Wave reflections in the pulmonary arteries analysed with the reservoir–wave model

In the pulmonary artery, we use the reservoir–wave model to separate the effects of a charging and discharging, elastic arterial reservoir from the effects of waves created by the contracting and relaxing heart. Wave intensity analysis quantifies the effects of waves that cause changes in pressure and flow and precisely identifies when waves created by the heart and reflections of these waves start and end. We show that negative wave reflections arise from the junction of lobar arteries stemming from the left and right pulmonary arteries. When blood volume is increased and pulmonary arteries become distended, the strength of negative wave reflections increases when 100% O2 is used for ventilation. Negative reflections suck blood downstream and, as they arrive when the heart is developing maximal pressure, negative reflections help to lower the back pressure the heart must pump against and, thus, they tend to increase the forward flow of blood.