Predictors for P_aO₂ and Hypoxemic Respiratory Failure in COPD–A Three-Year Follow-up

Abstract

Background: Knowledge about predictors for developing hypoxemia in the course of chronic obstructive pulmonary disease (COPD) progression is limited. The objective of the present study was to investigate predictors for overall P_aO₂, for a potential change in P_aO₂ over time, and for first occurrence of hypoxemia. Methods: 419 patients aged 40–76 years with COPD GOLD stages II-IV underwent clinical and pulmonary function measurements, including repeated arterial blood gases over three years. Airway obstruction, lung hyperinflation, markers of systemic inflammation and cardiovascular health, exacerbation frequency, smoking habits, and body composition were tested as possible predictors of P_aO₂ and first episode of hypoxemia. Results: In multivariate adjusted longitudinal analyses, forced expiratory volume in 1 second, total lung capacity and functional residual capacity (all in% predicted), resting heart rate and fat mass index were all associated with overall P_aO₂ (all P < 0.005). We found no change in P_aO₂ over time (ρ = 0.33), nor did we find evidence that any of the tested variables predicted change in P_aO₂ over time. In multivariate adjusted survival analyses, functional residual capacity and resting heart rate were predictors of episodic hypoxemia (both ρ < 0.005). Conclusions: This longitudinal study identified pulmonary, cardiac and metabolic risk factors for overall P_aO₂ and episodic hypoxemia, but detected no change in P_aO₂ over time.

Keywords: :

• arterial blood gases
• longitudinal study
• lung function
• risk factor