Safety Study of Continuous Positive Airway Pressure Via a Nasal Mask

Effect of Continuous Positive Airway Pressure Ventilation Through Nasal Mask on Upper Airway Patency During Induction of Anesthesia

Upper airway obstruction (UAO) is common complication during induction of general anesthesia. The mechanism of UAO during anesthesia has not been well understood. Posterior displacement of soft palate are believed to be the primary contributing factors. The mechanism of UAO during anesthesia share many similarities with obstructive sleep apnea (OSA). Since nasal continuous positive airway pressure (nCPAP) can maintain the airway patent in patients with OSA, the investigators hypothesize that nCPAP during induction of anesthesia will reduce the incidence and severity of UAO.

Inclusion Criteria:

Patients,between 18-65 years of age meeting ASA physical status classification I-II requiring general anesthesia for elective surgery who are able to breathe through both their nose and mouth while awake.

Exclusion Criteria:

1. Patients with major cardiovascular disease, respiratory disease, cerebral vascular disease or American Society of Anesthesiologists physical status class III or greater.
2. Abnormal vital signs on the day of admission for surgery [heart rate (HR, > 100 bpm or < 40 bpm), blood pressure (BP, > 180/100 mmHg or < 90/60 mmHg), room air transcutaneous oxyhemoglobin saturation (SPO2) < 96%] that are not correctable with his or her routine medication or commonly used pre-operative medication.
3. Unable to open mouth (< 2.5 cm) or unable to breathe through their mouth or nose.
4. Subjects with a beard, an abnormal facial structure or other factors precluding obtaining a viable face mask fit without air leak. Also, subjects having claustrophobia that can not tolerate the mask.
5. Any person with an anticipated difficult airway. This will include subjects who require or may require either a fiberoptic intubation or intubation while awake and subjects with known OSA or body mass index (BMI) greater than 35 km/m2.
6. Gastric-esophageal reflex or a full stomach.
7. The subject has remained in bed for more than 24 hours.
8. Neurological symptoms associated with neck extension, a neurological deficit from a previous stroke or spinal cord injury, a recent stroke or transient ischemic attack (TIA) within 2 weeks.
9. Pregnant women and women less than one month post-partum. Ruling out pregnancy will be conducted by careful history and physical examination as performed routinely prior to surgery. If the history is believed to be unreliable, the patient will be excluded unless a pregnancy test is performed and the result of the test is negative.
10. Emergency cases and subjects who have not adhered to the ASA NPO (Nil Per Os) guidelines.