bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of atropine on potentiation of exercise-induced bronchospasm by cold air
Authors: Deal E. C. , McFadden E. R. , Ingram R. H. , Jaeger J. J.
Published: December 2017

The role of vagal efferent activity in the cold air potentiation of exercise-induced asthma was assessed by exercising nine subjects who breathed air at ambient and subfreezing temperatures before and after cholinergic blockade. Lung volumes and maximal expiratory flow volume curves with air and with 80% helium-20% oxygen were obtained before and 5--10 min after each challenge. Isovolume comparisons of maximal expiratory flow rates with the two gases were used to assess relative contributions of large and small airways to flow limitation. Exercise under ambient conditions resulted in the expected airway obstruction and cold air exaggerated the response. Atropine pretreatment had no effect on the cold air potentiation. After atropine with ambient air exercise, there was an increase in the relative contribution of large airways to flow limitation, whereas exercise with cold air resulted in an increase in the contribution of small airways. We concluded that the potentiating effects of cold air are local and suggest that the immediate stimulus is related to cooling of intrathoracic airways.
Elasticity of excised dog lung parenchyma
Authors: Vawter D. L. , Fung Y. C. , West J. B.
Published: December 2017

An experimental procedure was developed to measure the stress-strain relationship on rectangular slabs (5.0 X 5.0 X 0.5 cm) of excised dog's lung. The slabs were subjected to biaxial loading and the resulting triaxial deformations were measured. Deformations were measured in the central portion of the specimen by video dimension analysers in order to minimize boundary effects. Specimen thickness was measured with a magnetic reluctance proximeter system. The data were sampled and stored on-line by a PDP-8E computer. An electromechanical servo system was used to control the lateral force. Tests were performed at several pH values and at 20 and 37 degrees C. The tissue exhibited a highly nonlinear stress-strain relationship, compliant at low stress levels and stiff when the stress was high. Hysteresis was observed to be about 28% and was unaffected by a 250-fold change in strain rate. Biaxial loading revealed a new characteristic: there is a change in elastic behavior when the tissue undergoes a compressive strain. When the tissue was in tension increasing the lateral load decreased the compliance, but the opposite was true when compressive strain was present.
Influence of posture on isometric fatigue
Authors: Lind A. R. , Burse R. , Rochelle R. H. , Rinehart J. S. , Petrofsky J. S.
Published: December 2017

The isometric strength of four trained subjects was unaltered by changes in posture. But the endurance of an isometric contraction held to fatigue at 25 and 40% of the maximum voluntary contraction (MVC) was 20% greater in the sitting than in the recumbent posture. This difference was abolished when the exercise was performed with the arm's circulation arrested. At rest, the blood flow through the forearm was greater when the subjects were in the recumbent than in the sitting position but the reverse was true during isometric contractions. In these two postures, there was no difference in the right atrial pressure during the contraction, suggesting that the low-pressure baroreceptors are not responsible for the differences in blood flow during exercise. To date no mechanism is available to explain these observations.
An animal model for the study of regional lung function
Authors: Robinson S. M. , Cadwallader J. A. , Hill P. M.
Published: December 2017

An animal model for the study of regional lung function is described. In sheep, the bronchus to the right apical lobe (RAL) of the lung arises directly from the trachea. A tracheal divider, inserted under local anesthesia via a permanent tracheostomy, was used to separate the ventilation of the RAL from that of the rest of the lung. Lobar blood flow was estimated from the RAL contribution to the pulmonary clearance of an intravenous bolus of 85Kr. Gas exchange was measured by conventional methods. Expressed as a percentage of the value obtained for the whole lung, lobar expired volume was 14.7 +/- 4.3%, capillary perfusion was 12.3 +/- 4.2%, oxygen uptake was 14.7 +/- 4.9%, and carbon dioxide production was 13.4 +/- 5.5% (mean +/- SD of 25 studies in 11 animals breathing air). The model permits the study of experimental conditions confined to a single lobe of the lung and offers the advantages of an intact chest wall, spontaneous ventilation and an unanesthetized animal.
Lack of effect of vagal afferent input on central neural respiratory afterdischarge
Authors: Eldridge F. L. , Gill-Kumar P.
Published: December 2017

The effect of respiratory inhibition caused by vagal stimulation or lung inflation on the central neural mechanism that maintains respiration after cessation of a facilitatory stimulus was studied in anesthetized cats. Phrenic activity was increased by carotid sinus nerve stimulation or by squeezing or stretching calf muscle. On cessation of stimulation there was an immediate decrease in respiratory output followed by a slow decrease (afterdischarge) over a period of 5 min. Vagal stimulation or lung inflation, which caused marked inhibition of inspiration, had no effect on the development of the afterdischarge or on the course of the subsequent recovery process. The mechanism causing afterdischarge is probably a buildup of activity in a neural network in the medulla and pons. Since its activity is unaffected by vagal inhibition of respiration, it can be concluded that the network is separate from inspiratory output neurons and those involved in phase switching and that it is not dependent on increased central inspiratory neuron activity.
Blood flow and relative tissue PO2 of brain and muscle: role of carotid chemoreceptors
Authors: Neubauer J. A. , Feldman R. S. , Huang J. T. , Vinten-Johansen J. , Weiss H. R.
Published: December 2017

The effects of inspiration of low O2 and/or high CO2 gas mixtures on relative tissue PO2 and perfusion of brain and muscle were studied in 60 pentobarbital-anesthetized spontaneously respiring rats. These animals were studied in intact condition, after administration of phenoxybenzamine hydrochloride, 2 mg/kg, or after bilateral denervation of their carotid bodies. In the intact rats, the relative tissue PO2 ratio of biceps brachii to cerebral white matter always decreased after exposure to the above gas mixtures. This indicated a better maintenance of O2 supply to demand in the brain than in muscle. After either carotid denervation or alpha adrenergic blockade, this change in the ratio was no longer significant. Further, cerebral blood flow responses to these gas mixtures were attenuated (avg + 5.3%) compared to previous work in intact rats. It is concluded that the brain is best protected against hypoxia and/or hypercapnia when the carotid chemoreflex is intact.
Camel thyroid metabolism: effect of season and dehydration
Authors: Yagil R. , Etzion Z. , Ganani J.
Published: December 2017

The thyroid function of normally hydrated and dehydrated camels was examined in winter, spring, and summer. The thyroid was stimulated in summer when water was available, but was inhibited following dehydration. It is concluded that the decline of thyroid function, as gauged by hormone secretion during dehydration in the summer, aids in preservation of body water by decreasing pulmonary water loss and dropping basic metabolism.
Relaxed +GZ tolerance in healthy men: effect of age
Authors: Hull D. H. , Wolthuis R. A. , Gillingham K. K. , Triebwasser J. H.
Published: December 2017

Fifty-three healthy US Air Force aircrewmen, 26–55 yr old, volunteered for a centrifuge study designed to determine the effect of age on relaxed +GZ tolerance. Each was subjected to G forces of gradual and rapid onset, with G tolerance determined by standardized contraction of peripheral visual fields. Of the subject characteristics studied, only age was positively correlated with rapid-onset G tolerance; both age and weight were positively correlated with gradual-onset G tolerance. A combination of age and weight gave a stronger positive correlation with G tolerance (rapid- and gradual-onset) than did either characteristic alone. No significant negative correlations were observed. We conclude that aging may offer some protection from G stress; there is no evidence that aging leads to a decrement in G tolerance.
A simple technique for measuring alveolar CO2 in infants
Authors: Dumpit F. M. , Brady J. P.
Published: December 2017

We designed a system consisting of a nostril adapter and a catheter for measurement of end-tidal (–alveolar”) CO2 in small infants using the Beckman LB-1 analyzer. Using this system, we obtained a capillary-“alveolar” PCO2 difference (PaCO2-PACO2) of 2.4 Torr in 19 normal term infants, 3.5 Torr in 12 preterm infants who had recovered from respiratory distress syndrome, and 9.0 Torr in 4 preterm infants with bronchopulmonary dysplasia. We also found in 5 infants that systems using faster flow rates (140–400 ml-min-1) or slower response times (greater than 0.3 s) reduced the duration of the alveolar plateaus as well as the calculated end-tidal PCO2. In addition, when term infants were not in a steady state, PACO2 values were unreliable and significantly lower than capillary values. We therefore conclude that measurement of alveolar CO2 using our technique is a simple noninvasive way of evaluating newborn pulmonary function.
Modeling the effect of axial bronchial tension on expiratory flow
Authors: Wilson T. A.
Published: December 2017

Previous modeling of the expiratory flow-limiting mechanism is extended by including axial tension in the airway walls as one of the forces that affect airway mechanics. The analysis supports the Dawson-Elliott explanation of the plateaus in isovolume pressure-flow (IVPF) curves and shows that axial tension has the effect of increasing maximum flow and introducing a negative-effort-dependent region. Solutions for boundary conditions representing a cannula in the airways are qualitatively different with flow approaching zero as the pressure drop across the system becomes large.
Analysis of PCO2 differences during rebreathing due to slow pH equilibration in blood
Authors: Bidani A. , Crandall E. D.
Published: December 2017

A quantitative analysis of the reaction and transport processes that occur in blood during and after gas exchange has been used to investigate mechanisms that might account for positive alveolar-mixed venous (A-V) and alveolar-arterial (Aa) PCO2 differences during rebreathing. The analysis was used to determine PCO2 changes that take place in blood as it travels from veins to arteries under conditions in which no CO2 is exchanged in the lung. The predicted A-V and Aa PCO2 differences are all positive and lie within the range of reported measured values. The differences are due to disequilibrium of [H+] between plasma and red blood cells, and to disequilibrium of the reactions CO2 in equilibrium HCO3- + H+ in plasma, as blood leaves the tissue and/or lung capillaries. The differences are increased with exercise and with continued O2 uptake in the lung, the latter due to the Haldane shift. We conclude that the two disequilibria and the Haldane shift contribute to the reported PCO2 differences in rebreathing animals but may not fully account for them. These mechanisms cannot explain any PCO2 differences that might exist during net CO2 elimination from blood in the lung.
Elevated temperature effects on catecholamines and serotonin in brains of male Japanese quail
Authors: Braganza A. , Wilson W. O.
Published: December 2017

Endogenous level and turnover of brain norepinephrine (NE), epinephrine (E), dopamine (DA), and serotonin (5-HT) in male Japanese quail were determined after acute (6 h) and chronic (5 wk) exposure to thermal (34 degrees C) and cyclic temperature (10--34 degrees C) stress. alpha-Methyl-p-tyrosine (alpha-MT) and p-chlorophenylalanine (PCPA) were used to study the turnover of the monoamine levels. The differences between the monoamine levels of drug-treated birds and control (22 degrees C) birds were regarded as changes in turnover. High ambient temperature (34 degrees C) stress for 6 h increased brain NE turnover. However, chronic exposure (5 wk) to 34 degrees C, and to cyclic temperatures (10--34 degrees C), did not increase turnover of brain NE. Also, acute and chronic heat exposures did not significantly change E turnover. High acute temperature stress had no effect on brain DA turnover, although chronic exposure of birds to 34 and 10--34 degrees C resulted in a retarded turnover. The central 5-HT turnovers increased when birds were subjected to acute 34 degrees C stress. Five weeks of exposure to 34 and 10--34 degrees C caused declines in 5-HT turnovers. Thus, the results indicate that NE and 5-HT turnovers increase during acute thermal exposure, but acclimation to thermal stress for 5 wk reduces the turnover of brain NE, 5-HT, and DA.
Exercise performance and hemodynamics during dietary potassium depletion in dogs
Authors: Lowensohn H. S. , Patterson R. E. , Olsson R. A.
Published: December 2017

Dietary potassium depletion plus high sodium intake has been reported to elevate resting heart rate and cardiac output and to cause heart failure during exercise. We implanted aortic root electromagnetic flowmeters and aortic and pulmonary artery catheters in five splenectomized dogs condition-trained to run at 9 km/h on an 11% grade for 20 min. Postoperatively, the dogs ate a potassium-enriched diet until completion of control studies; then potassium was withdrawn. During 4 wk of depletion, skeletal muscle potassium fell from 380 +/- 22 to 311 +/- 8 meq/kg, and muscle sodium rose from 142 +/- 14 to 207 +/- 27 meq/kg (mean +/- SE). Cardiac output, aortic blood pressure, heart rate, acceleration of aortic blood flow at rest or during exercise, and the oxygen cost of exercise remained at control levels. Serum creatine phosphokinase at rest, an indicator of rhabdomyolysis, was never elevated. A 24% dietary depletion of muscle potassium in the dog did not change resting and exercise hemodynamics and exercise performance from control.
Pressure, temperature, and repetitive impulse generation in crustacean axons
Authors: Kendig J. J. , Schneider T. M. , Cohen E. N.
Published: December 2017

Increases in nerve axon excitability, including repetitive activity, have from time to time been reported in nerves subjected to high hydrostatic pressure. With the description of the high-pressure nervous syndrome (HPNS) in human divers and experimental animals, this phenomenon is of interest as a possible basis for the hyperexcitability associated with HPNS. The present study was designed to define the relationships between temperature, pressure, and repetitive activity in isolated crayfish axons. Crayfish claw nerves were exposed to helium pressures between 1 and 200 atmospheres absolute (ATA) in a temperature-controlled recording chamber. Repetitive and spontaneous impulses were reliably evoked on compression. The probability of repetitive response was increased by low temperature and high pressure; the frequency of the repetitive activity was increased by high temperature and pressure. Repetitive activity appeared spontaneously in the unstimulated preparation but could be entrained by the stimulus. The results are consistent with a mechanism involving changes in nerve membrane lipid fluidity and in the time course of membrane ionic channel state changes, including those involved in repolarization and accommodation.
Dissociated ventilatory and central respiratory responses to CO2 at raised N2 pressure
Authors: Linnarsson D. , Hesser C. M.
Published: December 2017

The effects of hyberbaric nitrogen on the responses of ventilation and central inspiratory activity (CIA) to progressive hypercapnia were studied in eight subjects rebreathing a) O2 at an ambient pressure of 1.3 bar (control), and b) air at 6.1 bar (PO2 = 1.3 bar, PN2 = 4.8 bar). Inspiratory occlusion pressure (P0.1), pulmonary ventilation, and end-tidal PCO2 were used for the computation of individual CIA and ventilatory CO2 response curves. Increasing the inspired PN2 to 4.8 bar caused, on the average, a 40% increase of P0.1 at PCO2 = 50 Torr, whereas the slope of the ventilatory CO2 response curve was reduced by 39%. It was concluded that, at raised air and nitrogen pressures, CIA is increased, although not sufficiently to prevent a reduction of ventilation brought about by the increased gas density and consequent increase in airway resistance. The increased airway resistance is thought to be responsible for the increase in CIA by causing a reflex stimulation of the respiratory centers.
Effect of lung volume on the diving response in man
Authors: Openshaw P. J. , Woodroof G. M.
Published: December 2017

In an attempt to clarify the influence of lung volume on the cardiac component of the diving response in man, 10 subjects were studied while holding their breath for 20 s after inspiration or expiration, with or without immersion of the face in water. The electrocardiogram was recorded before and during each maneuver. After expiration, an increase in pulse interval was seen only on face immersion. After inspiration, an equal change in pulse interval was seen whether or not the face was immersed. Therefore the early bradycardia of face immersion is not apparent after inspiration.
Effect of exercise on collateral development in dogs with normal coronary arteries
Authors: Cohen M. V. , Yipintsoi T. , Malhotra A. , Penpargkul S. , Scheuer J.
Published: December 2017

To determine the effects of chronic exercise on the coronary collateral circulation of dogs with normal coronary arteries, 1-yr-old purebred beagles were divided into sedentary control and exercising groups. The latter were trained to run on a treadmill. A lower maximal heart rate during a standardized exercise test protocol after a 10- to 12-week training period and a higher gastrocnemius cytochrome oxidase activity in the runners attested to the presence of cardiovascular and skeletal muscle training effects. However, left ventricular weights, left ventricle/body weight ratios, myocardial myofibrillar and myosin ATPases, and hemodynamics were similar in sedentary and exercising dogs except for a significantly higher resting cardiac output in the runners. After occlusion of the left anterior descending coronary artery, both collateral conductance (retrograde flow/aortic pressure) and collateral flow measured with microspheres tended to be lower in the trained dogs, but differences were not significant. The endocardial/epicardial flow ratio in the ischemic area after coronary occlusion did not distinguish between exercisers and controls. Thus treadmill running in the dog with normal coronary arteries produced a training effect, but had no effect on coronary collateral vessels.
Effect of lung volume history on rate of edema formation in isolated canine lobe
Authors: Goldberg H. S.
Published: December 2017

The effect of lung volume history and prior accumulation of interstitial fluid on rate of edema formation in isolated canine lobes was investigated. Mean pulmonary artery pressure and mean pulmonary venous pressure were kept constant at 40 and 30 cmH2O, respectively. Transpulmonary pressure (Ptp) was varied among 5, 15, and 25 cmH2O by progressive stepwise inflation and deflation. Rate of fluid accumulation was estimated by changes in slow weight gain after a change in Ptp. Although there is continuous interstitial fluid accumulation over the course of the experiment the results indicate that interstitial hydrostatic pressure around leaky vessels at Ptp of 15 cmH2O is reduced by prior lung inflation to Ptp of 25 cmH2O and increased by prior deflation to Ptp of 5 cmH2O. These results suggest that the distribution of interstitial fluid may vary as a function of lung volume history.
Response of the rat erythrocyte to ozone exposure
Authors: Larkin E. C. , Kimzey S. L. , Siler K.
Published: December 2017

Sprague-Dawley rats were exposed to high (6--8 ppm) and moderate (1.5 ppm) amounts of ozone (O3) for various time periods. Response of the rat erythrocyte to ozone was monitored with red blood cell potassium (rubidium) influx studies, with storage stress combined with ultrastructural studies and with levels of erythrocyte glutathione peroxidase and superoxide dismutase. Erythrocytes of rats exposed to O3 showed no significant changes either in their potassium influx or in their glutathione peroxidase and superoxide dismutase activities compared to controls. Erythrocyte differential counts on O3-exposed animals showed significant changes initially as well as following storage stress compared to controls. Rats exposed to 8 ppm O3 for 4 h showed a marked increase in echinocytes. These consistent transformations from discocytes to echinocytes following O3 exposure suggest latent erythrocyte damage has occurred.
Temperature-induced changes in blood acid-base status in the alligator, Alligator mississipiensis
Authors: Davies D. G.
Published: December 2017

Gas exchange and arterial blood acid-base status were measured in 13 conscious alligators, Alligator mississipiensis, at 15, 25, and 35 degrees C. Arterial pH decreased by 0.250 units (from 7.635 to 7.385) and arterial carbon dioxide partial pressure increased by 11.4 Torr (from 11.8 to 23.2) as body temperature increased from 15 to 35 degrees C. No statistically significant changes occurred in arterial bicarbonate concentration. When OH-/H+ and alpha-imidazole were compared at each temperature, more variability was observed in OH-/H+, which increased from 8.7 to 12.0 as temperature increased from 15 to 35 degrees C. alpha-Imidazole remained essentially constant (0.76 at 15 degrees C and 0.80 at 35 degrees C). Body temperature increase caused marked increases in minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2). The relative changes in these parameters resulted in a decrease in both VE/VO2 and VE/VCO2. The data of the present study are consistent with the concept that poikilotherms regulate their alveolar ventilation with changes in body temperature in order to keep OH-/H+ or alpha-imidazole constant.
Monocrotaline model of noncardiogenic pulmonary edema in dogs
Authors: Miller W. C. , Rice D. L. , Kreusel R. G. , Bedrossian C. W.
Published: December 2017

Monocrotaline, a plant alkaloid shown histologically to produce pulmonary endothelial damage and edema, was used in dogs to produce an acute model of noncardiogenic pulmonary edema. Following intravenous injection there was no change in pulmonary vascular pressures or heart rate; cardiac output fell and pulmonary vascular resistance increased. After 2 h measurement of lung water demonstrated modest pulmonary edema in all animals. The degree of edema produced was more consistent and reproducible than that following alloxan or alpha-naphthylthiourea.
O2 extraction by hind limb versus whole dog during anemic hypoxia
Authors: Cain S. M. , Chapler C. K.
Published: December 2017

The ability of the hind limb to obtain oxygen and maintain its O2 uptake in relation to the whole body during isovolemic hemodilution with dextran was measured in eight anesthetized, paralyzed dogs kept at constant ventilation. Hind limb venous outflow (ankle to upper thigh) was restricted by tourniquets to femoral vein. Hind limb blood flow, O2 uptake (VO2), cardiac output, and total VO2 were measured at normal hematocrit, at hematocrits just above (16%, stage 2) and just below (10%, stage II) that at which total VO2 could be maintained at the control level, and following isovolemic reinfusion of recovered red blood cells (Hct = 23%). VO2 was maintained at the control level in whole body and hind limb during stage I. Total VO2 decreased significantly in stage II (P less than 0.05), whereas limb VO2 did not. Hind limb had a consistently greater extraction ratio for O2 (P less than 0.01) and lower venous oxygen partial pressure than the body as a whole (P less than 0.01). In spite of limitations of O2 delivery by anemia to the point that total O2 demand was not met, there was no redistribution of blood flow away from or decreased demand for O2 by the hind limb, which was mostly skeletal muscle.
Spectral analysis of human inspiratory diaphragmatic electromyograms
Authors: Schweitzer T. W. , Fitzgerald J. W. , Bowden J. A. , Lynne-Davies P.
Published: December 2017

The inspiratory diaphragmatic EMG was recorded via esophageal electrodes in six normal subjects. The EMG and ECG signals were analyzed by power density spectral analysis, before and after band-pass filtering (20--1,600 Hz). The EMG spectrum was concentrated in the bandwidth 25--250 Hz. Electrode motion introduced a significant artifact only at low frequencies. The ECG spectrum was also concentrated at lower frequencies, but substantial power from the cardiac signal spilled over across most of the EMG spectrum. Band-pass filtering was therefore effective in minimizing the former but not the latter. Of the various power and frequency parameters used to quantitate the EMG spectrum, the most stable was the centroid frequency. This was reproducible within and between subjects, and was not affected by changing tidal volume or inspiratory flow rate.
Forced oscillatory respiratory parameters following papain exposure in dogs
Authors: Haddad A. G. , Pimmel R. L. , Scaperoth D. D. , Bromberg P. A.
Published: December 2017

Respiratory mechanics were studied in nine intubated dogs before and after exposure to aerosolized papain under conditions known to produce emphysemalike lesions. Forced oscillatory resistance (RFO), compliance (CFO), and inertance (IFO) were computed from impedance data obtained at transrespiratory pressures of -10, 0 (FRC), +10, and +20 cmHWO. Dynamic compliance during tidal breathing (CTB) was also measured at FRC. After papain exposure CTB and CFO increased by 25% (P less than 0.05) at FRC and at +10 cmH2O. There were no consistent changes in RFO or IFO at FRC. However, RFO showed a greater dependency on transrespiratory pressure, which suggests that the elastic properties of airways may also have been affected by papain. Measurements made in open-chested papain-exposed animals showed that about 17% of total RFO and 20% of total elastance were attributable to the chest wall. Forced oscillatory impedance data are sensitive to experimental changes in lung mechanics and provide useful estimates of standard respiratory parameters.
A new definition of mechanical work done in human movement
Authors: Winter D. A.
Published: December 2017

The definition of efficiency of human movement has often been unable to cope with activities such as level gait because the numerator of the efficiency equation includes only external work done by the body on an external load. The major purpose of this paper is to propose a definition that not only accounts for any external work but also the internal work done by the limbs themselves. The internal work involves a new biomechanical analysis that takes into account all potential and kinetic energy components, all exchanges of energy within and between segments, and both positive and negative work done by the muscles. This analysis was applied to a study of over-ground level gait on eight subjects walking at different walking speeds. The internal work/stride as calculated from the sum of segment energies was compared with the same calculation on the body's center of mass energy. The latter was found to be in error (low) by 16.2% and could be low by as much as 40%. The average internal work per body mass per distance walked was 1.09 J/kg.m.
Lung interdependence and lung-chest wall interaction of sublobar and lobar units in pigs
Authors: Zidulka A. , Sylvester J. T. , Nadler S. , Anthonisen N. R.
Published: December 2017

In anesthetized and paralyzed pigs in the left decubitus position we obstructed, at functional residual capacity (FRC), either the right middle and lower lobes, or a small posterior basal lung unit, and then passively inflated the unobstructed remaining lung. Measurements were made of alveolar pressure in the obstructed and unobstructed lung regions as well as of esophageal pressure. The tendency of the obstructed lung region to inflate as the remainder of the lung was inflated was assessed by an index (A), which was the end-inspiratory pressure difference between unobstructed and obstructed alveolar pressures, normalized by the change in elastic recoil of unobstructed lung. With the chest wall intact, inflation of unobstructed lung resulted in a tendency to inflate the obstructed regions. This tendency was abolished with the chest wall removed. In a second group of pigs with the basilar lung unit obstructed, the height of the unit was changed by turning a pig from right to left decubitus positions. In each position A was assessed with both spontaneous and positive pressure ventilation. The magnitude of A was found to vary directly with the magnitude of caudal diaphragmatic motion and was greatest with the lung unit dependent and with spontaneous ventilation. These results suggest that lung-chest wall interaction was a more important factor tending to preserve homogenous inflation than lung tissue interdependence.
Forearm and finger blood flow responses to passive body tilts
Authors: Mengesha Y. A. , Bell G. H.
Published: December 2017

Ten to fifteen healthy subjects, ages 18--30 yr, were used to assess the correlation of forearm blood flow with graded passive body tilts and vascular resistance and also to discern the relative effects of body tilts on finger blood flow. In the head-up tilts forearm blood flow and arterial blood pressure fell progressively, whereas forearm vascular resistance and pulse rate increased. In the head-down tilts the forearm blood flow and the arterial blood pressure increased, whereas the forearm vascular resistance and pulse rate decreased. These changes were found to be significantly correlated with the different tilt angles and with one another. In a preliminary study it was found that infrared heating of the carpometacarpal region produced finger vasodilatation similar to the forearm vasodilatation observed by Crockford and Hellon (6). However, unlike forearm blood flow, finger blood flow showed no appreciable response to either the head-up or head-down tilts. This indicates that the sympathetic tone and the volume of blood in the finger are not appreciably altered by this test procedure at least 1 min after the body tilt is assumed.
Use of an exponential function for elastic recoil
Authors: Colebatch H. J. , Ng C. K. , Nikov N.
Published: December 2017

To improve the quantitative representation of elastic recoil, an exponential function (V = A - B exp (-KP), where V is the lung volume, P is the recoil pressure, and A, B, and K are constants), has been fitted to static pressure-volume (PV) data by a least-squares technique using a digital computer. The PV points below about 50% total lung capacity (TLC) usually deviate from an exponential expression. Increasing the lower volume limit to which the exponential was fitted from 40 to 75% of TLC in 20 subjects, increased K and B/A significantly. Residual variance was lowest (approx 1.0 +/- 0.5%) when the lower volume limit was between 50 and 60% TLC. The PV points in the lower volume range deviated significantly less from exponential in a group of older subjects than for young subjects. The coefficient of variation of K and B/A for duplicate studies in 10 subjects was 9 and 14%, respectively. For inflation PV data, K was significantly lower and A significantly higher than for deflation. For PV data obtained after a submaximal inspiration, K did not change significantly. From this exponential function, the PV curve above 50% TLC can be satisfactorily described by K, B/A, and recoil pressure at TLC; other conventional parameters may be derived.
Variability of the configuration of maximum expiratory flow-volume curves
Authors: Tien Y. K. , Elliott E. A. , Mead J.
Published: December 2017

With a computer technique variability of the configuration of maximum expiratory flow-volume (MEFV) curves was studied in terms of slope ratio, SR. SR = dV/dV divided by V/V, where V is the instantaneous flow and V is the volume increment above residual volume.) Approximately four SR-V curves, each based on three to five smoothed and averaged MEFV curves, were derived for each of 20 normal subjects (aged 23–55 yr) on a single occasion, and again at least 1 wk later. Individual curves were largely reproducible, the maximum difference in SR at most volumes being 0.3–1 U, but frequently showed substantial yet reproducible fluctuations with volume. These corresponeded to hitherto unrecognized irregularities of maximum expiratory flow that may reflect sudden changes in the location of flow limitation.
Experimental canine anaphylaxis: cyclic nucleotides, histamine, and lung function
Authors: Lazarus S. C. , Chesrown S. E. , Frey M. J. , Reed B. R. , Mjorndal T. O. , Gold W. M.
Published: December 2017

We studied the effects of Ascaris suum antigen (iv) in 32 natively allergic, anesthetized dogs. After thoracotomy, bilateral cervical vagotomy, and propranolol, samples of peripheral lung frozen in situ were obtained for measurement of cyclic nucleotides and histamine. Following Ascaris, lung histamine decreased 20.4 +/- 3.7% (mean +/- SE), cAMP increased 391 +/- 122%, and cGMP increased 110 +/- 20% with increased plasma histamine and physiological changes of anaphylaxis. No significant changes occurred in 10 control dogs. Release of histamine, reflecting immunological degranulation of mast cells, correlated closely with the physiological effects of anaphylaxis. beta-Adrenergic stimulation with isoproterenol prevented these physiological effects of anaphylaxis in three dogs studied. Furthermore, the level of cAMP induced in lung tissue by beta-adrenergic stimulation in these dogs correlated with the degree of inhibition of immunologically induced histamine release. These results illustrate the suitability of this experimental preparation to study the biochemical and physiological mechanisms of anaphylaxis in vivo.
Lung volume and pleural pressure in the anesthetized hamster
Authors: Lai Y. L.
Published: December 2017

Lung volumes and respiratory pressures were measured in anesthetized male hamsters weighing an average 117 g. In 16 supine animals functional residual capacity (FRC) determined by body plethysmograph was 1.12 +/- 0.23 (SD) ml (about 20% total lung capacity, TLC) slightly and significantly larger than the FRC measured by saline displacement, 1.01 +/- 0.15 ml. Similar results were found in six prone animals. Paralysis did not significantly alter supine FRC. Contrary to published reports, pleural pressure (Ppl) estimated from esophageal pressure was negative at FRC. The fact that lung volume decreased by 0.2 ml (about 4% TLC) when the chest was opened at FRC provided additional evidence of negative Ppl at FRC. No consistent changes in the lung pressure-volume curve were found after the chest was opened. Deflation chest wall compliance just above FRC was about twice lung compliance. The vital capacity and reserve volumes in this study agreed with values reported in the literature. However, absolute lung volumes (TLC, FRC, and residual volume) were lower by about 1.4 ml, possibly because of earlier overestimates of box FRC.
Metabolic and cardiopulmonary responses to wheelchair and bicycle ergometry
Authors: Glaser R. M. , Sawka M. N. , Laubach L. L. , Suryaprasad A. G.
Published: December 2017

To evaluate wheelchair activity in reference to a more familiar mode of locomotion, metabolic and cardiopulmonary responses to wheelchair ergometer (WERG) and bicycle ergometer (BERG) exercise were compared. Eighteen able-bodies subjects were tested on a combination wheelchair-bicycle ergometer. Oxygen uptake (VO2), respiratory exchange ratio (R), pulmonary ventilation (VE), ventilatory equivalent (VE/VO2), percent net mechanical efficiency (ME), and heart rate (HR) were determined at power output (PO) levels of 30, 90, and 150 kpm/min on each ergometer. For WERG and BERG exercise, VO2, VE, and HR increased linearly with PO. Generally, VO2, R, VE, VE/VO2, and HR responses were higher (P less than 0.05) during WERG than BERG exercise at each PO. Blood lactate was determined after 150 kpm/min, and found to be higher (P less than 0.05) during WERG than BERG exercise. ME increased with PO and was lower (P less than 0.05) for WERG than BERG exercise at each PO level. The greater metabolic and cardiopulmonary responses observed during WERG exercise may be due to inefficient biomechanics and the relatively small upper body musculature used for propulsion.
Rib cage deformation during static inspiratory efforts
Authors: Saunders N. A. , Kreitzer S. M. , Ingram R. H.
Published: December 2017

Patterns of rib cage (RC) deformation were studied in six normal subjects during moderate static inspiratory efforts such that esophageal pressure (Pes) as an index of transthoracic pressure fell to between -30 and -60 cmH2O during each maneuver. At lung volumes below 50% inspiratory capacity (IC), static inspiratory efforts deformed RC to a more elliptical shape; RC lateral diameter became smaller and RC lateral diameter became larger. However, at high lung volumes (greater than 50% IC) the opposite change in RC dimensions occurred despite similar changes in Pes, i.e., the RC became more circular. These differences in RC deformation did not appear to be a possive consequence of increased lung volume because the RC could be voluntarily deformed to a more circular shape at low lung volume when a) subjects performed static inspiratory efforts mainly with their intercostal and accessory muscles rather than their diaphragm as judged by a smaller change in transdiaphragmatic pressure for the same Pes; or b) subjects statically contracted their diaphragm with it held in a relatively flattened configuration as assessed by a large abdominal AP dimension. We suggest that deformation of the RC during static inspiratory efforts is not as predictable as has previously been suggested but depends on the pattern of contraction and configuration of the respiratory muscles.
Effects of inspiratory flow pattern on gas exchange in normal and abnormal lungs
Authors: Modell H. I. , Cheney F. W.
Published: December 2017

To study the influence of inspiratory flow pattern on gas exchange in normal and abnormal lungs, 15 dogs were mechanically ventilated with the ascending or descending half of a rectified sine-wave flow pattern during pentobarbital anesthesia. Blood-gas status and cardiac output were monitored during each pattern. Pulmonary injury was induced in 9 animals by prior injection of oleic acid into the right atrium. Ventilation was with room air and zero end-expiratory pressure. Although no significant difference was seen between the patterns in animals with normal lung function (PaO2 greater than 85 Torr on the ascending pattern), the descending pattern resulted in a rise in PaO2 of about 10% (P less than 0.01) in animals with abnormal lung function (PaO2 less than 70 Torr on the ascending pattern). No significant difference in PaCO2 or cardiac output was detected when flow pattern was changed in any of the animals. We conclude that inspiratory flow pattern is not a significant factor when ventilating normal lungs, but may improve gas exchange significantly when severe ventilation-perfusion maldistributions exist.
One- and three-minute exercise response in coronary artery disease
Authors: Auchincloss J. H. , Gilbert R. , Kuppinger M. , Peppi D. , Teperow-Putter K.
Published: December 2017

Treadmill exercise responses of oxygen uptake (VO2), CO2 production (VCO2), and venoarterial CO2 difference (Cv-Ca), measured by CO2 rebreathing (Defares technique) at 1 and 3 min of exercise, were studied in two separate series of control (apparently healthy) and coronary artery disease (CAD) subjects. In the 1-min series there were 21 controls and 15 CAD subjects. In the 3-min series there were 21 controls and 18 CAD subjects. All were males, ages 30--60 yr, and the CAD subjects had histories of myocardial infarction. In both series VO2 at 1 min and power requirement (P ) = 1,000 (VO2–1–1,000) was estimated where P =weight (kg) X grade (fractional) X walking speed (m/min). In the 1-min series (P = 1,000) all measurements were made at 45--60 s in separate test runs. In the 3-min series P was 750 kg.m/min, VCO2 and VO2 were measured at 2.5--3 min exercise, and Cv-Ca was measured at 3--3.25 min in the same test run. Data indicate that the average cardiac output (Q) for control subjects was 15 l/min in both series with lower values for CAD subjects. At 1 min reduced Q was accompanied by reduced VO2 or VCO2 and increased Cv-Ca, whereas at 3 min reduced Q was accompanied by increased Cv-Ca.
Abolition of a viscerosomatic reflex during oxygen deprivation
Authors: Ahluwalia J. M.
Published: December 2017

Effect of hypoxia was studied on the J reflex, a term used for the reflex inhibition of muscular exercise by activation of type J pulmonary endings. Hypoxia was induced by ventilating the animal with gas mixtures varying from 18 to 9% oxygen in nitrogen. The blood gas tensions of the arterial blood (PaO2) were measured before, during, and after hypoxia. It was found that the J reflex is sensitive to a reduction in oxygen. A fall in PaO2 between 67 and 47 Torr abolished this reflex. Studies were also undertaken to exclude the possibility that the effect of hypoxia was predominantly exerted on monosynaptic reflex itself. A similar fall in PaO2 also depressed the monosynaptic reflex. Minimum time required for the significant depression was 32 s. On the contrary the J reflex was abolished within this period suggesting that the abolition of J reflex is independent of the changes in monosynaptic reflex during hypoxia.
Cerebral gas exchange: perfusion and diffusion limitations
Authors: Ohta Y. , Farhi L. E.
Published: December 2017

The simultaneous washout of argon and methane from brain tissue stores was studied in anesthetized dogs that were rendered either hypocapnic or hypercapnic. The washout pattern can be analyzed in terms of two compartments with different rate constants. The two tracers were eliminated at the same rate from any one compartment in either experimental condition. Because argon and methane have the same blood-brain partition coefficient, and a ratio of molecular weights of 2.5, we conclude that their transport into or from the brain is not limited by diffusion over a wide range of cerebral blood flows.
Solubility and partition coefficients for gases in rabbit brain and blood
Authors: Ohta Y. , Ar A. , Farhi L. E.
Published: December 2017

Solubility and partition coefficients for argon, methane, neon, nitrogen, and sulfur hexafluoride in normal saline, rabbit blood, and exsanguinated rabbit brain were determined in a two-step process that involved equilibration of the various aliquots, and subsequent analysis by gas chromatography. Brain-blood partition coefficient was specifically higher than one for argon, neon, and sulfur hexafluoride, and questionably significant (P less than 0.025) for nitrogen.
Ventilatory response to muscular exercise: observations regarding a humoral pathway
Authors: Levine S.
Published: December 2017

To assess the role of humoral mechanisms in eliciting the hyperpnea of muscular exercise, anesthetized dogs underwent complete spinal transection at the second lumbar level (L2). Muscular exercise of the denervated hindlimbs was then induced by electrical stimulation. Coincident with hindlimb muscle contraction, oxygen consumption (VO2) increased 173% and ventilation (VE) increased 163%; no statistically significant changes occurred in arterial carbon dioxide tension (PCO2), arterial pH, or arterial oxygen saturation. Similar results were obtained after peripheral chemodenervation and vagotomy plus spinal transection. In order to evaluate the possibility that extracranial receptors mediate the increases in VE elicited by exercise-induced humoral factors, heads of vagotomized L2 spinal-transected dogs were perfused entirely by a support dog with blood of unchanging gas composition via both carotid and both vertebral arteries. The carotid bodies lay within the region of the perfused head; the aortic bodies were denervated. These L2 spinal-transected head-perfused animals still responded to hindlimb exercise with a 156% increase in VO2 and a 122% increase in VE. We conclude that muscular exercise can stimulate VE via humoral factors other than usual chemical stimuli in arterial blood (i.e., PCO2, pH, or O2 saturation). Extracranial receptors (other than conventional peripheral arterial chemoreceptors) appear to mediate a major portion of the increase in VE elicited by exercise-induced humoral factors.
Lung elasticity in regional and diffuse pulmonary fibrosis
Authors: Fine R. , McCullough B. , Collins J. F. , Johanson W. G.
Published: December 2017

Static deflation air and saline pressure-volume (PV) curves were performed on five normal excised baboon lungs, four with radiation-induced upper lobe fibrosis, and two with diffuse bleomycin-induced fibrosis. Curves were compared visually and using half-inflation pressures (h). When plotted as percent of observed vital capacity vs. transpulmonary pressure, the radiation-associated curves were similar in shape to control curves. Also, h values were not significantly different between the two groups. The bleomycin-associated curves, however, were shifted rightward and exhibited increased h values. PV curves were correlated with connective tissue data. Elastin concentration was increased in the irradiated upper lobes through loss of associated constituents. Elastin accumulated in the lower lobes of the irradiated animals through compensatory growth and in the bleomycin-associated lungs through excessive production. Collagen followed a similar but less dramatic trend. We conclude connective tissue accumulation may not lead to rightward shifted PV curves if accumulation is present in relatively noninflatable lung units, or as part of compensatory lung growth.
Subcutaneous tissue gas space pressure during superficial isobaric counterdiffusion
Authors: Cowley J. R. , Allegra C. , Lambertsen C. J.
Published: December 2017

Changes in subcutaneous tissue pressure caused by N2O-He, 1-ATA isobaric counterdiffusion gas phase development were measured. Only the ears of New Zealand White rabbits were subjected to counterdiffusion. The rabbits breathed a mixture of 80% N2O-20% O2 while their ears alone were surrounded by He and the rest of their bodies continued to be surrounded by air. Subcutaneous pressure changes were transmitted to the transducer-recorded system via a fluid-filled subcutaneous needle. When the gas phase developed in subcutaneous tissue, pressure rose and a maximum pressure (Pmax) was reached. Pmax in the counterdiffused ear was 48 +/- 10 (SD) Torr, and mean time to reach Pmax was 75 +/- 10 (SD) min. The findings are discussed in relation to the pathological processes of isobaric inert gas counterdiffusion.
Initiation of each avian inspiration by a CO2 threshold mechanism
Authors: Miller D. A. , Kunz A. L.
Published: December 2017

The avian respiratory oscillator has been investigated in a unidirectionally ventilated chicken by changing the dynamic pattern of inflow CO2 concentration (FCO2). Stimulation with periodic FCO2 results in a one-to-one synchronization of the respiratory movements that we have called pacing (Respir. Physiol. 22: 167--177, 1974). A two-parameter CO2 threshold model is proposed to explain this behavior. The model states that when FCO2 reaches a threshold level (L), it initiates the beginning of inspiration a constant time interval (LB) later. According to this model, when a triangular FCO2 concentration is used to synchronize the breathing pattern, the time from the minimum of the wave form to the beginning of inspiration (C-B interval) is dependent on the mean value and the rate of rise of FCO2 as determined by period and amplitude of the triangle. Particularly interesting is the prediction that the direction of the relationship (increasing or decreasing) between FCO2 amplitude and the C-B interval is dependent on whether the mean value of FCO2 is above or below the threshold level. Experimental data obtained during amplitude changes support the above prediction.