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.
Laparoscopic surgery humidification
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.
In addition, animal studies have revealed that surgical humidification reduces peritoneal tumor implantation and tumor load  suggesting a possible benefit in cancer patients undergoing abdominal surgery.
Conditioning the CO2 with only heat causes tissue drying. Warmer gas has a greater capacity for evaporation as the gas can hold more water vapor, 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. Temperature loss during surgery, due to tissue drying, can be prevented by adequately humidifying and heating the CO2.
Open surgery humidification
During open surgery the surgeon exposes the peritoneal cavity to the ambient air. Exposure to ambient air results in evaporation and cooling. Current studies have shown that the use of surgical humidification during open abdominal surgery (laparotomy) have warmer core body temperatures and reduced risk of operative hypothermia. As with any operation, maintaining patient normothermia is a critical process to prevent surgical site infections, additional respiratory distress and surgical bleeding.
Methods of surgical 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. CO2 for open surgery has been conditioned to date with the HumiGard™ Surgical Humidification System. These 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. Missing or empty
- 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. PMID 18639246.
- 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).
- Binda, Maria Mercedes; Corona, Roberta; Amant, Frederic; Koninckx, Philippe Robert (2014-07-01). "Conditioning of the abdominal cavity reduces tumor implantation in a laparoscopic mouse model". Surgery Today. 44 (7): 1328–1335. doi:10.1007/s00595-014-0832-5. ISSN 1436-2813. PMC . PMID 24452508.
- Carpinteri, Sandra; Sampurno, Shienny; Bernardi, Maria-Pia; Germann, Markus; Malaterre, Jordane; Heriot, Alexander; Chambers, Brenton A.; Mutsaers, Steven E.; Lynch, Andrew C. (2015-12-01). "Peritoneal Tumorigenesis and Inflammation are Ameliorated by Humidified-Warm Carbon Dioxide Insufflation in the Mouse". Annals of Surgical Oncology. 22 Suppl 3: 1540–1547. doi:10.1245/s10434-015-4508-1. ISSN 1534-4681. PMC . PMID 25794828.
- Davey, Andrew K.; Hayward, Jessica; Marshall, Jean K.; Woods, Anthony E. (2013-01-01). "The effects of insufflation conditions on rat mesothelium". International Journal of Inflammation. 2013: 816283. doi:10.1155/2013/816283. ISSN 2090-8040. PMC . PMID 23864985.
- Benavides, Richard; Wong, Alvin; Nguyen, Hoang (2009-09-01). "Improved outcomes for lap-banding using the Insuflow device compared with heated-only gas". JSLS: Journal of the Society of Laparoendoscopic Surgeons / Society of Laparoendoscopic Surgeons. 13 (3): 302–305. ISSN 1086-8089. PMC . PMID 19793466.
- Bessel, J; Maddern G (1998). "Influence of gas temperatures during laparoscopic procedures". The Pathophysiology of Pneumoperitoneum.: 18–27.
- 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, Eric J.; Schreve, Michiel A.; Visser, Pim; De Bruin, Ron W. F.; Marquet, Richard L.; Bonjer, H. Jaap (2002-10-01). "Impact of temperature and humidity of carbon dioxide pneumoperitoneum on body temperature and peritoneal morphology". Journal of Laparoendoscopic & Advanced Surgical Techniques. Part A. 12 (5): 355–364. doi:10.1089/109264202320884108. ISSN 1092-6429. PMID 12470410.
- Frey, Joana M.; Janson, Martin; Svanfeldt, Monika; Svenarud, Peter K.; van der Linden, Jan A. (2012-11-01). "Local insufflation of warm humidified CO₂increases open wound and core temperature during open colon surgery: a randomized clinical trial". Anesthesia and Analgesia. 115 (5): 1204–1211. doi:10.1213/ANE.0b013e31826ac49f. ISSN 1526-7598. PMID 22886839.
- Frey, Joana M. K.; Janson, Martin; Svanfeldt, Monika; Svenarud, Peter K.; van der Linden, Jan A. (2012-11-01). "Intraoperative local insufflation of warmed humidified CO₂ increases open wound and core temperatures: a randomized clinical trial". World Journal of Surgery. 36 (11): 2567–2575. doi:10.1007/s00268-012-1735-5. ISSN 1432-2323. PMID 22868970.
- Baucom, Rebeccah B.; Phillips, Sharon E.; Ehrenfeld, Jesse M.; Muldoon, Roberta L.; Poulose, Benjamin K.; Herline, Alan J.; Wise, Paul E.; Geiger, Timothy M. (2015-06-01). "Association of Perioperative Hypothermia During Colectomy With Surgical Site Infection". JAMA surgery. 150 (6): 570–575. doi:10.1001/jamasurg.2015.77. ISSN 2168-6262. PMID 25902410.
- Rajagopalan, Suman; Mascha, Edward; Na, Jie; Sessler, Daniel I. (2008-01-01). "The effects of mild perioperative hypothermia on blood loss and transfusion requirement". Anesthesiology. 108 (1): 71–77. doi:10.1097/01.anes.0000296719.73450.52. ISSN 1528-1175. PMID 18156884.