Efeito da umidificação dos gases anestésicos nas propriedades físicas e transportabilidade do muco respiratório durante anestesia geral / Effects of inspired gases humidity on respiratory mucus in patients under general anesthesia

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Background: In patients who are intubated, the natural mechanism of gas climatization by the nose and the upper airway is bypassed. During anesthesia, when the inspiratory gases are cold and dry, humidification of gases is recommended to prevent drying of the mucosal epithelium and respiratory secretions. The anesthesia systems have inherent humidifying properties as a result of the valvular rebreathing of some of the expired humidity and of the production of water in the CO2 absorber. However, the level of moisture in anesthetic ventilation is critically dependent on several factors that include the equipment, the arrangement of the circle breathing system and the fresh gas flow. To date the effect of humidity on respiratory mucus properties and transportability was not investigated. Objectives: The objective of this study was to measure the humidity and temperature of the inspired gas from a circle absorber system in two different ventilators (Dräger and Takaoka) and the effect of a heat and moisture exchanger (HME) on the inspired gas. Furthermore, we also evaluated the impact of humidity on in vitro mucus transportability and physical properties. Methods: We studied 44 patients with no pulmonary disease scheduled for elective surgery that were randomly allocated in four groups according to the anesthetic equipment (Dräger or Takaoka) and the absence or presence of HME. Respiratory mucus was collected and Temperature (T), absolute humidity (AH), relative humidity (RH) of inspired gases were recorded immediately after intubation (T0) and every 2 hours. In vitro respiratory mucus was studied by mucociliary transportability (MCT) by the frog palate method; cough clearance (CC) by the cough equipment, and contact angle (CA) by direct observation. Results: Dräger equipment delivered significantly higher levels of RH and AH when compared to Takaoka. The addition of HME increased AH and T in both equipments. RH was improved only in the Takaoka equipment. MCT, CC showed a non-significant trend to be higher in the group that provided the highest humidity (i.e Dräger + HME). CA did not change among groups. Longitudinal analysis showed that MCT was positively affected by an increase in AH and RH. CC was positively affected by the addition of HME. Conclusion: Our results showed that Dräger equipment was more effective in humidifying anesthetic gas than Takaoka. The performance of both equipments was improved when HME was added. The anesthetic equipment and the addition of HME affect the humidity delivered to the patient that in turn influences in vitro respiratory mucus transportability

ASSUNTO(S)

humidity/adverse effects respiratory mucosa/pathology anestesia geral umidade/efeitos adversos artificial respiration mucociliary clearance inhalation anesthetics respiração artificial equipments and supplies depuração mucociliar anestésicos inalatórios general anesthesia equipamentos e provisões mucosa respiratória/patologia

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