Background and goal of study: Preoxygenation results in denitrogenation of the functional residual capacity (FRC) of the lungs, leading to an increase in oxygen reserve and delayed onset to hypoxia during apnoea [1, 2]. The study focuses on the relationship between CRF and duration of apnoea after maximal nitrogen washout.
Materials and methods: Three groups of patients were included after Ethical Committee approval: 7 healthy, 9 chronic obstructive pulmonary disease (COPD), and 6 mild to moderate obese patients. Each subject underwent preoxygenation which consists of 3 min of tidal volume using an oxygen flow of 10 L min−1, followed by rapid sequence induction of general anaesthesia and manual ventilation. The end-points of preoxygenation were defined as FEO2 > 0.90; FEN2 inferior to 5% (RAM spectrometer). After endotracheal intubation, the patients were allowed to remain apnoeic until SPO2 reached 93%. Variables registered: demography, duration (min) of preoxygenation and of apnoea, FRC real/FRC theoretical (%). ANOVA.
Results and discussion: *P < 0.05 compared with healthy. TABLE
Conclusion: FRC should be assessed preoperatively if difficult endotracheal intubation is suspected, to inform on the duration of safe apnoea.
1 Archer GW. Br J Anaesth
2 Norris MC. Anesthesiology
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