Cardiopulmonary resuscitation (CPR) guidelines recommend conventional CPR using ventilation combined with chest compressions for pediatric out-of-hospital cardiac arrests (OHCAs) (1–4), particularly in pediatric OHCAs of asphyxial etiology. Pediatric OHCAs are less likely to be cardiac in origin and are more frequently associated with a respiratory etiology than adult OHCAs (3). Sudden infant death syndrome (SIDS) is the leading cause of pediatric OHCAs (29.6%–59.5%), followed by airway obstruction, trauma, and submersion (5, 6).

In Japan and other countries, most pediatric OHCAs occur in preschool children (40.1%–69.8%), while infants account for 23.5%–47.4% (7–9) of pediatric OHCAs (7, 10). The incidence of infantile OHCAs is 75.3 per 100,000 infants per year, which is similar to adult OHCAs (11). The survival rate of pediatric in-hospital cardiac arrests have improved, but the survival rate of pediatric OHCAs remains poor (2, 12). For hospital admissions for OHCAs, the survival rates at discharge are 3.3% for infants and 9.1% for 1–11-year-old children (2). OHCAs in older children may occur during school and outdoor activities, but OHCAs in younger children are more likely to happen at home (7, 9). Therefore, family members are more likely to witness or detect OHCAs, and family CPR directly influences outcomes. Few reports have focused on preschool OHCAs, despite their high proportion among total pediatric OHCAs. Therefore, this study focuses on preschool OHCAs not witnessed by physicians or emergency medical services (EMS). The efficacy of conventional bystander CPR (BCPR) was compared with that of compression-only BCPR. We created a comprehensive OHCA database of preschool aged-patients by combining and reconciling a nationwide OHCA database with another database, including detailed information on locations, to investigate the relationship between characteristics of preschool OHCAs and the benefits of conventional BCPR.

Epidemiological features of OHCAs in preschool children and outcome-associated factors were identified using a nationwide database from Japan. During the study period, 3,709 OHCAs occurred in preschool children (≤6 years old), or 14.2 OHCAs per 100,000 preschool children per year. In all preschool pediatric OHCA cases that were analyzed, the neurologically favorable 1-M survival rate was 3.5% (101/2,882). Our results show that preschool-aged OHCA patients had much poorer neurological outcomes than schoolchildren-aged OHCA patients (6–18 years old) in Japan (18, 19). In this study, we investigated the factors that affect the neurologically favorable 1-M survival rate in preschool pediatric OHCA patients. We focused on preschool pediatric OHCA cases, over half of which included infants, and limited the analysis to BCPR, yielding meaningful results.

In Japan, diagnosis of SIDS is made by the attending physicians through autopsies and mortality studies (20). SIDS falls into different categories when diagnosed without an autopsy, making it difficult to determine the exact incidence from the data in this study. SIDS, the leading cause of OHCAs in infants, occurs during sleep, especially in the prone or side position (21). However, apparent life-threatening events such as apnea, asphyxia, and cyanosis are not risk factors (22). In addition, hypoxemia due to asphyxiates precedes cardiac arrest and reduces brain function and gasps (23). Preschool children are less likely to complain of abnormal symptoms than adults and fall quietly into OHCA. Additionally, family members may be unaware of impending death signs in infants and children. OHCAs may occur at night, during sleep (including naps), or when the family members are occupied in household chores, leaving their child unsupervised. Blind spots and everyday noise may also hinder the discovery of OHCAs in pediatric patients. In this study, the inclusion of trauma and submersion associated with asphyxia events in OHCAs was done as these causes seem to be characteristic of preschool pediatric OHCAs, as found in previous reports (24).

The proportion of preschool pediatric OHCA cases receiving BCPR was approximately 66%, similar to the Korean study (24) conducted on the same age group, and higher than that in previous all-pediatric OHCA studies (5, 10, 25). The high BCPR rate in preschool pediatric OHCA patients may be because most bystanders are family members. However, compression-only BCPR accounted for three-quarters of these BCPR cases, and the bystanders tended not to opt for conventional BCPR. The proportion of conventional BCPR in this study was lower than that reported in previous all-pediatric OHCA studies (6, 23, 25). For this reason, in the American Heart Association CPR guidelines of 2010 and later (1, 2), pediatric (≥1 year) CPR is delivered according to the adult basic life support algorithm and emphasizes the importance of chest compressions. However, the European Resuscitation Council CPR guidelines point out that ventilation is as important as chest compressions in pediatric OHCAs up to puberty (4). In addition, CPR for infants is not emphasized because the general public rarely encounters cardiac arrest in infants. Mouth-to-mouth-and-nose rescue breathing in infants and children and chest compressions in infants are difficult to remember and to complete (26). It is possible that conventional CPR was not performed because bystanders lacked the knowledge of CPR procedures for infants and children. Consequently, intensive education is needed, especially for family members, about pediatric OHCAs and proper resuscitation procedures and measures.

In this study, before and after propensity score matching, conventional BCPR was associated with a higher neurologically favorable 1-M survival rate than compression-only BCPR. In addition, subgroup analyses after propensity score matching showed that in nonmedical and unwitnessed OHCA cases, neurological outcomes in the conventional BCPR group were significantly better than those in the compression-only BCPR group. Hypoxic-ischemic brain injury after cardiac arrest is the primary cause of poor mortality and neurological prognosis (27). Correction of hypoxemia and regional cerebral oxygen saturation by early ventilation during resuscitation has been shown to contribute to the achievement of ROSC and improvement of brain function prognosis (28). In this study, the ROSC rate was higher in conventional BCPR than in compression-only BCPR. In nonmedical causes, respiratory abnormalities due to trauma to the head or chest and rapid hypoxemia due to asphyxiation or drowning result in cardiac arrest; therefore, early ventilation is essential (2, 3, 29). During compression-only CPR, body-tored oxygen is distributed for up to 4 min after cardiac arrest (29). Considering that only one-fourth of the OHCAs in our study were witnessed, this should highlight concern for unwitnessed OHCA cases were thought to have already developed hypoxemia and early ventilation is required. In these two subgroups, oxygenation by early ventilation was adequate for subsequent brain resuscitation, which might have led to an improved neurologically favorable 1-M survival rate.

In this study, despite the high incidence of the medical cause of preschool pediatric OHCAs, only a few OHCA cases with shockable initial rhythm and prehospital defibrillation occurred, similar to that in a previous report (9). This finding of relatively few shockable initial rhythm events would also be consistent with a previous report stating that respiratory etiologies are more common than cardiac etiologies. However, the majority of OHCAs were unwitnessed, and it is possible that the shockable initial rhythm immediately after cardiac arrest changed to another ECG rhythm upon EMS arrival.

Conventional BCPR was not found to be superior to compression-only BCPR in OHCA cases due to medical causes probably because oxygen deficiency in medical OHCAs is less severe than that in non-medical OHCA, including submersion and asphyxia. Furthermore, tissue hypoxia progresses after cardiac arrest in medical OHCAs.

Without training in pediatric CPR, a bystander cannot perform CPR properly and has limited guidance from emergency medical dispatches. In this study, one-third of preschool pediatric OHCAs did not undergo BCPR, and a quarter of those who did, underwent conventional BCPR. Despite great interest in pediatric CPR in Japan, the lack of opportunities for CPR training may be another reason for the low rate of BCRP. Thus, focusing on educating family members living with preschool children and childcare facility staff about the importance of pediatric CPR, and increasing awareness about the risk of cardiac arrest occurring outdoors and at home, is warranted.

This study examined preschool pediatric OHCA patients, about half of whom were under one year of age. Although preschool pediatric OHCA is characterized differently from all-pediatric OHCA, a direct comparison with previous all-pediatric OHCA was not done due to the disparate age ranges. In addition, similar studies focusing on OHCA in preschool children are scarce and should be further investigated worldwide. EMS personnel interviewed the bystanders for factors associated with OHCA and also performed resuscitative efforts; however, bystander reports before EMS contact with the patient may be inaccurate. This study did not investigate the amount of administered epinephrine doses and the time from the onset of OHCA to the initiation of resuscitation; therefore, the neurological outcomes may have been affected. EMS reaction time, experience with CPR training, social status, and educational level, and other extrinsic factors may influence the relationship between the types of BCPR and a favorable neurological prognosis. Finally, the current study concluded at the end of 2019, effectively outside of the window of COVID-19 impact (30, 31). Therefore, we were not able to consider or compare the potential effects of current CPR standards on OHCA outcomes. This may be an area for further research.

Bystanders, primarily families, rarely perform conventional BCPR for preschool pediatric OHCA patients. However, conventional BCPR increases the neurologically favorable outcomes of nonmedical and unwitnessed OHCAs. In pediatric OHCAs, which are often associated with a respiratory etiology, hypoxic-ischemic brain injury after cardiac arrest contributes to poor mortality and neurologic prognosis.