bluuebunny/crossref_metadata_2025 huggingface dataset:
Spontaneous mechanical activities of dog trachealis muscle in vivo
Authors: Beinfield W. H. , Seifter J.
Published: December 2017

Isometric strain gauge arches attached transversely and longitudinally to cervical trachealis muscle (CTM) recorded spontaneous mechanical activities (SMA), passive constriction, and longitudinal tension in 64 dogs anesthetized with pentobarbital. Inspiratory tracheal elongation increased longitudinal tension and passively constricted CTM. Occasional overlapping of tracheal cartilages observed on initial exposure of cervical trachea appeared to be due to unprovoked persistent increases in SMA. Three major types of rhythmic SMA oscillations occurred in 42 lightly anesthetized dogs: slow oscillations 50 - 200 s/cycle (19 dogs); sinelike waves 20-30 s/cycle (12 dogs); and sinelike waves superimposed on slow oscillations (11 dogs). These rhythms were dampened by pharmacologically induced incrases or decreases in SMA. They disappeared following deeper anesthesia, atropinization, or bilateral vagotomy. Intravenous acetylcholine increased while isoproterenol decreased SMA before and after bilateral vagotomy in spontaneously breathing dogs as well as in artificially ventilated curarized dogs whose tracheas were isolated in situ. Atropine blocked acetylcholine actions and propranolol blocked those of isoproterenol. Changes in SMA induced pharmacologically did not correlate with simulatenous alterations in systemic arterial pressure of ventilatory patterns.
Ventilatory responses to intravenous and airway CO2 administration in anesthetized dogs
Authors: Fordyce W. E. , Grodins F. S.
Published: December 2017

The ventilatory responses to steady-state venous CO2 loading (iv CO2) and CO2 inhalation have been observed in chloralose-urethan-anesthetized dogs. Intravenous CO2 was administered by increasing the CO2 fraction of gas ventilating a membrane gas exchanger in an arteriovenous bypass; blood flow rate was fixed at 30 ml/min. During the study, we identified a time-dependent hyperventilation in all 14 experimentally treated dogs and in 4 additional sham-treated dogs. When we tested 8 of these animals with a protocol having small progressive increments in iv CO2 loading rate, we observed a response approaching isocapnia during iv CO2 and a large hypocapnia when we returned to control conditions. The use of a randomized protocol in 6 animals demonstrated the necessity of accounting for this systematic base-line shift, because before doing so the response depended more on the passage of time than on the nature of the CO2 load. After this analytical adjustment was made, there was no significant difference between the respiratory controller gains (delta nu E/delta Paco2) for inhaled and iv CO2.
Sleep and maturation of eucapnic ventilation and CO2 sensitivity in the premature primate
Authors: Guthrie R. D. , Standaert T. A. , Hodson W. A. , Woodrum D. E.
Published: December 2017

The effects of sleep state and postnatal maturation on steady-state CO2 sensitivity, "inspiratory drive" (VT/TI), and the inspiratory "duty cycle" (TI/Ttot) were examined in nine unanesthetized premature Macaca nemestrina in the first 3 wk of life. Minute volume (VE) in room air was less in NREM sleep than in the awake state but there were no differences in VE, VT/TI, or TI/Ttot between REM and NREM sleep. VE and VT/TI corrected for body weight increased in REM and NREM sleep with postnatal maturation whereas TI/Ttot did not vary. Concomitant with this increase in room air VE and VT/TI, an increase in CO2 sensitivity (delta V/delta Paco2) with postnatal maturation was documented in NREM sleep. CO2 sensitivity was similar between REM and NREM states at each postnatal age. The increase in VE following inhalation of 2-5% CO2 was mediated by an increase in VT/TI, whereas TI/Ttot remained constant. The differences in the effect of sleep on CO2 sensitivity between neonates and adults are discussed and possible mechanisms for the observed developmental increase in CO2 sensitivity are proposed.
Relative latency of responses of chemoreceptor afferents from aortic and carotid bodies
Authors: Lahiri S. , Nishino T. , Mulligan E. , Mokashi A.
Published: December 2017

Discharges from aortic and carotid body chemoreceptor afferents were simultaneously recorded in 18 anesthetized cats to test the hypothesis that aortic chemoreceptors, because of their proximity to the heart, respond to changes in arterial blood gases before carotid chemoreceptors. We found that carotid chemoreceptor responses to the onset of hypoxia and hypercapnia, and to the intravenously administered excitatory drugs (cyanide, nicotine, and doxapram), preceded those of aortic chemoreceptors. Postulating that this unexpected result was due to differences in microcirculation and mass transport, we also investigated their relative speed of responses to changes in arterial blood pressure. The aortic chemoreceptors responded to decreases in arterial blood pressure before the carotid chemoreceptors, supporting the idea that the aortic body has microcirculatory impediments not generally present in the carotid body. These findings strengthened the concept that carotid bodies are more suited for monitoring blood gas changes due to respiration, whereas aortic bodies are for monitoring circulation.
Lung degassing: an evaluation of two methods
Authors: Stengel P. W. , Frazer D. G. , Weber K. C.
Published: December 2017

This study compares the effectiveness of the oxygen absorption and vacuum degassing methods for removing trapped gas from lungs. In addition, the effects of changing vacuum pressure, number of times to degas, and lung orientation during the vacuum degassing procedure were evaluated. To evaluate the two methods, a capacitance spirometer was designed and constructed to record lung volume as lungs were vacuum degassed. When lungs containing trapped gas were degassed in a vacuum chamber, they initially expanded, then slightly decreased in volume until the vacuum was released. Lung volume rapidly decreased as the pressure in the vacuum chamber returned to ambient pressure. The results showed that oxygen absorption atelectasis was more effective in removing gas from the lungs than vacuum degassing the lungs. When vacuum degassing was use, it was found to be most effective when the pressure in the chamber was reduced to the vaporization pressure of H2O and when the lungs were degassed twice. Degassing the lungs more than twice did not significantly remove more gas from the lungs. Lung orientation did not affect the removal of gas during vacuum degassing.
Fast-responding flow-independent blood gas catheter for oxygen measurement
Authors: Lundsgaard J. S. , Jensen B. , Gronlund J.
Published: December 2017

Analytic expressions were derived for the response time, flow dependency, and signal-to-background ratio of blood gas catheters. These expressions were utilized to optimize the design of a new catheter. The catheter was tested in vitro and in vivo, and shown to be fast responding and practically flow independent, with an acceptable signal-to-background ratio.
Factors determining degree of inflation in intratracheally fixed rat lungs
Authors: Hayatdavoudi G. , Crapo J. D. , Miller F. J. , O'Neil J. J.
Published: December 2017

The total lung capacity (TLC) of rats was measured in vivo and was compared to the displacement volume of the lungs following intratracheal fixation with glutaraldehyde or formaldehyde solution. When glutaraldehyde was used the speed of infusion of the fixative was an important factor in the final degree of lung inflation achieved. With a low rate of fixative infusion and a final pressure of 20 cm of fixative the glutaraldehyde-fixed lungs inflated to 55% TLC. With a high initial flow of glutaraldehyde and a final pressure of 20 cm of fixative the lungs inflated to 84% TLC. Fixation of lungs inside the intact chest wall was found to result in a higher degree of inflation. With a reservoir height of 20 cm and a low rate of fixative infusion lungs fixed in situ reached 74% TLC, whereas lungs fixed in situ, but from animals that have been exsanguinated prior to fixation, inflated to only 58% TLC. This suggests that the volume of the blood in the lungs prior to infusion of glutaraldehyde influences the degree of inflation achieved. Formaldehyde-fixed lungs required 72 h to be completely fixed and they were inflated to 90% TLC when a reservoir height of 20 cm was used. Because of the slow rate of fixation using with formaldehyde solution the rate of infusion was found not to limit the degree of inflation that could be achieved.
Effect of CO2 and 100% O2 on cerebral blood flow in preterm infants
Authors: Leahy F. A. , Cates D. , MacCallum M. , Rigatto H.
Published: December 2017

To determine 1) the effect of arterial CO2 change on the neonatal cerebral circulation and 2) whether 100% O2 would produce significant decrease in cerebral blood flow (CBF), we studied 24 preterm infants to explain the late (5 min) hyperventilation observed in them during hyperoxia. Of these, 12 were studied before and during inhalation of 2-3% CO2 and 12 before and during the inhalation of 100% O2. We measured CBF by a modification of the venous occlusion plethysmography technique and found that CBF increased 7.8% per Torr alveolar carbon dioxide pressure change and that it decreased 15% with 100% O2. These findings suggest that 1) CO2 is an important regulator of CBF in the perterm infant, 2) CBF-CO2 sensitivity in these infants may be greater than in adult subjects, 3) 100% O2 reduced CBF significantly, and 4) a decrease in CBF during administration of 100% O2 may be at least partially responsible for the increase in ventilation with hyperoxia.
Methods for identifying respiratory oscillations disclose altitude effects
Authors: Brusil P. J. , Waggener T. B. , Kronauer R. E. , Gulesian P.
Published: December 2017

A very important problem in the analysis of biological data sequences is the detection of oscillations in the presence of random variations (noise). If the oscillations are not stationary, i.e., if they drift in frequency and amplitude, or occur in bursts, traditional analysis techniques utilizing the power spectrum or its time-domain equivalent, the autocorrelation function, can be both misleading and insensitive. Temporal filtering by a “comb”or se of band-pass filters is very effective for identifying and describing nonstationary oscillations. The basic procedures for interpreting the output of a comb filter are presented here, illustrated by examples using predefined input test sequences.
An automatic sigh feature for animal ventilators
Authors: Gibson R. D. , Gisser D. G. , Newell J. C.
Published: December 2017

A device is described that provides a reliable automatic deep breath to an animal being ventilated with a typical laboratory ventilator. The deep breath is provided by closing a solenoid valve in the expiratory tubing causing the animal to inspire two, three, or four consecutive tidal volumes without expiration. The interval between deep breaths is selected to be every 1, 2, 4, 6, 8, or 10 min. Control of this interval is provided by simple integrated circuits. Total parts cost of this device is approximately $90.
Pulmonary inactivation of serotonin and site of serotonin pulmonary vasoconstriction
Authors: Rickaby D. A. , Dawson C. A. , Maron M. B.
Published: December 2017

To determine whether the site of serotonin-induced pulmonary vasoconstriction is influenced by serotonin uptake and inactivation within the lung, we utilized an isolated perfused left lower lobe of the dog lung, which could be perfused with flow in the normal direction (i.e., blood flowing into the lobar artery) or in the retrograde direction (i.e., blood flowing into the lobar vein). To localize the site of vasoconstriction, we utilized an outflow occlusion technique in which the changes in lobar vascular resistance were divided into changes in arterial and venous resistances. Serotonin infusion constricted vessels on the arterial side of the site of serotonin uptake during both forward and retrograde perfusion while having much less influence on the venous side. However, during retrograde perfusion the serotonin infusion rate required to produce a given increase in arterial resistance was approximately 85 micrograms/min greater than during forward perfusion. Thus, it would appear that serotonin was primarily an arterial constrictor in this preparation and that, although the lung removed a substantial quantity of serotonin, the uptake and inactivation within the lung had relatively little influence on the site of serotonin vasoconstriction.
O2 extraction by canine hindlimb during alpha-adrenergic blockade and hypoxic hypoxia
Authors: Cain S. M. , Chapler C. K.
Published: December 2017

Hindlimb and total blood flow and O2 uptake were measured in anesthetized paralyzed dogs in which venous outflow from the left hindlimb (less paw) was directed through the femoral vein. After ventilation on room air, 10 dogs were given 3 mg/kg phenoxybenzamine + 10 ml/kg dextran and 10 other dogs were isovolemically exchanged with 10 ml/kg dextran without alpha-block while continuing to be ventilated on room air. All animals were then ventilated with 9.1% O2 in N2, followed by a recovery period on room air. Total and limb peripheral resistances were lowered by alpha-block, but total and limb blood flow changed little from control levels. Both total and limb O2 uptake were decreased below control values during hypoxia. Cardiac output and limb blood flow increased during hypoxia in both groups. Although alpha-block caused O2 extraction by the whole body to be less during hypoxia than in unblocked dogs, the hindlimb in both groups extracted O2 equally well. We concluded that skeletal muscle was not overperfused relative to O2 demand when alpha-blocked during hypoxia.
CO2-induced changes in ventilation and ventilatory pattern in normal sleeping infants
Authors: Haddad G. G. , Leistner H. L. , Epstein R. A. , Epstein M. A. , Grodin W. K. , Mellins R. B.
Published: December 2017

The effect of CO2 on the ventilatory pattern of 18 normal infants was studied during sleep at monthly intervals through the age of 4 mo. Using the barometric method, we measured tidal volume (VT), respiratory cycle time (Ttot), inspiratory time (TI), and expiratory time (TE). Two percent CO2 produced no change in TI and a significant increase in VT and mean inspiratory flow (VT/TI). There was no consistent change in TE or Ttot in either sleep state at any age. The percent increase from base line in instantaneous minute ventilation (VT/Ttot) during REM sleep was similar to that during quiet sleep. We conclude that with inhalation of 2% CO2 in the first 4 mo of life 1) the increase in VT/Ttot results solely from an increase in VT and the percent increase in VT/Ttot is the same in both sleep states and 2) the reflex termination of inspiration by inflation does not play an important role in eupnea during sleep because the increase in VT is not associated with a decrease in TI.
Effects of wind assistance and resistance on the forward motion of a runner
Authors: Davies C. T.
Published: December 2017

The aerobic energy cost (delta VO2) of running at different speeds (V) with and against a range of wind velocities (WV) has been studied in a wind tunnel on three healthy male subjects and the results compared with downhill and uphill gradient running on a motor-driven treadmill. In terms of equivalent horizontal and vertical forces, comparison showed that the two forms of exercise were physiologically identical for gradients and WV ranging from -10 to +5% and 1.5 to 15 m . s-1, respectively. The apparent mechanical efficiencies of the work performed with a head and following wind were approximately +0.35 and -1.2. At WV greater than 15 m . s-1 it was more efficient to run against the wind and the corresponding gradient on the treadmill. At high WV the subjects altered their posture and "leaned" into the wind, thus possibly converting potential drag into body lift. The energy cost of overcoming air resistance on a calm day outdoor was calculated to be 7.8% for sprinting (10 m . s-1), 4% middle-distance (6 m . s-1), and 2% marathon (5 m . s-1) running.
Control of skin blood flow during exercise by thermal reflexes and baroreflexes
Authors: Roberts M. F. , Wenger C. B.
Published: December 2017

Four male subjects exercised on cycle ergometers at 40-51% of maximal aerobic power in the upright and supine positions at air temperatures of 15, 25, and 40 degrees C. Esophageal temperature (Tes) was measured at heart level, and mean skin temperature was computed from a weighted average of eight skin temperature measurements. Forearm blood flow (ABF) was measured by venous occlusion plethysmography, and cardiac output was measured by a CO2 rebreathing technique. At air temperatures of 15 and 25 degrees C, cardiac stroke volume was slightly lower during upright exercise than it was during supine exercise, as was ABF at a given Tes. At 40 degrees C, however, stroke volume was much lower and ABF at a given Tes was considerably lower during upright as opposed to supine exercise. The reduced stroke volume during upright exercise in the heat shows that gravity compounds the effect of cutaneous venodilation by allowing blood to pool in dependent limbs and thus impairing cardiac filling. The proportionality between reduced stroke volume and reduced forearm blood flow suggests that the reduction in blood flow may be mediated by cardiopulmonary baroreflexes that are activated by reduced cardiac filling pressure.
alpha-Adrenergic control of intestinal circulation in heat-stressed baboons
Authors: Proppe D. W.
Published: December 2017

The mechanisms involved in producing intestinal vasoconstriction during a hyperthermia-producing intestinal vasoconstriction during a hyperthermia-producing environmental heat stress are unknown. Five conscious baboons (Papio anubis), each with chronically implanted catheters and a flow probe around the superior mesenteric artery, were subjected to environmental heating (Ta 40-45 degrees C) to raise their arterial blood temperature (Tbl) 2.0-2.6 degrees C to approximately 39.5 degrees C. Accompanying the gradual rise in Tbl was a fall in mean superior mesenteric artery blood flow (MSMF) and a progressive rise in superior mesenteric vascular resistance (SMR). At peak Tbl, MSMF had fallen 28.8 ± 0.6% (mean ±SE) and SMR had risen 50.2 ± 4.2%. To determine the involvement of the sympathetic nervous system in producing this intestinal vasoconstriction, the baboon was subjected to environmental heating after induction of alpha-adrenergic receptor blockade by phenoxybenzamine or phentolamine. In this state, the rise in Tbl was accompanied by no change in MSMF and a slight, but not statistically significant, rise (7.8 ± 3.8%) in SMR. Since alpha-receptor blockade nearly completely abolishes intestinal vasoconstriction during heat stress, this intestinal vasoconstriction must be mediated primarily by elevated sympathetic outflow.
Energy expended during oxygen deficit period of submaximal exercise in man
Authors: Pahud P. , Ravussin E. , Jequier E.
Published: December 2017

Aerobic (MR) and anaerobic (Man) metabolism was determined during the transition from mild (50 W external work) to heavier exercise (50% VO2max) in six subjects. The overall exercise efficiency was calculated during the oxygen deficit period and during steady-state exercise. MR was obtained by indirect calorimetry and Man by solving the heat balance equation: MR + Man - S = (R + C + E) + W, where radiative, convective, and evaporative heat losses (R + C + E) were measured by direct calorimetry, work output (W) by ergometry, and heat storage (S) by thermometry. (MR + Man) during the oxygen deficit period was found to be lower than MR during steady state. In the 1st min of exercise, mean mixed work efficiency (aerobic + anaerobic) was 33%, which was greater than aerobic efficiency (26.6%) during steady state. The mean anaerobic efficiency efficiency was 41%. This difference reflects the fact that the energy released by splitting of preformed high-energy bonds (i.e., creatine phosphate) is less than the energy released when high-energy bonds expended during mechanical work are continuously regenerated through oxidative phosphorylation. The reported measurements of overall energy metabolism in man provide means for estimating in vivo the coupling efficiency of physical work (i.e., 41%) as well as the efficiency with which energy released by substrate oxidations is recovered in the form of high-energy bonds (i.e., phosphorylation efficiency = 64%).
Responses of fetal sheep to simulated no-decompression dives
Authors: Stock M. K. , Lanphier E. H. , Anderson D. F. , Anderson L. C. , Phernetton T. M. , Rankin J. H.
Published: December 2017

The effect of simulated standard no-decompression dives to 60 and 100 ft of seawater was tested in 12 near term sheep carrying 16 fetuses. In the immediate postdive period there were no significant changes in fetal blood pressure or fetal placental or renal blood flow, but the maternal blood pressure was elevated and the maternal placental blood flow was depressed. Six surgically prepared fetuses were dived to 100 ft. Five died within 20 min of ascent and the sixth suffered severe cardiac arrhythmia and hypotension. At autopsy all fetuses were observed to have massive bubbling in the arterial system and heart. Five fetuses were dived to 100 ft without surgery. Two were alive 3 h later and no bubbles were present at autopsy, and three were born alive at term. With the 60-ft dives, three fetuses were subjected to surgery and all suffered massive bubbling. Two fetuses were dived to 60 ft without surgery; one was alive after 3 h and the other was born alive at term. We conclude that surgery and monitoring result in the formation of postdive gas bubbles that would not otherwise appear.
Relative responses of aortic body and carotid body chemoreceptors to hypotension
Authors: Lahiri S. , Nishino T. , Mokashi A. , Mulligan E.
Published: December 2017

Responses to acute arterial blood pressure changes of a single or a few chemoreceptor afferents from the aortic body and carotid body at constant arterial blood gases and pH were measured in 16 adult cats. During normocapnic normoxia and moderate hypoxia (arterial oxygen tension of 60 Torr) an induced hypotension of 80 Torr increased strikingly the discharge rate of all aortic chemoreceptors but not of most carotid chemoreceptors; hypotension down to the level of 50 Torr stimulated most carotid chemoreceptors only slightly. Hyperoxia eliminated the stimulatory effect of this degree of hypotension on carotid chemoreceptors; it did not affect aortic chemoreceptors to the same extent. Hypoxia augmented the effect on aortic chemoreceptors more than the effect on carotid chemoreceptors. Thus the effect of hypotension was dependent on arterial oxygen tension. The greater effect of hypotension on aortic body chemoreceptor activity indicates a greater normal circulatory constraint for the aortic body. Accordingly, aortic chemoreceptors are more suited to monitor circulatory changes in O2 flow, and carotid chemoreceptors are more suited to monitor arterial gas pressure changes due to respiration.
Failure of tracheal distension to inhibit breathing in anesthetized dogs
Authors: Lloyd T. C. , Cooper J. A.
Published: December 2017

Using anesthetized spontaneously breathing dogs, we compared the respiratory effects of tracheal distension with the effects of changes in lung volume before and after vagotomy. We used an endotracheal tube with a long cuff to distend the trachea to pressures of 10, 20, and 40 cmH2O. Lung volume increases were imposed by expiratory threshold loading, and volume was decreased by abdominal compression, both of which caused outward rib cage displacement. During expiratory loading, the tidal volume was unchanged but respiratory frequency and minute volume fell and an active expiratory effort appeared; whereas frequency and minute volume rose, but tidal volume fell during abdominal compression. Tracheal distension evoked no discernible change in breathing. Following vagotomy, tidal volume and minute volume fell, and frequency rose slightly, during expiratory loading but abdominal compression was without effect. After vagotomy, 40 cmH2O tracheal distension caused a slight frequency increase. We concluded that the potential role of tracheal deformation in the reflex control of breathing is insignificant in comparison with the other airways.
Enhanced thrombin and plasmin activity with exercise in man
Authors: Hyers T. M. , Martin B. J. , Pratt D. S. , Dreisin R. B. , Franks J. J.
Published: December 2017

We measured products of thrombin and plasmin action and of the platelet release reaction during exercise to determine if the well-known effect of exercise on in vitro coagulation and fibrinolytic tests reflects activity of these systems in vivo. Plasma fibrinopeptide A, produced by thrombin-mediated proteolysis of fibrinogen, increased with graded treadmill and cycle exercise to postexercise levels of 20--30 times resting values. Fibrin/fibrinogen-related D antigen increased in a similar fashion with peak levels at maximal O2 uptake. Plasma-activated partial thromboplastin times fell as fibrinopeptide A levels increased. Unheated fibrin plate lysis areas increased as D antigen concentrations rose, indicating increased release of plasminogen activator. In contrast to activation of the soluble coagulation and fibrinolytic systems, platelet counts and plasma levels of beta-thromboglobulin, a platelet release protein, did not change significantly with exercise. The effect of exercise on thrombin and plasmin was not influenced by prior physical training, but appeared to be less with cycle exercise than with treadmill exercis.
Fetal lung in organ culture. III. Comparison of dexamethasone, thyroxine, and methylxanthines
Authors: Gross I. , Wilson C. M. , Ingleson L. D. , Brehier A. , Rooney S. A.
Published: December 2017

Exposure of explants of fetal rat lung to dexamethasone, thyroxine, or the methylxanthines, aminophylline and caffeine, resulted in a significant increase in the rate of choline incorporation into all the choline-containing phospholipids. Dexamethasone, aminophylline, or caffeine treatment also resulted in an increase in the percentage of radioactivity from [3H]acetate in the surfactant-associated phospholipids, disaturated phosphatidylcholine, and phosphatidylglycerol and a corresponding decrease in the membrane phospholipids. Exposure to thyroxine had different effects. Only aminophylline and caffeine produced an increase in the rate of incorporation of acetate into phospholipid. Differences were also observed in the activities of enzymes of phospholipid synthesis. The activity of cholinephosphate cytidylyltransferase was increased by dexamethasone and that of choline kinase and lysolecithin acyltransferase by aminophylline. Thyroxine had no effect on any of the enzymes examined. All these agents produced a significant decrease in lung glycogen content and a small decrease in the protein-to-DNA ratio. These data indicate that corticosteroids, thyroxine, and the methylxanthines act directly on the fetal lung, but produce different effects and presumably act via different mechanisms.
Relation between flow, curvilinearity, and density dependence of pulmonary pressure-flow curves
Authors: Lisboa C. , Wood L. D. , Jardim J. , Macklem P. T.
Published: December 2017

In nine normal subjects we measured pulmonary pressure-flow curves by ensemble averaging over 20 breaths and solving the equation P = K'V alpha where P is flow-resistive pressure, K' is slope, 5 V is flow, and alpha is curvilinearity. The study was performed at four lung volumes from 37 to 73% of total lung capacity, with the subjects breathing air or HeO2. K' was lower at every lung volume during HeO2 breathing, whereas the exponent alpha was uninfluenced by either lung volume or HeO2 breathing. Although alpha increased with flow rate, comparison of air and HeO2 curves revealed that alpha was not uniquely related to Reynolds' number. Furthermore there was no correlation between curvilinearity and the density dependence of K'. These observations are inconsistent with the general equation P = KV alpha rho alpha-1 mu 2-alpha, where K is a constant related to airway geometry, rho is density and mu is viscosity. (Wood et al., J. Appl. Physiol. 41: 234-244, 1976). The reasons for this discrepancy are unclear, but do not appear to be related to effects of oscillatory flow because alpha was similar from 20 to 90 breaths/min in four subjects. We conclude that the curvilinearity of pulmonary pressure-flow curves is related to flow but independent of gas density and is not explicable solely on the basis of Reynolds' number.
Lung morphometry in guinea pigs acclimated to cold during growth
Authors: Lechner A. J. , Banchero N.
Published: December 2017

Weanling male guinea pigs, Cavia porcellus [initial weight (W) = 200-250 g], were chronically acclimated to 5 degrees C for 2-18 wk before they were killed. Controls were raised at 22 degrees C. Food and water were given ad lib., and growth was the same in both groups. Under pentobarbital anesthesia (30 mg/kg), lungs were fixed by tracheal instillation of glutaraldehyde and processed for electron microscopy. Lung volume (VL, ml) was measured by displacement; alveolar and capillary surface areas (SA and Sc, m2) were determined morphometrically. Regressions of lung variables vs. W at 22 degrees C (range of W = 89-1,274 g) were as follows: VL = 0.175 W0.676, SA = 0.0097 W0.759, and Sc = 0.0055 W0.825; for 5 degrees C animals (range of W = 239-1,074 g): VL = 0.384 W0.584, SA = 0.0334 W0.594, and Sc = 0.032 W0.562. The total arithmetic mean thickness of lung tissue did not vary with W, and averaged 1.39 microns at 22 degrees C and 1.41 microns at 5 degrees C. VL, SA, and Sc are significantly greater in 5 degrees C guinea pigs than in 22 degrees C animals when W = 300-600 g, but are indistinguishable between groups when W > 700 g. Chronic increases in oxygen consumption, which occur with prolonged exposure to cold, result in accelerated lung development in immature guinea pigs toward normal adult dimensions.
Computer determination of thoracic gas volume using plethysmographic "thoracic flow"
Authors: Lorino H. , Harf A. , Atlan G. , Brault Y. , Lorino A. M. , Laurent D.
Published: December 2017

Plotting a line to the variables obtained during a panting maneuver, i.e. thoracic volume and mouth pressure, is the conventional way of computing plethysmographic thoracic gas volume (TGV). This procedure is reliable if the magnitude of the thoracic volume changes is large compared to the drift on the signal; this is one of the major problems in volumetric plethysmography. We propose replacing the thoracic volume signal (Vt) by its time derivative (Vt) and similarly mouth pressure (Pm) with its time derivative (Pm). Drift is thus ruled out, and the magnitude of Vt is preserved when the subject fails to carry out noticeable changes in thoracic volume during the panting, since even then the speed of these changes in thoracic volume remains high. The use of Vt and Pm appeared to be necessary when a minicomputer was connected to a pressure-compensated flow plethysmograph to obtain an automatic calculation of TGV. A regression-line technique applied to signals obtained during the panting was used to find the slope of the relation and thus TGV. However, this slope can only be predicted with less than 5% error if the correlation coefficient is very high (i.e., above 0.99). The analysis of 121 recordings from patients showed that the mean r was only 0.954 when Vt and Pm were used. It increased to 0.993 with Vt and Pm. For the same recordings the comparison of hand-calculated TGV and computer-derived TGV showed a much better agreement for the Vt-Pm method (standard error of the estimate (SEE) = 0.14 liter) than for the Vt-Pm method (SEE = 0.34 liter). These results emphasize that, in contrast to the manual technique, the computer does not adequately handle even a small drift of the thoracic signal. The proposed time-derivative method is therefore useful for a hand calculation, but essential to a reliable computer determination of thoracic gas volume.
An interrupter method for measurement of airway resistance in small animals
Authors: Schlesinger R. B. , Zeccardi A. V. , Monahan J.
Published: December 2017

An interrupter technique for the measurement of airway resistance in spontaneously breathing, unanesthetized small experimental animals is described. The method makes use of an automatic 35-mm camera body to provide the necessary speed for interruption in these rapidly breathing animals and an analog computer to monitor breathing. The system was designed as a screening technique for assessing the irritancy of air pollutants. Initial results using rabbits is presented.
Diaphragmatic function in healthy subjects during partial curarization
Authors: Gal T. J. , Goldberg S. K.
Published: December 2017

Diaphragmatic function estimated by transdiaphragmatic pressure (Pdi) was studied in eight normal subjects during progressive partial paralysis with d-tubocurarine (dTc). Dynamic Pdi was measured during quiet tidal breathing, maximum deep inspiration, and 12-s maximum voluntary ventilation (MVV). Maximum static transdiaphragmatic pressure (Pdimax) was also measured during maximum static inspiratory efforts at four lung volumes. The maximum effect of dTc at a cumulative dose of 0.2 mg/kg abolished head-lift and handgrip ability. Pdimax at functional residual capacity was decreased to 42% of its control value indicating significant diaphragmatic weakness at this level of curarization. The weakness had no inpact on quiet breathing and a moderate effect on maximum inspiration. In either case Pdi represented an increasing fraction of Pdimax. MVV fell significantly before the Pdi during the maneuver decreased. This decreased MVV in curarized subjects reflects upper airway obstruction caused by pharyngeal muscle weakness and the diminished contribution of the other respiratory muscles that are important at high levels of ventilatory effort but more sensitive to effects of dTc.
Innervation of airway smooth muscle in the baboon: evidence for a nonadrenergic inhibitory system
Authors: Middendorf W. F. , Russell J. A.
Published: December 2017

The distribution of receptors and the innervation of intrapulmonary and extrapulmonary baboon airways were examined using tissue bath techniques. Acetylcholine and histamine (via H1-receptors) elicited contractions of all airways. Norepinephrine had both an excitatory (via alpha-receptors) and inhibitory (via beta-receptors) effect in trachealis strips, but in intrapulmonary airways, only inhibitions were observed. Transmural electrical stimulation of resting airways produced sustained contractions that were blocked by either 5 x 10(-6) M tetrodotoxin or 10(-6) M atropine. Electrical stimulation also caused relaxations of histamine-induced contractions in airways pretreated with 10(-6) M atropine and 10(-6) M phentolamine. Relaxations were blocked by 10 x 10(-6) M tetrodotoxin but were unaffected by either 10(-6) M propranolol or 10(-5) M guanethidine. The response of airways to exogenous ATP depended on the degree of active tone. ATP caused contractions in resting airways and airways with moderate tone. In contrast, ATP relaxed airways with high active tone. We conclude that a nonadrenergic system constitute the primary inhibitory innervation of baboon airways, but whether ATP might act as the neurotransmitter could not be determined.
Heterogeneity of local cerebral blood flow-PaCO2 sensitivity in neonatal dogs
Authors: Shapiro H. M. , Greenberg J. H. , Naughton K. V. , Reivich M.
Published: December 2017

Local cerebral blood flow (1-CBF) sensitivity to changes in arterial carbon dioxide tension (PaCO2) was measured in nitrous oxide-anesthetized newborn puppies using a quantitative autoradiographic technique and [14C]antipyrine as a tracer. 1-CBF was determined in four experimental groups at PaCO2 levels of 22, 34, 48, and 65 Torr, respectively. All seven brain areas studied demonstrated 1-CBF sensitivity to altered PaCO2. There were no significant differences (P greater than 0.05) in three subcortical white matter regions (frontal, parietal, occipital) in either 1-CBF or 1-CBF-CO2 sensitivity. With the exception of the thalamus, a reciprocal relationship existed between changes in local cerebral vascular resistance and blood flow. In the thalamus, 1-CBF increased at a greater rate than the 1-CVR reduction. The results show that CBF is heterogeneous in different brain areas of the neonatal dog at normocapnia and that differences in 1-CBF-CO2 sensitivity exist.
Programmable gas mixer for controlling concentration as a function of time
Authors: Jacky J.
Published: December 2017

A device for controlling gas concentration as a function of time according to a predetermined program is described. The apparatus is capable of producing any arbitrary time-varying gas concentration at frequencies up to about 4 Hz and can be set to ultra-low frequencies with excellent accuracy and repeatability. The apparatus consists of a single on/off solenoid valve for each gas in the mixture, all controlled by a microcomputer. The valve is rapidly pulsed open and closed, and the concentration of the corresponding gas in the mixture is proportional to the fraction of the cycle for which the valve remains open. Prior to an experiment, numerical values representing the amplitude of the desired concentration wave form at successive time intervals are entered into the computer memory. When the program is run, the microcomputer successively translates each of these values into a pulse-width modulated signal that opens and closes the valves via optically isolated relays. The processor can also translate an external control signal into the corresponding pulse train, permitting manual or automatic control of the mixture. The apparatus can be assembled in several hours from readily available components costing under $600, including the microcomputer.
Acute small animal preparation--suitable for fetal metabolic studies?
Authors: Lemons J. A. , Perez R. , Schreiner R. L. , Gresham E. L.
Published: December 2017

To determine the immediate effects of the "acute" experimental preparation, 11 near-term pregnant rabbits and 20 fetuses were studied. Blood samples were obtained from the maternal auricular artery, the fetal umbilical vein, and the fetal heart within 90 s of exposure of the uterus by laparotomy. Samples were assayed for pH, O2 and CO2 tension, O2 content, blood urea nitrogen, and plasma glucose. Results indicated that a pronounced fetal acidosis (primarily respiratory) had developed by the time samples were obtained. Further, fetal cardiac glucose levels were significantly elevated above umbilical vein concentrations in 7 of the 20 fetuses. In addition, maternal arterial O2 tension under light pentobarbital anesthesia was significantly less than that found in 35 unanesthetized does (52 vs. 79 Torr, P less than 0.01). All parameters measured varied over a wide range between animals. The results raise serious questions concerning the feasibility of performing and interpreting certain metabolic or cardiorespiratory studies in the acute small animal preparation.
Changes in pulmonary PV characteristics of human subjects at an altitude of 5,366 m
Authors: Mansell A. , Powles A. , Sutton J.
Published: December 2017

We measured lung mechanics in seven young adults at 90 m and again after 9-30 days of exposure to 5,366 m on the summit plateau of Mt. Logan. Increases in peak expiratory flow (by 20%, P less than 0.05) and decreases in total pulmonary resistance (by 30%, P less than 0.02) were consistent with the reduced gas density at high altitude. However, forced expiratory volume in 1 s decreased in four of the seven subjects, suggesting an increase in resistance of small airways or decrease in lung recoil associated with hypoxia. Increase in total lung capacity (TLC), as measured by helium dilution, occurred in each subject and by over 2 liters in two of the subjects (mean increase 17.9%, P less than 0.01). With the increased TLC's taken into account, there were still leftward shifts in the static expiratory pressure-volume (PV) curves with abnormally low lung recoil at 60% TLC, accounting for disproportionately large increases in residual volume (RV/TLC increased from 0.31 to 0.44, P less than 0.005). Prolonged exposure to high altitude is associated with increases in lung volume and shifts in PV curves indistinguishable from those previously described during exercise-induced asthma and during acute isocapnic hypoxia.
Characterization of renal response to prolonged immersion in normal man
Authors: Epstein M. , DeNunzio A. G. , Ramachandran M.
Published: December 2017

During the initial phase of spaceflight, there is a translocation of fluid from the lower parts of the body to the central vascular compartment with a resultant natriuresis, diuresis, and weight loss. Whether this natriuresis and diuresis result in the attainment of a new steady state or whether the circulatory adjustment is incomplete is the subject of continuing controversy. Because water immersion is regarded as an appropriate model for studying the redistribution of fluid that occurs in weightlessness, we carried out an immersion study of relatively prolonged duration in order to characterize the temporal profile of the renal adaptation to central hypervolemia. Twelve normal male subjects underwent an immersion study of 8-h duration in the sodium-replete state. Immersion resulted in marked natriuresis and diuresis which were sustained throughout the immersion period. The failure of that natriuresis and diuresis of immersion to abate or cease despite marked extrcellular fluid volume contraction as evidenced by a mean weight loss of -2.2 ± 0.3 kg suggests that central blood volume was not restored to normal and that some degree of central hypervolemia probably persisted.
Influence of bronchomotor tone on airway dimensions and resistance in excised dog lungs
Authors: Hahn H. L. , Watson A. , Wilson A. G. , Pride N. B.
Published: December 2017

In 10 excised dog lobes we measured total lobar resistance (Rlo) by forced oscillation at various transpulmonary pressures (Ptp) before and after bronchodilators and obtained simultaneous tantalum bronchograms in 5. Mean airway diameter increased up to a Ptp of 30 cmH2O, although the increase was greater between 0 and 10 cmH2O. In contrast, Rlo decreased between 0 and 10 cmH2O but increased again between 10 and 30 cmH2O. At a Ptp of 30 cmH2O, the mean diameter of small airways (〜 2 mm) increased 31%, that of large airways (〞 7 mm) 2% after aerosolized bronchodilators. At a Ptp of 1 cmH2O, increases were 44 and 15%, respectively. Values of Rlo were reduced at all Ptp after bronchodilator, but minimum Rlo occurred at lower Ptp than before, and the absolute increase in Rlo at greater Ptp was preserved. In four additional lobes, we partitioned Rlo using a retrograde catheter. All of the increase in Rlo at large Ptp was peripheral to the retrograde catheter. We conclude that excised lungs have bronchomotor tone that narrows airways even at high Ptp and that loss of tone magnifies the relative increase in Rlo at high Ptp, supporting suggestions that the increase is due to tissue resistance and hysteresis.
Comparison of two- and four-magnetometer methods of measuring ventilation
Authors: Robertson C. H. , Bradley M. E. , Homer L. D.
Published: December 2017

Collection of lymph from the efferent duct of the caudal mediastinal node in sheep is accepted as a reliable method for following lung microvascular fluid and protein filtration. There are significant variations in the efferent duct anatomy, which can complicate the cannulation procedure and, therefore, the success of the preparations. We analyzed the major variations in the efferent duct in 75 consecutive sheep. The majority (59%) had a single efferent duct varying in length, course, and origin fom the caudal mediastinal node; 41% had multiple ducts, often with confluences or bifurcations, making successful cannulation more difficult. It is important to recognize the potential variations in the efferent duct to facilitate useful cannulation.
Physiological adjustments of women to prolonged work during acute hypoxia
Authors: Wagner J. A. , Miles D. S. , Horvath S. M.
Published: December 2017

Five women (23-32 yr) performed bicycle work in a hypobaric chamber for 2 h at 41% of their respective altitude maximal oxygen uptakes (VO2) at 758, 586, 523, and 446 Torr barometric pressures (PB). Steady-state VO2 was achieved within 5 min work at all altitudes. Pulmonary ventilation (29.2 +/- 1.9 (mean +/- SE) 1/min, BTPS), respiratory rate (22 +/- 2 breaths/min), cardiac output (8.5 +/- 1.4 1/min), heart rate (115 +/- 6 beats/min), and stroke volume (75 +/- 13 ml) were similar at all altitudes, but time-related changes differed with altitude. Blood lactates did not change with work duration and were similar at 758 and 586 Torr PB but progressively elevated at 523 and 446 Torr. Blood norepinephrine, measured only at 758 and 446 Torr PB, increased with work but not altitude; epinephrine increased only at altitude. Norepinephrine levels and respiratory, cardiovascular, and thermoregulatory functions were essentially dependent on relative work load; blood lactates and epinephrine levels were not. Many physiological functions in these women performing sustained light work during acute altitude exposure were remarkably stable in contrast to previously reported studies on men.
Nonhomogeneous alveolar pressure swings in the presence of airway closure
Authors: Brown R. , Scharf S. , Ingram R. H.
Published: December 2017

When thoracic gas volume (TGV) is determined plethysmographically, it is assumed that the alveolar pressure swings are homogeneous and are appropriately represented by pressure swings at the mouth. However, recent studies have demonstrated differences in total lung capacities derived from TGV measurements made at different levels in the vital capacity. These differences suggested that, in the presence of airway closure, alveolar pressure swings may be nonhomogeneous during a TGV determination. This possibility was tested in six dogs. Pressure at the airway opening (ao) was measured from an endotracheal catheter. A balloon-tipped catheter was passed into the right lower lobe (RLL) bronchus for measurement of RLL pressure. delta PRLL -- delta Pao was monitored during inspiratory efforts with the airway opening occluded. With the RLL balloon inflated, delta PRLL always exceeded delta Pao by an amount averaging 8.2%. Induction of a pneumothorax eliminated all differences between delta PRLL and delta Pao. Thus, during a TGV measurement, the chest wall may apply to the lungs nonhomogeneous forces that, in the presence of airway closure (e.g., chronic obstructive pulmonary disease and asthma) would result in nonhomogeneous alveolar pressure swings and potentially significant errors in the plethysmographic determination of TGV.