Oxygen Extraction Efficiency Research Articles

Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus).

The effects of different ambient temperatures (Ta) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m). At both low and high altitude, oxygen consumption (VO2) decreased with increasing Ta at Ta from -10 to 30 degrees C. The VO2 was 15-20% smaller at high altitude than at low altitude at Ta below 30 degrees C. Increased VO2 at Ta below thermoneutrality was supported by increased minute volume (VI) at both low and high altitude. At most Ta, the change in VI was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (VT) or oxygen extraction efficiency (O2EE). At Ta = 0 degree C and below at high altitude, VI was constant due to declining VT and O2EE increased in order to maintain high VO2. At high altitude, VI (BTP) was 30-40% higher at a given Ta than at low altitude, except at Ta below 10 degrees C. The increased VI at high altitude was due primarily to a proportional increase in f, which attained mean values of 450-500 breaths/min at Ta below 0 degree C. The VI (STP) was equivalent at high and low altitude at Ta of 10 degrees C and above. At lower Ta, VI (STPD) was larger at low altitude. At both altitudes, respiratory heat loss was a small fraction (less than 10%) of metabolic heat production, except at high Ta (20-30 degrees C).

Effects of hypoxia on the respiratory and circulatory regulation of Nephrops norvegicus

The burrowing decapod Nephrops norvegicus (L.) was kept under various degrees of hypoxia in order to measure respiration, heart rate, scaphognathite rate, haemolymph oxygen content and pH. An emergence reaction to hypoxia occurred only in dim light (<10-2 m-c) or darkness, but after 10 d of moderate hypoxia the decapods showed no emergence response at all. The weight specific respiration of quiescent individuals was relatively low and increased only slightly in hypoxia (PwO2=40 torr). Heart rate, about 50 beats min-1, changed little during hypoxia, down to PwO2=40 torr, whereas scaphognathite rates rose from about 60 beats min-1 at normoxia to peak at 120 beats min-1 at PwO2=40 torr. The oxygen extraction efficiency (E) remained at 20 to 30% during the first hour of hypoxia then rose gradually to maximum values of 30 to 40%. A small respiratory alkalosis of the blood became evident only after 4h of hypoxia (PwO2=50 torr). Normoxic postbranchial O2 tensions (PaO2) were low (25–30 torr) and showed only a small decline during hypoxia. Over 10 to 13 d in moderate hypoxia an effective biosynthesis of 0.024 mM haemocyanin individual-1 d-1 occurred in fed decapods, whereas controls (normoxic) showed no significant change in pigment levels. A linear relationship between oxygen carrying capacity and haemocyanin concentration was found. It is contended that N. norvegicus is better able to cope with periodic exposure to hypoxia when food of sufficient quantity and quality is available.

Antarctic Fish Blood: Respiratory Properties and the Effects Of Thermal Acclimation

ABSTRACT The effects of thermal acclimation on whole blood oxygen affinity were examined in the antarctic fish Pagothenia borchgrevinki. 4·5 °C-acclimated fish had a P50 value of 26·7 mmHg at pH 8·4, compared to 20·7 mmHg for −1·5 °C-acclimated fish. The apparent heat of oxygenation, ΔH = −26·7 kJ mol−1, is comparable to values for temperate species. Warm-acclimation was followed by an increased ATP:Hb4 molar ratio, resulting in an augmentation of the thermal effect on oxy-haemoglobin affinity. This may be considered adaptive in a constantly well oxygenated environment, where oxygen loading at the gills is secured. Unloading to the tissues is thereby enhanced, supporting an elevated rate of aerobic metabolism at higher temperatures. In vivo blood pH was high, between 8·10 and 8·25 at − 1·5 °C. Astrup titration revealed arterial CO2 tensions of less than 0·8 mmHg, indicating relative hyperventilation and low oxygen extraction efficiency in antarctic fish. Blood oxygen affinities of four antarctic nototheniid species were low (P50 between 11·9 and 20·7 mmHg at pH 8·1 and -1·5 °C) in comparison with the temperate speciesNotothenia angustata (P50 = 10·8 mmHg). The zoarcid Rhigophila dearbomi had a high blood oxygen affinity (P50 = 4·3 mmHg). Blood oxygen-binding properties are discussed in relation to the polar environment, mode of life, and the concept of cold adaptation.

Oxygen consumption, ventilation and respiratory heat loss in a parrot,Bolborhynchus lineola, in relation to ambient temperature

1. Bolborhynchus lineola, a parrot of the humid tropics, has an unusually narrow thermoneutral zone (TNZ) (28–30 °C) and a total (wet) conductance 40% greater than predicted based upon its mass. 2. Within thermal neutrality mean tidal volume was 1.22 ml/breath and respiratory frequency was 28.6 breaths/min. These values are, respectively, 2.11 and 0.68 times allometrically predicted values (Lasiewski 1972). The mean rate of oxygen consumption in the TNZ during simultaneous measurement of other respiratory parameters was 1.87 ml O2/min and mean inspiratory minute volume equaled 34.3 ml/min (1.12 times the predicted value). 3. Mean oxygen extraction efficiency in the TNZ was 27.2%, 1.25 times the predicted value for a nonpasserine bird of 55.7 g and 1.66 times the predicted value for a similarly sized mammal. Maximum extraction efficiencies were about 53% at 27 °C and the highest mean value, 40.0%, was measured at that temperature. Mean oxygen extraction efficiency at allTa's belowTlc were higher than within TNZ or above it. 4. Total respiratory heat loss accounted for 9% of total heat production atTlc and only 3% of total heat production at 5 °C. Elevated oxygen extraction efficiencies belowTlc help to reduce respiratory heat loss. 5. Normal respiratory responses of resting birds to changes in ambient conditions can best be measured in totally unrestrained animals because respiratory frequency and oxygen consumption, and therefore oxygen extraction efficiency, are very labile and any disturbance masks normal responses.

Alpha-Stimulation protects exercise increment in skeletal muscle oxygen consumption.

Oxygen consumption (VO2) in an isolated, autoperfused, statically exercising canine gracilis muscle (2.5% P0) was studied in low blood flow (Q) states induced by constant norepinephrine (NE) infusion and by mechanical occlusion (MO). Q and VO2 were evaluated at rest (Qc and VO2c), after 5 min of exercise (Qe and VO2e) and after 5 more min of exercise with either NE or MO (Qt and VO2t). Data were normalized and plotted as the VO2e-VO2t)/(VO2c-VO2e) vs. (Qe-Qt)/(Qc-Qe) and equations of the lines for NE (y = 0.090x + 0.048) and for MO (y = 0.488x + 0.070) were determined. The slopes of the lines, tested by analysis of covariance, were significantly different (P less than 0.005). These data indicate that when NE reduced Q during exercise, the exercise induced in VO2 was protected to a greater degree than when MO reduced Q under similar conditions. To determine if the effect of NE on VO2 was secondary to a beta-adrenergic-receptor-mediated of skeletal muscle metabolic processes, the experiments were repeated in the presence of beta-blockade with propranolol. In the presence of beta-blockade, the effects of NE on skeletal muscle VO2 were unchanged. It is therefore hypothesized that the mechanism of this effect of NE may be an increase in the efficiency of oxygen extraction resulting from a redistribution of blood flow to more active muscle fiber regions.

Volume changes and oxygen extraction efficiency in the holothurian, Stichopusmollis (Hutton)

1. 1. Measurements of oxygen consumption and respiratory volume changes were made on the holothurian, Stichopus mollis (Hutton). 2. 2. It is concluded that the external body surface and the respira tory-trees are equally important as sites of oxygen uptake. 3. 3. The oxygen extraction efficiency of the respiratory trees of S. Mollis is estimated at 54 per cent at a temperature of 9°C.

Respiratory metabolism in pacifastacus leniusculus (Dana) (crustacea: decapoda) as related to its ecology

Respiratory metabolism in the high-altitude crayfish, Pacifastacus leniusculus from Lake Tahoe (California-Nevada, U.S.A.) was investigated in a series of laboratory experiments. In general, oxygen consumption was found to be directly proportional to size when expressed per individual, and inversely proportional to size when expressed per ash-free gram dry weight per unit time. No significant variations in respiratory rates were observed between males and females. There was little variation in uptake over a temperature range of 5°C to 12.5°C, while the lowest and highest uptake values were observed at 0°C and 15°C respectively. An increase in temperature above 15°C, however, resulted in a decrease in respiratory activity. These results closely correlate with patterns of ventilatory activity, oxygen extraction efficiency, and seasonal feeding and reproductive activity in Pacifastacus as related to the annual temperature profile for their Lake Tahoe habitat.

PULMONARY FUNCTION DURING NOREPINEPHRINE-INDUCED CALORIGENESIS IN COLD-ACCLIMATIZED RATS.

The effects of cold acclimatization on pulmonary function during norepinephrine-induced calorigenesis were studied. Norepinephrine resulted in a marked increase (85%) in the pulmonary minute volume in both the warm- and cold-acclimatized rats. This increase in the warm-acclimatized rats was accomplished entirely by increasing the respiratory rate, whereas in the cold-acclimatized rats, the increase in pulmonary minute volume was achieved for the most part by increasing the tidal volume with a slight increase in respiratory rate. Cold acclimatization was associated with a greater “efficiency of oxygen extraction” before, during, and after the infusion of norepinephrine. pulmonary minute volume; respiratory rate; oxygen extraction Submitted on December 6, 1962

CORONARY CIRCULATION AND GASEOUS METABOLISM OF HUMAN HEART STUDIED BY CORONARY SINUS CATHETERIZATION

Coronary sinus catheterization was performed in 112 human subjects, including thirty-three normal subjects, forty-six patients with cardiac failure, eleven patients with coronary sclerosis, six patients with hypertension, eight patients with anemia, seven patients with hyperthyroidism, and one patient with beri-beri. In these subjects myocardial gaseous metabolism has been investigated, while left ventricular coronary blood flow has been determined in forty-six of them by means of nitrous oxide methode.1. In normal subjects the average oxygen extraction of left ventricular myocardium was 10.5 volumes per cent. The left ventricular coronary blood flow per 100 grams per minute and the left ventricular oxygen consumption per 100 grams per minute averaged 68.5cc and 7.1cc., respectively, and left ventricular myocardial efficiency averaged 29 per cent. The average myocardial RQ was 0.89.2. In patients with cardiac failure due to valvular or hypertensive heart disease, the myocardial oxygen extraction were significantly increased. This was marked when failure was moderate or severe. The coronary blood flow was normal or slightly increased, resulting in the elevated myocardial oxygen consumption and low cardiac efficiency. In moderate or severe failure myocardial RQ was significantly reduced.3. In patients with coronary sclerosis, most of whom had anginal pain on exertion, myocardial oxygen extraction was slightly but significantly increased, while the coronary blood flow was normal at rest, resulting in elevated myocardial oxygen consumption. Myocardial efficiency was slightly decreased but was within normal range.4. In patients with essential hypertension both myocardial oxygen extraction and myocardial efficiency were normal. Further study is necessary, however, because only a few subjects were studied, including cases with slight hypertension.5. In patients with anemia myocardial oxygen extraction was decreased but myocardial oxygen extraction coefficient (Cao2-Cso2)/Cao2 was increased. Coronary blood flow was markedly increased, the ratio of coronary flow/cardiac output being higher than normal value. Myocardial efficiency was normal.5. In patients with hyperthyroidism myocardial oxygen extraction was normal. Coronary blood flow was increased but the ratio of coronary flow/cardiac output was normal. Myocardial efficiency was normal.7. After the administration of digitalis preparation (lanatoside-C or digicorin) in three patients with congestive failure coronary blood flow reduced about 10 per cent, resulting in the decreased left ventricular oxygen consumption and the elevation of cardiac efficiency.8. The effect of exercise, hypoxia and hexamethonium bromide on myocardial gaseous metabolism and coronary hemodynamics were also demonstrated in healthy and diseased heart.