Background: Primary ciliary dyskinesia (PCD) is a rare disease characterized by impaired lung function and increased work of breathing that may contribute to decreasing muscle oxygenation (SMO₂) and exercise capacity. The study aimed to compare SMO₂, exercise capacity, and activities of daily living (ADL) in PCD patients with and without inspiratory muscle weakness (IMW).

Method: Seventeen PCD patients with IMW (7F, 10M, 13.6±3.8 years, forced expiratory volume in one second (FEV₁) 72.2±15.3%) and 18 patients without IMW (11F, 7M, 13.5±2.9 years, FEV₁ 82.9±10.4%) were included. Pulmonary function was recorded. Inspiratory muscle strength (MIP) was measured using a mouth pressure device. Exercise capacity (incremental shuttle walk test, ISWT), and ADL (Glittre ADL test) were assessed. SMO₂ was recorded using a wearable lactate threshold device during ISWT and Glittre ADL test.

Results: ISWT distance (740.0±116.6 vs 628.2±121.4 m, p=0.009), and SMO₂ during ISWT (-3.61±3.38% vs -0.94±3.13%, p=0.021) and ADL test (-5.83±3.65% vs -2.82±4.95%, p=0.048), FEV₁ (%) and forced vital capacity (FVC) (%) were higher in patients without IMW compared to patients with IMW (p<0.05). The duration of the ADL test was lower in patients without IMW than in those with IMW (215.33±34.31 vs 246.41±49.72, p=0.038).

Conclusion: SMO₂, exercise capacity, and ADL were worse in PCD with IMW. Impaired inspiratory muscle strength may lead to worsening in pulmonary and extrapulmonary features. Therefore, MIP is one of the critical parameters that should be evaluated in these patients.