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PubMed2001

[Experimental model of perinatal pulmonary circulation in lambs].

STUDY AIM: Mechanisms that modulate fetal pulmonary circulation and transitional circulation at birth are incompletely understood. The aim of this experimental study was to describe an animal model in order to study the perinatal pulmonary circulation. MATERIAL AND METHODS: Pregnant ewes were operated on between 126 and 128 days gestation (term = 145 days). A skin incision was performed to the fetal lambs in utero and catheters were placed into the ascending aorta and the superior vena cava after insertion in the axillary artery and vein. Then, catheters were inserted into the left pulmonary artery (LPA), main pulmonary artery, and left atrium via a thoracotomy. Moreover, an ultrasonic flow transducer, and an inflatable vascular occluder were placed around the LPA and around the ductus arteriosus. During 10 days, studies were performed in utero (possibly continued when fetal lambs were delivered by caesarean section). This chronically prepared animal may be used to perform hemodynamic studies according to different protocols (drugs injection to the fetus or to the ewes, ductus arteriosus compression, oxygen test). The main pulmonary artery, aortic, left atrial and amniotic pressures, heart rhythm, and flow signal were continuously recorded. RESULTS: Eighteen pregnant ewes were operated on and nine only could be used for experimentation. This ovine model permitted several studies, particularly about effects of catecholamines on the pulmonary circulation, and about effects of ductus arteriosus compression on the pulmonary circulation. CONCLUSION: Chronically instrumented fetal lambs are an excellent model in order to study the perinatal pulmonary circulation.

Animals↗
PubMed2004

Adenoviral gene transfer to the neonatal rat pulmonary circulation.

BACKGROUND: Gene delivery to the pulmonary circulation has been studied in adult animals, but has not been extensively investigated in neonates. METHODS: We tested the ability of recombinant, replication-defective adenovirus to transduce the pulmonary circulation when delivered by percutaneous ventricular puncture. Five-day-old rat pups were injected with 10(7) to 10(10) particles (approximately 10(5) to 10(8) pfu) in 30 micro l total volume. RESULTS: Using RT-PCR, we detected transgene expression in both lung and liver at all dosages. However, whereas only 1/6 pups injected with 10(7) particles had detectable expression, 8/9 pups in the two highest dose groups had detectable expression. In the highest dose group expression was approximately 5-fold greater in lung than liver, though in the lower dose groups no difference between lung and liver was found. Expression decreased by only 25% from day 4 through the last time point at day 28 in lung, whereas liver expression was undetectable in 7 of 9 samples on day 28. Histopathological examination demonstrated expression both within the media of large arteries and in small, peripheral arteries and capillaries, with a concentration of expression in the most distal areas of both the lungs and liver. No evidence of inflammation was seen. CONCLUSIONS: We conclude that the neonatal pulmonary circulation can be effectively transduced using systemic adenoviral vector injection, has more sustained expression than liver, and may be a target for therapeutic gene delivery.

Adenoviridae↗
PubMed1984

Effects of acetylcholine in the pulmonary circulation of rabbits.

The pulmonary and systemic vascular beds differ in their response to several vasoactive substances. Acetylcholine (ACh) is a potent systemic vasodilator; however, its effects on the pulmonary circulation are not clear. Utilizing the isolated rabbit lung preparation perfused in situ under constant flow (92 +/- 3 ml/min) with an albumin-enriched physiologic salt solution, we studied the effects of graded concentrations of ACh (10(-10) to 10(-4) M) in the recirculating perfusate on pulmonary arterial pressure (PAP). The lungs were ventilated to 15 cm of water with 97% O2-3% CO2. ACh (10(-8) to 4 X 10(-7) M) produced a dose-dependent increase in PAP which required up to 20 min to return to predrug levels. Physostigmine (10(-5) M) maintained the maximal PAP response to ACh for the duration of the experiment (up to 2 hr). Higher concentrations of ACh produced rapid increases in PAP resulting in edema. Pre- or post-treatment with the muscarinic receptor antagonist atropine (10(-5) M) completely prevented or reversed the pressor effects of ACh, respectively. Histamine receptor (H1 and H2) or angiotensin II receptor blockade had no effect on the PAP actions of ACh, however pretreatment with the prostaglandin synthesis (cyclooxygenase) inhibitor indomethacin (10(-5) M) or aspirin (10(-3) M), completely abolished the PAP response to ACh up to concentrations of 10(-4) M. In experiments in which airway pressure was allowed to vary, it rose significantly in response to increasing concentrations of ACh. ACh-induced increases in airway pressure were unaffected by pretreatment with indomethacin (10(-5) M) but were totally inhibited by pretreatment with atropine (10(-5) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1988

Relation of pressure and flow of pulmonary circulation in patients with chronic obstructive pulmonary disease.

A series of 31 patients with various degrees of chronic obstructive pulmonary disease underwent right heart catheterization using flow-directed thermodilution catheters. Both rest and supine exercise values were obtained. The patients were divided into two groups on the basis of their reduction in forced expiratory volume in 1 s (FEV1). In patients with FEV1 values of greater than or equal to 1,300 ml (group 1), the arterial oxygen partial pressure (PaO2) did not significantly change with exercise, while in patients with FEV1 of less than or equal to 1,200 ml (group 2) PaO2 significantly (p less than 0.05) fell in response to exercise. In group 2, a significant increase of total pulmonary resistance (TPR) with exercise was found (p less than 0.01). Pulmonary vascular resistance (PVR) remained unchanged in both subgroups. It is suggested that the value of PVR for subgroup 2 is artificially low because an important variable, namely pulmonary artery wedge pressure, is influenced by alveolar pressure in patients with an uneven distribution of perfusion and ventilation at pulmonary venous pressures lower than alveolar pressure. The steeper slope of the pressure-flow relationship in these patients is probably due to an increased vascular tone caused by chronic hypoxia at rest and further fall of PaO2 and rise of arterial CO2 partial pressure in response to exercise.

Adult↗
PubMed1999

Spiral CT angiography of the pulmonary circulation.

Spiral computed tomographic (CT) angiography of the pulmonary circulation has emerged recently as a potential useful diagnostic method for the evaluation of the pulmonary circulation. As a minimally invasive examination, this technique is becoming widely available and has progressively replaced conventional and digital pulmonary angiography as the standard diagnostic imaging modality of the pulmonary circulation. The purpose of this review is to capture the current state of the art of the technical aspects of spiral CT angiography, with special emphasis on the post-processing techniques currently available. As CT is responsible for a considerable part of the medical radiation dose applied to the population, the current trends for dose saving will also be emphasized. With regard to the clinical applications of spiral CT angiography, its introduction into the diagnostic work-up of pulmonary embolism has considerably modified the diagnostic algorithms. Our 8-year review of the literature presented herein is expected to provide the readers with a basis for formulating an informed opinion on this topic. In addition, a large number of congenital and acquired disorders of the pulmonary circulation are also relevant to this technique, and these indications are discussed in the context of the corresponding therapeutic options. Owing to the multiple possibilities inherent to this technique, spiral CT has the potential for cost savings without reduction in image quality or diagnostic accuracy.

Aneurysm↗
PubMed1990

Pulmonary circulation and burns and trauma.

The lung is a critical organ in victims of thermal injury or multiple trauma since the blood that drains injured organs circulates through the pulmonary circulation before passing through any other organ. The lung therefore will receive the first volley of cytotoxins released postinjury. In addition to being a target of injury, the lung may also contribute to the injury of systemic organs. This injury may be the result of a reduced delivery of oxygenated blood or the direct release of cytotoxins into the systemic circulation. The injury to the lung may be to the pulmonary microvasculature or the airway. The bronchial circulation responds to injury by a marked elevation in its blood flow and microvascular permeability. These latter effects may be important in mediating the changes which occur in the lung parenchyma.

Animals↗
PubMed1976

[Hemodynamic analysis of pulmonary circulation by microcatheter technique in healthy persons and in patients with pulmonary silicosis (author's transl)].

A comparison of hemodynamic analysis of pulmonary circulation in 18 healthy men (PM less than 20 Torr) and 19 patients with pulmonary silicosis (PM larger than or equal to 20 Torr) at rest and under work load gave following results: In most healthy persons pulmonary pressure rose under load while resistance of pulmonary circulation decreased significantly. In patients with silicosis pulmonary pressure being elevated at rest reached pathological values under load while resistance of circulation decreased less. There was no difference in cardiac time-volume between both groups. The authors found a linear correlation between cardiac time-volume and oxygen uptake related to body surface. They derived a formula of approximating cardiac time-volume by oxygen uptake and body surface.

Cardiac Output↗
PubMed1979

[Effects of isometric exercise on the right ventricular function and on the pulmonary circulation, in normal subjects (author's transl)].

The pulmonary circulatory response and right ventricular haemodynamics were assessed in normal subjects who sustained hand-grip exercise (HG) at 50% of the maximum voluntary contraction (M.V.C.) for 3 minutes. Ten normal subjects, aged 25 to 66 years, who underwent full right catheterization were studied. The following parameters were taken into consideration: heart rate (HR), end diastolic right ventricular pressure (EDRVP) end diastolic right ventricular volume (EDRVV), mean pulmonary arterial pressure (PAP), pulmonary wedge pressure (PWP), total pulmonary resistance (TPR), cardiac output (CO) and right ventricular sistolic work minute index (RVSWMI). These data were obtained by means of a tip-micromanometer connected with an polygraphic recorder and by means of thermodilution cardiac output computer. The statistical significance of the difference between the resting control values and those after isometric exercise was calculated with the Student's paired t test. A comparison of the control data with those obtained after isometric exercise, demonstrate a statistical significant (p less than 0,001) increase of the HR, PAP, PWP, TRP, CO, RVSWMI, a less significant (p less than 0.01) increase RVEDP. Our findings show that the HG causes changes in the pulmonary circulation and the right ventricular function. Our data seem to sustain that the pulmonary circulation respondes differently under isometric stress than it does under isotonic stress. The use of HG can thus be postulated as a useful means of evaluation of the response of the pulmonary circulation and right ventricular function.

Adult↗
PubMed1999

A fractal approach for evaluation of pulmonary circulation in man at rest and during exercise.

Changes in pulmonary circulation caused by muscular exercise and body position are usual in daily life. By using first-pass radiocardiography and fractal analysis, pulmonary circulation in man was evaluated at rest and during muscular exercise. At rest, pulmonary circulation was heterogeneous as described by the relative dispersion (which is the coefficient of variation, i.e. the standard deviation of the pulmonary transit times divided by the mean transit time; RD = 0.51 +/- 0.06) and fractal in nature. During exercise, pulmonary circulation became more homogeneous (RD = 0.35 +/- 0.04; P < 0.001). The calculated fractal dimension decreases from 1.09 at rest to 1.06 during exercise. The model identifies a cubic-law response for circulation heterogeneity and a quarter-power law for resistance during muscular exercise.

Adult↗
PubMed1986

Relationship of arterial wedge pressure to closing pressure in the pulmonary circulation.

We studied the relationship between the pulmonary artery wedge pressure (Pw) and pulmonary venous pressure (Ppv) at 2 alveolar pressures (PA) in 7 isolated perfused dog lobes. If PA were the critical pressure in the pulmonary circulation, one would expect Pw to equal Ppv for all Ppv greater than PA. Relative to the hilum, the average critical pressure in these lobes was 15.07 +/- 0.40 cmH2O at PA = 5 cmH2O and increased significantly to 17.23 +/- 0.82 cmH2O at PA = 7 cmH2O. Because the critical pressure in fact exceeded PA, Pw was found to be relatively constant and independent of Ppv even when Ppv exceeded PA by 5 cmH2O or more. For example, at PA = 5.13 +/- 0.04 cmH2O and Ppv = 9.64 +/- 0.28, the mean value for Pw was 13.30 +/- 0.59 cmH2O. Pw is equal neither to the average critical pressure nor to PA, but instead lies between these two values. It is determined by the spectrum of closing pressures in the pulmonary circulation, and the time-constants for drainage of beds downstream from the occluded pulmonary arterial branch.

Animals↗