A Study to Look at Day to Day Changes in Lung Function in COPD Subjects Taking Albuterol/Salbutamol and Ipratropium

• Variability in daily FEV1 [ Time Frame: 21 days ] [ Designated as safety issue: No ]
  Variability in daily FEV1, estimated by CV (coefficient of variation) and by half range (i.e. Half the difference between maximum and minimum) daily FEV1 values.
  
  

• FEV1 >= 12% and 200mL increase [ Time Frame: 21 days ] [ Designated as safety issue: No ]
  Proportion of days that subjects achieve >= 12% and 200mL increase in FEV1
  
  
• Maximal bronchodilator response (FEV1) [ Time Frame: 21 days ] [ Designated as safety issue: No ]
  The maximal bronchodilator response for the first administered agent (defined as the FEV1 1 hour post dose of the first bronchodilator minus the pre dose FEV1).
  
  
• FEV1 increase of 100mL, 200mL and 250mL [ Time Frame: 21 days ] [ Designated as safety issue: No ]
  Proportion of days for which a subject achieves a threshold increase from baseline in FEV1, using thresholds of 100mL, 200mL and 250mL
  
  

Beta2-agonist and anticholinergics are a principle component of the pharmacologic management of chronic obstructive pulmonary disease COPD. It has been demonstrated that the combination of a short acting beta2-agonist and a short acting anticholinergic yields greater efficacy as measured by FEV1 when compared with the response to the individual short acting bronchodilators. However, daily bronchial response to these agents is poorly understood. It is also poorly understood how the variation in magnitude of the response to the individual agents and how the variation in response for one agent coincides with the variation in response to the other agent. This study will seek to define the pattern of response of each individual agent and the relationship between them. The study will also explore if the combination of the two agents leads to less variation in response compared to the individual agents. This is a randomized, open label, two period cross-over study. Eligible subjects will be randomized to a sequence of either albuterol/salbutamol via metered-dose inhaler (MDI) followed by ipratropium via MDI or the same dose of each bronchodilator given in the opposite order. Each study period will consist of 10 clinic visits to be conducted over 10 to 14 days.