• Measured at Month 6: total number of hours of stationary oxygen use
  
• total number of hours of ambulatory/portable oxygen use
  

• Measured at Months 3 and 5: activity
  
• Measured at Months 3 and 6: spirometric lung function testing
  
• hemoglobin level
  
• functional exercise capacity
  
• body weight
  
• health status
  
• ambulatory status
  
• survival
  
• number of exacerbations, physician office visits, and hospitalizations
  
• exercise endurance (measured at selected sites)
  

Individuals with COPD who experience hypoxemia (reduction of oxygen concentration in arterial blood) have an especially poor prognosis. Provision of LTOT to hypoxemic COPD patients is considered to be the standard of care. The majority of hypoxemic patients that are ambulatory are supplied with pressurized oxygen in E-cylinders. This system weighs approximatley 22 pounds, is mounted on a wheeled cart, and is towed by the patient. These cumbersome systems can be seen to impose a significant burden on weak and debilitated patients, discouraging them from being active. E-cylinders towed on a cart are referred to as 'portable,' in contrast to lightweight 'ambulatory' oxygen systems, which weigh less than 10 pounds and are designed to be carried by the patient. It is unknown whether patients provided with lightweight ambulatory systems comply better with oxygen prescription and increase their daily level of activity. This study will compare the use and benefits of a lightweight ambulatory oxygen device versus the standard portable E-cylinder device among hypoxemic individuals with COPD. Specifically, the study will examine daily duration of oxygen therapy and activity levels amongst both groups.

Inclusion Criteria:

• Currently in a stable phase of COPD, defined as having had no disease exacerbation within the 4 weeks prior to study entry
• Ambulatory
• Forced expiratory volume in one second (FEV1) less than or equal to 60% of predicted value at screening
• Ratio of FEV1 and forced vital capacity (FEV1/FVC) less than or equal to 65% of predicted value at screening
• Currently receiving LTOT
• Partial pressure of oxygen in arterial blood (PaO2) less than 60 torr

Exclusion Criteria:

• Clinically significant cardiovascular disease (e.g., uncontrolled hypertension, left-sided heart failure, peripheral vascular disease, exertional angina, complex arrhythmias, severe dependent edema, ischemic changes on stress electrocardiogram that would be contraindications for unrestricted ambulation or the 6-minute walk test)
• Orthopedic impairments that would limit ambulation
• Participation in the active phase of pulmonary rehabilitation within the 3 months prior to study entry
• Neurologic impairments (e.g., Parkinson's disease or a stroke) or mental states (e.g., senile dementia) that would limit independent ambulation
• Neoplastic disease that is anticipated to influence survival
• Currently receiving lightweight ambulatory oxygen therapy
• Inability to maintain an oxygen saturation of 92% at rest with 4L/minute of continuous oxygen flow and during exercise with an oxygen conserver setting of 6 utilizing a nasal cannula
• Currently a smoker
• Sleep apnea if it is characterized primarily as central sleep apnea syndrome (whether being treated or not) OR if it is known or suspected obstructive sleep apnea that has existed for at least 2 months and has not received stable treatment (stable treatment modes include positive airway pressure therapies or dental orthotic/mandibular positioning devices); individuals with diagnosed obstructive sleep apnea must have a body mass index less than or equal to 30 kg/m2 to be eligible for this study