Table 4 Observation Unit interventions and intervention characteristics

Condition Specific Observation Units

For example, Chest Pain Observation Units are for patients presenting with chest pain who are a low risk of acute myocardial infarction to undergo a short period of monitoring with serial ECGs and cardiac enzymes before further testing and discharge [53].

Rapid Assessment Zones/ Pods

Rapid Assessment Zones/ Pods (also referred to as Minor Injury Units) are spaces in ED adapted for clinician assessment and procedures for patients whose therapeutic needs exceed typical fast-track criteria, but can still receive investigations/ therapy in a chair and require limited observation [18, 55]. In Rapid Assessment zones/ pods, investigations are initiated, patients wait for results and/ or receive treatment in a chair or stretcher [55].

Medical Assessment Units

Medical Assessment Units are areas in ED for patients with complex medical conditions who will likely require admission [4, 8, 17]. Medical Assessment Units involve fast-tracking care of medically stable patients [17].

Short Stay Units

Short Stay Units are spaces in ED for patients who require a short period of observation, treatment (e.g., blood transfusions), or further diagnostic investigations that may take several hours to resolve without occupying ED beds or being admitted [8, 17, 54, 56].

ED Managed Acute Care Unit

ED managed acute care unit is a space physically remote from ED but staffed by ED for ED patients who require observation or management for more than 4 h [19].

Quick Diagnostic Units

Quick Diagnostic Units have been introduced to ED to manage referrals from GPs to EDs and are staffed by internal medicine specialists [18]. ED-based observations similar to the Quick Diagnostic Unit include Clinical Decision Units, Medical Assessment and Planning Units, Rapid Assessment and Planning Units, Observation bays, Express Admission Units [18].