Table 6—

Failure criteria of spontaneous breathing trials

Clinical assessment and subjective indicesAgitation and anxiety
Depressed mental status
Evidence of increasing effort
 Increased accessory muscle activity
 Facial signs of distress
Objective measurementsPa,O2 ≤50–60 mmHg on FI,O2 ≥0.5 or Sa,O2 <90%
Pa,CO2 >50 mmHg or an increase in Pa,CO2 >8 mmHg
pH <7.32 or a decrease in pH ≥0.07 pH units
fR/VT >105 breaths·min−1·L−1
fR >35 breaths·min−1 or increased by ≥50%
fC >140 beats·min−1 or increased by ≥20%
Systolic BP >180 mmHg or increased by ≥20%
Systolic BP <90 mmHg
Cardiac arrhythmias
  • Data taken from 16, 18, 19, 62, 116. Pa,O2: arterial oxygen tension; FI,O2: inspiratory oxygen fraction; Sa,O2: arterial oxygen saturation; Pa,CO2: arterial carbon dioxide tension; fR: respiratory frequency; VT: tidal volume; fC: cardiac frequency; BP: blood pressure. 1 mmHg = 0.133 kPa.