Association of a smartphone-based CPR assistance system with prehospital outcomes in out-of-hospital cardiac arrest: a pre-post observational study in Bangkok.

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) remains a major public health challenge. Smartphone-based systems may facilitate early bystander response; however, their real-world associations with patient outcomes following implementation within emergency medical service (EMS) systems remain uncertain.

OBJECTIVE

This study aimed to evaluate the association between system-level implementation of the MySOS application and prehospital and clinical outcomes among patients with OHCA in Bangkok.

METHODS

We conducted a retrospective uncontrolled before-after observational study of patients with OHCA in Bangkok, Thailand, between December 2022 and May 2024. Patients were classified according to the pre- and post-implementation periods of the MySOS application. Inverse probability of treatment weighting (IPTW) and weighted multivariable regression were used to account for measured differences between the study periods. Given the temporal definition of exposure and absence of confirmed patient-level application use, findings were interpreted as associations rather than causal effects.

RESULTS

Among 615 patients, 340 (55.3%) were included in the pre-implementation period and 275 (44.7%) in the post-implementation period. The post-implementation period was associated with a higher probability of return of spontaneous circulation (ROSC) (adjusted RD 6.28%, 95% CI 1.69-10.86; p = 0.007), although the corresponding RR was not statistically significant (RR 1.21, 95% CI 0.78-1.89). Differences in death at the scene were also observed between study periods (adjusted RD 14.70%, 95% CI 9.14-20.27; p < 0.001). No statistically significant differences were observed in 24-h survival, survival to hospital admission, or survival to hospital discharge.

CONCLUSIONS

The post-implementation period of the MySOS system was associated with a higher probability of ROSC, but not with improved longer-term survival outcomes. These findings should be interpreted cautiously because of the uncontrolled before-after design, residual baseline imbalance, potential temporal confounding, and the absence of patient-level data confirming actual application use. Further prospective studies incorporating direct measures of MySOS activation and utilization are warranted.