Pulmonary vascular resistance and compliance in pulmonary blood flow alterations in children with congenital heart disease

There is a unique hyperbolic relationship between pulmonary vascular resistance (Rp) and compliance (Cp); however, the characteristics of this coupling curve in pulmonary blood flow alterations remains unknown in children with congenital heart disease. We aimed to explore the Rp-Cp coupling and resistant-compliance (RC) time among them. We retrospectively reviewed catheterization data and calculated Rp and Cp in 217 subjects with ventricular septal defect. Median age and weight at catheterization were 2.8 (1.7-4.4) months and 4.3 (3.7-5.3) kg, respectively. Pulmonary hemodynamic parameters were as follows: mean pulmonary arterial pressure: 36 (28-43) mmHg; the amount of pulmonary blood flow (Qp): 14.2 (11.6-17.6) L/min/m²; Rp: 1.95 (1.38-2.59) Wood unit m²; Cp: 2.98 (2.42-3.88) mmHg/mL/m²; and RC time: 0.35 (0.30-0.40) s. RC time remained unchanged according to alterations in Qp (P = 0.206); however, the relationship between logarithm transformations of Rp and Cp showed more steeper according to an increase in Qp. The pulmonary circulation depends upon Cp rather than Rp according to the degree of Qp despite the constancy in RC time. We should take both Rp and Cp into consideration when evaluating the pulmonary circulation among children with congenital heart disease.

Substrate Effects on the Bandwidth of CdSe Quantum Dot Photodetectors

We investigate the time-resolved photocurrent response of CdSe quantum dot (QD) thin films sensitized with zinc β-tetraaminophthalocyanine (Zn4APc) (Kumar , ACS Appl. Mater. Interfaces, 2019, 11, 48271-48280) on three different substrates, namely, silicon with 230 nm SiO₂ dielectric, glass, and polyimide. While Si/SiO₂ (230 nm) is not suitable for any transient photocurrent characterization due to an interfering photocurrent response of the buried silicon, we find that polyimide substrates invoke the larger optical bandwidth with 85 kHz vs 67 kHz for the same quantum dot thin film on glass. Upon evaluation of the transient photocurrent, we find that the photoresponse of the CdSe quantum dot films can be described as a combination of carrier recombination and fast trapping within 2.7 ns followed by slower multiple trapping events. The latter are less pronounced on polyimide, which leads to the higher bandwidth. We show that all devices are resistance-capacitance (RC)-time limited and that improvements of photoresistance are the key to further increasing the bandwidth.

The resistance-compliance product of the pulmonary circulation varies in health and pulmonary vascular disease

Pulmonary vascular resistance (PVR) is traditionally used to describe pulmonary hemodynamic characteristics. However, it does not take into account pulmonary artery compliance (Ca) or pulsatile flow. The product of PVR and Ca is known as RC time. Previous studies assert that the PVR-Ca relationship is fixed and RC time is constant between health and disease states. We hypothesized that RC time was not constant in health and pulmonary vascular disease. Right heart catheterizations performed in Papworth Hospital over a 6 year period were analyzed. Subjects were divided into those with normal pulmonary hemodynamics (NPH group; n = 156) and pulmonary arterial hypertension (PAH group; n = 717). RC time and the right ventricle (RV) oscillatory power fraction were calculated. RC time for the NPH group (0.47 ± 0.13 sec) is significantly lower than the PAH group (0.56 ± 0.16 sec; P < 0.0001). The RV oscillatory power fraction is lower in the NPH group (P < 0.0001). RC time correlates inversely with the RV oscillatory power fraction in each group. We conclude, there is an inverse relationship between PVR and Ca, however, this relationship is not always fixed. Consequently, RC time is significantly lower in health compared to disease with elevated pulmonary artery pressures. PAH leads to a decrease in cardiac efficiency.