Healthcare & Clinical
ROX Index for HFNC Failure & Rapid Shallow Breathing Index (RSBI = f / VT)
Calculate the Roca ROX Index (SpO2 / FiO2) / RR to predict high-flow nasal cannula (HFNC) intubation risk and the Yang-Tobin Rapid Shallow Breathing Index RSBI = RR / VT_L for ventilator weaning.
Prevent delayed intubation on HFNC and failed extubation on mechanical ventilation!
In hypoxemic respiratory failure treated with High-Flow Nasal Cannula (HFNC), Roca et al.'s ROX Index combines oxygenation (SpO2% divided by fractional FiO2 from 0.21 to 1.00) in the numerator and work of breathing (respiratory rate RR, breaths/min) in the denominator: ROX = (SpO2 / FiO2) / RR! At 2, 6, and 12 hours on HFNC, ROX >= 4.88 predicts successful HFNC therapy without intubation, whereas ROX < 3.85 at 12 hours flags high risk of HFNC failure requiring prompt intubation (3.85 to < 4.88 is an indeterminate zone requiring frequent reassessment)!
Conversely, during a spontaneous breathing trial (SBT) prior to extubating a mechanically ventilated patient, Yang and Tobin's Rapid Shallow Breathing Index divides respiratory rate RR by spontaneous tidal volume VT in LITERS: RSBI = RR / VT_L! An RSBI < 105 breaths/min/L predicts ~80% successful ventilator weaning, whereas rapid shallow breathing with RSBI >= 105 signals impending respiratory muscle fatigue.
| ICU Respiratory Index | Bedside Inputs | Formula & Result | Clinical Threshold |
|---|---|---|---|
| ROX Index (Stable HFNC) | SpO2 = 94%, FiO2 = 0.50, RR = 28 | (94 / 0.50) / 28 = 6.71 | >= 4.88: Low HFNC Failure Risk |
| ROX Index (Failing HFNC) | SpO2 = 90%, FiO2 = 0.75, RR = 34 | (90 / 0.75) / 34 = 3.53 | < 3.85: High Intubation Risk! |
| RSBI (Spontaneous Breathing Trial) | SBT RR = 24, VT = 0.40 L (400 mL) | 24 / 0.40 = 60.0 breaths/min/L | < 105: Favorable for Extubation |
ROX Index = (SpO2% / Fractional_FiO2) / RR
Validates SpO2 in (0, 100], fractional FiO2 in [0.21, 1.0], and RR > 0 before computing ROX.
=IF(OR(B2 <= 0, B2 > 100, B3 < 0.21, B3 > 1, B4 <= 0), "Invalid Respiratory Inputs", ROUND((B2 / B3) / B4, 2))Rapid Shallow Breathing Index RSBI = SBT_RR / Tidal_Volume_L
Divides spontaneous respiratory rate B5 (breaths/min) by spontaneous tidal volume B6 (L).
=IF(OR(B5 <= 0, B6 <= 0), "Invalid Respiratory Inputs", ROUND(B5 / B6, 1))Try the example
Use the original values or change them to test your understanding.