Physiological responses to cardiopulmonary and field exercise tests in primary ciliary dyskinesia compared with healthy peers

Purpose: Primary ciliary dyskinesia (PCD) is a rare disorder characterized by defective motile cilia, impairing airway mucociliary clearance. Children with PCD (cwPCD) may exhibit distinctions in exercise responses compared to healthy peers (HP). We aimed to compare physiological responses to cardiopulmonary exercise testing (CPET), incremental shuttle walk test (ISWT), and 6-min walk test (6MWT) in cwPCD and HP and investigate the associations between clinical parameters. Methods: Twenty-three cwPCD and 23 HP were included. Pulmonary function and respiratory muscle strength were assessed. All participants performed CPET, ISWT, and 6MWT. Heart rate (HR), blood pressure (BP), oxygen saturation (SpO₂), and dyspnea and fatigue (modified Borg Scale) were assessed before and after tests. Results: In cwPCD, CPET and ISWT revealed similar HR, SpO₂, systolic BP, dyspnea, and fatigue responses (p > 0.05), while 6MWT elicited lower responses in these parameters (p < 0.05). cwPCD had lower ∆HR (p = 0.003), peak oxygen uptake (peakV˙O2) (p = 0.048), relative peakV˙O2 (p = 0.041), and higher minute ventilation/carbon dioxide production (V̇_E/V˙CO2) at anaerobic threshold (p = 0.047) compared to HP. PeakV˙O2 correlated with ISWT distance (ISWD) (r = 0.592) and 6MWT distance(6MWD) (r = 0.601) in cwPCD and HP (r = 0.648, r = 0.507, respectively) (p < 0.05). Regression equations were developed: relative peakV̇O₂ (mL/min/kg) = − 25.630 + 0.083 × 6MWD (m) [F_(1–21) = 7.719, p = 0.011, R² = 0.269] and relative peakV˙O2(mL/min/kg) = 1.922 + 0.032 × ISWD(m) [F_(1–21) = 11.790, p = 0.002, R² = 0.329). Conclusion: CPET and ISWT evoke comparable responses, while 6MWT results in lower physiological responses. However, 6MWT remains useful, given its association with peakV˙O2. The cwPCD have an altered V˙E control and early CO₂ increase with exercise, greater ventilatory inefficiency, and chronotropic impairment. Compared to field tests, CPET can be more helpful for determining ventilatory inefficiency and chronotropic impairment in PCD. ClinicalTrials.gov identifier: NCT05712798 (Registration Date: 26.01.2023).