Exercise alveolar oxygen extraction rate reflects ventilatory efficiency and predicts outcomes in idiopathic pulmonary fibrosis.

Abstracts No Comments

Miki, Keisuke; Toneyama Medical Center, 5-1-1 Toneyama, Toyonaka, Osaka, Japan
Nishijima, Ryosuke ;Sugisawa, Kenta; Nagata, Yuka;

BMC pulmonary medicine,2025 Dec 18

  • Background: Oxygen uptake (V’ O2 ) obtained from expiratory gas analysis is generally calculated using minute ventilation (V’ E ) and the inspired‒expired mean oxygen (O 2 ) concentration difference (ΔF O2 ) during cardiopulmonary exercise testing (CPET). We have reported that ΔF O2 , which is associated with ventilatory efficiency, is independent of V’ E at peak exercise and affects exercise tolerance in respiratory diseases other than idiopathic pulmonary fibrosis (IPF). We hypothesized that similar results are obtained in IPF, and that ΔF O2 is a prognostic factor for survival in IPF.
  • Methods: Forty-three patients with IPF, who underwent CPET with blood gas analysis were enrolled from our database.
  • Results: At peak exercise, ΔF O2 was strongly correlated with variables related to ventilatory efficiency, i.e., V’ E /carbon dioxide output (V’ CO2 ) ratio at the nadir during exercise (r=‒0.91) and correlated well with peak V’ O2 (r = 0.67), but it was independent of V’ E (r = 0.24) at peak exercise. Two multivariate Cox proportional hazards models with adjustment for age, including the previously reported prognostic factors, showed that ΔF O2 at peak exercise was a stronger predictor of survival than (1) peak V’ O2 , V’ E at peak exercise in a first analysis (hazard ratio: 0.195, 95% CI 0.070 to 0.500; p = 0.0005) and (2) than tidal volume at peak exercise, body mass index, and arterial oxygen tension (PaO 2 )-slope, i.e., the decrease in PaO 2 per the increase in V’ O2 during exercise in a second analysis (hazard ratio: 0.437, 95% CI 0.201 to 0.958; p = 0.0389).
  • Conclusions: These results show that ∆F O2 at peak exercise, which is correlated with ventilatory efficiency related to carbon dioxide clearance, is independent of ventilatory ability and is a stronger prognostic factor for survival than physiological ventilatory impairments with hypoxemia in IPF. CPET is essential for evaluating exercise alveolar O 2 extraction and guiding the optimal management of patients with IPF.