bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acid-base changes in blood and cerebrospinal fluid during altered ventilation
Authors: Merwarth C. R. , Sieker H. O. 
Published: December 2017

Functional abnormalities of the central nervous system are observed with hypo- and hyperventilation. This study correlates changes of pH, carbon dioxide tension and carbon dioxide content in arterial and cerebral venous blood and cerebrospinal fluid during altered ventilation. With the experimental design in which ventilation was controlled and the sagittal sinus, femoral artery, and cisterna magna were cannulated, a slight metabolic acidosis was found. With 10% CO2 inhalation acidosis occurred in both blood and spinal fluid and early in the period of inhalation, the usual cerebrospinal-arterial fluid pCO2 gradient was reversed. With hyperventilation, pH and pCO2 changes were more pronounced in the arterial blood but, as hyperventilation was continued, the arterial-cerebrospinal fluid difference decreased. It appeared likely that brain tissue acts as an important buffer, absorbing and releasing CO2 during states of altered ventilation. CO2 diffuses rapidly across cell boundaries, whereas bicarbonate crosses more slowly, thus providing an explanation for the differences noted between blood and cerebrospinal fluid. The particular clinical importance of these observations is that arterial pH, pCO2, and CO2 content may not accurately reflect changes within the cerebrospinal fluid or brain when ventilation is altered. Submitted on May 1, 1961
Carbon dioxide transport in anesthetized dogs during inhibition of carbonic anhydrase
Authors: Cain Stephen M. , Otis Arthur B. 
Published: December 2017

Following inhibition of blood carbonic anhydrase by acetazolamide in anesthetized dogs with one lung rebreathing in connection with a bag and with the other lung ventilating freely on pure oxygen, mixed venous Pco2 increased and alveolar Pco2 decreased. Carbon dioxide output dropped initially but gradually rose and attained a steady state value equal to that of the initial control condition. Before acetazolamide, 19% of the pulmonary CO22 output was derived from dissolved CO2, 26% from carbamino compound, and 55% from bicarbonate. In the new steady state following acetazolamide, 45% came from dissolved CO2, 38% from carbamino, and 17% from bicarbonate. Submitted on June 12, 1961
Transition between laminar and turbulent flow in human trachea
Authors: Dekker E. 
Published: December 2017

The critical velocities at which turbulence appears were determined, during the flow of both water and air, in 21 transparent plastic casts of human tracheae. The flow patterns varied considerably in casts from different individuals. The critical flow velocity of air moving through tracheal casts without the larynx averaged about 350 ml of air per second. In tracheal casts including the larynx, with the glottis in cadaveric position, the critical inspiratory flow was about 50 ml of air per second. With the glottis opened into a more natural position, the critical inspiratory flow velocity was higher, about 100 ml of air per second. The mean value of the critical expiratory flow was 122 ml of air per second. Air flow in the trachea of most individuals is probably turbulent during the greater part of normal respiratory activity. Calculation of critical flow velocities in the airways by means of Reynolds' formula for smooth cylindrical tubes leads to erroneously high values. Submitted on April 24, 1961
Cardiorespiratory responses during prolonged exercise
Authors: Michael Ernest D. , Hutton Kenneth E. , Horvath Steven M. 
Published: December 2017

Three healthy male subjects 20 years of age were exercised for 2—8 hr riding a bicycle ergometer or walking on a treadmill. Higher heart rates were found with the bicycle rides than with the walking exercises with equivalent oxygen uptakes. The subjects could not work on the bicycle ergometer at oxygen uptakes of 1.8 liters/min for more than 4 hr but could with this uptake walk 8 hr. The results indicated that an 8-hr period of exercise could be completed without undue fatigue whenever the energy cost did not exceed 35% of the maximum oxygen uptake where heart rates, oxygen uptakes, and rectal temperatures remained below 120 beats/min, 1.4 liters/min, and 38 C, respectively. The heart rate appeared to be the important factor for estimating 8-hr work endurance. A rate of 140 beats/min could not be maintained for more than 4 hr or a rate of 160 beats/min for more than 2 hr without extreme fatigue. Submitted on October 26, 1960
Mechanical work of breathing during exercise in trained and untrained subjects
Authors: Milic-Emili G. , Petit J. M. , Deroanne R. 
Published: December 2017

The mechanical work of breathing was measured from simultaneous records of esophageal pressure and tidal volume on seven well trained and seven untrained subjects exercising on a bicycle ergometer. At any given value of pulmonary ventilation, mechanical work of breathing was found to be the same for untrained and trained subjects. At any given value of oxygen uptake, pulmonary ventilation and, accordingly, mechanical work of breathing were found to be smaller in trained than in untrained individuals. Submitted on June 9, 1961
Characteristics of pressure-flow regulation by the kidney
Authors: Schmid Herman E. , Spencer Merrill P. 
Published: December 2017

Pressure-flow relationships in the dog kidney were studied by means of a square wave, noncannulating electromagnetic flowmeter probe placed around the renal artery by way of a retroperitoneal approach. Renal artery pressure was varied by a clamp on the artery and recorded via a needle inserted distal to the probe and clamp. Reductions in artery pressure from control levels demonstrated complete regulation of flow from control level down to 70 mm Hg, incomplete regulation from 50–70 mm Hg, and inability to compensate further below 50 mm Hg. Insignificant regulation was found in the iliac vascular bed by this technique. Recovery time of flow occurred within 5–60 sec following occlusion and was more prolonged at lower levels of artery pressure. The findings of a sharp inflection in the pressure-flow plot at approximately 70 mm Hg and a time course of regulation and recovery pattern varying with the reduced artery pressure suggest an active mechanism controlled by a sensitive feedback system. Submitted on September 18, 1961
Diaphragm activity and thoracoabdominal mechanics during positive pressure breathing
Authors: Agostoni Emilio 
Published: December 2017

The electrical activity of the diaphragm and the mechanical contribution of the thorax and the abdomen through the breathing cycle has been investigated in man during positive pressure breathing (PPB). The electrical activity of the diaphragm persists even at values at which inspiration should be completely passive according to the pressure volume diagram of the thorax and lung. The transdiaphragmatic pressure decreases as the value of PPB increases but is still appreciable at values of PPB at which the inspiration appears to be completely passive by an analysis based on transthoracic pressure measurements alone; the transdiaphragmatic pressure becomes zero only at PPB of about 30 cm H2O. The persistent activity of the diaphragm during PPB is counterbalanced by an activity of the abdominal muscles in excess of that of the expiratory muscles as given by transthoracic pressure measurements. Owing to the persistence of an abdominothoracic pressure gradient, the venous return and therefore the cardiac output should be less reduced than in the case of a passive inspiration. Submitted on September 22, 1961
Breath holding at beginning of exercise
Authors: Cummings E. G. 
Published: December 2017

Men stood astride a moving treadmill belt and at a verbal signal held their breath, jumped on the treadmill belt, and walked or ran at a series of speeds up to 9 mph until the breaking point was reached. Breath-holding time decreased sharply with increasing exercise rates, but began to level off at approximately 30 sec between 6 and 9 mph. Breaking-point alveolar Po2 decreased and Pco2 increased with increasing treadmill speeds. When these two factors were applied in the Otis, Fenn, and Rahn ventilation equation to describe ventilation at the breaking point, the ventilation ratio increased, and it was observed that the men withstood a stronger stimulus to breathe as the work rate increased, even though the breath-holding time remained fairly constant at higher work levels. Apparently at the beginning of work the stimulus to breathe is the combination of a relatively weak neurogenic stimulus and an accumulating chemical stimulus. It is postulated that the constancy of beginning breath-holding times at high work rates may reflect a transport time for the chemical stimulus to reach the receptor area from working muscles via the circulation. Submitted on September 25, 1961
Evaluation of iron stores as limiting high altitude polycythemia
Authors: Hornbein Thomas F. 
Published: December 2017

The total amount of iron available from normal body stores and usual dietary intake might be so small as to limit the rate and magnitude of the polycythemic response to high altitude. To evaluate this problem the influence of iron supplementation on blood hemoglobin concentrations was observed in ten members of a Himalayan expedition during the course of their ascent of a 25,660-ft peak. Half the group received iron supplements in large doses both orally and parenterally; the other five obtained only the iron present in the normal high altitude diet. Hemoglobin concentrations in both groups increased by 33% over 2 months. No significant difference in hemoglobin concentrations between the two groups was noted at any time during the course of the study. It is concluded that normal iron stores plus dietary iron were adequate to meet the needs of increased hemoglobin synthesis at high altitude in the five individuals who received no iron supplementation. Submitted on July 31, 1961
Physical regulation of temperature in Eskimos
Authors: Rennie Donald W. , Covino Benjamin G. , Blair Murray R. , Rodahl K. 
Published: December 2017

Temperature regulation of Eskimos and non-Eskimos, exclusive of shivering, was compared over a range of controlled conditions that produced near-maximal sweating (room temp., 35 C) to maximal cutaneous vasoconstriction (23 C air or 33 C water bath). The Eskimos consistently produced 15-20 kcal/m2/hr more heat at rest. This may or may not be cold adaptation. In air warmer than 28 C their surfeit of heat resulted in higher tissue conductances, warmer skin, and greater sweating. In cooler air and 33 C water, the physical conductance of heat through tissues of the Eskimos remained 60% greater and resulted in warmer skin or a greater fall of rectal temperature. This can be accounted for on physical grounds, since the Eskimos had 1 cm less subcutaneous fat than did non-Eskimos. The value of high metabolism and high tissue conductance to fully clothed Eskimos would appear to be reflex vascular convection of heat to distal extremities, since average skin temperatures under their clothing are comparable to those of unclothed Eskimos in room temperatures exceeding 28 C. Submitted on August 17, 1961
Postural variations in dead space and CO2 gradients breathing air and O2
Authors: Larson C. P. , Severinghaus J. W. 
Published: December 2017

Effects of postural changes on anatomic and physiologic dead space and arterial-alveolar CO2gradients were studied in 11 healthy, adult subjects breathing air and O2. Results indicate that, on moving from the supine to the sitting position, Vads and Vpds increased by corresponding amounts (42 and 37 ml) with no increase in alveolar dead space or volume of lung which is nonperfused. Arterial-alveolar CO2 gradients were unaffected by posture, but more than doubled with O2 breathing, suggesting that O2 may relax the pulmonary vascular bed and diminish perfusion of highest lung segments. Isoproterenol aerosol (0.5%) produced significant bronchodilatation (27 ml increase in Vads), but only small and inconsistent increases in alveolar dead space and CO2 gradients. The PDS/Vt ratio in these subjects while sitting, breathing air, averaged 31 ± 6%, which is higher than the normally accepted value of 30%. As a result, the upper normal limit for PDS/Vt has been increased to 40% in our laboratories. Submitted on January 22, 1962
Cold vasodilatation and cold acclimatization in the hands of British fish filleters
Authors: Nelms J. D. , Soper D. J. G. 
Published: December 2017

The duration of vasoconstriction and magnitude of cold vasodilatation of 11 experienced fish filleters was compared with 9 controls by immersion of the left hand in stirred ice and water mixtures. Vasodilatation occurred significantly earlier in the filleters, whose hand skin temperatures were significantly higher during immersion, in both the initial vasoconstriction and after vasodilatation. Results similar in some respects were obtained by immersion of the hands in water initially at 5 C. Several of the controls fainted and all were distressed, whereas most of the filleters were unaffected by the cold water. The difference is considered to show the characteristics of acclimatization, and the fact that the filleters are accustomed to working with their hands in very cold water is considered to be the stress producing the acclimatization response. Submitted on July 31, 1961
Relation of geometry to certain aspects of hydrodynamics in larger pulmonary arteries
Authors: Fry Donald L. , Patel Dali J. , De Freitas Flavio M. 
Published: December 2017

Pressure-flow relationships in the major pulmonary artery of the dog associated with accelerations imposed on flow by the geometry of vessel walls were evaluated. Assuming irrotational flow, the pressure-flow relationships may be evaluated by numerical substitution of fluid boundary measurements into Bernoulli's equation. Fluid boundary dimensions were obtained from Jeltrate casts of the pulmonary arterial tree in eight dogs. The results indicate that significant pressure differences may occur in the pulmonary artery at peak systolic blood flows due to nonuniformity and curvature of these vessels. Submitted on December 4, 1961
Responses to exercise as related to age and environmental temperature
Authors: Dill D. B. , Consolazio C. F. 
Published: December 2017

The responses of two subjects to exercise were studied after a time lapse of 29 years. Environmental temperatures varied from 0 to 50 C and oxygen consumptions from the resting value to about ten times basal metabolic rate. In DBD, present age 70, the heart rates were about the same in easy and moderate work at temperatures up to 40 C but much higher at 50 C. In FC, present age 50, at all work levels the heart rates were the same up to 20 C, lower at 30 and 40 C, and higher at 50 C. The aerobic capacity of both subjects had declined about one-fourth. Thus the responses to the stress of extreme heat showed little loss, whereas there was considerable loss in the ability to withstand the stress of hard work Submitted on February 19, 1962
Changes in blood gases and acid-base balance in the exercising dog
Authors: Wathen Ronald L. , Rostorfer Howard H. , Robinson Sid , Newton Jerry L. , Bailie Michael D. 
Published: December 2017

Effects of varying rates of treadmill work on blood gases and hydrogen ion concentrations of four healthy young dogs were determined by analyses of blood for O2 and CO2 contents, Po2, Pco2, and pH. Changes in these parameters were also observed during 30-min recovery periods from hard work. Arterial and mixed venous blood samples were obtained simultaneously during work through a polyethylene catheter in the right ventricle and an indwelling needle in an exteriorized carotid artery. Mixed venous O2 content, Po2 and O2 saturation fell with increased work, whereas arterial values showed little or no change. Mixed venous CO2 content, Pco2, and hydrogen ion concentration exhibited little change from resting levels in two dogs but increased significantly in two others during exercise. These values always decreased in the arterial blood during exercise, indicating the presence of respiratory alkalosis. On cessation of exercise, hyperventilation increased the degree of respiratory alkalosis, causing it to be reflected on the venous side of the circulation. Submitted on January 8, 1962
Blood flow in arm and finger during muscle contraction and joint position changes
Authors: Rohter Frank D. , Hyman Chester 
Published: December 2017

Digital pulse and blood flow were measured while subjects squeezed a hand dynamom eter. The pulse wave was obliterated at 25% maximum hand grip, and blood flow was occluded at 45% maximum hand grip. Maximum hand grip did not reduce radial pulse, therefore occlusion occurred at some point distal to the forearm muscles. Changes in blood flow suggest that the superficial palmar arch is occluded first and subsequently the deep palmar arch is arrested. Strong contraction of the biceps abolished the radial pulse, but did not diminish the brachial pulse wave; therefore occlusion must occur between the upper arm and the wrist, probably immediately distal to the elbow where the artery proceeds under the fascia of the biceps. Contracting the pronator teres also obliterated the digital pulse wave. Finally, it is possible to eliminate the digital pulse by rotating the clavicle backward, pressing the artery against the first rib. This was accomplished by horizontal retraction of the upper arm while it was elevated laterally or by simply jamming back the forward and horizontally elevated extremity. Submitted on February 20, 1961
Concurrent measurements of functional residual capacity by three methods
Authors: Tierney Donald F. , Nadel Jay A. 
Published: December 2017

We made concurrent measurements of the functional residual capacity (FRC) with the body plethysmograph (thoracic gas volume) and by 7-min and prolonged open-circuit nitrogen dilution methods (communicating gas volume). The mean difference between the 7-min communicating gas volume and the thoracic gas volume in 13 healthy subjects was only 0.13 liters. The thoracic gas volume averaged 0.99 liters larger than the communicating gas volume after 7 min of O2 breathing in 13 patients with emphysema. The communicating gas volume at 12–18 min was the same as the thoracic gas volume in 11 of 13 patients but was smaller in the other 2. When the thoracic gas volume was used to measure FRC, the total lung capacity averaged 142% of predicted normal in 13 patients with emphysema. Submitted on January 4, 1962
Influence of carbon dioxide and hyperventilation on cardiac output in man
Authors: McGregor M. , Donevan R. E. , Anderson N. M. 
Published: December 2017

The effect of changes in ventilation and carbon dioxide tension on cardiac output was studied in seven normal human subjects in the supine posture using a dye dilution method. Voluntary hyperventilation of room air with resultant hypocapnia invariably produced an increase in cardiac output (mean, 38 ml blood/ liter increase in ventilation). Voluntary hyperventilation with maintenance of CO2 tension at near normal levels resulted in a smaller increase in cardiac output (mean, 15 ml/liter). Hyperventilation produced by the inhalation of 8.4% CO2 produced no change in cardiac output within the first 2 min but an increase thereafter. The response of the cardiac output to hyperventilation is thus largely determined by the carbon dioxide content of the inspirate. The manner in which this takes place is uncertain. The higher cardiac output response at 2 min with hypocapnia may be partly the result of respiratory alkalosis. It might also be related to the increase in respiratory mechanical work per liter ventilation associated with the fall in CO2. The reason for the late rise of cardiac output with hypercapnia is unknown. Submitted on May 14, 1962
Some effects of apneic underwater diving on blood gases, lactate, and pressure in man
Authors: Olsen C. Robert , Fanestil Darrell D. , Scholander Per F. 
Published: December 2017

Five men of outstanding diving ability performed apneic underwater dives in a specially fitted tank. The divers hyperventilated to extreme degrees of hypocapnia before submerging, and their arterial blood carbon dioxide tensions rarely rose above normal levels during a dive. Arterial blood oxygen content was 15.5 vol % or above at the end of two 3-min resting dives and of three 1.5-min exercise dives. Blood lactate concentrations increased during the latter half of exercise dives and reached peak values after surfacing. A rise in arterial blood pressure began by 10 sec in each dive and persisted, coincident with a falling heart rate, to the end of the dive. The rate of blood pressure rise was greater during a dive in water of 26 C than with breath holding by the same subject out of water. Some differences between the adaptations of diving men and of other diving mammals are briefly discussed. Submitted on April 2, 196
Physical insulation of Korean diving women
Authors: Rennie D. W. , Covino B. G. , Howell B. J. , Song S. H. , Kang B. S. , Hong S. K. 
Published: December 2017

Human cold adaptation was studied by comparing maximal body insulation [ I = (rectal temp. – skin temp.) /rate of skin heat loss] of Korean diving women to insulation of Korean nondiving men and women and American men and women. Appropriate measurements were made during immersion in a constant-temperature bath cool enough to induce maximal cutaneous vasoconstriction without shivering. Subcutaneous fat was estimated from measurements of skin-fold thickness. Within each racial group there is a significant regression of I on fat thickness. Koreans had a significantly greater I than Americans of comparable fat thickness. Korean diving women had the same I as nondivers of comparable fat thickness. Korean women had significantly greater I than Korean men due, we believe, to thicker subcutaneous fat. This may be the reason why women and not men engage in diving. The only evidence for cold adaptation among diving women was their ability to withstand colder water immersion without shivering. Submitted on March 22, 1962
Effect of serum albumin infusion on lipid mobilization in man
Authors: Bogdonoff Morton D. , Linhart Joseph W. , Estes E. Harvey 
Published: December 2017

Serial plasma free fatty acid (FFA), cholesterol, and triglyceride levels were measured in 5 normal human subjects and in 11 hypoalbuminemic patients after infusion of norepinephrine with and without prior infusion of 50 g of serum albumin. In the hypoalbuminemic patients the peak response in FFA level to norepinephrine was diminished; after albumin infusion the peak rise of FFA level to norepinephrine was enhanced in both the normal and hypoalbuminemic individuals. Alterations in serum triglyceride and cholesterol concentrations that followed albumin infusion could be accounted for by the alteration in plasma volume that also occurred. The diminished FFA response in hypoalbuminemic patients was interpreted as indicating that norepinephrine-induced fat mobilization in man is dependent on the concentration of serum albumin, and that the defect in fat mobilization in hypoalbuminemia may be, in part, related to the alterations in cholesterol and triglyceride metabolism that are characteristic of hypoalbuminemia. Submitted on April 20, 1962