Monitoring Variability and Complexity at the Bedside

Abstract

Uncertainty regarding diagnosis and prognosis of critical illness results in increased mortality and cost. To address this clinical uncertainty, researchers have pioneered methods to analyse waveforms, including analysing the degree and variation of heart rate and respiratory rate over intervals-in-time, termed variability analysis. Research has demonstrated that altered heart and respiratory rate variability (HRV and RRV) are associated with and prognostic of critical illness (e.g. sepsis, organ failure, and extubation failure). We developed continuous individualized multiorgan variability analysis (CIMVATM) software to evaluate HRV and RRV continuously over time. We hypothesize that continuous variability monitoring in the ICU can provide improved ability to predict clinical trajectory potentially leading to real-time prognostication. In this review we explore the meaning of the altered variability in terms of degree and complexity and we discuss the potential clinical value of monitoring variability with respect to early warning of sepsis, prognostication of organ failure, impact of sedation, and improved prediction of extubation failure.