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Biomedical subjects

W M Zapol

Publications and source records attributed to W M Zapol.

At least 163 records · Page 9Linked to original sources
PubMed1980

Fetal cardiovascular and metabolic responses to simulated diving in the Weddell seal.

Fetal responses to normobaric diving simulated by submersion of the maternal head for 20 min were studied in four conscious Weddell seals near term. Microspheres injected into the maternal aorta were distributed to the placenta and kidneys in the ratio of 0.4 in the control period and 19.3 during diving, suggesting minimal placental vasoconstriction. Fetal heart rate fell during diving from a mean control value of 90 to 34 beats/min after 4 min. The onset of fetal bradycardia was not consistently associated with changes in blood gas tensions. Diving was associated with a fall in fetal arterial O2 tension from 24 to 9 Torr, arterial CO2 tension rose from 47 to 85 Torr, and arterial pH fell from 7.35 to 7.24. Fetal-maternal gradients for CO2 and H+ transport remained constant, whereas the gradient for O2 transport fell from 47 Torr before diving to 14 Torr at the end of diving. Blood lactate concentrations increased three- to fourfold during diving and reached peak values 10-15 min after diving ended. The similarity of the fetal and maternal heart rate responses to diving is consistent with the presence of physiological oxygen-conserving reflexes akin to the adult's.

Animals↗
PubMed1980

Platelet consumption and sequestration in severe acute respiratory failure.

To evaulate alterations in platelek kinetics and organ sequestration patterns during acute lung injury, we studied the fate of autologous radiolabeled platelets in 15 patients with severe acute respiratory failure (ARF) of diverse etiology. Thrombocytopenia (< 100,000 platelets/microliters) occurred in 10 patients. Platelet lifespan was reduced (2.30 +/- 0.39 days; mean +/- SEM) compared with normal volunteers (6.29 +/- 0.69; p < 0.01). Platelet turnover rate during ARF (251,100 +/- 90,000 platelets/microliters x day) was twice normal and never below the normal range. Platelet sequestration, determined by surface scintillation counting, occurred in the lungs, liver, and spleen. Although our measurements in patients with severe ARF did not determine whether platelets cause or exacerbate acute lung disease, the increased platelet consumption and pulmonary sequestration we detected suggests that platelets are directly involved in the pathophysiology of acute lung injury.

Acute Disease↗
PubMed1979

Extracorporeal membrane oxygenation in severe acute respiratory failure. A randomized prospective study.

Nine medical centers collaborated in a prospective randomized study to evaluate prolonged extracorporeal membrane oxygenation (ECMO) as a therapy for severe acute respiratory failure (ARF). Ninety adult patients were selected by common criteria of arterial hypoxemia and treated with either conventional mechanical ventilation (48 patients) or mechanical ventilation supplemented with partial venoarterial bypass (42 patients). Four patients in each group survived. The majority of patients suffered acute bacterial or viral pneumonia (57%). All nine patients with pulmonary embolism and six patients with posttraumatic acute respiratory failure died. The majority of patients died of progressive reduction of transpulmonary gas exchange and decreased compliance due to diffuse pulmonary inflammation, necrosis, and fibrosis. We conclude that ECMO can support respiratory gas exchange but did not increase the probability of long-term survival in patients with severe ARF.

Acute Disease↗
PubMed1979

Regional blood flow during simulated diving in the conscious Weddell seal.

Changes in regional blood flow during simulated normobaric diving were studied in the conscious Antarctic Weddell seal (Leptonychotes weddelli) by injecting 25-microns radioactive microspheres into the left ventricle. Injections were performed before and 8--12 min after submersion of the head in iced seawater. Diving was associated with a fall in cardiac output from a mean control value of 39.8 +/- 10.2 to 5.6 +/- 3.4 l/min (mean +/- SD) and in heart rate from 52 +/- 15 to 15 +/- 4 beats/min. Blood flow to the splanchnic and peripheral vascular bed was reduced by more than 90%, cerebral blood flow was unchanged, right and left ventricular blood flow decreased by 85%, and adrenal blood flow decreased by 39%. The pulmonary fraction of the injected microsphere dose increased from 7.9 to 29.9% during diving. This may signify a large increase of peripheral arteriovenous shunting during the dive and/or increased bronchial artery blood flow. It is concluded that blood flow during diving is directed to organs and tissues according to their metabolic requirements.

Animals↗
PubMed1979

High corticosteroid levels in plasma of adult and foetal Weddell seals (Leptonychotes weddelli).

Pregnant and non-pregnant Weddell seals and foetuses were found to have very high plasma concentrations of corticosteroids (1--7 mumol/l) that were unaffected by stress. Cortisol comprised most of the corticosteroid in the adult but only 50% of that in the foetus. The affinity constant (4.30-5.53 x 10(7) l/mol) and specificity of CBG and the MCR (4.5 l/d/kg lean body mass) in adult seals were similar to those of Man. The binding capacity of CBG (1.48--1.86 mumol/l) which is approximately three times that of Man contributed to the high plasma corticosteroid concentrations but the main factor was the cortisol turnover rate of 3670 mumol/d (1.3 g/d) which is the highest value reported in any species.

Adrenal Cortex Hormones↗
PubMed1979

Lung transvascular fluid dynamics with extracorporeal membrane oxygenation in unanesthetized lambs.

Extracorporeal membrane oxygenation (ECMO) is used for long-term support of patients with acute respiratory failure. We investigated the effect of partial venoarterial (VA) and venovenous (VV) bypass with filler-free silicone spiral-coil membrane lungs on steady-state lung transcapillary fluid filtration in six unanesthetized lambs for periods of 11 to 32 hours. Using three thoracotomies we prepared animals to collect lung lymph; lymph obtained in this way is representative of lung interstitial fluid. By studying lymph flow and composition we demonstrated that the permeability of the pulmonary capillaries does not change during prolonged partial VV or VA bypass with a membrane lung. There was no accumulation of lung water during bypass, and lung protein and fluid leak neither increased not decreased with bypass flows equivalent to those used clinically. Thus prolonged use of ECMO in unanesthetized lambs appears to be neither harmful nor beneficial to the steady-state dynamics of fluid exchange in the lung. Furthermore, total pulmonary blood flow is not a determinant of net fluid filtration across the lung microcirculation.

Animals↗
PubMed1977

Pulmonary metabolism during diving: conditioning blood for the brain.

During experimental diving by the awake Weddell seal, blood glucose concentration falls consistently. A large fraction of the glucose consumed from the central circulating blood appears as lactate. During diving, the lung utilizes blood lactate in preference to blood glucose as a source of both carbon and energy, and it is able to release glucose into pulmonary venous blood to supplement the supply available for brain metabolism.

Animals↗
PubMed1977

Pulmonary hypertension in severe acute respiratory failure.

We repeatedly assessed pulmonary and systemic hemodynamics in 30 patients undergoing therapy for severe acute respiratory failure of diverse causes. Pulmonary-artery hypertension and elevated pulmonar vascular resistance were observed in all patients after correction of systemic hypoxemia. Increasing pulmonary blood flow by isoproterenol infusion or decreasing pulmonary blood flow by partial bypass of the right side of the heart minimally altered pulmonary-artery pressure. Although neither elevated pulmonary vascular resistance nor low cardiac index reliably predicted death, survivors had preogressive decreases of pulmonary vascular resistance with time, whereas nonsurvivors tended to maintain or increase pulmonary vascular resistance. Right ventricular stroke-work index was markedly elevated in all patients. The work load imposed upon the right ventricle by elevation of pulmonary vascular resistance may be a factor limiting survival in severe acute respiratory failure.

Acute Disease↗
PubMed1977

Week long partial pulmonary bypass with an artificial lung pumped by the right ventricle.

Extracorporeal pumping PA-LA perfusions were carried out for 24 hrs in 5 awake, alert lambs by cannulating the main PA and the LA with large bore polyurethane cannulae. A mean of 42% of the basal cardiac was pumped through the membrane lung. When the PA occluder cuff was progressively inflated, up to 80% of the basal cardiac output was diverted to the extracorporeal circuit for short periods. Hemothorax remained a significant problem. Three lambs were electively perfused 12 hrs, 36 hrs, and 8 days without a roller pump, using a low resistance spiral coil membrane lung pumped by the RV. By inflating the occluder cuff, a mean of 55% of basal cardiac output was pumped by the RV through the membrane lung. The 8 day bypass lamb remained healthy and active without any bleeding or gross pathology. We did not observe air emboli, thromboemboli or gross infections in either group. We believe that such a mode of cannulation will eventually allow long-term perfusion of a low resistance membrane oxygenator driven directly by the RV.

Animals↗