The influence of hypoxaemia on anaerobic energy production during arm exercise (AE) has been investigated. Six men were studied during maximal AE and during 10 min of sitting submaximal AE under both normoxic (AEN) and hypoxic (AEH, respiratory hypoxia, 12% O2) conditions. Peak pulmonary oxygen uptake (VO2) during maximal AE ...

Eight male subjects were examined for the transition from anaerobic to aerobic energy supplies during supramaximal pedalling for 120 s on a cycle ergometer. The O2 debt and O2 deficit were measured for anaerobic supply, while O2 intake during exercise was measured for aerobic supply. The lactic acid system was ...

Exercise-induced hypoxaemia (EIH) has been associated with an oxygen diffusion limitation. Because polyunsaturated fatty acids (PUFA) administration can modify cell membrane fluidity, we hypothesized that the importance of EIH could be reduced after a 6-week PUFA diet. Resting pulmonary functions and a maximal cycling test were performed before and after ...

We examined the effects of the alpha-adrenergic blocking agent urapidil on coronary blood flow (CBF) and myocardial O2 consumption during exercise in 11 dogs trained to run on a motor-driven treadmill. Left circumflex coronary artery (LCX) BF was measured with an electromagnetic flowmeter, and aortic and coronary sinus electromagnetic flowmeter, ...

We examined whether arterial hypoxemia impairs incremental exercise performance in subjects with interstitial lung disease (ILD). Seven subjects underwent two incremental exercise tests on a bicycle ergometer in random order; one while breathing room air (RA), and the other while breathing 60% O2. Maximal exercise performance was impaired in all ...

Marsupials have lower resting metabolic rates than placental mammals, but it is not clear whether particular species can extend this energetic advantage to locomotion. Some active marsupials have a low cost of locomotion, but other more sedentary species, such as the Virginia opossum, appear to run very inefficiently. Steady-state rates ...

To examine whether the tip of the femoral vein catheter used for sampling femoral venous PO2 during cycling exercise is contaminated by skin or saphenous vein blood, we studied 6 healthy volunteers [21.7 +/- 0.7 (SD) yr] during three identical incremental exercise tests while breathing room air on the same ...

Birds are unique since they can combine a high rate of oxygen consumption at rest with a high maximum life span (MLSP). The reasons for this capacity are unknown. A similar situation is present in primates including humans which show MLSPs higher than predicted from their rates of O2 consumption. ...

In five subjects we examined the effect of exercise on the pattern of central venous (right atrial) N2 tensions (PVN2) after ascent from simulated non-decompression dives. The dives consisted of exposure to air at 3 bar for 20 min with 10 min of exercise (workload 75 W) at depth to ...

An analogy is drawn between cytochrome aa3 function and a polarographic cathode at which the potential of -0.6 V captures all O2 diffusing to the surface, achieving maximal O2 consumption (VO2max) by eliminating O2 backpressure and outward diffusion from the surface, defined herein as zero surface PO2. The relationship of ...

We assessed the inspiratory to end-tidal oxygen difference (PIO2-PE'O2) during voluntary hyperventilation in 10 healthy male volunteers. The oxygen difference was measured with a fast-response paramagnetic differential oxygen sensor. As simultaneous changes in metabolism and cardiac output also influence (PIO2-PE'O2), oxygen uptake was measured with indirect calorimetry and non-invasive transthoracic ...

When tissue O2 delivery falls below a critical threshold, tissue O2 uptake (VO2) becomes limited. We compared critical O2 delivery and critical and maximum O2 extraction ratios of the resting and contracting left hemidiaphragm with those of nondiaphragmatic tissues in seven dogs. The left hemidiaphragm was perfused through the left ...

The association of oxygen radical generation with impaired diaphragm performance has previously been reported after inspiratory resistive loading (IRL). We hypothesized that exposure of rats to normobaric hyperoxia (O2) could produce impaired diaphragm function because of free radical production. Sprague-Dawley rats were divided into four groups: 1) room air (control), ...

When at sea, phocids dive for long periods and spend a high percentage of their time submerged. This behaviour requires some combination of an increased oxygen storage capacity, rapid oxygen loading at the surface and reduced oxygen utilisation when submerged. To assess these adaptations, breath-by-breath ventilation was studied in four ...

Professional diving fishermen in the Pescadores Archipelago (119.30 degrees W, 23.30 degrees N) dive with a simple hookah system. Although they use modern equipment, such as wet suit, face mask, mouth piece with demand valve, spear gun, weight belt, and fins, their lack of knowledge of diving medicine is apparent. ...

The aim of this study was to examine the influence of water immersion to the chest on cardio-vascular adaptation to exercise. Upright or sitting immersion causes an increase in central blood volume, but it remains controversial whether central blood volume remains elevated during dynamic exercise in water and facilitates cardiac ...

OBJECTIVE: Investigation of the hypothesis that the infusion of 10 ng/kg/min prostacyclin (epoprostenol) (PGI2) improves O2 uptake in patients with hyperdynamic septic shock. DESIGN: Prospective, single cohort design. SETTING: ICU, university hospital. PATIENTS: Fifteen postoperative patients with septic shock. INTERVENTIONS: Infusion of 10 ng/kg/min of PGI2 for 60 min. MEASUREMENTS: ...

Anesthetized, paralyzed and mechanically ventilated pigs were hypoventilated to extreme hypercapnia (PaCO2 approximately 20 kPa) at FiO2 0.5, and allotted to receive hypothermia (approximately 31.5 degrees C) and buffer infusion, (HB-group, n = 6) or to a hypothermic control group (H-group, n = 6). The HB-group had higher arterial pH ...

To determine the effects of varying inspired O2 on positive radial acceleration (+Gz; i.e., head-to-foot inertial load) duration tolerance, seven men were exposed to the +4.5- to +7.0-Gz simulated aerial combat maneuver (SACM) by use of the Armstrong Laboratory (Brooks Air Force Base) centrifuge. Exposures were repeated on different days ...

This study examined the relationship of oxygen pulse (O2 pulse) to stroke volume (SV) and arterio-venous oxygen difference [(a-v)O2 diff] during submaximal cycle exercise in untrained (UG) and trained (TG) males. Fourteen volunteers in each group completed an incremental VO2 max test and a submaximal test at 60% VO2 max ...

Despite apparently depressed function, stunned myocardium maintains oxygen consumption and has the capacity to increase contractility with inotropic stimulation. We hypothesized that during stunning, O2 demand is maintained because regional segment work is performed, but is asynchronous with global left ventricular contraction, and that inotropic stimulation would restore regional work ...

Our question was whether inhibition of nitric oxide [endothelium-derived relaxing factor (EDRF)/NO] production in an in situ vascularly isolated but innervated canine hindlimb would prevent hypoxic vasodilation or interfere with O2 extraction during ischemic (IH) or hypoxic hypoxia (HH). After a control period, we gave NG-nitro-L-arginine methyl ester (L-NAME, 20 ...

The hemodynamic alterations in elderly individuals when combined with their reduced functional capacity concerning specific organ systems places them at an increased risk of developing shock with certain disease processes. The initial management should be directed toward shock resuscitation with appropriate volume and/or vasopressor/inotropic support. Then attention must be given ...

Exhaustive dynamic exercise with large muscle groups in chronic hypobaric hypoxia may be limited by central (nervous) rather than peripheral (metabolic) fatigue. Six males [32 +/- 4 (SD) yr] at sea level (SL) and after 1-mo acclimatization at 5,050 m (HA) performed exhaustive dynamic forearm exercise at a constant absolute ...

To test the influence of arterial O2 saturation (SaO2) on heart rate in cluster headache, changes in pulse rate induced by hyperoxia and hypoxia were monitored in 11 cluster headache patients (6 during cluster period, and 5 during remission). The results were compared with those obtained in 11 age and ...

The cardiovascular system has frequently been hypothesized to be the limiting step for O2 transport that determines VO2 max in many species of mammals. Careful analysis of the factors that determine how O2 is transported by the circulation demonstrate that such a single-step limitation cannot exist. Evaluation of the results ...

These data indicate that through the reduction in exercise time and recruitment of trained subjects, the exercising muscle in the human dynamic knee-extension model can reach even higher work rates, VO2, and Q than previously reported (Andersen & Saltin, 1985; Andersen et al., 1985; Rowell et al., 1986). Despite these ...

Physiological roles of ventilatory responses to acute hypoxia in the regulation of O2 transport and consumption were evaluated quantitatively in halothane anesthetized and spontaneously breathing rats with or without peripheral chemoreceptor afferents. Ventilation (VE), blood gas values, cardiac output (Q), and whole-body O2 consumption (VO2) were measured at various levels ...

To determine whether exercise induces hypoxemia in highly trained older "master" athletes (MA), as it does in certain elite endurance-trained young athletes (YA), 10 MA (65.3 +/- 2.6 yr), 10 control subjects (CS; 68.3 +/- 2.2 yr), and 10 endurance-trained YA (23.3 +/- 1.1 yr) performed an incremental exercise test. ...

We studied O2 transport in the leg to determine if hyperoxia will increase the maximal rate of O2 uptake (VO2max) in exercising muscle. An increase in inspired O2 fraction (FIO2) from 0.21 to 1.00 was postulated to have the following effects: 1) increase the leg VO2max by approximately 5-10%, 2) ...

The objective of this study was to examine the possible involvement of oxygen free radicals in the aging process. Rates of mitochondrial O2.- and H2O2 production and oxygen consumption in the kidney and the heart were compared among seven different mammalian species namely, mouse, hamster, rat, guinea pig, rabbit, pig, ...

We previously reported that O2 diffusion was limited in piglets. To test the hypothesis of an inadequacy between diffusion and perfusion in piglets (< 4 wk) vs. older pigs (> 8 wk), we compared in these two age groups the effect of an increase (by opening an arteriovenous fistula) or ...

Inspiratory muscle fatigue, a common event in patients in the intensive care unit, is under multifactorial control. To test the hypothesis that systemic oxygenation is a factor in this event, we subjected five healthy males (age 42 +/- 3 yr) to continuous inspiratory pressure (75% of maximal inspiratory pressure, -95 ...

We wished to assess whether the previously developed 3,3'-diaminobenzidine (DAB)-Mn++ cytochemical method, purportedly specific for superoxide localization, is detecting superoxide O2.- and/or the superoxide product, O2(1 delta g). We show here that polymorphonuclear leukocytes (PMNs) produce O2(1 delta g) extracellularly in response to non-phagocytic stimuli and that this production is ...

Oxygen tension was measured using flexible polarographic microelectrodes within the oviductal and uterine lumen in rhesus monkeys (n = 9), golden hamsters (n = 21) and rabbits (n = 6), during the reproductive cycle (monkey), during oestrus and pseudopregnancy (hamsters, rabbits) and during pregnancy (hamsters). In general, oxygen tensions in ...

During conventional cycle ergometry, as work rate (WR) is increased toward maximum, O2 extraction increases hyperbolically, typically achieving values of 80-90% at peak O2 uptake (VO2). In contrast, studies using isolated knee-extensor exercise report much higher mass-specific blood flows (Q) and lower maximal O2 extractions (approximately 70%), which have been ...

Breath-by-breath gas exchange was studied in 10 subjects during and after transitions between dry conditions and head-out immersion in thermoneutral conditions. Cardiac index (CI) was estimated by means of impedance cardiography. Previous largely qualitative models of changes in tissue gas stores after blood volume shifts could be confirmed and extended ...

Maximum oxygen uptake (VO2max) is affected by hemoglobin concentration ([Hb]). Whether this is simply due to altered convection of O2 into the muscle microcirculation or also to [Hb]-dependent diffusive transport of O2 out of the muscle capillary is unknown in humans. To examine this, seven healthy volunteers performed four maximal ...

Eleven end-stage renal disease patients trained by stationary cycling during their hemodialysis treatments. After a 6-week control period, 12 weeks of training began and was increased to 30 to 60 minutes at > or = 70% of peak heart rate. Baseline, pretraining and, posttraining exercise tests were performed. Workload (WL), ...

The stratum corneum, the outer 10 microns of the skin, serves as a permeability barrier regulating the transport of molecules between the body and the environment. The purpose of this study is to understand this permeability barrier function as it pertains to the diffusion of molecular oxygen. The stratum corneum ...

The efficiency of the vascular-tissue system in mammals for oxygen (O2) transport to tissue was evaluated by employing the following simulation models; (i) the spherical tissue model for assessing the maximum tissue mass for which a certain number of capillaries located in the center of each sphere can deliver sufficient ...

While wearing a self-contained breathing apparatus and fire-protective clothing, 35 healthy firefighting students aged 19-27 years performed smoke-diving (entry into a smoke-filled room) during a simulated shipboard fire. The mean (+/- SD) ambient temperature inside the simulator was 119 +/- 12 degrees C, and the task lasted 17 +/- 4 ...

The purpose of this work was to study the seasonal salivary cortisol and testosterone changes, and their relationships with lean body mass variations, in highly trained cyclists. Physical fitness, body composition (6 skinfolds) and basal salivary testosterone were evaluated in 7 male cyclists, on two separate occasions. The first assessment ...

Tissue O2 partial pressure (PtiO2) and O2 disappearance rates (dPO2/dt) after bilateral carotid artery occlusion were measured with recessed cathode O2 microelectrodes (tips < 3 microns) in gerbil brains (n = 38) from three age groups: young (Y, 3-6 mo), mature (M, 10-12 mo), and older (O, 18-21 mo). Mean ...

To investigate the effects of exercise training and immobilization on peak O2 uptake (VO2) and effective O2 diffusive conductance (DO2) in skeletal muscle, three groups of purpose-bred hounds [control (C), exercise trained (E), and immobilized (I)] were studied. Group E exercised on a treadmill 1 h/day, 5 days/wk for 8 ...

Almitrine, a peripheral chemoreceptor agonist, has been reported to increase arterial O2 saturation (SaO2) without changing minute ventilation (VE) during hypoxic exercise (Giesbrecht et al. J. Appl. Physiol. 70: 1770-1774, 1991). To explain this finding, we studied pulmonary hemodynamics (right heart catheterization) and gas exchange (multiple inert gas elimination technique) ...

We evaluated the effect of graded exercise on esophageal motility and gastroesophageal reflux. We studied eight trained cyclists using a catheter with three strain-gauge transducers connected to a solid-state datalogger and an ambulatory intraesophageal pH monitor. Each study lasted 4 hr during which subjects exercised on a stationary bike for ...

To establish safe levels for physical strain in occupational repetitive lifting, it is of interest to know the specific maximal working capacity. Power output, O2 consumption, heart rate and ventilation were measured in ten experienced forestry workers during maximal squat and stoop repetitive lifting. The two modes of repetitive lifting ...

The effects of short and long duration exercise on serum erythropoietin concentrations [EPO]s were studied in seven male cross-country skiers of national team standard and eight male marathon runners, respectively. The short duration exercise was performed as 60 min of cycling at an intensity of 80%-95% of maximal heart rate. ...

Brain cortex PO2 was measured after craniotomy and opening of the dura mater in 26 patients. We determined the brain tissue PO2 under standard narcotic conditions and after changing arterial PO2 and PCO2. Patients were divided into two groups (normal and pathological), depending on the aspect of their cortex on ...