Pulmonary O₂ transfer during pulsatile and non‐pulsatile perfusion

Abstract

The importance of the perfusion pattern for the oxygen transfer has been examined in isolated rabbit lungs perfused with plasma at constant volume inflow. The lungs were ventilated with constant tidal volume and constant end-expiratory pressure. Following a standardized rise in FIO2 the rate of rise in pulmonary venous PO2 (delta PO2/delta t) was measured during alternately pulsatile and non-pulsatile perfusion in normal lungs and in lungs made edematous by elevation of left atrial pressure. In normal lungs there was no difference in delta PO2/delta t when the two modes of perfusion were compared. In edematous lungs delta PO/delta t was statistically higher during pulsatile perfusion, indicating a beneficial effect of flow- and pressure pulsations, e.g. a better distribution of V/Q ratios throughout the lungs. In a separate series of expts. the advancement of a high O2 front through the airways was measured, and the two perfusion patterns compared. Since no difference was found, we suggest that the phenomenon of "cardiogenic gas mixing" in the airways in vivo is a result of a direct action of the heart on the lungs rather than arterial pulsations.

Pulmonary capillaries are recruited during pulsatile flow

“…In addition to a more homogeneous transit time distribu-tion, capillary recruitment adds directly to gas exchange surface area. Although we did not measure the response time of blood gas changes after a change in inspired gas concentrations, Hauge and Nicolaysen (7) showed that the rate of rise of PO 2 in pulmonary venous blood after an increase in the inspired oxygen concentration was greater during pulsatile flow than during steady flow. On the basis of these studies and our direct measurements of transit time and capillary recruitment, we conclude that gas exchange is more efficient during pulsatile flow.…”

“…WHEN PULMONARY BLOOD FLOW is pulsatile, vascular resistance falls (9,16) and gas exchange improves (7). Both of these observations could be explained if pulsatile flow caused capillary recruitment, for recruitment of capillaries would increase the cross-sectional area of the microvascular bed and the surface area available for gas exchange.…”

Pulmonary function assessment post‐left ventricular assist device implantation

“…Lastly, although the CF pumps provide better durability over the pumps providing pulsatile flow, 3 pulsatile flow has been shown to be beneficial for pulmonary capillary recruitment and the rate of oxygen uptake. 38,39 New-generation pumps implementing artificial pulsatility will be of interest for future research of lung diffusion in the LVAD population. 40 Prospective studies using appropriate techniques (rebreath D LCO assessment) are needed to evaluate the dynamic of changes in membrane conductance and Vc postimplantation.…”

Right Ventricular Failure After Left Ventricular Assist Device Implantation: The Need for an Implantable Right Ventricular Assist Device

“…Some authors reported beneficial effects of pulsatile flow for the pulmonary circulation and respiratory function (61–65), while other authors could not confirm these results (60,66,67). Furthermore, in patients, abnormal distribution of pulmonary blood flow has been observed after the Glenn or Fontan operations (68–70).…”