The impact of mechanical ventilation on long-term survival influences definitions of persistent critical illness

There are notable gaps in the understanding of the underlying pathophysiology of persistent critical illness (PerCI) and its extensive implications for patient outcomes. In this context, whether different PerCI definitions could yield distinct long-term outcomes for intensive care unit survivors is currently unknown. This prospective cohort study spanned 10 Brazilian hospitals from March 2015 to December 2017. We enrolled emergency medical and surgical patients with intensive care unit stays exceeding 72 hours and tracked them for more than 12 months after intensive care unit discharge. Chronic patients were classified using four widely recognized persistent critical illness definitions from the literature: 1) mechanical ventilation > 21 days or tracheostomy for mechanical ventilation weaning; 2) mechanical ventilation duration > 14 days; 3) intensive care unit stay > 10 days; and 4) intensive care unit stay > 8 days accompanied by specific clinical conditions warranting extended intensive care unit care. Additionally, the data were compared to those of survivors who did not meet any of the four persistent critical illness criteria. The study enrolled 1,616 patients, with 609 (37.7%) fulfilling one or more persistent critical illness definitions. The twelve-month survival rates among persistent critical illness patients varied by definition. At 12 months, patients with PerCI definitions centered on mechanical ventilation duration had markedly lower survival rates than non-persistent critical illness patients did (definition 1: HR: 1.49, 95%CI: 1.10 - 2.02; definition 2: HR: 1.66, 95%CI: 1.20 - 2.30). In contrast, definitions based on intensive care unit length of stay produced survival rates more aligned with non-persistent critical illness patients (definition 3: HR: 1.01, 95%CI: 0.82 - 1.25; definition 4: HR: 1.10, 95%CI: 0.88 - 1.30). Compared with other critically ill patients, patients with persistent critical illness definitions that are based on the duration of mechanical ventilation are associated with reduced 12-month survival, highlighting the impact of prolonged respiratory support on patient outcomes.