The Effects of Respiratory Muscle Performance on Clinical Outcomes in Obese Patients

Introduction: Respiratory muscle (RM) performance has been theorized to contribute to exercise-induced dyspnea, exercise intolerance, and low exercise capacity in patients with obesity. However, the impact of acute impairments in RM performance on exercise capacity in patients with obesity remains uncertain. Methods We prospectively recruited 8 participants (1 male, 7 female, Age: 43.25 ± 9.2 yrs; BMI: 49.33 ± 7.2 kg/m2; Waist Circumference: 130.38 ± 18.6 cm; Total Body Fat [%]: 52 ± 5. Diaphragm Thickness at expiration was assessed via B-mode ultrasound at the right 8th intercostal space in a semi-recumbent position. Participants performed a cardiopulmonary exercise testing (CPET) using a ramp treadmill protocol to peak exercise capacity. Measurements of RM performance were measured at baseline and repeated at 0-minutes and 5-minutes following CPET; Maximal Inspiratory Pressure (MIP), Sustained Maximal Inspiratory Pressure (SMIP), Inspiratory Duration (ID), Slope of the SMIP Plot (SMIP Slope), and Maximal Expiratory Pressure (MEP). One Way Repeated Measure ANOVA and Two-Sided Paired T-Tests were used to compare RM performance data before and after testing; statistical significance was set at p<0.05. Results: VO2peak: 18.91 ± 2.6 mL·kg-1·min-1; Peak RER: 1.02 ± 0.1; Age Predicted Heart Rate Max (%) 88 ± 13; VE/VCO2 Slope: 28.59 ± 4.2. Diaphragm Thickness: 3.05 ± 0.7 mm. When comparing Baseline to 0-minues following CPET significant reductions in MIP, SMIP, and MEP were observed: MIP (95 ± 23 cmH2O vs. 73 ± 23 cmH2O p = 0.014); SMIP (500 ± 165 PTU vs. 413 ± 176 PTU p= 0.038); MEP (74 ± 17 cmH2O vs. 62 ± 13 cmH2O 0.021). At 5-minutes following CPET, significant reductions in MIP (69 ± 17 cm H2O p= 0.008) and MEP (63 ± 13 cm H2O p= 0.013) were observed but not for any other measures of RM performance. Conclusion: Patients with obesity demonstrate significant reductions in RM performance following peak aerobic exercise which persist even after recovery but had relatively preserved RM performance at baseline. Acute fatigue of the respiratory muscles may contribute to the exercise induced dyspnea, and low exercise capacity observed in patients with obesity.