Table 1 General and specific quality criteria

Sample size (total number of participants)

Randomization allocation concealment (adequate, inadequate or uncertain)

Objective selection criteria for participants:

   Yes: if inclusion and exclusion criteria for participants are adequately reported

   No: if selection criteria are not reported

Blinding:

   Yes: for articles that implemented blinding at any level

   No: for articles reporting not being able to implement blinding of interventions at any level

   Not reported: for articles that did not make any mention of blinding

Standardization of co-interventions:

   Yes: if there was an attempt to standardize treatment and care besides the assigned interventions

   No: if no attempt to standardize was applied

   Uncertain: if this was not clearly reported

Intention-to-treat analysis (adequate, inadequate or uncertain)

Complete follow-up details (yes, no, not reported)

Outcome definition:

   Adequate: if objective criteria for endotracheal intubation were defined

   Inadequate: if the criteria were not defined

   Uncertain: if application of criteria was unclear

Specific quality criteria

Patient selection criteria (inclusion and exclusion)

Type of patients (presence of baseline co-morbidity: AMI or chronic obstructive pulmonary disease)

Description of baseline criteria for severity of illness

Report of interventions (technical description of CPAP and NPPV methods)

Report of objective criteria for endotracheal intubation (adequate, inadequate or uncertain)