Development of a new membrane-type heated humidifier for laparoscopic surgery

Recently, several animal studies showed that the core body temperature falls during pneumoperitoneum, and this hypothermia could be prevented by using heated and humidified gas insufflation. However, there are no satisfactory heated humidifiers to meet this purpose. Therefore, we developed a new membrane-type heated humidifier.

The newly developed heated humidifier employs an ion-exchange membrane (Nafion: Du Pont Co. Ltd) tube that passes water selectively in molecular form and a gas compartment is completely separated from distilled water to prevent infection. This humidifier consists of a Nafion tube assembly and a case that includes the heater. A perforated protecting tube is located outside the Nafion tube to prevent direct contact with the Nafion tube when it is assembled. The Nafion tube assembly is inserted in the case, and dry gas flows inside of the Nafion tube. The space between the case and the Nafion tube assembly is filled with distilled water. A heater raises the temperature of the distilled water, and heat and water vapor are transferred to cold and dry gas through the Nafion membrane. Four different types of insufflators were involved in this performance comparison study: a Nafion-based heated and humidified insufflator, a conventional heated insufflator, a conventional heated and humidified insufflator, and a conventional cold and dry insufflator. Temperature and relative humidity were measured once each minute for 15 min, which was repeated four times. Each insufflator was operated at two rates of flow: 5 L/min and 10 L/min.

Temperature and humidity of the conventional cold and dry insufflator, the Nafion membrane-type heated and humidified insufflator, the conventional heated insufflator, and the conventional heated and humidified insufflator measured at the distal end of circuit reached 22.0 +/- 0.2 degrees C and 0%, 36.7 +/- 1.1 degrees C and 100%, 29.0 +/- 0.4 degrees C and 0%, and 31.3 +/- 0.4 degrees C and 70.5 +/- 5.3% in 15 min at 5 L/min flow rates. At 10 L/min flow rates, temperature and humidity were almost the same as those at 5 L/min. The membrane-type heated humidifier demonstrated statistically significant improvement in both the temperature ( p < 0.0001) and relative humidity ( p < 0.0001) parameters in comparison to the conventional normal, heated, or heated and humidified insufflators at 5 L/min and 10 L/min continuous flow rate in statistics using repeated-measure ANOVA.

This newly developed heated humidifier offers the great advantages of maintaining intraabdominal temperature and humidity in comparison to conventional insufflators for laparoscopic surgery.