Effect of heat and moisture exchanger (HME) positioning on inspiratory gas humidification

<p>Abstract</p> <p>Background</p> <p>In mechanically ventilated patients, we investigated how positioning the heat and moisture exchanger (HME) at different places on the ventilator circuit affected inspiratory gas humidification.</p> <p>Methods</p> <p>Absolute humidity (AH) and temperature (TEMP) at the proximal end of endotracheal tube (ETT) were measured in ten mechanically ventilated patients. The HME was connected either directly proximal to the ETT (Site 1) or at before the circuit Y-piece (Site 2: distance from proximal end of ETT and Site 2 was about 19 cm) (Figure. <figr fid="F1">1</figr>). Two devices, Hygrobac S (Mallinckrodt Dar, Mirandola, Italy) and Thermovent HEPA (Smiths Medical International Ltd., Kent, UK) were tested. AH and TEMP were measured with a hygrometer (Moiscope, MERA Co., Ltd., Tokyo, Japan).</p> <p>Results</p> <p>Hygrobac S provided significantly higher AH and TEMP at both sites than Thermovent HEPA. Both Hygrobac S and with Thermovent HEPA provided significantly higher AH and TEMP when placed proximally to the ETT.</p> <p>Conclusion</p> <p>Although placement proximal to the ETT improved both AH and TEMP in both HMEs tested, one HME performed better in the distal position than the other HME in the proximal position. We conclude the both the type and placement of HME can make a significant difference in maintaining AH and TEMP during adult ventilation.</p

Trocador de calor e umidade: proteção contra infecções pulmonares? Estudo piloto

O objetivo deste trabalho foi realizar um estudo bacteriológico comparativo entre os sistemas de umidificação aquoso aquecido (UAA) e filtro trocador de calor e umidade (FTCU) quanto à colonização bacteriana e a incidência de infecção respiratória em pacientes submetidos à ventilação mecânica (VM). Trata-se de uma pesquisa prospectiva, controlada e randomizada, na qual 15 pacientes internados na Unidade de Terapia Intensiva (UTI) foram distribuídos em dois grupos. O primeiro fez uso de UAA (n=7) e o outro de FTCU (n=8). Foram coletadas amostras da secreção traqueal, condensado do circuito e FTCU na admissão do paciente, no quarto e oitavo dias, e realizada análise bacteriológica dos mesmos. Quanto às características antropométricas, não observou-se diferenças entre os grupos estudados. A prevalência de pneumonia associada à ventilação (PAV) foi de 57,1% no UAA e 62,5% no FTCU. Ao realizar a análise bacteriológica quantitativa entre eles, não foram observadas variações, sugerindo não haver diferença na prevenção de PAV entre os sistemas de umidificação; porém a presença das mesmas bactérias na secreção traqueal e no condensado e ausência destas na membrana do FTCU podem indicar que a principal fonte de contaminação é o próprio paciente.The aim of this study was to conduct a bacteriological research comparing the aqueous heated humidification systems (HH) and filter heat and moisture exchanger (FHME) and to bacterial colonization and the incidence of respiratory infection in patients undergoing mechanical ventilation. It is a prospective, controlled trial, in that 15 intensive care unit (ICU) patients were divided into two groups. The first made use of HH (n=7) and the other, FHME (n=8). We collected samples of tracheal secretions, and condensate circuit FHME at admission in the fourth and eighth day and bacteriological analysis of the same place. Regarding the anthropometric characteristics, no differences were observed between the groups. The prevalence of ventilator associated pneumonia (VAP) was 57.1% in the HH and 62.5% in FHME. When performing quantitative bacteriological analysis between the group and HH and FHME, differences were not observed, suggesting no variation in the prevention of VAP between the humidification systems, but the presence of these bacteria in the tracheal and condensate and in the absence of these membrane FHME may indicate that the main source of contamination is the patient himself