title: Low inspiratory capacity to total lung capacity ratio is a risk factor for chronic obstructive pulmonary disease exacerbation.
abstract: BACKGROUND
  Air trapping because of chronic obstructive pulmonary disease (COPD) leads to a reduction in inspiratory capacity/total lung capacity (IC/TLC) ratio. We hypothesize that COPD patients with a low IC/TLC ratio suffer more frequent COPD exacerbations.
  
  
  METHODS
  Retrospective cohort study of patients with COPD, aged 30 years or older with forced expiratory volume in 1 second <70% predicted and forced expiratory volume in 1 second/forced expiratory volume (FEV1/FVC) ratio <70% treated in our ambulatory care clinic for 3 years (2003-2006). Patients were divided in 2 groups, either IC/TLC ratio less than or greater than 25%.
  
  
  RESULTS
  Charts of 350 patients with COPD were reviewed. Of the 77 patients who met inclusion criteria, 28 patients (20 women and 8 men) had IC/TLC ratio <25% (low group) and 49 patients (25 women and 24 men) had IC/TLC ratio >25% (high group). Average number of exacerbations per person in the low group was 3.5 (0-10), significantly higher than in the high group, which was 2.2 (0-10; P = 0.01). Visits for COPD exacerbations were analyzed based on treatment site namely, office, emergency room (ER), and hospital. The per person office visits were 1.96 (0-10) in the low group and 0.80 (0-3) in the high group (P = 0.002). ER visits were similar, 0.57 (0-3) in the low group and 0.38 (0-3) in the high group (P = 0.15), as were hospital visits, 0.96 (0-8) in the low group and 1.06 (0-5) in the high group (P = 0.81).
  
  
  CONCLUSIONS
  COPD patients in the low group experienced significantly more unscheduled office visits because of exacerbations, suggesting they need early identification and closely monitored therapy.
authors.affiliation: Department of Medicine, Marshall University, Joan C. Edwards School of Medicine, Huntington, West Virginia, USA. zaman@marshall.edu
authors.forename: Mumtaz
authors.initials: M
authors.lastname: Zaman
authors.forename: Syed
authors.initials: S
authors.lastname: Mahmood
authors.forename: Abdullah
authors.initials: A
authors.lastname: Altayeh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012189:Retrospective Studies; D012307:Risk Factors