Evaluation of respiratory muscle strength and cough capacity in heroin-dependent individuals: a comparative cross-sectional study

This study aimed to evaluate respiratory muscle strength and cough capacity in individuals using heroin and to compare these findings with those of healthy smokers and non-smokers. The study sample included 131 individuals with heroin dependence and 138 healthy controls (76 smokers and 62 non-smokers). Dyspnea severity was assessed using the modified Medical Research Council Scale (mMRC). Respiratory muscle strength, specifically maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP), was measured using a portable electronic mouth pressure device. Peak cough flow rate (PCFR) was evaluated with a peak flow meter. The mMRC scores of heroin-dependent individuals were significantly higher compared to both smokers and non-smokers ( p < 0.0001). Regarding respiratory muscle performance, heroin users exhibited significantly lower MIP, MIP (%predicted), MEP (%predicted), and PCFR values than both control groups ( p < 0.05). After covariate adjustment, significant between-group differences remained for MIP, MIP (%predicted), and PCFR, whereas the differences in MEP and MEP (%predicted) were no longer statistically significant. The findings indicate that individuals with heroin dependence may have impaired inspiratory muscle performance and lower cough efficacy than both smokers and non-smokers. These impairments, combined with increased severity of dyspnea, suggest that heroin dependence may be associated with additional respiratory impairment beyond the effects observed with tobacco smoking. Incorporating respiratory muscle assessments and targeted strengthening interventions into multidisciplinary rehabilitation programs may help identify respiratory impairments and potentially improve clinical outcomes in this population.