Background: Respiratory work and respiratory oxygen consumption increase in IPF. Exertional dyspnea, the most prominent symptom of IPF, results from the effort of the respiratory muscles trying to meet the increased respiratory work. Thus, the presence of dyspnea and reduced exercise capacity may be associated with respiratory muscle dysfunction.

Objective: To investigate the relationship between respiratory muscle functions, dyspnea, fatigue, functional exercise capacity and quality of life in patients with IPF.

Methods: Thirteen patients (2 females, 11 males), mean age= 66.38±7.44, diagnosed with IPF were enrolled in the study. A Visual Analog Scale (VAS) was used to evaluate dyspnea and fatigue. Respiratory muscle strength and endurance (maximal inspiratory pressure-MIP, maximal expiratory pressure-MEP) were assessed using mouth pressures and the incremental load test. Functional exercise capacity was evaluated with the 6-minute walking test (6MWT). The modified Borg scale was used before and after the 6MWT for the evaluation of exertional dyspnea and fatigue. Nottingham Health Profile (NHP) was used to evaluate the quality of life.

Results: There was a significant moderate correlation between the incremental load test and VAS dyspnea (r=0.581,p=0.0037). Also, there were significantly high correlations between the incremental load test and The modified Borg scale for exertional dyspnea and fatigue (r=0.886 p<0.001, r=0.871 p<0.001, respectively). 6MWT, NHP, and VAS fatigue were not correlated with respiratory parameters.

Conclusion: Our results showed that exertional dyspnea and fatigue are related to respiratory muscle endurance in patients with IPF.