To the Editor: Despite the risk of rapid respiratory failure 1 and cardiac complications 2 due to Covid-19, it is unclear whether there is an association between Covid-19 and out-of-hospital cardiac arrest. The Lombardy region of Italy was among the first areas to have an outbreak of Covid-19 outside China, 3 and the first case there was diagnosed on February 20, 2020, in Lodi Province. 4 Using the Lombardia Cardiac Arrest Registry (Lombardia CARe), we compared out-of-hospital cardiac arrests that occurred in the provinces of Lodi, Cremona, Pavia, and Mantua during the first 40 days of the Covid-19 outbreak (February 21 through March 31, 2020) with those that occurred during the same period in 2019 (February 21 through April 1, to account for the leap year). We reviewed daily reports of new Covid-19 cases recorded by the National Department of Civil Protection 5 and cases of out-of-hospital cardiac arrest in the electronic database of the emergency medical system to identify either symptoms suggestive of Covid-19 (fever lasting ≥3 days before out-of-hospital cardiac arrest, with cough, dyspnea, or both) or positive results of testing to detect SARS-CoV-2 in pharyngeal swabs obtained before the out-of-hospital cardiac arrest or after death. (Details are provided in the Supplementary Appendix, available with the full text of this article at NEJM.org.)During the study period in 2020, a total of 9806 cases of Covid-19 were reported in the study territory. During this period, 362 cases of out-ofhospital cardiac arrest were identified, as compared with 229 cases identified during the same period in 2019 (a 58% increase). Increases of various magnitudes in the numbers of cases of out-ofhospital cardiac arrest were seen in all four provinces (Table S1 in the Supplementary Appendix). The sex and age of the patients were similar in the 2020 and 2019 periods, but in 2020, the incidence

Aims An increase in out-of-hospital cardiac arrest (OHCA) incidence has been reported in the very early phase of the COVID-19 epidemic, but a clear demonstration of a correlation between the increased incidence of OHCA and COVID-19 is missing so far. We aimed to verify whether there is an association between the OHCA difference compared with 2019 and the COVID-19 epidemic curve. Methods and results We included all the consecutive OHCAs which occurred in the Provinces of Lodi, Cremona, Pavia, and Mantova in the 2 months following the first documented case of COVID-19 in the Lombardia Region and compared them with those which occurred in the same time frame in 2019. The cumulative incidence of COVID-19 from 21 February to 20 April 2020 in the study territory was 956 COVID-19/100 000 inhabitants and the cumulative incidence of OHCA was 21 cases/100 000 inhabitants, with a 52% increase as compared with 2019 (490 OHCAs in 2020 vs. 321 in 2019). A strong and statistically significant correlation was found between the difference in cumulative incidence of OHCA between 2020 and 2019 per 100 000 inhabitants and the COVID-19 cumulative incidence per 100 000 inhabitants both for the overall territory (ρ 0.87, P < 0.001) and for each province separately (Lodi: ρ 0.98, P < 0.001; Cremona: ρ 0.98, P < 0.001; Pavia: ρ 0.87, P < 0.001; Mantova: ρ 0.81, P < 0.001). Conclusion The increase in OHCAs in 2020 is significantly correlated to the COVID-19 pandemic and is coupled with a reduction in short-term outcome. Government and local health authorities should seriously consider our results when planning healthcare strategies to face the epidemic, especially considering the expected recurrent outbreaks.

We conclude that in COPD patients, different levels of PSV may induce different respiratory patterns and gas exchange. PS levels capable of obtaining a satisfactory equilibrium in blood gases may result in ineffective respiratory efforts if external PEEP is not applied. The addition of PEEPe, not exceeding dynamic intrinsic PEEP, may also reduce the metabolic work of the diaphragm without altering gas exchange.