Table 2

Sources of heterogeneity: LMIC particularities

Baseline age, comorbidities and performance status
 Age, comorbidities and previous performance status are important determinants of critical care outcome
 Baseline health status and comorbidities have a different profile in LMICs when compared to HICs [7, 8]
ICU admission policies
 Patients may be more prone to be admitted to the ICU according to bed availability or admission policies
 Paucity of ICU beds in Latin American and other LMICs may compromise appropriate timing for ICU admission and result in higher mortality [9, 10]
Local practices in mechanical ventilation
 Some units may choose to start mechanical ventilation early and/or may adopt early weaning protocols; thereby, duration of mechanical ventilation may vary
  Ventilator settings may also be different (i.e. tidal volume)
 Mortality of acute respiratory failure is high in LMICs and adherence to best practices may be lower [11, 12]
Diagnostic technique availability
 Diagnostic techniques may vary between centres and countries
 LMICs may have restricted access to basic and advanced diagnostic methods [10]
Microbiological profile
 Causative pathogen is associated with outcome in nosocomial pneumonia
 Gram-negative rods (including MDR pathogens) are more common in LMICs, especially Latin America [13]
Initial empirical antimicrobial therapy
 Lack of adherence to early antimicrobial therapy may impact clinical outcomes
 Sepsis awareness is lower in LMICs [14]
Use of prevention strategies
 Several prevention strategies may be effective in preventing nosocomial pneumonia, especially VAP (subglottic suctioning tubes, coated tubes, etc.)
 Limited availability of some devices in LMICs
 Lack of availability of single rooms in some settings [15]
EOL preferences
 EOL policies vary between different countries and between different cultures
   This may result in changes in outcome estimates
 Physicians in Latin America may be less prone to establish clear EOL policies and to discuss treatment directives with patients and relatives [16]

HIC: high-income country; EOL: end-of-life.