Pharyngeal oxygen administration increases the time to serious desaturation at intubation in acute lung injury: an experimental study

Abstract

Introduction: Endotracheal intubation in critically ill patients is associated with severe life-threatening complications in about 20%, mainly due to hypoxemia. We hypothesized that apneic oxygenation via a pharyngeal catheter during the endotracheal intubation procedure would prevent or increase the time to life-threatening hypoxemia and tested this hypothesis in an acute lung injury animal model.

Methods: Eight anesthetized piglets with collapse-prone lungs induced by lung lavage were ventilated with a fraction of inspired oxygen of 1.0 and a positive end-expiratory pressure of 5 cmH2O. The shunt fraction was calculated after obtaining arterial and mixed venous blood gases. The trachea was extubated, and in randomized order each animal received either 10 L oxygen per minute or no oxygen via a pharyngeal catheter, and the time to desaturation to pulse oximeter saturation (SpO2) 60% was measured. If SpO2 was maintained at over 60%, the experiment ended when 10 minutes had elapsed.

Results: Without pharyngeal oxygen, the animals desaturated after 103 (88-111) seconds (median and interquartile range), whereas with pharyngeal oxygen five animals had a SpO2 > 60% for the 10-minute experimental period, one animal desaturated after 7 minutes, and two animals desaturated within 90 seconds (P < 0.016, Wilcoxon signed rank test). The time to desaturation was related to shunt fraction (R2 = 0.81, P = 0.002, linear regression); the animals that desaturated within 90 seconds had shunt fractions >40%, whereas the others had shunt fractions <25%.

Conclusions: In this experimental acute lung injury model, pharyngeal oxygen administration markedly prolonged the time to severe desaturation during apnea, suggesting that this technique might be useful when intubating critically ill patients with acute respiratory failure.

Figure 1

Outline of the experiment. The arrows above the horizontal line indicate measurements, whereas the arrows below the line indicate interventions. The two periods were randomized during which pharyngeal oxygen was or was not administered. Crs, compliance of the respiratory system; FiO2, fraction of inspired oxygen.

Figure 2

Arterial oxygen tension (PaO₂) versus time of apnea without (upper panel) and with (lower panel) pharyngeal oxygen administration. The symbols and lines depict the individual values.

Figure 3

Time to desaturation below 60% as estimated by pulse oximetry versus shunt fraction on pharyngeal oxygen administration. The dots depict the individual values.