Pulmonary Insufficiency in the Rat After Intravascular Coagulation and Inhibition of Fibrinolysis - Studies on Pulmonary Microcirculation and Pathophysiology

In posttraumatic pulmonary insufficiency microembolism of fibrin to the lungs and inhibited fibrinolysis have been given key-roles and the term "the delayed microembolism syndrome" has been designated to those cases. The pathogenetic mechanisms involved are only to a limited extent known. Those were investigated in a rat model. Fibrinolysis was inhibited with AMCA and intravascular coagulation induced by a 5-min injection of thrombin, 500 NIH/kg b.w.. Within 5 min a profound consumption of fibrinogen occurred and 125-la- belled fibrin was embolized to the lungs. At that time the alveolar circulation was decreased, vasoconstriction and platelet-red cell aggragates appeared as seen by in vivo microscopy and arterial P02 was diminished irrespective of fibrinolysis. After restitution for 1 h a progressive pulmonary insufficiency with P02 decrease and PC02 retention occurred. Trasylol® did not influence on pulmonary damage. Converting enzyme activity was not diminished. A retention of fibrin degradation products (fdp) occurred in the lungs and infusion of low molecular weight fdp aggravated pulmonary oedema. Lung mast cells were partly degranulated and mepyramine maleate slightly counteracted pulmonary oedema. It is concluded that release of vasoactive low molecular weight fdp probably plays a causal role in oedema formation; probably in part by releasing histamine from lung mast cells.

Pulmonary Insufficiency in the Rat After Intravascular Coagulation and Inhibition of Fibrinolysis - Studies on Pulmonary Microcirculation and Pathophysiology

In posttraumatic pulmonary insufficiency microembolism of fibrin to the lungs and inhibited fibrinolysis have been given key-roles and the term “the delayed microembolism syndrome” has been designated to those cases. The pathogenetic mechanisms involved are only to a limited extent known. Those were investigated in a rat model. Fibrinolysis was inhibited with AMCA and intravascular coagulation induced by a 5-min injection of thrombin, 500 NIH/kg b.w.. Within 5 min a profound consumption of fibrinogen occurred and 125-la-belled fibrin was embolized to the lungs. At that time the alveolar circulation was decreased, vasoconstriction and platelet-red cell aggragates appeared as seen by in vivo microscopy and arterial PO2 was diminished irrespective of fibrinolysis. After restitutio for tha progressive pulmonary insufficiency with PO2 decrease and PCO2 retention occurred. Trasylol did not influence on pulmonary damage. Converting enzyme activity was not diminished. A retention of fibrin degradation products (fdp) occurred in the lungs and infusion of low molecular weight fdp aggravated pulmonary oedema, l.ung mast cells were partly degranulated and mepyramine maléate slightly counteracted pulmonary oedema. It is concluded that release of vasoactive low molecular weight fdp probably plays a causal role in oedema formation; probably in part by releasing histamine from lung mast cells.

An objective determination of +Gz acceleration tolerance

Until recently, human +Gz acceleration tolerance has relied solely on subjective criteria relating to loss of vision. By use of newly developed noninvasive instrumentation using a transcutaneous Doppler flow system, objective end point criteria have been developed based on measured blood flow to the head. The system consists of miniature 8 MHz Doppler sensors (2 x 1 x 0.5 cm) placed on the forehead over both frontal branches of the temporal arteries to detect blood flow velocity from back scattered ultrasound. Its use has allowed for correlation of altered, decreased and actual reversal of eye level blood flow with subsequent central light loss. Over 100 subjects have now been studied during more than 2,000 centrifuge runs. Objective changes in temporal artery flow velocity consistently preceded visual degradation for each subject during all acceleration profiles. No subject has gone unconscious without first exhibiting a minimum 6 sec of total flow cessation. Retrograde flow followed by complete flow cessation always preceded central light loss. Results indicate that this method can be successfully used with a wide variety of tasks during exposure to +Gz acceleration. It is recommended for use during evaluation of protective maneuvers or devices on the centrifuge or during actual flight in high performance aircraft. It may also serve as a potential safety monitor during space Shuttle re-entry if there is doubt about a passenger's cardiovascular status.

Left ventricular mechanical efficiency in man with heart disease

Thirty-eight adults with valvular and/or myocardial disease had heart catheterization with coronary blood flow and myocardial O2 consumption (MVO2) per 100 g measured by the nitrous oxide washout technique. Quantitative biplane angiocardiography was performed to assess left ventricular volume, mass, ejection fraction and work. Left ventricular efficiency was calculated from work, MVO2/100 g and mass. Efficiency ranged from 4 to 40% and was normal in some patients with severe ventricular pressure-volume work overloads. Total left ventricular MVO2 ranged up to 461 ml/min. Neither total MVO2 nor MVO2/100 g was significantly related to ventricular work, ejection fraction, or tension-time index. These data suggest 1) a relationship between left ventricular efficiency and myocardial function in chronic valvular or myocardial disease, 2) that efficiency may be normal in hypertrophied ventricles, and 3) that chronic increases in resting ventricular metabolic requirements are met by hypertrophy rather than by increased MVO2/100 g.

Cardiovascular function during sustained +Gz stress

The development of aerospace systems capable of very high levels of positive (+Gz) stress, has created a need for a better understanding of the cardiovascular responses to acceleration. Using a canine model, the heart and cardiovascular system were instrumented to continuously measure coronary blood flow, cardiac output, left ventricular and aortic root pressure, and oxygen saturation in the aorta, coronary sinus, and right ventricle. The animals were exposed to acceleration profiles up to +6 Gz, 120 s at peak G; a seatback angle of 45 degrees was simulated in some experiments. Radiopaque contrast medium was injected to visualize the left ventricular chamber, coronary vasculature, aorta, and branches of the aorta. The results suggest mechanisms responsible for arrhythmias which may occur, and subendocardial hemorrhage which has been reported in other animals.

A multichannel implantable telemetry system for flow, pressure, and ECG measurements

The design of telemetry systems for chronic implantation within the body have progressed from simple single-channel devices to complex multichannel systems over the last 15 yr. Although chronic measurements of temperature, ECG, and pressure have been reported with good results, measurements such as dimension and blood flow have been difficult because of heavy power requirements. The design to be described is a multiplex system that will measure up to eight individual parameters simultaneously, including blood flow. Flow is measured using an electromagnetic transducer, and by special design, the normal high power requirements of the electromagnetic technique have been reduced to a few hundred milliwatts. The system is powered by two NiCad, rechargeable batteries which are periodically recharged through the intact skin by induction at 250 kHz to an implanted pickup coil. The presently constructed units have been configured to measure ECG, two pressures, temperature and ascending aortic flow.

+Gz tolerance in man after 14-day bedrest periods with isometric and isotonic exercise conditioning

The purpose of this study was to determine the effects of isometric or isotonic exercise training on post-bedrest +Gz tolerance. Seven male volunteers, 19-22 years, underwent accelerations of +2.1 Gz (740 s), +3.2 Gz (327 s), and +3.8 Gz (312 s) in a selected, randomized order; the ramp to peak acceleration was 1.8 G/min. The centrifugation runs were terminated by loss of central vision (blackout) to a white light with a luminance of 3.15 times 10-5 log candle/cm-2 (0.092 ft-lambert). The study began with a 14-d ambulatory control period, followed by three 14-d bedrest periods (each separated by a 21-d recovery period) and then a final week of recovery. During the ambulatory periods, the subjects exercised on a bicycle ergometer at 50% of their maximal oxygen uptake (max VO2) for 1 h/d. During two of the three bedrest periods, the subjects performed in the supine position one of two routines, either isometric exercise (21% of max leg extension force for 1 min followed by 1-min rest) or isotonic exercise (68% of max VO2) for 0.5 in the morning and afternoon. During the third bedrest period, no exercise was performed. In general +Gz tolerance was reduced by 24% to 35% (p less than or equal to 0.05) after bedrest. Compared with control values, there were significant reductions in average tolerance times after bedrest with no exercise and isotonic exercise at all G levels. With isometric exercise, there was a significant decrease in tolerance at 2.1 Gz but not at 3.2 Gz or 3.8 Gz, even though the latter tolerances were reduced 15.6% and 10.0%, respectively. Both exercise regimens maintained tolerance at levels equal to or above that obtained with no exercise. Compared with control values, average tolerances were lower (p less than or equal to 0.05) after the two recovery periods between the bedrest periods (minus 24% to minus 26% at 3.2 Gz and 3.8 Gz), indicating that 3 weeks of ambulation was not sufficient time for full recovery from the deconditioning induced in this study. A prediction equation was constructed with data from all comparable studies utilizing deconditioned men riding relaxed without protective garments: Tolerance (in seconds) equals minus 334 + (1715/+Gz level). From this equation, the calculated tolerance after bedrest is 13.5 min at 1.5 G, and the point of zero tolerance is 5.1 Gz.

Light-pen computer processing of video image for the determination of left ventricular volume

A volume angiography system for on-line computation of left ventricular angiograms has been developed utilizing a video disc recorder, a light-pen unit, and a digital computer. The video disc recorder allows for immediate replay and stop-motion of ventricular angiograms on a video monitor. The light-pen is used by a technician/physician operator to define the margins of the ventricular chamber and input the data directly to the digital computer. The computer, utilizing the arealength method, applies preset magnification factors and calculates the ventricular volume. Comparison of this light-pen computer system with conventional manual processing of cine film yielded a correlation coefficient of 0.99. The equipment configuration employed in this system offers the advantages of available hardware components and operational simplicity. The major benefit has been avoidance of the logistic delays involved in cine film processing and handling, which have been obviated by the on-line capability of the video disc, light-pen, and computer combination.

Relationship between changes in left ventricular dimensions and the ejection fraction in man

Left ventricular length and calculated diameter were derived from angiocardiograms in 24 subjects with various heart diseases. Chamber diameter was noted to decrease an average of 27.5% from end-diastole to end-systole, and chamber length decreased 13%. Only subjects with calculations of left ventricular mass differing less than 25% from end-diastole to end-systole were accepted in order to avoid effects of spurious increases in end-systolic wall thickness on calculated diameter. Patients with localized disorders of contraction were also excluded. An extremely close linear relationship between the percentage change in diameter and the ejection fraction was demonstrated. Analysis of the radii of curvature showed that the lateral wall usually straightens during systole. However, if extreme ventricular dilatation is present, the lateral-wall curvature increases with systole. The possible implications of this alteration in contraction pattern and its effect upon the ejection fraction were discussed.

A quantitative angiocardiographic study of left ventricular hypertrophy and the electrocardiogram

The QRS amplitude, duration, and mean axis direction of the standard 12-lead electrocardiogram were compared with left ventricular mass, volume, wall thickness, and stroke work in 112 adult patients. These patients had normal left ventricles or various degrees of left ventricular dilatation or hypertrophy. Left ventricular volumes and mass were determined by a quantitative angiocardiographic method. A significant but not a close correlation between left ventricular mass and ECG voltage was found. Enddiastolic volume, stroke volume, stroke work, wall thickness, and "total left ventricular volume" (volume of left ventricular muscle and cavity at end-diastole) had generally lesser degrees of correlation with the QRS amplitude than did the mass alone. Subgrouping of patients into those with pressure overload on the left ventricle, volume overload, aortic valve disease, or anatomic left ventricular hypertrophy did not improve correlations. The left ventricular hypertrophy voltage criteria of Sokolow and of Grant were assessed; respectively, 68% and 67% of 75 patients with anatomic hypertrophy had hypervoltage. The direction of the anatomic long axis of the left ventricle was not significantly related to the mean QRS-vector direction.

The in vivo determination of left ventricular volume. Comparison of the fiberoptic-indicator dilution and the angiocardiographic methods

End-diastolic volumes, stroke volumes, and ejection fractions determined in quick succession by the fiberoptic indicator-dilution technique and the angiocardiographic method were compared in 63 patients with various disorders, aged 6 weeks to 58 years. The calibration methods are discussed in detail.

Good agreement was found (r=0.965) although end-diastolic volume by the fiberoptic-indicator method (FO) (mean, 106.3 ml/m 2 ) consistently exceeded enddiastolic volume by the angiocardiographic method (A) (92.5 ml/m 2 ). Variations in injection techniques, the absolute size of the volume (range, 31.0 to 478.5 ml/m 2 ), and heart rate (from 55 to 179 beats/min) did not influence this correspondence significantly.

Stroke volumes, ejection fractions, and end-systolic volumes were compared in 41 patients with nonregurgitant lesions. The correlation coefficients are 0.808, 0.824, and 0.950, respectively.

These results show better agreement than was previously suggested by workers utilizing other indicator-dilution systems. Reasons for this finding, such as the fact that studies were carried out in quick succession in the same patients, the advantage of indocyanine green over other indicators, the characteristics of the fiberoptic sampling system, the adequacy of mixing in the human left ventricle, and the errors inherent in the angiocardiographic method are discussed. Since agreement existed over a wide range of volumes, a set of regression equations was calculated that permitted the interchange of stroke volume, ejection fraction, and end-systolic and end-diastolic volumes in situations where one technique is favored over the other. Thus, for end-diastolic volume by angiocardiography, EDV A =0.785 EDV FO + 10.6 (in ml/m 2 ).

Mechanisms of pulsus alternans

The mechanisms of pulsus alternans were studied in three patients by cineangiographic determinations of left ventricular volume. In two patients with left ventricular disease, pulsus alternans occurred without detectable variation in left ventricular enddiastolic pressure (LVEDP) or end-diastolic volume (EDV), although in the second case these values did alternate in the initial postextrasystolic beats. Another patient with normal left ventricular function had brief postextrasystolic pulsus alternans associated with LVEDV alternations. Twenty-nine patients with valvular aortic stenosis who showed pulsus alternans during left heart catheterization were also studied. Persistent alternation in LVEDP occurred in eight, with transient LVEDP alternation appearing after extrasystoles in 22 cases. Cardiac cycle length and diastolic interval alternation occurred inconsistently.