Investigating breathing patterns of asthma patients during exercise using a novel parameter

Abstract

<b>Introduction:</b> Exercise induced dyspnoea (EID) in patients with asthma is often attributed to exercise induced bronchoconstriction. However, around 29% of patients with asthma suffer from dysfunctional breathing which can also lead to EID. This study investigates (possibly dysfunctional) breathing patterns during exercise in patients with asthma as compared to healthy subjects. <b>Methods:</b> Breathing patterns of 15 healthy subjects and 12 asthma patients were compared during a maximal cycling ergometry test. The breathing pattern was quantified with a newly developed parameter called BPratio, which is tidal volume (Vt) divided by breathing frequency (Bf) and predicted vital capacity. Asthma control was assessed by the ACQ, mini-AQLQ and VAS scores. <b>Results and Discussion</b>: In the majority of subjects, Vt increased from the start and Bf only increased in&nbsp;the last part of&nbsp;the test, generally considered as a normal pattern. However, in 33% of healthy subjects and 42% of the asthma patients, Bf increased much earlier. This results in a roughly constant BPratio during the majority of the test. The asthma patients with an early increase of Bf experienced worse asthma control than the other asthma patients (ACQ of 1.6 vs 0.14 (p=0.14), VAS for dyspnoea over past 7 days (16.5mm vs 2.0mm (p=0.04)), and mini-AQLQ scores of 4.65 vs 6.67 (p=0.11)). This deviant breathing pattern is likely caused by elevated physical stress perception during exercise. <b>Conclusion:</b> A deviant breathing pattern, quantified&nbsp;with&nbsp;the novel parameter BPratio, can be related to worse asthma control. This makes the BPratio a promising tool to quantify breathing patterns during exercise, which can support the diagnosis of DB in asthma patients.