From capacity to sustainability: Rethinking healthcare flow

Healthcare systems internationally continue to experience sustained operational pressure driven by rising demand, workforce shortages, delayed care backlogs, and increasing clinical complexity. Current recovery strategies frequently focus on expanding activity through additional operating lists, extended working hours, weekend services, escalation pathways, and intensified workforce deployment. Although such approaches may improve short-term throughput, they may simultaneously generate hidden organisational strain that progressively undermines workforce resilience and long-term system stability. Existing healthcare flow literature has substantially advanced understanding of demand-capacity mismatch, bottlenecks, queueing dynamics, and operational variation. However, comparatively little conceptual attention has been directed towards the sustainability of the human systems required to maintain healthcare flow under prolonged pressure. This opinion article proposes a broader conceptual framework for understanding healthcare flow beyond traditional capacity-based models. Drawing on systems thinking, queueing theory, resilience engineering, and workforce sustainability literature, the paper introduces the concepts of sustainable flow capacity, flow saturation, and flow debt as tools for examining the sustainability of healthcare delivery under prolonged operational pressure. The article argues that healthcare organisations should increasingly evaluate whether operational performance remains sustainable over time, rather than focusing solely on throughput escalation.