Non-invasive ventilation--mechanisms of benefit

Over the last few years there has been growing interest in the use of non-invasive ventilation (NIV) in the management of ventilatory failure in acute on chronic ventilatory failure and in stable hypercapnic patients. To understand why assisted ventilation should be effective in improving gas exchange even during spontaneous breathing a basic understanding of the pathophysiology of ventilatory failure is required and this is discussed. The etiology of ventilatory failure is likely to be multifactorial with different factors assuming greater or lesser degrees of importance even in patients with the same condition. Indeed in an individual patient there may be differences at various stages of the illness. The same is true for the mechanism of benefit from NIV. With the current state of knowledge during NIV the aim should be to rest the respiratory muscles, control nocturnal hypoventilation and improve sleep quality. In some individuals severe symptoms, as a consequence of disturbed sleep, may occur and be symptomatically improved by non-invasive ventilation during sleep.