Simulation of blood flow in microgravity.

Knowledge of venous, capillary, and arterial blood flow in microgravity is required to modify hemostatic techniques for control of bleeding in traumatic injuries or surgical procedures in space. To simulate human arterial, venous, and capillary bleeding, fresh whole bovine blood was injected by two operators at calculated flow rates (3.5, 7, and 14 mL for venous and 14 and 28 mL for arterial) in 10 seconds with empirical controls in a lucent glove box during zero gravity parabolic flight on NASA's KC-135 aircraft. A pig's foot was used to mimic capillary bleeding. Hemostasis with sponges and laerdal suction was evaluated by video and still photography. Evaluations of the arterial and venous bleeding were conducted at 3 rates x 3 parabolas, and capillary bleeding was evaluated with 5 parabolas x 2 methods (pig's foot and sponge). Influenced by surface tension, the slow venous bleeding coated syringe surfaces and formed a dome over the skin laceration bleeding site. Arterial and venous bleeders broke into uniform spheres with low-velocity spheres bouncing off an absorbent pad and suction tip. Conventional dabbing with gauze fragmented blood into small spheres. Capillary oozing was better controlled by "wicking" up blood with gauze. Repeated arterial bleeding opacified the glove box wall. This stimulation demonstrated unique characteristics of extracorporeal blood flow and inadequacies of common methods of hemostasis in microgravity.     

Comparison of peak flow gauge and peak flow meter.

A comparison has been made of the new peak flow gauge and the Wright peak flow meter. Close correlation was found between measurements made with the two instruments both in normal subjects and in patients. The peak flow gauge is as consistent as the peak flow meter but is cheaper and more portable. It should be useful in survey work in general practice and for loan from hospital outpatient departments where serial measurements are used to monitor patients' progress.     

Gas flow in relation to blood flow in oxygenators. An evaluation of the new Shiley bubble oxygenator.

A new bubble oxygenator, designed by the Shiley Laboratories, which utilizes a low gas flow for oxygenation, was first tested in dogs and then in 100 clinical cases. For perfusion in adult patients, a gas flow as low as 0.6 litre oxygen per 1 litre blood has given adequate oxygenation and removal of carbon dioxide with no untoward effect on the blood, as compared with other oxygenators, including the membrane type.     

Variability of peak flow in wheezy children.

A study of peak flow variability was carried out among a population sample of 63 wheezy children aged 9-11 years. Recordings were made over 12 days at three times during the day--first thing in the morning, on returning home from school and at bedtime. Eighty nine per cent of the children had symptoms during the diary period. The mean amplitude (difference between the highest and lowest daily peak flow values) was 17% of the mean daily value (range 4-48%). By cosinor analysis the amplitude was 12% of the mean value (range 1-53%). In 65% of the children the lowest point of the daily rhythm as determined by cosinor analysis lay between midnight and 8am; the rhythm was, however, statistically significant in only fourteen individuals (22%). These levels of variability are considerably lower than those previously reported in hospital based studies of adult asthmatics. As a method of demonstrating variable airflow obstruction, which is the defining physiological characteristic of asthma, the use of a peak flow diary alone appears to be of limited value in children.     

Micturition urodynamic flow studies in children.

Voiding abnormalities are encountered frequently in pediatric patients. Symptoms of daytime incontinence, frequency and nocturnal enuresis in any combination may indicate underlying neurophysiologic detrusor imbalance. Incomplete evaluation of these symptoms can result in inappropriate medical therapy or even ineffective operations. Within the preceding 7 months 34 children with hard-core voiding abnormalities were evaluated with urodynamic techniques. Several categories of abnormal voiding patterns were identified, including the hyperactive external sphincter, uninhibited pediatric neurogenic bladder, detrusor hyperreflexia secondary to chronic cystitis, hyperactive external sphincter with hypotonic bladder and the hyperactive external sphincter with detrusor irritability. All patients received specific pharmacotherapy based on presenting signs and symptoms, and voiding pattern abnormality. Of the 24 patients who have been treated in this manner and were evaluated 83.5% have had complete remission of symptoms while on therapy, the remainder being improved but still having occasional symptoms. The technique and data demonstrate that children with hard-core voiding abnormalities can achieve rehabilitation with urodynamic assessment.     

Age-related variation in urinary flow variables and flow curve patterns in elderly males.

A group of randomly selected males, over 50 years of age, was examined with regard to history and urinary flow rate. Originally, the group had comprised 93 men without voiding problems, 15 who, although suffering from voiding problems, had not yet contacted their doctor, and 4 who had contacted their doctor because of voiding problems. Five years later the data were re-examined and 61 men were fully investigated again; in the remaining 51 patients only the history was updated. The 2 sets of data were evaluated separately as 2 cross-sectional investigations and as paired data sets by means of non-parametric statistical analysis. All uroflow variables were considered, i.e. Qmax, Qave, Qmax-time, Q "corrected", volume and the ratio Qmax/Qmax-time. In addition, the flow curve configuration was classified as normal or abnormal. When compared as 2 cross-sectional investigations, the latter confirmed the results of the first. Qmax, Qave, Q "corrected" and volume decreased with advancing age, but no correlation could be demonstrated between Qmax-time and age. The flow curve pattern altered, so that a normal flow curve was seldom seem at an advanced age. Uroflow variables tended towards the abnormal with advancing years and symptoms increased concurrently. These changes were largely accepted by the elderly males. Thus the decision to operate for benign prostatic hyperplasia should be based on both history and urinary flow.     

Calf blood flow in intermittent claudication.

Calf blood flow was correlated with severity of symptoms in 24 patients with intermittent claudication. Calf blood flow was measured (Whitney strain gauge) at three levels of demand--at rest, after exercise ("open"), and after exercise with total vascular occlusion by a tourniquet about the thigh ("closed"). The results showed significant correlation between the patients' reported capacity to walk and measured exercise tolerance on an ergometer (P less than or equal to .01). The coefficients of correlation between exercise tolerance and calf blood flow (resting, postopen or postclosed exercise) or the vascular reserve (difference between postopen and postclosed exercise hyperemia) were not significant. It is concluded that capacity for walking in cases of intermittent claudication is not a reliable index of the calf blood flow. The relationship between these factors would be clearer if the patients pain threshold and calf tissue metabolic activity were known also.     

Whole pancreatic blood flow and islet blood flow in hypovolemic hypotension in rats.

The blood volume of adult, male rats was reduced with 5 ml (approximately 30% of the total blood volume) by bleeding, which reduced the mean arterial blood pressure (MAP) to 50 mm Hg. This hemorrhagic hypotension caused an increase in both serum glucose and serum insulin concentrations when compared with either normotensive control animals or with rats infused with nitroprusside to obtain an MAP similar to that of the bled animals. The blood perfusion of the whole pancreas was reduced in both groups of hypotensive animals but more markedly in those with hemorrhagic hypotension. The islet blood flow was reduced only in the bled animals. The percentage fraction of blood diverted through the islet organ was markedly increased in bled rats compared to the control animals, whilst this increase was less pronounced in the nitroprusside-infused rats. The vascular conductance in the nitroprusside-treated rats was unchanged for the whole gland, but increased for the islets. Both these values in bled animals were decreased. It is concluded that the blood flow regulation differs between the endocrine and exocrine parts of the pancreas in hypovolemic hypotension.