title: Oxygen desaturation during a 6 min walk test is a sign of nocturnal hypoxemia.
abstract: BACKGROUND⁄
  
  
  OBJECTIVE
  Patients with chronic obstructive pulmonary disease (COPD) may experience sleep disordered breathing with nocturnal desaturation. An exploratory study was performed to determine whether any commonly measured clinical parameters were useful in predicting nocturnal desaturation in patients with COPD. A validation study was subsequently performed to confirm the utility of the parameter identified in the exploratory study as most useful in this regard.
  
  
  METHODS
  A total of 103 (exploratory cohort) and 200 (validation cohort) consecutive patients with COPD admitted for pulmonary rehabilitation were evaluated. Standard outcome measures including nocturnal oximetry and the 6 min walk test (6MWT) on room air with continuous pulse oximetry were assessed. Patients with sleep apnea or those undergoing long-term oxygen therapy were excluded.
  
  
  RESULTS
  In the exploratory study, the mean (± SD) patient age was 70 ± 9.9 years, with forced expiratory volume in 1 s of 0.76 ± 0.34 L, which was 36 ± 16% of predicted. Body mass index, arterial oxygen tension, oxygen saturation by pulse oximetry at rest and during the 6MWT all demonstrated significant correlations with percentage of time spent with a saturation <90%. When the lowest pulse oximetry during the 6MWT was ≤88%, 10 of 21 patients demonstrated a saturation <90% for at least 30% of sleep time. This measure yielded a positive likelihood ratio of 3.77 (95% CI 1.87 to 7.62) compared with those who did not reach this threshold value. The validation study confirmed similar detection characteristics.
  
  
  CONCLUSIONS
  Results from the present study suggest that monitoring oxygen saturation changes during a 6MWT is useful in helping to identify COPD patients who may experience significant nocturnal desaturation.
authors.affiliation: Research Department, Mount Sinai Hospital Center, Montreal, Quebec, Canada.
authors.forename: Adrienne S
authors.initials: AS
authors.lastname: Scott
authors.forename: Marcel A
authors.initials: MA
authors.lastname: Baltzman
authors.forename: Ryan
authors.initials: R
authors.lastname: Chan
authors.forename: Norman
authors.initials: N
authors.lastname: Wolkove
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005080:Exercise Test; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000150:complications*; D012891:Sleep Apnea Syndromes / Q000097:blood / Q000150:complications*; D016138:Walking
chemical_list: D010100:Oxygen