摘要：Background: Supplemental O 2 is often administered without knowledge of CO 2 levels for patients with ventilatory pump failure (VPF). This can render oximetry ineffective as a gauge of alveolar ventilation, airway secretions, and lung disease. We have noted that diurnal hypoventilation with hypercapnia tends to be symptomatic when O 2 saturation levels decrease below 95% and patients extend sleep noninvasive ventilatory support (NVS) into daytime hours. We also noted that with advancing age, less hypercapnia results in desaturation. This study was designed to explore oxyhemoglobin desaturations (O 2 desats) as a function of age and hypercapnia for patients with VPF. Methods: A retrospective analysis of 8933 consecutive patient visits for whom end-tidal CO 2 and O 2 sats were measured. O 2 sats 50 cmH 2 O were the most significant including for visit-ages < 30 and ≥ 30 years. There was a statistically significant 4% decrease in the odds of O 2 desat for every one-year increase in age to age 30 (OR = 0.96, 95% CI = [0.93, 0.99], p = 0.02) and for visit-ages ≥ 30 a significant 30% increase in the odds of O 2 desat for every 10-year increase in age (OR 1.3, 95% CI = [1.1, 1.6], p = 0.006). Relationship for ages ≥ 30 years were also significant for CO 2 levels over 45 mmHg also. 40% of the time when CO 2 was greater than 45 mmHg O 2 sat was low. Discussion: This study demonstrated a significantly lower risk of O 2 desat occurring at EtCO 2 levels ≥ 50 mmHg for patients from 10 to 20 years of age than those younger than 10 and a significantly greater risk of O 2 desat for 10 years intervals after age 20. Thus, with age, less hypercapnia results in desats and dyspnea with patients tending to extend NVS into daytime hours. This may be due to increases in physiological shunting, decreased pulmonary elasticity, and worsening ventilation/perfusion ratios with age.
