To compare the rapid shallow breathing index (RSBI) values, the incidence of adverse reactions, and the predictive accuracy measured under 5 different ventilator strategies in the same patient group.

98 ready for weaning patients were included and divided into success (n=71) and failure (n=27) groups based upon their weaning outcome. Before weaning, the RSBI values were determined under the patients disconnecting from the ventilator (RA-no ventilator) and still connecting to the ventilator with 4 different settings (fraction of inspired oxygen (FiO2) 21 or 40% combined with continuous positive airway pressure (CPAP) 0 or 5 cm H2O). The patients were extubated after completing the weaning trials. Successful weaning was defined as patients free from the ventilator for over 48 hours.

Inclusion Criteria:

• intubated medical patients with mechanically ventilated more than 48 hours
• clinically ready for weaning
• Glasgow coma scales were at least 8
• their ventilator settings were: assist-controlled, pressure support (PS)or synchronized intermittent mandatory ventilation plus PS mode, FiO2 40% or less, positive end-expiratory pressure 5 cm H2O or less, and sensitivity setting on 1 L/min. Their arterial blood gases results were acceptable

Exclusion Criteria:

• having ongoing lung or neuromuscular disease and signs of increased intracranial pressure

respiratory therapy intensive Care unit in a medical center