bluuebunny/crossref_metadata_2025 huggingface dataset:
Rib cage and abdominal contributions to ventilatory response to CO2 in infants
Authors: Honma Y. , Wilkes D. , Bryan M. H. , Bryan A. C.
Published: December 2017

We have measured the ventilatory response to inhaled CO2 of six newborn infants in rapid-eye-movement (REM) and non-REM (NREM) sleep. Ventilatory responses were measured using the Read rebreathing technique. The response was further partitioned into the volume contributions of the rib cage and abdominal compartment using the respiratory inductance plethysmograph. Sleep state was defined by electroencephalogram, electrooculogram, and behavioral criteria. In NREM sleep, there was a highly significant linear correlation between both tidal volume (VT) and instantaneous minute ventilation (VI) with CO2. Among infants, the slope of VT varied from 1.0 to 0.34 ml X Torr-1 X kg-1. However, these differences were largely due to differences in rib cage contribution, which varied from 0.56 to -0.08 ml X Torr-1 X kg-1. The abdominal contribution was similar among infants (0.41–0.56 ml X Torr-1 X kg-1). In REM, the slopes of VI were less steep than in NREM, with greater breath-to-breath variability. Slopes of VT also tended to be lower. The abdominal responses were similar to those in NREM, whereas the rib cage response was low and negative in three studies. We conclude that the slope of the CO2 response curve is primarily determined by the extent of rib cage recruitment.
Effect of training on blood lactate levels during submaximal exercise
Authors: Hurley B. F. , Hagberg J. M. , Allen W. K. , Seals D. R. , Young J. C. , Cuddihee R. W. , Holloszy J. O.
Published: December 2017

Eight men were studied before and after a 12-wk exercise program to determine the effect of training on blood lactate levels during submaximal exercise. The training elicited a 26% increase in maximum O2 uptake (VO2max). Lactate concentrations at the same relative exercise intensities in the 55–75% of VO2max range were significantly lower after training. A significantly higher relative exercise intensity was needed to elicit a given lactate level in the 1.5- to 3.0-mM range after training. O2 uptake at the work rate required to raise blood lactate to 2.5 mM was 39% higher after training. A blood lactate of 2.5 mM was attained at 68 +/- 4% VO2max before and 75 +/- 3% of VO2max after training. Eight competitive runners required an even higher relative work rate (83 +/- 2% of VO2max) to attain a blood lactate of 2.5 mM. These data provide evidence that the adaptations to training that result in an increase in VO2max are, to some degree, independent of those responsible for the lower blood lactate levels during submaximal exercise.
A modified anaerobic method of sweat collection
Authors: Boysen T. C. , Yanagawa S. , Sato F. , Sato K.
Published: December 2017

In an attempt to devise a method for collecting large volumes of thermally induced sweat with less epidermal contamination and evaporative water loss, we developed an anaerobic sweat collector by using a sheet of polyethylene film placed over a thin layer of Vaseline and paraffin oil on the skin. To test the validity of the new method, sweat samples collected every 5 min from the new collector (sweat A) were compared with those obtained from a second collector using no oil (sweat B) and scraped sweat for concentrations of adenosine 3′,5′-cyclic monophosphate (cAMP), protein, glucose, urea, lactic acid, calcium, sodium, potassium, and cholesterol. The concentration of sweat ingredients in scraped sweat was often far greater than could be expected from evaporative water loss alone. When compared with sweat A, sweat B also had higher concentrations of these ingredients in the initial samples, indicating epidermal contamination, which was especially marked in cAMP, protein, urea, cholesterol, and calcium. Concomitant with a rise in plasma glucose following the administration of a glucose bolus, the sweat glucose significantly increased, indicating the plasma as a major source of sweat glucose. We conclude that the new sweat collector is instrumental in collecting large volumes of the cleanest possible human sweat.
Exercise-induced adaptations of rat soleus muscle grafts
Authors: White T. P. , Villanacci J. F. , Morales P. G. , Segal S. S. , Essig D. A.
Published: December 2017

In female Wistar rats (n = 316) under pentobarbital sodium anesthesia, the soleus muscle was autografted with its nerve reimplanted. One purpose was to characterize the chronological development of graft innervation and recruitment during locomotion. Furthermore, we tested hypotheses regarding the efficacy of run conditioning of different intensities, durations, and postgrafting initiation times to alter mass and pyruvate-malate oxidation capacity of grafts. Choline acetyltransferase activity of grafts increased from 10% of control value at 7 days postgrafting to 55 and 100% at days 28 and 56, respectively. Running-induced glycogen depletion occurred in grafts; this is consistent with graft recruitment during locomotion. There was a threshold of conditioning intensity below which no improvements occurred and above which there were improvements. Spring (50 m/min) and endurance (30 m/min) conditioning of a duration of at least 28 days that was initiated at 28 or 56 days postgrafting increased mass of grafts by 30% compared with grafts from nonconditioned rats. Easy conditioning (15 m/min) had no effect on graft mass. Changes in graft total protein content paralleled those of mass. Oxidation capacity of grafts increased significantly with some conditioning protocols, but not to the same extent as mass. The exercise-induced adaptations should improve graft function in the host organism.
Effect of O2, N2, and CO2 composition on nonlinearity of Fleisch pneumotachograph characteristics
Authors: Yeh M. P. , Adams T. D. , Gardner R. M. , Yanowitz F. G.
Published: December 2017

Although the Fleisch pneumotachograph has many advantages, its flow-conductance characteristics are nonlinear and sensitive to changes in gas composition. The purpose of this study was to assess the effect of different O2, N2, and CO2 compositions on the nonlinearity of the Fleisch pneumotachograph flow-conductance characteristics, by use of a recently developed computerized calibration method. Hospital-grade O2 was mixed with room air to obtain seven gas mixtures (containing O2 percentages of 20.9, 28.3, 38.7, 52.8, 66.7, 78.7, and 99.6%). Within the accuracy of the applied method, the measured flow-conductance curves of the pneumotachograph had the same shape. Relative flow resistance of gas mixtures to room air was directly proportional to their O2 composition. Two O2-N2-CO2 mixtures were also tested. Their relative flow resistance compared with room air was proportional to the viscosity ratios. We concluded that the change in O2, N2, and CO2 composition does not affect the nonlinearity of the Fleisch pneumotachograph flow-conductance characteristics. However, the relative flow resistance compared with room air does change in a predictable way.
Glucose tolerance in young and older athletes and sedentary men
Authors: Seals D. R. , Hagberg J. M. , Allen W. K. , Hurley B. F. , Dalsky G. P. , Ehsani A. A. , Holloszy J. O.
Published: December 2017

Groups of endurance-trained masters athletes (60 +/- 2 yr), older untrained men (62 +/- 1 yr), lean older untrained men (61 +/- 2 yr), endurance-trained young athletes (26 +/- 1 yr), and young untrained men (28 +/- 1 yr) were studied to obtain information on the separate effects of age, physical activity, and body fatness on glucose tolerance and insulin sensitivity. Each subject underwent an oral 100-g glucose tolerance test. Skinfold thickness was determined at six sites. The trained groups had a higher maximum O2 uptake capacity and lower sum of skinfolds than their sedentary peers. The lean older untrained group had a sum of skinfolds similar to that of the young untrained group. The masters athletes, young athletes, and young untrained men exhibited similar glucose tolerance whereas the two older untrained groups had an almost twofold greater total area under the glucose curve (P less than 0.05). The masters and young athletes had significantly blunted plasma insulin responses compared with the other three groups (P less than 0.05). The young and the lean older untrained groups had similar plasma insulin responses with significantly lower insulin levels than the older untrained group (P less than 0.05). These results provide evidence that regularly performed vigorous exercise can, in some individuals, prevent the deterioration of glucose tolerance and insulin sensitivity with age.
Interrelationships of contraction time, Vmax, and myosin ATPase after spinal transection
Authors: Roy R. R. , Sacks R. D. , Baldwin K. M. , Short M. , Edgerton V. R.
Published: December 2017

Interrelationships of selected mechanical and biochemical properties of hindlimb extensor muscles following low thoracic cord transection were studied. Kittens were spinalized (Sp) at 2 wk and maintained for 6–12 mo. Some Sp animals were exercised (Sp-E) on a treadmill 25–30 min/day, 5 days/wk. In situ contractile properties of the slow-twitch soleus (SOL) and fast-twitch medical gastrocnemius (MG) muscles of normal (N), Sp, and Sp-E cats were determined. Exercise did not affect most parameters; thus Sp and Sp-E groups are considered collectively. The cross-sectional areas (CSA) of the SOL and MG decreased by 43 and 32%, respectively. Specific tension (tension/CSA) was maintained in the SOL but decreased (P less than 0.05) in the MG. Contraction time (CT) and half-relaxation time were significantly shorter in the SOL but unchanged in the MG. Maximum shortening velocity (Vmax) and myosin ATPase (mumol X mg-1 X min-1) increased (P less than 0.05) in the SOL of both groups and the MG of Sp. Frequency-tension responses of both muscles shifted toward that resembling a “faster” muscle. These results substantiate the existence of relatively independent regulatory mechanisms for Vmax and CT and show that myosin ATPase levels are more closely related to Vmax than CT. Although the changes in the SOL were consistent with the hypothesis that slow fibers are converted to fast, the elevated Vmax and myosin ATPase of the MG suggest that significant changes also occur within a “fast” fiber-type category.
Relative independence of metabolic enzymes and neuromuscular activity
Authors: Baldwin K. M. , Roy R. R. , Sacks R. D. , Blanco C. , Edgerton V. R.
Published: December 2017

Effects of spinal cord transection in 2-wk-old cats on the metabolic, histochemical, and fatigue properties of a fast- and a slow-twitch muscle were determined. Chronic (6–12 mo) spinalization (Sp) resulted in an increased ratio of fast-twitch, oxidative-glycolytic (FOG) to slow-twitch, oxidative (SO) fibers in soleus (SOL). In medial gastrocnemius (MG), Sp produced a histochemical profile suggesting that fast fibers were increased at the expense of slow fibers. Changes in biochemical markers for oxidative (citrate synthase) and glycolytic (GPD) potential were consistent with the histochemical findings. The fatigue index of Sp MG and SOL remained normal and was consistent with the type and degree of fiber type change. Daily treadmill exercise did not markedly alter any of the adaptations. The metabolic and fatigue properties of skeletal muscle of Sp cats are consistent with the view that as some fibers develop “faster-like” characteristics, the oxidative and the glycolytic potential is also enhanced. As was true of the contractile properties and related biochemical data, the changes observed suggest that significant changes occurred within as well as across fiber types. These data, in conjunction with that of chronic EMG recordings, provide evidence that there is a relative independence of both the oxidative potential and the fatigability of a muscle relative to its quantity of activation.
Measurement system for respiratory water vapor and temperature dynamics
Authors: Primiano F. P. , Montague F. W. , Saidel G. M.
Published: December 2017

An instrumentation system has been developed to simultaneously measure water vapor and temperature at the same point within respiratory airways during breathing. A mass spectrometer was used to analyze gas continuously sampled through a modified inlet catheter. At the tip of the catheter, gas temperature is sensed by a microbead thermistor. Adequate water vapor dynamics is achieved by a two-step procedure. First, the tip of the sampling catheter is constricted to reduce the catheter's internal pressure and thereby prevent condensation and evaporation. Second, the water vapor signal from the mass spectrometer is compensated electronically to improve its transient response. As part of the evaluation of the system, water vapor and gas temperature were measured in the oropharynx of human subjects.
Effect of high local temperature on reflex cutaneous vasodilation
Authors: Taylor W. F. , Johnson J. M. , O'Leary D. , Park M. K.
Published: December 2017

We examined the effect of high local forearm skin temperature (Tloc) on reflex cutaneous vasodilator responses to elevated whole-body skin (Tsk) and internal temperatures. One forearm was locally warmed to 42 degrees C while the other was left at ambient conditions to determine if a high Tloc could attenuate or abolish reflex vasodilation. Forearm blood flow (FBF) was monitored in both arms, increases being indicative of increases in skin blood flow (SkBF). In one protocol, Tsk was raised to 39–40degrees C 30 min after Tloc in one arm had been raised to 42 degrees C. In a second protocol, Tsk andTloc were elevated simultaneously. In protocol 1, the locally warmed arm showed little or no change in blood flow in response to increasing Tsk and esophageal temperature (average rise = 0.76 +/-1.18 ml X 100 ml-1 X min-1), whereas FBF in the normothermic arm rose by an average of 8.84 +/- 3.85 ml X 100 ml-1 X min-1. In protocol 2, FBF in the normothermic arm converged with that in the warmed arm in three of four cases but did not surpass it. We conclude that local warming to 42 degrees C for 35–55 min prevents reflex forearm cutaneous vasodilator responses to whole-body heat stress. The data strongly suggest that this attenuation is via reduction or abolition of basal tone in the cutaneous arteriolar smooth muscle and that at a Tloc of 42 degrees C a maximum forearm SkBF has been achieved. Implicit in this conclusion is that local warming has been applied for a duration sufficient to achieve a plateau in FBF.
Alveolar surface tension, lung inflation, and hydration affect interstitial pressure [Px(f)]
Authors: Hida W. , Hildebrandt J.
Published: December 2017

Peribronchoarterial interstitial fluid pressure [Px(f)] was measured by wicks inserted between bronchus and artery of dog lobes filled with air, saline, 6% dextran in saline, or mineral oil. Five inflations were made to total lung capacity, with one min stops at eight selected volume levels in each cycle. Deflation recoil (measured as transpulmonary pressure, Ptp) was largest for air and least for saline and dextran, and it fell between these extremes for mineral oil. Correspondingly, Px(f) was most negative for air, slightly less negative for mineral oil, and least for saline and dextran. On the first cycle, the Px(f) for saline and dextran were nearly equal, but in later cycles Px(f) with saline drifted fairly rapidly toward alveolar pressure. By plotting Px(f) vs. Ptp, all first-cycle curves were brought toward a single line. During later cycles, Ptp and Px(f) always changed together along this line, except for saline. We conclude that 1) at fixed vascular pressure, Px(f) depends mainly on Ptp and less on lung volume; 2) large changes in Px(f) with saline suggest that at least some fluid can enter this interstitial space quite rapidly; and 3) peripheral tissue swelling with saline causes some reduction in Ptp, and both swelling and lower recoil contribute to increased trapping of saline.
Tracheal cross-sectional areas from acoustic reflections in dogs
Authors: Jackson A. C. , Krevans J. R.
Published: December 2017

The cross-sectional area of airways can be estimated from their response to an acoustic pressure pulse introduced at the airway opening. Errors in these area estimates are expected if the airways do not behave rigidly at these frequencies. In eight dogs we tested the accuracy of this technique to estimate tracheal cross-sectional areas by comparing them with area estimates made from radiographic bronchograms. Tracheal areas using this technique were not statistically different from areas determined radiographically. The results indicate that the dog trachea does behave rigidly enough so that this method can be used to measure its cross-sectional area.
Static contraction of hindlimb muscles in cats reflexly relaxes tracheal smooth muscle
Authors: Longhurst J. C.
Published: December 2017

Static contraction of skeletal muscle is associated with increased ventilation. Although chemical stimulation of afferents from skeletal muscle causes relaxation of tracheal smooth muscle, it is not known if skeletal muscle contraction also causes tracheal relaxation. Therefore, in 10 chloralose-anesthetized cats, I examined the hemodynamic and tracheal smooth muscle responses to hindlimb skeletal muscle contraction induced by stimulating the L7 and S1 ventral roots. Isometric tension was measured in the transverse cervical trachea. During contraction average gastrocnemius tension increased from 0.7 +/- 0.1 to 4.9 +/- 0.6 kg, blood pressure and heart rate increased from 100 +/- 8 to 128 +/- 9 mmHg and from 192 +/- 11 to 202 +/- 13 beats/min, respectively, whereas tracheal tension decreased from 19.7 +/- 0.4 to 17.5 +/- 0.7 g (all P less than 0.02). There were significant (P less than 0.01) linear correlations between change in tracheal tension and maximal developed tension (r = -0.65), tension time (r = -0.68), and average developed tension (r = -0.76). Transection of the L7 and S1 dorsal roots in six cats reduced the tracheal relaxation associated with muscle contraction (pre: 19.9 +/- 0.3 to 17.5 +/- 0.3 g vs. post: 20.3 +/- 0.4 to 20.3 +/- 0.6 g) while average developed gastrocnemius muscle tension was not altered (pre: 1.1 +/- 0.1 to 6.4 +/- 1.1 kg vs. post: 1.2 +/- 0.2 to 6.8 +/- 1.2 kg). Thus static contraction of hindlimb muscles in cats reflexly lowers tracheal tension. This response is related to muscle mass and total tension generated by the contracting skeletal muscle.
Interaction of sulfur dioxide and dry cold air in causing bronchoconstriction in asthmatic subjects
Authors: Bethel R. A. , Sheppard D. , Epstein J. , Tam E. , Nadel J. A. , Boushey H. A.
Published: December 2017

To determine whether sulfur dioxide and airway cooling and drying interact in causing bronchoconstriction in persons who have asthma, we measured specific airway resistance in seven asthmatic subjects before and after they performed voluntary eucapnic hyperpnea for 3 min breathing four different gas mixtures. The mixtures, which the subjects breathed through a mouthpiece in random order on 4 different days, were 1) humidified room-temperature air, 2) humidified room-temperature air containing 0.5 ppm SO2, 3) cold dry air, and 4) cold dry air containing 0.5 ppm SO2. Each subject breathed at a rate and depth known from preliminary studies to cause little or no bronchoconstriction when that subject inhaled 0.5 ppm SO2 in humidified room-temperature air or cold dry air. When given independently in the blinded study, 0.5 ppm SO2 or cold dry air again caused insignificant bronchoconstriction, but when given together the two stimuli caused significant bronchoconstriction, as indicated by an increase in specific airway resistance from 6.94 +/- 2.85 to 22.35 +/- 10.28 l X cmH2O X l–1 X s (mean +/- SD) (P less than 0.001). thus airway cooling and/or drying increases the bronchoconstriction induced by inhaled SO2 in persons who have asthma. This increase suggests that persons who have asthma may be more sensitive to the bronchoconstrictor effects of ambient SO2 in cold dry environments than in warm moist environments.
Human whole-blood oxygen affinity: effect of temperature
Authors: Zwart A. , Kwant G. , Oeseburg B. , Zijlstra W. G.
Published: December 2017

phe effect of temperature changes on human whole-blood O2 affinity was measured in the blood of six healthy donors over almost the entire O2 saturation (SO2) range (1–99%). The results showed that temperature has no influence on the shape of the O2 dissociation curve, implying that the temperature coefficient (delta log PO2/delta T) is independent of SO2. Simultaneous measurements of the total (proton) Haldane factor (delta[HbH]/[delta HbO2]) at the five temperatures under study (22, 27, 32, 37, and 42 degrees C) revealed that this factor depends on temperature. The liberation of protons from hemoglobin appeared to be linear with respect to changes in SO2. We therefore conclude that the (proton) Bohr factor (H+ factor) is dependent on temperature over the entire SO2 range in the same way as previously described for SO2 = 50%. The exothermic oxygenation reaction in whole blood was accompanied by a heat evolution (delta HO2) of 42.7 kJ/mol (monomeric) hemoglobin.
Neural regulation of 35SO4-macromolecule secretion from tracheal glands of ferrets
Authors: Borson D. B. , Charlin M. , Gold B. D. , Nadel J. A.
Published: December 2017

Our goal was to determine what nervous mechanisms mediate the secretion of macromolecules from tracheal submucosal glands of ferrets. To do this, we studied the secretion of 35SO4-labeled macromolecules in vitro in response to electrical or pharmacological stimulation in the absence and presence of a specific nerve blocker and autonomic antagonists. We found that electrical field stimulation and the agonists acetylcholine, phenylephrine, terbutaline, and norepinephrine each cause secretion of radiolabeled materials. The molecular weights of the labeled materials released during base line and after electrical stimulation were greater than 1,000,000. The antagonists atropine, phentolamine, and propranolol alone prevented the responses to acetylcholine, phenylephrine, and terbutaline, respectively, without preventing responses to any other of these agonists or changing baseline secretion. Only phentolamine and propranolol together prevented the response to norepinephrine. Tetrodotoxin prevented the response to electrical stimulation but not the responses to the agonists. Each of the antagonists inhibited a significant portion of the response to electrical stimulation, but the combination of all three did not completely prevent secretion. We conclude that cholinergic nerves mediate secretion via muscarinic mechanisms, that adrenergic nerves mediate secretion via both alpha- and beta-adrenergic mechanisms, and that nonadrenergic-noncholinergic nerves mediate secretion via unidentified mechanisms.
Apnea duration is related to ventilatory oscillation characteristics in newborn infants
Authors: Waggener T. B. , Stark A. R. , Cohlan B. A. , Frantz I. D.
Published: December 2017

The occasional short apneas seen in full-term infants within the first postnatal week are related to the minimum phase of oscillatory breathing patterns. To determine the relationship between breathing patterns and the longer and more frequent apneas seen in premature infants, we monitored respiration in 14 premature infants using a face mask and pneumotachograph. Tidal volume, breath duration, and ventilation were calculated on a breath by breath basis, converted to time-axis data strings, and filtered with a comb of zero phase shift digital band pass filters to detect breathing patterns. Compared with full-term infants, premature infants had breathing patterns that occurred more often and had twice the average amplitude. Of 182 apneas greater than or equal to 3 s long, 94% occurred at the minimum phase of oscillatory breathing patterns. All of the 38 apneas greater than or equal to 10 s long occurred at the minimum phase of oscillatory breathing patterns. Duration of apnea was related to breathing pattern characteristics, e.g., longer apneas were related to stronger, longer cycle-time breathing patterns. Apnea in the premature infant is not an isolated event but is one aspect of an underlying pattern.
Determination of lung water content and distribution by nuclear magnetic resonance
Authors: Cutillo A. G. , Morris A. H. , Blatter D. D. , Case T. A. , Ailion D. C. , Durney C. H. , Johnson S. A.
Published: December 2017

The present study was designed to determine the value of nuclear magnetic resonance (NMR) imaging as a technique for quantifying lung water distribution and to estimate the degree of spatial resolution achieved by this technique. The spatial distribution of water was determined in six small (0.76 ml) rat lung tissue specimens by an NMR line-scan technique. After NMR imaging, each lung specimen was frozen and subdivided into slices; the gravimetric lung water content for each lung slice was compared with the integrated NMR water content over the volume corresponding to the same lung slice. In each tissue specimen, NMR and gravimetric lung water values were significantly correlated; the correlation coefficient for the pooled data for all six lung specimens was 0.91 (P less than 0.01). In two lung specimens, NMR values tended to be slightly higher than the gravimetric values. The magnitude of the difference between NMR and gravimetric values was generally less than 20% and only occasionally exceeded 25%. Our results suggest that the NMR-imaging method provides satisfactory estimates of lung water content and its distribution; the resolving power of the technique is excellent, as shown by its ability to detect water content differences between lung tissue slices of volume as small as 0.076 ml.
Pressure excursions during oscillatory flow in a branching network of tubes
Authors: Akhavan R. , Kamm R. D.
Published: December 2017

The pressure difference across individual branches of a four-generation network of branching tubes was measured with the objective of obtaining general laws to describe the pressure drop in the airways under conditions of oscillatory flow. Fourier decomposition showed that the pressure signals consisted of a dominant component at the excitation frequency (“fundamental”) and a “first harmonic” of smaller magnitude. For values of the ratio Re/alpha less than 200, the fundamental mainly represented fluid acceleration, whereas the first harmonic reflected the effects both of viscous dissipation and the change in total cross-sectional area between parent and daughter generations. For values of Re/alpha greater than 200, the magnitude of the fundamental was considerably larger than that due to fluid acceleration alone, suggesting the possibility of onset of turbulence in the branching network. These pressure measurements were applied to a simple model of the dog lung to predict total airway resistance. The results are found to be in substantial agreement with physiological measurements.
Effect of increased lung volume on perception of breathlessness, effort, and tension
Authors: Killian K. J. , Gandevia S. C. , Summers E. , Campbell E. J.
Published: December 2017

By the addition of externally added elastic loads at both functional residual capacity (FRC) and increased lung volume, increased respiratory muscle effort, tension, and breathlessness were induced in normal subjects. The magnitude of each of these sensations was estimated using the psychophysical technique of category scaling (Med. Sci. Sports Exercise 14: 377–381, 1982). The tidal volume, inspiratory time, and breathing frequency were kept constant to avoid variability in sensation due to these factors. The perceived magnitude of effort and breathlessness increased significantly as the inspiratory pressure and lung volume increased (P less than 0.05). The magnitude of perceived tension increased as the inspiratory pressure increased (P less than 0.05) but not as lung volume increased. To validate these results, the subjects estimated the perceived magnitude of a series of static inspiratory occlusion pressures at both lung volumes using open-magnitude scaling and sensory matching. The perceived magnitude of effort increased significantly as the pressure increased and as the lung volume increased (P less than 0.05). To match the perceived effort required to produce the target pressures at FRC, the subjects reproduced pressures. These were not significantly different. However, to match the effort required to produce the target pressures at increased lung volume, the pressures reproduced at FRC were significantly greater (P less than 0.05). The results suggest that the sensations of breathlessness and effort are psychophysically the same, whereas tension is perceived by a different sensory mechanism.
Regulation of transport across pulmonary alveolar epithelial cell monolayers
Authors: Goodman B. E. , Brown S. E. , Crandall E. D.
Published: December 2017

Domes are formed in large numbers by primary cultured monolayers of type II alveolar epithelial cells from rat lungs. These fluid-filled structures are formed by active transport of solute from medium to substratum, with water following passively. In the present study, we used dome-forming monolayers to study the regulation of alveolar epithelial transport processes by determining the effects on dome formation of adenosine 3',5'-cyclic monophosphate (cAMP) analogues, phosphodiesterase inhibitors, neurotransmitters, and vasopressin (antidiuretic hormone, ADH). The cAMP analogues (dibutyryl cAMP and 8-bromo-cAMP) and phosphodiesterase inhibitors (theophylline, papaverine, and isobutylmethylxanthine) caused large increases in dome formation by 24 h. ADH and beta-adrenergic agonists (epinephrine, terbutaline, and isoproterenol) also caused significant increases in dome density. The beta-agonist response was completely eliminated in the presence of the beta-blocker propranolol. Dibutyryl guanosine 3',5'-cyclic monophosphate and acetylcholine (cholinergic agonist) had no effect on dome formation, whereas the alpha-adrenergic agonist methoxamine caused a small but significant decrease in dome formation. These findings suggest that the active solute flux resulting in dome formation by type II alveolar epithelial cell monolayers is increased by substances expected to elevate intracellular cAMP (or analogue) concentrations. An attractive speculation having major implications for lung fluid balance is that transepithelial fluxes can be modulated by endogenous, and perhaps exogenous, chemical agents in adult mammalian alveolar epithelium in vivo.
Reproducibility and accuracy of airway area by acoustic reflection
Authors: Brooks L. J. , Castile R. G. , Glass G. M. , Griscom N. T. , Wohl M. E. , Fredberg J. J.
Published: December 2017

To determine the accuracy and reproducibility of measurements of airway area by acoustic reflection (AAAR) we made repeated measurements of tracheal areas in human volunteers, glass airway models, and excised canine tracheae. In 10 adult males, the mean ratio of tracheal AAAR to tracheal areas determined roentgenographically was not significantly different from one (1.06 +/- 0.13 SD). Within-run variability was 10 +/- 4% (CV), mean intrasubject day-to-day variability was 9 +/- 4% (CV). A custom-made mouthpiece is necessary for accurate measurements of AAAR. Mean variability related to differences in mouthpiece construction was 7 +/- 6% (CV). The effect of variations in upper airway and glottic sizes on tracheal AAAR measurements was investigated using glass airway models. In model studies, tracheal AAAR measurements were found to be independent of changes in proximal airway size for glottic apertures greater than or equal to 1 cm2 and upper airway areas less than or equal to 8 cm2. Tracheal area was, however, overestimated by 20% in the rigid-walled glass models. The effects of airway wall rigidity were qualitatively investigated by comparing acoustic and roentgenographic measurements of excised canine tracheae surrounded by either air or petroleum jelly. Differences in the accuracy of measurements of AAAR in vitro and in vivo are probably due to differences in airway wall inertance. These studies suggest that the measurement of AAAR yields an accurate and reproducible result that may be clinically useful for the noninvasive detection of changes in central airway geometry.
Coordination between rib cage muscles and diaphragm during quiet breathing in humans
Authors: De Troyer A. , Estenne M.
Published: December 2017

The pattern of activation of the scalenes and the parasternal intercostal muscles was studied in relation to the pattern of rib cage and abdominal motion during various respiratory maneuvers in the tidal volume range in five normal humans. Electromyograms (EMG) of the scalenes and parasternal intercostals were recorded with bipolar needle electrodes, and changes in abdominal and rib cage displacement were measured using linearized magnetometers. The scalenes and parasternal intercostals were always active during quiet breathing, and their pattern of activation was identical; in both muscles the EMG activity usually started together with the beginning of inspiration, increased in intensity as inspiration proceeded, and persisted into the early part of expiration. In addition, like the parasternal activity the scalene inspiratory activity persisted until the tidal volume was trivial, increased during tidal inspirations performed with the rib cage alone, and was nearly abolished during diaphragmatic isovolume maneuvers. However, attempts to perform tidal inspiration with the diaphragm alone, while causing an increase in parasternal EMG activity, were associated with a marked reduction or a suppression of scalene EMG activity and a reduced substantially distorted rib cage expansion. In particular, the upper rib cage was then moving paradoxically.(ABSTRACT TRUNCATED AT 250 WORDS)
How does positive end-expiratory pressure reduce intrapulmonary shunt in canine pulmonary edema?
Authors: Malo J. , Ali J. , Wood L. D.
Published: December 2017

We ventilated separately the right and left lungs of seven dogs having thoracotomies and catheters in both lower lobe veins. Two hours after right atrial injection of oleic acid, shunt (Qs/QT) in each lower lobe increased from 0.10 to 0.47. Ten minutes after positive end-expiratory pressure (PEEP) was increased from 3 to 13 cmH2O in one lung, mean lobar Qs/QT decreased to 0.06 with no change in its fraction of pulmonary blood flow measured by microsphere techniques. At the same time mean Qs/QT in the other lower lobe was 0.48. At end expiration each lower lobe hilum was then clamped, and the excised lobe was quickly frozen over liquid N2. There was no difference in the extravascular lung liquid per gram blood-free dry lobe between the lower lobes (7.5 +/- 2.6 ml/g), but perivascular cuff liquid was greater in the lower lobe with PEEP (3.8 +/- 2.8 ml/g) than in the lower lobes without PEEP (2.4 +/- 1.7 ml/g). Light microscopy revealed that 77.8 +/- 9.0% of the alveoli were flooded in the lobe without PEEP, but only 22.2 +/- 11.8% were flooded in the lobe with PEEP. The mean linear intercepts of the flooded alveoli were not different between lower lobes, and both were reduced to about 50% of the size of adjacent unflooded units in the same lobe. Alveolar septum thickness was greater without PEEP. We conclude that PEEP reduces Qs/QT by inflating previously flooded and collapsed air spaces and by redistributing the excess alveolar water into the compliant perivascular space, thus eliminating the obstacle to pulmonary O2 transfer.
Pressure effects and uptake of platelet-activating factor in isolated rat lung
Authors: Lichey J. , Friedrich T. , Franke J. , Nigam S. , Priesnitz M. , Oeff K.
Published: December 2017

The aim of this study was, first, to examine pressure effects of platelet-activating factor (PAF) on pulmonary vasculature and bronchi in isolated perfused and ventilated rat lungs and, second, to investigate pulmonary uptake of tritium-labeled PAF injected into the pulmonary artery. Four different perfusates were used: Krebs-Ringer solution (KRS) and KRS with 0.2, 2.0, and 4% albumin. In the KRS, perfusion and inflation pressure increased by 100 and 47%, respectively, after 100 micrograms PAF. By increasing the albumin concentration, the pressure effects were reduced significantly (P less than 0.01). These changes were paralleled by increasing tritium outflow rates (15.9 +/- 3.6, 49.7 +/- 12.5, 78.3 +/- 8.7, 87.8 +/- 2.6%, respectively). Comparable changes in tritium outflow rates (19.2 +/- 3.9, 38.2 +/- 7.2%) occurred when tracer amounts of labeled PAF were injected, but, in KRS with 2.0 and 4.0% albumin, tritium outflow was significantly lower (52.8 +/- 8.0 and 60.8 +/- 11.8%, respectively). Pressure effects are related to extraction rates. Both pressure effects and extraction rates depend on binding to the albumin in the perfusion medium used. PAF might act on smooth muscle tissue of the pulmonary vasculature. Inflation pressure increases are probably due to concomitant occurrence of edema.
Local vagal responses in the lung periphery
Authors: Gertner A. , Bromberger-Barnea B. , Kelly L. , Traystman R. , Menkes H.
Published: December 2017

In previous work we studied responses to ozone (O3) in the lung periphery of anesthetized male mongrel dogs. O3 (0.1 ppm) delivered locally to the lung periphery through a bronchoscope wedged in a segmental airway increased collateral resistance (Rcs) 31.5 +/- 5%. Bilateral cervical vagotomy or pretreatment with atropine aerosol prevented these responses to O3. In the present study we asked two questions. First, is the vagus necessary for responses to 0.1 ppm O3 because it maintains base-line tone? Second, are physiological responses to O3 administered through a bronchoscope localized to the challenged region? To answer the first question, we increased base-line Rcs (38.4 +/- 11.8%) by administering an acetylcholinesterase inhibitor, neostigmine (aerosol), through the bronchoscope. Following neostigmine, O3 exposure increased Rcs (55.8 +/- 18.4%) only if the vagi were intact. To answer the second question, we introduced two bronchoscopes simultaneously into different regions of the lung. When O3 was delivered through one bronchoscope, responses were detected only in the exposed region. However, when the whole left lung was exposed to O3, the responses were also detected in the right lung, but only when the vagi were intact. We conclude that the lung has the capacity to respond to localized oxidant insult with vagally mediated responses limited to the region that is challenged. However, when a larger area is exposed, vagally mediated responses become generalized and affect both lungs.
Respiratory activity of posterior cricoarytenoid muscle and vocal cords in humans
Authors: Brancatisano T. P. , Dodd D. S. , Engel L. A.
Published: December 2017

We examined the respiratory activity of the posterior cricoarytenoid muscle (PCA) simultaneously with the movements of the vocal cords during tidal breathing and panting in four normal seated subjects. A bipolar electrode was constructed to record the surface electromyogram (EMG) of the PCA. The glottis was visualized with a fiberoptic bronchoscope, and the glottic image was recorded simultaneously with tidal volume and a digital time marker on video tape. During quiet breathing the integrated EMG signal (EPCA) showed consistent phasic variations in each subject. The inspiratory onset of EPCA in the four subjects preceded inspiratory flow by 170 +/- 80, 650 +/- 310, 130 +/- 80, and 130 +/- 90 ms (mean +/- SD), respectively. This lead time of the PCA was similar to that between the onset of glottic widening and inspiration in each subject. The proportion of each cycle during which EPCA increased (the duty cycle) was 31 +/- 3% (mean +/- SE), whereas the inspiratory portion of the respiratory cycle constituted 37 +/- 2% (mean +/- SE), respectively. The duty cycle of the PCA remained relatively constant in the same subject on different days. During panting at functional residual capacity, the EPCA increased to 142 +/- 11% of the peak activity recorded during the preceding control breaths. This was accompanied by a sustained increase in the glottic width to 91 +/- 9% of the peak value in the preceding breaths. These results confirm the role of the PCA as a principal abductor of the vocal cords and indicate a temporal relationship between PCA activation and the inspiratory phase of the respiratory cycle during tidal breathing in humans.
Effects of hypercapnia on Breuer-Hering threshold for inspiratory termination
Authors: Clanton T. L. , Lipscomb W. T.
Published: December 2017

The effects of CO2 concentration on the timing of inspiratory duration (TI) and expiratory duration (TE) and the responses to lung inflation were studied in decerebrate paralyzed cats. With lung volume held at functional residual capacity during the breath cycle, hypercapnia (fractional concentration of inspired CO2 = 0.04) caused variable changes in TI and significant increases in TE. To obtain the Breuer-Hering threshold relationship [tidal volume (VT) vs. TI] and the timing relationship between TE and the preceding TI (TE vs. TI), ramp inflations of various sizes were used to terminate inspiration at different times in the breath cycle. Hypercapnia caused the VT vs. TI curves to shift in an upward direction so that at higher lung volumes TI was lengthened. Also, the slope of the TE vs. TI relationship was increased. The results suggest that hypercapnia diminished the sensitivity of the Breuer-Hering reflex to the lung volume, thus allowing volume to increase with little effect on TI. In addition, TE appears to become more sensitive to changes in the preceding TI. A model is presented which provides a possible neural mechanism for these responses.
Isoproterenol infusion promotes nitrogen washout in rats under normobaric conditions
Authors: Mack G. W. , Lin Y. C.
Published: December 2017

Cardiac output and the rate of N2 elimination were measured simultaneously in unanesthetized rats during isobaric desaturation with 100% O2. Whole-body N2-washout curves for the rat are characterized by three compartment half times derived by exponential stripping, representing the slow, intermediate, and fast components of the system. During saline infusion (control) the respective half times for these compartments were 120, 15, and 2 min. Isoproterenol infusion increased cardiac output by 40% and the volume of N2 eliminated by 10% over a 2-h washout. More importantly, the half time of the slowest compartment decreased from 120 to 70 min. The intermediate compartment half time shortened from 15 to 13 min, while the fast compartment was unaffected. The decrease in slow compartment half time will contribute significantly to the shortening of the duration of stay during decompression. A plot of slow compartment rate constants vs. measured cardiac output (range 280–690 ml X min-1 X kg-1) demonstrated a linear relationship between perfusion and the tissue-blood gas exchange rate. The results indicate that enhanced cardiac output and generalized vasodilation shorten the time required to desaturate the slower body tissues. Various maneuvers or drugs that demonstrate similar cardiovascular responses should be beneficial during prolonged decompression procedures involved in saturation diving.
Asymmetry of canine tracheal epithelium: osmotically induced changes
Authors: Man S. F. , Hulbert W. , Park D. S. , Thomson A. B. , Hogg J. C.
Published: December 2017

The symmetry of osmotic conductivity of the canine tracheal epithelial cells was examined in vitro. When an osmotic load of 100 mosM sucrose was added to the serosal bathing solution, no change in the transepithelial potential difference was observed in 15 tissue preparations. In contrast, when the same osmotic load was added to the mucosal bathing solution, there was a rapid decrease in the transepithelial potential difference of 3.9 +/- 0.5 mV (n = 23); ouabain (10(-4) M) eliminated this change. Tissues that had been exposed to the osmotic load added to either the mucosal or serosal side were compared with the control using light and electron microscopy. When the osmotic load was added to the mucosal fluid, there was no change in the nuclear-to-cytoplasmic area ratio of the cell types examined. However, when the same osmotic load was added to the serosal fluid, a marked increase in the nuclear-to-cytoplasmic area ratio of the ciliated cells was observed. This finding indicated cell shrinkage. Dilution potentials measured by substituting NaCl with mannitol also showed asymmetry. The morphological features are probably caused by differences in the osmotic conductivity (Lp) of the basolateral and apical cell membranes, with the Lp of the apical membrane being less than that of the basolateral membrane. The basis for osmotically induced potentials remained undetermined.
Quantification of damage by air emboli to lung microvessels in anesthetized sheep
Authors: Albertine K. H. , Wiener-Kronish J. P. , Koike K. , Staub N. C.
Published: December 2017

We studied the ultrastructural damage caused by venous air embolization in anesthetized sheep by morphological techniques after monitoring hemodynamics and lymph dynamics. Lung lymph flow and protein flux increased during 1 and 4 h of venous air embolization, results consistent with increased microvascular permeability. Histologically, the air emboli were restricted to the small pulmonary arterial vessels (1,000 to 100 micron in diam). Neutrophils accumulated around the air bubbles and formed intravascular clumps. Ultrastructurally, at the air embolus-blood interface, neutrophils appeared attached to a layer a proteinaceous material. Many neutrophils were in close contact with the pulmonary arterial endothelial cells. We found gaps (0.1–3 micron in width) between the endothelial cells of the pulmonary arterial microvessels. Beneath these gaps the basal lamina was disrupted. Other vessel types were unaffected. Some lymphocytes were seen near the air bubbles and the endothelial cell gaps. Platelets remained discoid, and fibrin clots were not observed. These results indicate that venous air embolization in sheep damages the pulmonary arterial microvessels. Neutrophils are closely associated to both the air emboli and the endothelial cell gaps.
Contribution of tree structures in the lung to lung elastic recoil
Authors: Smith J. C. , Butler J. P. , Hoppin F. G.
Published: December 2017

The direct contribution of forces in tree structures in the lung to lung recoil pressure and changes in recoil pressure induced by alterations of the forces are analyzed. The analysis distinguishes the contributions of axial and circumferential tensions in the trees and indicates that only axial tensions directly contribute to static recoil. This contribution is derived from analysis of the axial forces transmitted across a random plane transecting the lung. The change in recoil pressure induced by changes in axial tension is similarly derived. Alterations of circumferential tensions in the trees indirectly change recoil by causing nonuniform deformations of the surrounding lung parenchyma, and a continuum elasticity solution for the stress induced by the deformations is derived. Sample calculations are presented for the airway tree based on available data on airway morphometric and mechanical properties. The increase in recoil pressure accompanying increases in axial and circumferential tensions with contraction of airway smooth muscle is also analyzed. The calculations indicate that axial stresses in the airway tree out to bronchioles directly contribute only a small fraction of the static recoil pressure. However, it is found that contraction of smooth muscle in these airways can increase recoil pressure appreciably (10–20%), mainly by the deformation of the parenchyma with increases in circumferential tension in smaller airways. The results indicate that the geometric and mechanical properties of the airway tree are such that only peripheral elements of the tree can substantially affect the elastic properties of the lung. The possible contributions of vascular trees for which data on mechanical and morphometric properties are more limited are also discussed.