Abstract
BACKGROUND: Indoor CO(2) concentration is an important metric of indoor air quality (IAQ). The dynamic temporal pattern of CO(2) levels in intensive care units (ICUs), where healthcare providers experience high cognitive load and occupant numbers are frequently changing, has not been comprehensively characterized. OBJECTIVE: We attempted to describe the dynamic change in CO(2) levels in the ICU using an Internet of Things-based (IoT-based) monitoring system. Specifically, given that the COVID-19 pandemic makes hospital visitation restrictions necessary worldwide, this study aimed to appraise the impact of visitation restrictions on CO(2) levels in the ICU. METHODS: Since February 2020, an IoT-based intelligent indoor environment monitoring system has been implemented in a 24-bed university hospital ICU, which is symmetrically divided into areas A and B. One sensor was placed at the workstation of each area for continuous monitoring. The data of CO(2) and other pollutants (e.g., PM2.5) measured under standard and restricted visitation policies during the COVID-19 pandemic were retrieved for analysis. Additionally, the CO(2) levels were compared between workdays and non-working days and between areas A and B. RESULTS: The median CO(2) level (interquartile range [IQR]) was 616 (524-682) ppm, and only 979 (0.34%) data points obtained in area A during standard visitation were ≥ 1,000 ppm. The CO(2) concentrations were significantly lower during restricted visitation (median [IQR]: 576 [556-596] ppm) than during standard visitation (628 [602-663] ppm; p < 0.001). The PM2.5 concentrations were significantly lower during restricted visitation (median [IQR]: 1 [0-1] μg/m(3)) than during standard visitation (2 [1-3] μg/m(3); p < 0.001). The daily CO(2) and PM2.5 levels were relatively low at night and elevated as the occupant number increased during clinical handover and visitation. The CO(2) concentrations were significantly higher in area A (median [IQR]: 681 [653-712] ppm) than in area B (524 [504-547] ppm; p < 0.001). The CO(2) concentrations were significantly lower on non-working days (median [IQR]: 606 [587-671] ppm) than on workdays (583 [573-600] ppm; p < 0.001). CONCLUSION: Our study suggests that visitation restrictions during the COVID-19 pandemic may affect CO(2) levels in the ICU. Implantation of the IoT-based IAQ sensing network system may facilitate the monitoring of indoor CO(2) levels.