Inter-individual variability of added lung sounds in a healthy population

Introduction: Computer aided lung sound analysis (CALSA) can provide a wealth of information about normal and adventitious lung sounds. Currently there is a lack of information about the ‘normality‘ of these sounds and how they relate to anthropometric variables. This research aimed to create a database of normal reference values and explore the effect that gender, height, body mass index (BMI) and lung function might have on crackle parameters.Methods: One hundred healthy participants were recruited; anthropometric and spirometry data were collected. A digital stethoscope connected to a laptop was used to record lung sounds at seven chest locations; participants were seated and mouth breathing slightly deeper than tidal volume. Lung sound data were analysed by time expanded waveform analysis. Descriptive and inferential statistics were used to summarise data and test hypotheses.Results: Males were found to have significantly longer durations of initial deflection width (IDW) compared to females at two chest wall locations (p<0.05). Two cycle deflection (2CD) differed significantly (p<0.05) at three locations for participant heights <1.71m compared to ?1.71m. Only one significant correlation (trachea) was found between BMI and IDW (r=0.214, p=0.033) and BMI and 2CD (r=0.245, p=0.014). Although some statistically significant relationships were detected between lung function and crackle parameters, the highest r was 0.29.Conclusions: There was no convincing evidence of any consistent relationship between crackle frequency and gender, height, BMI or lung function. Therefore, it is unlikely these variables are responsible for the inter-individual differences noted in crackle parameters in healthy people