Table 6—

Failure criteria of spontaneous breathing trials

Clinical assessment and subjective indices	Agitation and anxiety
	Depressed mental status
	Diaphoresis
	Cyanosis
	Evidence of increasing effort
	Increased accessory muscle activity
	Facial signs of distress
	Dyspnoea
Objective measurements	P_a,O₂ ≤50–60 mmHg on F_I,O₂ ≥0.5 or S_a,O₂ <90%
	P_a,CO₂ >50 mmHg or an increase in P_a,CO₂ >8 mmHg
	pH <7.32 or a decrease in pH ≥0.07 pH units
	f_R/V_T >105 breaths·min⁻¹·L⁻¹
	f_R >35 breaths·min⁻¹ or increased by ≥50%
	f_C >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. P_a,O₂: arterial oxygen tension; F_I,O₂: inspiratory oxygen fraction; S_a,O₂: arterial oxygen saturation; P_a,CO₂: arterial carbon dioxide tension; f_R: respiratory frequency; V_T: tidal volume; f_C: cardiac frequency; BP: blood pressure. 1 mmHg = 0.133 kPa.