Nocturnal desaturation

Michelet P, Guervilly C, Helaine A, et al. Adding ketamine to morphine for patient-controlled analgesia after thoracic surgery influence on morphine consumption, respiratory function, and nocturnal desaturation. Br JAnaesth 2007 99 396-403. 

Therefore, in symptomatic patients with daytime normocapnia but significant nocturnal desaturation (Sao2 < 90% for >10% total sleep time, or mean REM Sa02 < 90% and minimum Sa02 < 90% or Sao2 < 88% for 5 consecutive minutes), NIV is warranted (3). 

It seems reasonable to start NIV in symptomatic patients (Table 2) who have signs of respiratory muscle weakness (FVC <80% predicted or SNIP < 40 cmH20) and evidence of nocturnal desaturation or a Paco2 > 49 mmHg (18). Bourke et al. suggested that orthopnea was the most useful criterion for benefit and compliance with NIV (94), and Sivak (96) noted lack of correlation between VC and the success of NIV. In a small prospective study, Jackson et al. (19) suggested that early intervention with NIV, based on nocturnal desaturation (Sao2 < 90% for 1 min), may improve quality of life. 

Oxygen alone, although preventing the nocturnal desaturation, often results in unacceptably high levels of Pcx>2. Diuretics and tracheostomy alone, although providing a temporary improvement, will at best delay the need for mechanical ventilatory support. 

Neumann C, Martinez D, Schmid H. Nocturnal oxygen desaturation in diabetic patients with severe autonomic neuropathy. Diabetes Res Clin Pract 1995 28 97-102. 

---