Responses to progressive exercise in subjects with chronic dyspnea and inspiratory muscle weakness

Abstract

Introduction Inspiratory muscle weakness (IMW) is a potential cause of exertional dyspnea frequently under‐appreciated in clinical practice. Cardiopulmonary exercise testing (CPET) is usually requested as part of the work‐up for unexplained breathlessness, but the specific pattern of exercise responses ascribed to IMW is insufficiently characterized. Objectives To identify the physiological and sensorial responses to progressive exercise in dyspneic patients with IMW without concomitant cardiorespiratory or neuromuscular diseases. Methods Twenty‐three subjects (18 females, 55.2 ± 16.9 years) complaining of chronic daily life dyspnea (mMRC = 3 [2‐3]) plus maximal inspiratory pressure < the lower limit of normal and 12 matched controls performed incremental cycling CPET. FEV1/FVC<0.7, significant abnormalities in chest CT or echocardiography, and/or an established diagnosis of neuromuscular disease were among the exclusion criteria. Results and Conclusion Patients presented with reduced aerobic capacity (peak V̇O2: 79 ± 26 vs 116 ± 21 %predicted), a tachypneic breathing pattern (peak breathing frequency/tidal volume = 38.4 ± 22.7 vs 21.7 ± 14.2 breaths/min/L) and exercise‐induced inspiratory capacity reduction (‐0.17 ± 0.33 vs 0.10 ± 0.30 L) (all P < .05) compared to controls. In addition, higher ventilatory response (ΔV̇E/ΔV̇CO2 = 34.1 ± 6.7 vs 27.0 ± 2.3 L/L) and symptomatic burden (dyspnea and leg discomfort) to the imposed workload were observed in patients. Of note, pulse oximetry was similar between groups. Reduced aerobic capacity in the context of a tachypneic breathing pattern, inspiratory capacity reduction and preserved oxygen exchange during progressive exercise should raise the suspicion of inspiratory muscle weakness in subjects with otherwise unexplained breathlessness.

Cardiopulmonary Exercise Testing in the Assessment of Dysfunctional Breathing

“…These stressful events can include excessive aerobic training, bereavement or a health-related illness ( Courtney, 2009 ). Respiratory diseases (such as asthma or COPD) as well as musculoskeletal dysfunction, pain or an altered chest wall shape can also cause DB, by triggering the diaphragm into an abnormal pattern of breathing ( Barker and Everard, 2015 ; Berton et al, 2020 ).…”

Effectiveness of a training program for a patient with non-cardiac chest pain that combines intervention to improve quality of life, psychological state, and functional capacity: a case report

“…When subjects with inspiratory muscle weakness showing symptoms of overexertion (shortness of breath and leg discomfort) were compared with controls, a higher metabolic and ventilation demand for a given work rate in serial measurements of lung volumes and symptomatic perception during submaximal exercise was observed. Decreased inspiratory capacity associated with an excessive tachypnea breathing pattern and preserved oxygen gas exchange indicates inspiratory muscle weakness that contributes to effort intolerance and dyspnea [ 25 ]. The physical activity level of our patient who received the combined training changed from sedentary to minimally active, and the level of physical activity increased.…”

The pulmonary function laboratory in the investigation of dyspnea of unknown origin

“…Incremental cardiopulmonary exercise testing revealed a tachypneic breathing pattern with a consistent reduction in dynamic inspiratory capacity despite the lack of resting hyperinflation; moreover, she reported disproportionate dyspnea relative to the achieved work rate (a Borg scale score of 5/10 at 45 W, > the 95th percentile). 1 These findings raised the suspicion of inspiratory muscle weakness/fatigue 2 : although MIP and MEP were reduced, they were still within the limits of normal. Of note, however, 12-s maximal voluntary ventilation (MVV; 38 L/min) was reduced both in % of predicted (47%) and relative to the MVV estimated from FEV 1 (73 L/min).…”