Mr. Mazan et al., Comparison of forced oscillation with the conventional method for histamine bronchoprovocation testing in horses, AM J VET RE, 60(2), 1999, pp. 174-180
Objective-To compare response of horses to histamine bronchoprovocation (HB
P), using total respiratory resistance (R-rs) measured by forced oscillator
y mechanics (FOM) with dynamic compliance (C-dyn) and pulmonary resistance
(R-L) measured by the esophageal balloon method.
Animals-10 horses with various degrees of airway reactivity.
Procedure-The 2 methods for measuring airway responses to HBP were performe
d on separate days. Endpoints compared were increase of 150 or 200% of base
line R-rs (PC150Rrs, PC200Rrs) and to 150% of baseline R-L (PC150RL) or dec
rease to 65% of baseline C-dyn (PC65Cdyn). Frequency dependence of respirat
ory mechanics, using FOM, was evaluated, using the slope of R-rs over 1 to
3 Hz and the ratios of R-rs at 1 Hz to R-rs at 2 and 3 Hz (R-rs1Hz/R-rs2Hz,
R-rs1Hz/R-rs3Hz) and of R-rs at 2 Hz to R-rs at 3 Hz (R-rs2Hz/R-rs3Hz) Eff
ect of histamine on frequency dependence was assessed.
Results-Correlation with PC65Cdyn was high for PC150Rrs (r(s) = 0.93) and P
C200Rrs (r(s) = 0.96). Correlation between PC65Cdyn and PC150RL was weakly
positive (r(s) = 0.61). The slope of R-rs over 1 to 3 Hz changed significan
tly between baseline (-0.07 +/- 0.09 cm H2O/L/s/Hz) and final histamine dos
e (-0.28 +/- 0.10 cm H2O/L/s/Hz). The R-rs1Hz/R-rs3Hz and R-rs2Hz/R-rs3Hz d
iffered significantly (P < 0.05 between baseline [1.27 +/- 0.36 and 0.96 +/
- 0.11, respectively] and final histamine dose [1.62 +/- 0.37 and 1.09 +/-
0.14, respectively]).
Conclusions-Correlation between histamine-induced changes in respiratory me
chanics, as measured by FOM and the pneumotachographesophageal balloon meth
od, was good. The FOM results indicated frequency dependence of respiratory
mechanics during HBP.
Clinical Relevance-A noninvasive method of measuring airway reactivity will
facilitate routine evaluation of horses with suspected small airway diseas
e and may be suitable for field studies.