Tracheobronchial consequences of the use of heat and moisture exchangers in dogs.
OBJECTIVE
To determine the effect of heat and moisture exchange (HME) on the tracheobronchial tree (TBT) using a unidirectional anesthesic circuit with or without CO2 absorber and high or low fresh gas flow (FGF), in dogs.


METHODS
Thirty-two dogs were randomly allocated to four groups: G1 (n=8) valvular circuit without CO2 absorber and high FGF (5 L x min(-1)); G2 (n=8) as G1 with HME; G3 (n=8) circuit with CO2 absorber with a low FGF (1 L x min(-1)); G4 (n=8) as G3 with HME. Anesthesia was induced and maintained with pentobarbital. Tympanic temperature (TT), inhaled gas temperature (IGT), relative (RH) and absolute humidity (AH) of inhaled gas were measured at 15 (control), 60, 120 and 180 min of controlled ventilation. Dogs were euthanized and biopsies in the areas of TBT were performed by scanning electron microscopy.


RESULTS
The G2 and G4 groups showed the highest AH (>20 mgH2O x L(-1)) and G1 the lowest (< 10 mgH2O x L(-1)) and G3 was intermediate (< 20 mgH2O x L(-1)) (P < 0.01). There was no difference of TT and IGT among groups. Alterations of the mucociliary system were greatest in G1, least in G2 and G4, and intermediate in G3.


CONCLUSIONS
In dogs, introduction of HME to a unidirectional anesthetic circuit with/without CO2 absorber and high or low FGF preserved humidity of inspired gases. HME attenuated but did not prevent alterations of the mucociliary system of the TBT.
Barra Bisinotto
F M
FM
Department of Anesthesiology, College of Medicine, UNESP, Botucatu, São Paulo, Brazil. flora@mednet.com.br
Braz
J R
JR
Martins
R H
RH
Gregório
E A
EA
Abud
T M
TM
D000758:Anesthesia; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D001980:Bronchi / Q000502:physiology* / Q000648:ultrastructure; D004285:Dogs; D004848:Epithelium / Q000502:physiology / Q000648:ultrastructure; D005260:Female; D006813:Humidity; D008297:Male; D008855:Microscopy, Electron, Scanning; D012121:Respiration, Artificial / Q000009:adverse effects*; D013696:Temperature; D013990:Tidal Volume / Q000502:physiology; D014132:Trachea / Q000502:physiology* / Q000648:ultrastructure