Pulmonary arterial resistance and compliance in preterm infants

Effect of delayed cord clamping on maternal and neonatal outcome in twin pregnancies: a retrospective cohort study

The objective of this study was to compare the maternal and neonatal outcomes following delayed cord clamping (DCC) versus immediate cord clamping (ICC) in twin pregnancies. This was a retrospective cohort study of 705 twin pregnancies who delivered at ≥ 24 weeks of gestation. Maternal and neonatal hemoglobin levels, blood transfusion, and neonatal outcomes were compared between DCC (n = 225) and ICC (n = 480) groups. Mean maternal predelivery and postpartum hemoglobin levels and the rate of postpartum hemoglobin drop ≥ 20% or maternal blood transfusion were comparable between the two groups. The DCC group had a significantly higher mean neonatal hemoglobin level (DCC vs. ICC: 17.4 ± 3.5 vs. 16.6 ± 2.7 g/dl, P = 0.010) but significantly lower rates of neonatal blood transfusion (DCC vs. ICC: 3.3% vs. 8.8%, P < 0.001) and respiratory distress syndrome (DCC vs. ICC: 6.7% vs. 15.2%, P < 0.001) than the ICC group. In conclusion, DCC compared with ICC in twin pregnancy was not associated with an increase of maternal postpartum bleeding complications, but it was associated with higher neonatal hemoglobin level and lower risks of neonatal blood transfusion and respiratory distress syndrome.

Humidity during high-frequency oscillatory ventilation compared to intermittent positive pressure ventilation in extremely preterm neonates: An in vitro and in vivo observational study

BACKGROUND

Inappropriate humidification of inspired gas during mechanical ventilation can impair lung development in extremely low birthweight (ELBW) infants. Humidification depends on multiple factors, such as the heater-humidifier device used, type of ventilation, and environmental factors. Few studies have examined inspired gas humidification in these infants, especially during high-frequency oscillatory ventilation (HFOV). Our objective was to compare humidity during HFOV and intermittent positive pressure ventilation (IPPV), in vitro and in vivo.

METHODS

In vitro and in vivo studies used the same ventilator during both HFOV and IPPV. The bench study used a neonatal test lung and two heater-humidifiers with their specific circuits; the in vivo study prospectively included preterm infants born before 28 weeks of gestation.

RESULTS

On bench testing, mean absolute (AH) and relative (RH) humidity values were significantly lower during HFOV than IPPV (RH = 79.4 ± 8.1% vs. 89.0 ± 6.2%, p < 0.001). Regardless of the ventilatory mode, mean RH significantly differed between the two heater-humidifiers (89.6 ± 6.7% vs 78.7 ± 6.8%, p = 0.003). The in vivo study included 10 neonates (mean ± SD gestational age: 25.7 ± 0.9 weeks and birthweight: 624.4 ± 96.1 g). Mean RH during HFOV was significantly lower than during IPPV (74.6 ± 5.7% vs. 83.0 ± 6.7%, p = 0.004).

CONCLUSION

RH was significantly lower during HFOV than IPPV, both in vitro and in vivo. The type of heater-humidifier also influenced humidification. More systematic measurements of humidity of inspired gas, especially during HFOV, should be considered to optimize humidification and consequently lung protection in ELBW infants.

Comprehensive assessments of pulmonary circulation in children with pulmonary hypertension associated with congenital heart disease

Pulmonary hypertension associated with congenital heart disease (CHD-PH) encompasses different conditions confounded by the left-to-right shunt, left heart obstruction, ventricular dysfunction, hypoxia due to airway obstruction, dysplasia/hypoplasia of the pulmonary vasculature, pulmonary vascular obstructive disease, and genetic variations of vasoactive mediators. Pulmonary input impedance consists of the pulmonary vascular resistance (Rp) and capacitance (Cp). Rp is calculated as the transpulmonary pressure divided by the pulmonary cardiac output, whereas Cp is calculated as the pulmonary stroke volume divided by the pulmonary arterial pulse pressure. The plots of Rp and Cp demonstrate a unique hyperbolic relationship, namely, the resistor-capacitor coupling curve, which represents the pulmonary vascular condition. The product of Rp and Cp is the exponential pressure decay, which refers to the time constant. Alterations in Cp are more considerable in CHD patients at an early stage of developing pulmonary hypertension or with excessive pulmonary blood flow due to a left-to-right shunt. The importance of Cp has gained attention because recent reports have shown that low Cp potentially reflects poor prognosis in patients with CHD-PH and idiopathic pulmonary hypertension. It is also known that Cp levels decrease in specific populations, such as preterm infants and trisomy 21. Therefore, both Rp and Cp should be individually evaluated in the management of children with CHD-PH who have different disease conditions.

Right Ventricular Function and Its Coupling With Pulmonary Circulation in Precapillary Pulmonary Hypertension: A Three-Dimensional Echocardiographic Study

Objective: To assess right ventricular (RV) function and RV-pulmonary arterial (PA) coupling by three-dimensions echocardiography and investigate the ability of RV-PA coupling to predict adverse clinical outcomes in patients with precapillary pulmonary hypertension (PH). Methods: We retrospectively collected a longitudinal cohort of 203 consecutive precapillary PH patients. RV volume, RV ejection fraction (RVEF), and RV longitudinal strain (RVLS) were quantitatively determined offline by 3D echocardiography. RV-PA coupling parameters including the RVEF/PA systolic pressure (PASP) ratio, pulmonary arterial compliance (PAC), and total pulmonary resistance (TPR) were recorded. Results: Over a median follow-up period of 20.9 months (interquartile range, 0.1-67.4 months), 87 (42.9%) of 203 patients experienced adverse clinical outcomes. With increasing World Health Organization functional class (WHO-FC), significant trends were observed in increasing RV volume, decreasing RVEF, and worsening RVLS. RV arterial coupling (RVAC) and PAC were lower and TPR was higher for WHO-FC III+IV than WHO-FC I or II. The RVEF/PASP ratio showed a significant correlation with RVLS. RVAC had a stronger correlation with the RVEF/PASP ratio than other indices. Multivariate Cox proportional-hazard analysis identified a lower 3D RVEF and worse RVLS as strong predictors of adverse clinical events. RVAC, TPR, and PAC had varying degrees of predictive value, with optimal cutoff values of 0.74, 11.64, and 1.18, respectively. Conclusions: Precapillary-PH with RV-PA uncoupling as expressed by a RVEF/PASP ratio <0.44 was associated with adverse clinical outcomes. PAC decreased and TPR increased with increasing WHO-FC, with TPR showing better independent predictive value.

Characteristics of the pulmonary circulation in infants with complete atrioventricular septal defect

OBJECTIVE

Infants with complete atrioventricular septal defect occasionally accompany pulmonary hypertension; however, the pulmonary circulation can be altered by pulmonary vascular conditions as well as the left heart lesions. This study aimed to explore whether the left heart lesions were related to the pulmonary circulation among them.

METHODS

We performed echocardiography and cardiac catheterisation in 42 infants with complete atrioventricular septal defect and studied relationships between the pulmonary haemodynamic parameters and the left heart morphology.

RESULTS

Age and weight at preoperative evaluation were 65 days (47-114) (the median following interquartile range) and 5.5 kg (4.0-7.1), respectively. There were 27 individuals with Down syndrome. Gestational age was 38 weeks (37-39). Catheterisation showed mean pulmonary arterial pressure: 36 (29-46) mmHg, the ratio of pulmonary to systemic blood flow: 3.45 (2.79-4.98), pulmonary vascular resistance: 2.20 Wood units·m2 (1.53-3.65), and pulmonary arterial compliance: 2.78 (1.86-4.10) ml/Hg/m2. Echocardiography showed the Rastelli classification type A in 28 and type C in 14, moderate or severe left atrioventricular valve regurgitation in 19 patients (45%), atrioventricular valve index of 0.67 (0.56-0.79), left ventricular end-diastolic volume z score of 4.46 (1.96-7.78), and aortic valve diameter z score of -0.70 (-1.91 to 0.20). Multivariable regression analysis revealed that preoperative pulmonary vascular resistance was significantly correlated to gestational age (p = 0.002), and that preoperative pulmonary arterial compliance was significantly correlated to gestational age (p = 0.009) and Down syndrome (p = 0.036).

CONCLUSIONS

The pulmonary circulation does not depend upon the presence of left heart lesions but gestational age and Down syndrome in infants with complete atrioventricular septal defect.

Respiratory Severity Score with Regard to Birthweight during the Early Days of Life for Predicting Pulmonary Hypertension in Preterm Infants

OBJECTIVE

The respiratory severity score (RSS) has been demonstrated to be associated with the oxygenation index in intubated newborn infants. We aimed to evaluate the usefulness of RSS with regard to birthweight (BW) in preterm infants for predicting an association with future pulmonary hypertension (PH).

METHODS

Preterm infants with <30 weeks' gestation and <1250 g BW were reviewed and grouped into two (PH vs. no PH). Basic perinatal characteristics, comorbidities and parameters reflecting lung condition, including duration of invasive mechanical ventilator care, were compared. Respiratory support parameters (FiO2, RSS and RSS/kg) during the first 5 days of birth (0-120 h) were compared between the groups, and receiver operating characteristics curves were produced to evaluate the association with PH.

RESULTS

RSS/kg, of the three respiratory support parameters, demonstrated significantly higher values in the PH group in the early days of life. Particularly, RSS/kg at day 2 of life had the greatest area under the curve [0.762, 95% confidence interval (CI) 0.655-0.869, p < 0.001] and maintained statistical significance [odds ratio (OR) 1.352, 95% CI 1.055-1.732, p = 0.017] in the multivariable analysis for a potential association with PH, along with gestational age (OR 0.996, 95% CI 0.993-0.999, p = 0.015) and preterm premature rupture of membrane >18 h (OR 4.907, 95% CI 1.436-16.765, p = 0.011).

CONCLUSION

RSS/kg is a potential marker associated with the development of PH. Future studies could verify its usefulness as a reliable surrogate for predicting respiratory morbidity in clinical settings.

Decreased Pulmonary Arterial Compliance is a Predictor for Poor Outcomes in Infants with Isolated Atrial Septal Defect and Pulmonary Hypertension

This study aimed to investigate risk factors for poor outcomes in infants with isolated atrial septal defect (ASD) and pulmonary hypertension who had unexpectedly fatal course. We retrospectively reviewed 22 infants with isolated ASD and pulmonary hypertension, and analyzed the relationship between clinical outcomes and pulmonary hemodynamic parameters including pulmonary arterial resistance (Rp) and compliance (Cp) based on cardiac catheterization among them. Age and weight at cardiac catheterization were 5 (1-11) months and 4.9 (3.1-9.2) kg, respectively. There were 17 individuals with Down syndrome. Pulmonary hemodynamic parameters were shown as follows: the ratio of pulmonary to systemic blood flow: 2.0 (0.6-3.8), mean pulmonary arterial pressure: 41 (20-60) mmHg, the ratio of pulmonary to systemic mean pressure (Pp/Ps): 0.67 (0.46-1.13), Rp: 4.11 (0.68-15.80) Wood units m², and Cp: 1.80 (0.63-6.16) mL/mmHg m². There were 4 deaths during the follow-up period of 40 (7-241) months. Univariable logistic regression analysis revealed that Pp/Ps (odds ratio [OR]: 18,500, 95% confidential interval [CI] 1.48-230,659,690, P = 0.041) and Cp (OR: 0.03, 95% CI 0.001-0.73, P = 0.031) were significantly related to death. A Pp/Ps cutoff value more than 0.94 and a Cp cutoff value less than 0.97 mL/mmHg m² yielded as the predictors of death with sensitivity of 98% and 94%, specificity of 75% and 75%, respectively. Decreased Cp is a previously unrecognized predictor for poor outcome in infants with isolated ASD and pulmonary hypertension.

Impact of Gestational Age on Surgical Outcomes in Patients With Functionally Single Ventricle

BACKGROUND

Younger gestational age (GA) is known to be associated with worse outcomes after congenital cardiac surgery. We sought to determine the impact of GA on surgical outcomes of single-ventricle palliation.

METHODS

Among the 284 patients with functionally single ventricle who were born between January 2005 and December 2014, 50 neonates were born prematurely (GA < 37 weeks) and 113 neonates in the early term period (37 weeks ≤ GA < 39 weeks). Initial palliation was required in 251 patients, whereas 33 patients received primary bidirectional cavopulmonary anastomosis (BCPA).

RESULTS

BCPA and the completion Fontan operation were performed in 200 and 169 patients, respectively. Overall survival at 5 years were 62.5% ± 2.9%. On Cox regression younger GA (hazard ratio, 1.14 per 1-week decrease; P = .007) was identified as a risk factor for increased interstage mortality (ISM) between initial palliation and BCPA. On subgroup analysis of the preterm or early-term patients with initial palliation (n = 145), younger postmenstrual age at initial palliation was associated with increased ISM before BCPA (hazard ratio, 1.18; P = .005). After BCPA, however, younger GA did not increase the risk of ISM between BCPA and the Fontan operation (P = .47).

CONCLUSIONS

Younger GA is a risk factor for ISM between initial palliation and BCPA. Deferral of initial palliation may be beneficial to decrease the risk of ISM in patients who were born at preterm or early term. Adverse effects of younger GA on survival disappeared once BCPA was performed.

Relationship Between Pulmonary Arterial Resistance and Compliance in Patients with Down Syndrome

This study aimed to clarify the characteristics of pulmonary arterial resistance (Rp)-compliance (Cp) coupling in individuals with Down syndrome (DS), who have increased risks of pulmonary arterial hypertension (PAH). We performed cardiac catheterization before and after corrective surgery in 85 DS infants and 85 controls with congenital heart disease and PAH. We retrospectively collected hemodynamic data and compared Rp and Cp between the groups. Age at surgery was 3.5 (2.6-4.6) months. The first and second catheterizations were performed 1 month before and after corrective surgery in both groups. Preoperative Cp in DS patients was significantly lower than that in controls [2.27 (1.62-3.0) vs. 2.50 (1.86-3.31) mL/mmHg/m², p = 0.039], although there was no significant difference in mean pulmonary arterial pressure and Rp between the groups. Analysis of covariance revealed that the slopes of the preoperative regression lines for the logarithmic transformations of Rp and Cp were identical in DS patients and controls (p = 0.299). However, the postoperative regression line was shifted downward in DS patients after corrective surgery. Postoperative home oxygen therapy (HOT) was performed in 39 patients (36 DS patients) and multivariate logistic regression analysis revealed that postoperative HOT was significantly related to low preoperative Cp (p = 0.039) and DS (p = 0.0001). Individuals with DS have the unique pulmonary vasculature characterized with low Cp that is related to postoperative HOT.