Characterization of dysfunctional breathing using cardiopulmonary exercise testing.

Cardiopulmonary exercise testing (CPET) is emerging as a useful tool in the identification of dysfunctional breathing (DB). We aimed to evaluate the prevalence and functional impact of different patterns of DB in 628 adult patients referred for CPET due to unexplained dyspnoea (August 2019-December 2023). Patients were assigned to four groups following CPET interpretation: normal, breathing pattern disorder (BPD), hyperventilation (HV), and combined BPD with HV (BPDHV). Demographic and CPET performance data were analyzed using non-parametric tests as appropriate. 94 (15.0%) patients had normal CPETs and 267 (42.5%) were identified as having DB. The remaining 267 were excluded as having alternative diagnoses. Of those with DB, 145 (54.3%) had BPD, 41 (15.4%) had HV, and 81 (30.3%) had BPDHV. VE/VCO was significantly increased in HV or BPDHV only (p < 0.001). Patients in all three DB groups exhibited significantly impaired peak VO compared to those with normal CPETs (p < 0.001). These CPET findings highlight DB as a common driver of symptoms in unexplained dyspnoea. Over half of patients with DB had isolated BPD, which requires visual inspection of relevant CPET plots to diagnose. Those identified with DB had significantly reduced peak VO, which may be a useful classifier of functional severity in DB.