Effect of pressure support ventilation and positive end expiratory pressure on the rapid shallow breathing index in intensive care unit patients

Intensive Care Med. 2008 Mar;34(3):505-10. doi: 10.1007/s00134-007-0939-x. Epub 2007 Dec 1.


Objective: We compared rapid shallow breathing index (RSBI) values under various ventilatory support settings prior to extubation.

Design and setting: Prospective study in the intensive care unit at a university hospital.

Patients: Thirty six patients ready for extubation.

Interventions: Patients were enrolled when receiving pressure support ventilation (PSV) of 5 cmH2O, PEEP of 5 cmH2O, and FIO2 of 40% (PS). Subsequently each patient received a trial of PSV of 0 cmH2O, PEEP of 5 cmH2O, and FIO2 of 40% (CPAP), a trial of PSV of 0 cmH2O, PEEP of 5 cmH2O and FIO2 of 21% (CPAP-R/A), and a 1-minute spontaneously breathing room air trial off the ventilator (T-piece). Trials were carried out in random order.

Measurements and results: Respiratory frequency (f) and tidal volume (VT) were measured during PS, CPAP, CPAP-R/A, and T-piece in all patients. RSBI (f/VT) was determined for each patient under all experimental conditions, and the average RSBI was compared during PS, CPAP, CPAP-R/A, and T-piece. RSBI was significantly smaller during PS (46+/-8 bpm/l), CPAP (63+/-13 bpm/l) and CPAP-R/A (67+/-14 bpm/l) vs. T-piece (100+/-23 bpm/l). There was no significant difference in RSBI between CPAP and CPAP-R/A. RSBI during CPAP and CPAP-R/A were significantly smaller than RSBI during T-piece. In all patients RSBI values were less than 105 bpm/l during PS, CPAP, and CPAP-R/A. However, during T-piece the RSBI increased to greater than 105bpm/l in 13 of 36 patients.

Conclusions: In the same patient the use of PSV and/or PEEP as low as 5 cmH2O can influence the RSBI. In contrast, changes in FIO2 may have no effect on the RSBI.

Publication types

  • Comparative Study

MeSH terms

  • Aged
  • Female
  • Humans
  • Intensive Care Units
  • Intubation, Intratracheal
  • Male
  • Middle Aged
  • Positive-Pressure Respiration / methods*
  • Prospective Studies
  • Regression Analysis
  • Respiratory Insufficiency / therapy*
  • Respiratory Mechanics / physiology
  • Ventilator Weaning / methods
  • Ventilators, Mechanical