Effect of perivascular electromagnetic flow probes on pulmonary hemodynamics

We determined the effect of perivascular electromagnetic flow probes (EMF) on pulmonary hemodynamics in acute experiments. In seven dogs placement of the EMF on the main pulmonary artery (MPA) increased pulmonary arterial pulse pressure by 25% (17.8-21.9 cmH₂O, P<0.005) and mean right ventricular pressure by 12% (23.2-25.9 cmH₂O, P<0.001) but did not alter heart rate, systemic blood pressure, mean pulmonary arterial pressure, or right ventricular end-diastolic pressure. This respone was not abolished by local application of lidocaine to the MPA. In three cats input impedance was calculated from measurements of pressure and flow in the MPA. Impedance was calculated with flow measured using an EMF and ultrasonic volume flow probe (USF), which avoids the constraining effect of the EMF. When flow was measured with an EMF rather than a USF, there was a significant difference in the impedance spectra (P<0.001), but it was only apparent in the moduli greater than six harmonics. We conclude that the EMF does affect right ventricular afterload in acute experiments and alters the measured input impedance.