Non-Invasive Ventilation (NIV) For Positive Pressure Support. A Randomised Cross-Over Trial To Evaluate The Short-Term Effects of NIV As An Adjunct To Airway Clearance Techniques in Adults With Cystic Fibrosis.

Cystic Fibrosis (CF) is a genetic disorder of altered ion transport across cell membranes which is characterised by the production of thickened bodily secretions, affecting the function of organs such as the pancreas and the lungs. Within the lungs, thickened mucus alters normal mucocillary clearance mechanisms resulting in airway obstruction, mucus plugging and recurrent infections. The cycle of recurrent infections and subsequent inflammation is thought to be the major mechanism towards damage to lung tissue and the occurrence of fibrosis, which decreases lung function, lowers tissue oxygenation and eventually leads to respiratory failure and death. Optimisation of the removal of airway secretions is therefore an integral part of the management of CF in order to try and prevent these complications. Traditionally, a variety of approaches are usually combined including mucolytic or hydrator therapy to make the secretions less viscous, and chest physiotherapy to mobilise secretions and improve airway clearance.

There are many chest physiotherapy or airway clearance techniques (ACT) available including breathing methods such as the Active Cycle of Breathing Techniques (ACBT) or Autogenic Drainage (AD) and adjuncts such as Positive Expiratory Pressure (PEP), High Frequency Chest Oscillation (the "Vest"), or oscillatory devices such as the Flutter or Acapella. Research has shown there to be no difference in effectiveness between techniques, as long as they are performed correctly and regularly, and therefore choice of ACT depends upon assessment of the patient by a trained physiotherapist and discussions with the individual. With advancing disease or infections, often the effectiveness of ACTs can decrease due to patient fatigue, shortness of breath or overwhelming amount of secretions. At this time it is necessary to re-assess ACTs, and the addition of positive pressure to airway clearance techniques has been shown to decrease patient fatigue and respiratory rates during clearance. One of these studies also demonstrated improvements in oxygenation and respiratory muscle strength after the use of positive pressure with ACT. While no studies have reported an increase in sputum expectorated with the addition of positive pressure, the ability to augment greater tidal volumes through positive pressure is thought to be a mechanism which could improve sputum clearance. Clinical experience at the Royal Brompton hospital has indicated that with alterations in pressure and flow rates from resting settings, sputum clearance appears to be easier and more effective; the investigators aim to explore this observation objectively in this study.

Research Question:

Does the addition of non-invasive ventilation (Breas, I-Sleep 25) as supplementary positive pressure to normal airway clearance techniques improve sputum clearance in stable adult patients with cystic fibrosis?

Hypothesis