Predicting Dynamic Inspiratory Muscle Strength in COPD and Asthma Patients

This observational study evaluates whether dynamic inspiratory muscle strength can be estimated in patients with chronic obstructive pulmonary disease (COPD) and asthma using simple clinical and performance-based measurements. Dynamic inspiratory muscle strength was assessed using the S-Index, which reflects the pressure generated during a fast and forceful inspiration while airflow is maintained. The study included adult male patients diagnosed with COPD or asthma. Participants completed respiratory muscle strength assessment, pulmonary function testing, body composition assessment, and a fixed-pressure inspiratory muscle performance test using a threshold loading device set at 30 cmH₂O. The number of inspiratory repetitions performed until task failure and related respiratory variables were recorded. The main aim of the study was to develop prediction models for estimating S-Index values from accessible measures such as peak inspiratory flow, inspiratory repetition performance, spirometry parameters, and body composition variables. The study may help determine whether dynamic inspiratory muscle strength can be estimated in clinical settings where direct S-Index measurement devices are not available.