The fibroprotein network of the pulmonary interalveolar wall

The oxygen environment of the arterial media in early rabbit hypertension

Hypertensive stimuli in experimental animals appear to cause early arterial wall hypermetabolism before hypertension is established and before histomorphic changes are marked. Hypermetabolism and the large diffusion distances for oxygen characteristic of large arteries imply that mural hypoxia could occur early in the disease but this has not been studied. Therefore, we measured aortic wall tissue oxygen distributions in male New Zealand White rabbits 2 weeks (1) after production of upper body hypertension by coarctation of the abdominal aorta, (2) after sham operation, and (3) in normal controls. As compared to normal and sham operated animals, blood pressure in the coarctation animals was significantly elevated from control levels, and the oxygen partial pressures were significantly reduced throughout the media. However, the hypoxic mural oxygen tensions in this relatively thin wall were not low enough to terminate classical respiration. At the time of measurement, moderate microscopic pathology was already present, including increased connective tissue production. The accompanying histomorphic changes are compatible with reports of extrarespiratory oxygen sensitivity of connective tissue metabolism.

In vivo oxygen transport in the normal rabbit femoral arterial wall

In vivo measurements of tissue oxygen tension were made at 10-micrometer intervals through functioning in situ rabbit femoral arterial walls, using inhalation anesthesia and recessed microcathodes with approximately 4-micrometer external diameters. External environment was controlled with a superfusion well at 30 torr PO2, 35 torr PCO2. Blood pressure, gas tension levels, and blood pH were held within the normal range. Radial PO2 measurements closely fit a mathematical model for unidimensional diffusion into a thick-walled artery with uniform oxygen consumption, and the distances traversed fit measured dimensions of quick-frozen in vivo sections. Using standard values of diffusion and solubility coefficients, mean calculated medial oxygen consumption was 99 nl0/ml-s. Mural oxygen consumption appeared to be related linearly to mean tangential wall stress. Differences in experimental design and technique were compared with previous in vivo and in vitro measurements of wall oxygenation, and largely account for the varying results obtained. Control of environment external to the artery, and maintenance of normally flowing blood in the lumen in vivo appeared critical to an understanding of mural oxygenation in life. If the conditions of this experiment prevailed in arteries with thicker avascular layers, PO2 could have been 20 torr at approximately 156 micrometer and 10 torr at 168 micrometer from blood (average values).

Measurement of cardiac output by impedance cardiography in patients with myocardial infarction. Comparative evaluation of impedance and dye dilution methods

The cardiac output was measured simultaneously by the impedance cardiography and dye dilution methods in 10 patients with acute myocardial infarction 2-3 weeks after admission to the Coronary Care Unit. The impedance cardiac output was on the average 9.7% higher than the dye dilution cardiac output. The reproducibility of impedance cardiac output 4.1%, compared with 5.1% for the dye dilution method. The study showed a satisfactory reliability of impedance in predicting the relative changed of cardiac output in response to tilting from the supine to the 30 degrees head-up position, to a 10 degrees head-down position, and to the intravenous administration of propranolol.

Comparison of indices of muscle and pump performance in patients with coronary artery disease

During diagnostic cardiac catheterization of 20 patients, 19 of whom had coronary artery disease (CAD), left ventricular (LV) performance was assessed by both muscle function indices and pump function indices. Muscle function indices included max dP/dt, Vpm, Vce5, and Vmax, the latter derived from both total pressure (TP) and developed pressure (DP) using catheter-tip manometry. Pump function indices included LV ejection fraction (EF) and percent abnormally contracting segment (ACS), determined from biplane LV angiography. Muscle and pump function indices were also compared to the presence of the S3 (ventricular diastolic) gallop. Correlations existed between EF and Vmax (TP), EF and Vpm, percent-ACS and Vmax(TP), and percent-ACS and Vpm, with r values of 0.760, 0.777, -0.884, and -0.841, respectively. Vmax(TP) and Vpm also correlated quantitatively with the presence of the S3 gallop (p less than 0.0005). Total pressure-derived muscle function indices appear to adquately describe mean LV performance in patients with CAD and ACS, but these muscle function indices are probably highly dependent upon the size of the myocardial scar.