In mechanically ventilated patients, disconnection from the ventilator and endotracheal suctioning can induce major arterial oxygen desaturation resulting from apnea, changes in inspired oxygen fraction, and decrease in lung volume. The aim of this study was to test the efficacy of a simple method of delivering oxygen and maintaining lung volume during this process. Our study was conducted in two parts. In the first part, constant-flow insufflation of oxygen (CFI) was used in seven patients ventilated for acute respiratory failure (Pa(O2)/FI(O2) = 347 +/- 33 mm Hg) as a means of maintaining arterial oxygenation during apnea and disconnection from the ventilator. CFI was administered via a modified endotracheal tube in which small capillaries allowed delivery of a high-velocity jet flow near te tracheal end of the tube during disconnection from the ventilator. In comparison to apnea alone, CFI prevented a fall in arterial oxygen tension (16 +/- 7 mm Hg during CFI versus 117 +/- 27 during apnea, after 90 s of disconnection in the two situations, p < 0.001), whereas it did not reduce the development of hypercapnia. The efficacy of CFI resulted both from the injection of oxygen into the trachea and from the maintenance of positive alveolar pressure induced by air entrainment (mean 10.4 +/- 1.1 cm H2O), preventing a fall in lung volume usually occurring after disconnection (+338 +/- 88 ml during CFI versus -344 +/- 64 ml during apnea, p < 0.01). In the second part of the study CFI was used to prevent arterial oxygen desaturation induced by endotracheal suctioning. In seven other patients who were sedated but not paralyzed (Pa(O2)/FI(O2) = 199 +/- 34 mm Hg), endotracheal suctioning was performed with or without administration of CFI. In five of the seven patients oxygen desaturation was fully prevented when CFI was used, but it was observed in all patients and reached -15.6 +/- 2.6% during standard suctioning. In the two remaining patients, desaturation was much lower and recovery time was much shorter when CFI was used. Measurements of transpulmonary pressure and lung compliance during these periods suggested that CFI was able to prevent a decrease in lung volume induced by suctioning. Assessment of lung volume by CT scanning in five patients demonstrated that CFI prevented the 27% fall in lung volume induced by endotracheal suctioning. We propose to use this simple method as a means to avoid or minimize arterial oxygen desaturation during disconnection from the ventilator or during endotracheal suctioning in severely hypoxemic patients ventilated for acute respiratory failure.
