Preoxygenation and Anesthesia: A Detailed Review

Initiation of preoxygenation prior to anesthetic induction and tracheal intubation is a commonly recognized technique intended to boost oxygen reservoirs in the body and thus slow the progression of desaturation of arterial hemoglobin at times of apnea. Even though challenges associated with ventilation and intubation are inconsistent, it is preferable for all patients to necessitate preoxygenation. The effectiveness of preoxygenation is measured by its performance and efficiency. Determinant factors of efficacy indices include rises in the alveolar O2 fraction (FAO2), reductions in the alveolar nitrogen fraction (FAN2), and improvements in the arterial O2 stress (PAO2). The effectiveness or efficiency of preoxygenation during apnea is evaluated from the declining trend in level of oxyhemoglobin desaturation (SAO2). The maximal risk associated with preoxygenation generally comprises delayed diagnosis of oesophageal intubation, absorption atelectasis, generation of reactive oxygen species, and incidences of adverse hemodynamic results. Since the time of preoxygenation is minimal, there are limited hemodynamic effects and the aggregation of reactive oxygen species to counteract its effectiveness. In general, three methods of preoxygenation techniques are followed for the routine procedures, namely, deep breathing, rapid breathing at fraction of inspired oxygen (FiO2) of 1 for two to five minutes, and the four vital capacities method. Health professionals, especially anesthesiologists specialized in Ear Nose and Throat (ENT) and traumatology, must be empowered by alternative methods like trans-tracheal ventilation to resolve life-threatening medical emergencies. Equipment accessibility and needful training are two essential components that are recommended for significant preparedness. The present article reviews the advantages conferred by the preoxygenation techniques with special attention to the high-risk population. It also details the inadequacies and the risks associated with the preoxygenation technique.