The effect of back-up rate during non-invasive ventilation in young patients with cystic fibrosis

Intensive Care Med. 2004 Apr;30(4):673-81. doi: 10.1007/s00134-003-2126-z. Epub 2004 Jan 16.


Objective: The aim of the study was to evaluate the effect of the back-up rate on respiratory effort during non-invasive mechanical ventilation.

Design: An in vitro study evaluated the inspiratory trigger in seven domiciliary ventilators. Then, a prospective, randomized, crossover trial compared the effect on respiratory effort of three different back-up rates during pressure support (PS) and assist-control/volume-targeted (AC/VT) ventilation.

Setting: A research unit and a tertiary referral pediatric center.

Patients: Ten patients with cystic fibrosis (CF).

Interventions: During the in vivo study, the back-up rate was progressively increased to the maximum that patients could tolerate (Fmax) and respiratory effort, as judged by pressure/time product of the diaphragm (PTPdi/min), was compared between the two ventilatory modes.

Results: Differences were observed between trigger pressure, trigger time delay, trigger pressure/time product and the slope between flow and pressure in the seven ventilators. PS and AC/VT ventilation were associated with a decrease in respiratory effort (PTPdi/min was 518+/-172, 271+/-119 and 291+/-138 cmH(2)O. s(-1). min(-1), for spontaneous breathing, PS and AC/VT ventilation, respectively, p=0.05). During the two modes, increasing the back-up rate to Fmax resulted in a greater reduction in PTPdi/min (p=0.001), which was more pronounced during AC/VT ventilation, due to the automatic adjustment of the inspiratory/expiratory time ratio.

Conclusions: Increasing the back-up rate during PS and AC/VT ventilation decreases respiratory effort in young patients with CF, but this effect was more marked with AC/VT ventilation.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Cross-Over Studies
  • Cystic Fibrosis / physiopathology*
  • Female
  • Humans
  • Intensive Care Units
  • Lung / physiopathology*
  • Male
  • Peak Expiratory Flow Rate
  • Prospective Studies
  • Pulmonary Gas Exchange
  • Respiration, Artificial / methods*
  • Respiratory Function Tests
  • Respiratory Mechanics