A client who has been mechanically ventilated for 5 days following ARDS is being evaluated for weaning readiness. The respiratory therapist reports the following parameters: Rapid shallow breathing index (RSBI) of 85, negative inspiratory force (NIF) of -28 cm H2O, spontaneous tidal volume of 6 mL/kg, and FiO2 requirement of 40% to maintain SpO2 >92%. Which parameter indicates the client may NOT be ready for weaning?

A. The Rapid Shallow Breathing Index (RSBI) is calculated as the ratio of respiratory rate to tidal volume (in liters). An RSBI 40% to maintain adequate oxygen saturation indicates ongoing oxygenation impairment, suggesting the client may not yet be ready for weaning. Successful weaning usually requires an FiO2 ≤40% and PEEP ≤5 cm H2O to maintain SpO2 ≥90–92%, ensuring the lungs can sustain oxygenation without excessive support.