Wkr. Barnikol et al., A RESPIRATORY MICROVALVE FOR SPONTANEOUSL Y BREATHING ANESTHETIZED SMALL ANIMALS, Biomedizinische Technik, 39(3), 1994, pp. 57-62
For the accurate functional analysis of the gas exchange in the lungs
or evaluation of artificial oxygen carriers in spontaneously breathing
anaesthetized small animals, we developed a new respiratory micro-val
ve. The body of the valve is made of aluminium, and the flaps are made
of silicone rubber. The maximum flow rate in a rat measured with a pn
eumotachograph and the microvalve was an average of 19.9 ml/s during i
nspiration, and 17.8 ml/s during expiration. The pressure measured in
the tracheal tube was -0.85 during inspiration, and +0.39 cm H2O durin
g expiration; the end-expiratory pressure in the tube was zero. In two
experiments with anaesthetised rats lasting 4-5 hours, ventilation, o
xygen uptake, carbon dioxide release and the respiratory exchange rati
o were 638 ml/min/kg, 21.7 ml O2(STPD)/min/kg, 16.6 ml CO2(STPD)/min/k
g, and 0.77, respectively. There was no significant change in any para
meter during the experiment. The microvalve increases the dead space b
y approximately 35%, but this is well tolerated by the rats, which com
pensate by increasing their tidal volume by about 10 to 15%. The major
advantage of using the micro-valve in comparison with other methods i
s the fact that the true difference between inspiratory and mean mixed
expiratory gas can be measured with great accuracy. The micro-valve c
an readily be adjusted for optimal use with a range of animals.