Surgical humidification is the conditioning of insufflation gas with water vapour (humidity) and heat during surgery. Surgical humidification is used to reduce the risk of tissue drying and evaporative cooling.
During laparoscopy (laparoscopic surgery or minimally invasive surgery), it is necessary to insufflate the abdominal cavity (i.e. inflate the abdomen like a balloon) with medical-grade carbon dioxide (CO2) to create a viewing and working space for the surgery. The CO2 may be unconditioned, or conditioned with heat, or with humidification and heat. During insufflation, the peritoneum (an extensive delicate membrane that lines the abdominal cavity and covers most of the abdominal organs) is exposed to the CO2.
Unconditioned medical-grade CO2 has virtually no moisture and enters the abdomen at room temperature (19 to 21 °C). The condition of the gas is dry and cold compared to that of the natural physiological state of the peritoneum which is immersed in fluid at body temperature (37 °C). Experimental and clinical investigations have demonstrated that insufflation with unconditioned CO2 causes evaporation of the fluid and drying of the peritoneum, resulting in inflammation and damage to its cells. Clinically, peritoneal injury caused by drying has been linked to post-operative pain, evaporative cooling resulting in a decrease in core temperature and increased risk of intra-operative hypothermia, as well as adhesion formation.
Conditioning the CO2 with only heat causes tissue drying also. Warmer gas has a greater capacity for evaporation as the gas can hold more water vapour; therefore, the tissues will dry faster than when unconditioned gas is used, potentially leading to increased adverse consequences.
Conditioning the CO2 with humidity, in combination with heat, has been shown to decrease peritoneal damage  by reducing the capacity of CO2 to carry moisture away from the tissue. Humidifying and heating CO2 during laparoscopic surgery lessens the risk of cellular damage to the peritoneum by reducing the drying effects of CO2.. Temperature loss during surgery, due to tissue drying, can be prevented by adequately humidifying and heating the CO2.
Methods of laparoscopic humidification
CO2 for laparoscopic surgery is conditioned with humidity and heat via devices such as the HumiGard™ Surgical Humidification System (Fisher & Paykel Healthcare Ltd, Auckland, New Zealand) and the Insuflow® (LEXION Medical, St Paul, USA). Such devices are positioned between the gas source and the patient interface.
The devices aim to condition the gas to body temperature and 100% Relative Humidity (although the exact temperature and humidity may vary slightly according to the manufacturer).
- United States Pharmacopoeia and the National Formulary Supplements. 26-NF 21. 3rd ed (United States Pharmacopeial Convention: 2003; NJ;). 2003.
- Puttick, M; Scott-Coombes D; Dye J; Nduka C; Menzies-Gow N; Mansfield A; Darzi A (1999). "Comparison of immunologic and physiologic effects of CO2 pneumoperitoneum at room and body temperatures". Surg Endosc 13 (6): 572–575. doi:10.1007/s004649901043.
- Erikoglu, M; Yol S; Avunduk MC; Erdemli E; Can A (2005). "Electron-microscopic alterations of the peritoneum after both cold and heated carbon dioxide pneumoperitoneum". J Surg Res 125 (1): 73–77. doi:10.1016/j.jss.2004.11.029.
- Peng, Y; Zheng M; Ye Q; Chen X; Yu B; Liu B (2009). "Heated and humidified CO2 prevents hypothermia, peritoneal injury, and intra-abdominal adhesions during prolonged laparoscopic insufflations". J Surg Res 151 (1): 40–47. doi:10.1016/j.jss.2008.03.039.
- Volz, J; Koster S; Spacek Z; Paweletz N (1999). "Characteristic alterations of the peritoneum after carbon dioxide pneumoperitoneum". Surg Endosc 13 (6): 611–614. doi:10.1007/s004649901052.
- Mouton, W G; Bessell JR; Otten KT; Maddern GJ (1999). "Pain after laparoscopy". Surg Endosc 13 (5): 445–448. doi:10.1007/s004649901011.
- Sajid, M; Mallick A; Rimpel J; Bokari S; Cheek E; Baig M (2008). "Effect of heated and humidified carbon dioxide on patients after laparoscopic procedures: a meta-analysis". Surg Laparosc Endosc Percutan Tech 18 (6): 539–546.
- Wills, VL; Hunt DR (2000). "Pain after laparoscopic cholecystectomy". Br J Surg 87 (3): 539–546. doi:10.1046/j.1365-2168.2000.01374.x.
- Bessel, J; Karatassas A; Patterson J; Jamieson G; Maddern G (1995). "Hypothermia induced by laparoscopic insufflation. A randomized study in a pig model.". Surg Endosc 9 (7): 791–796. doi:10.1007/bf00190083.
- Bessell, J; Ludbrook G; Millard S; Baxter P; Ubhi S; Maddern G (1999). "Humidified gas prevents hypothermia induced by laparoscopic insufflation: a randomized controlled study in a pig model". Surg Endosc 13 (2): 101–105. doi:10.1007/s004649900914.
- Noll, E; Schaeffer R; Joshi G; Diemunsch S; Koessler S; Diemunsch P (2012). "Heat loss during carbon dioxide insufflation: comparison of a nebulization based humidification device with a humidification and heating system". Surg Endosc.
- Sammour, T; Kahokehr A; Hill AG (2008). "Meta-analysis of the effect of warm humidified insufflation on pain after laparoscopy". Br J Surg 95 (8): 950–956. doi:10.1002/bjs.6304.
- Binda, M; Molinas C; Hansen P; Koninckx P (2006). "Effect of desiccation and temperature during laparoscopy on Adhesion formation in mice". Fertil Steril 86 (166-175).
- Benavides, R; Wong A; Nguyen H (2009). "Improved outcomes for lap-banding using the insuflow device compared with heated-only gas". JSLS 13 (3): 302–305.
- Bessel, J; Maddern G (1998). "Influence of gas temperatures during laparoscopic procedures". The Pathophysiology of Pneumoperitoneum.: 18–27.
- Slim, K; Bousquet J; Kwiatkowski F; Lescure G; Pezet D; Chipponi J (1999). "Effect of CO2 gas warming on pain after laparoscopic surgery: a randomized double-blind controlled trial.". Surg Endosc 13 (11): 1110–1114. doi:10.1007/s004649901184.
- Wills, V; Hunt D; Armstrong A (2001). "A randomized controlled trial assessing the effect of heated carbon dioxide for insufflation on pain and recovery after laparoscopic fundoplication". Surg Endoscopy 15: 166–170. doi:10.1007/s004640000344.
- Hazebroek, EJ; Schreve MA; Visser P; De Bruin RW; Marquet RL; Bonjer HJ (2002). "Impact of temperature and humidity of carbon dioxide pneumoperitoneum on body temperature and peritoneal morphology.". J Laparoendosc Adv Surg Tech A 12 (5): 355–364. doi:10.1089/109264202320884108.
- Mouton, WG; Bessell JR; Pfitzner JP; Dymock RB; Brealey J; Maddern GJ (1999). "A randomized controlled trial to determine the effects of humidified carbon dioxide insufflation during thoracoscopy". Surg Endosc 13 (4): 382–385. doi:10.1007/s004649900994.