bluuebunny/crossref_metadata_2025 huggingface dataset:
Lobar flow patterns in a hollow cast of canine central airways
Authors: Snyder B. , Jaeger M. J.
Published: December 2017

To demonstrate that the regional partitioning of flow in central airways is direction dependent, we compared inspiratory and expiratory lobar flows in a hollow rigid cast of canine lungs. Lobar flows were measured by a hot-wire anemometer, simultaneous tracheal flows by a pneumotachograph, and data displayed as (lobar) flow-(tracheal) flow curves. For tracheal airflows between 50 and 370 ml/s, we found that inspiratory apical flows were smaller, and basal flows larger, than corresponding expiratory distributions. This effect was largely extinguished by substituting a gas mixture of 85% He-15% N2; resulting regional flows were comparable to expiratory distributions obtained on room air. Thus canine central airways structure induces a kinematically irreversible flow pattern, consistent with a model of “cascade flow” in which branching structure modifies the distribution only of inspiratory flow. These results support Fowler's concept that lung regions fill and empty sequentially and may be pertinent to analyses of regional washout.
Time course of posthyperventilation breathing in humans depends on alveolar CO2 tension
Authors: Folgering H. , Durlinger M.
Published: December 2017

The time course of the decrease in ventilation immediately after 1 min of voluntary isocapnic hyperventilation was studied in eight healthy subjects. The hyperventilation tests were done at three different levels of alveolar CO2 tension (PACO2), and at each PACO2 level with a fixed respiratory frequency and with a freely chosen (increased) frequency. The time constant of the decrease in ventilation after free-frequency hyperventilation was inversely related to the PACO2, with a regression equation of tau 1 (s) = 78.6 - 1.2 PACO2. After the fixed-frequency hyperventilation, the time constant of the decrease in ventilation was virtually zero and independent of PACO2. These results do not agree with earlier findings in anesthetized animals. The fact that hypocapnia increases the excitability of neurons might explain the findings. The extreme respiratory afterdischarge phenomenon in hypocapnic patients suffering from the hyperventilation syndrome is consistent with the outcome of this study.
Effect of cold exposure on various sites of core temperature measurements
Authors: Livingstone S. D. , Grayson J. , Frim J. , Allen C. L. , Limmer R. E.
Published: December 2017

Rectal, esophageal, auditory canal, gastrointestinal tract, and sublingual temperature were recorded on five young Caucasian males who, in an environment of -32 degrees C and 11-km/h wind, sat during one 90-min exposure and walked on a treadmill at 2.9 km/h during another. The clothing permitted cooling of their torsos while giving adequate protection to their extremities. Control exposures involved subjects sitting in still air at 24–26 degrees C dressed only in thermal underwear. In the control environment all of the internal body temperatures measured gave comparable and consistent values; however, cold exposure affected the various sites differently. Esophageal temperatures fluctuated rapidly as a result of subjects swallowing cold saliva. Sublingual temperatures were below the lower limit of a clinical thermometer, possibly because of facial cooling. Auditory canal temperatures were low, perhaps also because of facial cooling. Rectal temperatures were high as were the gastrointestinal tract temperatures, due perhaps to local heat production in response to cold stimulation. Metabolic rate increased initially in the cold and again toward the end of the cold exposure.
Mechanical heart-lung interaction with positive end-expiratory pressure
Authors: Wallis T. W. , Robotham J. L. , Compean R. , Kindred M. K.
Published: December 2017

Recent reports have suggested that positive end-expiratory pressure (PEEP) depresses left ventricular (LV) function or shifts LV pressure-volume (PV) relationships due to neural, humoral, or mechanical events. These studies have usually utilized pressures measured during expiration. To study the mechanical effects of PEEP in expiration and inspiration, the circulation was arrested in 12 open-chest dogs, and the coronaries were perfused with a cold cardioplegic agent. Balloons were placed in the ventricles to measure ventricular pressures. Shifts in cardiopulmonary blood volume were prevented by venting the atria to atmosphere. Having ablated neural reflexes and humoral changes, we varied ventricular volumes, chest wall compliance, tidal volume, and PEEP. We found that isovolumic ventricular pressures (relative to atmosphere) increase with PEEP (P less than 0.001), and heart-lung interaction with PEEP is significantly greater in inspiration (P less than 0.001). The effect of PEEP is modified by heart volume (P less than 0.01) and respiratory system compliance (P less than 0.01). We conclude that a mechanical compressive force can be applied to the heart by the lungs as they expand, and this may explain the previous reports of diminished LV function or LV diastolic compliance with PEEP and, in part, explain the decreased cardiac output associated with PEEP. The marked increase in mechanical compressive forces applied to the heart during inspiration with PEEP may have far greater hemodynamic consequences than events during expiration.
Paraquat inhibits mixed-function oxidation by rat lung
Authors: Aldrich T. K. , Fisher A. B. , Forman H. J.
Published: December 2017

The effect of paraquat on 7-ethoxycoumarin (7-EC)deethylation, an NADPH-dependent cytochrome P-450-linked reaction, was studied in isolated rat lungs. Control lungs oxidatively deethylated 7-EC at a constant rate, metabolizing 178 +/- 12 nmol/g dry wt in 50 min (n=3, mean +/- SE). When glucose was omitted from the perfusate, 7-EC deethylation was lower (85 +/- 17 nmol/g, P less than 0.05), and the rate progressively decreased, suggesting inadequate pentose shunt regeneration of NADPH. During perfusion with paraquat (10(-3) M), 7-EC metabolism was still lower (75 +/- 5 nmol/g in the presence of glucose and 18 +/- 4 nmol/g in the absence of glucose, P less than 0.05). Addition of lactate plus pyruvate partially restored 7-EC deethylase activity in control lungs but had no effect in lungs perfused with paraquat. Varying perfusate paraquat concentrations (10(-6) to 10(-3) M) inhibited 7-EC deethylation in a dose-dependent fashion (r = 0.79, P less than 0.02). Oxidative demethylation of p-nitroanisole, another cytochrome P-450-linked reaction, was similarly inhibited by paraquat. In contrast, microsomes isolated from paraquat-perfused lungs showed no inhibition of 7-EC metabolism (measured in the presence of an NADPH-regenerating system). We conclude that paraquat depletes NADPH in the isolated lung to a sufficient extent to impair mixed-function oxidation. Such NADPH depletion may play a role in the toxicity of paraquat.
Effect of central vascular engorgement and immersion on various lung volumes
Authors: Buono M. J.
Published: December 2017

The purpose of this study was to determine the relative contribution of central vascular engorgement (CVE) and increased hydrostatic pressure on various lung volumes during head-out immersion in water. Residual volume (RV) and vital capacity (VC) were determined on 12 male volunteers under three randomly assigned conditions: control, CVE, and immersion. CVE was produced via G-suit inflation. There were significant (P less than 0.01) mean decreases, compared with the control value, of 4.9% (280 ml) and 5.9% (340 ml) in VC during CVE and immersion, respectively. RV was not significantly changed across the three conditions. It was concluded that more than 80% of the decrease in VC during immersion can be attributed to CVE. However, the mechanism by which CVE decreased VC is still unclear. In addition, these data suggest that RV is relatively insensitive to the increase in CVE normally associated with immersion. Therefore, during immersion, RV is not simply the result of the balance of these opposing forces (i.e., CVE and hydrostatic pressure), as previously suggested.
Citric acid airway constriction in dogs with hyperreactive airways
Authors: Hirshman C. A. , Peters J. , Downes H. , Leon D. , Lynn R. K. , Butler J. , Hanifin J. M.
Published: December 2017

To understand the mechanisms underlying the bronchoconstrictor response to 10% citric acid administered for 5 min in Basenji-Greyhound (BG) dogs, we evaluated the protection afforded by atropine (0.2 and 0.4 mg/kg iv) and by aerosols of isoproterenol (1 mg/ml) and cromolyn sodium (20 mg/ml). In untreated dogs, citric acid increased pulmonary resistance by 4.6- to 11.5-fold and decreased dynamic compliance (Cdyn) to 45–55% of the control response. Isoproterenol and cromolyn sodium significantly reduced the response, whereas atropine did not. Moreover we have demonstrated in the arterial plasma of these dogs a slow-reacting substance (SRS) after, but not before, citric acid challenge. This SRS exhibits both pharmacologic properties and chemical characteristics similar to leukotrienes. We conclude that mediators of immediate-type hypersensitivity rather than reflex mechanisms play a dominant role in the production of airway constriction during citric acid (5-min) challenge in BG dogs.
Reproducibility of cardiopulmonary effects of different endotoxins in the same sheep
Authors: Traber D. L. , Adams T. , Henriksen N. , Traber L. D. , Thomson P. D.
Published: December 2017

This study compares qualitative and quantitative differences between the cardiopulmonary responses to Salmonella typhimurium and Escherichia coli 055:B5 endotoxins (Difco) in the same sheep model. Lipopolysaccharides, 0.75 micrograms/kg, were infused into chronically instrumented sheep over 30 min. Cardiopulmonary and pulmonary lymph flux data were collected for 2 h prior to and 6 h following this. One week later the sequence was repeated with another endotoxin. The administration of the two endotoxins was varied: some received S. typhimurium first; others received E. coli. A total of 13 animals were studied; 8 had intact pulmonary lymphatic catheters. Following each injection of endotoxin these animals showed a typical response of early high pressure-mediated increase in pulmonary lymph flow and later lymph flow elevation associated with a very mild increase in microvascular pressure and lymph with normal protein levels. These changes were associated with hemoconcentration, lowered arterial oxygen partial pressure, cardiac index, and blood neutrophil count. It is concluded that Difco S. typhimurium and E. coli endotoxins are similar in their mechanism of action and potency and can be studied in the same animal.
Temperature sensitivity of skeletal muscle in the conscious goat
Authors: Jessen C. , Feistkorn G. , Nagel A.
Published: December 2017

A method has been developed to test the hypothesis that the deep tissues of the legs, e.g., skeletal muscle and/or periosteum, contain thermosensitive elements feeding signals into the temperature-regulating system. Stainless steel thermodes of 10 to 12-mm diameter and 100 to 150-mm length were chronically implanted into the marrow spaces of both humeri and femora, all of which have wide cavities and thin walls. Perfusing the thermodes with water of 0 degree C altered the temperature of the deep muscle layers by several degrees. The animals were further equipped with intravascular heat exchangers, which served to keep general body temperature constant during periods of leg cooling. Eighty experiments were performed in a hot and dry environment. During the middle period of each experiment the legs were cooled by perfusing the thermodes with water of 0 degree C. This caused respiratory evaporative heat loss to decrease by 0.15–0.20 W/kg. The small but significant response occurred at constant general body temperature and is therefore indicative of a local effect of the cooling on deep thermosensitive elements in the legs themselves and a neural afferent transmission of temperature signals into the temperature-regulating system.
Sympathoadrenal responses to cold and ketamine anesthesia in the rhesus monkey
Authors: Kolka M. A. , Elizondo R. S. , Weinberg R. P.
Published: December 2017

The effect of cold exposure on the sympathoadrenal system in primates was studied with and without ketamine anesthesia in eight adult rhesus monkeys. Each monkey was placed in a primate chair at a thermoneutral temperature (25 degrees C) for 1 h (control) followed by cold exposure (12 degrees C) for 3 h or placed in a circulating water bath (28 degrees C) to induce a decrease in core temperature (Tre) to 35 and 33 degrees C. Plasma catecholamines were analyzed by high-pressure liquid chromatography with electrochemical detection (60–65% recovery, coefficient of variation = 15%). The 3-h cold exposure was associated with a 175% increase above control levels of norepinephrine (NE) and a 100% increase in epinephrine (E). Decreases were evident in Tre (0.5 degree C), mean skin temperature (Tsk, 5.5 degrees C), and mean body temperature (Tb, 2.0 degrees C). Continuous infusion of ketamine (0.65 mg . kg-1 . min-1) resulted in no change in the plasma levels of NE and E from the control levels. Tre, Tsk, and Tb all showed greater declines with the addition of ketamine infusion to the cold exposure. Water exposure (28 degrees C) under ketamine anesthesia resulted in a drop in Tre to 33 degrees C within 1 h. Plasma levels of NE and E were unchanged from control values at Tre of 35 and 33 degrees C. The data suggest that the administration of ketamine abolished both the thermoregulatory response and the catecholamine response to acute cold exposure.
Effect of inflation on trachealis muscle tone in canine tracheal segments in vitro
Authors: Gunst S. J. , Lai-Fook S. J.
Published: December 2017

Isolated tracheal segments were studied in vitro to determine how inflation affects the length and tension of the contracted and relaxed trachealis muscle. Circumferential trachealis muscle lengths were measured from cross-sectional radiographs taken during stepwise inflation of intact 20-cm-long tracheal segments to an inflation pressure of 25 cmH2O. A tracheal length spanning two cartilage rings was then cut out and mounted in a tissue bath using clips attached at the points of muscle insertion into the cartilage. The ring was stretched open along the axis of the muscle, and the resulting forces of the relaxed and contracted muscle and the cartilage were measured. Muscle lengths and tensions during inflation of the trachea were determined by comparing pressure vs. length and force vs. length measurements. During inflation from 0 to 25 cmH2O, the circumferential length of the trachealis muscle contracted with 10(-5) M acetylcholine increased from 48 to 70% of its length of maximal active tension (Lmax), while the relaxed muscle increased from 80 to 93% Lmax. The length of the contracted muscle was maintained at a nearly constant proportion of its relaxed length at each pressure.
Expiratory motor responses in the suckling opossum
Authors: Farber J. P.
Published: December 2017

To evaluate developmental aspects of expiratory muscle utilization, ventilation and electromyographic (EMG) activity from abdominal muscles were measured in unanesthetized suckling opossums. From about 20–35 days of age, breathing against a continuous positive airway pressure (CPAP) or inhalation of hypercapnic and asphyxiant test gases (ventilatory chemostimulation) increased or initiated a sustained expiratory-phased abdominal EMG discharge. Using younger animals, such responses could not be demonstrated during test manipulations, or pattern of activation was not typical of that observed in the older group. In another series of experiments, vagal mechanisms underlying expiratory abdominal muscle responses were evaluated by using lightly anesthetized animals. Unilateral vagotomy reduced abdominal EMG levels during ventilatory chemostimulation while minimally affecting breathing pattern; in addition, abdominal muscle activity during CPAP was of slower onset than before vagotomy. Slow onset of abdominal muscle activity was also seen in relatively young intact unanesthetized animals during responses to CPAP. Thus vagal afferents mediate expiratory motor responses during chemostimulation of breathing and may account, in part, for maturation of expiratory responses to CPAP.
Ventilatory changes associated with changes in pulmonary blood flow in dogs
Authors: Green J. F. , Sheldon M. I.
Published: December 2017

To examine the influence of pulmonary blood flow (Qp) on spontaneous ventilation (VE), we isolated the systemic and pulmonary circulations and controlled the arterial blood gases and blood flow (Q) in each circuit as we measured VE. Each dog was anesthetized with ketamine and maintained with halothane. Systemic Q was drained from the right atrium and pumped through an oxygenator and heat exchanger and returned to the aorta. An identical bypass was established for the pulmonary circulation, draining blood from the left atrium and pumping it to the pulmonary artery. The heart was fibrillated, all cannulas were brought through the chest wall, and the median sternotomy was closed. The dog was then allowed to breathe spontaneously. The arterial O2 partial pressure (PO2) of both circuits was maintained greater than 300 Torr. Systemic Q was maintained at 0.080 l X min-1 X kg-1. Initially the arterial CO2 partial pressure (PCO2) of both circuits was set at 40 Torr as Qp was varied randomly between approximately 0.025 and 0.175 l X min-1 X kg-1. The average VE-Qp relationship was linear with a slope of 1.45 (P less than 0.0005). Increasing the arterial PCO2 of both circuits to 60 Torr elevated VE an average of 0.37 l X min-1 X kg-1 at each level of Qp (P less than 0.0005). Vagotomy abolished the effect of Qp on VE. Increasing Qp affected the systemic arterial PCO2-VE response curve by shifting it upward without altering its slope. These results demonstrate that increases in Qp are associated with increases in VE. This phenomenon may contribute to exercise hyperpnea.
Carotid chemoreceptor regulation of expiratory duration
Authors: Bowes G. , Andrey S. M. , Kozar L. F. , Phillipson E. A.
Published: December 2017

We studied the effect of an experimentally augmented breath on the duration of expiration (TE) to test the hypothesis that within-breath reductions in alveolar partial pressure of CO2 (PACO2) delay the onset of the subsequent inspiration through a carotid chemoreceptor mechanism. Studies were performed in five carotid body intact (CBI) and three carotid body denervated (CBD) dogs during quiet wakefulness and nonrapid-eye-movement sleep. The vagus nerves were blocked in order to abolish vagal mechanisms capable of modulating TE. In CBI dogs, mechanically augmented breaths [mean tidal volume (VT), 149% of control] induced a mean decrease in PACO2 of 3.3 Torr and prolonged TE by 2.21 s to 127% of control (P less than 0.001). In contrast, in CBD dogs augmented breaths of comparable magnitude failed to change TE. Spontaneous sighs in fully intact dogs (mean VT, 369% of control) produced marked prolongation of TE (to 429% of control). In CBI dogs, there was a direct relationship between VT and the resulting TE across all experimental conditions (control, vagal blockade, augmented breaths, spontaneous sighs), whereas in CBD dogs, changes in VT failed to alter TE. The results indicate that the carotid bodies are able to induce within-breath alterations in TE and that such a mechanism can account for the prolongation of TE by vagal blockade and by spontaneous sighs.
Influence of increased alveolar PCO2 on thoracic gas volume measurements
Authors: Peslin R. , Jardin P. , Bohadana A. B.
Published: December 2017

We examined the possibility that cyclic gas exchange between alveolar space and the surrounding tissue, induced by alveolar pressure variations, could interfere with plethysmographic measurements of thoracic gas volume (TGV). A model study suggested that TGV could be overestimated by up to 100 ml and that the phenomenon could account for some of its previously reported negative frequency dependence (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 52: 739–747, 1982). As the error would be mainly due to CO2 exchange and be proportional to its partial pressure (PCO2), we studied in nine normal subjects the influence of increasing alveolar PCO2 from 30 to 50 Torr on TGV measurements at panting frequencies (f) of 0.5 and 22.5 Hz. Contrary to model predictions, CO2 tended to decrease TGV estimates at low frequency and to increase them at high frequency. As a consequence, frequency dependence of TGV (delta TGV/delta f) was less at high than at low PCO2 (-39 +/- 32 vs. -84 +/- 49 ml x Hz-1, P less than 0.001). The data are not satisfactorily explained but suggest that gas exchange is not an important factor in TGV measurements.
Force and duration of muscle twitch contractions in humans at pressures up to 70 bar
Authors: Harris D. J. , Bennett P. B.
Published: December 2017

The contraction peak force (CPF) and contraction time (CT) of the soleus Hoffmann (H) reflex and motor (M) response muscle twitch were measured in three subjects during the 686-m seawater Atlantis III simulated dive at Duke University. The mean CPF of both H and M twitches was observed to be 40–60% larger during compression than in predive control studies (P less than 0.001 for M response). This effect was sustained during the first 300 m of decompression, while postdive values were normal. Rate of contraction, as measured by changes in CT, was slowed significantly but only during compression (by 23% in the H reflex at 66.4 bar, P less than 0.001). These marked effects in CPF and CT cannot be explained by the small increases observed in the muscle action potential latency and duration, or other neuronal mechanisms. It is concluded that the twitch contraction of skeletal muscle is significantly slowed and augmented at pressure due to changes in excitation-contraction coupling or in the contractile process itself. These findings may be of importance in interpreting the etiology of many neuromuscular signs of the high-pressure neurological syndrome.
Comparative aspects of the dynamics of breathing in newborn mammals
Authors: Mortola J. P.
Published: December 2017

Static and dynamic properties of the respiratory system have been studied in anesthetized, tracheostomized newborns of six species, ranging in size from rats to piglets. Respiratory system compliance (Crs), total resistance of respiratory system (Rrs), and expiratory time constant (tau) have been measured in the paralyzed passively ventilated animals. Crs is found to be proportional to body weight (BW0.80) and Rrs to BW-0.75; tau is independent of body size, the shortest value being in kittens and guinea pigs and a value of about 0.14 s in the other species. Including the upper airway resistance, tau becomes approximately 0.22 s. This value is similar to the expiratory time of the fastest breathing species; therefore in the smallest species the high breathing rate can be regarded as a mechanism to raise end-expiratory level. On a few occasions, dynamic lung compliance and pulmonary resistance, measured in spontaneously breathing kittens, puppies, and piglets were, respectively, smaller and larger than Crs and Rrs, suggesting that the hysteresis of the pressure-volume curve may be substantial. Rrs was almost linear within the volume and flow range investigated, with the Rohrer's constant K2 always being less than 2.5% of K1. The Reynolds number increases with body size (alpha BW0.51) more than is predictable from the changes in tracheal diameter, since the tracheal flow velocity is not an interspecific constant.
Effect of hindlimb immobilization on the fatigability of skeletal muscle
Authors: Witzmann F. A. , Kim D. H. , Fitts R. H.
Published: December 2017

The soleus (SOL) and extensor digitorum longus (EDL) muscles of the rat were studied in situ (33.5 degrees C) after 6 wk of disuse atrophy produced by hindlimb immobilization (IM). IM resulted in depressed peak twitch (Pt) and tetanic (Po) tension as well as a decreased rate of tension development (+dP/dt) and decline (-dP/dt) in the slow-twitch SOL. The fast-twitch EDL was affected to a lesser extent, because only Po (g . cm-2) and Po,-dP/dt (g . cm-2 . ms-1) were depressed after IM. Twitch duration, as measured by contraction time and one-half relaxation time, was shortened in the SOL and prolonged in the EDL. In both the fast and slow muscles 30 min of electrical stimulation resulted in a significant decline in Po. Relative to the prefatigued Po, the atrophied and control muscles showed a similar fatigue pattern. This occurred in spite of lower ATP and glycogen concentrations and higher lactate levels in the atrophied muscles. Our results indicate significant impairment of contractile function following IM in fast and slow muscles with preferential alterations in the slow SOL. In addition, despite a lower resting capacity and an increased dependence on glycolysis, contractile properties of atrophied muscles differed little from control muscles in their pattern of response to 30 min of electrical stimulation.
Effect of extracellular calcium on superoxide release by rat alveolar macrophages
Authors: Forman H. J. , Nelson J.
Published: December 2017

Alveolar macrophages can be stimulated to release superoxide into the extracellular medium. The mechanism of activation of superoxide release has been reported to be mediated by the movement of Ca2+ into the cytosol, but the involvement of extracellular Ca2+ in this process has remained uncertain. Extracellular Ca2+ was not an absolute requirement for activation of superoxide release; however, 1.3 mM extracellular Ca2+ caused an approximate twofold enhancement of superoxide release stimulated by either concanavalin A or formyl-methionyl-leucyl-phenylalanine but had no effect on digitonin-stimulated superoxide release. Concanavalin A-stimulated superoxide was inhibited by the “Ca2+ entry blockers,” Mn2+ (1 microM) or methoxyverapamil (D-600) (100 microM). Inhibition by Mn2+ was competitive with extracellular Ca2+, whereas inhibition by D-600 was noncompetitive. Neither inhibitor, however, affected superoxide release after initiation. Thus activation of superoxide release by alveolar macrophages can be accomplished, in part, through the entrance of Ca2+ into the cell.
Dopamine, dobutamine, and phentolamine effects on pulmonary vascular mechanics
Authors: Graham R. , Skoog C. , Macedo W. , Carter J. , Oppenheimer L. , Rabson J. , Goldberg H. S.
Published: December 2017

The pressure-flow (P-Q) relationship of the pulmonary vasculature, in an isolated canine lobe perfused under classical zone II conditions, can be characterized by a rectilinear segment at high flow, a curvilinear segment at low flow, and a pulmonary arterial pressure (Ppa) that exceeds alveolar pressure at zero flow. This demonstrates the presence of critical closure in the pulmonary vascular bed. Effects of drugs on pulmonary vascular resistance (PVR) must take the normal P-Q relationship into account. We examined the effect of dopamine (D) and dobutamine (DB), alone and in combination with phentolamine (P), on the slope of the rectilinear segment of the P-Q curve (equivalent to vascular conductance), the extrapolated Ppa intercept (Ppai), and the Ppa at zero flow (Ppaz). Low-dose D (0.4–0.8 mg) and DB (1.0–5.0 mg) did not significantly alter any parameter from control. Higher-dose D (1.2–6.8 mg) and DB (13–38 mg) decreased vascular conductance 32.3 +/- 12.1 (SE) to 50.45 +/- 5.6% (P less than 0.05), and P alone increased conductance 12.0 +/- 2.6% (P less than 0.01) from control with no significant effect on Ppai or Ppaz. The change in conductance with D and DB alone was abolished when either drug was given in combination with P. Ppaz and Ppai decreased significantly from control with DB in combination with P when no significant effect on vascular conductance was noted. The results suggest that lung vessels determining changes in flow resistance are pharmacologically distinct from those subserving critical closure in the pulmonary vascular bed.
Molar absorptivities of human hemoglobin in the visible spectral range
Authors: Zijlstra W. G. , Buursma A. , Zwart A.
Published: December 2017

In a recent paper, Burkhard and Barnikol (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 52: 124–130, 1982) claimed that the absorption spectra of human (oxy-)hemoglobin are dependent on the total hemoglobin concentration (CHb) and it is suggested that this might also be the case with cyanmethemoglobin (HiCN). Such relationships would invalidate the widely used spectrophotometric methods for the determination of total hemoglobin and the fractions of various hemoglobin derivatives in human blood. Although Burkhard and Barnikol's findings are rather improbable considering earlier data, we measured the millimolar absorptivities of oxyhemoglobin (epsilon HbO2) and cyanmethemoglobin (epsilon HiCN) at various wavelengths over a wide range of concentrations (CHb approximately equal to 0.004–10 mmol x 1(-1)), using two different types of spectrophotometers. epsilon HbO2 and epsilon HiCN proved to be independent of CHb. Moreover the values obtained confirmed those in the earlier literature, whereas those of Burkhard and Barnikol are some 30% higher. Consequently there is no reason to doubt the validity of the generally accepted millimolar absorptivities of human hemoglobin.
Site of pulmonary hypoxic vasoconstriction studied with arterial and venous occlusion
Authors: Hakim T. S. , Michel R. P. , Minami H. , Chang H. K.
Published: December 2017

We applied the arterial and venous occlusion technique in an in situ, isolated left lower lobe preparation of a dog lung to compare the effects of hypoxia with the effects of airway pressure elevation, and the infusion of serotonin, norepinephrine, and histamine. The total arteriovenous pressure drop across the lobe was partitioned longitudinally into pressure drops across the relatively indistensible arteries (delta Pa) and veins (delta Pv) and across the middle distensible vessels (delta Pm). Hypoxia increased primarily delta Pm, as did elevation of airway pressure, whereas the vasoactive drugs increased either delta Pa or delta Pv. The increases in pulmonary arterial pressure (Pa) caused by hypoxia and by elevation of airway pressure were independent of blood flow rate, but increases in Pa induced by the vasoactive drugs were dependent on flow rate. We conclude that in the dog hypoxia acts primarily on small distensible vessels, whereas pulmonary vasoactive drugs constrict the relatively indistensible arteries and veins. It is possible that the increase in pulmonary vascular resistance during hypoxia did not involve smooth muscle contraction.
Hyperventilation in ponies at the onset of and during steady-state exercise
Authors: Pan L. G. , Forster H. V. , Bisgard G. E. , Kaminski R. P. , Dorsey S. M. , Busch M. A.
Published: December 2017

We studied blood gases in ponies to assess the relationship of alveolar ventilation (VA) to pulmonary CO2 delivery during moderate treadmill exercise. In normal ponies for 1.8, 3, or 6 mph, respectively, partial pressure of CO2 in arterial blood (PaCO2) decreased maximally by 3.1, 4.4, and 5.7 Torr at 30–90 s of exercise and remained below rest by 1.4, 2.3, and 4.5 Torr during steady-state (4–8 min) exercise (P less than 0.01). Partial pressure of O2 in arterial blood (PaO2) and arterial pH, (pHa) also reflected hyperventilation. Mixed venus CO2 partial pressure (PVCO2) decreased 2.3 and 2.9 Torr by 30 s for 3 and 6 mph, respectively (P less than 0.05). In work transitions either from 1.8 to 6 mph or from 6 mph to 1.8 mph, respectively, PaCO2 either decreased 3.8 Torr or increased 3.3 Torr by 45 s of the second work load (P less than 0.01). During exercise in acute (2–4 wk) carotid body denervated (CBD) ponies at 1.8, 3, or 6 mph, respectively, PaCO2 decreased maximally below rest by 9.0, 7.6, and 13.2 Torr at 30–45 s of exercise and remained below rest by 1.3, 2.3, and 7.8 Torr during steady-state (4–8 min) exercise (P less than 0.1). In the chronic (1–2 yr) CBD ponies, the hypocapnia was generally greater than normal but less than in the acute CBD ponies. We conclude that in the pony 1) VA is not tightly matched to pulmonary CO2 delivery during exercise, particularly during transitional states, 2) the exercise hyperpnea is not mediated by PaCO2 or PVCO2, and 3) during transitional states in the normal pony, the carotid bodies attenuate VA drive thereby reducing arterial hypocapnia.
Preparation of a jugular vein cannula: use with a semiautomatic blood-sampling system
Authors: Tinsley F. C. , Short W. G. , Powell J. G. , Shaar C. J.
Published: December 2017

A method for preparation and surgical implantation of a rodent jugular vein cannula and construction and use of an automatic blood-sampling system are described. The cannula permits repeated blood sampling without disturbing the rat. The semiautomatic sampling system permits one individual to collect blood samples from three rats simultaneously.
Cardiac output measurement using N2O uptake: a method to subtract cardiogenic oscillations
Authors: Dawson W. T. , Johnson R. L.
Published: December 2017

Plethysmographic (box) methods using N2O uptake to measure pulmonary capillary blood flow, right ventricular stroke volume, and pulmonary arterial flow pulse conduction time have been complicated by the presence of so-called “cardiogenic oscillations” in the box flow records on air and N2O breathing. The exact cause of these oscillations is unknown but believed to be secondary to instantaneous changes in net blood flow into and out of the thorax during the cardiac cycle. We examined these oscillations and pulmonary capillary blood flow in normal human subjects in a flow plethysmograph using a pressure compensation circuit to extend the frequency response. The cardiogenic oscillations in flow recorded at the mouth (with glottis open) are much greater in amplitude and 90 degrees out of phase from those recorded from the plethysmograph. We derived a theoretical analysis of this and designed an analogue electrical circuit to enable us to eliminate these oscillations by electrical subtraction from the box flow record generated by N2O uptake in the pulmonary capillary bed. Measurements of pulmonary capillary blood flow and ventricular stroke volume using our method correlate with measurements made with acetylene-rebreathing blood flow measurements performed sequentially at the same sitting.
Nonuniform lung deformations
Authors: Wilson T. A.
Published: December 2017

This review evaluates the progress that has been made in describing the lung as a deformable solid and in using the methods of solid mechanics to answer questions about nonuniform lung deformations and parenchymal interdependence. The interdependence effect on the large intrapulmonary vessels has been successfully analyzed by these methods, but the modeling and analysis of the effects of gravity and chest wall shape on lung expansion are far from complete.
Sympathetic and parasympathetic nervous control of airway resistance in dog lungs
Authors: Inoue H. , Ishii M. , Fuyuki T. , Inoue C. , Matsumoto N. , Sasaki H. , Takishima T.
Published: December 2017

We studied autonomic nervous control of central (Rc), peripheral (Rp), and extremely peripheral (Rep) airway resistances using a combination of a retrograde catheter method and a pleural capsule method. Airflow through the pleural capsule enabled us to measure Rep, which mainly reflected the resistance of local bronchioles less than 0.6 mm in diameter. Rp of the airways less than about 2 mm in diameter was not negligibly small at any lung volume (VL). With vagi intact, Rc increased at high as well as low VL, whereas Rp and Rep increased sharply as VL decreased. Vagal stimulation increased Rp more markedly than Rc, and Rep least of all. Propranolol augmented total airway resistance (Rtot) two to four times as much as vagal stimulation, mainly because of increased Rp. Stimulation of stellate ganglia inhibited up to half the increase of Rtot elicited by vagal stimulation; most of the inhibition occurred in Rp, but little in Rc and Rep. Our data suggest that both sympathetic and parasympathetic control is more extensive for Rp than for Rc or Rep.
Patency and compliance of pulmonary veins when airway pressure exceeds blood pressure
Authors: Fung Y. C. , Sobin S. S. , Tremer H. , Yen M. R. , Ho H. H.
Published: December 2017

Our measurements on cat's lung show that pulmonary veins and venules are not collapsible, but remain open when the alveolar gas pressure (PA) exceeds the local blood pressure (Pv). Their compliance constants show no discontinuity as Pv falls below PA. The capillaries, however, do collapse when PA greater than Pv. The explanation of the patency of the veins when PA greater than Pv is the pulling on the blood vessels by tension in the interalveolar septa. Photomicrographs show that each venule (or vein) is pulled radially by three or more interalveolar septa. Capillary sheets, however, are exposed to gas on the lateral sides and can readily collapse when PA greater than Pv. These facts provide the key to the analysis of pulmonary blood flow in zone 2. The “sluicing” gate, i.e., the site of flow limitation, must be located at the junctions of capillary sheets and the first generation of venules. Further, data on the branching pattern and compliance of small pulmonary veins, which are needed in quantitative analysis of pulmonary circulation, are presented.
Augmentation of alpha-adrenergic contractions in the trachealis muscle of living dogs
Authors: Brown J. K. , Shields R. , Jones C. , Gold W. M.
Published: December 2017

Discrepancies exist between reported effects of histamine on the alpha-adrenergic responsiveness of the canine trachealis muscle. Therefore, using an in situ preparation described recently (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 49: 84–94, 1980), we tested the effects of histamine and other agents on alpha-adrenergic responses in the trachealis muscle of 34 anesthetized dogs. Under basal conditions, maximum alpha-adrenergic responses were small [3 +/- 1 (SE) g/cm] compared with those induced by a supramaximal parasympathetic stimulus (45 +/- 3 g/cm). After exposure of the muscle to histamine, responsiveness increased markedly to alpha-adrenergic stimuli, which included tracheal arterial injections of norepinephrine and phenylephrine or electrical stimulation of sympathetic nerves. Augmented alpha-adrenergic responsiveness persisted for 20 min after the end of contractions induced by histamine. Serotonin and long-acting, but not short-acting, cholinergic agonists also potentiated alpha-adrenergic responsiveness. We concluded that exposure of the trachealis muscle in living dogs to a variety of constrictor stimuli potently augmented its alpha-adrenergic responsiveness.
Intercompartmental fluid shifts after dextran infusion in rabbits
Authors: Mohsenin V. , DuBois A. B.
Published: December 2017

Intercompartmental fluid shifts were studied in New Zealand White rabbits after infusion of hyperoncotic dextran solution with a mean molecular weight of 64,200 and osmolality of 220 mosmol/kg H2O. In comparison with the control period, it was found that 1) plasma volume increased by a net volume of 83 +/- 12 ml; 2) systemic blood pressure increased slightly but significantly and central venous pressure increased markedly (this was accompanied by a reduction of interstitial fluid pressure from a control of -1 to -8 cmH2O after dextran); 3) plasma volume expansion was not accompanied by plasma sodium and chloride dilution when they were expressed in meq/kg of plasma water; and 4) plasma osmolality did not change after dextran infusions. The increase in plasma volume unaccompanied by any change in plasma sodium, chloride, or osmolality may be explained by a transcapillary fluid shift from the interstitial space to the bloodstream caused by an increase in plasma oncotic pressure. Because the more negative interstitial fluid pressure did not seem to attract any appreciable amount of fluid from the cells, we concluded that the interstitial space did not hydrodynamically couple the intravascular space to the cellular compartment.
Hypoxic constriction of alveolar and extra-alveolar vessels in isolated pig lungs
Authors: Sylvester J. T. , Mitzner W. , Ngeow Y. , Permutt S.
Published: December 2017

To examine whether hypoxia causes constriction of alveolar or extra-alveolar vessels, we determined the relationships among transpulmonary pressure, pulmonary arterial pressure (Ppa), blood flow (Q), and transvascular fluid filtration rate (W) during normoxia (PO2 = 200 Torr) and hypoxia (PO2 = 50 Torr) in isolated pig lungs perfused with autologous blood. Left atrial pressures were always subatmospheric. The effects of lung inflation and hypoxic vasoconstriction on the Ppa-Q relationship were similar; when transpulmonary pressure was greater than 5 Torr, both shifted the curve to higher pressures in a parallel fashion. When transpulmonary pressure was 0–5 Torr, however, inflation had no effect on the Ppa-Q relationship during either normoxia or hypoxia. During normoxia at a transpulmonary pressure of 3.5 Torr, the relationship between fluid filtration rate and flow was characterized by a W of zero at Q less than 1.5 l/min and a rapid increase in W with Q above this value. Both hypoxia and inflation shifted this relationship to higher filtration rates in a parallel fashion. Furthermore, the combined effects of hypoxia and inflation on filtration rate were additive. These results suggest that hypoxia caused constriction of both alveolar and extra-alveolar vessels, resulting in increased intraluminal pressure and filtration of fluid in vessels upstream from the sites of constriction.
Time course of deacclimatization to cold water immersion in Korean women divers
Authors: Park Y. S. , Rennie D. W. , Lee I. S. , Park Y. D. , Paik K. S. , Kang D. H. , Suh D. J. , Lee S. H. , Hong S. Y. , Hong S. K.
Published: December 2017

Seasonal basal metabolic rates (BMR), critical water temperature (Tcw), maximal body insulations (Imax), and finger blood flow during hand immersion in 6 degrees C water (Q finger) were measured periodically during the course of a 3-yr longitudinal study (1980–1982) of modern Korean diving women (ama), who have been wearing wet suits since 1977 to avoid cold stress during work. Methods and protocols were identical to previous studies of cotton-suited ama from 1961–1974. The BMR of modern ama did not undergo seasonal fluctuation (1980–1981) and was within the DuBois standard and comparable to nondivers year around Tcw of ama was still reduced by 2–3 degrees C in 1980 but increased progressively to equal that of nondivers in 1982, when compared at comparable subcutaneous fat thickness (SFT). Since modern ama and nondivers have 2.4 times thicker SFT (i.e., 4–13 mm) than in 1962 the absolute Tcw is significantly reduced. Q finger of ama was also significantly lower than controls in 1980 but in 1981–1982 was identical to controls. Imax of modern ama was identical to controls of comparable SFT in 1980–1982. The time course of cold deacclimatization thus was BMR, 3 yr; Imax, 3 yr; Q finger, 4 yr; and Tcw, 5 yr. This longitudinal study provides further evidence that acclimatization to cold did at one time exist in these diving women.
Expiratory and arterial partial pressure relations under different ventilation-perfusion conditions
Authors: Zwart A. , Luijendijk S. C. , de Vries W. R.
Published: December 2017

Inert tracer gas exchange across the human respiratory system is simulated in an asymmetric lung model for different oscillatory breathing patterns. The momentary volume-averaged alveolar partial pressure (PA), the expiratory partial pressure (PE), the mixed expiratory partial pressure (PE), the end-tidal partial pressure (PET), and the mean arterial partial pressure (Pa), are calculated as functions of the blood-gas partition coefficient (lambda) and the diffusion coefficient (D) of the tracer gas. The lambda values vary from 0.01 to 330.0 inclusive, and four values of D are used (0.5, 0.22, 0.1, and 0.01). Three ventilation-perfusion conditions corresponding to rest and mild and moderate exercise are simulated. Under simulated exercise conditions, we compute a reversed difference between PET and Pa compared with the rest condition. This reversal is directly reflected in the relation between the physiological dead space fraction (1--PE/Pa) and the Bohr dead space fraction (1--PE/PET). It is argued that the difference (PET--Pa) depends on the lambda of the tracer gas, the buffering capacity of lung tissue, and the stratification caused by diffusion-limited gas transport in the gas phase. Finally some determinants for the reversed difference (PET--Pa) and the significance for conventional gas analysis are discussed.
Effects of hyperbaric oxygen exposure at 31.3 ATA on spontaneously beating cat hearts
Authors: Doubt T. J. , Evans D. E.
Published: December 2017

Cardiovascular responses to raised ambient pressure and acute hyperbaric oxygen (HBO) exposure [HBO, partial pressure of oxygen (PO2) = 2 ATA)] were examined in anesthetized cats. Relatively normoxic [PO2 = 0.35 ATA] helium compression to 31.3 ATA decreased spontaneous heart rate, prolonged the P-R and Q-T intervals of the ECG independently of changes in rate, and significantly increased ventricular contractility. HBO while at depth produced further decreases in heart rate, with no change in the P-R interval. The Q-T interval decreased significantly in the presence of bradycardia, particularly during the first 15 min of exposure. During the first 10-15 min of HBO exposure myocardial contractility and developed ventricular pressure were reduced, but contractility increased significantly at 30 min. These results indicate that HBO interacts with depth effects to produce hyperbaric bradycardia but reverses pressure actions on ventricular repolarization. The inotropic effects of HBO are time dependent, with slightly negative effects occurring initially, followed by positive inotropic actions at 30 min.
Deposition of aerosol particles and flow resistance in mathematical and experimental airway models
Authors: Kim C. S. , Brown L. K. , Lewars G. G. , Sackner M. A.
Published: December 2017

Aerosol deposition and flow resistance in obstructed airways were determined from five mathematical and experimental airway models. The first three models were theoretical and based upon Weibel's symmetrical lung model with 1) uniform reduction of airway diameter in various groups of airway generations; 2) obstruction of a few major airways such that a severe uneven flow distribution occurs in the lung; 3) focal constriction of selected large airways. In model 3, an empirical formula was utilized to assess deposition and resistance in the constricted airways. The remaining two models were tested experimentally; 4) oscillation of a compliant wall in a straight tube and 5) two-phase gas-liquid flow utilizing human sputum in a rigid branching tube. In models 1, 2, and 3, airway resistance increased to a greater extent than did the increase of aerosol deposition except when small airways were obstructed in model 1. Here, the increase of aerosol deposition was slightly higher than the rise in airway resistance. A sharp increase of aerosol deposition with a minimal increase of flow resistance was demonstrated in models 4 and 5. These data indicate that aerosol deposition may be a more sensitive indicator of airway abnormalities than overall airway resistance in small airways obstruction, during oscillation of large and medium airway walls, and when excessive secretions within the airways move with a wave or slug motion.