Non-invasive ventilation (NIV)
Non-invasive ventilation (NIV) is “the provision of ventilatory support through the patient’s upper airway using a mask or similar device” (BTS guidelines, 2002). The aims of ventilation include:
• Correcting hypoxaemia (low blood oxygen levels) and/or hypercapnia (high blood carbon dioxide levels)
• Improving tidal volumes/decreasing atelectasis (lung collapse)
• To decrease fatigue and the work of breathing
• To buy time for medications etc. to work
Non invasive ventilation has been used for patients with CF since the early 1990s when it was described as a holding measure for patients on the transplant waiting list (Hodson et al, 1991). Non invasive ventilation is occasionally used as a ‘bridge to transplant’ but there are many other indications for considering this treatment in CF care:
• Type II respiratory failure, acute or acute on chronic respiratory failure
• Nocturnal hypoventilation
• During pregnancy
• During/post surgical procedures
• As an adjunct to physiotherapy
What do the guidelines say?
Although NIV is used for the above indications in many CF Units there is little robust academic evidence for its effectiveness (Moran et al, 2009). There are no randomised controlled trials of NIV versus conventional treatment. The British Thoracic Society Guidelines (BTS guidelines, 2002) advise that “a trial of NIV may be undertaken in patients with a respiratory acidosis (pH <7.35) secondary to an acute exacerbation of bronchiectasis, but excessive secretions are likely to limit its effectiveness and it should not be used routinely.”
NIV and physiotherapy
The BTS guidelines state that, “NIV can be used as an adjunct to physiotherapy, but there is insufficient evidence to recommend its routine use in these patients. Studies have reported reduced fatigue when NIV is used in association with airway clearance. Maximum inspiratory pressure and oxygen saturation are maintained, and the respiratory rate is lowered during treatment. Moran & Bradley do document a patient perception of easier chest clearance, and a patient preference for the addition of NIV with physiotherapy but no increase in sputum clearance as measured by sputum weight when NIV is used for airway clearance (Moran & Bradley, 2003).
NIV and exercise
NIV use during exercise may decrease dyspnoea and improve oxygenation thereby improving exercise tolerance (BTS guidelines, 2002). There is, however, no objective evidence at present to support this.
• There is little evidence in the literature to support the wide use of NIV in Cystic Fibrosis. This is mainly due to an absence of clinical studies.
• By extrapolation from experience in the management of chronic obstructive pulmonary disease (COPD) there is likely to be a significant role for NIV in the management of ventilatory failure following acute exacerbations.
• Chronic use of NIV is anecdotal but there is likely to be a role for such therapy as a bridge to transplantation and for patients with severe symptomatic hypercapnia.
• NIV can be used as an adjunct to physiotherapy
British Thoracic Society (BTS) guidelines. Non-invasive ventilation in acute respiratory failure. Thorax 2002; 57: 192-211.[PubMed]
Hodson ME, Madden BP, Steven MH, et al. Non-invasive ventilation for cystic fibrosis patients – a potential bridge to transplantation. Eur Respir J 1991; 4: 524-527. [PubMed]
Moran F, Bradley J. Non-invasive ventilation for cystic fibrosis. Cochrane Database Syst Rev 2003; 2: CD002769 .[PubMed]
Moran F, Bradley JM, Piper AJ. Non-invasive ventilation for cystic fibrosis. Cochrane Database Syst Rev. 2009 Jan 21;(1):CD002769. [PubMed]