Rapid sequence induction (RSI) is the administration of an anesthesia induction agent followed immediately by a paralytic agent prior to insertion of an endotracheal airway (Reynolds & Heffner, 2005). Oxygen desaturation is considered one of the most frequently occurring complications of endotracheal intubation (ETI) after administration of RSI agents. Following administration of a paralytic agent, there is a period of apnea while the provider utilizes a laryngoscope in an attempt to pass an endotracheal tube through the trachea. It is during this period of time that oxygen saturation levels rapidly decline. The current standard of practice includes pre-oxygenation by use of a non-rebreather mask (NRB) at 15 liters per minute (L/min), …show more content…
During the normal process of ventilation, gasses flow through the trachea into the alveoli where diffusion occurs. At the level of the alveoli, oxygen diffuses into the alveolar capillaries where it attaches to the hemoglobin molecule while carbon dioxide (CO2) diffuses into the alveoli where it is expelled during exhalation. The hemoglobin molecule then transports the oxygen through the blood to vital organs and tissue. A pressure gradient exists between the alveolus and the capillaries, which facilitates this diffusion of oxygen into the capillaries (Andreoli & Cecil, …show more content…
A lack of inspiratory effort reduces the movement of these gasses into and out of the lungs, resulting in hypoxia. When supplemental oxygen is applied to the apneic patient, the pressure gradient facilitates the movement of oxygen to the alveoli and into the capillaries. This increases the amount of time before the apneic patient becomes hypoxic. However, the elimination of CO2 is reliant upon alveolar ventilation. Over an extended period of time, this build up of CO2 will result in an uncompensated respiratory acidosis (Frumin et al., 1959).
One potential side effect of delivering high levels of oxygen to the apneic patient is the resultant washout of nitrogen from the respiratory system, which is needed to prevent alveolar collapse. In order for apneic oxygenation to be effective, the alveoli must be patent, with minimal atelectasis to prevent the deleterious effects of shunting. Utilization of a HFNC, which has the ability to provide a small amount of positive end-expiratory pressure (PEEP), may counteract this process by keeping the alveoli patent while providing supplemental oxygen to the apneic patient (Weingart, 2011).