Heat and moisture exchangers and the body temperature: a peroperative study

Abstract

The importance of conditioning the inhaled gas for maintaining the body temperature during artificial respiration was investigated. The mean body temperature (MBT) was deduced from readings from five measuring sites, four of which were situated at the skin and the fifth in the rectum. Temperature recordings were made every 15th min. Twenty patients were admitted to the study. In 10 patients a heat and moisture exchanger was used (the HME group), and the other 10 were ventilated without an HME (the control group). The patients were normoventilated, and a non-rebreathing system was used. All operations were made in the ENT-region of the body. Great care was taken to avoid variation of external factors that may affect the MBT. We found that the MBT decreased 0.2 degrees C/h less in the HME group than in the control group. If corrections were made for differences in amounts of fluids given and age factors, a difference in heat loss of 41.6 kJ/h between the two groups could be derived from this figure. This difference was statistically significant. Our finding correlated fairly well with a predicted reduction of heat loss of 26.0 kJ/h for the type of HME used. A certain margin of error seemed to be inevitable in measuring body temperatures, and the reason for this is discussed. Our results support the fact that the investigation is adequately designed, and that the heat conserved with an HME is rather low.

Efficacy of a heat and moisture exchanger in inhalation anesthesia at two different flow rates

“…However, Johansson and colleagues [8] reported that an HME did not prevent an early redistribution of body heat, and it also did not maintain the body temperature in the absence of concomitant heating methods. Eckerbom and Lindholm [13] also reported that the heat conserved with an HME was rather low. Therefore, when a circulating-water mattress is used, HME may have no more additive effects to help in maintaining the body temperature, although there were no control data for the absence of a circulating-water mattress in the present study.…”

Do heat and moisture exchangers in the anaesthesia breathing circuit preserve body temperature in dogs undergoing anaesthesia for magnetic resonance imaging?

“…Also, many factors affect the efficacy of the HME; whether they are hydrophobic or hygroscopic (Dorsch & Dorsch 2014), the initial humidity of the gas, the fresh gas flow and the existence of a leak in the breathing system (Gedeon et al 1987). In the human literature it is well described that hygroscopic HMEs have better heat conserving and exchanging properties than the hydrophobic HMEs used in our study (Eckerbom & Lindholm 1990;Sottiaux et al 1993;Martin et al 1994). Also the higher the fresh gas flow, the less efficient the HME is in conserving heat and moisture (Eckerbom & Lindholm 1990).…”

Umidificação e aquecimento do gás inalado durante ventilação artificial com baixo fluxo e fluxo mínimo de gases frescos

“…Os autores observaram que o sistema respirató-rio sem absorvedor e com alto fluxo de gases frescos mostrou valores significativamente menores da umidade relativa (entre 37% a 39%) e absoluta (entre 8 a 9 mg H 2 O.L -1 ) do que o grupo com baixo fluxo e absorvedor de CO 2 , quando a umidade relativa ficou ao redor de 75% a 79% e a umidade abso- , mas, em nossa opinião, o menor limite de umidificação durante a anestesia é difícil de determinar 1 , porque ele depende da duração da anestesia, das condições pulmonares prévias do paciente e do sistema respiratório empregado. Os estudos referentes à umidificação foram feitos especialmente em animais de laboratório 8, [32][33][34][35] . Investigações no homem são limitadas pelo pequeno número de pacientes envolvidos em cada pesquisa e a ausência de informações sobre os pacientes envolvidos em cada estudo 2,17 .…”

“…, but, in our opinion, it is difficult to determine the lowest humidification limit during anesthesia 1 because it depends on anesthesia duration, previous pulmonary conditions and the respiratory system used. Humidification studies were primarily performed with animals 8, [32][33][34][35] . In men, investigations are limited by the small number of patients involved and the lack of information about patients involved in each study 2,17 .…”

“…No segundo canal, utilizou-se a temperatura da cal sodada, por meio de sensor fixado na parede externa do canister, em sua parte inferior, em local em que a temperatura foi mais elevada. A leitura dos atributos de umidade e de temperatura foi feita nos momentos: M 0 (controle) -imediatamente, após a instalação do sistema ventilatório, de acordo com o grupo estudado, que ocorreu após 10 minutos da instalação do sistema de ventilação com a utilização de fluxo de oxigênio de 2 L.min 35,7) 36,9* (36,4-38,5) # p < 0,05: FM > BF em M 90 * p < 0,05: BF e FM: M 0 < M 30 < M 60 < M 90 < M 120 em relação à temperatura do canister * p < 0,05: BF e FM: M 0 < (M 30 = M 60 ) < (M 90 = M 120 ) em relação à temperatura da placa junto ao sistema expiratório go do tempo nos dois grupos (p < 0,05) (Tabela IV). A temperatura da placa junto ao sistema expiratório não apresentou diferença significante entre grupos (p > 0,05), mas aumentou ao longo do tempo nos dois grupos (p < 0,05).…”