In this study, we gathered data on the OHCA care provided by the Emergency Services in the Community of Madrid, Spain, one of the first European regions to suffer the effects of COVID-19. These data have enabled a detailed analysis of OHCAs during the successive waves of the pandemic, including a plateau phase after the first wave in which strict initial mitigation measures allowed transmission to be controlled, and to compare these periods with the same months in the year prior to the pandemic. We found no increase in the number of OHCAs during the pandemic year compared to the non-pandemic year. As far as we know, no other studies have made this comparison between full years, but some groups have compared specific periods during 2020 with their counterparts in the previous year. Although a few of these investigations showed differences in the number of OHCAs,15 most reported an increase during the pandemic period.5,6,16,17,18
Throughout the pandemic, response times have increased, as described above,5,19,6,20,16,17,21,22 because both resource activation and arrival times increased, as Lim et al. also reported.23 We did, however, observe response times at pre-pandemic levels during the pandemic plateau phase (Fig. 1), after which they increased again slightly.
In most studies, no significant differences were reported in terms of sex ratios, similar to our findings, but some studies have reported significantly higher patient ages during the pandemic period.16,18,24 This result contrasts with our findings and those of Rosell et al.,25 in both cases showing lower ages in this patient population, although usually not significantly so. The COVID-19 pandemic has clearly influenced all aspects of life, both because of its direct health effects and because of home lockdown–related measures implemented to varying degrees. As a result, during the pandemic year, the percentage of OHCAs taking place in homes increased,3,17,18,14,15,19,21,22,23 especially during the first wave, although this percentage later decreased, possibly because of easing lockdowns (Fig. 3).
We observed that resuscitation attempt rates decreased significantly during the first pandemic wave, as reported in other studies,5,20,16,17,22 but we also found that they recovered to non-pandemic levels during the remainder of the pandemic year (Fig. 1), which has not been previously assessed. The most common reason for non-resuscitation, especially in the first and third waves, was the excessive time between the OHCA and the arrival of the advanced life support. These longer periods between call placement and EMS arrival in the first and third waves could be the result of both a higher number of calls and greater awareness of the need to use personal protective equipment, leading to longer call-response times.
We found no significant differences in whether or not the airway was managed, but as other studies have indicated,6,24,25 supraglottic airway management devices were more commonly used during the pandemic period, a pattern that changed over time (Fig. 2). Even with the observed changes, the use of orotracheal tubes for airway management was still more common, despite recommendations otherwise.
As other researchers have reported5,16,17 during the pandemic year, the aetiology of OHCA was most frequently medical. Only during the plateau phase did this percentage drop, falling even to non-pandemic levels (Fig. 2).
As described in other studies,5,19,6,20,16,17,21,23,24,25,26 we found that OHCA survival at hospital admission was significantly reduced. One prediction might have been that as the first wave ended and COVID-19 incidence fell, the survival rate would have improved; however, it remained low, with no significant changes during the successive waves (Fig. 2). This pattern could be explained by the high probability of thromboembolism27 among patients who had suffered COVID-19 and its sequelae.
When comparing survival at the time of hospital discharge and comparing one-month survival rates, we found no significant differences for either between the pre-pandemic and pandemic years, but there was a trend towards worse survival during the pandemic. We also found no significant differences in these outcomes among the different periods of the pandemic.
The results of this study highlight the influence that COVID-19 has had on OHCA and on EMS activity, showing how the pandemic has increased stress on the Emergency Coordination Centre in terms of attending the population. In the community of Madrid, as in Nantes10 and Lausanne,28 the number of calls increased during the first pandemic wave, whereas some studies in other regions showed that the number of calls actually decreased.20,29 In Madrid, the increased number of EMS calls continued through the successive waves, and this overload led to a delay in activation times for available resources throughout the pandemic year. In some regions, where the calls decreased, activations often have decreased as well.9,20 In other places, however, despite an increased number of calls, resource dispatches decreased10 or remained the same, as in Madrid,30 with a similar pattern occurring during subsequent waves. One possible inference is that at times of high call volume, the various call handling systems significantly influenced how both resource dispatch and response time were handled, as Penverne et al. demonstrated.10
Limitations: This study has the limitations inherent to a prospective study starting on 15 March 2020 and involving comparison with retrospective data acquired from the SUMMA 112 OHCA registry. Although the variables were considered in the same way in all cases, some patient data may be missing, such as survival to hospital discharge and one-month survival. In addition, not knowing the underlying reason for the increase in resource mobilisation despite the increased number of calls creates a degree of uncertainty that we cannot address. Possible explanations include additional call handlers or new management guidelines. Another limitation is that according to some other studies,31 possibly only one of every ten COVID-19 positive cases was detected during the first wave, so that the actual incidence during this period could have been much higher than what official records indicate.