ORIGINAL RESEARCH Improved Transport Incubator Temperature Control with Insulating Thermal Cover Andrew J. Macnab, MD, FRCPC,’ Dennis Schweers,* Marilynn D. Kendall, RN,3 Judy H. Komori, RN, BSN,3 Malcolm BiddIe British Columbia Children’s Hospital and British Columbia Ambulance Service (Pediatric Transport Program), Vancouver, B.C. Department of Biomedical Engineering, British Columbia Children’s Hospital, Vancouver, B.C. Special Care Nursery, British Columbia Children’s Hospital, Vancouver, B.C. Infant Transport Team, British Columbia Children’s Hospital, Vancouver, B.C. Key Words: cold stress, heat loss, hypothermia, neonate, radiation Address for correspondence: A.J. Macnab, MD, Director, Pediatric Transport Program, Division of Critical Care, B.C.‘s Children’s Hospital, 4480 Oak Street, Vancouver, B.C. V6H 3V4 Submitted: October 30, 1994 Revised: April 21, 1995 Accepted: April 22, 1995 Air Medical Journal 14:2 April-June 1995 Abstract Introduction: Cold stress, secondary to heat loss, can compromise infants in transport in- cubators during interfacility transfer. With cur- rent incubator designs, considerable radiant heat loss occurs. The use of additional exter- nal thermal insulation to reduce heat loss has been recommended for infant transports in cold environments. Method: A laboratory experiment was done to compare the rate of heat loss from a trans- port incubator with and without a commer- cially available, thermal insulating cover in place. The environment was a commercial freezer simulating subzero environmental tem- peratures. Measurements included air temper- ature inside the incubator and freezer, patterns of heater action and duration of battery power output. The significance of the different rates of cooling was compared using Pearson’s r. Suboptimal battery performance was ex- cluded by repeating one arm of the study with an external battery in place of the internal unit. Results: The rate of heat loss from the incu- bator was: 1) significantly slower when the covered and uncovered incubators were com- pared (f-2 = 0.52) and 2) essentially identical for the uncovered incubator with either the in- ternal or the external battery (r-2 = 0.96). Conclusion: In the laboratory setting, exter- nal thermal insulation slows transport incuba- tor radiant heat loss. Clinically, this effect likely would benefit infants at risk of cold stress dur- ing inter-facility transports. Introduction It long has been recognized that cold stress leads to increased mortality in low birth weight infants1 and that the risk of hypothermia is a potential hazard of neonatal transport.2J When transports take place in a cold environment, heat loss from the incubator increases. In many instances, even with the heater permanently on and with no interruption of power supply, the incubator tempera- ture will fall progressively. This means that many transport teams will experi- ence conditions where the ambient tem- perature within their incubators will fall unless additional measures are taken. This paper reports the laboratory trial of a thermal insulating cover that provides additional insulation and reduces heat loss from the transport incubator to the environment. Silverman’s4 series of randomized, controlled trials established the key role of incubation as a means of improving survival of small infants. Chances showed that to achieve rewarming in the tiny, sick neonate, it is necessary occasionally to operate incubators at temperatures in excessof 40” C. Wheldon6 suggests an in- creased awareness of the special environ- mental requirements of preterm infants has contributed to the improved survival of infants less than 30 weeks of gestation and that the provision of warmth is, per- haps, their most important requirement. LeBlanc7 confirms that keeping babies warm optimizes their chance of survival. Design changes continue to occur in medical devices for this purpose. 65