Abstract
Since little is known about the effect of decreased haematocrit (Hct) on lung function, we assessed the acute effects of haemodilution during stable haemodynamic condition on respiratory mechanical parameters and lung volume changes on anaesthetized intubated minipigs (n=8).
After control condition, stepwise 10 ml/kg blood withdrawals were compensated with 30 ml/kg of crystalloid to maintain stable haemodynamics. Forced oscillation technique was used to measure airway resistance (Raw), respiratory tissue damping (G) and elastance (H). Effective lung volume (ELV) was measured from the CO2 elimination traces. Extravascular lung water (EVLW) was determined by thermodilution. Respiratory and haemodynamic measurements were made before and following each step of haemodilution.
Haemodilution led to an increase in Raw (up to 20%) and decrease in G (up to – 40%), with significant correlations with Hct levels (R=-0.67 and 0.67 for Raw and G respectively, p< 0.0001). ELV decreased in parallel with a slight but significant increase in H (r=0.66, p< 0.0001) and EVLW.
Our data suggest that haemodilution affects the lung function and these changes correlate with the Hct values. The increase in EVLW indicates that this regimen leads to overcompensation, which may explain the increases in Raw and the loss of ELV. The decreases in G with Hct may be due to the altered blood rheology affecting the lung tissue viscoelasticity.
- Copyright ©ERS 2015