Background: Patients under regional block or local anaesthesia often receive IV sedation and nasal cannula O2. Over-sedation or airway obstruction may cause severe desaturation, especially patients in beach chair position. A simple nasal TSE-PAP mask assembly was shown to maintain spontaneous ventilation and improve oxygenation in sedated obese patients with OSA(1-3). We used it to provide nasal CPAP and N2O for a patient with autonomic neuropathy during shoulder arthroscopy under local anaesthesia. 
Case Report: A 68 y/o female with autonomic neuropathy associated with severe HTN lability presented for arthroscopic biopsy of infected right shoulder resulting from two failed rotator cuff repairs. She had failed attempts at both medical antihypertensive treatment, due to profound hypotension, and two medullary decompressive surgeries in an effort to relieve her dysautonomia. 

She did well with recent arthroscopic I & D of the shoulder under interscalene block with a nasal CPAP mask assembly providing 50% N2O. However, she complained of PONV. She gave consent for case report. Her pre-operative BP was in 220's/130's and HR in 130's which improved (BP 196/125, HR 112) with midazolam (2 mg). 

An infant mask with a fully inflated air cushion was secured over her nose with rubber head straps and connected to the anesthesia machine via a long breathing circuit (Fig. 1-2). APL valve was adjusted to deliver 6 cm H2O CPAP with 2 L O2/min and 2 L N2O/min (Fig. 3). Initially, her BP briefly dropped to 90's/60's which were corrected with phenylephrine/ephedrine and decreasing propofol infusion from 100 to 25-50 mcg/kg/min. She maintained spontaneous ventilation and 100% SpO2 throughout the procedure.

She tolerated the procedure well with 2 x 25 mcg fentanyl and IV 1 gm acetaminophen. She maintained stable BP (130-170/80-110) and HR (80-100). 
 
She was elated that she had no PONV and requested again the same anaesthesiologist for her shoulder repair in the future. She was discharged home without complication. 
Discussion: This simple nasal TSE-PAP mask assembly maintained spontaneous ventilation, oxygenation and stable hemodynamics in a patient with autonomic neuropathy in beach chair position under local anaesthesia and sedation. It may improve patient safety at a low cost. 

Ref: 1) www.TSEMASK.com, 2) SAMBA 28th AM, 2013, 3) SAM AM (MC), 2014 
Learning Points: How to prepare a nasal mask assembly using existing anaesthesia equipment and to provide nasal CPAP to maintain spontaneous ventilation in a beach chair position.

Repeated use of a novel nasal PAP mask assembly to maintain spontaneous ventilation and oxygenation in a patient with autonomic neuropathy for arthroscopic biopsy of recurrent shoulder joint infection under local anaesthesia