Table 1.

GRADE evaluation of interventions for carbon monoxide poisoning (acute)

Important outcomes	Carboxyhaemoglobin levels, neurological sequelae, mortality, adverse effects
Number of studies (participants)	Outcome	Comparison	Type of evidence	Quality	Consistency	Directness	Effect size	GRADE	Comment
What are the effects of oxygen treatments for acute carbon monoxide poisoning?
2 (367)	Neurological sequelae	Hyperbaric oxygen 100% v oxygen 100% given by non-re-breather mask in mild to moderate poisoning	4	–1	0	–2	0	Very low	Quality point deducted for lack of blinding. Directness points deduced for uncertainty about definition of outcome and inclusion of differing severities of CO poisoning
1 (152)	Neurological sequelae	Hyperbaric oxygen 100% v normobaric oxygen 100% in moderate to severe poisoning	4	–2	0	–1	0	Very low	Quality points deducted for sparse data and methodological weaknesses (possible bias). Directness point deducted for disparity between groups at baseline in number of people with cerebellar abnormalities
1 (139)	Neurological sequelae	Hyperbaric oxygen 100% interspersed with normobaric oxygen v normobaric oxygen 100% in moderate to severe poisoning	4	–2	0	–2	0	Very low	Quality points deducted for sparse data and methodological weaknesses (change in definition of outcome during trial). Directness points deducted for disparity in high Mini-Mental scores at baseline and for unclear reporting of numbers of sessions of treatment given and pressures/durations of hyperbaric treatment

Type of evidence: 4 = RCT; 2 = Observational Consistency: similarity of results across studies Directness: generalisability of population or outcomes Effect size: based on relative risk or odds ratio