Adaptive Non-invasive Ventilation to Abolish Tidal Flow Limitation
Condition: Pulmonary Disease, Chronic Obstructive; Hypercapnia; Ventilator Lung
MeSH terms: Pulmonary Disease, Chronic Obstructive; Hypercapnia
Study type: Interventional

Summary: 
      This study aimed to evaluate the effects of a novel automatic non-invasive ventilation (NIV)
      mode that continuously adjusts expiratory positive airway pressure (EPAP) to the lowest value
      that abolishes tidal expiratory flow limitation. The investigators conducted a prospective,
      randomized, cross-over study on stable chronic obstructive pulmonary disease (COPD) patients.
      Patients were studied in the hospital during two non-consecutive nights while using either
      fixed or adaptive EPAP. The primary outcome was the transcutaneous partial pressure of carbon
      dioxide. Secondary outcomes were: oxygen saturation, breathing pattern, oscillatory
      mechanics, patient-ventilation asynchronies, sleep quality and sleep-related respiratory
      events.
    

Detailed description: 
      Study design: prospective, randomized, cross-over study. Study population: moderate to severe
      COPD patients, long-term users of nocturnal non-invasive ventilation for chronic hypercapnic
      respiratory failure. Inclusion criteria: age<85 years; presence of tidal expiratory flow
      limitation in the supine position at an expiratory positive airway pressure of 4 cmH2O.
      Exclusion criteria: COPD exacerbation within the past two months; acute illness; clinical
      instability.

      Study protocol: Patients were studied in the hospital over 2 non-consecutive nights while
      using either fixed or automatic EPAP.

      Ventilation strategy: pressure-controlled NIV was delivered using a non-commercial version of
      BiPAP Synchrony Ventilator (Philips-Respironics) via an unvented facial mask (AMARA,
      Philips-Respironics). The ventilator evaluated the presence of tidal expiratory flow
      limitation by the forced oscillation technique. In the automatic-EPAP mode, the ventilator
      continuously adjusted EPAP to the minimum level able to abolish tidal expiratory flow
      limitation, with a minimum EPAP of 4 cmH2O and keeping the pressure support constant.

      Measurements: During each study night, the investigators recorded transcutaneous partial
      pressure of carbon dioxide and oxygen saturation (TOSCA, Radiometer) continuously. Airway
      opening pressure, flow and volume tracings were exported from the ventilator. Full laboratory
      polysomnography (Alice5, Philips-Respironics) was performed according to the American Academy
      of Sleep Medicine recommendations.

      Data analysis: the investigators compared parameters from the two nights using Wilcoxon
      signed-rank test. P-values <0.05 were considered statistically significant.
    

Intervention name(s): fixed-EPAP; auto-EPAP
Intervention type(s): Device; Device
Intervention description(s): In the fixed-EPAP mode, the device kept EPAP fixed at the prescribed value; In the Auto-EPAP mode, the device automatically adjusted EPAP to the minimum level able to abolish tidal expiratory flow limitation.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Supportive Care