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A healthy newborn infant acquired a substantial body burden of mercury by inhaling mercury vapor originating from a broken mercury expansion switch in the heating unit of an infant incubator. Highly toxic mercury vapor is produced in quantity by heating otherwise harmless metallic mercury. Switches and thermometers that contain mercury should be removed from infant incubators.
A new non-electric transport incubator has been developed for transferring babies between health facilities in developing countries. The temperature performance of this prototype was compared with a commercial electric incubator. The warm-up time for the prototype was 51.8 min, compared with 48.1 min for the electric incubator. Forty-five non-distressed premature babies, aged 24-72 h, with a gestational age of less than 37 weeks, were continuously evaluated for a 2 h period. Twenty-five babies, with a mean weight of 2073 g (range 1500-2500 g), were studied in the prototype, and 20 babies, with a mean weight of 2076g (range 1550-2500 g), were studied in the electrical incubator. The rectal and abdominal skin temperature, heart rate, oxygen saturation and respiratory rate of the babies were recorded. The temperature, oxygen and humidity level of the canopy and the room temperature were also measured. The SaO2, heart rate and respiratory rate were within the normal range (in the prototype: 96.5%, 130.5 beats min(-1) and 43 breaths min(-1), respectively; and, in the electric incubator: 96.5%, 128.5 beats min(-1) and 40 breaths min(-1), respectively). No evidence of carbon dioxide narcosis, hypoxia, acidosis or adverse thermoregulatory behaviour were observed in the two groups. The mean rectal temperature for both groups was within the range 36.5 degrees C-37.5 degrees C. There was no significant difference between the measurements of the two groups. The level of oxygen inside the canopy was 21%, and no decrease was observed. The new nonelectric transport incubator confirmed its safety and efficiency in providing a warm environment for non-distressed premature babies over a 2 h period.
Two models of infant incubators were studied to determine the strength of the magnetic field generated by the heater and fan motors. Measurements were taken at intervals along the center line of the incubator. The results show that fields greater than 100 milligauss and 25 milligauss were measured in the C-86 and C-100 model Isolettes, respectively.
The following acoustic effects of incubators were investigated: Noise level and vibration measurements inside incubators. Noise emanation into the vicinity of incubators. Deadening of incubator noise by the hood. The noise intensity inside the incubators was also registered under conditions of intensive care using sound emitting therapeutic and monitoring equipment. The results show that the noise level of incubator motors can be tolerated. This applies to well-serviced incubators only, however. The hood muffles outside noise, particularly in the range of greatest hearing acuity. But there is no protection against noisy intensive-care systems within the incubator. The infants own noise production is considered to contribute substantially to the noise within an incubator.
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The uneven distribution of the ambient temperature in a model of an infant incubator was demonstrated using the computational fluid mechanical (CFM) simulation of the air flow. A finite volume method of CFM calculation was performed on a three-dimensional (3D) model of an infant incubator including a model baby. The time course of the temperature distribution was computed solving the heat transfer equations simultaneously with the momentum equations. An uneven temperature distribution was observed for a long period (60 s) after the warm inflow was introduced into the incubator chamber. The temperature distribution was complex in 3D space and unsteady even after a long time, suggesting that it may take a considerable time to settle and may continue to be unsteady even if the inflow velocity is steady.
In a survey of 42 infant incubators 18 showed detectable concentrations of mercury vapor. In 12 instances the concentrations of mercury vapor in the thermometer holder exceeded industrial safety standards. In 16 incubators the contamination was traced to broken mercury-in-glass thermometers used to monitor incubator ambient temperatures. Use of alcohol thermometers or thermistors in place of mercury-in-glass thermometers would eliminate this potential hazard.
We have created a pilot wireless network for the convenient monitoring of temperature and humidity of infant incubators. This system combines infrared and radio frequency (RF) communication in order to minimize the power consumption of slave devices, and we therefore call it a hybrid wireless network. The slave module installed in the infant incubator receives the calling signal from the host with an infrared receiver, and sends temperature and humidity data to the host with an RF transmitter. The power consumption of the host system is not critical, and hence it uses the maximum power of infrared transmission and continuously operating RF receiver. In our test implementation, we included four slave devices. The PC calls each slave device every second and then waits for 6 s, resulting in a total scan period of 10 s. Slave devices receive the calling signals and transmit three data values (temperature, moisture, and skin temperature); their power demand is 1 mW, and can run for about 1000 h on four AA-size nickel-hydride batteries.
Two double-walled incubators, the Air Shields C-100 and the Ohio IC, were evaluated for performance characteristics. The Ohio incubator heated more rapidly from room temperature to 36 degrees C, but overshot the preset air temperature and produced greater fluctuation in air temperature due to the operation of the servocontrol system at equilibrium. Neither incubator produced excessive air currents, sound levels, or carbon dioxide accumulation.
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Air temperatures were continuously recorded inside four incubators with proportional heating control and six incubators with on/off heating cycles, during routine use. The air temperatures in the former were constant throughout, with a gradient between the roof and above-mattress air temperature not exceeding 1 degree C. In contrast, the recordings from the latter models showed a regular cyclical oscillation, the duration of the cycle varying from 14 to 44 minutes. Each incubator had a characteristic profile. The roof air temperature could vary by as much as 7-1 degrees C and the above-mattress air temperature by as much as 2-6 degrees C during the cycle. The oscillation persisted in the air temperatures recorded inside an open-ended hemicylindrical heat shield when used inside these incubators, but was markedly reduced inside a closed-ended heat shield, Carbon dioxide concentration did not increase significantly inside the latter.
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