title: Impact of overlap syndrome on severity of acute exacerbation of chronic obstructive pulmonary disease.
abstract: BACKGROUND
  The severity of exacerbation in chronic obstructive pulmonary disease (COPD) due to the overlap of obstructive sleep apnea syndrome (OSAS) is not known.
  
  
  OBJECTIVE
  To find out the 1) severity of acute exacerbation of COPD (AECOPD) in patients with overlap syndrome compared to only COPD, 2) prevalence of overlap syndrome in AECOPD, and 3) clinical characteristics of COPD compared to overlap syndrome.
  
  
  METHODS
  Fifty-one patients admitted with AECOPD were classified into; Mild exacerbation: Normal arterial blood gases (ABG) treated with antibiotics, Moderate: Normal ABG treated with parenteral corticosteroids, Severe: Type 1 respiratory failure, Very severe: Type 2 respiratory failure with normal pH and Life-threatening: Type 2 respiratory failure with pH <7.35. They were evaluated for OSAS with full polysomnography after the exacerbation subsided and analysed depending on presence or absence of overlap syndrome.
  
  
  RESULTS
  The majority of only COPD cases (26/38) had mild and moderate exacerbations whereas majority of overlap patients (9/13) had severe, very severe and life-threatening exacerbations (statistically significant, P = 0.021). Of 51 patients, 13 had OSAS i.e. the prevalence of overlap in AECOPD was 25.5%. The mean BMI in only COPD and overlap syndrome was 20.70 ± 8.03 kg/m(2) and 31.82 ± 5.80 kg/m(2) (P < 0.001), respectively. Metabolic syndrome was recorded in 2/36 (5.3%) patients in only COPD and 6/13 (46.2%) patients in overlap (P < 0.001).
  
  
  CONCLUSIONS
  Overlap syndromes are more likely have respiratory failure compared to only COPD during AECOPD. AECOPD have a high prevalence of OSAS. Overlap syndrome have significantly higher likelihood of obesity and metabolic syndrome compared to only COPD.
authors.affiliation: Department of Pulmonary Medicine, ESI-Post Graduate Institute of Medical Sciences and Research, Delhi, India.
authors.forename: Dipti
authors.initials: D
authors.lastname: Gothi
authors.affiliation: Department of Pulmonary Medicine, Era's Lucknow Medical College, Lucknow, Uttar Pradesh, India.
authors.forename: Shiv Sagar
authors.initials: SS
authors.lastname: Gupta
authors.affiliation: Department of Pulmonary Medicine, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
authors.forename: Nishith
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Department of Pulmonary Medicine, National Institute of Tuberculosis and Respiratory Disease, Delhi, India.
authors.forename: Kartik
authors.initials: K
authors.lastname: Sood
keywords: Acute exacerbation of COPD; metabolic syndrome; obesity; obstructive sleep apnea syndrome