Volume Pulmonary Artery Research Articles

The hemodynamic and respiratory effects of diazepam (Valium).

Diazepam, 5–10 rag, was given intravenously to treat anxiety occurring during cardiac catheterization in 15 patients. Anxiety was effectively relieved in 11 patients. Hemodynamic and ventilatory parameters were assessed before, and ten and 30 minutes after diazepam. The cardiac index decreased significantly in only three patients, each of whom had a control cardiac index in the high-normal range. No significant changes occurred in patients whose control cardiac indexes were below normal. Systolic blood pressure decreased by more than 10 mm Hg in eight patients. Pulmonary arterial pressure, heart rate, stroke volume and pulmonary and systemic resistance did not change significantly. Hypoventilation occurred in all patients. Ten minutes after diazepam minute ventilation had decreased by 28 per cent and tidal volume by 23 per cent. Paco2 increased by 5 mm Hg and Pao2 decreased by 10 mm Hg. The observed changes in blood pressure and ventilation were without clinical correlates and did not require therapy.

Cardiovascular response to localized heating of the anterior hypothalamus.

1. The effects, on the systemic and pulmonary circulation, of localized heating of the anterior hypothalamus, at different environmental temperatures, have been studied in the unanaesthetized ox.2. In a cool environment (15 degrees C), heating the hypothalamus elicited panting which was associated with increases in cardiac output, heart rate, pulmonary arterial pressure and central blood volume, and decreases in systemic total peripheral resistance, and the percentage of red cells in mixed venous blood.3. In a hot environment (40 degrees C), the cardiovascular responses were of smaller magnitude than in the cool environment. It was suggested that the smaller responses in the hot environment were probably related to a higher level of blood flow through the skin before the hypothalamus was heated.4. The cardiovascular responses to localized heating of the anterior hypothalamus were similar to those which occur during hyperthermia. However, there were also differences between the effects of the two procedures and it was concluded that hyperthermia involves the stimulation of other receptors in addition to those in the anterior hypothalamus.

Differential reactivity in the pulmonary circulation.

A new method for relating regional intravascular resistance to pulmonary arterial, capillary, and venous pressure and volume was used to evaluate local differences of reactivity in the pulmonary blood vessels in the isolated lung lobe of the dog. Intravascular infusion of isoproterenol caused active dilatation of pulmonary arteries and veins. Capillary conductance (1/resistance) and volume increased, possibly as a result of the opening of previously closed capillaries. Serotonin infusion caused active constriction of both the pulmonary arteries and veins. A low dose of serotonin (1.5 mug/min per kg) caused predominant constriction of whichever vessels were upstream (arteries during forward perfusion, veins during reverse perfusion). A high dose of serotonin (4.5-5.0 mug/min per kg) caused constriction of both upstream and downstream vessels. Metabolic inactivation of serotonin by the lung is suggested as an explanation for these observations. Histamine infusion caused predominant venous constriction whether veins were upstream or downstream. Capillary volume and conductance decreased during forward and reverse perfusion, perhaps as a result of pericapillary edema formation. Large arterial vessels constricted slightly, whereas small arterial vessels appeared to be passively dilated.

Longitudinal distribution of vascular resistance in the pulmonary arteries, capillaries, and veins.

A new method has been described for measuring the pressure and resistance to blood flow in the pulmonary arteries, capillaries, and veins. Studies were performed in dog isolated lung lobes perfused at constant flow with blood from a donor dog. Pulmonary artery and vein volume and total lobar blood volume were measured by the ether plethysmograph and dyedilution techniques. The longitudinal distribution of vascular resistance was determined by analyzing the decrease in perfusion pressure caused by a bolus of low viscosity liquid introduced into the vascular inflow of the lobe. The pulmonary arteries were responsible for 46% of total lobar vascular resistance, whereas the pulmonary capillaries and veins accounted for 34 and 20% of total lobar vascular resistance respectively. Vascular resistance was 322 dynes .sec.cm(-5)/ml of vessel in the lobar pulmonary arteries, 112 dynes.sec.cm(-5)/ml in the pulmonary capillaries, and 115 dynes.sec.cm(-5)/ml in the lobar pulmonary veins. Peak vascular resistivity (resistance per milliliter of volume) was in an area 2 ml proximal to the capillary bed, but resistivity was high throughout the pulmonary arterial tree. The pulmonary arteries accounted for approximately 50% of vascular resistance upstream from the sluice point when alveolar pressure exceeded venous pressure. The method described provides the first measurements of pulmonary capillary pressure. Mid-capillary pressure averaged 13.3 cm H(2)O, pulmonary artery pressure averaged 20.4 cm H(2)O, and pulmonary vein pressure averaged 9.2 cm H(2)O. These techniques also provide a way of analyzing arterial, capillary, and venous responses to various pharmacologic and physiologic stimuli.

The effect of hyperthermia on the systemic and pulmonary circulation of the ox (Bos taurus).

The cardiac output, arterial blood pressure, pulmonary arterial pressure, heart rate, blood volume, respiratory rate and rectal temperature of the unanæsthetized ox have been measured at environmental temperatures of 150° C. and 400° C. (low humidity) and also during hyperthermia induced by increasing the humidity of the hot environment (400° C.). Derived values for total peripheral resistance, central blood volume and cardiac work were obtained from the measured data.The cardiac output, central blood volume and respiratory rate were significantly higher, while the mean blood pressure and calculated total peripheral resistance were significantly lower, in the hot dry environment than they were at 15° C. These results seemed to be consistent with the hypothesis that a peripheral vasodilatation and an increased venous return occurred in the hot dry environment.The increase in systemic arterial blood pressure during hyperthermia was attributed to the concomitant increase in cardiac output because the total peripheral resistance diminished. The increase in the cardiac output was the result of an increased heart rate. At a rectal temperature of 41.50° C. the stroke volume of the heart was considerably lower than its control value at an environmental temperature of 15° C. The work of the heart was increased during hyperthermia.The increased respiratory activity in hyperthermic animals was associated with a diminution of the mean pulmonary arterial pressure and an increase in the central blood volume.No statistically significant differences in plasma or blood volumes of the animals were recorded between environments of 15° C. and 40° C. (low humidity) and 40° C.(high humidity). The plasma volume tended to diminish during hyperthermia while the blood volume tended to be maintained close to its control value as a result of an increase in the proportion of red cells in the blood.At a rectal temperature of 41.5° C. none of the animals was in a state of circulatory failure, but there was evidence that their cardiovascular systems were severely stressed at this temperature.

Pulmonary arterial circulation time, pulmonary arterial blood volume, and the ratio of gas to tissue volume in the lungs of dogs.

Pulmonary arterial circulation time, pulmonary arterial blood volume, and the ratio of gas to tissue volume in the lungs of dogs.