Do air pollutants levels during the previous 48 hours predict out-of-hospital cardiac arrest incidence compared to same-day pollutants levels?

Abstract Funding Acknowledgements None. Introduction Association between air pollutants (APs) levels and out-of-hospital cardiac arrest (OHCA) at the same day of the measurements have been previously described. Whether APs levels measured during the previous 48 hours may predict OHCA occurrence is not known. Purpose To analyse whether same-day APs levels compared to APs levels during the previous 48 hours are associated with OHCA incidence. Methods OHCA admissions on five Cardiac Intensive Care Units of our city were assessed during September-2020 to December-2021. Free access data regarding particulate matter (PM10), carbon monoxide (CO), nitrogen dioxide (NO2) and ozone (O3) levels during the same period were also registered. APs measures occurred each hour daily at three different spots, delivering more than 31000 measurements. APs levels during the previous 48 hours and during the index day were compared between OHCA-free days (OHCA-Fd) and OHCA-days. Results 179 patients were included. Main demographic characteristics are shown on table 1. Daily OHCA incidence and APs mean levels/month are shown in Table 2. As shown at table 3 same-day higher NO2 and lower O3 levels were found on OHCA-days compared to OHCA-fd: 41 ±10 vs. 36 ±9 µg/m3, p=0.016 for NO2 and 45 ±13 vs. 51 ±11 µg/m3, p= 0.003 for O3. As shown on Table 2 same day mean O3 levels were also higher from April to September compared to the rest of the year (p<0.001). OHCA incidence was lower in this same period (p<0.001). There wasn’t any association between OHCA incidence and APs (NO2, O3, PM10 and CO) measured at any moment during the event's prior 48 hours. Conclusions Same-day higher NO2 and lower O3 levels were associated to a higher OHCA incidence in our city. On the other hand, association between OHCA and NO2, O3, PM10 or CO measurements during the previous 48 hours was not found in our cohort. Reducing production of NO2 (i.e., reducing fossil-fuel consumption) may reduce OHCA risk during that same day.