Effects of nasal continuous airway pressure on pulmonary and systemic output in preterm infants

Objective: Respiratory assistance with nasal continuous positive airway pressure (n-CPAP) is an effective treatment in premature newborns presenting respiratory distress. The aim of the study was to depict cardiac function, systemic (Qs) and pulmonary output (Qp) by echocardiography in stable premature infants requiring prolonged n-CPAP. Our hypothesis was that n-CPAP could reduce pulmonary blood flow. Patients and methods: All premature infants < 32 weeks gestation, > 7 days-old, requiring n-CPAP without severe respiratory compromise nor need for additional oxygen were prospectively included. Every patient had a first echocardiography while on n-CPAP. N-CPAP was then discontinued for two hours and a second echocardiography was performed. Results: 17 premature infants were included. Mean gestational age was 28 ± 2 weeks and mean weight 1.1 ± 0.3 kg. Following retrieval of n-CPAP we observed an increase in Qp of 53 ml/kg/min (95% CI 19-87 ml/kg/min), but no significant change in Qs. Consecutively a significant increase in Qp/Qs ratio of 16% was found (95% CI 7-29%). Conclusions: Nasal continuous positive airway pressure has hemodynamic effects in preterm infants in stable pulmonary and cardiac conditions. It reduces pulmonary output without interference with systemic output.

Altered high-energy phosphate metabolism predicts contractile dysfunction and subsequent ventricular remodeling in pressure-overload hypertrophy mice.

To study the role of early energetic abnormalities in the subsequent development of heart failure, we performed serial in vivo combined magnetic resonance imaging (MRI) and (31)P magnetic resonance spectroscopy (MRS) studies in mice that underwent pressure-overload following transverse aorta constriction (TAC). After 3 wk of TAC, a significant increase in left ventricular (LV) mass (74 +/- 4 vs. 140 +/- 26 mg, control vs. TAC, respectively; P < 0.000005), size [end-diastolic volume (EDV): 48 +/- 3 vs. 61 +/- 8 microl; P < 0.005], and contractile dysfunction [ejection fraction (EF): 62 +/- 4 vs. 38 +/- 10%; P < 0.000005] was observed, as well as depressed cardiac energetics (PCr/ATP: 2.0 +/- 0.1 vs. 1.3 +/- 0.4, P < 0.0005) measured by combined MRI/MRS. After an additional 3 wk, LV mass (140 +/- 26 vs. 167 +/- 36 mg; P < 0.01) and cavity size (EDV: 61 +/- 8 vs. 76 +/- 8 microl; P < 0.001) increased further, but there was no additional decline in PCr/ATP or EF. Cardiac PCr/ATP correlated inversely with end-systolic volume and directly with EF at 6 wk but not at 3 wk, suggesting a role of sustained energetic abnormalities in evolving chamber dysfunction and remodeling. Indeed, reduced cardiac PCr/ATP observed at 3 wk strongly correlated with changes in EDV that developed over the ensuing 3 wk. These data suggest that abnormal energetics due to pressure overload predict subsequent LV remodeling and dysfunction.

Development of fluid conduits in the auriferous shear zones of the Hutti Gold Mine, India: evidence for spatially and temporally heterogeneous fluid flow

The gold mineralization of the Hutti Mine is hosted by nine parallel, N - S trending, steeply dipping, 2 - 10 m wide shear zones, that transect Archaean amphibolites. The shear zones were formed after peak metamorphism during retrograde ductile D, shearing in the lower amphibolite facies. They were reactivated in the lower to mid greenschist facies by brittle-ductile D-3 shearing and intense quartz veining. The development of a S-2-S-3 crenulation cleavage facilitates the discrimination between the two deformation events and contemporaneous alteration and gold mineralization. Ductile D, shearing is associated with a pervasively developed distal chlorite - sed cite alteration assemblage in the outer parts of the shear zones and the proximal biotite-plagioclase alteration in the center of the shear zones. D3 is characterized by development of the inner chlorite-K-feldspar alteration, which forms a centimeter-scale alteration halo surrounding the laminated quartz veins and replaces earlier biotite along S-3. The average size of the laminated vein systems is 30-50 m along strike as well as down-dip and 2-6 m in width. Mass balance calculations suggest strong metasomatic changes for the proximal biotite-plagioclase alteration yielding mass and volume increase of ca. 16% and 12%, respectively. The calculated mass and volume changes of the distal chlorite-sericite alteration (ca. 11%, ca. 8%) are lower. The decrease in 6180 values of the whole rock from around 7.5 parts per thousand for the host rocks to 6-7 parts per thousand for the distal chlorite-sericite and the proximal biotite-plagioclase alteration and around 5 parts per thousand for the inner chlorite-K-feldspar alteration suggests hydrothermal alteration during two-stage deformation and fluid flow. The ductile D-2 deformation in the lower amphibolite facies has provided grain scale porosities by microfracturing. The pervasive, steady-state fluid flow resulted in a disseminated style of gold-sulfide mineralization and a penetrative alteration of the host rocks. Alternating ductile and brittle D3 deformation during lower to mid greenschist facies conditions followed the fault-valve process. Ductile creep in the shear zones resulted in a low permeability environment leading to fluid pressure build-up. Strongly episodic fluid advection and mass transfer was controlled by repeated seismic fracturing during the formation of laminated quartz(-gold) veins. The limitation of quartz veins to the extent of earlier shear zones indicate the importance of preexisting anisotropies for fault-valve action and economic gold mineralization. (C) 2003 Elsevier B.V. All rights reserved.

A prospective observational study comparing a non-operator dependent automatic PWV analyser to pulse pressure, in assessing arterial stiffness in hemodialysis.

BACKGROUND: Chronic kidney disease (CKD) accelerates vascular stiffening related to age. Arterial stiffness may be evaluated measuring the carotid-femoral pulse wave velocity (PWV) or more simply, as recommended by KDOQI, monitoring pulse pressure (PP). Both correlate to survival and incidence of cardiovascular disease. PWV can also be estimated on the brachial artery using a Mobil-O-Graph; a non-operator dependent automatic device. The aim was to analyse whether, in a dialysis population, PWV obtained by Mobil-O-Graph (MogPWV) is more sensitive for vascular aging than PP. METHODS: A cohort of 143 patients from 4 dialysis units has been followed measuring MogPWV and PP every 3 to 6 months and compared to a control group with the same risk factors but an eGFR > 30 ml/min. RESULTS: MogPWV contrarily to PP did discriminate the dialysis population from the control group. The mean difference translated in age between the two populations was 8.4 years. The increase in MogPWV, as a function of age, was more rapid in the dialysis group. 13.3% of the dialysis patients but only 3.0% of the control group were outliers for MogPWV. The mortality rate (16 out of 143) was similar in outliers and inliers (7.4 and 8.0%/year). Stratifying patients according to MogPWV, a significant difference in survival was seen. A high parathormone (PTH) and to be dialysed for a hypertensive nephropathy were associated to a higher baseline MogPWV. CONCLUSIONS: Assessing PWV on the brachial artery using a Mobil-O-Graph is a valid and simple alternative, which, in the dialysis population, is more sensitive for vascular aging than PP. As demonstrated in previous studies PWV correlates to mortality. Among specific CKD risk factors only PTH is associated with a higher baseline PWV. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02327962.

How to prevent venous cannula orifice obstruction during extracorporeal circulation.

Venous cannula orifice obstruction is an underestimated problem during augmented cardiopulmonary bypass (CPB), which can potentially be reduced with redesigned, virtually wall-less cannula designs versus traditional percutaneous control venous cannulas. A bench model, allowing for simulation of the vena cava with various affluent orifices, venous collapse and a worst case scenario with regard to cannula position, was developed. Flow (Q) was measured sequentially for right atrial + hepatic + renal + iliac drainage scenarios, using a centrifugal pump and an experimental bench set-up (afterload 60 mmHg). At 1500, 2000 and 2500 RPM and atrial position, the Q values were 3.4, 6.03 and 8.01 versus 0.77*, 0.43* and 0.58* l/min: p<0.05* for wall-less and the Biomedicus(®) cannula, respectively. The corresponding pressure values were -15.18, -31.62 and -74.53 versus -46.0*, -119.94* and -228.13* mmHg. At the hepatic position, the Q values were 3.34, 6.67 and 9.26 versus 2.3*, 0.42* and 0.18* l/min; and the pressure values were -10.32, -20.25 and -42.83 versus -23.35*, -119.09* and -239.38* mmHg. At the renal position, the Q values were 3.43, 6.56 and 8.64 versus 2.48*, 0.41* and 0.22* l/min and the pressure values were -9.64, -20.98 and -63.41 versus -20.87 -127.68* and -239* mmHg, respectively. At the iliac position, the Q values were 3.43, 6.01 and 9.25 versus 1.62*, 0.55* and 0.58* l/min; the pressure values were -9.36, -33.57 and -44.18 versus -30.6*, -120.27* and -228* mmHg, respectivly. Our experimental evaluation demonstrates that the redesigned, virtually wall-less cannulas, allowing for direct venous drainage at practically all intra-venous orifices, outperform the commercially available control cannula, with superior flow at reduced suction levels for all scenarios tested.

Analysis of flow dynamics in right ventricular outflow tract.

BACKGROUND: The mechanism behind early graft failure after right ventricular outflow tract (RVOT) reconstruction is not fully understood. Our aim was to establish a three-dimensional computational fluid dynamics (CFD) model of RVOT to investigate the hemodynamic conditions that may trigger the development of intimal hyperplasia and arteriosclerosis. METHODS: Pressure, flow, and diameter at the RVOT, pulmonary artery (PA), bifurcation of the PA, and left and right PAs were measured in 10 normal pigs with a mean weight of 24.8 ± 0.78 kg. Data obtained from the experimental scenario were used for CFD simulation of pressure, flow, and shear stress profile from the RVOT to the left and right PAs. RESULTS: Using experimental data, a CFD model was obtained for 2.0 and 2.5-L/min pulsatile inflow profiles. In both velocity profiles, time and space averaged in the low-shear stress profile range from 0-6.0 Pa at the pulmonary trunk, its bifurcation, and at the openings of both PAs. These low-shear stress areas were accompanied to high-pressure regions 14.0-20.0 mm Hg (1866.2-2666 Pa). Flow analysis revealed a turbulent flow at the PA bifurcation and ostia of both PAs. CONCLUSIONS: Identified local low-shear stress, high pressure, and turbulent flow correspond to a well-defined trigger pattern for the development of intimal hyperplasia and arteriosclerosis. As such, this real-time three-dimensional CFD model may in the future serve as a tool for the planning of RVOT reconstruction, its analysis, and prediction of outcome.

Effects of continuous positive airway pressure treatment on coronary vasoreactivity measured by (82)Rb cardiac PET/CT in obstructive sleep apnea patients.

PURPOSE: Obstructive sleep apnea syndrome (OSA) increases the risk of cardiovascular disease. We aimed at evaluating the effect of continuous positive airway pressure (CPAP) treatment on coronary endothelium-dependent vasoreactivity in OSA patients by quantifying myocardial blood flow (MBF) response to cold pressure testing (CPT). METHODS: In the morning after polysomnography (PSG), all participants underwent a dynamic (82)Rb cardiac positron emitting tomography/computed tomography (PET/CT) scan at rest, during CPT and adenosine stress. PSG and PET/CT were repeated at least 6 weeks after initiating CPAP treatment. OSA patients were compared to controls and according to response to CPAP. Patients' characteristics and PSG parameters were used to determine predictors of CPT-MBF. RESULTS: Thirty-two untreated OSA patients (age 58 ± 13 years, 27 men) and 9 controls (age 62 ± 5 years, 4 men) were enrolled. At baseline, compared to controls (apnea-hypopnea index (AHI) = 5.3 ± 2.6/h), untreated OSA patients (AHI = 48.6 ± 19.7/h) tend to have a lower CPT-MBF (1.1 ± 0.2 mL/min/g vs. 1.3 ± 0.4 mL/min/g, p = 0.09). After initiating CPAP, CPT-MBF was not different between well-treated patients (AHI <10/h) and controls (1.3 ± 0.3 mL/min/g vs. 1.3 ± 0.4 mL/min/g, p = 0.83), but it was lower for insufficiently treated patients (AHI ≥10/h) (0.9 ± 0.2 mL/min/g vs. 1.3 ± 0.4 mL/min/g, p = 0.0045). CPT-MBF was also higher in well-treated than in insufficiently treated patients (1.3 ± 0.3 mL/min/g vs. 0.9 ± 0.2 mL/min/g, p = 0.001). Mean nocturnal oxygen saturation (β = -0.55, p = 0.02) and BMI (β = -0.58, p = 0.02) were independent predictors of CPT-MBF in OSA patients. CONCLUSIONS: Coronary endothelial vasoreactivity is impaired in insufficiently treated OSA patients compared to well-treated patients and controls, confirming the need for CPAP optimization.