Oxygen therapy during exacerbations of chronic obstructive pulmonary disease

Venturi masks (VMs) and nasal prongs (NPs) are widely used to treat acute respiratory failure (ARF) in chronic obstructive pulmonary disease (COPD), In this study, these devices were compared in terms of their potentiality to worsen respiratory acidosis and their capacity to maintain adequate (>90%) arterial oxygenation (Sa,O-2) through time (similar to 24 h), In a randomized cross-over study, 18 consecutive COPD patients who required hospitalization because of ARF were studied. After determining baseline arterial blood gas levels ton room air), patients,were randomized to receive oxygen therapy through a VM or NPs at the lowest possible inspirators oxygen fraction that resulted in an initial Sa,O-2 of greater than or equal to 90%. Arterial blood gas levels were measured again 30 min later ton O-2), and Sa,O-2 recorded using a computer during the subsequent similar to 24 h, Patients ffere then crossed-over to receive O-2 therapy by means of the alternative device O-2 or VM), and the same measurements obtained again in the same order. It was observed that both the VM and NPs improved arterial oxygen tension (p < 0.0001) to the same extent (p=NS),without any significant effect upon arterial carbon dioxide tension or pH, However, despite this adequate initial oxygenation, St,ol was <90% for 3.7+/-3.8 h using the VM I and for 5.4+/-5.9 h using NPs (p<0.5), Regression analysis shelved that the degree of arterial hypoxaemia (p<0.05) and arterial hypercapnia (p<0.05) present before starting O-2 therapy and, particularly, the initial Sn,oz achieved after initiation of O-2 therapy (p<0.0001) enabled the time tin h) that patients would be poorly oxygenated (Se,O-2 <90%) on follow-up to be predicted. These findings suggest that, in order to maintain an adequate (>90%) level of arterial oxygenation in patients with chronic obstructive pulmonary disease and moderate acute respiratory failure: 1) the initial arterial oxygen saturation on oxygen should be maximized whenever possible by increasing the inspiratory oxygen fraction; 2) this strategy seems feasible because neither the VM nor NPs worsen respiratory acidosis significantly; and 3) the Venturi mask (better than nasal prongs) should be recommended.