Domiciliary ventilation in chronic obstructive pulmonary disease: where are we?

Thorax Editorials Domiciliary ventilation in chronic obstructive pulmonary disease: where are we? The introduction of non-invasive nasal positive pressure ventilation (NIPPV) in the late 1980s has been a major advance in the home management of patients with chronic hypercapnic respiratory failure due to chest wall and neuro-muscular disease.`3 Nasal ventilation is considerably easier to administer than previously used negative pressure techniques , and this has enabled many more patients to be offered long term domiciliary ventilation with correction of arterial blood gases, control of nocturnal hypoventil-ation, and improvement in quality of life. This success with NIPPV has stimulated renewed interest in its use at home in patients with chronic obstructive pulmonary disease (COPD). However, is there sufficient evidence for benefit, and which group of patients with COPD should be selected for domiciliary NIPPV? Patients with severe COPD exhibit marked abnormalities ofventilation overnight which causes derangement ofblood gas tensions and may contribute to the progressive deterioration seen in this group.45 Long term domiciliary oxygen therapy (LTOT), when used for 15 or more hours per day, has been shown to have physiological benefit and improves survival in patients with hypoxic COPD.67 It has therefore been suggested that ventilatory support at home may confer further advantages when used in addition to LTOT. Physiological considerations Evidence is emerging that the mechanisms underlying the sustained change in daytime blood gas tensions with ventilation is related to reversal of nocturnal hypo-ventilation and improvement in carbon dioxide responsiveness. Withdrawal of non-invasive ventilation in patients with chest wall and neuromuscular disease results in deterioration in symptoms and nocturnal hypo-ventilation, but has no effects on respiratory muscle function.89 A study of NIPPV in patients with COPD showed that those patients whose blood gas tensions improved had associated increased chemosensitivity to carbon dioxide, although no effects were observed on respiratory muscle strength.'0 It has been suggested that the respiratory muscles of patients with COPD are subject to fatigue. Several investigators have shown that the application of non-invasive ventilation, using both positive and negative pressure techniques, may produce significant reductions in electro-myographic (EMG) activity of the diaphragm and work of breathing."-'" However, no long term controlled study has yet shown an improvement in measures of ventilatory muscle strength with the addition of assisted ventilation. Patients with hypoxic COPD also have sleep disruption, although the effects of supplemental oxygen therapy on sleep quality have been variable.'516 Although some of these patients may …