title: Exercise-induced desaturation in patients with chronic obstructive pulmonary disease on six-minute walk test.
abstract: OBJECTIVE
  Exercise-induced desaturation (EID) is associated with increased mortality in chronic obstructive pulmonary disease (COPD). However, the relationship of EID with anthropometric and clinical parameters of resting pulmonary function test and six-minute walk test (6MWT) in COPD remains unclear. The study was designed to assess the correlate of EID and to identify various possible predictors of EID in stable normoxemic patients of COPD.
  
  
  METHODS
  Sixty patients with stable COPD diagnosed and staged as per the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines underwent 6MWT. A drop in standard pulse oximetry (SpO2) of ≥4% or nadir up to ≤88% was defined as EID. Based on EID during 6MWT, two groups were formed: desaturators (DS) and nondesaturators (NDS). DS and NDS were compared for baseline and clinical characters by the Student's t-test while Pearson and Spearman rho correlation coefficient assessed strength of the association of anthropometric and clinical variables with EID. The predictors of EID were identified by logistic regression and receiver operator curve analysis.
  
  
  RESULTS
  Out of 60 patients with stable COPD, 33 patients desaturated on exercise (n = 33/60). DS had significantly lower values of FEV1 (P < 0.001), FVC (P < 0.01) FEV1/FVC (P < 0.01) compared to NDS. EID had significant negative correlation with FEV1 (r = 0.31, P < 0.01), resting oxygen saturation (r = 0.549, P < 0.001) and 6MWD (r = 0.511, P < 0.001). Resting SpO2 ≤93% was found to a predictor of EID with a sensitivity and specificity of 83% and 78%, respectively.
  
  
  CONCLUSIONS
  The 6MWT is a safe and sensitive test to recognize EID in normoxic stable COPD patients. Resting oxygen saturation is a good predictor of EID.
authors.affiliation: Department of Physiology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India.
authors.forename: Archana Chauhan
authors.initials: AC
authors.lastname: Dogra
authors.affiliation: Department of Physiology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India.
authors.forename: Urmil
authors.initials: U
authors.lastname: Gupta
authors.affiliation: Department of Pulmonary Medicine, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India.
authors.forename: Malay
authors.initials: M
authors.lastname: Sarkar
authors.affiliation: Department of Physiology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India.
authors.forename: Anita
authors.initials: A
authors.lastname: Padam
keywords: 6-minute walk test; Chronic obstructive pulmonary disease; exercise-induced desaturation; predictors