Does Chronic Ventilatory Support Improve the Outcomes of Rehabilitation in Hypercapnic COPD Patients?

Several randomised controlled trials in patients with stable Chronic Obstructive Pulmonary Disease (COPD) have demonstrated that pulmonary rehabilitation (PR) improves dyspnoea, exercise tolerance, and health-related quality of life. Research in this field has been important in our department for several years. The first study in this respect was started in 1986 comparing outpatient rehabilitation with rehabilitation in the community in patients with severe COPD. This study showed that rehabilitation supervised by a physical therapist in the community is effective for a long period in contrast to outpatient rehabilitation. In 1990 the second study started showing that positive initial benefits of home based rehabilitation on quality of life can be maintained for 18 months if the patients visit the local physical therapist once a month.

However, less positive effects of rehabilitation have been reported in the more severe patients. Because of dyspnoea due to inspiratory muscle fatigue patients may not receive an adequate training stimulus, and therefore rehabilitation might be less effective. In these more severe patients alternative therapies are needed. These non-pharmacological treatments include nutritional supplementation, oxygen therapy, lung transplantation, lung volume reduction surgery and ventilatory support.

The last few years a discussion within the 4 home mechanical ventilation centres (HMV) in the Netherlands has been started about the role of chronic ventilatory support in end-stage COPD. Theoretically, it might be effective because:

1. a resetting of the respiratory centre may reduce daytime PaCO2;
2. a better internal milieu (pH, PaO2, PaCO2) may improve peripheral muscle function;
3. resting the respiratory muscles during the night may increase their daytime strength and endurance;
4. a reduction in the number of nocturnal arousals may improve the quality of sleep. Nevertheless, none of these mechanisms has been proven and currently there is no evidence that noninvasive positive pressure ventilation (NIPPV) should be given to stable patients with COPD. While several randomised controlled trials (RCT's) on NIPPV have been published with different outcomes, a recent meta-analysis did not show beneficial effects on blood gasses, lung function, respiratory muscle function and walking distance.

In contrast several uncontrolled studies did show clear benefits from NIPPV on gas-exchange, dyspnoea and quality of life. Possible reasons for these conflicting outcomes are differences in: