Gas exchange and haemodynamics during high frequency body surface oscillation in rabbits

To establish the clinical feasibility of high frequency body surface oscillation (HFBSO) as a mode of controlled ventilation for infants and to examine its effects on basic haemodynamic parameters, we studied twelve intact rabbits in two groups. The animals were placed in a body chamber with their heads remaining outside through a neck-hole. The mean chamber pressure was maintained at -3 to -4 cmH2O and a piston pump, operating at 3, 6, 9, 12 and 15 Hz, created pressure swings in the chamber, thus generating oscillatory tidal volumes. A fresh-airflow of 2 1.min-1 was used over the mouth. In the first group of six rabbits, we obtained the relationship between tidal volume (VT) and frequency (f) which maintained a normocapnic state (PaCO2 = 40 +/- 2 mmHg) when the animals were paralysed. The average tidal volumes required were between 1.36 and 1.78 ml.kg-1 for the 3-15 Hz frequency range, or about 1/4 of the spontaneous tidal volume. The corresponding mean PaO2 was 66.7 mmHg at 3 Hz and 73.4 mmHg at 9 Hz. These results indicate that adequate ventilation and acceptable gas exchange took place in these experimental animals during HFBSO. In the second group, six rabbits were catheterized with catheter-tip pressure transducers in order to obtain the aortic (ABP), central venous (CVP) and intrathoracic pressures. The arterial pressure profile was severely deranged by HFBSO, but, electronic subtraction of the intrathoracic pressure swings from the ABP signal resulted in the return of the normal pressure profile.(ABSTRACT TRUNCATED AT 250 WORDS)