Impact of helicopter emergency medical services base operating regime (24 h vs. 07:00–20:00) on mission volume and structure in Poland: a cross-sectional–longitudinal analysis with duty-time standardization (10 March–10 August 2025)

Helicopter Emergency Medical Services (HEMS) are a critical component of modern emergency systems, enabling rapid access to advanced care in both urban and rural settings. While seasonal and regional variation in HEMS operations has been reported internationally, evidence from Poland based on standardized national data remains limited. We analyzed 5,272 dispatches recorded across 21 Polish HEMS bases between 10 March and 10 August 2025. Weekly and seasonal trends were examined using descriptive statistics, boxplots, and regression models. Dispatch composition was stratified into accidents, illnesses, and inter-hospital transports. Workload intensity was standardized per 100 duty-hours, and Poisson regression with base fixed effects and cluster-robust errors was used to compare daytime (07:00–20:00) and 24-hour bases. Weekly national dispatch totals fluctuated between 160 and 320, with a seasonal increase of 9.5% from spring (mean 228.8/week) to early summer (mean 250.5/week). Accidents accounted for 48.0% of all missions, illnesses for 39.5%, and inter-hospital transports for 12.5%. Accident-related missions increased significantly in early summer (OR 1.30, 95% CI 1.14–1.49), while illness missions decreased (OR 0.82, 95% CI 0.73–0.93); inter-hospital transports remained stable. Standardized workloads clustered closely around the national median of 10.1 missions/100 duty-hours (mean 10.4/100 h), with the busiest bases exceeding 12/100 h and the least busy reporting < 9/100 h. Regression models showed no significant differences between daytime and 24-hour bases (IRR 0.97–0.98; p > 0.7) and no interaction with season. The Polish HEMS system demonstrates stable per-hour workloads across bases, with seasonal surges in trauma driving short-term variability. Absolute differences between bases primarily reflect duty-hour configurations rather than differences in dispatch rates relative to time of availability. Resource planning may benefit from maintaining operational flexibility during periods of increased demand, particularly in summer months. Further studies covering longer observation periods and integrating meteorological, demographic, and injury data are needed to better understand the environmental and systemic drivers of HEMS workload.