Pulmonary hemodynamics after endotoxin administration: change in pulmonary capillary blood flow

Development of an experimental model of an acute respiratory failure by intratracheal sea water infusion: a comparison with a conventional oleic acid induction

An experimental model of acute respiratory failure (ARF) was successfully developed in dogs by endotracheal sea water infusion. Serial changes in blood gases and hemodynamics, and histological changes in the lungs after use of this method were compared with those of the conventional model induced by oleic acid, and the following results were observed. Blood gases deteriorated more rapidly after sea water than after oleic acid, while the changes caused by oleic acid progressed with time, and those caused by sea water did not. Not only systemic but also pulmonary hemodynamics were adversely influenced by oleic acid, but not by sea water. Extravascular lung water was observed to increase significantly in both groups. The increase was linear after oleic acid treatment, however, while with the sea water method it leveled off to a plateau. There was no significant difference between the histological changes in lungs of the two models. Our model will provide many advantages over the conventional one using oleic acid, and will be useful for studying the pathophysiology of ARF and its therapeutic strategies, such as extracorporeal membrane oxygenation and/or carbon dioxide removal.

Pulmonary hypertension in sepsis: measurement by the pulmonary arterial diastolic-pulmonary wedge pressure gradient and the influence of passive and active factors

To examine the relative roles of passive factors (flow; filling pressures of left side of heart) and active factors (acidosis; arterial unsaturation) in the genesis of pulmonary hypertension when associated with sepsis, 37 patients with sepsis and 24 patients without sepsis were examined. Pulmonary hypertension was measured by the pulmonary arterial diastolic-pulmonary wedge pressure gradient (PAd-PWP gradient) and correlated reasonably with a standard formula for calculated resistance ([PA--PWP]/CI, where PA is mean pulmonary artery pressure and CI is cardiac index). In 22 of 37 patients, sepsis was associated with a significant degree of resistance to flow in the pulmonary circulation, as measured by the PAd-PWP gradient: and the higher the PAd--PWP gradient, the greater the likelihood of early death. None of the examined passive or active factors appeared to be adequate to explain pulmonary hypertension when present. By the use of previously derived formulae to estimate the compliance of the elastic pulmonary arteries, factors affecting this part of the pulmonary microcirculation could not be held accountable for apparent pulmonary hypertension. Therefore, the presence of pulmonary hypertension in sepis appears to be an active, rather than a passive, phenomenon and unrelated to arterial oxygen saturation or acid-base imbalance. Although the exact cause is unknown, pulmonary hypertension in sepis is associated with a high mortality and may be clinically followed by measurement of the PAd-PWP gradient.