Brazilian Journal of Anesthesiology
https://app.periodikos.com.br/journal/rba/article/doi/10.1590/S0034-70942005000100008
Brazilian Journal of Anesthesiology
Scientific Article

Sistemas respiratórios com absorção de CO2, circulares, valvulares: comparação do comportamento térmico entre sistema coaxial e convencional com diferentes fluxos de gás fresco

Anesthesia breathing systems with CO2 absorption, circle valve circuit: comparison of thermal behavior of coaxial system and conventional system with different fresh gas flows

Marcelo Luís Abramides Torres; Eduardo Tsuyoshi Yamaguchi; Ubirajara Sabbag Fonseca

http://dx.doi.org/10.1590/S0034-70942005000100008 Braz J Anesthesiol, vol.55, n1, p.72-77, 2005
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Resumo

JUSTIFICATIVA E OBJETIVOS: A manutenção da temperatura do gás inalado pelo paciente durante o procedimento anestésico é fundamental para evitar complicações respiratórias durante o peri-operatório. O objetivo deste estudo é comparar a capacidade de aquecimento dos gases inalados em sistemas respiratórios com absorção de CO2, circulares, valvulares, coaxial e convencional, variando o fluxo de gás fresco (FGF). MÉTODO: Foram estudados dois sistemas respiratórios em um simulador de pulmão, que foi ventilado com volume corrente de 600 mL e freqüência de 10 bpm. O modelo simulava a produção de CO2, através da administração de fluxo de 250 mL.min-1 de CO2, e o gás exalado do pulmão-teste passava por um umidificador aquecido para simular o gás expirado. Os dois sistemas foram classificados como circulares, valvulares, com absorção de CO2. No sistema A (coaxial), o ramo inspiratório passava pelo interior do ramo expiratório, enquanto que o sistema B foi o convencional. As medidas de temperatura do gás inalado foram realizadas nos momentos 0, 5, 10, 20, 30, 40, 50, 60 e 90 minutos, sendo empregados FGF baixos (0,5 e 1 L.min-1) e altos (3 e 6 L.min-1). RESULTADOS: O sistema A apresentou variação térmica significativa entre o início e o final dos ensaios (22,47 ± 1,77 ºC e 24,27 ± 3,52 ºC p < 0,05, respectivamente). Os sistemas A e B produziram temperaturas semelhantes ao final do estudo (24,27 ± 3,52 ºC e 23,61 ± 1,93 ºC, respectivamente), e não houve diferença entre as temperaturas finais dos sistemas e a temperatura ambiental (21,25 ± 1,20 ºC e 21,81 ± 1,87 ºC, respectivamente). A utilização de baixos FGF produziu temperaturas semelhantes às temperaturas observadas ao final do estudo com fluxos mais elevados nos dois sistemas (A: 25,53 ± 4,78 ºC e 23,02 ± 0,80 ºC; B: 24,50 ± 0,85 ºC e 22,72 ± 2,36 ºC, respectivamente). CONCLUSÕES: O sistema coaxial apresentou variação térmica significativa entre o início e o final do experimento, o que não foi observado no sistema convencional. Não houve diferença das temperaturas finais quando comparados os dois sistemas entre si, independentemente do FGF empregado.

Palavras-chave

EQUIPAMENTOS, EQUIPAMENTOS, GASES

Abstract

BACKGROUND AND OBJECTIVES: The adequate maintenance of inhaled gases temperature during anesthetic procedures is critical to prevent perioperative respiratory complications. This study aimed at comparing the ability to warm up inhaled gases of coaxial breathing system and conventional system, by varying fresh gas flows (FGF). METHODS: Breathing systems were tested in a lung simulator ventilated with 600 mL tidal volume and respiratory frequency of 10 bpm. The model simulated human CO2 production by delivering 250 mL.min-1 of CO2 flow. Then, exhaled gas from the model was directed to a pre-warmed humidifier to simulate human exhaled gas. Both systems were classified as circle, valve circuits with CO2 absorption. In the coaxial system (model A), the inspiratory branch was enveloped by the expiratory branch, whereas the conventional one (model B) presented separated respiratory branches. Inhaled gas temperature was measured at the following moments: 0, 5, 10, 20, 30, 40, 50, 60 and 90 minutes, with low (0.5 and 1 L.min-1) and high (3 and 6 L.min-1) FGF. RESULTS: Model A presented significant thermal variation between beginning and end of experiment (22.47 ± 1.77 ºC and 24.27 ± 3.52 ºC respectively, p < 0.05). Both models A and B produced similar temperatures at the end of the study (24.27 ± 3.52 ºC and 23.61 ± 1.93 ºC respectively). There was no difference between final temperatures of both models and environmental temperature (21.25 ± 1.20 ºC and 21.81 ± 1,87 ºC respectively). Low FGF has produced similar temperatures to those observed at the end of the study with higher flows in both models (A: 25.53 ± 4.78 ºC and 23.02 ± 0.80 ºC; B: 24.50 ± 0.85 ºC and 22.72 ± 2.36 ºC, respectively). CONCLUSIONS: The coaxial system presented significant thermal variation between beginning and end of experiment, while this was not observed in the conventional one. No difference was observed in final temperatures when comparing both systems, regardless of the FGF.

Keywords

EQUIPMENTS, EQUIPMENTS, GASES

Referencias

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