The humidity in a low-flow Drager Fabius anesthesia workstation with or without thermal insulation or a heat and moisture exchanger: a prospective randomized clinical trial

• Grant number: 17/00477-2
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: April 01, 2017
• End date: June 30, 2017
• Field of knowledge: Health Sciences - Medicine - Surgery
• Principal Investigator: Jose Reinaldo Cerqueira Braz
• Grantee: Jose Reinaldo Cerqueira Braz
• Host Institution: Faculdade de Medicina (FMB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Tracheal intubation limits the normal warming and humidifying functionsof a patient's upper airways. An inhaled gas minimum moisture target of 20 mgH2O.L-1is recommended to reduce the deleterious effects of dry gas on the airways. The Fabius GS Premium anesthesia workstation (Dräger Medical, Lübeck, Germany) has a built-in hotplate to heat gases in the breathing circuit. The use of a low fresh gas flow (FGF) in the breathing circuit increases the temperature and humidity of the inhaled gas and a heat and moisture exchanger (HME) can be used to further heat and humidify the inhaled gas. The corrugated tubes of the breathing circuit are composed of materials with low thermal insulation (TI), and the temperature and humidity of the gases in the circuit are influenced by the cold operating room temperature. The aim of this study was to compare the temperature and humidity of the inhaled gases from a low-flow Fabius anesthesia workstation with or without TI of the breathing circuit and with or without an HME. Forty-one adult female patients were randomly allocated into four groups according to the devices coupled to the breathing circuit from a Dräger Fabius GS Premium anesthesia workstation, used to ventilate their lungs using a breathing circle system with a low FGF (1 L.min-1): control (n = 11), with TI (n = 10), with an HME (n = 10) or with TI and an HME (TIHME) (n = 10). The temperature and humidity of the inhaled gases were measured close to the tracheal tube using a thermo-hygrometer. Measurements were obtained at 10, 30, 60, 90 and 120 minutes after connecting the patients to the breathing circuit. The mean inhaled gas temperature was higher in the HME and TIHME groups (29.2 ± 1.3°C and 30.1 ± 1.2°C, respectively) compared with the control and TI groups (27.5 ± 1.0°C and 27.2 ± 1.1°C, respectively; P = 0.003). The mean inhaled gas absolute humidity was higher in the HME and TIHME groups (28.1 ± 2.3 mgH2O.L-1 and 29.4 ± 2.0 mgH2O.L-1, respectively) compared with the control and TI groups (25.0 ± 1.8 mgH2O.L-1 and 24.9 ± 1.8mgH2O.L-1, respectively; P < 0.001). The low FGF Fabius GS Premium breathing circuit provides the minimum humidity level of inhaled gases to avoid damage to the tracheobronchial epithelia. TI of the breathing circuit does not increase the temperature or humidity of the inhaled gases, whereas inserting an HME increases both the heat and moisture of the inhaled gases closer to physiological values. (AU)