Background: Patients often receive IV sedation and O2 via a nasal cannula (NC) during monitored anaesthesia care (MAC). Over-sedation or airway obstruction may cause severe desaturation, especially in obese patients with obstructive sleep apnea (OSA). A simple nasal CPAP mask assembly has been shown to maintain spontaneous respiration and improve oxygenation in deeply sedated OSA patients.1-3 We report its use in a morbidly obese OSA patient with difficult airway and severe cardiopulmonary diseases during cystoscopy. 

Case Report: A 37 y/o morbidly obese male (BMI 62 kg/m2) with Class IV airway, OSA, pulmonary HTN, CHF, CAD, COPD/asthma requiring home NC O2 (4 L/min)presented for cystoscopy, utereroscopy and laser lithotripsy for urethral stone. Due to patient´s severe cardiopulmonary diseases and physical habitus, the procedure was to proceed under MAC with difficult airway intubation equipment standby. His O2 saturation (Sat) was 87% with NC 4 L O2/min and would decrease with any change from sitting position. With patient lying supine, an infant mask with fully inflated air cushion was placed over his nose and secured with head straps and connected to anaesthesia breathing circuit/machine with 12 L/min O2 and 5-6 cm H2O CPAP. His O2 Sat increased to 92%. 

He then received midazolam (2 mg) and fentanyl (50 mcg x 2). During the following 2 ½ hour procedure, he was maintained on conscious sedation titrated with ketamine (total 80 mg), dexmedetomidine (total 139 mcg) and a propofol infusion (40 mcg/kg/min for 25 min). He also received IV acetaminophen (1 g). He maintained spontaneous respiration and his O2 Sat mid 80's%. He tolerated the procedure well without any complication. He was doing well with facial CPAP in the PACU. He was elated that endotracheal intubation was avoided and gave consent for photography and case report. After a brief period on facial CPAP, he received his routine NC O2 supplement. He was discharged home without any problem. 

Discussion: This simple nasal CPAP assembly maintained spontaneous respiration and prevented severe desaturation in a morbidly obese patient with a difficult airway, OSA and severe cardiopulmonary diseases under procedure sedation. It may improve patient safety. 

Ref: 1. www.tsemask.com; 2. SAMBA 28th AM, 2013; 3. IARS AM: MCC1080, 2015 
Learning Points: How to prepare a nasal mask assembly and how to provide CPAP in obese OSA patients and assisted nasal ventilation in deeply sedated patients with airway obstruction.

A novel nasal CPAP mask assembly maintained spontaneous respiration and improved oxygenation in a morbidly obese patient with OSA, difficult airway and severe cardiopulmonary diseases under MAC during cystoscopy