bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual levels and biochemical changes after ventilation with perfluorinated liquid
Authors: Calderwood H. W. , Ruiz B. C. , Tham M. K. , Modell J. H. , Saga S. A. , Hood C. I.
Published: December 2017

Twenty-three beagle dogs were ventilated with perfluorinated liquid, perfluoro-1-isopropoxy-hexane (Caroxin-F) for 1 h and were reconverted to gaseous breathing. Hematologic and biochemical changes were studied in five dogs for 1 yr and the remaining animals were followed for evidence of retained Caroxin-F for up to 3 yr. We found that the dogs could be ventilated with liquid Caroxin-F and returned to spontaneous breathing of gaseous oxygen with normal blood gas exchange within 24–72 h. Serum alkaline phosphatase, serum cholesterol, and white blood cell count increased with liquid ventilation but returned to normal in less than 1 wk. Trace amounts of Caroxin-F were detected by chromatography in all tissues studied for the entire 3-yr period. The highest levels of Caroxin-F were found in the lungs and associated lymph nodes. No histologic evidence of the presence of Caroxin-F was seen except for local accumulations of vacuolated macrophages in the lungs and associated lymph nodes. We conclude that Caroxin-F can be breathed without residual deleterious effects, even though trace amounts remained for at least 3 yr.
Relative contributions of rib cage and abdomen to breathing in normal subjects
Authors: Sharp J. T. , Goldberg N. B. , Druz W. S. , Danon J.
Published: December 2017

By use of the method of Konno and Mead and the respiratory magnetometer, the partition of respired gas volumes into rib cage and diaphragm-abdomen components was accomplished in 81 normal subjects including 32 young and middle-aged men, 29 young and middle-aged women, and 20 elderly men. Studied were isovolume maneuvers and the relaxation configuration over the inspiratory capacity range, quiet tidal breathing, increased amplitudes of slow breathing, rapid inspirations and expirations, and both quiet and forceful phonation. No major differences were noted between men and women or between the young and the elderly during any respiratory acts. During quiet breathing most normal subjects are abdominal breathers when supine and thoracic breathers when upright. Rapid respiratory maneuvers were accomplished mostly through rib cage displacement suggesting that rib cage muscles are capable of more rapid action than diaphragm and abdominal muscles. Data from deep breathing and rapid maneuvers supported the view that abdominal and rib cage muscles often act to optimize the mechanical (length-tension) advantage of the diaphragm.
Localization of the effective thermosensitive site in the preoptic region of the ox
Authors: Calvert D. T. , Findlay J. D.
Published: December 2017

These studies were carried out using chronically implanted thermode probes in conscious oxen at 15 degrees C air temperature. The probes were perfused with water either 4 degrees C above or 5 degrees C below resiting hypothalamic temperature and the thermoregulatory response measured by the change in auditory meatal temperature during the perfusion periods of 25 or 40 min duration, respectively. The anatomical position of the probes was known relative to the third cerebral ventricle in each animal. The thermosensitive area of the ox anterior hypothalamic/preoptic region was shown to be highly localized in a position corresponding to the posterior part of the area preoptica. The same area was responsible for both warm and cold sensitivity, the warm sensitivity being approximately three times greater than the cold.
Arterial pressure contour analysis for estimating human vascular properties
Authors: Watt T. B. , Burrus C. S.
Published: December 2017

The form of an arterial blood pressure curve during the diastolic portion of the cardiac cycle was here employed to identify parameters in a third-order model of the vascular system. Calculated elastic and intertial characteristics of this fitted model then became clinically accessible indices of corresponding real vascular properties. This technique incurred no risk and little discomfort for the patient. Tested in theory, in animal experimentation, and in human observations, our procedure utilized a Gauss-Newton algorithm via digital computer to provide rapid model solutions from different starting values, from multiple measurements sites, and from normal or diseased patients. Model parameters thus determined defined ranges of normal variation and suggested a less compliant arterial bed in hypertensive than in normotensive patients.
Aerosol penetrance: a sensitive index of peripheral airways obstruction
Authors: Dolovich M. B. , Sanchis J. , Rossman C. , Newhouse M. T.
Published: December 2017

Early injury of the small airways has been demonstrated in asymptomatic smokers. Ventilatory tests including the maximum midexpiratory flow rate and closing volume have been useful in clinical detection of small airways disease in symptomatic subjects. In the present study, airway “obstruction” was assessed aerodynamically by gamma camera measurements of chest radioactivity following the inhalation of 131I-labeled aerosol (aerodynamic mass median diameter 3 mum). Studies were performed in normal subjects, asymptomatic smokers, and patients with chronic obstructive lung disease. An aerosol penetrance index (AeP) was devised from determinations which involved 1) an analysis of central (inner zone) and peripheral (outer zone) deposition of aerosol in the lung and 2) a ratio of initial counts to 24-h counts in the periphery (outer zone) of the lung. AeP values were 41.5 +/- 11.5 for the normal group, 20.9 +/- 7.6 for the smoker group, and 10.6 +/- 5.2 for the subjects with chronic obstructive airway disease. AeP was significantly reduced in the smokers indicating that the AeP is a sensitive index of early peripheral airways obstruction.
Reference sample method for cardiac output and regional blood flow determinations in the rat
Authors: Malik A. B. , Kaplan J. E. , Saba T. M.
Published: December 2017

The reference sample method was used for simultaneous determinations of cardiac output and regional blood flows in conscious rats. Microspheres (15 +/- 5 mum in diam) labeled with strontium-85 were injected into the left ventricle and known volumes of reference sample were withdrawn from peripheral arteries. The calculated cardiac output measurements agreed with the previously reported values in rats. The percent distribution of the cardiac output to the brain, intestinal bed, and lungs were different from the reported values obtained in the rats using larger spheres. These differences may be related to the use of smaller spheres and to differences in the preparation. The absolute regional flows to various organs expressed in terms of milliliters per minute per gram tissue weight were also determined. The results indicate that the reference sample method can be applied to smaller mammals for determinations of regional flows and cardiac output.
Effects of continuous positive-pressure ventilation in experimental pulmonary edema
Authors: Hopewell P. C. , Murray J. F.
Published: December 2017

We compared the effects of continuous positive-pressure ventilation (CPPV), using 10 cmH2O positive end-expiratory pressure (PEEP), with intermittent positive-pressure ventilation (IPPV), on pulmonary extravascular water volume (PEWV) and lung function in dogs with pulmonary edema caused by elevated left atrial pressure and decreased colloid osmotic pressure. The PEWV was measured by gravimetric and double-isotope indicator dilution methods. Animals with high (22–33 mmHg), moderately elevated (12–20 mmHg), and normal (3–11 mmHg) left atrial pressures (Pla) were studied. The PEWV by both methods was significantly increased in the high and moderate Pla groups, the former greater than the latter (P less than 0.05). There was no difference in the PEWV between animals receiving CPPV and those receiving IPPV in both the high and moderately elevated Pla groups. However, in animals with high Pla, the Pao2 was significantly better maintained and the inflation pressure required to deliver a tidal volume of 12 ml/kg was significantly less with the use of CPPV than with IPPV. We conclude that in pulmonary edema associated with high Pla, PEEP does not reduce PEWV but does improve pulmonary function.
Maximum exercise tests on "postcoronary" patients
Authors: Kavanagh T. , Shephard R. J.
Published: December 2017

The maximum oxygen intake has been measured directly (uphill treadmill walking) in 36 patients following recovery from myocardial infarction. These were selected as follows: 15 consecutive new entrants to an exercise program that is currently accepting about one-sixth of the total reported myocardial infarction hospital admissions in metropolitan Toronto (group A), 12 patients not responding well to training (group B), and 9 patients now running substantial distances (group C). The only clinical complications were two episodes of ventricular tachycardia. Twenty patients reached an oxygen plateau, and in group C, the maximum heart rate (170/min) reached Scandinavian norms, with a maximum oxygen intake (2.63 +/- 0.35 1/min STPD, 36.9 +/- 4.8 ml/kg-min STPD) as in healthy men of the same age. The rate of adaptation to a progressive submaximum test was such that comparable Astrand nomogram predictions of VO2max were obtained from data in the 3rd and 5th min at the third load. Predictions generally agreed closely with directly measured values. It may be concluded that in patients who have recovered sufficiently to enter an exercise rehabilitation program 1) predictions of VO2max have about the same accuracy (+/-10) as in healthy subjects, and 2) direct measurements can often be pursued to an “oxygen plateau” without due risk.
Prostaglandin synthetase inhibitors do not decrease hypoxic pulmonary vasoconstriction
Authors: Weir E. K. , McMurtry I. F. , Tucker A. , Reeves J. T. , Grover R. F.
Published: December 2017

Prostaglandins are naturally occurring substances with powerful vasoactive effects that are released from tissues during hypoxia or ischemia. Several workers have suggested that a prostaglandin may help to mediate the pulmonary vascular pressor response to alveolar hypoxia. To investigate this possibility, we have measured the pressor responses to hypoxia before and after prostaglandin synthesis antagonism with meclofenamate in eight anesthetized dogs, two groups of awake calves (n=10 and =5), and nine isolated, perfused rat lungs. In addition, synthesis was inhibited by the use of indomethacin in nine additional dogs. The stability of the pulmonary vascular response to repeated hypoxic challenges was demonstrated in nine other dogs. In each species and with both prostaglandin antagonists, the pulmonary pressorresponses to hypoxia were significantly increased rather than reduced. We conclude that prostaglandins do not mediate the pulmonary vasoconstriction caused by hypoxia. The consistent increase observed suggests that hypoxic vasoconstriction stimulates prostaglandin synthesis, the net effect of which is pulmonary vasodilatation which opposes the constriction.
Effects of hypercapnia on uterine and umbilical circulations in conscious pregnant sheep
Authors: Walker A. M. , Oakes G. K. , Ehrenkranz R. , McLaughlin M. , Chez R. A.
Published: December 2017

Changes in the uterine and umbilical circulations during induced hypercapnia were studied in nine unanesthetized near-term pregnant sheep. Blood flows were measured with electromagnetic flow transducers and arterial pressures with vascular catheters implanted under anesthesia 2–16 days prior to experiments. Hypercapnia was induced in the fetus alone by giving acetazolamide iv to the fetus, 100–200 mg/kg. Mean fetal arterial Pco2 increased from49.5 to 63.4 mmHg but no significant changes in umbilical blood flowoccurred. Stepwise increases in both maternal and fetal arterial Pco2 were induced by increasing maternal inspired CO2 concentration to a maximum of 12%. Nodignificant changes occurred in uterine or umbilical circulations until hypercapnia was severe (maternal arterial Pco2 greater than 60 mmHg, fetal arterial Pco2 greater than 70 mmHg). With severe hypercapnia uterine vascular resistance increased significantly and uterine blood flow decreased despitean increase in maternal arterial pressure; fetal arterial pressure and umbilical blood flow increased significantly, but umbilical vascular resistancedid not. We conclude that hypercapnia in conscious pregnant sheep is associated with significant changes in uterine and umbilical circulations, but only when hypercapnia is severe. Carbon dioxide is unlikely to be a factor innormal physiological regulation of the uteroplacental circulation in this species.
Influence of carbon monoxide on hemoglobin-oxygen binding
Authors: Hlastala M. P. , McKenna H. P. , Franada R. L. , Detter J. C.
Published: December 2017

The oxygen dissociation curve and Bohr effect were measured in normal whole blood as a function of carboxyhemoglobin concentration [HbCO]. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HCl at constant PCO2 (fixed acid Bohr effect). As [HbCO] varied through the range of 2, 25, 50, and 75%, P50 was 26.3, 18.0, 11.6, and 6.5 mmHg, respectively. CO2 Bohr effect was highest at low oxygen saturations. This effect did not change as [HbCO] was increased. However, as [HbCO] was increased from 2 to 75%, the fixed acid Bohr factor increased in magnitude from -0.20 to -0.80 at very low oxygen saturations. The effect of molecular CO2 binding (carbamino) on oxygen affinity was eliminated at high [HbCO]. These results are consistent with the initial binding of O2 or CO to thealpha-chain of hemoglobin. The results also suggest that heme-heme interaction is different for oxygen than for carbon monoxide.
Measurement of VO2, VCO2, and evaporative water loss with a flow-through mask
Authors: Withers P. C.
Published: December 2017

Equations for the calculation of VO2, VCO2, and evaporative water loss were derived for use of a paramagnetic gas analyzer with a flow-through respirometry system and an open or closed mask. The magnitude of errors involved in the determination of VO2 with no CO2 absorbent are small (+/-3%) but may be greater if no H2O absorbent is used, unless an appropriate correctionis made for evaporative water loss. Data collected for hummingbirds (Selasphorus sasin) and monitor lizards (Varanus gouldii) indicate the validity ofthe technics described for the measurement of RQ and evaporative water lossand demonstrate the use of paramagnetic gas analyzers in monitoring respiratory patterns.
Causes of high blood O2 affinity of animals living at high altitude
Authors: Petschow D. , Wurdinger I. , Baumann R. , Duhm J. , Braunitzer G. , Bauer C.
Published: December 2017

We have measured the partial pressure of O2 at 50% saturation (P50) and the concentration of various phosphate compounds in the erythrocytes of the bar-headed goose and the guanaco to establish the cause of the high blood O2 affinity in animals who normally reside at high altitude. The same data were obtained in the blood of two goose species, that live at sea level, and in human blood. At standard conditions (pH 7.4, PCO2 40 Torr, 37 degrees C), P50 was 29.7 Torr in the blood of the bar-headed goose and was about 10 Torr higher in the goose species living at sea level. Since the concentration of organic phosphates was not markedly different in the erythrocytes of either goose species we conclude that the hemoglobin of the bar-headed goose reacts more weakly with organic phosphates, which can also be inferred from studies on purified hemoglobin solutions. Likewise, the low P50 of guanaco blood in comparison with human blood can be explained by a reduced interaction of 2,3-bisphosphoglycerate of guanaco hemoglobin compared to the human pigment.
Regulation of arousal from hibernation by temperature in three species of Citellus
Authors: Twente J. W. , Twente J. , Moy R. M.
Published: December 2017

The frequency of arousal from periods of hibernation of Citellus lateralis, C. tridecemlineatus, and C. columbianus was demonstrated to be regulated by environmental (and therefore body) temperature over the range of 2–12 degrees C in a log-linear relationship. The slopes of the lines of regression for all three species were not significantly different from one another. Durations of the periods of hibernation for the considerably larger C. columbianus, however, were significantly longer at all levels of temperature than those for the similar-sized C. lateralis and C. tridecemlineatus. The mechanism(s) regulating the duration of the period of hibernation was considered to be concerned with some aspect of metabolism and probably the same for all three species.
Oxygen delivery and uptake in dogs during anemic and hypoxic hypoxia
Authors: Cain S. M.
Published: December 2017

Three groups of dogs were anesthetized, paralyzed, and ventilated at constant rates with the spleen clamped. Two groups were isovolemically hemodiluted with warm dextran and plasma to hematocrits just above and below that at which O2 uptake (VO2) could not be maintained at preanemic levels. One of these groups was given propranolol to reduce the cardiac output response to anemia. The third group was ventilated on a low O2 gas mixture to decrease oxygen uptake. VO2 was thus limited at a high-delivery O2 pressure (PO2) in anemia and a low-delivery PO2 in hypoxic hypoxia. VO2 was reduced at a mixed venous PO2 of 45 Torr in anemia and at 17 Torr in hypoxic hypoxia. VO2, mixed venous PO2, and O2 delivery decreased precipitously at hematocrits below 10%. Once VO2 was limited by O2 availability, a single linear relationship (r = 0.91) was found for percent VO2 as a function of total O2 delivery (cardiac output X arterial O2 content) during both anemic and hypoxic hypoxia. The critical value for O2 delivery was 9.8 ml/kg-min. When O2 supply became limiting, VO2 apparently was not diffusion limited because it was more dependent on volume delivery rates than on delivery PO2.
Linear increase in aerobic power induced by a strenuous program of endurance exercise
Authors: Hickson R. C. , Bomze H. A. , Holloszy J. O.
Published: December 2017

Eight subjects exercised for 40 min/day, 6 days/wk for 10 wk. For 3 days/wk they performed six 5-min intervals of bicycling on an ergometer against a resistance that elicited VO2 max, separated by 2-min intervals of exercise requiring 50–60% of Vo2 max. On the alternate 3 days, they ran as far as they could in 40 min. Our purpose was to obtain information regarding the time course and magnitude of the increase in Vo2 max and endurance that occur in response to strenuous exercise when the training stimulus is kept approximately constant relative to maximum aerobic capacity. Average Vo2 max increased 5% (P less than 0.05) during the 1st wk. Endurance, Vo2 max, and time to attainment of peak heart rate all increased linearly during the 10 wk. The average weekly increase in Vo2 max was 0.12 l/min. The total increase in Vo2 max averaged 16.8 ml/kg per min (44%). Four of the eight subjects attained Vo2 max levels approaching or exceeding 60 ml/kg per min. It appears from these results that aerobic work capacity can increase more rapidly and to a greater extent in response to training than has generally been thought.
Cardiovascular, respiratory, and metabolic adjustments to exercise in dogs
Authors: Wagner J. A. , Horvath S. M. , Dahms T. E.
Published: December 2017

Cardiovascular and metabolic parameters were studied in dogs anesthetized with pentobarbital sodium, and while awake resting or exercising for 30 min at either 6.4 km/h, 10% grade (32% VO2 max) or 8.0 km/h, 16% grade (50% VO2 max). The anesthetized dogs had lower cardiac outputs, stroke volumes, arterial-mixed venous oxygen differences, oxygen uptakes, rectal temperatures, and higher diastolic and mean arterial pressures than awake resting dogs. Heart rates and arterial systolic pressures were similar in the two conditions. The increased oxygen uptakes during exercise were associated with approximately equal percentage increments in cardiac outputs and oxygen extractions. Cardiac output increases during exercise were largely due to increases in heart rates. Arterial CO2 tension and CO2 contents as well as venous O2 and CO2 gas tensions and contents declined, and pH and rectal temperatures increased during exercise. The dogs became alkalotic during exercise. Elevated central body temperatures appeared to be the major factor controlling respiration.
Combined effects of breathing resistance and hyperoxia on aerobic work tolerance
Authors: Dressendorfer R. H. , Wade C. E. , Bernauer E. M.
Published: December 2017

Effects of three curvilinear inspiratory resistances (R1, R2, R3) on the cardiorespiratory responses of seven well-trained men during incremental cycling tests to exhaustion were studied by comparison to the low resistance R0 (at 1 l/s, R0 = 0.2; R3 = 6.5 cmH2O-s/l). Submaximal VO2 and the gas exchange anaerobic threshold (AT) were not affected by increasing resistance. Although maximal work rates were not significantly changed, highly significant reductions were observed for VE (R0 = 166.3; R3 = 99.7 l/min BTPS), VO2 max (R0 = 4,26; R3 = 3.74 l/min), HR (R0 = 185; R3 = 176 beats/min), and endurance (R0 = 17.3; R3 = 15.5 min) suggesting that aerobic work tolerance was dependent on ventilatory capacity. In additional tests removal of R3 at exhaustion abruptly increased VE and VO2, and permitted work to continue. Ventilation and work tolerance were therefore limited by R3 before the legs fatigued. Breathing 35% O2 against R3 produced significant, although small, increases in AT, VO2 max, peak HR, and endurance while decreasing the hyperventilatory response to work above AT. Thus, aerobic work tolerance reduced with high inspiratory resistance was partly restored by moderate hyperoxia, apparently because the ventilatory limit was delayed.
Decrease of maximum work performance following ozone exposure
Authors: Folinsbee L. J. , Silverman F. , Shepard R. J.
Published: December 2017

A bicycle ergometer was used to measure maximum exercise oxygen consumption following 2 h of intermittent exercise in an environmental chamber ventilated with air (FA test) or filtered air plus 0.75 ppm ozone (PO test). Thirteen adult males performed both tests according to a random sequence. The maximum attained VO2 declined 10% (P less than 0.01), maximum attained work load was reduced by 10% (P less than 0.01), maximum ventilation decreased 16% (P less than 0.01), and maximum heart rate dropped 6% (P less than 0.05) in the PO test. At the highest common work load, heart rate and oxygen consumption were similar and ventilation was slightly higher (P less than 0.05); however, frequency of respiration increased 45% (P less than 0.01) and tidal voluem fell by 29% (P less than 0.01) following ozone exposure. During maximum exercise, the respiratory frequency was similar in both tests, but tidal volume was 21% lower (P less than 0.01) in PO experiments. Decreases in vital capacity and FEV1.0 as well as cough and chest discomfort were also noted following ozone exposure. We conclude that the reduction of maximum attained VO2 is a consequence of ventilatory limitation of maximum effort, probably related to respiratory discomfort.
Skin, preoptic, and core temperatures influence behavioral thermoregulation
Authors: Adair E. R.
Published: December 2017

Squirrel monkeys (Saimiri sciureus) will learn to regulate their chamber air temperature (Ta) behaviorally by selecting between two air temperatures, 10 and 50 degrees C. When transient (10-min) displacements of local preoptic temperature (Tpo) are made around neutral, via water-perfused thermodes, changes in Ta selected are linear and inversely proportional to the Tpo displacement. The same result occurred in the present study when 10-min Tpo displacements were made around a clamped (36--41 degrees C) Tpo. The higher the clamped Tpo level, the steeper the linear functions relating behavioral response to Tpo transients. This change of gain was manifested in behavioral adjustments of Ta or skin temperature. The data showed that the temperature of the extrahypothalamic body core (measured rectally) was driven by the clamped Tpo to a nonneutral level. When this level was maintained stable during the Tpo transients, core temperature was shown to be a multiplicative factor governing the gain of the behavioral effector responses.
Effect of histamine on electrical and ion transport properties of tracheal epithelium
Authors: Marin M. G. , Davis B. , Nadel J. A.
Published: December 2017

Previously we showed that the active transport of Cl-toward and Na+ away from the tracheal lumen creates an electrical potential difference (lumen negative) across the canine tracheal epithelium in vitro. The present study examined the effect of histamine on the electrical properties and ion transport of the canine tracheal epithelium in vitro. In six pairs of membranes, under short-circuit conditions, histamine (10(-4) M) significantly increased the net flux toward the lumen of Cl- from 1.7 +- 0.5 SE to 2.4 +- 0.6 microneq/cm2-h and Na+ from -0.4 +- 0.3 to 0.2 +- 0.3 microneq/cm2-h. The response to histamine was inhibited by diphenhydramine (10(-6) M), an H1-receptor antagonist, but not by burimamide (10(-4) M), an H2-receptor antagonist. These results are consistent with the hypothesis that an H1-type receptor mediates the increase of ion flux toward the lumen due to histamine. Increased ion flux toward the lumen may mediate water secretion into the airway lumen and have important effects on the physical properties of the liquid through which the respiratory cilia beat.
Assessment of maximal aerobic power in specifically trained athletes
Authors: Stromme S. B. , Ingjer F. , Meen H. D.
Published: December 2017

Maximal aerobic power of 37 athletes (14 females and ten male cross-country skiers, eight male rowers and five male cyclists) was determined during uphill running on the treadmill and during maximal performance of their specific sport activity. For the skiers a significantly (P less than 0.005) higher VO2max was found during uphill skiing than during running, the differences being 2.9 and 3.1% for the females and males, respectively. The rowers and cyclists obtained a difference of 4.2 and 5.6%, respectively (P less than 0.01). The largest individual differences between the two test procedures were 12.2, 5.4, 14.3, and 7.9% for female and male cross-country skiers, rowers, and cyclists, respectively. It is concluded that in evaluation of maximal aerobic power of atheletes, it becomes important to select a work situation which allows optimal use of the specifically trained muscle fibres. This means that the test preferably should be identical with the subjects' specific sport activity, under the assumption that a reasonably large muscle mass is engaged during the performance.
Skin blood flow and sweating changes following exercise training and heat acclimation
Authors: Roberts M. F. , Wenger C. B. , Stolwijk J. A. , Nadel E. R.
Published: December 2017

Eight subjects underwent an exercise training program (10 days at 75% VO2max for 1 h/day at 25 degrees C db/13 degrees C wb) and a heat-acclimation program (10 days at 50% VO2max for 1 h/day at 35 degrees C db/32 degrees C wb). The relations of chest sweat rate and of forearm blood flow to internal temperature were determined for each subject at a 25 degrees C ambient temperature before training, between training and acclimation, and following acclimation. Training shifted the vasodilation and sweating thresholds toward lower internal temperatures, and acclimation further lowered these thresholds. All threshold shifts were statistically significant (P less than 0.05). Training and acclimation both appeared to increase the slope of the sweating relation, but these effects were not statistically significant. Changes in the slope of the blood flow relation were small and inconsistent. Since arm blood flow is higher at any given internal temperature after acclimation, the lower blood flow which is reported to accompany heat acclimation must result from the lower body temperatures.
A new apparatus for the accurate measurement of airway resistance in infancy
Authors: Stocks J. , Levy N. M. , Godfrey S.
Published: December 2017

A new heated rebreathing system has been developed for the measurement of thoracic gas volume (TGV) and airway resistance (Raw) in infants by the plethysmographic technique. The apparatus has a linear response to flow rates between 0–160 ml-s-1, a dead space of 12 ml and a resistance of 5 cmH2O–1–1-S-1 at a flow rate of 60 ml-s-1. The inclusion of pneumatically operated valves in the apparatus is a major improvement over previous methods of occlusion for TGV measurements. The infant is allowed to rebreathe saturated gas at body temperature through the heated system, thus overcoming a potential source of error when measuring Raw in infants. Using this apparatus, the average coefficient of variation was 3.7% for TGV and 5.9% for Raw.
Alcohol, respiration, skin and body temperature during cold water immersion
Authors: Martin S. , Diewold R. J. , Cooper K. E.
Published: December 2017

Subjects who had not been exercising, were immersed for 20 min in water at 13 degrees C after ingestion of alcohol. During the immersion period, total ventilation, end-tidal PCO2, rectal temperature, aural temperature, and mean skin temperature were recorded. Control experiments were carried out at the same water temperature. Blood samples (3 ml), taken immediately before the immersion period, were analyzed by gas liquid chromatography. The mean blood alcohol level was 90+/-11.2 mg-(100 ml)-1. There was no significant difference in ventilatory responses, rectal temperatures, aural temperatures, or mean skin temperatures achieved during the two cold water immersions. It would appear that for a 20-min immersion at 13 degrees C, relatively high blood alcohol levels do not affect ventilatory responses or increase body heat losses.
Rebreathing pulmonary capillary and tissue volume in normals after saline infusion
Authors: Farney R. J. , Morris A. H. , Gardner R. M. , Armstrong J. D.
Published: December 2017

A rebreathing technique was utilized to assess changes in diffusing capacity (DCO), pulmonary capillary blood volume (Vc), pulmonary parenchymal tissue volume (Vt), and cardiac output (Qc), after infusion of 2 liters of 0.9% saline intravenously in 13–25 min in five healthy subjects. Blood hemoglobin concentration decreased an average of 17%. Vc increased strikingly in all five subjects. No significant changes in Vt, or in Vt per unit lung volume were observed. Radiographic evidence of interstitial pulmonary edema was present in four of the five subjects. Radiographic total lung capacity was reduced significantly in four of the five subjects. Significant reductions in forced vital capacity (FVC), forced expiratory volume in 1.0 and 3.0 s, and mean forced expiratory flow during the middle half of the FVC occurred in three of the five subjects. No dyspnea, cough, or physical examination abnormalities of lungs or heart occurred. This noninvasive, ventilation-limited, rebreathing technique appears capable of detecting early changes in pulmonary congestion, at a time when definitive radiographic changes and changes in the physical examination are absent. It appears capable of detecting the increase in Vc associated with hypervolemia in man.
Correlation between ventilatory and cerebrovascular responses to inhalation of CO
Authors: Doblar D. D. , Santiago T. V. , Edelman N. H.
Published: December 2017

To study the determinants of carbon monoxide (CO) induced hyperpnea simultaneous measurements were made of carboxyhemoglobin level in arterial blood (HbCO), ventilation (VE), cerebral blood flow (CBF), O2 delivery to the brain (CBF X O2 content of arterial blood), O2 consumption of the brain (CMRO2), and O2 tension in cerebral venous blood (PVO2) during inhalation of 1% CO in 40% O2 by six unanesthetized goats. HbCO increased to 65% in 10 min; VE remained constant until a HbCO level of approximately 50% was reached and then increased abruptly; CBF increased progressively; O2 delivery to the brain and CMRO2 decreased somewhat with CO inhalation; these decreases reached statistical significance at a HbCO level of 30–40% whereupon the rate of decline with respect to HbCO level increased substantially; and PVO2 decreased progressively from an average of from 31 to 14.6 Torr and averaged 19.2 Torr when hyperpnea was manifest. When considered in the light of previous studies which indicate that CO-induced hyperpnea is not caused by stimulation of the carotid bodies, these data suggest that this phenomenon is related to brain hypoxia. Calculations of brain tissue O2 tension with the Krogh equation support this contention.
Quantitative analysis of the front crawl in men and women
Authors: Pendergast D. R. , Di Prampero P. E. , Craig A. B. , Wilson D. R. , Rennie D. W.
Published: December 2017

Body drag, D, and the overall mechanical efficiency of swimming, e, were measured from the relationship between extra oxygen consumption and extra drag loads in 42 male and 22 female competitive swimmers using the front crawl at speeds ranging from 0.4 to 1.2 m/s. D increased from 3.4 (1.9) kg at 0.5 m/s to 8.2 (7.0) kg at 1.2 m/s, with D of women (in brackets) being significantly less (P less than 0.05) than that of men. Mechanical efficiency increased from 2.9% at 0.5 m/s to 7.4% at 1.2 m/s for men, the values for women being somewhat greater than those for men. The ratio, D/e was shown to be identical to the directly measured energy cost of swimming one unit distance, V02/d, and was independent of the velocity up to 1.2 m/s. It averaged 52 and 37 l/km for men and women respectively (P less than 0.05). When corrected for body surface area the values were 27 and 22 l/km-m2 for men and women, respectively (P less than 0.05). The underwater torque, T, a measure of the tendency of the feet to sink, was 1.44 kg-m for men and 0.70 kg-m for women (P less than 0.05). VO2/d increased linearly with T for both men and women of similar competitive experience. However, the proportionality constant delta VO2/d-delta T was significantly less for competitive than noncompetitive swimmers. The analysis of the relationship VO2/d vs. T provides a valuable approach to the understanding of the energetics of swimming.
Airway geometry by analysis of acoustic pulse response measurements
Authors: Jackson A. C. , Butler J. P. , Millet E. J. , Hoppin F. G. , Dawson S. V.
Published: December 2017

Serial distribution of airway properties determines in part the response of the lung to high frequency oscillations. We measured the response of excised dog lungs and lobes between 156 and 10,000 Hz and determined the area-distance function of the acoustically equivalent structure having rigid walls, regular branching, and negligible internal losses. The utility of this techique was tested by determining the effects of air trapping, removal of pleura from a dried lung, central airway smooth muscle tone. A strong correlation was found between relative changes in equivalent acoustic area and relative area changes measured radiographically in individual airways at corresponding distances. We conclude that despite departures of the properties of the real lung from the characteristics of the acoustically equivalent structure, changes in the area-distance function computed by this technique provide reasonable estimates of the magnitude and serial distribution of actual changes in airway cross-sectional area.
Effects of elevated plasma FFA and insulin on muscle glycogen usage during exercise
Authors: Costill D. L. , Coyle E. , Dalsky G. , Evans W. , Fink W. , Hoopes D.
Published: December 2017

Seven men were studied during 30 min of treadmill exercise (approximately 70% VO2 max) to determine the effects of increased availability of plasma free fatty acids (FFA) and elevated plasma insulin on the utilization of muscle glycogen. This elevation of plasma FFA (1.01 mmol/1) with heparin (2,000 units) decreased the rate of muscle glycogen depletion by 40% as compared to the control experiment (FFA = 0.21 mmol/1). The ingestion of 75 g of glucose 45 min before exercise produced a 3.3-fold increase in plasma insulin and a 38% rise in plasma glucose at 0 min of exercise. Subsequent exercise increased muscle glycogen utilization and total carbohydrate (CHO) oxidation 17 and 13%, respectively, when compared to the control trial. This elevation of plasma insulin produced hypoglycemia (less than 3.5 mmol/1) in most subjects throughout the exercise. These data illustrate the regulatory influence of both plasma insulin and FFA on the rate of CHO usage during prolonged severe muscular activity.
An electromyographic index for localized muscle fatigue
Authors: Lindstrom L. , Kadefors R. , Petersen I.
Published: December 2017

A new method for objective quantification of localized muscle fatigue is described. The method is based on power spectrum analysis of myoelectric signals obtained from the fatigued muscle. It permits real-time investigations and yields statistically based criteria for the occurrence of fatigue. The findings are interpreted in terms of muscle action potential conduction velocity changes and rate of the fatigue development.
Saturation kinetics for steady-state pulmonary CO transfer
Authors: Mendoza C. , Peavy H. , Burns B. , Gurtner G.
Published: December 2017

Steady-state diffusing capacity of the lungs for carbon monoxide (DLCO) was measured in 13 anesthetized, paralyzed dogs ventilated at constant tidal volume and rate, using four different inspired CO levels (190, 600, 1,110, and 2,000 ppm). DLCO increased and reached a maximum as the inspired CO level was raised from 190 to 600 ppm. Further increases in inspired CO concentration were accompanied by a decrease in inspired CO concentration were accompanied by a decrease in DLCO. CO dead space and Pao2 remained constant at all inspired O2 levels. In some experiments a second set of measurements was made, the results of which were similar to those of the first set. The results cannot be explained by changes in CO back pressure, pulmonary capillary volume, or reaction rate of CO with hemoglobin, but can be explained if there is carrier-mediated CO transport in the alveolar capillary membrane.
Early response of plasma contents on exposure of working men to heat
Authors: Senay L. C.
Published: December 2017

Twelve men block-stepped (35 W) 4 h/day for 12 days and were divided into two similar groups on the basis of Vo2max. All were exposed to 33.8 degrees C dry bulb, 32.7 degrees C wet bulb for 2 h (E1) while working (30% Vo2max). Venous blood was obtained at 10-min intervals during hour 1 and at 20-min intervals during hour 2. Group 1 was acclimatized to heat. Group II continued to train. The test exposure was repeated (E2). During E1 a trend toward hemodilution was evident but not significant for either group. Protein moved into the vascular volume and a decrease in plasma osmolarity was significant only after 30 min. For both groups during E2 significant hemodilution occurred during the first 10 min. Only group I remained significantly hemodiluted for 2 h. Protein movement and osmodilution again occurred in both groups. These results support earlier suggestions as to the mechanisms of hemodilution based on 1-h blood samples. Conflicting evidence as to the pressure or absence of hemodilution upon heat exposure is noted, and a hypothesis is proposed which appears to reconcile divergent results.
Determining P50 in the presence of carboxyhemoglobin
Authors: Ledwith J. W.
Published: December 2017

A method is proposed, using mathematical solutions to the Roughton-Darling analysis, that theoretically can correct the measurements used for P50 determinations, whenever HbCO is present in blood, either initially or after equilibration. The resulting P50 is calculated in a “CO-free” state, independent of the actual presence of HbCO. This can be converted to a term designated T50, which indicates the in vivo shift caused by the concentration of HbCO measured. The concept was tested by comparing the P50 measurements in subjects with normal hemoglobins who differed by smoking habits (smokers vs. nonsmokers). The results showed similar mean values for this definition of P50, despite an average 10-fold difference in initial concentrations of HbCO. The method is applicable both to the single point principle, wherein P50 is estimated directly from venous blood measurements, and to standard tonometry-mixing techniques, as long as instrumentation includes the measurement of CO saturation.
Lactate release in relation to tissue lactate in human skeletal muscle during exercise
Authors: Jorfeldt L. , Juhlin-Dannfelt A. , Karlsson J.
Published: December 2017

In four healthy volunteers, muscle lactate concentration and the release of lactate from the leg were determined at rest and at 4 and 12 min of sitting bicycle exercise at four intensities (30, 50, 70, and 90% of maximal oxygen uptake). The muscle biopsies were obtained by needle biopsy technique from m. vastus lateralis. The rate of lactate release was calculated from the femoral venous-arterial differences of lactate and the leg blood flow was determined by constant rate dye infusion. Both leg blood flow and leg oxygen consumption increased linearly with work intensity. The release of lactate rose approximately linearly with the muscle lactate concentration up to about 4–5 mmol/min but then the relationship revealed a clear leveling off. These results indicate a maximal level for the lactate release from the exercising muscles with a translocation hindrance for lactate within the muscles.
Quantitative lung morphology in Japanese waltzing mice
Authors: Bartlett D. , Areson J. G.
Published: December 2017

We have reinvestigated the question of whether exercise stimulates lung growth by determining body weight (BW), lung volume (LV), alveolar surface area (SA), and alveolar number (N) in Japanese waltzing mice, in their phenotypically normal littermates, and in normal albino mice. BW, LV, SA, and N were all less in waltzing mice than in their littermates; LV/BW, SA/BW, and N/BW were indistinguishable in the two groups. Age-matched albino mice had larger BW and smaller N/BW than the waltzers or their littermates. The results indicate that both waltzing mice and their nonwaltzing littermates have more highly compartmentalized lungs than albino mice of the same age. However, the data provide no support for the hypothesis that sustained exercise enhances lung growth.
Calibration of a new ear oximeter in humans during exposure to centrifugation
Authors: Besch E. L. , Baumgardner F. W. , Burton R. R. , Gillingham K. K. , McPherson R. F. , Leverett S. D.
Published: December 2017

An optoelectronic ear oximeter (Hewlett-Packard, model 47201A) was evaluated as a noninvasive method for determining arterial oxygen saturation (SaO2) in human subjects during exposure to various levels of accelerative forces. This physiological calibration involved exposing five subjects, while breathing air and wearing the ear oximeter for 60 s to each of three levels of accelerative forces (3, 5, and 7 G); arterial blood samples were withdrawn concurrently. SaO2 was calculated indirectly from the oxygen tensions (PaO2) measured from the sampled arterial blood with a blood gas analyzer and corrected for pH and base excess. These data were compared, as were similar data taken from the same subjects breathing three different hypoxic gas mixtures while resitng at earth's gravity (1 G). Regression analyses of these data for both experimental groups (a, G exposure, or b, hypoxic exposure), comparing the ear-oximeter SaO2 with the calculated SaO2, showed the ear oximeter to be accurate with correlation coefficients of 0.95 and 0.98, respectively.
Influence of hypoxia on the longitudinal distribution of pulmonary vascular resistance
Authors: Dawson C. A. , Grimm D. J. , Linehan J. H.
Published: December 2017

We have examined the influence of hypoxia on the longitudinal distribution of vascular resistance and intravascular pressure in isolated cat lungs using the low-viscosity bolus technique. Hypoxia increased total vascular resistance, decreased total lung blood volume, and moved the maximum local resistance downstream away from the main pulmonary artery. The circumference of the main pulmonary artery was increased and the extravascular lung water (double indicator dilution technique) was decreased by hypoxia. Thus, it would appear that distension of the large pulmonary arteries and a decrease in the amount of lung tissue perfused contributed to the change in resistance distribution brought about by hypoxia.
Physical activity and hypophysectomy on the aerobic capacity of ligaments and tendons
Authors: Vailas A. C. , Tipton C. M. , Laughlin H. L. , Tcheng T. K. , Matthes R. D.
Published: December 2017

Traditionally, ligaments and tendons (L and T) have been regarded as metabolically inert structures. However, sufficient biochemical evidence on the metabolism of collagen has indicated that such a concept is no longer tenable. To determine whether L and T respond to increased or decreased levels of chronic exercise, studies were undertaken to measure their aerobic capacities. For comparative purposes, similar measurements were obtained from liver and skeletal muscles secured from normal and hypophysectomized male rats. Oxygen consumption and cytochrome oxidase (CO) activity was recorded from cell suspensions that had been prepared with the inclusion of collagenase and with elastase added to the medium. The O2 results showed that L and T had values that were approximately 10 times lower than liver tissue and 7.5 times less than the means from skeletal muscles. Hypophysectomy caused marked reductions in O2 uptake of liver and muscle tissues; but had no impact on L and T. When CO activity of these connective tissues were evaluated, immobilization and hypophysectomy caused significant reductions that ranged from -36% to -59% respectively. Training, on the other hand, resulted in increases of less than 10% in the activity of this enzyme within L and T while being elevated in muscle tissue by 58%. It was concluded that the metabolic activity of L and T was lowered with decreased levels of physical activity but it was unclear why chronic exercise did not produce the opposite effect.
Rat as a model for humanlike ventilatory adaptation to chronic hypoxia
Authors: Olson E. B. , Dempsey J. A.
Published: December 2017

Oxygen uptake (VO2), expired volume (VE), and arterial blood gases were studied in awake, unrestrained rats over 14 days of hypobaric hypoxia (4,300 m altitude) and upon return to acute normoxia. Control data (at 250 m) showed (mean +/- 95% confidence limits (CL)) arterial oxygen pressure (Pao2) = 85.5 +/- 1.1; arterial carbon dioxide pressure (PaCO2) = 39.8 +/- 0.5; arterial pH pHa) = 7.430 +/- 0.009; VE = 78 +/- 3; VO2 = 2.36 +/- 0.09 ml.min-1.100 g-1; and dead space volumetidal volume ratio (VD/VT) = 0.37 +/- 0.04. During 14 days at 4.300 m the rat showed: a) a constant PaO2 (50–52 Torr); b) a time-dependent hyperventilation (e.g., PaCO2 = 30.2 +/- 1.1 at 1 h of hypoxia, 24.7 +/- 1.3 at day and 21.9 +/- 1.0 at 14 days); c) an increase in VE (85% of control) due to both frequency (33%) and VT (40%); d) a continued but reduced hyperventilation upon acute return to normoxia after 5 h to 14 days at 4,300 m; e) a 24% fall in VO2 after 1 h of hypoxia which returned to control by 4 days at 4,300 m; and f) a rise in pHa to 7.52 after 5 h of hypoxia, which fell to 7.45 by 14-day hypoxia. The rat's marked ventilatory response and changing VO2 during acute hypoxia clearly differs from the human response to sojourn at 4,300 m. However, the progressive and sustained hypocapnia during hypoxic exposure and the continued hyperventilation with acute normoxia in the rat provided essential, perhaps unique characteristics for an animal model of human ventilatory acclimatization.