新型冠状病毒肺炎疫情下综合医院发热门诊环境监测与感染控制

Environmental monitoring and infection control of fever clinics in general hospitals during COVID-19 pandemic

新型冠状病毒肺炎疫情暴发初期,社会性恐慌导致感染新型冠状病毒的患者和有类似症状的患者涌向医院,尤其是发热门诊.此外,还有部分已感染新型冠状病毒的患者到医院其他科室就诊.疫情初期,由于医护人员个人防护物资储备不足及防护意识不到位,部分医护人员被感染,因此,必须严格控制医院内环境,减少医院内近距离人际接触频率,防止新型冠状病毒通过飞沫、接触等途径传播.本研究以清华大学附属北京清华长庚医院为例,基于二氧化碳(CO2)浓度的实时监测,建立了评估医院通风稀释情况、预警发热门诊内患者间传播风险的环境控制方法.根据发热门诊候诊区走廊、护理站和医生诊室在室人数限值及规定新风量,计算出上述区域内二氧化碳浓度理论上限值.环境监测期间,医护人员均采取二级防护,未有医患间感染发生;共接诊5名新型冠状病毒肺炎确诊患者,确诊患者停留在发热门诊期间,就诊患者佩戴口罩,候诊区走廊、护理站和医生诊室二氧化碳浓度均低于理论上限值且分别控制在609、654和711 ppm(1 ppm=10–6 mol/mol)以下,患者间未发生交叉感染.该经验与方法可供同类型综合医院发热门诊设计与改造参考.

The early stage of the COVID-19 epidemic happened to be the flu season. Since some symptoms of influenza and COVID-19 are similar, symptomatic patients flocked to fever clinics and emergency departments. Meanwhile, asymptomatic COVID-19 patients attending other departments in general hospitals made things worse. Lack of knowledge of the pathogen, absence of awareness and short of personal protective equipment all posed threat to healthcare workers as well as other patients. As SARS-Co V-2 can be spread via droplets, direct contacts and potentially aerosols, the indoor air environment of hospitals, especially fever clinics, must have strict measures to prevent hospital-acquired infection.Thirty-two sensors were deployed in the Tsinghua University Affiliated Beijing Tsinghua Changgung Hospital(mentioned as Changgung Hospital hereinafter) from January 30, 2020, in order to monitor high-resolution real-time indoor environmental parameters at its fever clinic, isolation wards and other departments. One sensor monitors and records CO2 concentration, PM2.5 mass concentration, relative humidity, temperature and illuminance every 5 minutes. Six sensors were located at the fever clinic, where all patients with fever and/or other COVID-19 related symptoms firstly attended after arriving at the hospital. The clinic has two parts, one for diagnosis and the other for quarantine. Three sensors were placed in doctor’s office, nursing station and waiting area in the diagnosis part, respectively. Natural ventilation was chosen to dilute the environment, as the flowrate of outdoor airflow was abundant in Beijing’s winter.Atmospheric CO2 concentration surrounding Changgung Hospital was stable, and the rise of indoor CO2 concentration was caused by human exhalation. During this pandemic, CO2 concentration can be regarded as an indicator of room ventilation condition and hospital congestion, if all the people in hospital were regarded as potential infector of SARSCo V-2. According to the usage pattern of the fever clinic, the maximum number of patients in each functional area was set as 4 for doctor’s office, 4 for nursing station and 11 for waiting area. According to the ventilation regulation of infectious disease hospital, the air change rate at fever clinics should be at least 6 h–1. In addition, the outdoor CO2 concentration was assumed to be 400 ppm. Based on these conditions, the upper limits of indoor CO2 concentration were 902, 864 and867 ppm for doctor’s office, nursing station and waiting area at the Changgung Hospital’s fever clinic, respectively. Indoor CO2 concentration exceeding these thresholds stands for poor ventilation or overcrowds. Fortunately, this didn’t happen during the monitoring period and indoor CO2 concentration didn’t exceed 609–711 ppm. In another word, natural ventilation was sufficient and effective in this specific case at the Changgung Hospital’s fever clinic. Moreover, together with environment disinfection and personal protective measures, good ventilation condition led to no COVID-19 hospitalacquired infection.To conclude, this article introduced a real-time environmental monitoring campaign at the Changgung Hospital’s fever clinic. Similar methodology can help assess ventilation conditions and risk of hospital-acquired infection at the fever clinic during and after COVID-19 pandemic. Once indoor CO2 concentration exceeds the set thresholds, areas with high infection risk can be identified rapidly and timely, so that prevention measures can be taken in time.