Disposable low-cost cardboard incubator for thermoregulation of stable preterm infant – a randomized controlled non-inferiority trial
Study objective: We determined whether thermoregulation of stable preterm infants at post-menstrual age 32 to 36 weeks and weight 1250 to 2250 grams in the low-cost incubator and thermoregulation of infants in standard single-wall incubator for 48 hours are comparable. Study end points: Maintaining axillary and skin temperature of infant in normal range from 36.5°C to 37.5°C for a period of 48 hours. If abnormal temperature i.e., axillary temperature < 36.5°C / > 37.5°C or apnea requiring bag and mask ventilation or any abnormal vital signs persisting for a duration exceeding 30 minutes infants would be taken out of study, and managed as per standard guidelines. We checked if the infants in low-cost incubator were maintaining hourly skin temperature, and axillary temperature measured 4th hourly were within non-inferiority limit of 0.2C. Place of study: Single centre study, in step-down neonatal intensive care unit and ‘KMC ward’ of Sri Ramachandra Medical College and Research Centre. Study intervention: Study incubators were assembled after hospital disinfection policy. After negative surface culture of incubators, infants were randomly nursed in either low-cost incubator or standard single-wall incubator in air-control mode and set-incubator temperature as per standard guidelines for 48 hours. Infant’s skin temperature measured by thermistor skin probe, axillary temperature measured by digital thermometer and vital signs were monitored. Incubator and ambient room temperature, humidity details measured by digital thermohygrometer were recorded. If infant develops any adverse events infant were taken out of study incubator and managed as per attending clinician decisions. Infants were observed till discharge for any untoward adverse events. Surface culture were taken from study incubators on day 3, day 5 and day 7 and incubators worked for 5 days in last set-air temperature. In post-infant period incubators are monitored by microbiology, temperature and humidity monitoring from day 3 to day 7. Findings: Median weight at enrollment for infants < 33 weeks and >= 33 weeks were similar in both groups. Mean skin and axillary temperature were lower in low-cost incubator group, but within the non-inferiority limit 0.2 C. In view of repeated measures, mixed model estimate for skin and axillary temperature were also within non-inferiority limit. ‘Failed thermoregulation’ occurred in none. Mild hypothermia occurred in 23% of standard incubator group and 33% low-cost incubator group. Incubator temperature in low-cost incubator was slightly higher. In post-infant period standard incubator and low cost incubator had excellent agreement to maintain set-temperature. Baseline characteristics, skin temperature, axillary temperature, incubator temperature, incubator humidity, room temperature, room humidity during 48 hour infant period and post-infant monitoring period are provided. Incubator surface culture details, nurses feedback of incubator are provided.