INTRODUCTION

The incidence of end-stage heart failure has risen due to the aging population in Japan. The total number of 119 calls in Yokohama has experienced a rapid increase, reaching approximately 200,000 cases annually. In Yokohama, about 4% of these cases are diagnosed with heart failure. If the current situation persists, more elderly patients with heart failure will be transported to the emergency center, even as end-stage heart failure (Stage D) cases and hospital bed capacity become increasingly strained. This could potentially lead to the collapse of the entire regional health care system.

In December 2019, the Japanese government implemented the Stroke and Cardiovascular Disease Control Act. This legislation underscores the pressing necessity to establish a new treatment system for elderly patients with heart failure.

The Yokohama Medical Control Council (Yokohama MC) has discussed strategies to protect against the potential collapse of the health care system in the future, given the aging population in Yokohama, which currently stands at 3.76 million people.

Continuous positive airway pressure (CPAP) therapy is one of the treatments available for heart failure. The “Acute/Chronic Heart Failure Clinical Practice Guidelines” published by The Japanese Circulation Society¹ emphasize the importance of early treatment for patients with heart failure, as it can help prevent aggravation of the condition. However, the benefits of early CPAP administration in prehospital emergency care settings in Japan have not yet been established. Currently, in Japan, the only way to administer early CPAP in the field is through a doctor's medical treatment. Consequently, the Yokohama MC has established dispatch criteria for Doctor Cars and developed a CPAP flowchart.

In Western countries, the National Association of EMS Physicians (2022) issued a statement recommending noninvasive ventilation, including prehospital CPAP therapy administration.² Besides, a systematic review conducted in 2015 by the National Institutes of Health reported that prehospital administration of CPAP therapy was associated with reduced mortality and intubation.^{3, 4} By contrast, there are no findings from Japan regarding the prehospital administration of CPAP therapy, with only case reports available for the postoperative administration of CPAP therapy.^{5, 6}

The aim of this study is therefore to describe the prehospital use of CPAP, which is already established as the first-line care in the emergency room for patients with heart failure but is being applied to patients transported by regional Doctor Cars (in Yokohama, utilizing the City 3–type Doctor Car system). However, currently in Japan, the law strictly prohibits paramedics from administering treatment. Therefore, the findings of this study could potentially contribute to the future consideration of granting fire station paramedics permission to administer such treatment.

METHODS

The regional Doctor Car system and CPAP equipment

In Yokohama City, with a population of 3.7 million, there are 2 types of Doctor Car systems (as of 2020). One was the All Yokohama Work-Station–type Doctor Car, and the other was the normal-type Doctor Car system, which included the Yokohama City University Medical Center Doctor Car and the National Hospital Organization Yokohama Medical Center Doctor Car. All Yokohama Work-Station–type Doctor Car's dispatch comprised one emergency doctor (from each emergency hospital in Yokohama), one nurse, and two or three fire station paramedics.

The Yokohama MC developed dispatch criteria for the Yokohama Doctor Car system (Table 1), which included patients with severe heart failure, and created a flowchart for the administration of CPAP in the field (Figure 1). We chose the Boussignac CPAP system (Figure 2A,B) due to its suitability for field use and safety features. The positive end-expiratory pressure can be monitored using a manometer within the Boussignac CPAP system (Figure 2D), which enhances patient safety and reduces the risk of pneumothorax.

TABLE 1. Doctor Car dispatch criteria by the Yokohama Medical Control Council (Yokohama MC).

Orthopnea with severe dyspnea due to potential heart failure. Accident with multiple victims. Sudden onset chest pain and back pain due to potential myocardial ischemia. Sudden onset headache and consciousness disorder due to potential Sub-arachnoid hemorrhage (SAH). Severe trauma decided by the high-energy category and the case with confirmed space medicine. Field Commander request.

• Note: The Yokohama MC established dispatch criteria for the Doctor Car system. Doctor Car dispatch is employed for patients with severe trauma, similar to other Doctor Car and Doctor-Heli systems. In Yokohama, Doctor Car dispatch is also utilized for patients with severe dyspnea.

The Yokohama MC provided training to fire station paramedics on the use of CPAP in the field (Figure 3). To mitigate the potential spread of aerosols to the Doctor Car's cabin, we incorporated a virus filter into the Boussignac system as a preventive measure against coronavirus disease 2019 (COVID-19; Figure 2C).

RESULTS

Between October 1, 2020, and January 23, 2022, a total of 661 Doctor Car dispatches were recorded. Among these, CPAP therapy was administered on-site in 13 cases. The median age (interquartile range) was 87 (79–94) years. Overall, 13 patients (92%) had a relevant previous medical history, including 1 (8%) with brain disease, 5 (38%) with heart disease, 4 (31%) with respiratory disease, 4 (31%) with cardiovascular disease, 1 (8%) with gastrointestinal disease, and 3 (23%) with other diseases such as diabetes mellitus. One additional patient (8%) was transferred from another institute due to the need for advanced treatment for carbon monoxide intoxication. Notably, there were no patients with psychiatric diseases.

In terms of the degree of illness, as documented in the medical records, 1 case (9%) was classified as mild, 5 cases (45%) as moderate, 4 cases (36%) as severe, and 1 case (9%) as serious. The median respiratory rate at contact (interquartile range) was 34% (30%–36%), heart rate was 99 (91–142) beats/min, systolic blood pressure was 148 (105–192) mmHg, and the body temperature was 36.6°C (36.2°C–36.7°C).

Regarding changes in SpO₂ over time, the median (interquartile range), excluding missing values, was 89% (83%–93%) without oxygen, 95% (94%–99.3%) with oxygen, and 100% (97%–100%) with CPAP (Table 2; Figure 4). The median on-site stay time (interquartile range) was 11 (9–24) min, and the arrival time from dispatch command to the hospital was 28 (16–36) min. Respiratory distress was caused by heart failure in 10 patients (91%) and pneumothorax in 1 patient (9%). Importantly, none of the patients’ conditions worsened after the use of CPAP.

DISCUSSION

The Yokohama MC engaged in discussions regarding the establishment of a new system in compliance with the Japanese law “Stroke and Cardiovascular Disease Control” within Yokohama City. As in other Japanese cities, the population aged over 70 years is increasing rapidly in this city; therefore, there is an urgent need to develop a novel and unique system for managing heart failure in an aging society. In response to the challenges posed by an aging society, the Yokohama MC determined that equipping CPAP attachments in the field represents one of the essential solutions for addressing heart failure.

We described the prehospital use of CPAP, a treatment modality already established as first-line care in emergency rooms for patients with heart failure, but now extended to patients transported via regional Doctor Cars. Currently, fire paramedics are strictly prohibited from performing medical treatments in Japan. As CPAP therapy falls under the category of medical treatment, fire station paramedics are not allowed to employ this procedure. In this study, CPAP therapy was administered by Doctor Car personnel, including doctors and fire station paramedics. The findings of this study are based on an uncontrolled analysis and a relatively small sample size. Although CPAP therapy was safely applied to our limited sample group, caution should be exercised when interpreting the findings. We anticipate that in the future, paramedics will gain the capability to utilize CPAP therapy in the field, potentially playing a crucial role in preventing health care system strain in our aging society.

The study was conducted during the COVID-19 pandemic in Japan. As CPAP therapy has the potential to generate aerosols that may be related to the transmission of the coronavirus, we decided to exclude patients with fever from the CPAP protocol as a precautionary measure. Because of the impact of the COVID-19 pandemic, the total number of cases included in the study was limited to 13.

CPAP is a positive airway pressure treatment that has the potential to promote or worsen pneumothorax, particularly in elderly patients. In this study, where the median patient age was 87 years, only one case was diagnosed with pneumothorax. However, no adverse events were observed during transportation to the hospital. The Boussignac CPAP system is equipped with a manometer to monitor the positive end-expiratory pressure levels, which enhances patient safety.

In this study, we conducted an examination based on a case series; nevertheless, parameters included in our research registry have the potential to be valuable for future large-scale observational studies. These parameters encompass variables such as sex, respiratory rate, and SpO₂, which are considered covariates or confounding factors in patient prognosis, as emphasized in the literature.³ However, partial pressure of oxygen (PaO₂) and partial pressure of carbon dioxide (PaCO₂) have also been identified as confounding factors.³ In the future, the quality of examinations can be significantly enhanced by integrating this information with data collected during hospitalization following transportation. According to the most recent randomized controlled trial conducted with inpatients with COVID-19 in the United States, the administration of CPAP therapy resulted in a significantly lower intubation rate (33.4% vs. 41.3%, p = 0.03) compared with the group receiving standard oxygen therapy. In addition, the mortality rate decreased; however, there was no significant difference between the groups (16.7% vs. 19.2%, p = 0.37).⁷ Conducting large-scale multicenter collaborative research on CPAP therapy administration in Japan will underscore the importance of combining background variables and confounding factors.

There are some limitations to our study. This was an observational study limited to cases in Yokohama City. Thus, it is necessary to perform further studies by accumulating more cases in the future.

CONCLUSION

The study, supported by a regional MC council (Yokohama MC), described the prehospital use of CPAP, a treatment modality already established as first-line care in emergency rooms for patients with heart failure, but now extended to patients transported via regional Doctor Cars. Because of the impact of the COVID-19 pandemic, the total number of cases included in the study was limited to 13. Thus, we were not able to draw firm conclusions regarding the safety and effectiveness of CPAP. To the best of our knowledge, this is the first report of a prospective observational study of prehospital CPAP therapy originating from Japan, making our attempt both clinically and academically significant. However, it is necessary to conduct large-scale multicenter cohort studies, accumulate cases, and control confounding factors identified in previous findings to achieve increased safety and effectiveness verification.

CONFLICT OF INTEREST STATEMENT

The authors have declared that there is no conflict of interest.

ETHICS STATEMENT

Approval of the Research Protocol: The Institutional Review Board of the Yokohama City University Medical Center reviewed and approved the study protocol.

Informed Consent: The IRB waived a requirement to obtain informed consent.

Registry and the Registration No. of the Study/Trial: Not applicable.

Animal Studies: Not applicable.