Prediction of post-pneumonectomy respiration

Recent results on oxygen capture during the human respiratory cycle have shown that this capture exhibit a complex dependence on both ventilation VE and cardiac output (Kang, M.-Y. et al. Respir. Physiol. Neurobiol. 2015; 205:109-119). This is shown in the figure 1 which displays the loci of constant VO2 as a function of VE and Q. The predictive method is based on the idea that the resection of a fraction of the lungs volume does not modify strongly Q so that the local blood velocity in the remaining volume is increased accordingly. Consider for example the case where half the lung volume has been resected. As a consequence the local blood velocity is doubled but the local ventilation would keep the same if the diaphragm motion were not modified. This is shown in the figure by shifting from A (for which VE(normal) = 7.5 L/min; Q(normal) = 5L/min and VO2(normal) = 220mL/min) to B (same ventilation, local Q(B) = 2Q(normal) = 10L/min and VO2(post) = (1/2)VO2(B) =(1/2)(0.35) L/min=0.175L/minwhich is insufficient. To recover a normal VO2, one has to increase the ventilation of the remaining section by shifting from B to C where VO2(post) = (1/2)VO2(C) = 220mL/min = VO2(normal). In conclusion, this indicates that, at constant Q, ventilation increase or artificial support is needed to recover normal VO2. The method can be extended to any resection size and to COPD patients that exhibit impaired ventilation before pneumonectomy.