Ventilator Monitoring in Early Exacerbation Detection

The aim of this study is to determine whether respiratory disease exacerbations (a sudden worsening of symptoms) can be predicted by variables that are monitored by non-invasive ventilators (small machines that assist breathing) in patients requiring long term home ventilation.

The investigators hypothesise that acute exacerbations of patients with respiratory disease and ventilatory failure will be predicted by changes in the respiratory variables monitored and stored by ventilators during chronic home ventilator use.

This pilot study is a proof of concept study investigating whether respiratory variables measured during chronic non-invasive ventilation (NIV) therapy may be used to predict a disease exacerbation.

Modern ventilators used in the home for chronic respiratory failure have the ability to monitor and store respiratory variables that may worsen during exacerbations, and may potentially detect exacerbations before symptoms become apparent. Normal pressure support ventilators monitor respiratory rate which might be expected to increase with worsening disease. In patients with obstructive airways disease an increase in expiratory time may potentially be observed with worsening airways obstruction. Adaptive servo ventilators, which modulate pressure support to maintain constant minute ventilation, may increase the amount of pressure support delivered if respiratory mechanics deteriorate as a result of an exacerbation.

Consenting experienced NIV users will be switched to an adaptive-servo ventilator with the capacity to monitor and store therapy data. The device being used is the Stellar 150 ventilator (Resmed, Ltd., Bella Vista, Australia) with hardware and software ability to measure variables such as respiratory rate, airflow, pressure support and leak.

Patients will use the ventilator for a total of 4 months during which they will complete daily symptom diaries, including medication use and peak flow measurements.

Changes in ventilator variables will be analysed and day to day variation identified. Changes will be compared with daily peak expiratory flow measures (an indication of how well the airways are functioning), patient symptoms, and healthcare utilization. Hospital admissions for exacerbations, GP consults, and healthcare team contacts will also be measured.

Eligibility Criteria:
Inclusion Criteria:

* Patients with a diagnosis of obstructive (COPD, cystic fibrosis, bronchiectasis or chronic asthma) or restrictive (NMD, chest wall disorder) lung disease confirmed by a hospital consultant
* aged \> 18 years
* established home ventilator user with ventilator prescribed for either chronic ventilatory failure or nocturnal hypoventilation
* able to use bilevel positive pressure ventilation with Inspiratory positive airway pressure (IPAP) requirement \<30cm H2O (Stellar ventilator - IPAP max 30)

Exclusion Criteria:

* patients \< 18 years
* cognitive impairment sufficient to interfere with comprehension of the study or use of ventilator
* poor adherence with non-invasive ventilation (\<3hours/night for \>10days/month)
* Inspiratory positive airway pressure (IPAP) requirement \>30cmH2O