bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of aging on respiratory sensations produced by elastic loads
Authors: Tack M. , Altose M. D. , Cherniack N. S.
Published: December 2017

We compared the effects of graded elastic loads on respiratory sensations in 19 healthy subjects greater than 60 yr of age to 21 healthy subjects less than 30 yr old. The magnitude of the respiratory sensation was quantitated by two well-established psychophysical techniques. In the magnitude-estimation method, subjects indicated the intensity of the sensation experienced with numbers; in the cross-modality method, the level of sensation was signaled with a dynamometer activated by thumb pressure. In addition, the effects of nonrespiratory stimuli were compared in the two groups. With both methods, the logarithm of the response to elastic loads was linearly related to the logarithms of the stimulus. The slope of the line relating the log of the response to the log of the stimulus (beta) was significantly greater in the younger group than in the older group using the magnitude-estimation method but not with the cross-modality matching test. There were no differences in the ability of the two groups to assign numbers to line length. However, the older group had a lower beta for magnitude estimation of thumb force than the younger group. The results suggest 1) that respiratory sensation follows Steven's law and grows exponentially with the stimulus; 2) that the growth of sensations produced by elastic loading is less in older than in younger individuals; and 3) differences in the perception of the mode used for matching in the cross-modality test may obscure significant differences in the sensations elicited by respiratory stimuli.
Effects of 100% O2 breathing on permeability of alveolar epithelium to solute
Authors: Matalon S. , Egan E. A.
Published: December 2017

We measured the effects of 100% O2 exposure at 1 atm for 48 (n = 5) and 63 h (n = 6) on the solute permeability of the alveolar epithelium of rabbits. We instilled 10-15 ml of saline containing trace amounts of 131I-albumin (r approximately 35 A), 125I-cytochrome c (r approximately 17 A), and [57Co]cyanocobalamin (r approximately 6.5 A) into an atelectatic segment of the right lower lobe. Egress of these tracers was determined from their change in concentration in the alveolar saline and their detection in arterial blood. All tracers left the alveolar space and appeared in the arterial blood on the 63-h O2 group, cytochrome c and cyanocobalamin in the 48-h O2 group, and only cyanocobalamin in the control (air breathing). The O2-exposed animals had PaO2 values higher than 500 Torr, normal PaCO2 and pH, and wet-to-dry lung weight ratios not different from control. We concluded that increasing the length of O2 exposure increases the solute permeability of the alveolar epithelium and this precedes the appearance of pulmonary edema.
Ventriculocisternal cerebrospinal perfusion in unanesthetized fetal lambs
Authors: Bissonnette J. M. , Hohimer A. R. , Richardson B. S.
Published: December 2017

Methods have been developed for the placement of cannulas in the lateral cerebral ventricle and cisternum magnum of the fetal lamb. Three to seven days after surgery, perfusion of the cerebral ventricular system was carried out in unanesthetized lambs in utero. Artificial cerebrospinal fluid (CSF) was perfused at 123 microliter/min for 4-5 h with no change in fetal arterial O2 pressure, CO2 pressure, pH, mean arterial blood pressure, or heart rate. The preparation is suitable for measurements of net formation of fetal central CSF and also for producing changes in the ionic composition of the fetal CSF.
Effects of dopamine on chemoreflexes in breathing
Authors: Nishino T. , Lahiri S.
Published: December 2017

The effects of intravenous infusion of dopamine (20 microgram.min) on the steady-state ventilatory and carotid chemoreceptor responses to successive levels of isocapnic hypoxia and hyperoxic hypercapnia were investigated in cats anesthetized with alpha-chloralose. Dopamine infusion was followed by a maximal decrease in ventilation in about 20 s. Thereafter, the effect diminished and stabilized. Termination of dopamine infusion was promptly followed by an increase in ventilation. These ventilatory responses were smaller than the corresponding carotid chemoreceptor responses. The steady-state effect of dopamine infusion was to diminish ventilation at all levels of arterial O2 tension, the decrease being greater during hypoxia than that during hyperoxia. Bilateral section of the carotid sinus nerves significantly diminished but did not abolish the inhibitory effect of dopamine on ventilation during hyperoxia. Thus the ventilatory depression due to dopamine infusion is not entirely due to its effect on the carotid chemoreceptors. Dopamine decreased ventilatory responses to successive levels of hypercapnia by the same magnitude without changing the slope of the response curves. The steady-state relationship between chemoreceptor activity and ventilation shows that the ventilatory equivalent for carotid chemoreceptor activity is increased during dopamine infusion because of its greater inhibitory effect on carotid chemoreceptor activity than on ventilation with the decrease of arterial O2 tension.
Measurement of oxygen consumption and carbon dioxide production rates by a tracer-bolus method
Authors: Clark J. S. , Bigler A. H. , Cutillo A. , Watanabe S. , Renzetti A. D.
Published: December 2017

A new method for measuring oxygen consumption and carbon dioxide production is described. The method is based on the injection of a helium bolus into the inspired gas for repeated breaths; the helium can be delivered through the mouth or through a nostril (the injection system being controlled by the integrated flow signal or by the signal of a thermistor, respectively). Compared with the conventional gas-collection technique, the tracer-bolus method allows more rapid and frequent measurements. The method does not necessarily require an airtight respiratory circuit, so that it can be conveniently applied in less cooperative subjects, including children. The results of validation studies based on a comparison with the standard gas-collection technique are presented; these results indicate that the measurements by the tracer-bolus method are accurate in normal subjects. In patients with obstructive lung disease, the determinations are associated with a systematic error, which is expected, the tracer-bolus method being based on a single-compartment, uniformly ventilated and perfused lung model; the error is, however, predictable from the degree of functional impairment and can be corrected using equations based on routine pulmonary function tests.
Interactions between permeability and hydrostatic pressure in perfused dogs' lungs
Authors: Huchon G. J. , Hopewell P. C. , Murray J. F.
Published: December 2017

To evaluate interactions between increased permeability of the pulmonary vasculature and increased hydrostatic pressure on lung fluid flux, we measured water and blood contents of five equally thick slices of in situ perfused dogs' lungs that had been vertically suspended and, after experimental manipulations, rapidly frozen. Measurements were made under four sets of conditions (4 dogs each): 1) control; 2) increased left atrial pressure (Pla), 25 cmH2O relative to the bottom of the lung; 3) oleic acid; and 4) oleic acid and increased Pla. Significant interactions on lung water content were found between 1) oleic acid and increased Pla (P less than 0.005) and 2) oleic acid and height of the slice of lung (P less than 0.003). Blood content was significantly affected by interactions between 1) oleic acid and height of the lung slice (P less than 0.001) and 2) increased Pla and height of the lung slice (P less than 0.001). We conclude that there are significant interactions between increased permeability and hydrostatic pressure that affect regional lung water content and intrapulmonary distribution of blood.
Alcohol consumption in rats: effects on work capacity in the heat
Authors: Francesconi R. , Mager M.
Published: December 2017

To quantitate the effects of ingestion of ethanol (EtOH)-water mixtures on the ability to work in the heat (35 degrees C), adult male rats (250-350 g) were given 0, 4, 8, 12, or 16% EtOH as the sole source of drinking water for 14 days. The endurance capacity (treadmill time) of rats drinking 4% EtOH was similar to that of rats consuming water (32 vs. 32.9 min, respectively). However, the treadmill time of rats drinking of 16% EtOH was significantly (P less than 0.05) reduced when compared with that of animals drinking 4 or 8% EtOH. Maximal rectal and skin temperatures were likewise lower in the group consuming 16% EtOH, whereas increments in rectal and skin temperatures during treadmill exercise were unaffected. Although hematocrit and plasma protein levels were unaltered, plasma levels of the commonly reported indices of heat-exercise injury were exacerbated by consumption of increasing concentrations of EtOH. We concluded that ingestion of EtOH for 2 wk had minimal effects on thermoregulation and that the decrements in work capacity noted were probably the result of alterations in hepatic and muscle metabolism.
Atelectatic lobe blood flow: open vs. closed chest, positive pressure vs. spontaneous ventilation
Authors: Pirlo A. F. , Benumof J. L. , Trousdale F. R.
Published: December 2017

We measured lobar hypoxic pulmonary vasoconstriction (HPV) caused by both absorption atelectasis (AA) and nitrogen ventilation (N2) during conditions of a) open chest and positive-pressure ventilation (PPV), b) closed chest ad PPV, and c) closed chest and spontaneous ventilation (SV) and compared conditions a with b and b with c. In eight pentobarbital-anesthetized dogs we found that selective hypoxia of the left lower loe (LLL) caused by either AA or N2 resulted in the same percent decrease in the electromagnetically measured LLL blood flow whether the ches was open or closed to whether ventilation was by PPV or SV (range 58.3-65.0%). Whether the chest was open or closed and whether ventilation was by PPV or SV, reexpansion and ventilation of LLL AA with LLL N2 did not change LLL blood flow and indicated that there were no mechanical forces responsible for the decreased LLL AA blood flow. Differences in the degree of hypoxia, magnitude of transpulmonary pressure, and absolute pulmonary vascular pressure between LLL AA and N2 were considered to be minor. We conclude that the mechanism of decreased blood flow to an atelectatic lobe, whether the chest is open or closed and whether ventilation is by PPV or SV, is entirely due to HPV.
Diaphragmatic and genioglossal electromyogram responses to CO2 rebreathing in humans
Authors: Onal E. , Lopata M. , O'Connor T. D.
Published: December 2017

To assess the relationship between central control of upper airway and respiratory muscle, simultaneously recorded diaphragmatic electromyogram (EMGdi) and genioglossal EMG (EMG ge) responses to CO2 rebreathing were compared in five supine volunteers. Both EMGs were quantitated in terms of inspiratory peak moving time-average activity. In all subjects both EMGdi and EMGge increased linearly with increasing alveolar CO2 pressure (r = 0.93 +/- 0.04 and 0.87 +/- 0.07, respectively), resulting in a significantly linear EMGge vs. EMGdi relationship (r = 0.91 +/- 0.04). CO2 response slopes of both EMGs were similar and linearly related (r = 0.96, P less than 0.001) such that subjects with low EMGdi response also had a low EMGge response and vice versa. Although the onset of EMGge activity preceded that of EMGdi, and the pattern of both EMGs were different, inspiration duration of both EMGs were similar. These data indicate that in humans both diaphragm and genioglossus muscle share similar control mechanisms and suggest that upper airway function is intimately related to the regulation of breathing.
A modified Van Slyke apparatus
Authors: Brix O.
Published: December 2017

A modified micro-Van Slyke apparatus for analyzing gases in a 25- to 100-microliter sample of blood or other solutions is described. The method is based on the vacuum-extraction principle in which the gases are released for direct manometric measurement. A determination of total CO2 and total O2 content in blood can be completed in about 7 in. A commercial micro-Van Slyke apparatus (Thomas Magna-Matic manometer apparatus) requires 10-15 min for the same determination. The modified Van Slyke can be operated under field conditions without losing accuracy. The modified Van Slyke apparatus has greater reproducibility and accuracy than the commercial model.
Fast integrated flow plethysmograph for small mammals
Authors: Sinnett E. E. , Jackson A. C. , Leith D. E. , Butler J. P.
Published: December 2017

The accurate measurement of a forced vital capacity (FVC) maneuver in a small mammal requires that the plethysmograph in use have good response characteristics at high frequencies. We develop, on a theoretical basis, the behavior of zeroth-order (pressure type), first-order (flow type without inertance), and second-order (flow type with inertance) plethysmogrphs. The actual frequency response of a mouse-sized plethysmograph is then presented, and a technique for improving its response characteristics is described. A flat amplitude response (within 3% of a reference flow taken as truth) was obtained for sinusoidal inputs below 240 Hz. A phase lag with respect to the reference flow equivalent to a simple time delay of 1.4 ms was observed up to 150 Hz. A typical FVC curve for a mouse is shown, and criteria are provided for designing similar plethysmographs suitable for use with larger animals.
Collateral ventilation in excised human lungs
Authors: Berend N. , Skoog C. , Thurlbeck W. M.
Published: December 2017

Pressure-volume (PV) curves and single-breath nitrogen (SBN) washout traces were obtained in 32 excised human lungs. Comparison of the volumes at the onset of phage IV of the SBN traces (V phase IV) and the volumes at the inflection points (VIP) of the PV curves revealed V phase IV to be significantly larger than VIP. We postulated that V phase IV was caused by bulk airway closure and that the difference between V phase IV and VIP was due to collateral ventilation. To test this we correlated V phas IV -- VIP with age and emphysema grades of the lungs. Significant correlations were obtained, demonstrating that with increasing age and emphysema grade V phase IV -- VIP also increased. This is consistent with the documented evidence for decreased resistance to collateral ventilation with increasing age and emphysema. In addition, in a total of 86 lungs we demonstrated that with increasing age and emphysema there is an increasing incidence of total lack of sigmoid deviation in the PV curve.
Development of CO2 sensitivity: effects of gestational age, postnatal age, and sleep state
Authors: Guthrie R. D. , Standaert T. A. , Hodson W. A. , Woodrum D. E.
Published: December 2017

To determine the independent effects of sleep state, gestational age, and postnatal age on eucapnic ventilation and steady-state CO2 sensitivity, nine premature (146 +/- 3 days) and eight full-term (168 +/- 2 days) monkeys, Macaca nemestrina, from accurately timed conceptions were studied serially over the first 3 wk of life. Minute volume (VE)/kg,tidal volume (VT)/kg, and respiratory frequency were quantitated during rapid-eye-movement sleep (REM) and nonrapid-eye-movement sleep (NREM)in room air and when animals were breathing varied concentrations of cO2 in 21% O2. Eucapnic VE/kg and CO2 sensitivity [(deltaVE/kg)/delta PaCO2] increased progressively with advancing postnatal age during NREM sleep in grouped term and premature animals. CO2 sensitivity was not significantly different between REM and NREM sleep except in full-term animals at the highest postconceptual age studied (189 +/- 2 days) when [(delta VE/kg)/delta PaCO2] was lower in REM sleep than in NREM sleep (209 +/- 54 vs. 301 +/- 71 ml.min-1.kg-1.Torr-1; P less than 0.05, paired-t test). Gestational age had no measurable effect on eucapnic ventilation or CO2 sensitivity. These results support the hypothesis that REM sleep-induced depression of CO2 sensitivity develops in the neonatal monkey with advancing postconceptual age.
Myocardial norepinephrine turnover during induced hypothermia and rewarming
Authors: Jones S. B.
Published: December 2017

Norepinephrine (NE) turnover in myocardial tissue was measured in male golden hamsters (Mesocricetus auratus) during 1) continuous hypothermia, 2) rewarming from hypothermia initiated by exposure to 22 degrees C ambient, and 3) normothermic control state. Hypothermia was induced by exposure to 80% He-20% O2 atmosphere at 0 to -10 degrees C. At sequential periods after tritiated norepinephrine ([3H]NE) infusion, hamsters were killed by cervical transection and hearts were removed and analyzed for NE and [3H]NE content. Rate constants, turnover times, and turnover rates were determined from regression analysis of [3H]NE/micrograms NE tissue decay. Myocardial concentrations of NE were constant during NE-turnover measurements in each group. However, myocardial NE levels were reduced by 37% in both continuous hypothermia and rewarming from hypothermia compared with normothermic controls. NE turnover was highest during rewarming from hypothermia (0.34 micrograms.g-1.h-1), but no decay in myocardial [3H]NE was detectable during continuous hypothermia. Control animals had turnover values of 0.15 micrograms.g-1.h-1. Turnover data indicate severe depression in myocardial sympathetic nerve activity during hypothermia but a significant increase above normothermic control levels during rewarming from hypothermia.
A characterization of the respiratory pattern of gasping
Authors: St John W. M. , Knuth K. V.
Published: December 2017

The purpose of this investigation was to compare the respiratory pattern of gasping with eupnea and apneusis. Decerebrate, cerebellectomized, vagotomized, paralyzed and ventilated cats were used. The ventilatory pattern, assessed by phrenic nerve activity, was reversibly altered from eupnea to apneusis or gasping by use of a cooling-for, thermode positioned inm the rostral pons or through the pontomedullary junction, respectively. Irreversible apneusis or gasping resulted from brain stem lesions or freezing at appropriate loci. Analysis of phrenic activity revealed that the rates of onset and rise of the gasp were much greater than those of the eupneic or apneustic inspiration. Moreover, in contrast to eupnea or apneusis, neither the frequency nor the intensity of gasps was altered by hypercapnia, hypocapnia, or carotid chemoreceptor stimulation by sodium cyanide. Although hypoxia caused an increase in gasping frequency, this response was transient and not dependent on carotid chemoreceptor mechanisms. These results provide no support for the concept that common mechanisms localized in medulla, underlie the neurogenesis of all automatic ventilatory patterns.
Oxygen equilibrium properties of blood and hemoglobin of fetal and adult Weddell seals
Authors: Qvist J. , Weber R. E. , Zapol W. M.
Published: December 2017

Oxygen equilibria of whole blood and hemoglobins from adult and fetal Weddell seals are reported. The maternal blood shows a lower O2 affinity than the fetal blood (halfsaturation O2 tension P50 = 26.9 +/- 1.18 and 21.4 +/- 1.25 Torr, respectively, at 37 degrees C and pH 7.4), and a greater Bohr effect (delta log P50/delta pH = -0.49 and -0.31, respectively, at pH 7.4-6.8), correlated with higher red cell 2,3-diphosphoglycerate (2,3-diphosphoglycerate (2,3-DPG) concentrations (6.45 +/- 0.81 mmol.1-1, compared to 2.65 +/- 0-42 mmol.1-1 in the fetus). Both the maternal and fetal erythrocytes contain two major and two minor hemoglobin components occurring in the same ratio and the 2,3-DPG-free whole hemolysates, as well as the isolated major components from each stage, show the same oxygenation properties, ascribing the whole-blood differences to the higher adult DPG levels. A 2,3-DPG effect also appears to account for the disparity in the Bohr effects, which will favor unloading of O2 from the maternal circulation during diving as maternal and fetal blood pH decrease in parallel.
Effects of airway occlusion at functional residual capacity in pentobarbital-anesthetized kittens
Authors: Trippenbach T. , Zinman R. , Mozes R.
Published: December 2017

The effects or airway occlusion at the end of inspiration on timing parameters and the "integrated" phrenic activity were studied in 1- to 21-day-old kittens at two levels of pentobarbital anesthesia before and after bilateral vagotomy. In intact kittens during the first 2 wk of life, instead of the classical effects of airway occlusion at functional residual capacity (FRC), shortening of both inspiration and expiration, a decrease in amplitude and rate of rise of the integrated phrenic activity, or augmented breaths were recorded. These effects were not altered by an additional dose of pentobarbital sodium. In kittens of all ages, airway occlusion performed after bilateral vagotomy had no significant effects on either timing and phrenic activity. Therefore, vagally mediated reflexes are probably responsible for the paradoxical effects of airway occlusion at FRC. However, a possible contribution of the chest wall receptors cannot be excluded.
Hypoxia effects on plasma volume shifts at rest, work, and recovery in supine posture
Authors: Miles D. S. , Bransford D. R. , Horvath S. M.
Published: December 2017

The purpose of this study was to determine the effects acute exposure to hypoxia (less than 1.5 h; gas mixture 12.6% O2–87.4% N2) has on plasma volume (PV) shifts during rest and exercise. Nine unacclimatized males performed identical protocols in the supine posture in both normoxic (N) and hypoxic (H) conditions. The protocol was rest 60 min, submaximal exercise (PWC 140, work rate eliciting a heart rate of 140 beats/min) for 30 min, immediately followed by maximal exercise, and 10 min of passive recovery. There were slight but significant losses of 2.7 and 1.4% PV at rest in H and N conditions, respectively. At the same relative intensity of submaximal exercise (work loads reduced by 22% in H conditions), PV losses were nearly identical (N = 11.2%, H = 11.8%). There was a further PV efflux subsequent to maximal exercise (N = 7.9%, H = 5.2%). The maximum PV efflux, from the beginning of rest to the end of maximal exercise, was 20% for both conditions. Total plasma protein (PP) content was unchanged during rest or exercise for either N or H conditions. After 10 min of recovery, restitution of PV was 10% below preexercise values for both N and H conditions. We conclude that acute hypoxic exposure does not influence the loss of VP or PP during submaximal or maximal exercise.
Measurement of dead space ventilation using a pHa servo-controlled ventilator
Authors: Coon R. L. , Zuperku E. J. , Kampine J. P.
Published: December 2017

A control system for the systemic arterial pH (pHa) servo control of mechanical ventilation has recently been developed. If pHa is maintained constant by the change, separation of minute volume into alveolar ventilation and physiological dead space ventilation (VE = fVA VDp) can be manipulated to show that VDp = (VE1 - VE 2)/(f1 - fe) where f1 and f2 are different ventilator frequencies and VE1 and VE2 are expired minute volumes at these frequencies. Also, added dead space can be measured. VDadded = (VE2 - VE1)/f where VE1 and VE2 are the minute volumes before and after the dead space was added. The validity of these equations was tested in the anesthetized dog. The measured added dead space was in close agreement with the volume of dead space which was added and with that measured by another independent method. The measurement of VDp, probably as a result of tidal volume-related changes in VDp, did not agree as well with VDp measured by an independent method.
Reduced norepinephrine response to dynamic exercise in human subjects during O2 breathing
Authors: Hesse B. , Kanstrup I. L. , Christensen N. J. , Ingemann-Hansen T. , Hansen J. F. , Halkjaer-Kristensen J. , Petersen F. B.
Published: December 2017

The purpose of this investigation was to study the influence of hyperoxia on catecholamine response to dynamic exercise. While breathing either 21 or 100% O2 seven subjects performed submaximal bicycle exercise. Arterial blood pressure was similar in both exercise experiments. The CO2 output was not influenced by 100% O2 breathing, but increments in plasma lactate concentration were reduced. The increases in plasma norepinephrine and epinephrine concentrations and heart rate were significantly lower during 100% O2 than during 21% O2 breathing. The results suggest that O2 plays an important role in the regulation of sympathetic nervous activity during dynamic exercise in humans.
An O2-CO2 mixing system for studies on water-breathing animals
Authors: Rodeau J. L. , Malan A.
Published: December 2017

A simple system based on single-stage gas-stream mixing produces accurate O2-CO2 mixtures suitable for studies on water-breath-ing animals. CO2 fractions as low as 0.05% can be obtained, with an output pressure up to 25 kPa and a full range accuracy of +/- 1%.
Pulmonary mechanics and gas exchange in seated normal men with chest restriction
Authors: Klineberg P. L. , Rehder K. , Hyatt R. E.
Published: December 2017

Lung volumes, static pressure-volume curves, maximal expiratory flow-volume curves, right-to-left intrapulmonary shunts (Qs/Qt), and distributions of ventilation and perfusion relative to the alveolar ventilation and perfusion ration (VA/Q) were determined in seated normal men before chest strapping while breathing air (Cair) and during chest strapping while breathing air (Sair) or 100% oxygen (So2). With Sair and So2, mean vital capacity was reduced by 44% from control. Elastic recoil pressure [Pst(L)] of the lung at 50% control total lung capacity (TLC) increased significantly (P less than 0.05) from 4.64 +/- 0.39 cmH2O (mean +/- SE) to 7.00 +/- 0.47 cmH2O with Sair and to 7.24 +/- 0.70 cmH2O with So2. Maximal expiratory flow at 50% of control TLC increased significantly (P less than 0.05) from 3.22 to 0.25 l/s (mean +/- SE) to 5.84 +/- 0.69 l/s with Sair and to 5.50 +/- 0.68 l/s with So2. With Sair, no significant increase in Qs/Qt from control was observed. With So2, mean Qs/Qt increased significantly (P less than 0.05) from 0 to 2.2 +/- 0.9% of the cardiac output. It is therefore unlikely that the development of atelectasis, as indicated by an increase in Qs/Qt, accounts for the increase in Pst (L) with Sair and So2. Current evidence suggests that either change in alveolar surface compliance or distortion of the lung or both are responsible for the increased recoil pressure but that neither mechanism alone appears to explain it totally.
Adrenoceptor control of lung fluid and protein exchange
Authors: Hakim T. S. , Minnear F. L. , van der Zee H. , Barie P. S. , Malik A. B.
Published: December 2017

We studied the effects of alpha- and beta-adrenergic antagonists on lung fluid and protein exchange in anesthetized sheep. alpha-Adrenergic blockade with 2 mg/kg phentolamine caused a transient and small decrease in lung lymph flow (Qlym), which was associated with a decrease in mean pulmonary arterial pressure (Ppa); but the steady-state Qlym and mean left atrial pressure were not different from base-line values. In contrast, beta-adrenergic blockade with propranolol (2 mg/kg) caused an increase in Qlym from a base-line value of 7.7 +/- 2.2 ml/h to a steady-state value of 10.6 +/-2.3 ml/h within 2 h (P less than 0.05), which was not associated with a change in Ppa. The increase in Qlym persisted for the 4-h duration of the study. The 39% increase in Qlym after propranolol was associated with a 50% increase in transvascular protein clearance (CL), whereas in control animals the 100% increase in Qlym after left atrial hypertension was associated with only a 36% increase in CL, indicating increased transvascular transport of proteins after propranolol. The transient decrease in Qlym after phentolamine may be due to the short-lasting decreased in pulmonary microvascular pressure and vascular surface area. However, the long-lasting increases in Qlym and CL after propranolol may be due to an increase in vascular surface area and to an increase in endothelial permeability of proteins. The results suggests that beta-adrenergic receptors regulate the transendothelial transport of fluid and proteins.
Ventilation during prolonged hypercapnia in the rat
Authors: Lai Y. L. , Lamm J. E. , Hildebrandt J.
Published: December 2017

Awake rats, with chronically implanted arterial catheters and abdominal thermistors, were continuously exposed to 5 or 7% CO2 in air in an environmental chamber for up to 3 wk. To obtain measurements, rats were transferred to a body plethysmograph flushed with the same CO2 mixture, and, after stabilization, O2 consumption (Vo2), ventilation (VE), and arterial blood gases (ABG) were determined. After 2-h exposure, VE, tidal volume/inspiratory time (VT/TI), and VO2 were significantly increased. Thereafter, VE and VT/TI fell gradually with time, the largest decrease occurring within the 1st day of exposure. The increase in VO2 was maintained up to 3 days and then declined. ABG revealed extensive metabolic compensation for respiratory acidosis within 3–7 days. delta(VT/TI) correlated well with delta VE and delta [HCO3]a (P less than 0.05). It is likely that the gradual return toward normal pHa reduces ventilatory drive (VT/TI), which in turn lowers VE. Estimated alveolar ventilation did not decrease consistently with time in parallel with VE, suggesting that the early ventilatory overshoot might also be due to an increase in dead space.
Computer-derived image compositing
Authors: Wall R. J. , Sobin S. S. , Karspeck M. , Lindal R. G. , Tremer H. M. , Fung Y. C.
Published: December 2017

A computer-derived composite image is obtained of the details contained in successive photomicrographs taken by optical sectioning of the collagen networks in the pulmonary interalveolar wall. Three-dimensional information is therefore contained in a two-dimensional portrayal, providing a basis for computer digital analysis otherwise not readily available.
Rat lung surfactant kinetics biochemical and morphometric correlation
Authors: Young S. L. , Kremers S. A. , Apple J. S. , Crapo J. D. , Brumley G. W.
Published: December 2017

Biochemical and morphometric techniques were combined to estimate the distribution and flux or rat lung disaturated phosphatidylcholine (DSPC) in surfactant pathways. We found 126 +/- 8 X 10(6) alveolar epithelial type II (AEP II) cells per lung, each containing 150 +/- 30 lamellar bodies (LB). High yields of LB were isolated by centrifugation of lung homogenates with a discontinuous sucrose density gradient. Measurement of DSPC in LB and alveolar lavage (LV) material demonstrated that only 30% (LB 14%, LV 16%) of lung DSPC was present in these surfactant compartments. Radiolabeling of lung DSPC with [14C]palmitate demonstrated a product-precursor-relationship between LB and LV and a surfactant-associated DSPC flux of 90 microgram-lung-1 X h-1. We conclude that, although only 16% of lung DSPC is in an intracellular surfactant pathway at any time, all this DSPC is ultimately secreted onto the alveolar surface.
Model of elasticity of the human lung
Authors: De Wilde R. , Clement J. , Hellemans J. M. , Decramer M. , Demedts M. , Boving R. , Van de Woestijne K. P.
Published: December 2017

A model of the elasticity of the human lung has been developed to evaluate the relative importance of the characteristics of the lung parenchyma, of thorax configuration, and of gravity on the vertical gradients of pleural pressure and regional volumes, and on the linear displacements of lung tissue, of various lung volumes. The predictions of the model are compared with available experimental data. It is suggested that the bulk elasticity modulus of the human lung is high with respect to that of canine lungs, that the shearing forces are low ("effective" Poison's ratio of about 0.4-0.45), and that the variations of regional pleural pressures and volumes during deflation are determined primarily by the interaction between lung weight and changes in thorax configuration.
Changes in brain surface pH during acute isocapnic metabolic acidosis and alkalosis
Authors: Javaheri S. , Clendening A. , Papadakis N. , Brody J. S.
Published: December 2017

It has been thought that the blood-brain barrier is relatively impermeable to changes in arterial blood H+ and OH- concentrations. We have measured the brain surface pH during 30 min of isocapnic metabolic acidosis or alkalosis induced by intravenous infusion of 0.2 N HCl or NaOH in anesthetized dogs. The mean brain surface pH fell significantly by 0.06 and rose by 0.04 pH units during HCl or NaOH infusion, respectively. Respective changes were also observed in the calculated cerebral interstitial fluid [HCO-3]. There were no significant changes in cisternal cerebrospinal fluid acid-base variables. It is concluded that changes in arterial blood H+ and OH- concentrations are reflected in brain surface pH relatively quickly. Such changes may contribute to acute respiratory adaptations in metabolic acidosis and alkalosis.
Role of fascia in maintenance of muscle tension and pressure
Authors: Garfin S. R. , Tipton C. M. , Mubarak S. J. , Woo S. L. , Hargens A. R. , Akeson W. H.
Published: December 2017

The effect of fasciotomy on muscle tension (measured by a force transducer attached to the tendon) and interstitial fluid pressure (measured by Wick catheters in the muscle belly) was studied in the anterolateral compartments of 13 dog hindlimbs. Muscle tension and pressure were monitored in the tibialis cranialis muscle after low- and high-frequency stimulation of the peroneal nerve to produce twitch- and tetanic-type contractions. Fasciotomy decreased muscle force during the low-frequency stimulation by 16% (35.3 +/- 4.9 to 28.4 +/- 3.9 N) and during the high-frequency stimulation by 10% (60.8 %/- 4.9 to 54.8 +/- 3.9 N). Muscle pressure decreased 50% after fasciotomy under both conditions, 15 +/- 2 to 6 +/- 1 mmHg and 84 +/- 17 to 41 +/- 8 mmHg), respectively. Repeated functional evaluations during the testing procedure indicated that muscle fatigue was not a major factor in these results. It was concluded that fascia is important in the development of muscle tension and changes in interstitial pressure. Furthermore, the results raised questions concerning the merits of performing a fasciotomy for athletes with a compartment syndrome.
Increased pulmonary vascular permeability following acid aspiration
Authors: Grimbert F. A. , Parker J. C. , Taylor A. E.
Published: December 2017

The effect of hydrochloric acid aspiration on transvascular fluid and protein flux and lung water content was studied in 21 anesthetized dogs. We measured steady-state lung lymph flow, pulmonary arterial and left atrial pressures, and the concentration of total protein and albumin in both lymph and plasma after intratracheal instillation of 2 ml/kg 0.1 N HCl. Acid injury produced a twofold increase in lung lymph flow and lymph protein clearance when compared with control. This indicated an increase in pulmonary microvascular permeability. In dogs given 25 g concentrated human albumin and 1 mg/kg furosemide 10 min after the acid injury, the acid-induced increase in fluid filtration was prevented. However, the decrease in fluid filtration was not attributed to an increase in the transvascular protein osmotic pressure gradient but to a more direct effect of furosemide. Treatment with furosemide alone prevented the increase in lung lymph flow induced by acid injury, whereas albumin alone did not. In all acid-injured animals there was an increase in lung water when compared wtih control. Therefore acid aspiration produced localized areas of damage to filtration vessels that lead to increased leakage of protein and water. Furosemide treatment prevented much of this increased fluid and protein flux by an undefined mechanism.
Evidence for a sodium electrogenic pump in airway smooth muscle
Authors: Souhrada M. , Souhrada J. F. , Cherniack R. M.
Published: December 2017

We tested the hypothesis that the resting membrane potential (Em) of guinea pig and bovine airway smooth muscle (ASM) (m. trachealis transversus) might be influenced by a Na+ electrogenic pump. To determine the Em of ASM, glass microelectrodes filled with 3 M KCI and offering an impedance between 40 and 80 M omega were used. After incubation a normal oxygenated physiological salt solution (PSS) [pH, 7.38 +/- 0.02 (SD); temp, 37 +/- 0.5 degrees C (SD)] for 60 min, the Em of guinea pig ASM was -62.5 +/- 1.25 (SE) mV (successful impalement of 437 cells of 37 tracheal preparations from 37 different animals) and that of bovine ASM was -60.0 +/- 1.5 mV (successful impalement of 306 cells of 26 tracheal preparations from 26 different animals). Tracheal preparation consisted of 10-mm-long segments of cervical or intrathoracic portions of the trachea. Approximately 30% of the cells of both species exhibited spontaneous electrical activity (slow waves). Studies to determine whether an electrogenic pump was present revealed that a) ouabain (10(-5) M), a specific inhibitor of the Na+ pump, causes depolarization of ASM in both species; b) exposure of ASM to a K+-free solution resulted in a similar depolarization followed by a hyperpolarization; c) exposure to normal PSS after "Na+ loading" resulted in significant hyperpolarization of ASM when these preparations were returned to normal PSS; and d) Em of ASM decreased on exposure to a low temperature (21, 25, and 29 degrees C) and increased at a high temperature (40 degrees C). It is concluded that an active electrogenic pump is present in guinea pig and bovine airway smooth muscle.
Nonelectrolyte permeability of canine tracheal epithelium
Authors: Man S. F. , Thomson B. R.
Published: December 2017

We examined the nonelectrolyte permeability characteristics of canine tracheal epithelium in vitro and confirmed that the transepithelial potential difference was 26.3 +/- 2.2 mV, lumen negative. Exposure of the epithelium to a sucrose osmotic load resulted in a streaming potential (SP); a linear relationship was noted between osmotic load and SP. The presence of an osmotic load did not change the short-circuit current and the SP disappeared after removal of the osmotic load. The SP developed with urea, thiourea, D-xylose, and l-glycine were similar to the SP developed for equimolar concentrations of sucrose. The urea and insulin spaces were similar magnitude. When the bulk phase was stirred at 600 rpm, the effective thickness of the unstirred water layer (UWL) external to the epithelial surface was 144 +/- 12 micron. These results support the suggestion that the Staverman reflection coefficients (sigma) of these probe molecules are similar, the estimates of sigma are valid despite the presence of an UWL, and the tracheobronchial epithelium has a pore size smaller than the hydrodynamic radius of urea.
Effect of hypercapnia on net filtration of fluid in the lungs of awake newborn lambs
Authors: Haberkern C. M. , Bland R. D.
Published: December 2017

To study the effect of hypercapnia on net transvascular filtration of fluid in newborn lungs, we measured pulmonary arterial and left pressures and collected lung lymph from 11 awake 2-wk-old lambs as they spontaneously breathed a gas mixture rich in carbon dioxide. After a 2-h control period in air, the lambs breathed 8-11% carbon dioxide mixed with air and nitrogen for 2-6 h. Average pulmonary arterial pressure and blood flow to the lungs increased during hypercapnia, but pulmonary vascular resistance did not change. In all cases, hypercapnia led to an acute transient increase in lymph flow. During sustained hypercapnia, however, flow of lymph was not significantly different from flow measured during the control period. The concentration of protein in lymph decreased at the onset of hypercapnia and remained low during sustained hypercapnia. These results suggest that acute hypercapnia increases net filtration by increasing the transvascular gradient of hydraulic pressure, whereas, in a "steady-state," neither hypercapnia nor the tachypnea that accompanies it alters net transvascular filtration of fluid in the lungs of unanesthetized newborn animals.
Effects of different-size microemboli on lung fluid and protein exchange
Authors: Johnson A. , Malik A. B.
Published: December 2017

We examined the effects of embolization with different-size glass-bead microemboli on pulmonary transvascular fluid and protein exchange in the sheep lung lymph fistula preparation. Embolization with either 200- or 500-micron-diameter glass beads caused comparable increases in pulmonary vascular resistance, which were sustained for the duration of the study. The 200-micron beads increased pulmonary lymph flow (Qlym) and did not affect the lymph-to-plasma protein concentration ratio (L/P), whereas injection with 500-micron beads increased Qlym and decreased L/P. The latter changes were comparable to those observed after an increase in pulmonary microvascular pressure induced by left atrial hypertension, suggesting that the 500-micron beads increase the Qlym by raising the microvascular hydrostatic pressure. In contrast, the 200-micron beads increased the transvascular clearance of proteins to a greater extent, since L/P did not decrease as Qlym increased. These findings suggest that lung vascular permeability increases after embolization with smaller (200-micron) but not with larger (500-micron) emboli. The increased permeability after embolization with small beads may be due to transmission of the permeability-increasing substances to the downstream capillaries via the collateral pulmonary arteries. This would not occur after embolization with larger emboli if these obstructed the pulmonary arteries upstream from branching points of the collateral arteries. The ultrafiltration of protein-poor plasma after embolization with the 500-micron beads may reflect increased fluid filtration in unobstructed microvessels due to increase in the microvascular hydrostatic pressure.
Respiratory muscle fatigue during cardiogenic shock
Authors: Aubier M. , Trippenbach T. , Roussos C.
Published: December 2017

The effect of cardiogenic shock (tamponade) on respiratory muscles performance was studied in 13 dogs breathing spontaneously. These 13 dogs were compared with 7 dogs artificially ventilated and paralyzed. Cardiac output amounted in both groups to 25-35% of the control value and was maintained constant. None of the dogs were hypoxic. All the spontaneously breathing dogs died on the average 140 +/- 15 min after the onset of cardiogenic shock, whereas the seven dogs artificially ventilated were all alive after 3 h and then killed. Death in the spontaneously breathing dogs was secondary to respiratory failure. Transdiaphragmatic pressure increased during the 1st h by 152 +/- 25% of control and then decreased by 286 +/- 18% in relation to the peak value before the death of the animals. No major changes in the mechanical properties of the respiratory system occurred. The decrease in transdiaphragmatic pressure occurred despite a marked increase per breath in the amplitude of the integrated electrical activity of the diaphragm and of the phrenic nerve. It is concluded that the ventilatory failure of cardiogenic shock is due to an impairment of the contractile process of the respiratory muscles. Artificial ventilation avoids respiratory failure and prolongs survival, which may bear important therapeutic implications.
Lipid fluidity in lung surfactant: monolayers of saturated and unsaturated lecithins
Authors: Hawco M. W. , Davis P. J. , Keough K. M.
Published: December 2017

Monolayers of saturated or unsaturated lecithins (PCs) could be compressed to near-zero surface tension (gamma) when they were below the gel-to-liquid crystalline transition temperature (Tc) of the PC, whereas, when above Tc, they collapsed at gamma of 15-23 mN X m-1. Thus PCs with ordered, but not necessarily saturated, chains are required to achieve low gamma. At 37 degrees C the minimum gamma reached by monolayers containing dipalmitoyl PC (DPPC; Tc = 41 degrees C) plus 1-stearoyl-2-oleoyl PC (SOPC; Tc = 6 degrees C) depended on the proportions of the two lipids and the compression rate. When compressed at 1 cm2 X s-1, monolayers of mixtures containing less than 50% SOPC were capable of achieving gamma less than 9 mN X m-1. When the proportion of unsaturated lecithin was high (70%), compression at 1 cm2 X s-1 was insufficient to form a monolayer capable of reaching a very low surface tension. Exclusion of fluid lipid during compression could account for these observations.
Breath-to-breath monitoring of inspiratory occlusion pressures in humans
Authors: Ward S. A. , Agleh K. A. , Poon C. S.
Published: December 2017

A pneumatically drive occlusion device has been designed to implement brief (ca. 130 ms) inspiratory airway occlusion and to monitor the associated inspiratory occlusion pressure (P100) on a breath-to-breath basis in humans. The device, which has a low resistance when patent, provides no discernible modulation of ventilation during steady and nonsteady states of moderate intensity cycle-ergometer exercise. With this technique, it is possible to undertake investigations of dynamic as well as steady-state P100 responses to stimuli such as extensive, inhaled CO2, and hypoxia.
Mechanics and energetics of stilt walking
Authors: Vaida P. , Anton-Kuchly B. , Varene P.
Published: December 2017

Three subjects were studied walking on a sports track with and without 1-m-long stilts. They were asked to walk in different ways. Pace length, step rate, heart rate, and oxygen consumption were measured under both conditions at different speeds. The results show that walking speed is generally faster for stilt walking than for normal walking. The higher speed is achieved due to increased pace length in spite of a decrease in step rate. The relationship between energy expenditure and walking speed is approximately the same in both cases. This result may be explained by two opposing factors: increase of pace length and decrease of step rate decrease the energy requirements of stilt walking, but the foot loading presented by the stilt walking exaggerates these conditions and increases energy expenditure.
Endotoxin reverses the decreased tolerance of rats to greater than 95% O2 after preexposure to lower O2
Authors: Frank L.
Published: December 2017

Bacterial endotoxin has a marked protective effect against pulmonary O2 toxicity in rats placed directly in atmospheres of greater than 95% O2. To determine whether endotoxin treatment during exposure to relatively low levels of hyperoxia would protect rats from the accelerated O2 toxicity that normally occurs when these rats are transferred to greater than 95% O2, we gave endotoxin or saline 1) during exposure to 40% O2 (5 days), or 2) during exposure to 40%-60%-85% O2 (2 days at each level). Saline-treated rats showed significantly decreased tolerance on transfer to greater than 95% O2 [LT50 = 47.5 h (exposure 1) and 48.5 h (exposure 2)] compared with normal nonpreexposed rats (LT50 = 66 h). In contrast, endotoxin-treated rats showed a marked tolerance on transfer to greater than 95% O2 [% of rats surviving 72 h = 14/16 (88%) endotoxin-treated vs. 2/16 (13%) saline-treated]. The endotoxin-treated rats, unlike the saline-treated rats, showed significant elevations in lung superoxide dismutase, catalase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase levels after the O2 preexposure periods; this may account for their significantly improved tolerance when challenged with greater than 95% O2 exposure.