The effect of inspiratory duration and chinstrap during non-invasive ventilation

INTERVENTION: Night 1: Sleep study titration review study on non‐invasive ventilation (with titration of inspiratory time during the study and no chinstrap). Nights 2,3 & 4 at home acclimatizing to NIV without chinstrap. (inspiratory duration not set) Night 5, 6 & 7: Three experimental nights in randomized order Inspiratory duration set no chinstrap Inspiratory duration not set no chinstrap Inspiratory duration set with chinstrap The duration on the experimental interventions is one night each. CONDITION: Hypercapnic Respiratory Failure Nocturnal hypoventilation PRIMARY OUTCOME: Sleep quality including arousals Sleep quality including percentage REM sleep Sleep quality including sleep efficiency SECONDARY OUTCOME: 1. Non‐invasive gas exchange overnight (SaO2, TcCO2). 2. Apnoea and arousal index. 3. Subjective scores of comfort and sleep. 4. Synchronization index (number of successful inspiratory and expiratory triggers). 5. Psychomotor vigilance testing. INCLUSION CRITERIA: Patients with documented nocturnal hypoventilation from any cause. Using non‐invasive ventilation chronically at home. Be using a bilevel pressure preset ventilator at home in the spontaneous mode. Be using a nasal interface with NIV. Preferably to be using NIV without the use of supplemental oxygen. To be included in the study, subjects will: 1. Have to have sustained improvements in gas exchange and symptomatolgy. 2. Be compliant with non‐invasive ventilation at home (using >5hrs per night). 3. Able to attend the sleep laboratory on 3 nights within the trial period (ie 6 nights).