Effect of pressure support ventilation and positive end expiratory pressure on the rapid shallow breathing index in intensive care unit patients.
OBJECTIVE
We compared rapid shallow breathing index (RSBI) values under various ventilatory support settings prior to extubation.


METHODS
Prospective study in the intensive care unit at a university hospital.


METHODS
Thirty six patients ready for extubation.


METHODS
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.


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.
Department of Anesthesiology, American University of Beirut, Riad El Solh, P.O. Box 11-0236, 1107 2020 Beirut, Lebanon.
Mohamad F
MF
El-Khatib
Salah M
SM
Zeineldine
Ghassan W
GW
Jamaleddine
D000368:Aged; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007442:Intubation, Intratracheal; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D012044:Regression Analysis; D012131:Respiratory Insufficiency / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology; D015300:Ventilator Weaning / Q000379:methods; D012122:Ventilators, Mechanical