Vital signs are the fundamental measurements used by healthcare professionals to quickly assess a person’s basic bodily functions. These indicators reflect life-sustaining processes, providing an immediate snapshot of physiological health. Monitoring these values allows clinicians to track a patient’s stability, identify deviations from their baseline, and detect potential health crises. The consistent measurement of these signs is a universal practice, forming the initial step in nearly every medical evaluation.
The Foundation: Traditional Vital Signs
The core set of traditional vital signs historically consisted of four measurements reflecting cardiovascular and respiratory function: Body Temperature, Pulse Rate, Respiratory Rate, and Blood Pressure. The medical community recognized the limitations of these measures in providing a complete picture of a patient’s well-being. This led to the widespread adoption of a fifth measurement. Pain was designated as the fifth vital sign to ensure its routine assessment and management, acknowledging that subjective experience is an important indicator of overall health status.
Identifying Candidates for the 6th Vital Sign
The search for a comprehensive physiological picture has led to two main candidates for the sixth vital sign: Pulse Oximetry and Functional Status.
Pulse Oximetry (SpO2)
Pulse Oximetry, or SpO2, is the most commonly adopted candidate in acute care settings, measuring the percentage of hemoglobin carrying oxygen in the blood. This non-invasive test uses a device on a fingertip to calculate oxygen saturation, typically yielding a result between 95% and 100% in a healthy individual. Oxygen saturation provides immediate, objective data on the efficiency of oxygen transport, offering a direct measurement of respiratory function that traditional signs cannot provide alone.
Functional Status (Gait Speed)
Functional Status, often measured by Gait Speed or walking velocity, is another significant candidate, particularly in geriatric and rehabilitation medicine. This metric reflects the integrated health of the neurological, musculoskeletal, and cardiovascular systems. Gait speed is easily measured by timing a patient over a short distance and is highly predictive of future health outcomes. A walking speed below certain thresholds, such as 0.6 meters per second, indicates an increased risk for hospitalization, dependency, and mortality. While SpO2 focuses on an immediate physiological state, gait speed serves as a powerful long-term prognostic indicator.
Integrating the New Sign into Patient Care
The systematic integration of a sixth vital sign improves patient safety and the precision of clinical assessment.
SpO2 Integration
Incorporating SpO2 provides an early warning signal for respiratory distress, allowing clinicians to detect low oxygen levels (hypoxemia) non-invasively before generalized symptoms appear. Continuous pulse oximetry monitoring, particularly in critical care environments, enhances the ability to detect subtle patient deterioration. Its inclusion in Early Warning Score systems helps accurately stratify patient risk, triggering timely intervention by rapid response teams.
Functional Status Integration
Incorporating gait speed into routine patient visits fundamentally changes risk stratification and care planning. A measurable decline in walking speed provides an objective, actionable metric that prompts interventions like physical therapy to mitigate frailty and reduce the likelihood of falls. This measurement helps healthcare providers predict the need for rehabilitation services and assess the probable discharge location following a hospital stay. By adding this functional assessment, the overall physiological snapshot becomes more comprehensive, including a measure of physical resilience and long-term prognosis. This results in a shift toward proactive, personalized care that improves patient outcomes through early detection and targeted prevention strategies.