Effects of tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury and acute respiratory distress syndrome

Crit Care Med. 2006 Jan;34(1):8-14. doi: 10.1097/01.ccm.0000194538.32158.af.

Abstract

Objective: To assess the effects of step-changes in tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS).

Design: Prospective, nonconsecutive patients with ALI/ARDS.

Setting: Adult surgical, trauma, and medical intensive care units at a major inner-city, university-affiliated hospital.

Patients: Ten patients with ALI/ARDS managed clinically with lung-protective ventilation.

Interventions: Five patients were ventilated at a progressively smaller tidal volume in 1 mL/kg steps between 8 and 5 mL/kg; five other patients were ventilated at a progressively larger tidal volume from 5 to 8 mL/kg. The volume mode was used with a flow rate of 75 L/min. Minute ventilation was maintained constant at each tidal volume setting. Afterward, patients were placed on continuous positive airway pressure for 1-2 mins to measure their spontaneous tidal volume.

Measurements and main results: Work of breathing and other variables were measured with a pulmonary mechanics monitor (Bicore CP-100). Work of breathing progressively increased (0.86 +/- 0.32, 1.05 +/- 0.40, 1.22 +/- 0.36, and 1.57 +/- 0.43 J/L) at a tidal volume of 8, 7, 6, and 5 mL/kg, respectively. In nine of ten patients there was a strong negative correlation between work of breathing and the ventilator-to-patient tidal volume difference (R = -.75 to -.998).

Conclusions: : The ventilator-delivered tidal volume exerts an independent influence on work of breathing during lung-protective ventilation in patients with ALI/ARDS. Patient work of breathing is inversely related to the difference between the ventilator-delivered tidal volume and patient-generated tidal volume during a brief trial of unassisted breathing.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Disease
  • Adult
  • Aged
  • Analysis of Variance
  • Critical Illness
  • Female
  • Follow-Up Studies
  • Hospitals, University
  • Humans
  • Intensive Care Units
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Probability
  • Prospective Studies
  • Respiration, Artificial / methods
  • Respiratory Distress Syndrome, Adult / diagnosis
  • Respiratory Distress Syndrome, Adult / mortality
  • Respiratory Distress Syndrome, Adult / therapy*
  • Respiratory Insufficiency / diagnosis
  • Respiratory Insufficiency / mortality
  • Respiratory Insufficiency / therapy*
  • Risk Assessment
  • Survival Rate
  • Tidal Volume / physiology*
  • Treatment Outcome
  • Work of Breathing / physiology*