Analysis of the breathing pattern in patients with asthma during physical exercise: A cross-sectional study

Background: About 25 % of patients with asthma suffer from dysfunctional breathing, often leading to exercise induced dyspnoea (EID). EID, however, is often attributed to exercise induced bronchoconstriction, while the contribution of dysfunctional breathing to EID is overlooked. This leads to potential suboptimal treatment of patients with asthma. Therefore, this study investigates the breathing patterns of patients with asthma during exercise compared to healthy subjects and its influence on the level of EID. Methods: This cross-sectional study investigated individual breathing patterns of 15 well-controlled asthma patients and 15 healthy subjects during a cardiopulmonary exercise test (CPET), objectified with a newly designed parameter Breathing Pattern (BP) angle. This parameter describes the gradual relation between the increase in tidal volume and breathing frequency in the middle phase of CPET (40–60 % of max load reached) corrected for forced vital capacity. Dyspnoea was assessed with VAS and Borg scores. Results: BP angle and other CPET parameters were similar among groups. In both groups, 3 subjects had a BP angle<45° (n = 6), indicating relative fast shallow breathing during mid-level exercise. They experienced a significantly higher level of dyspnoea at max exercise compared to subjects with BP angle>45° (n = 24) (VAS: 86.5 vs 65.5 mm (p = 0.036), Borg: 8 vs 4 (p = 0.001)). Discussion: An increase of breathing frequency at mid-level exercise, quantified with BP angle, is related to higher levels of dyspnoea. This indicates that dysfunctional breathing patterns play an important role in the development of exercise induced dyspnoea in patients with asthma and require more attention regarding treatment.