Peri-intubation oxygenation techniques to minimize the degree of hypoxia in patients with hypoxemic respiratory failure in intensive care unit.

Patients admitted to Intensive care units(ICUs) with hypoxemic (Type I) respiratory failure often require respiratorysupport in the form of intubation and mechanical ventilation. Drop in SpO2 to below 70% (Critical hypoxia) whileperforming intubation increases the risk of arrhythmias, hemodynamiccompromise, hypoxic brain injury and death1.  Securing the airway rapidly without criticalhypoxia or aspiration is often a challenge for intensivists. Moreover the marginof safety for desaturation is lesser with critically ill patients when comparedto patients without pre-existing hypoxia.

Preoxygenation is the standard recommendation before intubating patientsin ICU because of the following reasons:

1.     Preoxygenationallows a safety buffer during period of intubation. It extends the duration of“Safe apneaâ€, defined as the time until a patient reaches a saturation of88-90%, to allow for placement of a definitive airway.

2.      Rapid sequence induction (RSI) has beencommonly employed in ICU, taking into account the high risk of aspiration ofgastric contents in these patients2.

Several Preoxygenation techniques have beendeveloped to prevent or limit the risk of desaturation during intubation. Non-invasiveventilation (NIV) for preoxygenation of patients with acute hypoxemicrespiratory failure is associated with less hypoxemia when compared topreoxygenation with a traditional face mask with reservoir bag3.However, NIV mask has to be taken off after preoxygenation in order to performorotracheal intubation. The hypoxemic patient doesn’t receive oxygen duringthis period, precipitating rapid desaturation, especially in patients withdifficult airway.

“Apneic oxygenation†has been described which allows continuedoxygenation during the period of apnea. Apneic oxygenation extends the durationof safe apnea when used after administration of sedatives or muscle relaxants.Many strategies have been developed to provide apneic oxygenation such as NODESAT (nasal oxygen during efforts securing a tube) using a nasal cannula setat 15 L/min, THRIVE (Trans-nasal humidified rapid-insufflation with ventilatoryexchange) using a high flow nasal cannula at 60 L/min4

Though apneic oxygenation can be providedwith nasal cannula, a patent airway is required for oxygen to reach the hypopharynx and be entrained into the trachea. A nasopharyngeal airway canaccomplish this airway patency especially in patients with obesity andObstructive sleep apnea. Furthermore, studies have shown that HFNC (High FlowNasal Cannula) oxygen therapy generates a flow dependant positive airwaypressure by increasing end-expiratory lung volume, suggesting a possibleassociated alveolar recruitment.

Nasopharyngeal airway as a means to allow apneic oxygenation and toenhance the continued positive airway pressure (CPAP) thereby promotingalveolar recruitment, has not been assessed and the possible benefits oversimple nasal cannula with 15 L/min O2 flow for apneic oxygenation has to be established.

Therefore we undertake this study to compare whether providing CPAP through  Nasopharyngeal airway as a means of apneic oxygenation is effective when compared to traditional means of apneic oxygenation using Nasal prongs at 15 L/min while intubating hypoxic patients in ICU.