Noninvasive mechanical ventilation with average volume assured pressure support (AVAPS) in patients with chronic obstructive pulmonary disease and hypercapnic encephalopathy

BMC Pulm Med. 2013 Mar 12:13:12. doi: 10.1186/1471-2466-13-12.


Background: Non-invasive mechanical ventilation (NIV) in patients with acute respiratory failure has been traditionally determined based on clinical assessment and changes in blood gases, with NIV support pressures manually adjusted by an operator. Bilevel positive airway pressure-spontaneous/timed (BiPAP S/T) with average volume assured pressure support (AVAPS) uses a fixed tidal volume that automatically adjusts to a patient's needs. Our study assessed the use of BiPAP S/T with AVAPS in patients with chronic obstructive pulmonary disease (COPD) and hypercapnic encephalopathy as compared to BiPAP S/T alone, upon immediate arrival in the Emergency-ICU.

Methods: We carried out a prospective interventional match-controlled study in Guayaquil, Ecuador. A total of 22 patients were analyzed. Eleven with COPD exacerbations and hypercapnic encephalopathy with a Glasgow Coma Scale (GCS) <10 and a pH of 7.25-7.35 were assigned to receive NIV via BiPAP S/T with AVAPS. Eleven patients were selected as paired controls for the initial group by physicians who were unfamiliar with our study, and these patients were administered BiPAP S/T. Arterial blood gases, GCS, vital signs, and ventilatory parameters were then measured and compared between the two groups.

Results: We observed statistically significant differences in favor of the BiPAP S/T + AVAPS group in GCS (P = .00001), pCO(2) (P = .03) and maximum inspiratory positive airway pressure (IPAP) (P = .005), among others. However, no significant differences in terms of length of stay or days on NIV were observed.

Conclusions: BiPAP S/T with AVAPS facilitates rapid recovery of consciousness when compared to traditional BiPAP S/T in patients with chronic obstructive pulmonary disease and hypercapnic encephalopathy.

Trial registration: Current Controlled Trials application ref is ISRCTN05135218.

Publication types

  • Controlled Clinical Trial

MeSH terms

  • Aged
  • Aged, 80 and over
  • Critical Care / methods
  • Female
  • Glasgow Coma Scale
  • Humans
  • Hypercapnia / therapy*
  • International Cooperation
  • Length of Stay
  • Male
  • Noninvasive Ventilation / methods*
  • Positive-Pressure Respiration / methods*
  • Prospective Studies
  • Pulmonary Disease, Chronic Obstructive / therapy*
  • Respiratory Insufficiency / therapy*
  • Unconsciousness / therapy*

Associated data

  • ISRCTN/ISRCTN05135218