Pulmonary transit time has close relation with pulmonary pulse wave transit time in normal subjects.

Background: Pulmonary transit time (PTT) and pulmonary pulse wave transit time (pPTT) are useful parameters for the evaluation of cardiopulmonary circulation and vascular alterations, but their relationship remains unknown. The aim of this study was to investigate the correlation between PTT and pPTT.

Methods: A total of 60 healthy volunteers were involved in this study. They were divided into two groups (30 participants per group): <50 years and >50 years. They all underwent Doppler echocardiography of pulmonary vein flow and contrast echocardiography with the measurement of pPTT and PTT, respectively. The correlation between PTT and pPTT was deduced.

Results: Compared with Group of <50 years, there was a significant increment in left atrial volume index, left atrial pressure and pulmonary artery stiffness but a significant reduction in acceleration times of pulmonary artery flow in Group of >50 years (p < 0.05). Group >50 years had longer PTT and but reduced normalized PTT by R-R interval (NPTT), reduced normalized pPTT by R-R interval (NpPTT) than Group <50 years (p < 0.05), while there was no significant difference in pPTT between the two groups (p > 0.05). PTT and NPTT were all negatively correlated with pPTT and NpPTT. The statistically significant strongest correlation was observed between PTT and NpPTT (r = -0.886, p < 0.0001). The regression equation for them was y = 7.4396-13.095x (R  = 0.785; p < 0.001), where x and y represent NpPTT and PTT, respectively.

Conclusion: PTT had close relation with pPTT in normal subjects. From the regression equation for them, we can get the value of PTT simply and easily by non-invasively measured pPTT.