bluuebunny/crossref_metadata_2025 huggingface dataset:
Ventilation by high-frequency oscillation
Authors: Bohn D. J. , Miyasaka K. , Marchak B. E. , Thompson W. K. , Froese A. B. , Bryan A. C.
Published: December 2017

The effect of applying a high-frequency small-volume sinusoidal oscillation at the airway was investigated in anesthetized apneic beagle dogs (mean wt 11 kg, mean VDphys 6.6 +/- 0.6 ml/kg). Oscillations generated by a piston in a cylinder were transmitter to the lungs through an uncuffed endotracheal tube (4.5 mm ID, 6.0 mm OD), which allowed a substantial leak back through the vocal cords. A bias flow of fresh gas presented inspired air to the midtracheal level. The minimum distal airway pressure (measured at the end of the endotracheal tube) was maintained between 0 and 2 cmH2O. Peak airway pressures were 4-8 cmH2O. The optimal frequency for CO2 elimination was 15 Hz. Using volumes of 1.9 ml/kg (range 1.7-2.3) at this frequency the mean PaCO2 was 33.1 +/- 0.5 Torr. In four dogs breathing 100% O2 the PaO2 was 594 +/- 9 Torr during spontaneous ventilation and 580 +/- 9 Torr after 5 h of uninterrupted oscillation. In four experiments using room air the PaO2 was 95 +/- 5 Torr during spontaneous respiration and 106 +/- 1 Torr after 5 h of oscillation. In an additional seven studies there was no difference in mean cardiac output between oscillation and conventional mechanical ventilation. This study demonstrates that high-frequency small-volume oscillations can maintain gas exchange for many hours presumably by markedly enhancing the diffusivity of gases in the lung.
Use of magnetometers to volume-reference flow-volume curves
Authors: Goldstein D. , Mead J.
Published: December 2017

Chest wall diameters measured by magnetometers were used to indicate a lung volume reference for repeated interrupted partial flow-volume curves (IPFVC's) and IPFVC's, and total respiratory conductances were measured before and after bronchodilation in normals. With posture rigidly controlled, subjects matched the magnetometer display on an X-Y oscilloscope to a previously marked point on the screen. Seven subjects performed six inspiratory capacities (IC's) from the reference point, completely reposturing before each maneuver. For a mean IC of 2.25 liters the standard deviation was 5.5%. IPFVC's were performed through a valve system triggering open at 60 cmH2O and shutting after 1 liter of expiration. Ten subjects each performed five sets of IPFVC's volume-referenced by magnetometers and the pooled flow variability was 5% or 0.15 l/s. Respiratory conductances by forced oscillations and IPFVC's were measured in five normal subjects before and after inhaled isoproterenol. In each subject the flow increase was always greater than the conductance increase (about 2.5:1.0) for P less than 0.05. We conclude that magnetometers may be used in normals to volume-reference IPFVC's with excellent reproducibility.
Pulmonary tissue volume in isolated perfused dog lungs
Authors: Crapo R. O. , Crapo J. D. , Morris A. H. , Berlin S. L. , Devries W. C.
Published: December 2017

Lung tissue volume (Vt) and pulmonary capillary blood flow (Qc) were measured with an acetylene rebreathing technique in intact and isolated perfused dog lungs. Qc (1.73 ± 0.17 l/min) was consistently greater than pump flow (0.87 ± 0.10 l/min) in isolated perfused lungs because acetylene disappearance from the lung was increased by diffusion across the pleura into the room. In spite of the increased acetylene loss, Vt can be measured in isolated lungs with reproducibility similar to that in intact animals (Vt intact = 207 ± 63 ml, Vt isolated perfused = 208 ± 61 ml).
Effects of urinary bladder afferents on respiration
Authors: Schondorf R. , Polosa C.
Published: December 2017

The electrical activity of phrenic and recurrent laryngeal motoneurons was recorded during activation of urinary bladder afferents in pentobarbital-anesthetized, paralyzed, artificially ventilated cats. Distension or spontaneous neurogenic contraction of the bladder decreased the amplitude and frequency (bursts/min) of the burst activity in these two nerves. The decrease in frequency was due mainly to a prolongation of the interburst interval (duration of expiration). Similar effects were observed during low-frequency electrical stimulation of pelvic nerve afferents with conduction velocities in the A gamma-A delta range. High-frequency stimulation of pelvic nerve afferents increased the amplitude of the burst activity in these two nerves. These results suggest an action of bladder afferents on the brain stem oscillator controlling respiratory frequency and drive. Some of the excitatory and inhibitory effects of bladder afferents on phrenic motoneurons may be mediated through spinal circuits.
Stroke volume during recovery from upright bicycle exercise
Authors: Goldberg D. I. , Shephard R. J.
Published: December 2017

A CO2 rebreathing method has been modified to allow nonsteady-state measurements of cardiac output during and after recovery from upright bicycle ergometer exercise. Data obtained on 10 healthy men who continued loadless pedaling for 4 min following a progressive exercise bout to 70% of maximum oxygen intake showed a rapid recovery of heart rate. In contrast, there was an early 29% increase of stroke volume and 216 s after exercise the stroke volume was still larger than the final exercise reading. It appears that if venous return is facilitated, the metabolic needs of recovery plus the small cost of loadless pedaling are met by maintaining stroke volume rather than heart rate.
Ventilatory responses of newborn calves to progressive hypoxia in quiet and active sleep
Authors: Jeffery H. E. , Read D. J.
Published: December 2017

Isocapnic progressive hypoxia was produced by rebreathing 8-10% oxygen in replicate tests during quiet and active sleep, in five full-term calves aged 1-8 days. Airflow through a tightly fitting mask was digitized at 50-ms intervals to calculate breath-by-breath ventilation and rate. Using a cuvette oximeter, arterial O2 saturation (SaO2) was recorded continuously. A mass-spectrometer record of end-tidal PO2 and PCO2 confirmed the mask seal and the constancy of PCO2. Sleep state was characterized by EEG, EOG, neck EMG, and behavior. In quiet sleep the ratio of ventilation to its normoxic control (VR) increased linearly as SaO2 fell; reflex arousal occurred at SaO2 84.9 ± 4.3% (SD) with VR 1.4 ± 0.39 (SD). In contrast, during active sleep, hypoxemia progressed without any ventilatory response to a very low SaO2; a reflex arousal occurred at SaO2 59.2 ±11.0%, often with a ventilatory response developing abruptly just prior to arousal. The slope of the VR/SaO2 regression lines for the overlapping range of SaO2 differed significantly with state in each animal (P < 0.001); the pooled VR values at SaO2 75% were 1.73± 0.15 (SD) and 0.91 ± 0.18 for quiet and active sleep respectively. The depression of the ventilatory response to hypoxia in active sleep differs from previous reports on adult dogs. The basis for this difference needs to be evaluated in relation to species and age, in particular in relation to both the mechanics of breathing and to chemoreceptor reflexes.
Comparison of direct and acoustical area measurements in physical models of human central airways
Authors: Jackson A. C. , Olson D. E.
Published: December 2017

Total cross-sectional areas were computed from direct measurements made on two human central airway casts. Acoustic pulse-response measurements were obtained on rigid-walled positive replicas of these casts. From the acoustic response data of each cast, we computed the area-distance function of the acoustically equivalent structure (i.e., the structure with regular branching and negligible viscous losses, but with similar acoustic properties). The acoustic data predicted equivalent areas that compared favorably to the total cross-sectional areas in the casts at all points from the beginning of the trachea to distances about 6 cm beyond the carina corresponding to airways of the third, fourth, or fifth generation. These results indicate that, at least in the central airways, branching asymmetry and internal energy losses introduced negligible errors in estimates of cross-sectional areas derived from acoustic pulse-response measurements. This rapid noninvasive technique thus shows promise as a method of detecting upper and central airway obstruction.
Solubility of acetylene in human blood determined by mass spectrometry
Authors: Meyer M. , Scheid P.
Published: December 2017

To measure the acetylene solubility (alpha C2H2) in human blood, a blood sample, which had been equilibrated with a gas mixture containing C2H2, was injected into an airtight acetylene-free vessel, and the gas partial pressure was measured by mass spectrometry after reequilibration. The system was calibrated by injecting into the vessel a known volume of the equilibrating gas mixture. At 37 degrees C, alpha C2H2 averaged 0.768 ± 0.004 (SD) ml STPD.ml blood-1.atm-1, which is only slightly above the data from the literature.
Delineating acute neuroendocrine responses in microwave-exposed rats
Authors: Lu S. T. , Lebda N. , Pettit S. , Michaelson S. M.
Published: December 2017

One hundred and eighteen male rats (Long-Evans) were acclimated to experimental procedures (i.e., handling, transferring from and back to "home" cage, body weight and colonic temperature determinations) for 2 wk and then subjected to cage confinement for 3 days before microwave (MW) exposure to 2,450 MHz for 1-, h, at 1-70 mW.cm-2 or sham exposure at ambient temperature of 24 +/- 1 degree C. Colonic temperature increased after exposure to power densities greater than or equal to 20 mW.cm-2 and was the most sensitive parameter measured. Inverse relationships between corticosterone and thyrotropin or growth hormone were noted after exposure for 1 h at 50 mW.cm-2 and above. Pituitary-thyroid function was inhibited after exposure to 20 mW.cm-2 for 2-8 h. Changes in other hormones were transient or inconsistent. Corticosterone, thyrotropin, and growth hormone levels could be correlated with power density or colonic temperature in rats exposed to MW for 1 h; corticosterone and thyrotropin levles correlated with colonic temperatures in shams. Body temperature influences adenohypophysial hormones in studies of MW biological effects.
Pressure-volume behavior of perivascular interstitium measured in isolated dog lung
Authors: Lai-Fook S. J. , Toporoff B.
Published: December 2017

Pulmonary perivascular interstitial fluid pressure (Px) was measured as a function of extravascular water accumulation (W). Px was measured directly by wick catheters and open-ended needles inserted in the interstitium near the hilus of isolated perfused dog lobes. Lobes were studied at constant transpulmonary pressure (Ptp) and vascular pressure (Pv, arterial equal to venous pressure). Px-W behavior had two distinct phases: an initial low compliance phase interpreted as perivascular filling, followed sometimes by an abrupt transition to a high compliance phase interpreted as alveolar flooding. W at transition was between 20 and 50% of the initial lung weight. Perivascular compliance during filling at a Ptp of 6 cmH2O was 0.1 g.g wet lobe wt-1.cmH2O-1, which was one-sixth that during alveolar flooding and 2.5 times that at a Ptp of 25 cmH2O. At the start of alveolar flooding, estimated alveolar interstitial fluid pressure was slightly (2 cmH2O) below alveolar pressure (PAlv) at a Ptp of 6 cmH2O but considerably belov PAlv at high lung volumes. These findings support the concept that alveolar surface tension reduces the interstitial fluid pressure below PAlv.
Responses to continuous negative-pressure breathing in man at rest and during exercise
Authors: Bjurstedt H. , Rosenhamer G. , Hesser C. M. , Lindborg B.
Published: December 2017

We studied the respiratory and circulatory effects in six healthy supine volunteers of continuous negative-pressure breathing (CNPB) at -15 and -30 cmH2O at rest and during dynamic leg exercies at 50% of individual working capacity. CNPB had no significant effects on respiratory minute volume, tidal volume, or arterial carbon dioxide tension. Mean arterial pressure remained essentially unchanged both at rest and during exercise, signifying that the reductions in intrathoracic pressure caused corresponding increases in left ventricular afterload. Nevertheless, cardiac output increased significantly in both conditions, causing reductions of mean central venous pressure that were considerably greater during exercise than at rest. These responses were reflected by increments in left ventricular work, amounting to 24 and 20% at rest and during exercise, respectively, at -30 cmH2O. We conclude that in CNPB at rest the increased activity of the left ventricle with associated juxtathoracic venous collapse protects the right heart and pulmonary circulation from congestion and that it does so even more effectively during exercise.
Thermoregulation during rest and exercise in different postures in a hot humid environment
Authors: Kabayashi K. , Horvath S. M. , Diaz F. J. , Bransford D. R. , Drinkwater B. L.
Published: December 2017

The time course of whole-body sweating and thermal regulation during rest and exercise in a hot humid environment was investigated in three body postures. After 45 min rest in the upright, low-sit, or supine posture, five unacclimatized men exercised for 45 min on a bicycle ergometer in the same posture in an environment of 49.5 degrees C, 28.9 Torr. Exercise was performed at two different work loads, corresponding to about 30 and 45% of VO2max. During exercise auditory canal temperature, rectal temperature, and mean skin temperature increased linearly being highest in the supine and lowest in the upright posture. Percentage of evaporated sweat from the skin to secreted sweat was 65% in upright, 52% in the low-sit, and only 46% in the supine posture during the last 20 min of exercise regardless of work load. The time course of the rate of body heat storage was different from predictions based on the thermal balance equation. Evaporative heat loss was not 100% effective in cooling the skin surface.
Moderation of hypoxic vasoconstriction by infused arachidonic acid: role of PGI2
Authors: Gerber J. G. , Voelkel N. , Nies A. S. , McMurtry I. F. , Reeves J. T.
Published: December 2017

To determine the role of prostaglandins in modulating pulmonary circulatory responses, we examined the effect of the prostaglandin precursor, sodium arachidonate, on the pulmonary vascular resistance of mongrel dogs during alveolar hypoxia. When infused intravenously for 5 min during hypoxia, sodium arachidonate (1 mg/min) decreased pulmonary vascular resistance from 6.9 ± 1.1 to 4.9± 0.6 U (P less than 0.05). The vasodilation produced by sodium arachidonate was blocked by sodium meclofenamate, a cyclooxygenase inhibitor. By infusing radiolabeled sodium arachidonate and collecting aortic blood samples, we found from chromatographic and mass spectrometric analysis that a major prostaglandin produced was 6-keto-PGF1 alpha, the stable hydrolysis product of PGI2. Infusion of PGI2, but not PGE2, during hypoxia decreased pulmonary vascular resistance. We concluded that the prostaglandin precursor, sodium arachidonate, is a vasodilator of the pulmonary vasculature that has been constricted by alveolar hypoxia, probably because PGI2 is formed from the arachidonate. The pulmonary circulation may be similar to the systemic circulation where vasoconstriction results in the generation of vasodilatory prostaglandins that attenuate the constrictor effect.
Alteration in myocardial oxygen balance during exercise after beta-adrenergic blockade in dogs
Authors: Heyndrickx G. R. , Pannier J. L. , Muylaert P. , Mabilde C. , Leusen I.
Published: December 2017

The effects of beta-adrenergic blockade upon myocardial blood flow and oxygen balance during exercise were evaluated in eight conscious dogs, instrumented for chronic measurements of coronary blood flow, left ventricular pressure, aortic blood pressure, heart rate, and sampling of arterial and coronary sinus venous blood. The administration of propranolol (1.5 mg/kg iv) produced a decrease in heart rate, peak left ventricular (LV) dP/dt, LV (dP/dt/P, and an increase in LV end-diastolic pressure during exercise. Mean coronary blood flow and myocardial oxygen consumption were lower after propranolol than at the same exercise intensity in control conditions. The oxygen delivery-to-oxygen consumption ratio and the coronary sinus oxygen content were also significantly lower. It is concluded that the relationship between myocardial oxygen supply and demand is modified during exercise after propranolol, so that a given level of myocardial oxygen consumption is achieved with a proportionally lower myocardial blood flow and a higher oxygen extraction.
Adrenal component to pulmonary hypertension caused by nicotine administration in the dog
Authors: Maron M. B. , Rickaby D. A. , Dawson C. A.
Published: December 2017

In this study, we investigated the possibility that the adrenal gland contributes to nicotine-induced pulmonary hypertension using a canine left lower lung lobe (LLL) preparation that was pump-perfused with mixed venous blood at constant flow and outflow pressure. Main pulmonary artery, left atrial, and LLL arterial pressures were monitored to assess the responses of the animal's intact right lung and isolated LLL. With the adrenal venous return intact, injection of 10-26 micrograms/kg nicotine into the left ventricle or ascending aorta resulted in a 42% increase in LLL arterial pressure and a 70% increase in the pulmonary arterial-left atrial pressure gradient (Ppa-Pla). When the adrenal venous return was interrupted, the increases in LLL arterial pressure and Ppa-Pla were reduced to 6 and 10%, respectively. The LLL response could be eliminated by alpha-adrenergic receptor blockade, suggesting that adrenal catecholamines may contribute to the pulmonary hypertension induced by nicotine infusion.
Dynamic respiratory mechanics in intact anesthetized hamsters
Authors: Strope G. L. , Cox C. L. , Pimmel R. L. , Clyde W. A.
Published: December 2017

A system for measuring parameters of ventilation and respiratory mechanics in intact anesthetized hamsters was developed. Means ± SD of five weekly measurements in eight hamsters were 0.68 ± 0.09 ml for tidal volume, 45 ± 14 breaths.min-1 for respiratory frequency, 29.3 ± 10.4 ml.min-1 for minute ventilation, 0.301 ± 0.080 ml.cmH2O-1 for dynamic compliance, 0.435 ± 0.151 cmH2O.ml-1.s for inspiratory resistance, 0.311± 0.101 cmH2O.ml-1.s for expiratory resistance, and 0.334 ± 0.096 cmH2O.ml-1.s for average resistance. The standard deviations of five consecutive measurements of these parameters on the same day were typically 10% of the corresponding mean values suggesting that acute changes as small as 10% can be detected in a study of similar size. The corresponding value for five single measurements on different days at weekly intervals was 30%. We believe that this system yields reasonable and repeatable measurements, and, because it is atraumatic, it can be used in chronic studies of diseases in hamsters and other small animals.
Halothane anesthesia and respiratory mechanics in dogs lying supine
Authors: Southorn P. , Rehder K. , Hyatt R. E.
Published: December 2017

Functional residual capacity (FRC) and quasi-static deflation pressure-volume (PV) curves of the total respiratory system, lung, and chest wall were measured in eight trained dogs lying supine, first awake and then anesthetized with halothane. Two of the eight dogs were repetitively examined 10 times during a 15-mo period. FRC decreased with anesthesia in six of the eight dogs and incresed with anesthesia in the remaining two dogs. There was a significant mean anesthesia-induced reduction in FRC of 16.9% (P 〜 0.05). FRC change with anesthesia varied between studies in one of the two dogs repetitively examined. Mean PV curves of the total system, lung, and chest wall of the six dogs whose FRC decreased with anesthesia were shifted to the right by anesthesia. PV curves from the two dogs whose FRC increased with anesthesia were shifted to the left. Anesthesia produced a significant reduction (P 〜 0.05) in mean lung compliance and significant increases (P 〜0.05) in mean chest wall and total system compliances.
An electrocapillary flowmeter usable as a quantitative sweat detector
Authors: Alric R. , Quatrefages R. , Comallonga J.
Published: December 2017

A quantitative sweat detector was devised as part of a noninvasive portable warning apparatus intended for the surveillance of unstable insulin-treated diabetics who may have nocturnal hypoglycemic attacks. The sweat sensor consists of a pair of electrodes embedded in a porous material that is infiltrated under capillary drive by sweat as it oozes out of the skin. It was shown that the detector is almost insensitive to insensible perspiration but undergoes graded variation of impedance as it is filled with sweat. It thus works as a transducer of sweat flux (flow rate through unit skin area) as long as the porous material is not saturated. This device has already proved useful as a hypogycemic alarm and could certainly be used for the measurement of sweating rate in place of more cumbersome devices involving ventilated chambers.
Effects of apomorphine and pimozide on temperature regulation during exercise in the rat
Authors: Gisolfi C. V. , Mora F. , Bloomfield S. , Beattie M. , Magnes S.
Published: December 2017

The purpose of this study was to determine the effects of a specific dopamine receptor agonist (apomorphine) and antagonist (pimozide) on thermoregulation when the heat loss pathway was activated by the stress of exercise. Apomorphine or its control vehicle (0.9% wt/vol saline) was injected systemically (0.5, 1.0, 1.5 mg/kg ip) or within the preoptic-anterior hypothalamus (5, 10, 20 micrograms) immediately before the start of treadmill exercise at 21.5 m/min. Colonic, tailskin, and ambient temperatures were recorded each minute. Oxygen consumption was calculated from on-line measurements of percent O2 and CO2. Pimozide injected systemically (0.5 mg/kg ip) had no effect on resting colonic temperature, but caused a significant (P less than 0.05) hyperthermia during treadmill exercise compared to saline controls. Central and systemic injections of apomorphine caused a dose-dependent hypothermia that was blocked by pretreatment with pimozide. Oxygen uptake values during exercise following the central injection of apomorphine were virtually identical to those following the injection of saline, but colonic temperature was significantly (P less than 0.05) lower than saline controls, indicating that the hypothermia observed was not due to a reduction in metabolic rate. These data indicate that dopamine receptors in the preoptic-anterior hypothalamus of the rat participate in the mediation of heat dissipation when the animal is challenged with a heat stress.
Control of breathing in Sherpas at low and high altitude
Authors: Hackett P. H. , Reeves J. T. , Reeves C. D. , Grover R. F. , Rennie D.
Published: December 2017

Sherpas are well known for their physical performance at extreme altitudes, yet they are reported to have blunted ventilatory responses to acute hypoxia and relative hypoventilation in chronic hypoxia. To examine this paradox, we studied ventilatory control in Sherpas in comparison to that in Westerners at both low and high altitude. At low altitude, 25 Sherpas had higher minute ventilation, higher respiratory frequency, and lower end-tidal carbon dioxide tension than 25 Westerners. The hypoxic ventilatory response of Sherpas was found to be similar to that in Westerners, even though long altitude exposure had blunted the responses of some Sherpas. At high altitude, Sherpas again had higher minute ventilation and a tendency toward higher arterial oxygen saturation than Westerners. Oxygen administration increased ventilation further in Sherpas but decreased ventilation in Westerners. We conclude that Sherpas differ from other high-altitude natives; their hypoxic ventilatory response is not blunted, and they exhibit relative hyperventilation.
Body fluid and hematologic adjustments during resting heat acclimation in rhesus monkey
Authors: Oddershede I. R. , Elizondo R. S.
Published: December 2017

The purpose of this study was to examine body fluid adjustments during prolonged resting heat exposure in primates. Rhesus monkeys were acclimated for 35 days at 35 degrees C and 30% rh. Red cell mass, extracellular fluid volume (ECF), and total body water (TBW) were determined with 51Cr, 35SO4, and 3H2O, respectively, prior to and at intervals during heat exposure. Heat acclimation was characterized by a fluid shift from the interstitial compartment. In relation to TBW, interstitial fluid volume and ECF decreased 10.3 and 8.3%, respectively, while plasma volume (PV) and intracellular fluid were increased an average of 5.8 and 3.8%. TBW increased 4.8% during heat exposure. Hematocrit and hemoglobin decreased significantly on day 3 (7.9 and 6.5%) followed by a return toward control values. PV in relation to TBW remained elevated throughout the exposure. An increased drinking (25.0%) was associated with a decrease in caloric intake (30.7%) during heat acclimation. This study has provided a complete body fluid compartment analysis during resting heat acclimation in the rhesus monkey. Our results are consistent with the hypothesis that heat acclimation in primates is characterized by a protein and fluid shift from the interstitial fluid compartment to the cardiovascular system and to the intracellular compartment.
Calcium augments hypoxic vasoconstriction in lungs from high-altitude rats
Authors: Voelkel N. F. , Morris K. G. , McMurtry I. F. , Reeves J. T.
Published: December 2017

Isolated lungs from high-altitude rats compared with those from low-altitude rats have blunted hypoxic pressor responses. Because calcium is essential for the hypoxic pressor response and has been shown to be altered in the pulmonary arterial smooth muscle during high-altitude exposure, we wondered whether altered calcium metabolism might account for the blunted response. We attempted to unmask differences between high- and low-altitude rat lungs by altering extracellular calcium. The addition of calcium to the blood perfusate augmented the hypoxic pressure response of high-altitude lungs and depressed that of low-altitude lungs. Calcium addition did not affect pressor responses to angiotensin II, but slowed vasodilation after both angiotensin injection and removal of the hypoxic stimulus. The maximal KCl-induced contraction was blunted in rings of main pulmonary artery from high-altitude rats, but augmented in their aortic rings. Submaximally constricted (40 mM KCl) pulmonary arteries from low- but not high-altitude rats further constricted with calcium addition. Aortic rings exhibited an inverse behavior. Thus, calcium addition augmented the blunted vasopressor response in high-altitude rats lungs, possibly by an effect on lung arteries. The aorta and main pulmonary artery differ in calcium handling.
Ventricular volume overload alters cardiac output distribution in rats during exercise
Authors: Flaim S. F. , Minteer W. J.
Published: December 2017

A rat model for chronic left ventricular volume overload (a-v fistula, 2 mo) was used to test the effects of acute exhaustive treadmill exercise (EX) (5 min, 70 ft/min, 0 degrees grade) on cardiocirculatory hemodynamics and cardiac output (CO) distribution during heart failure (HF). Control (C) and HF rats were studied at rest (R) and during the last minute of EX. Heart rate (HR), mean arterial pressure (MAP), and left ventricular end-diastolic (LVEDP) pressure were recorded and CO, blood flow (BF) to various regions, and total CO distribution were determined by the radioactive microsphere technique. In HF, biventricular hypertrophy and elevated LVEDP at R were correlated with an average shunt size equaling 37% of total CO. In both groups, CO and HR rose during EX with no change in MAP. Systemic CO in HF was reduced compared to C during both R and EX. BF to splanchnic, renal, cutaneous, and testicular circulations was compromised at R in HF, whereas only skeletal muscle BF was compromised in HF during EX. Data for CO distribution suggest that the major effect of HF during R was increased delivery to the coronary and the skeletal muscle beds at the expense of the cutaneous and renal beds, whereas %CO to the cerebral, hepatic, and gastrointestinal beds was spared. During EX, %CO to skeletal muscle beds in HF was attenuated compared to C, whereas that to the coronary bed was increased with no change in other regions.
Brain hypoxia and control of breathing: neuromechanical control
Authors: Chapman R. W. , Santiago T. V. , Edelman N. H.
Published: December 2017

The effects of graded brain hypoxia on respiratory cycle timing, the lung inflation reflex, and respiratory compensation for an inspiratory flow-resistive load were studied in unanesthetized goats. Two models, inhalation and CO and acute reduction of brain blood flow (BBF) were used to produce comparable levels of brain hypoxia. The lung inflation reflex was assessed as the ratio of inspiratory time of an occluded breath to that of the preceding spontaneous breath (TIoccl/TIspont).

Compensation for flow-resistive loading was assessed as the effect of the load upon the airway occlusion pressure response to rebreathing CO2 (delta P 0.1/delta PCO2). Major findings were 1) severe brain hypoxia (HbCO of 60% or BBF of 42%) caused tachypnea due to a 50% or more reduction of expiratory time but only a 20% or less reduction of inspiratory time; 2) moderate carboxyhemoglobinemia (HbCO of 25-30%) enhanced TIoccl/TIspont from 1.5 +/- 0.1 at control to 2.1 +/- 0.1, while severe brain hypoxia (HbCO of 60% and BBF of 42%) reduced the ratio to 1.0 +/- 0.2; and 3) compensation for a flow-resistive load, manifested by increases of delta P 0.1/delta PCO2 of 75-300% in the control state, was abolished at HbCO of 45-50% and BBF of 60%. The data suggest that in unanesthetized animals brain hypoxia elicits tachypnea largely by an effect on the expiratory phase of the bulbopontine timing mechanism. The observed enhancement of the lung inflation reflex and abolition of flow-resistive load compensation are best explained by hypoxic depression of higher than brain stem neural function.
Relation between respiratory valve dead space and tidal volume
Authors: Bradley P. W. , Younes M.
Published: December 2017

We measured the "effective" dead space of five commonly used respiratory valves: Hans Rudolph valve, two-way J valve, triple-J valve, and modified Otis-McKerrow valves without and with vane. The dead space was measured using a technique that mimicked the operation of valves during ordinary laboratory procedures. The valves were ventilated with tidal volumes ranging from 0.35-3.00 liters and at different frequencies. With all valves, there was a marked tendency for "effective" dead space to be tidal volume dependent. The measured dead space approached the water-displacement volume of the common chamber of the valve only at tidal volumes in excess of 2.0 liters. The relation between valve dead space and tidal volume was independent of frequency.
Hysteresis in the relation between diffusing capacity of the lung and lung volume
Authors: Cassidy S. S. , Ramanathan M. , Rose G. L. , Johnson R. L.
Published: December 2017

The diffusing capacity of the lung for carbon monoxide (DLCO) varies directly with lung volume (VA) when measured during a breath-holding interval. DLCO measured during a slow exhalation from total lung capacity (TLC) to functional residual capacity (FRC) does not vary as VA changes. Since VA is reached by inhaling during breath holding and by exhaling during the slow exhalation maneuver, we hypothesized that the variability in the relation between DLCO and VA was due to hysteresis. To test this hypothesis, breath-holding measurements of DLCO were made at three lung volumes, both when VA was reached by inhaling from residual volume (RV) and when Va was reached by exhaling from TLC. At 72% TLC, DLCO was 22% higher when VA was reached by exhalation compared to inhalation (P < 0.02). At 52% TLC, DLCO was 19% higher when VA was reached by exhalation compared to exhalation (P < 0.005). DCLO measured during a slow exhalation fell on the exhalation limb of the CLCO/VA curve. these data indicate that there is hysteresis in DLCO with respect to lung volume.
Oxygen uptake and energy expenditure during horizontal treadmill running
Authors: Hagan R. D. , Strathman T. , Strathman L. , Gettman L. R.
Published: December 2017

The purpose of this investigation was to compare linear and curvilinear regression equations relating oxygen uptake and energy expenditure to running velocity and to examine the effects of age, sex, and maximal aerobic power on these relations in well-conditioned male and female runners. One-variable linear equations that use running velocity as the independent variable for predicting oxygen uptake and energy expenditure ahd coefficients of determination (r2) of 0.86 and 0.897, respectively. Two-variable linear equations that use body mass and velocity as independent variables had r2 values of 0.895 and 0.901 for the same relation. Age sex, and maximal aerobic power did not influence the relations between oxygen uptake, energy expenditure, and running velocity. Stepwise regression indicated that the two-variable linear equations had the highest r2 values suggesting that between the running velocities of 8.8 and 16.9 km.h-1 these equations best express the relation of oxygen uptake and energy expenditure to running velocity.
Model for antiorthostatic hypokinesia: head-down tilt effects on water and salt excretion
Authors: Deavers D. R. , Musacchia X. J. , Meininger G. A.
Published: December 2017

Water and electrolyte excretion was investigated in antiorthostatic hypokinetic and orthostatic hypokinetic and control rats in metabolic cages. Significant (t test, P < 0.05), diuresis, natriuresis, and kaliuresis occurred in the antiorthostatic hypokinetic subjects but did not occur in either the orthostatic hypokinetic or controls. Recovery from antiorthostatic hypokinesia was characterized by retention of water, sodium, and potassium. Patterns of changes in body weight and food and water orthostatic hypokinetic rats and thus could not account for the differences in renal handling of water and electrolytes. Also, differences in ingestion of food and water in controls could not account for differences in excretion of water and electrolytes between these and antiorthostatic hypokinetic rats. It was concluded that the antiorthostatic position was responsible for the diuresis and natriuresis and that the antiorthostatic hypokinetic rat appears to be a good model for the study of water and electrolyte excretion during conditions such as bed rest, water immersion, and exposure to weightlessness.
Functional overload of rat fast-twitch skeletal muscle during development
Authors: Belcastro A. N. , Wenger H. , Nihei T. , Secord D. , Bonen A.
Published: December 2017

The intent of this study was observe the effects of different training programs on selected biochemical properties in lantaris muscle of young rats. Littermates (10 days old) were assigned to endurance (E), sprint (S), and control (C) groups. Animals in each group were partitioned into either 21- or 51-day groups and 10-day controls. Myofibrillar ATPase activities at 21 and 51 days (0.720 +/- 0.028 and 0.719 +/- 0.012 mumol Pi.mg-1.min-1) were higher than the 10-day activity (0.191 +/- 0.022 mumol Pi.mg-1.min) for C animals (P less than or equal to 0.05). At 51 days, E training resulted in a lower ATPase activity than both the 21-day E and 51-day C animals (P less than or equal to 0.05). Sarcoplasmic reticulum protein yield and Ca2+ binding and uptake increased from 10 to 51 days for C animals (P less than or equal to 0.05). The Ca2+-binding ability for 51-day E animals (26.1 +/- 3.4 nmol Ca2+/mg) was greater than for the 51-day C animals (20.0 +/- 1.69 nmol Ca2+/mg) (P less than or equal to 0.05). The plantaris muscle of S animals were not altered at 21 and 51 days compared to C animals were not altered at 21 and 51 days compared to C animals (all variables). The results suggest that exercise training alters the biochemical characteristics of skeletal muscle during growth.
Phasic vagal influence on inspiratory motor output in anesthetized human subjects
Authors: Polacheck J. , Strong R. , Arens J. , Davies C. , Metcalf I. , Younes M.
Published: December 2017

Vagal influence on inspiratory motor output was assessed in 20 normal subjects and in 12 patients with respiratory disorders under enflurane anethesia using the method of airway occlusion. The change in inspiratory duration during occlusion (delta TI) was measured from mechanical parameters (respiratory flow and tracheal pressure). In eight of the subjects, however, the effect of occlusion and augmentation of tidal volume was further evaluated from diaphragmatic electromyogram. In normal subjects delta TI (mechanical) averaged 0.15 s (range -0.1 to +0.77 s) and correlated with the duration of inspiration during occlusion. Electromyographic observations indicated that the change in neural TI exceeds the change in mechanical TI by approximately 0.2 s and that augmentation of tidal volume shortens TI with no apparent volume threshold. There was a tendency for vagal influence to be higher with restrictive lung disease and lower with obstructive airway disease. These observations indicate that a majority of humans display a significant vagal influence on TI in the spontaneous tidal volume range under anesthesia.
Effect of pulmonary venous pressure on steady-stage collateral resistance
Authors: Fuller S. D. , Robinson N. E. , Scott J. B.
Published: December 2017

Steady-state collateral resistance (Rcoll), residual volume (RV), and lung pressure-volume (PV) relations were determined in an isolated perfused dog lung as pulmonary venous pressure (Ppv) was increased. Increased Ppv had no effect on the lung PV curve except for a significant increase in RV when Ppv equaled or exceeded 20 Torr. When compared to the value at Ppv = 5 Torr, significant decreases in Rcoll occurred when Ppv was raised to 15 Torr or above at transpulmonary pressure, PL = 0 cmH2O, to 20 Torr or above when PL = 2 cmH2O, and to 25 Torr or above when PL = 4 cmH2O. In most dogs the decrease in Rcoll with increased Ppv could be explained by increased lung volume.
Influence of opsonic fibronectin deficiency on lung fluid balance during bacterial sepsis
Authors: Niehaus G. D. , Schumacker P. T. , Saba T. M.
Published: December 2017

Lung microvascular permeability in sheep increases during Pseudomonas bacteremia. The sheep's low plasma opsonic fibronectin concentration and associated inefficient reticuloendothelial clearance of blood-borne particulates may contribute to the response of increased lung vascular permeability during sepsis. The present study investigated the influence of sepsis on lung fluid balance in sheep with and without opsonic glycoprotein (plasma fibronectin) deficiency. Using the lung lymph fistula preparation in sheep, we made measurements of lung lymph flow (QLYM), lymph-to-plasma protein concentration ratios (L/P), pulmonary hemodynamics, and extravascular lung water content. Deficiency of opsonic fibronectin resulted in a minimal increase in lymph flow with no change in transvascular protein clearance (QLYM X L/P). Pseudomonas sepsis with or without fibronectin deficiency resulted in a stable L/P and a transient increase in pulmonary arterial pressure, which declined to a new steady state. Although sepsis resulted in a 100% elevation (P < 0.05) in lymph flow and transvascular protein clearance, sepsis in the presence of fibronectin deficiency induced a sustained 300--400% increase in lymph flow and a 300% increase in transvascular protein clearance. Thus opsonic fibronectin deficiency exaggerates the increased lung vascular permeability during sepsis.
Effect of plasma carbonic anhydrase on ventilation in exercising dogs
Authors: Lewis S. M. , Hill E. P.
Published: December 2017

Recent studies suggest pH sampled by arterial chemoreceptors may not equal that sampled by external pH electrodes, because the uncatalyzed hydration of CO2 in plasma is a slow reaction (t 1/2 approximately 9 S). The importance of this reaction rate to ventilatory control (particularly during exercise) is not known. We studied the effect of catalyzing the CO2-pH reaction in three awake exercising dogs with chronic tracheostomies and carotid loops; the dogs were trained to run on a treadmill. Respiration frequency, tidal volume, total ventilation, and end-tidal partial pressure of CO2 (PCO2) were continuously monitored. Periodically, carotid artery blood was drawn and analyzed for partial pressure of O2 (PO2), PCO2, pH, and plasma carbonic anhydrase (CA) activity. Measurements were made during steady-state exercise (3 mph and 10% grade), during a control period, after injection of a 5 ml bolus of saline, and after injection of 5 mg/kg of bovine CA dissolved in 5 ml of saline. This dose of CA increased the reaction rate by more than 80-fold. Neither the control nor the CA injections significantly altered the ventilatory parameters. Saline and CA date differed by less than 5% in ventilation, 1 Torr in arterial PCO2, 0.01 in pH units, and 1.5 Torr in end-tidal PCO2. Thus the of CO2 hydration in plasma is not a significant factor in ventilatory control.
Improved esophageal balloon technique for use in infants
Authors: Beardsmore C. S. , Helms P. , Stocks J. , Hatch D. J. , Silverman M.
Published: December 2017

Esophageal balloons of three different wall thicknesses, two different lengths, and two different diameters were made to assess which type of balloon gave the most consistent and reliable measurements of dynamic compliance (CL) and pulmonary resistance (Rp). The balloons were subjected to in vitro testing to determine their pressure-volume characteristics and working range and then used in infants to compare in vivo results from one balloon to another. The optimal balloon was found to have a length of 35--50 mm, a diameter of 7.6 mm, and a wall thickness of 0.045--0.075 mm. The use of unsuitable balloons or inappropriate volumes of air within the balloon resulted in applied pressures being under-recorded, both in vitro and in vivo, with consequent overestimation of CL and underestimation of Rp during infant lung function tests. Recommendations are made concerning the techniques of making and using esophageal balloons.
Possible alterations in brain monoamine metabolism during hypoxia-induced tachypnea in cats
Authors: Gautier H. , Bonora M.
Published: December 2017

In carotid body-denervated cats, moderate hypoxia, or even normoxia when compared to hyperoxia, provokes a significant depression of the respiratory output. This is observed in conscious or anesthetized or decerebrated animals. On the other hand, more severe hypoxia induces tachypnea (hypoxic tachypnea of Miller and Tenney, Respir. Physiol. 23: 31-39, 1975) in conscious cats, whereas the same hypoxia is followed by marked respiratory depression or apnea in the anesthetized or decerebrated animals. Hypoxic tachypnea can be partly or completely reversed by injection of dopa or xanthines such as caffeine or aminophylline. This suggests that alterations in brain monoamine metabolism by hypoxia may be responsible for the alterations in suprapontine respiratory control systems, resulting the tachypnea. Mild hypercapnia can also reverse hypoxic tachypnea. It is concluded that the ventilatory response to hypoxia of conscious animals results from stimulation of peripheral chemoreceptors, inhibition of brain stem neurons, and finally involvement of suprapontine structures that seems to be mediated by depletion of monoamines.
Stability of alveolar hypoxic vasoconstriction with intermittent hypoxia
Authors: Miller M. A. , Hales C. A.
Published: December 2017

Repeated intermittent global hypoxia has been reported to markedly enhance hypoxic pulmonary vasoconstriction in dogs. We have reexamined this phenomenon but with intermittent unilateral alveolar hypoxia, avoiding complications of systemic hypoxemia. Fifteen anesthetized dogs were intubated with a double-lumen endotracheal tube, allowing separate ventilation of one lung with 100% N2 as a hypoxic challenge and the other lung with 100% O2 to maintain adequate systemic oxygenation. Distribution of lung perfusion was determined with intravenous 133Xe and external chest detectors. Each dog alternately breathed air or the unilateral alveolar hypoxia combination for 15 min each for a total of 12 hypoxic challenges or 6 h. Two groups emerged on the basis of the strength of their vasoconstrictor responses to successive hypoxic challenge. In group I (n = 6), perfusion to the hypoxic lung decreased 29% with the first challenge and decreased comparably with successive challenges. In group II, vasoconstriction was initially weak with perfusion decreasing only 5%, but perfusion decreased further with time alone (n = 5) or successive challenges (n = 4), falling 35% on the 12th challenge (comparable to group I). Delayed achievement of hypoxic vasoconstriction in group II may be secondary to a vasodilating prostanoid that disappears with time.
Airway effects of respiratory heat loss in normal subjects
Authors: O'Cain C. F. , Dowling N. B. , Slutsky A. S. , Hensley M. J. , Strohl K. P. , McFadden E. R. , Ingram R. H.
Published: December 2017

The increased minute ventilation (VE) associated with exercise produces similar degrees of airway cooling in normal and asthmatic subjects, but only those with asthma develop postexertional bronchoconstriction in response to this stimulus. We have found that when normal subjects breathing subfreezing air perform isocapnic hyperventilation to levels exceeding those associated with even exhausting exercise, 1-s forced expiratory volumes and maximum midexpiratory flow rates fall significantly. When tests more sensitive in detecting bronchoconstriction are employed, changes are seen at lower levels of hyperventilation that simulate the VE associated with moderately heavy work loads. We conclude that normal subjects respond to airway cooling, but are much less sensitive than those with asthma.
Resting metabolic rate and cost of locomotion in long-term fasting emperor penguins
Authors: Dewasmes G. , Le Maho Y. , Cornet A. , Groscolas R.
Published: December 2017

During the Antarctic winter emperor penguins fast for up to 120 days when breeding at rookeries, which may be as much as 120 km from open water. Emperors have lost almost half of their body mass by the time they walk back to the sea to feed. Resting metabolic rate and metabolic rate during treadmill walking at 1.4 km times h-1 were measured regularly along the course of 63-118 days of fasting in four emperors that lost between 33 and 55% of their body mass. Resting metabolic rate decreased linearly with body mass throughout the fast; it was 76 and 50 W at 39 and 18 kg body mass, respectively, which therefore corresponds to a limited increase in the resting metabolic rate per unit of body mass. There was a considerable decrease in the metabolic rate for walking at 1.4 km times h-1, from 340 to 140 W at body masses of 39 and 18 kg, respectively; this decrease was linear with body mass but at a steeper rate below 23 kg. From 39 to 23 kg, the cost of walking per unit of body mass remained constant. Below 23 kg (a point where about 2.5 kg of fat remain), the increased efficiency for walking may be due to a change in the mechanics of locomotion.