respiratory rate of 20.84 ± 4.45/min compared to non-smokers with 17.41 ± 3.14/min (p < 0.05). In addition, active smokers in the study were significantly more frequent among patients with night-time wheezing (60 % vs. 23.8 %). This might suggest that smokers need to perform increased breathing work with increased breathing rate to compensate for oxygen deficiency in bronchial obstruction. The results of the present study show that with the acoustic recording of breath sounds, a reliable representation and calculation of the breath frequency is possible.