title: Effect of expiratory positive airway pressure on tidal volume during non-invasive ventilation.
abstract: During non-invasive ventilation (NIV), tidal volume ( Vt) will depend upon the difference between inspiratory and expiratory positive airway pressure (IPAP and EPAP, respectively), provided the respiratory muscles are relaxed and the lungs and chest wall therefore move along their passive pressure-volume curves. To test this hypothesis, we studied the effect of increasing EPAP during pressure-controlled modes of NIV in 30 long-term ventilator users (10 each with scoliosis, obesity hypoventilation or neuromuscular disorders). While maintaining the same IPAP, addition of 5 cmH2O of EPAP reduced mean Vtby 167 ml; 10 cmH2O reduced Vtby 367 ml. This pattern was seen in all three patient groups. EPAP has several potential advantages, for example maintaining upper airway patency, preventing basal atelectasis and facilitating triggering. EPAP does, however, appear to reduce Vt. Decreasing EPAP is an alternative to increasing IPAP if measurements of gas exchange during NIV indicate that ventilation is inadequate.
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: W
authors.initials: W
authors.lastname: Kinnear
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: L
authors.initials: L
authors.lastname: Watson
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: P
authors.initials: P
authors.lastname: Smith
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: L
authors.initials: L
authors.lastname: Johnson
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: S
authors.initials: S
authors.lastname: Burrows
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: J
authors.initials: J
authors.lastname: Colt
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: M
authors.initials: M
authors.lastname: Sovani
authors.affiliation: Gateway B, Nottingham NHS Treatment Centre, Queens Medical Centre, Nottingham, UK.
authors.forename: A
authors.initials: A
authors.lastname: Khanna
mesh_terms: D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation / Q000379:methods*; D009468:Neuromuscular Diseases / Q000150:complications / Q000503:physiopathology; D063087:Noninvasive Ventilation / Q000379:methods*; D010845:Obesity Hypoventilation Syndrome / Q000150:complications / Q000503:physiopathology; D011312:Pressure; D011897:Random Allocation; D012131:Respiratory Insufficiency / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D012600:Scoliosis / Q000150:complications / Q000503:physiopathology; D013990:Tidal Volume
keywords: Non-invasive ventilation; respiratory failure; respiratory muscles; scoliosis; ventilation