9. Monitoring, oxygen and positive airway pressure therapy for obese patients with sleep apnea

#### 9.1. Monitoring

Oxygen saturation and respiratory rate should be closely monitored in these group of patients receiving opioids or other potentially sedative medications [88]. For continuous assessment of the adequacy of ventilation in the postoperative setting, end-tidal CO2 measurement has become the standard of care [89, 90]. End-tidal CO2 detects hypoventilation earlier than any other physiological monitors. OSA patients at high risk should be continuously monitored with pulse oximetry until patient maintains oxygen saturation to their preoperative baseline levels [91, 92]. Studies have shown that pulse oximetry monitoring in postoperative patients is very useful in detecting hypoxemic episodes [40, 93].

#### 9.2. Oxygen therapy

Obese patients with suspected or confirmed OSA should be transferred with supplemental oxygen from operation room to the post-anesthesia care unit (PACU) after receiving general anesthesia. In the PACU, patient head end elevation by at least 30 degrees is recommended. Though there is not enough literature that shows the effect of supplemental oxygen in postoperative settings, the recommendation is that supplemental oxygen should be continued in all postoperative OSA patients until they maintain preoperative (baseline) oxygen saturation on room air [91].

#### 9.3. Positive airway pressure therapy

Use of CPAP in PACU is recommended for OSA patients who were using it preoperatively at home and also when patients get frequent attacks of airway obstruction in the recovery room [91, 94]. It should also be continued on the inpatient units. CPAP has shown to reduce the incidences of apnea and hypopnea episodes when compared to the preoperative baseline. CPAP is associated with improved ventilation in postoperative OSA patient and also it has shown reduced hospital stay [95–97].

Patients who receive long-acting opioids should be monitored closely and may need high dependency unit admission for postoperative monitoring. Indications for obese patients with OSA for HDU or ICU admission are preexisting co-morbidities, limited functional capacity, major surgery, poorly controlled OSA requiring systemic opioids. The patient should be discharged to the unmonitored settings only when adequate oxygen saturation is maintained to baseline level on room air and with no more risk of respiratory depression (apnea or hypopnea) that can be determined ideally when the patient is asleep [91].
