Low-flow oxygen delivery in patients with disturbed consciousness

Background: When low-flow oxygen (O2) delivery is required, a nasal cannula is commonly used. However, no reports have described arterial blood gas analysis in actual patients receiving O2 simultaneously through a mask and a nasal cannula. Methods: This prospective observational study included 110 patients with disturbed consciousness due to brain damage. Arterial lines were inserted in all patients for blood pressure monitoring, and arterial blood was collected through the line. Arterial O2 saturation (SaO2) and partial pressures of O2 (PO2) and carbon dioxide (PCO2) were measured while patients received O2 at flow rates of 1, 2, and 3 L/min through either a mask or a nasal cannula. Results: SaO2 was significantly higher with a mask than with a nasal cannula when O2 was delivered at 2 and 3 L/min ( p < 0.01). PO2 was significantly higher with a mask at 1, 2, and 3 L/min; however, PCO2 did not differ significantly among room air, nasal cannula, and mask O2 delivery. In O2 administration of 1, 2, and 3 L/min, no significant differences in PO2 or PCO2 were identified between closed-mouth and open-mouth breathing with either a mask or a nasal cannula. Discussion: Low-flow O2 delivery through a mask provides better oxygenation in comatose patients. For patients with decreased PO2 levels, low-flow O2 administration using a mask is more effective in increasing PO2 than using a nasal cannula, regardless of closed- or open-mouth breathing; however, one drawback is that the mask must be temporarily removed during oral care and suctioning procedures.