[Increased inspiratory oxygen fractions (FIO2) using a conventional drug delivery nebuliser]

Nebulised drugs are very useful in COPD exacerbations. The most frequently used propellant is compressed air, which is commonly administered together with nasal oxygen in those patients with respiratory failure. The purpose of this approach is to avoid the risks inherent in breathing high inspiratory oxygen fractions (FIO(2)).

To analyze the actual FIO(2) obtained with such a common method under experimental conditions.

Volunteers breathed using different patterns (quiet breathing, panting and deep breathing), through either the nose or the mouth, with oxygen flows of 0 vs. 4l/min. Then, they repeated quiet breathing and panting patterns, with nebulization of saline propelled by compressed air (8l/min) and oxygen flows of 0, 2, 4, 6 and 8l/min. The F(I)O(2) was simultaneously determined both in retronasal (RN) and retropharyngeal (RF) areas.

During breathing without simultaneous nebulization and oxygen flow of 4l/min, FIO(2) reached mean values of 0.42-0.71 (RN) and 0.29-0.38 (RF) for the three ventilatory patterns analyzed. With nebulisations during quiet breathing, mean FIO(2) values were 0.39 (RN) and 0.27 (RF) for 2l/min O(2) flow, 0.47 (RN), 0.34 (RF) for 4l/min, 0.58 (RN), 0.38 (RF) for 6l/min, and 0.68 (RN) and 0.50 (RF) for 8l/min. Similar results were obtained with the panting pattern.

The FIO(2) obtained using the conventional nebulization system (propulsion with compressed air and simultaneous nasal oxygen therapy) are relatively high, and therefore, might involve risks for COPD patients during exacerbations.