bluuebunny/crossref_metadata_2025 huggingface dataset:
Time course of bronchoconstriction induced by dry gas hyperpnea in guinea pigs
Authors: Ray D. W. , Garland A. , Hernandez C. , Eappen S. , Alger L. , Solway J.
Published: December 2017

We examined the effects of hyperpnea duration and abrupt changes in inspired gas heat and water content on the magnitude and time course of hyperpnea-induced bronchoconstriction (HIB) in anesthetized mechanically ventilated male Hartley guinea pigs. In 12 animals subjected to 5, 10, and 15 min (random order) of dry gas isocapnic hyperpnea [tidal volume (VT) 4-6 ml, 150 breaths/min) followed by quiet breathing of humidified air (VT 2-3 ml, 60 breaths/min), severe bronchoconstriction developed only after the cessation of hyperpnea; the magnitude of respiratory system resistance (Rrs) increased with the duration of dry gas hyperpnea [peak Rrs 1.0 +/- 0.2, 1.8 +/- 0.3, and 2.3 +/- 0.3 (SE) cmH2O.ml-1.s, respectively]. Seven other guinea pigs received, in random order, 10 min of warm humidified gas hyperpnea, 10 min of room temperature dry gas hyperpnea, and 5 min of dry gas hyperpnea immediately followed by 5 min of warm humidified gas hyperpnea. After each hyperpnea period, the animal was returned to quiet breathing of humidified gas. Rrs rose appreciably after the 10 min of dry and 5 min of dry-5 min of humidified hyperpnea challenges (peak Rrs 1.3 +/- 0.2 and 0.7 +/- 0.2 cmH2O.ml-1.s, respectively) but not after 10 min of humidified hyperpnea (0.2 +/- 0.04 cmH2O.ml-1.s). An additional five animals received 10 min of room temperature dry gas hyperpnea followed by quiet breathing of warm humidified air and 10 min of room temperature dry gas hyperpnea followed by 30 min of warm humidified gas hyperpnea in random order.(ABSTRACT TRUNCATED AT 250 WORDS)
Air travel across four time zones in college swimmers
Authors: O'Connor P. J. , Morgan W. P. , Koltyn K. F. , Raglin J. S. , Turner J. G. , Kalin N. H.
Published: December 2017

Eighteen female and 22 male college swimmers were flown across four time zones in east-to-west (E-W) and west-to-east (W-E) directions. A pre- and postflight paced swim of 182.9 m at an intensity equal to 90% of the swimmers' maximal velocity was completed, and salivary cortisol, heart rate (HR), and rated perceived exertion were measured. Blood pressure, HR, muscle soreness, and mood were also assessed at rest on the day before and on the day after travel. Because training volumes for both females and males were greater (P less than 0.001) in the week before W-E than E-W travel, the W-E and E-W data were analyzed separately. Two-way repeated-measures analyses of variance revealed that pre- and postexercise cortisol decreased after E-W travel and increased after W-E travel in comparison to preflight values. Resting and exercise HR responses to air travel were small in magnitude, and their significance depended on the direction of travel. Effort sense was not altered by air travel, but significant (P less than 0.001) improvements in mood and reductions in muscle soreness were observed after E-W and W-E travel for both genders. It was concluded that 1) female and male college swimmers have similar responses to air travel and 2) air travel across four time zones during heavy swim training does not have negative physiological, perceptual, or affective consequences.
Dynamic behavior of excised dog rib cage: dependence on muscle
Authors: Kikuchi Y. , Stamenovic D. , Loring S. H.
Published: December 2017

To assess the contribution of the rib cage to chest wall elastance and hysteresis, we measured force-displacement behavior of the isolated canine rib cage during sinusoidal forcing of the sternum in the midsagittal plane at low frequencies (0.02-2.0 Hz). Elastance of the rib cage was nearly invariant with frequency of forcing from 0.02 to 1.0 Hz and decreased with increasing amplitude. Hysteresis, the width of the force-displacement loop at middisplacement (zero displacement), was nearly constant with frequency below 1.0 Hz and increased with increasing amplitude of forcing. Removal of muscle reduced elastance and hysteresis of the rib cage substantially. The data suggest that the excised dog rib cage shows dynamic behavior similar to that of the intact human rib cage and chest wall and that respiratory muscle is responsible for a major part of the behavior of the passive chest wall. We also calculated the major and minor stiffnesses in the sagittal plane, which differed by a factor of 3-11, and their directions lay close to the dorsoventral and cephalocaudal axes, respectively. Removal of muscle reduced the stiffnesses but did not change their directions. Thus, although respiratory muscles impede motion in the sagittal plane, they do not alter its pattern.
Effect of slowly increasing elastic load on breathing in conscious humans
Authors: Puddy A. , Younes M.
Published: December 2017

Because the detection of added loads is a function of the step change in load relative to background level of load (Weber's law), we reasoned that detection may be delayed if the load is increased in very small steps over a protracted period. This would permit the study of subliminal load responses over a greater range than would otherwise be possible. In 13 healthy males, an external elastic load (delta E) was added in very small steps (load increased every few seconds) such that delta E increased from zero to 6.0 cmH2O/l in 18 min. Each subject underwent a control study in which an identical protocol was followed but no load was added. Five subjects sensed the load after a variable period of load application. Their results were discarded. In the remaining eight subjects, there was no perception of increased load throughout the 18 min. By comparison with the control studies in the same subjects, there was a progressive reduction in tidal volume and breath duration with loading. To assess the response to an increase in load associated with perception, in five of the eight "nonsensers" the load was suddenly doubled (delta E = 6 cmH2O/l) at the end of the 18 min of progressive nonsensed loading. This evoked perception in all subjects and was associated with highly variable responses in tidal volume and breath duration. We conclude that tachypnea associated with elastic loading in conscious humans is a reflex response that is facilitated by consciousness but does not require perception.
Maximum airflow through the nose in humans
Authors: Pertuze J. , Watson A. , Pride N. B.
Published: December 2017

Inspiratory and expiratory flow via the nose and via the mouth during maximum-effort vital capacity (VC) maneuvers have been compared in 10 healthy subjects. Under baseline conditions maximum flow via the nose was lower than that via the mouth in the upper 50-60% of the VC on expiration and throughout the VC on inspiration. The mean ratio of maximum inspiratory to maximum expiratory flow at mid-VC was 1.38 during mouth breathing and 0.62 during nasal breathing. Inspiratory flow limitation with no increase in flow through the nose as driving pressure was increased above a critical value (usually between 12 and 30 cmH2O) was found in all six subjects studied. Stenting the alae nasi in seven subjects increased peak flow via the nose from a mean of 3.49 to 4.32 l/s on inspiration and from 4.83 to 5.61 l/s on expiration. Topical application of an alpha-adrenergic agonist in seven subjects increased mean peak nasal flow on inspiration from 3.25 to 3.89 l/s and on expiration from 5.03 to 7.09 l/s. Further increases in peak flow occurred with subsequent alan stenting. With the combination of stenting and topical mucosal vasoconstriction, nasal peak flow on expiration reached 81% and, on inspiration, 79% of corresponding peak flows via the mouth. The results demonstrate that narrowing of the alar vestibule and the state of the mucosal vasculature both influence maximum flow through the nose; under optimal conditions, nasal flow capacity is close to that via the mouth.
Inspiratory elevation of the ribs in the dog: primary role of the parasternals [published errata appear in J Appl Physiol 1991 Aug;71(2):following Table of Contents and 1991 Dec;71(6):following Author Index]
Authors: De Troyer A.
Published: December 2017

To assess the relative contributions of the different groups of inspiratory intercostal muscles to the cranial motion of the ribs in the dog, we have measured the axial displacement of the fourth rib and recorded the electromyograms of the parasternal intercostal, external intercostal, and levator costae in the third interspace in 15 anesthetized animals breathing at rest. In eight animals, the parasternal intercostals were denervated in interspaces 1-5. This procedure caused a marked increase in the amount of external intercostal and levator costae inspiratory activity, and yet the inspiratory cranial motion of the rib was reduced by 55%. On the other hand, the external intercostals in interspaces 1-5 were sectioned in seven animals, and the reduction in the cranial rib motion was only 22%; the amount of parasternal and levator costae activity, however, was unchanged. When the parasternals in these animals were subsequently denervated, the levator costae inspiratory activity increased markedly, but the inspiratory cranial motion of the rib was abolished or reversed into an inspiratory caudal motion. These studies thus confirm that, in the dog breathing at rest, the parasternal intercostals have a larger role than the external intercostals and levator costae in causing the cranial motion of the ribs during inspiration. A quantitative analysis suggests that the parasternal contribution is approximately 80%.
Effect of vasoconstriction on longitudinal distribution of pulmonary vascular pressure and volume
Authors: Dawson C. A. , Linehan J. H. , Rickaby D. A. , Krenz G. S.
Published: December 2017

We used an improved version of the low-viscosity bolus method to evaluate longitudinal (arterial-to-venous) differences in the sensitivity of the dog lung lobe vasculature to selected vasoconstrictor stimuli, including hypoxia, and serotonin, histamine, and norepinephrine infusions. This method revealed a bimodal distribution of local vascular resistance vs. cumulative vascular volume under the zone 3 conditions studied. Our interpretation of the two modes of relatively high resistance is that they correspond to high resistance per unit volume segments of the arteries and veins upstream and downstream from the relatively low resistance per unit volume capillary bed. Thus an increase in the height of the upstream and downstream modes of the resistance distribution suggests constriction in small arteries and veins, respectively. Horizontal displacement of the modes along the cumulative volume axis suggests changes in the distribution of volume among the arteries, veins, and capillary bed. By use of these criteria, the results are consistent with the concept that each of the vasoconstrictor stimuli studied had a different longitudinal response pattern. Hypoxia constricted mainly small arteries, whereas serotonin constricted small and large arteries. Histamine constricted large and small veins, and norepinephrine constricted large and small veins and arteries.
Muscle structure and performance capacity of Himalayan Sherpas
Authors: Kayser B. , Hoppeler H. , Claassen H. , Cerretelli P.
Published: December 2017

The ultrastructure of the vastus lateralis muscle of Sherpas from Nepal [5 males; age 28 +/- 2.8 (SD) yr, indirect maximal O2 consumption 48.5 +/- 5.4 ml.kg(-1).min(-1)] was assessed and compared with those of sedentary lowlanders and of Caucasian climbers before and after high-altitude exposure. The mean cross-sectional area of the fibers was 3,186 +/- 521 microns2, i.e., similar to those of Caucasian elite high-altitude climbers (3,108 +/- 303 microns2) and a group of climbers after a 6- to 8-wk sojourn at 5,000-8,600 m (3,360 +/- 580 microns2) but significantly (P less than 0.05) smaller than that of unacclimatized climbers (4,170 +/- 710 microns2) and slightly, although not significantly, lower than that of sedentary lowlanders (3,640 +/- 260 microns2). The number of capillaries per square millimeter of muscle cross section was 467 +/- 22, not significantly smaller than those of climbers on return from a Himalayan expedition (538 +/- 89) and elite high-altitude climbers (542 +/- 127) but significantly (P less than 0.05) greater than that of sedentary lowlanders (387 +/- 25). The volume density of mitochondria was 3.96 +/- 0.54%, significantly (P less than 0.05) less than the values found for any other investigated group, including sedentary subjects at sea level (4.74 +/- 0.30%). It is concluded that Sherpas, like acclimatized Caucasian climbers, are characterized by 1) facilitated convective and diffusive muscle O2 flow conditions and 2) a higher maximal O2 consumption-to-mitochondrial volume ratio than lowlanders despite a reduced mitochondrial volume density.
Shivering onset, metabolic response, and convective heat transfer during cold air exposure
Authors: Tikuisis P. , Bell D. G. , Jacobs I.
Published: December 2017

The onset and intensity of shivering of various muscles during cold air exposure are quantified and related to increases in metabolic rate and convective heat loss. Thirteen male subjects resting in a supine position and wearing only shorts were exposed to 10 degrees C air (42% relative humidity and less than 0.4 m/s airflow) for 2 h. Measurements included surface electromyogram recordings at six muscle sites representing the trunk and limb regions of one side of the body, temperatures and heat fluxes at the same contralateral sites, and metabolic rate. The subjects were grouped according to lean (LEAN, n = 6) and average body fat (NORM, n = 7) content. While the rectal temperatures fluctuated slightly but not significantly during exposure, the skin temperature decreased greatly, more at the limb sites than at the trunk sites. Muscles of the trunk region began to shiver sooner and at a higher intensity than those of the limbs. The intensity of shivering and its increase over time of exposure were consistent with the increase in the convective heat transfer coefficient calculated from skin temperatures and heat fluxes. Both the onset of shivering and the magnitude of the increase in metabolic rate due to shivering were higher for the LEAN group than for the NORM group. A regression analysis indicates that, for a given decrease in mean skin temperature, the increase in metabolic rate due to shivering is attenuated by the square root of percent body fat. Thus the LEAN group shivered at higher intensity, resulting in higher increases in metabolic heat production and convective heat loss during cold air exposure than did the NORM group.
Applications of fractal analysis to physiology
Authors: Glenny R. W. , Robertson H. T. , Yamashiro S. , Bassingthwaighte J. B.
Published: December 2017

This review describes approaches to the analysis of fractal properties of physiological observations. Fractals are useful to describe the natural irregularity of physiological systems because their irregularity is not truly random and can be demonstrated to have spatial or temporal correlation. The concepts of fractal analysis are introduced from intuitive, visual, and mathematical perspectives. The regional heterogeneities of pulmonary and myocardial flows are discussed as applications of spatial fractal analysis, and methods for estimating a fractal dimension from physiological data are presented. Although the methods used for fractal analyses of physiological data are still under development and will require additional validation, they appear to have great potential for the study of physiology at scales of resolution ranging from the microcirculation to the intact organism.
Effect of atelectasis and surface tension on pulmonary vascular compliance
Authors: Nelin L. D. , Rickaby D. A. , Linehan J. H. , Dawson C. A.
Published: December 2017

The effects of atelectasis and surface tension on the vascular volume and compliance in an isolated perfused dog lung lobe were studied using vascular occlusion and indicator-dilution methods. Measurements were made during atelectasis and again after the lobes were inflated with either a gas mixture (air) or 0.9% saline. Inflation with air resulted in a 20% increase in vascular volume (P less than 0.02), whereas saline inflation had no effect on vascular volume. Inflation with either air or saline increased static vascular compliance by approximately 58% (P less than 0.001) and dynamic vascular compliance by approximately 85% (P less than 0.001). The larger dynamic compliance in the inflated lobes appears to have been mainly due to a larger microvascular compliance. The results suggest that atelectasis can result in a stiffer pulmonary capillary bed. This effect appears to be due primarily to the reconfiguration of the lung tissue structure, because replacing the air with an incompressible fluid did not have the same effect.
Thyroarytenoid muscle activity during loaded and nonloaded breathing in adult humans
Authors: Insalaco G. , Kuna S. T. , Costanza B. M. , Catania G. , Cibella F. , Bellia V.
Published: December 2017

Previous fiber-optic studies in humans have demonstrated narrowing of the glottic aperture in expiration during application of expiratory resistive loads. Nine healthy subjects were studied to determine the effect of expiratory resistive loads on the electromyographic activity of the thyroarytenoid (TA) muscle, a vocal cord adductor. Four of the nine subjects also underwent the application of inspiratory resistive loads and voluntary prolongation of either inspiratory (TI) or expiratory (TE) time. TA activity was recorded by intramuscular hooked-wire electrodes. During quiet breathing in all subjects, the TA was phasically active on expiration and often tonically active throughout the respiratory cycle. TA expiratory activity progressively increased with increasing levels of expiratory load. Inspiratory loads resulted in increased TA "inspiratory" activity. Voluntary prolongation of TE to times similar to those reached during loaded breathing induced increases in TA expiratory activity similar to those reached during the loaded state. Voluntary prolongation of TI was associated with an increase in TA inspiratory activity. Similar increases in TI during inspiratory loading or voluntary conditions were associated with comparable increases in TA inspiratory activity in three of the four subjects. In conclusion, increased activation of TA during the application of expiratory resistive loads implies that the reported narrowing of glottic aperture during expiratory loading is an active phenomenon. Changes in activation of the TA with resistive loads appear to be related to changes in respiratory pattern.
Respiratory responses to aortic and carotid chemoreceptor activation in the dog
Authors: Hopp F. A. , Seagard J. L. , Bajic J. , Zuperku E. J.
Published: December 2017

Respiratory responses arising from both chemical stimulation of vascularly isolated aortic body (AB) and carotid body (CB) chemoreceptors and electrical stimulation of aortic nerve (AN) and carotid sinus nerve (CSN) afferents were compared in the anesthetized dog. Respiratory reflexes were measured as changes in inspiratory duration (TI), expiratory duration (TE), and peak averaged phrenic nerve activity (PPNG). Tonic AN and AB stimulations shortened TI and TE with no change in PPNG, while tonic CSN and CB stimulations shortened TE, increased PPNG, and transiently lengthened TI. Phasic AB and AN stimulations throughout inspiration shortened TI with no changes in PPNG or the following TE; however, similar phasic stimulations of the CB and CSN increased both TI and PPNG and decreased the following TE. Phasic AN stimulation during expiration decreased TE and the following TI with no change in PPNG. Similar stimulations of the CB and CSN decreased TE; however, the following TI and PPNG were increased. These findings differ from those found in the cat and suggest that aortic chemoreceptors affect mainly phase timing, while carotid chemoreceptors affect both timing and respiratory drive.
Differences between VO2 maxima of twitch and tetanic contractions are related to blood flow
Authors: Brechue W. F. , Barclay J. K. , O'Drobinak D. M. , Stainsby W. N.
Published: December 2017

The purpose of this investigation was to compare oxygen uptake (VO2) and fatigue characteristics of isotonic tetanic contractions with those observed during isotonic twitches in dog gastrocnemius-plantaris muscle. Tetanic contractions (1/s, 200-ms trains of 50 impulses/s) elicited a peak VO2 of 9.01 +/- 0.42 mumol.g-1.min-1, which declined 29% in 30 min. The peak was significantly lower during 4/s twitches (6.23 +/- 0.36 mumol.g-1.min-1), but the rate of decline was similar. Peak blood flow (Q) was 37% higher and decreased more slowly during tetanic than twitch contractions. VO2/Q and VO2/venous PO2 were similar in both groups at peak VO2 and later declined or remained constant over time. Power was significantly greater with tetanic contractions with the relative decline between 3 and 30 min similar in both groups (32 and 37%). In conclusion, tetanic contractions result in significantly higher VO2 and power than do twitch contractions. This was derived primarily from increased Q because the arteriovenous O2 difference was similar. A significant determinant of the difference in Q between twitch and tetanic contractions is mechanical hindrance of Q. There is relatively more time for unhindered flow in the tetanic contractions. In electrically stimulated muscles, maximal VO2 is related to Q and reflects mainly Q through the muscle rather than the VO2 capacity of the muscle.
Frequency characteristics of airway and tissue impedances in respiratory diseases
Authors: Mishima M. , Kawakami K. , Higashiya K. , Fukunaga T. , Ooka T. , Kuno K.
Published: December 2017

We measured the frequency characteristics (at 10–40 Hz) of airway (Za) and tissue (Zt) impedances in cases of chronic obstructive pulmonary disease [asthmatic bronchitis (AB), chronic pulmonary emphysema (CPE)] and interstitial pneumonitis (IP) by use of an improved random noise oscillation and body box method. The results were then compared with those obtained for normal subjects. The real part of Za was markedly elevated in patients with AB but only slightly elevated in those with CPE. To interpret these data we used an electromechanical analogue including serial inhomogeneity with shunt impedance. From this model we concluded that AB causes both the central and peripheral airway resistances to increase, while CPE brings about a rise mainly in peripheral resistance. In IP patients, only the imaginary part of Zt decreased, which might reflect the decrease in both lung and chest wall compliance. In CPE patients, but not in AB patients, the real part of Zt fell. These data were consistent with the assumption that the decrease in mass per unit volume of lung tissue and hyperinflation of the chest wall in CPE patients might lower the tissue resistances.
Effects of pulmonary restriction on hypercapnic responses of heart-lung transplant recipients
Authors: Duncan S. R. , Kagawa F. T. , Kramer M. R. , Starnes V. A. , Theodore J.
Published: December 2017

Previous studies of hypercapnic ventilatory responses (HCVR) in human heart-lung transplant recipients (HLTX) have yielded conflicting results. We compared the HCVR of restricted transplant recipients (HLTX-R) to recipients with normal pulmonary function (HLTX-N), and normal controls (C). HLTX-R exhibited limited tidal volume responses, whereas their frequency responses were essentially identical to those of other subjects. Accordingly, HCVR of HLTX-R (1.45 +/- 0.59 l.min-1.Torr CO2(-1)) were significantly depressed compared with both HLTX-N and C (2.90 +/- 0.55 vs 3.05 +/- 1.23, respectively) (P less than 0.02). Despite undoubtedly greater ventilatory impedances, airway (mouth) occlusion pressure responses (Pm0.1) during hypercarbia of HLTX-R (0.46 +/- 0.28 cmH2O) were similar to those of C (0.43 +/- 0.20) and paradoxically blunted compared with HLTX-N (0.83 +/- 0.36) (P less than 0.02). We conclude that pulmonary reflexes are superfluous for maintenance of HCVR in HLTX with normal respiratory mechanics, whereas the presence of moderate restriction results in profound depression of CO2 responses among these subjects.
Methods for intracellular recording from hippocampal brain slices under high helium pressure
Authors: Southan A. P. , Wann K. T.
Published: December 2017

A method for intracellular recording from rat hippocampal brain slices under helium pressure is described. The preparation is mounted on a horizontal mobile platform that is rolled into the pressure chamber and can be viewed at pressure. Remote manipulation of the glass microelectrodes is achieved by a high-resolution electrically driven commercially available system. The slice is superfused continuously from a closed system within the chamber. Temperature is maintained at 37 degrees C and PO2 at 0.5 atm within the pressure chamber. A pressure of 200 ATA can be obtained, although thus far recordings have been made up to only 130 ATA. The experiments demand that a number of sample recordings be made from the same slice at both ambient and high pressure, and tests have proved that, although difficult, this can be achieved. The resting membrane potential, the current-voltage relationship, and the action potential responses to short (8 ms), medium (80 ms), and long (800 ms) depolarizing current pulses have all been measured in CA1 pyramidal neurons.
Measurement of total respiratory impedance in infants by the forced oscillation technique
Authors: Desager K. N. , Buhr W. , Willemen M. , van Bever H. P. , de Backer W. , Vermeire P. A. , Landser F. J.
Published: December 2017

The forced oscillation technique according to Landser et al. (J. Appl. Physiol. 41:101–106, 1976) was modified for use in infants. Adaptations, including a flexible tube to connect the infant to the measuring system and a bias flow to avoid rebreathing, did not influence impedance values. The linearity of the respiratory system was assessed and confirmed by 1) applying pseudo-random noise oscillations at three different amplitudes to 7 infants and 2) comparing in 12 infants impedance values obtained with pseudo-random noise and with sinusoidal oscillations at 12 and 32 Hz. Intersubject variability, averaged for all frequencies, was 6%. In 17 infants the relative error (+/- SD) between two series of five measurements within a time interval of 15 min was 0.5 +/- 5.7%. No statistically significant difference was found between impedance values before and after repositioning of the infant's head, whereas rotation resulted in a decrease in resistance and no effect on reactance. Our results indicate that the infant-adapted forced pseudo-random noise oscillation technique has the potential to give valuable information about ventilatory lung function in infants.
Effect of alkalosis on maximum oxygen uptake in rats acclimated to simulated altitude
Authors: Gonzalez N. C. , Zamagni M. , Clancy R. L.
Published: December 2017

The objective of the present experiments was to determine whether prevention or moderation of exercise acidosis would influence arterial blood oxygenation and exercise capacity in hypoxia. The effect of administration of 0.3 M NaHCO3 (3 ml/100 g) on maximum O2 uptake (VO2max) and arterial blood oxygenation was determined in rats acclimated to simulated altitude (370–380 Torr barometric pressure) for 3 wk (HxBic) and in normoxic littermates (NxBic). Controls were simulated-altitude (HxNaCl) and normoxic rats (NxNaCl) given 0.3 M NaCl. Inspiratory PO2 during treadmill exercise was approximately 70 Torr for hypoxic rats and 140–145 Torr for normoxic rats. VO2max was 18% higher in HxBic than in HxNaCl (62.8 + 1.6 vs. 53.1 + 1.0 ml STPD.min-1.kg-1, respectively, P less than 0.05) and only 8% higher in NxBic than in NxNaCl (74.0 + 1.1 vs. 68.7 + 1.5 ml STPD.min-1.kg-1, respectively, P less than 0.05). Exercise in HxNaCl resulted in a decrease in arterial O2 concentration (CaO2), which was largely due to a pH-induced decrease in O2 saturation of arterial blood, and occurred despite an increase in arterial PO2. NaHCO3 moderated the acidosis of exercise and largely attenuated the decrease in CaO2. The effects of acidosis and bicarbonate on CaO2 were much less evident in the normoxic controls. There was an almost linear relationship between VO2max and the corresponding CaO2 for all four groups, suggesting that the effect of NaHCO3 on VO2max may be related to moderation of the decrease in CaO2.
Carrying loads with springy poles
Authors: Kram R.
Published: December 2017

People throughout Asia use springy bamboo poles to carry the loads of everyday life. These poles are a very compliant suspension system that allows the load to move along a nearly horizontal path while the person bounces up and down with each step. Could this be an economical way to carry loads inasmuch as no gravitational work has to be done to lift the load repeatedly? To find out, an experiment was conducted in which four male subjects ran at 3.0 m/s on a motorized treadmill with no load and while carrying a load equal to 19% body wt with compliant poles. Oxygen consumption rate, vertical ground reaction force, and the force exerted by the load on the shoulders were measured. Oxygen consumption rate increased by 22%. The same increase has previously been observed when loads are carried with a backpack. Thus compliant poles are not a particularly economical method of load carriage. However, pole suspension systems offer important advantages: they minimize peak shoulder forces and loading rates. In addition, the peak vertical ground reaction force is only slightly increased above unloaded levels when loads are carried with poles.
Blood rheology in acute mountain sickness and high-altitude pulmonary edema
Authors: Reinhart W. H. , Kayser B. , Singh A. , Waber U. , Oelz O. , Bartsch P.
Published: December 2017

The role of blood rheology in the pathogenesis of acute mountain sickness and high-altitude pulmonary edema was investigated. Twenty-three volunteers, 12 with a history of high-altitude pulmonary edema, were studied at low altitude (490 m) and at 2 h and 18 h after arrival at 4,559 m. Eight subjects remained healthy, seven developed acute mountain sickness, and eight developed high-altitude pulmonary edema. Hematocrit, whole blood viscosity, plasma viscosity, erythrocyte aggregation, and erythrocyte deformability (filtration) were measured. Plasma viscosity and erythrocyte deformability remained unaffected. The hematocrit level was lower 2 h after the arrival at high altitude and higher after 18 h compared with low altitude. The whole blood viscosity changed accordingly. The erythrocyte aggregation was about doubled 18 h after the arrival compared with low-altitude values, which reflects the acute phase reaction. There were, however, no significant differences in any rheological parameters between healthy individuals and subjects with acute mountain sickness or high-altitude pulmonary edema, either before or during the illness. We conclude that rheological abnormalities can be excluded as an initiating event in the development of acute mountain sickness and high-altitude pulmonary edema.
Effect of lung volume and positional changes on pulmonary diffusing capacity and its components
Authors: Stam H. , Kreuzer F. J. , Versprille A.
Published: December 2017

Normal subjects have a larger diffusing capacity normalized per liter alveolar volume (DL/VA) in the supine than in the sitting position. Body position changes total lung diffusing capacity (DL), DL/VA, membrane conductance (Dm), and effective pulmonary capillary blood volume (Qc) as a function of alveolar volume (VA). These functions were studied in 37 healthy volunteers. DL/VA vs. VA yields a linear relationship in sitting as well as in supine position. Both have a negative slope but usually do not run parallel. In normal subjects up to 50 yr old DL/VA and DL increased significantly when subjects moved from a sitting to a supine posture at volumes between 50 and 100% of total lung capacity (TLC). In subjects greater than 50 yr old the responses of DL/VA and DL to change in body position were not significant at TLC. Functional residual capacity (FRC) decreases and DL/VA increases in all normal subjects when they change position from sitting to supine. When DL/VA increases more than predicted from the DL/VA vs. VA relationship in a sitting position, we may infer an increase in effective Qc in the supine position. In 56% of the volunteers, supine DL was smaller than sitting DL despite a higher DL/VA at FRC in the supine position because of the relatively larger decrease in FRC. When the positional response at TLC is studied, an estimation obtained accidentally at a volume lower than TLC may influence results. Above 80% of TLC, Dm decreased significantly from sitting to supine. Below this lung volume the decrease was not significant. The relationship between Qc and VA was best described by a second-order polynomial characterized by a maximum Qc at a VA greater than 60% of TLC. Qc was significantly higher in the supine position than in the sitting position, but the difference became smaller with increasing age. In observing the sitting and supine positions, we saw a decrease in maximum Qc normalized per square meter of body surface area with age.
Regional deformation of the canine diaphragm
Authors: Pean J. L. , Chuong C. J. , Ramanathan M. , Johnson R. L.
Published: December 2017

To follow regional deformation of the diaphragm in dogs, radiopaque markers were implanted under surgical anesthesia into different anatomic regions of the muscle in triangular arrays (approximately 1 cm to a side). After recovery from surgery, changes in area and shape of the triangles were followed with biplane cinefluorography during quiet breathing and during inspiratory efforts against an occluded airway (Mueller maneuvers). From changes in shape of the triangles during contraction, area changes were decomposed into a major direction and magnitude of shortening (Eg1) and a minor length change (Eg2) perpendicular to Eg1, both expressed as a fraction of initial length at end expiration. With the use of these techniques, systematic differences in regional area change were observed in different parts of the diaphragm during inspiratory efforts at different lung volumes. Regional area always decreased during contraction in the crural and midcostal zones of apposition to the rib cage. Area decreased less and often increased during inspiratory efforts in the costal dome near the central tendon and in the costal region near its rib cage insertion. Differences in regional area change were not due to differences in the Eg1 in different parts of the diaphragm but were a consequence of differences in widening of the muscle along Eg2 perpendicular to the direction of Eg1. As lung volume was passively increased above functional residual capacity, regional area decreased in all parts of the diaphragm except in the costal regions near rib cage insertion, where area increased.
Distensibility of small arteries of the dog lung
Authors: al-Tinawi A. , Madden J. A. , Dawson C. A. , Linehan J. H. , Harder D. R. , Rickaby D. A.
Published: December 2017

To obtain in situ measurements of the distensibility of small (100- to 1,000-microns-diam) pulmonary arterial vessels of the dog lung, X-ray angiograms were obtained from isolated lung lobes with the vascular pressure adjusted to various levels. The in situ diameter-pressure relationships were compared with the diameter-pressure relationships for small arteries that were dissected free from the lungs and cannulated with small glass pipettes for the measurement of diameter and transmural pressure. The diameter-vascular or diameter-transmural pressure curves from both in situ and cannulated vessels were sufficiently linear in the pressure range studied (0–30 Torr) that they could be characterized by linear regression to obtain estimates of D0, the diameter at zero vascular pressure, and beta, the change in diameter (micron) per Torr change in pressure. The vessel distensibility coefficient (alpha) was defined as alpha = beta/D0. The mean values of alpha were approximately 2.0 +/- 0.8%/Torr (SD) for the in situ vessels and 1.7 +/- 0.6%/Torr for the cannulated vessels, with no statistically significant difference between the two methods. The influence of vasoconstriction elicited by serotonin was evaluated in the in situ vessels. Serotonin-induced vasoconstriction caused a decrease in D0 and little change in alpha.
Skeletal muscle changes after endurance training at high altitude
Authors: Bigard A. X. , Brunet A. , Guezennec C. Y. , Monod H.
Published: December 2017

The effects of endurance training on the skeletal muscle of rats have been studied at sea level and simulated high altitude (4,000 m). Male Wistar rats were randomly assigned to one of four groups: exercise at sea level, exercise at simulated high altitude, sedentary at sea level, and sedentary at high altitude (n = 8 in each group). Training consisted of swimming for 1 h/day in water at 36 degrees C for 14 wk. Training and exposure to a high-altitude environment produced a decrease in body weight (P less than 0.001). There was a significant linear correlation between muscle mass and body weight in the animals of all groups (r = 0.89, P less than 0.001). High-altitude training enhanced the percentage of type IIa fibers in the extensor digitorum longus muscle (EDL, P less than 0.05) and deep portions of the plantaris muscle (dPLA, P less than 0.01). High-altitude training also increased the percentage of type IIab fibers in fast-twitch muscles. These muscles showed marked metabolic adaptations: training increased the activity levels of enzymes involved in the citric acid cycle (citrate synthase, CS) and the beta-oxidation of fatty acids (3 hydroxyacyl CoA dehydrogenase, HAD). This increase occurred mainly at high altitude (36 and 31% for HAD in EDL and PLA muscles; 24 and 31% for CS in EDL and PLA muscles). Training increased the activity of enzymes involved in glucose phosphorylation (hexokinase). High-altitude training decreased lactate dehydrogenase activity. Endurance training performed at high altitude and sea level increased the isozyme 1-to-total lactate dehydrogenase activity ratio to the same extent.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of pulsatile flow on microvascular resistance in adult rabbit lungs
Authors: Raj J. U. , Kaapa P. , Anderson J.
Published: December 2017

We have determined the effect of pulsatile flow on segmental vascular resistance in lungs from 29 adult rabbits. In group I (n = 4), II (n = 8), and III (n = 8) lungs were isolated. In group IV (n = 9) rabbits were anesthetized, their chests were opened, and lungs were studied in vivo. Group I and II lungs had steady-flow perfusion: group I with intact vasotonus and group II with papaverine treatment. Group III lungs (papaverine treated) were perfused for two consecutive 45-min periods with steady and pulsatile flow. In all isolated lungs and in lungs of five anesthetized rabbits, we measured pressures in subpleural 20- to 50-microns-diam arterioles and venules by use of the micropipette servo-nulling method. Measurement of distribution of blood flow in lungs of four anesthetized rabbits by use of radiolabeled microspheres revealed no abnormality of blood flow to the micropunctured lobe. We found that total and segmental vascular resistances were similar in group I and II lungs, with microvessels representing 55% of total resistance. In group III lungs, total resistance was 30% lower during pulsatile flow than during steady flow because of a lower microvascular resistance. Lungs in vivo (group IV) had a significantly lower total vascular resistance than isolated lungs and had a low fractional resistance in microvessels (approximately 28%). We conclude that, in isolated perfused adult rabbit lungs, vascular resistance is very high, particularly in the microvascular segment, and that pulsatile flow decreases microvascular resistance.
Role of the diaphragm in chest wall mechanics
Authors: Lichtenstein O. , Ben-Haim S. A. , Saidel G. M. , Dinnar U.
Published: December 2017

We analyzed three different assumptions about diaphragm function that determine the thoracoabdominal interaction. In the simplest case, the diaphragm is assumed to be a completely flaccid membrane serving only to partition the thorax and the abdominal cavity. In the second case, it is assumed to have a finite tension but to maintain a relatively flat surface at the base of the rib cage (i.e., a negligible zone of apposition). In the general case, it is assumed that the diaphragm has finite tension and its position may vary (i.e., permitting a zone of apposition). These possible modes of behavior are incorporated into a mathematical model of ventilatory system mechanics that distinguishes the diaphragm, lung, abdomen, and rib cage. The significance of these modes is examined with respect to data from human experiments in which gas or liquid is introduced into the pleural or abdominal spaces, causing a volume change (Vep). We show that the Vep effect on the thoracic and abdominal volumes is sensitive to diaphragm mechanics and depends on the nature of the Vep: gastric distension (with water or air) or pneumothorax. Only the behavior of the general model is consistent with physiological observations, especially the distribution of Vep. Our general mathematical model can quantitatively predict this behavior.
Acute ozone-induced change in airway permeability: role of infiltrating leukocytes
Authors: Kleeberger S. R. , Hudak B. B.
Published: December 2017

The role of infiltrating polymorphonuclear leukocytes (PMNs) in acute lung injury and inflammation is still controversial. In inbred mice, acute ozone (O3) exposure induces airway inflammation that is characterized by a maximal influx of lavageable PMNs 6 h after exposure and a maximal increase in lung permeability 24 h after O3. We tested the hypothesis that O3-induced change in airway epithelial permeability of O3-susceptible C57BL/6J mice is due to infiltrating PMNs. Male mice (6–8 wk) were treated with a nonsteroidal anti-inflammatory drug (indomethacin), a chemotactic inhibitor (colchicine), or an immunosuppressant (cyclophosphamide) to deplete or inhibit PMNs from infiltrating the airways. After drug or vehicle treatment, mice were exposed for 3 h to 2 ppm O3 or filtered air, and pulmonary inflammation was assessed by inflammatory cell counts and total protein content (a marker of airway permeability) in bronchoalveolar lavage (BAL) fluid. Filtered air exposure did not affect the parameters of pulmonary inflammation at any time after exposure. Compared with vehicle controls, each of the drug treatments resulted in significant reduction of PMN influx 6 and 24 h after O3. However, total BAL protein content was not attenuated significantly by the three treatments at either 6 or 24 h postexposure. Results of these experiments suggest that the influx of PMNs and the change in total BAL protein are not mutually dependent events in this model and suggest that infiltrating PMNs do not play a major role in acute O3-induced changes in permeability of the murine lung.
Aging and respiratory muscle metabolic plasticity: effects of endurance training
Authors: Powers S. K. , Lawler J. , Criswell D. , Lieu F. K. , Martin D.
Published: December 2017

We examined the oxidative and antioxidant enzyme activities in respiratory and locomotor muscles in response to endurance training in young and aging rats. Young adult (4-mo-old) and old (24-mo-old) female Fischer 344 rats were divided into four groups: 1) young trained (n = 12), 2) young untrained (n = 12), 3) old trained (n = 10), and 4) old untrained (n = 6). Both young and old endurance-trained animals performed the same training protocol during 10 wk of continuous treadmill exercise (60 min/day, 5 days/wk). Compared with young untrained animals, the young trained group had significantly elevated (P less than 0.05) activities of 3-hydroxyacyl-CoA dehydrogenase (HADH), glutathione peroxidase (GPX), and citrate synthase (CS) in both the costal diaphragm and the plantaris muscle. In contrast, training had no influence (P greater than 0.05) on the activity of lactate dehydrogenase within the costal diaphragm in young animals. In the aging animals, training did not alter (P greater than 0.05) activities of CS, HADH, GPX, or lactate dehydrogenase in the costal diaphragm but significantly (P less than 0.05) increased CS, HADH, and GPX activities in the plantaris muscle. Furthermore, training resulted in higher activities of CS and HADH in the intercostal muscles in the old trained than in the old untrained animals. Finally, activities of CS, HADH, and GPX were significantly (P less than 0.05) lower in the plantaris in the old untrained than in the young untrained animals; however, CS, HADH, and GPX activities were greater (P less than 0.05) in the costal diaphragm in the old sedentary than in the young untrained animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Maturation of steady-state CO2 sensitivity in vagotomized anesthetized lambs
Authors: Jansen A. H. , Ioffe S. , Chernick V.
Published: December 2017

The maturation of the respiratory sensitivity to CO2 was studied in three groups of anesthetized (ketamine, acepromazine) lambs 2–3, 14–16, and 21–22 days old. The lambs were tracheostomized, vagotomized, paralyzed, and ventilated with 100% O2. Phrenic nerve activity served as the measure of respiration. The lambs were hyperventilated to apneic threshold, and end-tidal PCO2 was raised in 0.5% steps for 5–7 min each to a maximum 7–8% and then decreased in similar steps to apneic threshold. The sinus nerves were cut, and the CO2 test procedure was repeated. Phrenic activity during the last 2 min of every step change was analyzed. The CO2 sensitivity before and after sinus nerve section was determined as change in percent minute phrenic output per Torr change in arterial PCO2 from apneic threshold. Mean apneic thresholds (arterial PCO2) were not significantly different among the groups: 34.8 +/- 2.08, 32.7 +/- 2.08, and 34.7 +/- 2.25 (SE) Torr for 2- to 3-, 14- to 16-, and 21- to 22-day-old lambs, respectively. After sinus denervation, apneic thresholds were raised in all groups [39.9 +/- 2.08, 40.9 +/- 2.08, and 45.3 +/- 2.25 (SE) Torr, respectively] but were not different from each other. CO2 response slopes did not change with age before or after sinus nerve section. We conclude that carotid bodies contribute to the CO2 response during hyperoxia by affecting the apneic threshold but do not affect the steady-state CO2 sensitivity and the central chemoreceptors are functionally mature shortly after birth.
Oxygen-dependent reperfusion injury in the isolated rat lung
Authors: Eckenhoff R. G. , Dodia C. , Tan Z. , Fisher A. B.
Published: December 2017

To further define the relationship between oxygen dependence of lung injury during ischemia and ischemia-reperfusion, we used the isolated, perfused, and ventilated rat lung model, so that oxygenation and perfusion could be separated. During ischemia, lungs were ventilated with various oxygen concentrations and then ventilated with 95% oxygen during the 60-min reperfusion period. Other lungs were ventilated with 0% oxygen (nitrogen) during ischemia, and the reperfusion phase oxygen concentration was varied. Tissue and perfusate lipid peroxidation products (thiobarbituric acid-reactive substances and conjugated dienes), dry-to-wet weight ratio, and lactate dehydrogenase were measured as indexes of lung damage. In addition, electron microscopy of some lungs was performed. Results demonstrate an oxygen dependence of lipid peroxidation in both the ischemic and reperfusion phases, but lipid peroxidation is severalfold greater in the reperfusion than in the ischemic phase. Products of lipid peroxidation closely correlate with indexes of lung injury (dry-to-wet weight ratio, lactate dehydrogenase, and electron microscopy).