Effect of hemorrhagic shock on intrapulmonary right-to-left shunt (QS/QT) and dead space (VD/VT)

The effect of hemorrhagic shock on intrapulmonary right-to-left shunt and dead space ratio was investigated in spontaneously breathing dogs under barbiturate anesthesia. Intrapulmonary right-to-left shunt was reduced sufficiently to offset the marked increase in arteriovenous oxygen difference and PaO2 did not fall. Dead space ratio was increased markedly; therefore, in shock, sufficient CO2-elimination depends on severe hyperventilation. According to this empirical findings, a decrease in PaO2 in shock must not be interpreted as a consequence of the shock itself, but it implies an additional pulmonary pathology.