bluuebunny/crossref_metadata_2025 huggingface dataset:
Sympathetic response to exercise in various tissues with advancing age
Authors: Mazzeo R. S. , Grantham P. A.
Published: December 2017

It was the purpose of this investigation to examine any age-related changes in norepinephrine turnover (NEt) in four tissues at rest and during exercise. Fischer 344 rats 6 (n = 20) and 25 mo of age (n = 20) were received from the National Institute on Aging. NEt was determined at rest, during 30 min of submaximal exercise, and at maximal exercise by administration of alpha-methyl-p-tyrosine, a competitive inhibitor of tyrosine hydroxylase. Resting NE declined with age in both heart (38.2 vs. 30.5 ng.g-1.h-1) and liver (11.2 vs. 6.4 ng.g-1.h-1). NEt was greater in the older animals compared with the young animals in heart (120.9 vs. 169.5 ng.g-1.h-1), liver (23.1 vs. 38.9 ng.g-1.h-1), and adrenals (74.0 vs. 98.4 ng.mg-1.h-1) during submaximal exercise. In response to maximal exercise, NEt varied depending on age and tissue. It was concluded that, in response to exercise stress, the older animals generally demonstrated a higher NEt (reflecting elevated sympathetic activity) perhaps because of a decreased adrenergic receptor sensitivity and/or responsiveness.
Effects of negative upper airway pressure on pattern of breathing in sleeping infants
Authors: Thach B. T. , Menon A. P. , Schefft G. L.
Published: December 2017

Negative upper airway (UAW) pressure inhibits diaphragm inspiratory activity in animals, but there is no direct evidence of this reflex in humans. Also, little is known regarding reflex latency or effects of varying time of stimulation during the breathing cycle. We studied effects of UAW negative pressure on inspiratory airflow and respiratory timing in seven tracheostomized infants during quiet sleep with a face mask and syringe used to produce UAW suction without changing lower airway pressure. Suction trials lasted 2–3 s. During UAW suction, mean and peak inspiratory airflow as well as tidal volume was markedly reduced (16–68%) regardless of whether stimulation occurred in inspiration or expiration. Reflex latency was 42 +/- 3 ms. When suction was applied during inspiration or late expiration, the inspiration and the following expiration were shortened. In contrast, suction applied during midexpiration prolonged expiration and tended to prolong inspiration. The changes in flow, tidal volume, and timing indicate a marked inhibitory effect of UAW suction on thoracic inspiratory muscles. Such a reflex mechanism may function in preventing pharyngeal collapse by inspiratory suction pressure.
Effect of dietary fish oil on lung lipid profile and hypoxic pulmonary hypertension
Authors: Archer S. L. , Johnson G. J. , Gebhard R. L. , Castleman W. L. , Levine A. S. , Westcott J. Y. , Voelkel N. F. , Nelson D. P. , Weir E. K.
Published: December 2017

The effects of dietary polyunsaturated fats on chronic hypoxic pulmonary hypertension were assessed in rats fed fish oil, corn oil, or a lower fat, “high-carbohydrate” diet (regular) beginning 1 mo before the start of hypoxia (0.4 atm, n = 30 for each). Mean pulmonary arterial pressures were lower in the chronically hypoxic rats fed fish oil (19.7 +/- 1.8 mm Hg) than in the rats fed corn oil (25.3 +/- 1.6 mm Hg) or regular diets (27.5 +/- 1.5 mm Hg, P less than 0.05). The fish oil diet increased lung eicosapentaenoic acid 50-fold and depleted lung arachidonic acid 60% (P less than 0.0001 for each). Lung thromboxane B2 and 6-ketoprostaglandin F1 alpha levels were lower, and platelet aggregation, in response to collagen, was reduced in rats fed fish oil. Chronically hypoxic rats fed fish oil had lower mortality rates than the other hypoxic rats. They also had lower blood viscosity, as well as less right ventricular hypertrophy and less peripheral extension of vascular smooth muscle to intra-acinar pulmonary arteries (P less than 0.05 for each). The mechanism by which dietary fish oil decreases pulmonary hypertension and vascular remodeling during chronic hypoxia remains uncertain. The finding that a fish oil diet can reduce the hemodynamic and morphological sequelae of chronic hypoxia may have therapeutic significance.
Vascular collagen affects reactivity of hypertensive pulmonary arteries of the rat
Authors: Tozzi C. A. , Poiani G. J. , Edelman N. H. , Riley D. J.
Published: December 2017

We studied the role of vascular collagen on the responsiveness of isolated pulmonary arteries to vasoactive agonists. Dose-response curves to prostaglandin F2 alpha, (PGF2 alpha), angiotensin II (ANG II), and norepinephrine (NE) and responses to a depolarizing concentration of KCl were obtained on rings of pulmonary artery from normal rats, chronically hypoxic (10% O2 for 10 days) rats, and chronically hypoxic rats treated with cis-4-hydroxy-L-proline (cHyp), an agent that blocks collagen accumulation. Treatment with this agent prevented the rise in pulmonary blood pressure normally seen during hypoxia. Collagen content was twice normal in hypoxic vessels and was significantly reduced in vessels from cHyp-treated hypoxic rats. There was no change in reactivity to PGF2 alpha, but reactivity to ANG II, NE, and KCl was decreased in vessels from hypoxic rats. cHyp treatment completely restored reactivity to NE and KCl and partially restored reactivity to ANG II. The changes in contractility could be a response to the lower blood pressure. Another explanation is that collagen deposited in hypertensive pulmonary arteries may impair reactivity to some constrictor agonists.
Influence of physical training on heart rate variability and baroreflex circulatory control
Authors: Seals D. R. , Chase P. B.
Published: December 2017

Nineteen males (aged 45–68 yr) were studied before and after either a period of regular endurance exercise [walk/jog 3–4 days/wk for 30 +/- 1 (SE) wk, n = 11] or unchanged physical activity (38 +/- 2 wk, n = 8) (controls) to determine the influence of physical training on cardiac parasympathetic (vagal) tone and baroreflex control of heart rate (HR) and limb vascular resistance (VR) at rest in middle-aged and older men. Training resulted in a marked increase in maximal O2 uptake (31.6 +/- 1.2 vs. 41.0 +/- 1.8 ml.kg-1.min-1, 2.56 +/- 0.16 vs. 3.20 +/- 0.18 l/min, P less than 0.05) and small (P less than 0.05) reductions in body weight (81.2 +/- 3.5 vs. 78.7 +/- 4.0 kg) and body fat (23.8 +/- 1.3 vs. 20.9 +/- 1.3%). HR at rest was slightly, but consistently, lower after training (63 +/- 2 vs. 58 +/- 1 beats/min, P less than 0.05). In general, HR variability (index of cardiac vagal tone) was greater after training. Chronotropic responsiveness to either brief carotid baroreflex stimulation (neck suction) or inhibition (neck pressure), or to non-specific arterial baroreflex inhibition induced by a hypotensive level of lower body suction, was unchanged after training. In contrast, the magnitude of the reflex increase in forearm VR in response to three levels of lower body suction was markedly attenuated after training (38–59%; P less than 0.05 at -10 and -30 mmHg; P = 0.07 at -20 mmHg). None of these variables or responses was altered over time in the controls. These findings indicate that in healthy, previously sedentary, middle-aged and older men, strenuous and prolonged endurance training 1) elicits large increases in maximal exercise capacity and small reductions in HR at rest, 2) may increase cardiac vagal tone at rest, 3) does not alter arterial baroreflex control of HR, and 4) results in a diminished forearm vasoconstrictor response to reductions in baroreflex sympathoinhibition.
Respiratory effects of the Jarvik-7 artificial heart
Authors: Rouby J. J. , Leger P. , Arthaud M. , Devilliers C. , Cabrol A. , Gandjbakch I. , Cabrol C. , Viars P.
Published: December 2017

In five anesthetized patients with a Jarvik-7 artificial heart, pulmonary volume displacements generated by cardiogenic oscillations were measured using an indirect spirometric method. Consequences on gas exchange were also evaluated during a 15-min period of apnea by use of a tracheal insufflation of pure O2 at a constant flow rate of 20 l/min. The Jarvik-7 artificial heart generated a mean pulmonary volume displacement of 105 +/- 29 (SD) ml/heart beat. After 15 min of apnea, arterial PCO2 (PaCO2) significantly increased from 29 +/- 5 to 47 +/- 6 (SD) Torr. PaCO2 increased by 0.8 Torr/min from the 5th to the 15th min of apnea. Mean arterial PO2, mean pulmonary shunt, mean O2 consumption, and mean metabolic production of CO2 did not change significantly during the apnea period. Because cardiac output was kept constant during the study, O2 transport was adequately maintained throughout the apnea period. In patient 1, where the period of apnea was continued for 60 min, PaCO2 progressively increased until the 45th min and then remained stable at 61 Torr during the last 15 min of apnea. This “plateau” corresponded to an alveolar ventilation of 3,907 ml/min, representing 69% of the alveolar ventilation calculated during conventional mechanical ventilation. In conclusion, the Jarvik-7 artificial heart provides a potent respiratory support through the cardiogenic oscillations it generates.
Respiratory epithelial permeability after cigarette smoke exposure in guinea pigs
Authors: Burns A. R. , Hosford S. P. , Dunn L. A. , Walker D. C. , Hogg J. C.
Published: December 2017

The purpose of this study was to determine the pathology of cigarette smoke-increased permeability at the bronchioalveolar junction of the guinea pig. After exposure to either smoke or room air, guinea pigs were anesthetized and fluorescein isothiocyanate-dextran (FITC-D, mol wt 10,000) was aerosolized into their lungs. Blood samples taken through a carotid arterial cannula were analyzed by gel chromatography and spectrofluorometry for the presence of FITC-D. The results confirmed that, after smoke exposure, increased amounts of intact FITC-D molecules with a reported Einstein-Stokes radius of 22.2 A crossed the respiratory epithelium into the vascular space. Transmission electron-microscopic studies showed that the FITC-D diffused across damaged type I pneumocyte membranes and cytoplasm to reach the basal lamina and entered the alveolar capillaries through endothelial tight junctions. Damage to the alveolar epithelium was more frequent for the smoke-exposed animals than the room air-exposed animals (P less than 0.05). We conclude that smoke exposure damages type I cells and that inhaled FITC-D crosses the epithelial barrier at damaged type I cells of the bronchioloalveolar junctions.
Skeletal muscle O2 consumption and energy metabolism during hypoxemia
Authors: Gutierrez G. , Pohil R. J. , Narayana P.
Published: December 2017

We determined the relationship of O2 transport (TO2) to O2 consumption (VO2) and to changes in cellular bioenergetics in an isolated blood-perfused rabbit hindlimb preparation (n = 8) during hypoxemia. The preparations were subjected to reductions in TO2 by progressively decreasing partial pressure of arterial O2 (PaO2). At each level of PaO2 we obtained simultaneous measures of arterial and venous blood gases, venous lactate concentration, and changes in the relative concentrations of inorganic phosphate, phosphocreatine, and ATP measured with 31P magnetic resonance spectroscopy. The ratio of the change in vascular resistance (R) to the corresponding decrease in TO2 was taken as an index of vascular autoregulation with hypoxemia. Linear and logarithmic functions were fitted by least squares to the TO2-VO2 data from each experiment. TO2-VO2 relationships were characterized as O2 conforming (linear function, n = 4) or O2 regulating (logarithmic function, n = 4), depending on the goodness of fit. Those preparations showing an O2-conforming pattern had higher control VO2 (2.42 +/- 0.14 vs. 1.66 +/- 0.19 ml.min-1.kg-1; P less than 0.05) and a lesser degree of vascular autoregulation (0.07 +/- 0.03 vs. 0.21 +/- 0.02; P less than 0.01) than the O2-regulating group. Decreases in VO2 were always accompanied by increases in inorganic phosphate and lactate and decreases in phosphocreatine, indicating O2 supply limitation and anaerobic ATP production. There was no evidence of cellular adaptation to hypoxia by decreasing energy needs or of VO2 limitation by the depletion of adenine nucleotides.
Effect of negative-pressure ventilation on lung water in permeability pulmonary edema
Authors: Skaburskis M. , Michel R. P. , Gatensby A. , Zidulka A.
Published: December 2017

We have previously shown (Am. Rev. Respir. Dis. 136: 886–891, 1987) improved cardiac output in dogs with pulmonary edema ventilated with external continuous negative chest pressure ventilation (CNPV) using negative end-expiratory pressure (NEEP), compared with continuous positive-pressure ventilation (CPPV) using equivalent positive end-expiratory pressure (PEEP). The present study examined the effect on lung water of CNPV compared with CPPV to determine whether the increased venous return created by NEEP worsened pulmonary edema in dogs with acute lung injury. Oleic acid (0.06 ml/kg) was administered to 27 anesthetized dogs. Supine animals were then divided into three groups and ventilated for 6 h. The first group (n = 10) was treated with intermittent positive-pressure ventilation (IPPV) alone; the second (n = 9) received CNPV with 10 cmH2O NEEP; the third (n = 8) received CPPV with 10 cmH2O PEEP. CNPV and CPPV produced similar improvements in oxygenation over IPPV. However, cardiac output was significantly depressed by CPPV, but not by CNPV, when compared with IPPV. Although there were no differences in extravascular lung water (Qwl/dQl) between CNPV and CPPV, both significantly increased Qwl/dQl compared with IPPV (7.81 +/- 0.21 and 7.87 +/- 0.31 vs. 6.71 +/- 0.25, respectively, P less than 0.01 in both instances). CNPV and CPPV, but not IPPV, enhanced lung water accumulation in the perihilar areas where interstitial pressures may be most negative at higher lung volumes.
Flutter in collapsible tubes: a theoretical model of wheezes
Authors: Grotberg J. B. , Gavriely N.
Published: December 2017

A mathematical analysis of flow through a flexible channel is examined as a model of flow-induced flutter oscillations that pertain to the production of wheezing breath sounds. The model provides predictions for the critical fluid speed that will initiate flutter waves of the wall, as well as their frequency and wavelength. The mathematical results are separated into linear theory (small oscillations) and nonlinear theory (larger oscillations). Linear theory determines the onset of the flutter, whereas nonlinear theory determines the relationships between the fluid speed and both the wave amplitudes and frequencies. The linear theory predictions correlate well with data taken at the onset of flutter and flow limitation during experiments of airflow in thick-walled collapsible tubes. The nonlinear theory predictions correlate well with data taken as these flows are forced to higher velocities while keeping the flow rate constant. Particular ranges of the parameters are selected to investigate and discuss the applications to airway flows. According to this theory, the mechanism of generation of wheezes is based in the interactions of fluid forces and friction and wall elastic-restoring forces and damping. In particular, a phase delay between the fluid pressure and wall motion is necessary. The wave speed theory of flow limitation is discussed with respect to the specific data and the flutter model.
Effect of upper airway shunt and series properties on respiratory impedance measurements
Authors: Cauberghs M. , Van de Woestijne K. P.
Published: December 2017

Because of the contradictory statements published about the influence of the shunt properties of the upper airway on the measurements of the respiratory impedence by means of the forced oscillation technique, this influence has been reevaluated. In healthy adults and children and in patients with obstructive lung disease, the total respiratory impedance was measured by applying oscillations at the mouth (conventional technique) or around the head (head generator technique), with the cheeks either supported by the hands or not. In healthy adults the two techniques (conventional cheeks supported and head generator) yield similar results for respiratory resistance (Rrs) and a more pronounced increase of respiratory reactance (Xrs) with frequency with the head generator. In children and in patients with moderate airway obstruction, the negative frequency dependence of Rrs observed with the conventional technique tends to disappear with the head generator. This is not observed in patients with severe airway obstruction. The differences between the two techniques can be explained by the influence of the shunt impedance of the upper airway on Rrs and Xrs. Correction for this influence by subtracting the impedance measured during a Valsalva maneuver is not satisfactory, since the Valsalva maneuver itself modifies the upper airway shunt. The head generator technique reduces the influence of the upper airway shunt but does not suppress it altogether; the residual error is small, however.
Effects of inspiratory elastic load on respiratory control in hypercapnia and exercise
Authors: Poon C. S.
Published: December 2017

Five healthy young men underwent two separate steady-state incremental exercise runs within the aerobic range on a treadmill with alternating periods of breathing with no load (NL) and with a discontinuous inspiratory elastic load (IEL) of approximately 10 cmH2O/l. End-tidal PCO2 was maintained constant throughout each run at the eucapnic or a constant hypercapnic level by adding 0–5% CO2 to the inspired O2. Hypercapnia caused a steepening, as well as upward shift, relative to the corresponding eucapnic ventilation-CO2 output (VE-VCO2) relationship in NL and IEL. Compared with NL, the VE-VCO2 slope was depressed by IEL, more so in hypercapnic [-28.7 +/- 7.2 (SE) %] than in eucapnic exercise (-16.0 +/- 2.8%). The steady-state hypercapnic ventilatory response at rest was also markedly depressed (-32.1 +/- 11.2%). Occlusion pressure response was augmented in response to IEL during eucapnic exercise (88.7 +/- 13.3%) but not during CO2 inhalation at rest or during exercise. Breathing pattern characteristics were similar regardless of the type of stimulus input and the level of inspiratory load. Results are consistent with the notion that the control of VE and breathing pattern may both be influenced by a balance between the prevailing chemical drive and a propensity of the controller to reduce respiratory effort.
Beta-adrenergic receptors are not responsible for exercise stimulation of glucose transport
Authors: Sternlicht E. , Barnard R. J. , Grimditch G. K.
Published: December 2017

This study was designed to examine whether the increased glucose transport after acute exercise in rat skeletal muscle is mediated via beta-adrenergic receptor stimulation. Sarcolemmal (SL) membranes were isolated from three groups: control (C), acute exercise (E), and exercise + propranolol (E+P). The acute exercise bout was performed on a treadmill and consisted of a 45-min run until near exhaustion. E+P received an intravenous propranolol injection (0.8 mg/kg) 10 min before the exercise session. Michaelis-Menten kinetics at 1.5 s indicated that the Vmax for glucose transport was increased after each perturbation compared with C but were not different from each other (E, 4,334 +/- 377; E+P, 4,824 +/- 357; and C, 1,366 +/- 124 pmol.mg protein-1.s-1). The apparent Km's were similar in all groups. Scatchard plots for the D-glucose inhibitable class of cytochalasin B binding sites indicated no differences in either the total number of binding sites in the SL vesicles (C, 5.5 +/- 0.3; E, 5.1 +/- 0.2, and E+P, 5.1 +/- 0.3 pmol/mg protein) or in their dissociation constant (Kd) (C, 46 +/- 3; E, 48 +/- 3; and E+P, 49 +/- 2 nM). The increase in Vmax for transport was similar between E and E+P, indicating that exercise does not stimulate glucose transport via the beta-adrenergic receptor.
Sympathetic neural discharge and vascular resistance during exercise in humans
Authors: Seals D. R.
Published: December 2017

The purpose of this study was to determine the relationship between changes in efferent muscle sympathetic nerve activity (MSNA) to the lower leg and calf vascular resistance (CVR) during isometric exercise in humans. We made intraneural (microneurographic) determinations of MSNA in the right leg (peroneal nerve) while simultaneously measuring calf blood flow to the left leg, arterial pressure, and heart rate in 10 subjects before (control), during, and after (recovery) isometric handgrip exercise performed for 2.5 min at 15, 25, and 35% of maximal voluntary contraction (MVC). Heart rate and arterial pressure increased above control within the initial 30 s of handgrip at all levels, and the magnitudes of the increases at end contraction were proportional to the intensity of the exercise. In general, neither MSNA nor CVR increased significantly above control levels during handgrip at 15% MVC. Similarly, neither variable increased above control during the initial 30 s of handgrip at 25 and 35% MVC; however, during the remainder of the contraction period, progressive, parallel increases were observed in MSNA and CVR (P less than 0.05). The correlation coefficients relating changes in MSNA to changes in CVR for the individual subjects averaged 0.63 +/- 0.07 (SE) (range 0.30–0.91) and 0.94 +/- 0.06 (range 0.80–0.99) for the 25 and 35% MVC levels, respectively. During recovery, both MSNA and CVR returned rapidly toward control levels. These findings demonstrate that muscle sympathetic nerve discharge and vascular resistance in the lower leg are tightly coupled during and after isometric arm exercise in humans. Furthermore, the exercise-induced adjustments in the two variables are both contraction intensity and time dependent.
Dynamic response of local pulmonary blood flow to alveolar gas tensions: experiment
Authors: Paradowski L. J. , Grant B. J.
Published: December 2017

The purpose of this study was to investigate the mechanism that causes a damped oscillatory response of local pulmonary blood flow to local hypoxia. The left lower lobe (LLL) of 10 anesthetized dogs was ventilated independently but synchronously with the rest of the lungs. Blood flow to the LLL as a proportion of total flow (QLLL/QT) was measured during the on-transient of the hypoxic response when LLL inspirate was changed from O2 to N2. There was a damped oscillatory response of QLLL/QT to hypoxia (34 of 40 trials). In contrast, the off-transient was always monotonic. There was no enhancement of the steady state or dynamic hypoxic response with repeated challenges. Local alveolar hypercapnia caused a damped oscillatory response in the presence of local hypoxia (15 of 20 trials), but there was no response in the presence of local hyperoxia. We conclude that 1) the dynamic pulmonary vascular response to O2 and CO2 are not additive because the response to CO2 is attenuated by hyperoxia and 2) the damped oscillatory response that occurs during hypoxia is the result of changes of local alveolar CO2 per se.
Effects of starvation and refeeding on elastase-induced emphysema
Authors: Sahebjami H. , Domino M.
Published: December 2017

Adult rats received pancreatic elastase (75 U/100 g) intratracheally and were divided into three groups: fed, starved, and refed. Starved rats received one-third of their measured daily food consumption until they lost 40% body weight. The refed group was fed after 40% weight loss. A control group received saline intratracheally. Saline volume-pressure curve was shifted more significantly to the left of the control group in starved than in fed rats and was superimposed in refed and fed groups. Mean linear intercept was larger and alveolar surface area was smaller in starved than in fed rats compared with the control group; both were similar in fed and refed rats. Protein and hydroxyproline content of the lung were higher in fed than in control and in starved groups; after refeeding these returned to the control values. We conclude that starvation aggravates elastase-induced injury and that refeeding results in the complete recovery of the mechanical but only partial recovery of the morphometric changes induced by starvation.
Propagation of stress waves in inflated sheep lungs
Authors: Jahed M. , Lai-Fook S. J. , Bhagat P. K. , Kraman S. S.
Published: December 2017

If the lung is an elastic continuum, both longitudinal and transverse stress waves should be propagated in the medium with distinct velocities. In five isolated sheep lungs, we investigated the propagation of stress waves. The lungs were degassed and then inflated to a constant transpulmonary pressure (Ptp). We measured signals transmitted at locations approximately 1.5, 6, and 11 cm from an impulse surface distortion with the use of small microphones embedded in the pleural surface. Two transit times were computed from the first two significant peaks of the cross-correlation of microphone signal pairs. The “fast” wave velocities averaged 301 +/- 92, 445 +/- 80, and 577 +/- 211 (SD) cm/s for Ptp values of 5, 10, and 15 cmH2O, respectively. Corresponding “slow” wave velocities averaged 139 +/- 22, 217 +/- 36, and 255 +/- 89 cm/s. The fast waves were consistent with longitudinal waves of velocity [(K + 4G/3)/p]1/2, where bulk modulus K = 4 Ptp and shear modulus G = 0.7 Ptp. The slow waves were consistent with transverse (and/or Rayleigh) waves of velocity (G/p)1/2, with a G value of 0.9 Ptp. Measured values of K were 5 Ptp and values of G measured by indentation tests were 0.7 Ptp. Thus, stress wave velocities measured on pleural surface of isolated lungs correlated well with elastic moduli of lung parenchyma.
Increased exercise SaO2 independent of ventilatory acclimatization at 4,300 m
Authors: Bender P. R. , McCullough R. E. , McCullough R. G. , Huang S. Y. , Wagner P. D. , Cymerman A. , Hamilton A. J. , Reeves J. T.
Published: December 2017

Arterial O2 saturation (Sao2) decreases in hypoxia in the transition from rest to moderate exercise, but it is unknown whether other several weeks at high altitude SaO2 in submaximal exercise follows the same time course and pattern as that of ventilatory acclimatization in resting subjects. Ventilatory acclimatization is essentially complete after approximately 1 wk at 4,300 m, such that improvement in submaximal exercise SaO2 would then require other mechanisms. On days 2, 8, and 22 on Pikes Peak (4,300 m), 6 male subjects performed prolonged steady-state cycle exercise at 79% maximal O2 uptake (VO2 max). Resting SaO2 rose from day 1 (78.4 +/- 1.6%) to day 8 (87.5 +/- 1.4%) and then did not increase further by day 20 (86.4 +/- 0.6%). During exercise, SaO2 values (mean of 5-, 15-, and 30-min measurements) were 72.7% (day 2), 78.6% (day 8), and 82.3% (day 22), meaning that all of the increase in resting SaO2 occurred from day 1 to day 8, but exercise SaO2 increased from day 2 to day 8 (5.9%) and then increased further from day 8 to day 22 (3.7%). On day 22, the exercise SaO2 was higher than on day 8 despite an unchanged ventilation and O2 consumption. The increased exercise SaO2 was accompanied by decreased CO2 production. The mechanisms responsible for the increased exercise SaO2 require further investigation.
Glycogen supercompensation in rat soleus muscle during recovery from nonweight bearing
Authors: Henriksen E. J. , Kirby C. R. , Tischler M. E.
Published: December 2017

The time course of glycogen changes in soleus muscle recovering from 3 days of nonweight bearing by hindlimb suspension was investigated. Within 15 min and up to 2 h, muscle glycogen decreased. Coincidentally, muscle glucose 6-phosphate and the fractional activity of glycogen phosphorylase, measured at the fresh muscle concentrations of AMP, increased. Increased fractional activity of glycogen synthase during this time was likely the result of greater glucose 6-phosphate and decreased glycogen. From 2 to 4 h, when the synthase activity remained elevated and the phosphorylase activity declined, glycogen levels increased (glycogen supercompensation). A further increase of glycogen up to 24 h did not correlate with the enzyme activities. Between 24 and 72 h, glycogen decreased to control values, possibly initiated by high phosphorylase activity at 24 h. At 12 and 24 h, the inverse relationship between glycogen concentration and the synthase activity ratio was lost, indicating that reloading transiently uncoupled glycogen control of this enzyme. These data suggest that the activities of glycogen synthase and phosphorylase, when measured at physiological effector levels, likely provide the closest approximation to the actual enzyme activities in vivo. Measurements made in this way effectively explained the majority of the changes in the soleus glycogen content during recovery from nonweight bearing.
Control of extrathoracic airway dynamics
Authors: Schultz E. L. , Horvath S. M.
Published: December 2017

The ventilatory controlling factors associated with oral augmentation of nasal breathing were investigated in 25 (14 women, 11 men) healthy adults during an incrementally graded bicycle exercise test. Ventilatory variables were measured by separate oral and nasal pneumotachometers integrated with a valveless oral-nasal face mask and a flexible oral catheter. Inspired and expired breath length, nasal flows, nasal ventilation, transnasal pressures, nasal work of breathing, nasal powers, and nasal resistances were measured simultaneously on a breath-by-breath basis and averaged over the 30-s interval before oral augmentation. Subjects participated in a minimum of two separate tests, with statistical analysis focusing on the correlation obtained for nasal work of breathing (r = 0.870), nasal average power (r = 0.838), and average transnasal pressure (r = 0.819) during inspiration and for average nasal power (r = 0.801) during expiration indicates that these variables were the most reliable predictors of the oral augmentation of nasal breathing.
Effect of sleep on nocturnal bronchoconstriction and ventilatory patterns in asthmatics
Authors: Ballard R. D. , Saathoff M. C. , Patel D. K. , Kelly P. L. , Martin R. J.
Published: December 2017

To assess the effect of sleep on airflow resistance and patterns of ventilation in asthmatic patients with nocturnal worsening, 10 adult subjects (6 asthmatic patients with nocturnal worsening, 4 normal controls) were monitored overnight in the sleep laboratory on two separate occasions. During 1 night, subjects were allowed to sleep normally, whereas during the other night all sleep was prevented. The six asthmatic patients demonstrated progressive increases in lower airway resistance (Rla) on both nights, but the rate of increase was twofold greater (P less than 0.0001) during the sleep night compared with the sleep prevention night. However, overnight decrements in forced expired volume in 1 s (FEV1) were similar over the 2 nights. The asthmatic patients maintained their minute ventilation as Rla increased during sleep, demonstrating a stable tidal volume with a mild increase in respiratory frequency. We conclude that in asthmatic patients with nocturnal worsening 1) Rla increases and FEV1 falls overnight regardless of sleep state, 2) sleep enhances the observed overnight increases in Rla, and 3) sleep does not abolish compensatory ventilatory responses to spontaneously occurring bronchoconstriction.
Ventilatory response to rowing and cycling in elite oarswomen
Authors: Szal S. E. , Schoene R. B.
Published: December 2017

Rowing is a unique exercise for humans, and the imposed biomechanical motion may alter both respiratory mechanics and timing. To investigate the ventilatory patterns of competitive rowers while rowing, we studied the pulmonary function of eight members of the University of Washington Women's Crew and one former member of the 1984 Women's Olympic Rowing Team on a rowing ergometer. Ventilatory performance of the oarswomen was compared both with their performance to exhaustion on a cycle ergometer and with the ventilatory response of six untrained controls on a rowing and a cycle ergometer. We found rowing elicited a higher ventilatory response in both the oarswomen and controls in submaximal and maximal work loads (P less than 0.001). Both oarswomen and controls had higher maximal breathing frequencies when rowing compared with cycling [rowers, 54.7 +/- 1.9 vs 49.8 +/- 0.09 (SE) breaths/min, P less than 0.05; and controls, 53.6 +/- 2.5 vs. 49.2 +/- 4.7, P less than 0.05] and lower maximal tidal volumes (rowers, 1.94 +/- 0.12 vs. 2.21 +/- 0.09 liters, P less than 0.01; controls, 1.59 +/- 0.09 vs. 1.68 +/- 0.19, difference not significant). Both oarswomen and controls were more hypocapnic while rowing compared with cycling (rowers, P less than 0.001; controls, P less than 0.02), although oarswomen were less hypocapnic while rowing than nonrowers (P less than 0.03). These results indicate that rowing causes hyperventilation with a higher breathing frequency and lower tidal volume. This alteration of pattern is possibly secondary to a change in mechanics, which possibly arises from the generation of high exercise ventilation in a variable seated position.
O2- and pneumonia-induced lung injury. I. Pathological and morphometric studies
Authors: Coalson J. J. , King R. J. , Winter V. T. , Prihoda T. J. , Anzueto A. R. , Peters J. I. , Johanson W. G.
Published: December 2017

The physiological, morphological, and morphometric findings of several lung injury models in baboons have been compared in the following six study groups: 1) initial injury with oleic acid followed by ventilation with 100% O2, 2) ventilation with 100% O2, 3) ventilation with 80% O2, 4) ventilation with 80% O2 followed by inoculation of Pseudomonas aeruginosa, 5) ventilation with 40% O2, and 6) normal nonventilated room-air-breathing animals. The animals were maintained for 11 days in an intensive care unit. Light microscopically, animals ventilated with 40 and 80% O2 showed mild lung injury, consisting mostly of an increase in alveolar macrophages in peribronchiolar sites and focal alveolar wall widening. The 100% O2-oleic acid, 100% O2, and 80% O2-Pseudomonas-treated baboons showed mixed exudative-reparative diffuse alveolar lesions. Ultrastructurally, the type II cells of these three groups had significantly altered morphology with aberrations of lamellar body configurations. Morphometric findings showed increases in type II and interstitial cells and decreases in type I and endothelial cells in these injured animals. A striking finding was that the physiological, morphological, and morphometric changes of an 80% O2-Pseudomonas insult was as injurious as 100% O2. This synergistic effect of hyperoxia and infection very likely reflects the most frequent evolution of adult respiratory distress syndrome in patients in intensive care units.
Effects of temperature and composition on the viscosity of respiratory gases
Authors: Turner M. J. , MacLeod I. M. , Rothberg A. D.
Published: December 2017

The steady-state sensitivity of resistance pneumotachographs is proportional to viscosity. Dynamic characteristics of pneumotachographs, pressure transducers, and mass spectrometers are also viscosity dependent. We derive linear equations to approximate the viscosities of O2, N2, CO2, H2O, He, N2O, and Ar for temperatures between 20 and 40 degrees C by using published viscosity data and a nonlinear extrapolation equation. We verify the accuracy of the extrapolation equation by comparison with published data. Our linear equations for pure gas viscosities yield standard errors less than 0.35 microP. We also compare a nonlinear equation for calculating the viscosities of mixtures of gases with published measured viscosities of dry air, humid air, and He-O2 and N2-CO2 mixtures. The maximum difference between published and calculated values is 1.3% for 10% CO2 in N2. All other differences are less than 0.38%. For saturated humid air at 35 degrees C, a linear concentration-weighted combination of viscosities differs from our nonlinear equation by 4.9, 2.1, and 1.7% at barometric pressures of 32, 83, and 100 kPa, respectively. By use of our method, the viscosity of normal respiratory gases can be calculated to within 1% of measured values.
Effect of osmolality on availability of glucose ingested during prolonged exercise in humans
Authors: Jandrain B. J. , Pirnay F. , Lacroix M. , Mosora F. , Scheen A. J. , Lefebvre P. J.
Published: December 2017

The aim of this study was to investigate whether the osmolality of a glucose solution, ingested at the beginning of a prolonged exercise bout, affects exogenous glucose disposal. We investigated the hormonal and metabolic response to a 50-g glucose load dissolved in either 200 (protocol A), 400 (protocol B), or 600 (protocol C) ml of water and given orally 15 min after adaptation to exercise in five healthy male volunteers. Naturally labeled [13C]glucose was used to follow the conversion of the ingested glucose to expired-air CO2. Total carbohydrate oxidation (indirect calorimetry) was similar in the three protocols (A, 237 +/- 20; B, 258 +/- 17; C, 276 +/- 20 g/4 h), as was lipid oxidation (A, 128 +/- 4; B, 132 +/- 15; C, 124 +/- 12 g/4 h). Exogenous glucose oxidation rates were similar under the three experimental conditions, and the total amount of exogenous glucose utilized was slightly, but not significantly, increased with the more diluted solution (A, 42.6 +/- 4.4; B, 43.4 +/- 4.1; C, 48.7 +/- 7.2 g/4 h). The blood glucose response was similar in the three protocols. Thus, within the range investigated, the osmolality of the glucose solution ingested had no significant influence either on its oxidation (which was 86–98% of the load ingested) or on the utilization of endogenous carbohydrate, lipid, or protein stores.
Lack of alveolar O2 during lung reperfusion does not decrease edema formation
Authors: Overand P. T. , Bishop M. J. , Eisenstein B. L. , Chi E. Y. , Su M. , Cheney F. W.
Published: December 2017

We previously reported that pulmonary arterial occlusion for 48 h followed by 4 h of reperfusion in awake dogs results in marked edema and inflammatory infiltrates in both reperfused and contralateral lungs (Am. Rev. Respir. Dis. 134: 752–756, 1986; J. Appl. Physiol. 63: 942–950, 1987). In this experiment we study the effects of alveolar hypoxia on this injury. Anesthetized dogs underwent thoracotomy and occlusion of the left pulmonary artery. Twenty-four hours later the dogs were reanesthetized, and a double-lumen endotracheal tube was placed. The right lung was continuously ventilated with an inspiratory O2 fraction (FIO2) of 0.35. In seven study animals the left lung was ventilated with an FIO2 of 0 for 3 h after the left pulmonary artery occluder was removed. In six control animals the left lung was ventilated with an FIO2 of 0.35 during the same reperfusion period. Postmortem bloodless wet-to-dry weight ratios were 5.87 +/- 0.20 for the left lower lobe and 5.32 +/- 0.12 for the right lower lobe in the dogs with hypoxic ventilation (P less than 0.05 for right vs. left lobes). These values were not significantly different from the control dog lung values of 5.94 +/- 0.22 for the left lower lobe and 5.11 +/- 0.07 for the right lower lobe (P less than 0.05 for right vs. left lobes). All values were significantly higher than our laboratory normal of 4.71 +/- 0.06. We conclude that reperfusion injury is unaffected by alveolar hypoxia during the reperfusion phase.
Influence of work rate on ventilatory and gas exchange kinetics
Authors: Casaburi R. , Barstow T. J. , Robinson T. , Wasserman K.
Published: December 2017

A linear system has the property that the kinetics of response do not depend on the stimulus amplitude. We sought to determine whether the responses of O2 uptake (VO2), CO2 output (VCO2), and ventilation (VE) in the transition between loadless pedaling and higher work rates are linear in this respect. Four healthy subjects performed a total of 158 cycle ergometer tests in which 10 min of exercise followed unloaded pedaling. Each subject performed three to nine tests at each of seven work rates, spaced evenly below the maximum the subject could sustain. VO2, VCO2, and VE were measured breath by breath, and studies at the same work rate were time aligned and averaged. Computerized nonlinear regression techniques were used to fit a single exponential and two more complex expressions to each response time course. End-exercise blood lactate was determined at each work rate. Both VE and VO2 kinetics were markedly slower at work rates associated with sustained blood lactate elevations. A tendency was also detected for VO2 (but not VE) kinetics to be slower as work rate increased for exercise intensities not associated with lactic acidosis (P less than 0.01). VO2 kinetics at high work rates were well characterized by the addition of a slower exponential component to the faster component, which was seen at lower work rates. In contrast, VCO2 kinetics did not slow at the higher exercise intensities; this may be the result of the coincident influence of several sources of CO2 related to lactic acidosis. These findings provide guidance for interpretation of ventilatory and gas exchange kinetics.
Effects of a draft-loaded interval-training program on skeletal muscle in the horse
Authors: Gottlieb M. , Essen-Gustavsson B. , Lindholm A. , Persson S. G.
Published: December 2017

Five Standardbred trotters were trained on a treadmill 3 times/wk for 12 wk by intervals of draft-loaded exercise. The draft load was 34 kp and the velocity approximately 7 m/s. Muscle biopsies were taken from the gluteus medius and longissimus muscles before training and after 2, 4, 8, and 12 wk of training and from the brachiocephalicus muscle before and after training. Both the percentage and the area of type IIa fibers increased and the percentage of type IIb fibers decreased in the gluteus medius muscle during the first 2 wk of training, and then no further significant difference was noted. The percentage of type I fibers increased in the brachiocephalicus muscle, and the area of type IIb fibers increased in the longissimus muscle. The citrate synthase activity increased in the gluteus muscle only, and the increase was seen during the first 2 wk. No significant differences were seen in 3-hydroxy-acyl-CoA dehydrogenase and lactate dehydrogenase activities in the muscles during the entire training period. Less glycogen was utilized in the gluteus muscle and less blood lactate accumulated when the horses performed an unloaded submaximal exercise test after compared with before training. It can be concluded that rapid changes are induced in the gluteus medius muscle when horses are trained pulling a light-draft resistance at a submaximal trotting speed.
Histochemical characteristics of human expiratory and inspiratory intercostal muscles
Authors: Mizuno M. , Secher N. H.
Published: December 2017

The relative occurrence of slow-twitch (ST) and fast-twitch (FTa and FTb) fibers, fiber size, and capillary supply in internal (INT) and external intercostal muscles (EXT), the costal diaphragm (DIA), and vastus lateralis muscle (VAS) was examined post-mortem in eight healthy males. The relative occurrence of ST fibers in INT [64 +/- 3% (SE)] and EXT (62 +/- 3%) was similar but higher than in DIA (49 +/- 3%) and VAS (40 +/- 6%; P less than 0.05). The occurrence of FTa fibers in expiratory INT (35 +/- 3%) was higher than in inspiratory INT and EXT (17 +/- 1%; P less than 0.05) but similar to DIA (28 +/- 6%) and VAS (32 +/- 2%). Accordingly, expiratory INT had fewer FTb fibers (1 +/- 1%) than the others (P less than 0.05). Expiratory INT had a 60% larger fiber area than inspiratory INT and EXT and DIA (P less than 0.05), but the area was similar to that of VAS. The number of capillaries per fiber was higher in expiratory INT (2.3 +/- 0.1) than in inspiratory INT and EXT (1.6 +/- 0.1), DIA (1.9 +/- 0.1), and VAS (1.8 +/- 0.2; P less than 0.05). The results suggest that the occurrence of many large capillary-rich FTa fibers in expiratory INT is bound to function (expiratory vs. inspiratory) rather than to anatomy (INT vs. EXT).
Menstrual status and plasma vasopressin, renin activity, and aldosterone exercise responses
Authors: De Souza M. J. , Maresh C. M. , Maguire M. S. , Kraemer W. J. , Flora-Ginter G. , Goetz K. L.
Published: December 2017

The effects of menstrual cycle phase (early follicular vs. midluteal) and menstrual status (eumenorrhea vs. amenorrhea) on plasma arginine vasopressin (AVP), renin activity (PRA), and aldosterone (ALDO) were studied before and after 40 min of submaximal running (80% maximal O2 uptake). Eumenorrheic runners were studied in the early follicular and midluteal phases determined by urinary luteinizing hormone and progesterone and plasma estradiol and progesterone assays; amenorrheic runners were studied once. Menstrual phase was associated with no significant differences in preexercise plasma AVP or PRA, but ALDO levels were significantly higher during the midluteal phase than the early follicular phase. Plasma AVP and PRA were significantly elevated at 4 min after the 40-min run in the eumenorrheic runners during both menstrual phases and returned to preexercise levels by 40 min after exercise. Plasma ALDO responses at 4 and 40 min after exercise were higher in the midluteal phase than the early follicular phase. Menstrual status was associated with no significant differences in preexercise AVP or PRA; however, ALDO levels were significantly higher in the amenorrheic runners. After exercise, responses in the amenorrheic runners were comparable with the eumenorrheic runners during the early follicular phase. Thus, submaximal exercise elicits significant increases in plasma AVP and PRA independent of menstrual phase and status. However, plasma ALDO is significantly elevated during the midluteal phase, exercise results in a greater response during this menstrual phase, and amenorrheic runners have elevated resting levels of ALDO.
Combination of constant-flow and continuous positive-pressure ventilation in canine pulmonary edema
Authors: Sznajder J. I. , Becker C. J. , Crawford G. P. , Wood L. D.
Published: December 2017

Constant-flow ventilation (CFV) maintains alveolar ventilation without tidal excursion in dogs with normal lungs, but this ventilatory mode requires high CFV and bronchoscopic guidance for effective subcarinal placement of two inflow catheters. We designed a circuit that combines CFV with continuous positive-pressure ventilation (CPPV; CFV-CPPV), which negates the need for bronchoscopic positioning of CFV cannula, and tested this system in seven dogs having oleic acid-induced pulmonary edema. Addition of positive end-expiratory pressure (PEEP, 10 cmH2O) reduced venous admixture from 44 +/- 17 to 10.4 +/- 5.4% and kept arterial CO2 tension (PaCO2) normal. With the innovative CFV-CPPV circuit at the same PEEP and respiratory rate (RR), we were able to reduce tidal volume (VT) from 437 +/- 28 to 184 +/- 18 ml (P less than 0.001) and elastic end-inspiratory pressures (PEI) from 25.6 +/- 4.6 to 17.7 +/- 2.8 cmH2O (P less than 0.001) without adverse effects on cardiac output or pulmonary exchange of O2 or CO2; indeed, PaCO2 remained at 35 +/- 4 Torr even though CFV was delivered above the carina and at lower (1.6 l.kg-1.min-1) flows than usually required to maintain eucapnia during CFV alone. At the same PEEP and RR, reduction of VT in the CPPV mode without CFV resulted in CO2 retention (PaCO2 59 +/- 8 Torr). We conclude that CFV-CPPV allows CFV to effectively mix alveolar and dead spaces by a small bulk flow bypassing the zone of increased resistance to gas mixing, thereby allowing reduction of the CFV rate, VT, and PEI for adequate gas exchange.