Respiratory muscle workload in intubated, spontaneously breathing patients without COPD: pressure support vs proportional assist ventilation

Intensive Care Med. 2003 Jun;29(6):949-954. doi: 10.1007/s00134-003-1704-4. Epub 2003 Mar 27.


Objective: To compare the respiratory muscle workload associated with pressure support ventilation (PSV) and proportional assist ventilation (PAV) in intubated and spontaneously breathing patients without COPD.

Design and setting: Prospective study, intensive care unit university hospital.

Interventions: Twenty intubated patients, during early weaning, PSV settings made by clinician in charge of the patient, and two levels of PAV, set to counterbalance 80% (PAV 80) and 50% (PAV 50) of both elastic and resistive loads, respectively. The patients were ventilated in the following order: 1) PSV; 2) PAV 50 or PAV 80; 3) PSV; 4) PAV 80 or PAV 50; 5) PSV. PSV settings were kept constant.

Measurements: Arterial blood gases, breathing pattern and respiratory effort parameters at the end of each of the five steps.

Main results: PSV and PAV 80 had the same effects on work of breathing (WOB). The pressure-time product (PTP) was significantly higher during PAV 80 than during PSV (90+/-76 and 61+/-56 cmH(2)O.s.min(-1), respectively, P <0.05). Tidal volume was comparable, albeit more variable with PAV 80 than with PSV (variation coefficient, 43% vs 25%, respectively, P <0.05). PAV 50 entailed a higher respiratory rate, lower tidal volume, and higher WOB and PTP than PSV and PAV 80. PaO(2)/FiO(2) and SaO(2) were lower with PAV 50 than with PSV and PAV 80.

Conclusion: In a group of intubated spontaneously breathing non-COPD patients, PAV 80 and PSV were associated with comparable levels WOB, whereas PTP was higher during PAV 80. PAV 50 provided insufficient respiratory assistance.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Airway Resistance
  • Blood Gas Analysis
  • Female
  • Forced Expiratory Flow Rates
  • Humans
  • Intermittent Positive-Pressure Ventilation / methods*
  • Lung Compliance
  • Male
  • Middle Aged
  • Positive-Pressure Respiration / methods*
  • Prospective Studies
  • Pulmonary Disease, Chronic Obstructive / complications
  • Pulmonary Gas Exchange
  • Respiratory Insufficiency / complications
  • Respiratory Insufficiency / metabolism
  • Respiratory Insufficiency / physiopathology
  • Respiratory Insufficiency / therapy*
  • Tidal Volume
  • Treatment Outcome
  • Work of Breathing*