Purpose: 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.min(-1)); G2 (n =
8) as G1 with HME; G3 (n = 8) circuit with CO, absorber with a low FGF (I L
.min(-1)); G4 (n = 8) as G3 with HME. Anesthesia was induced and maintained
with pentobarbital. Tympanic temperature (TT), inhaled gas temperature (IG
T), relative (RH) and absolute humidity (AH) of inhaled gas were measured a
t 15 (control), 60, 120 and 180 min of controlled ventilation. Dogs were eu
thanized and biopsies in the areas of TBT were performed by scanning electr
on microscopy.
Results: The G2 and G4 groups showed the highest AH (> 20 mgH(2)O.L-1)and G
I the lowest(< 10 mgH(2)OL(-1)) and G3 was intermediate (< 20 mgH(2)O.L-1)
(P < 0.01). There was no difference of TT and IGT among groups. Alteration
s of the mucociliary system were greatest in G1, least in G2 and G4, and in
termediate in G3.
Conclusion: In dogs, introduction of HME to a unidirectional anesthetic cir
cuit with/without CO2 absorber and high or low FGF preserved humidity of in
spired gases. HME attenuated but did not prevent alterations of the mucocil
iary system of the TBT.