Claude Lenfant

Effect of altitude on oxygen binding by hemoglobin and on organic phosphate levels

The relationship between oxygen dissociation and 2,3-diphosphoglycerate (2,3-DPG) in the red cell has been studied in subjects moving from low to high altitude and vice versa. Within 24 hr following the change in altitude there was a change in hemoglobin affinity for oxygen; this modification therefore represents an important rapid adaptive mechanism to anoxia. A parallel change occurred in the organic phosphate content of the red cell. While this study does not provide direct evidence of a cause-effect relationship, the data strongly suggest that with anoxia, the observed rise in organic phosphate content of the red cell is responsible for increased availability of oxygen to tissues.

Oxygen transport in man.

OXYGEN transport is a corporate process involving several organs, each with its own regulatory system. Individual diseases of the heart, lungs or blood may impair the functional capacity of a singl...

Gas transport and oxygen storage capacity in some pinnipeds and the sea otter

Abstract The present study summarizes the factors contributing to oxygen storage capacity in several species of marine mammals. Additional data are presented on respiratory properties of blood. Phocid seals showed the highest Hb concentration and hematocrit which correlate with longer and deeper dives in comparison with the otariid seals, the walrus and the sea otter which were also studied. A larger circulating blood volume in the phocid seals gave them a blood O2 storage capacity more than twice the average for the other species studied. Muscle myoglobin concentration was also about twice as high in the phocid seals. The lung oxygen storage capacity calculated from maximum lung volume, was conversely smaller in the phocid seals than in the other species studied. The sea otter was exceptional with a very high lung O2 storage capacity making up two thirds of the total capacity. The larger total O2 storage capacity in the phocid seals is discussed in relation to the diving behavior of the animals. The respiratory properties of blood showed no significant adaptive features in O2-Hb affinity or Bohr shift, but a distinctly higher buffering capacity distinguishes blood of marine mammals from terrestrial non-diving species.

Respiration in a primitive air breather, amia calva☆

Abstract Amia calva is a primitive air breathing fish having a well vascularized air bladder and efficient gills. The roles of aquatic and aerial gas exchange were studied in relation to temperature, activity and gas composition of the ambient water. At 10 °C, Amia is relatively inactive and is an almost exclusive water breather. With increasing temperature and activity, the rate of oxygen depletion from the air bladder increases progressively and the air breathing rate increases. At 30 °C, three times as much oxygen is taken from air as from water but the gills continue to be the principal site for CO 2 elimination. There was a gradual increase of air breathing and gill breathing rates with decreasing oxygen tensions in the water (Pw O 2 ) until the air breathing rate increased sharply and gill breathing declined at a Pw O 2 of 40 to 50 mm Hg at 20 °C. The sharply increased emphasis on air breathing occurred at higher oxygen tensions at 30 °C. The gill breathing rate varied reciprocally with air bladder O 2 tensions. The changes of gas tensions in central systemic vessels and vessels of the air bladder indicate a tendency for blood to bypass the exchange vessels in a gas exchange organ, either gill or air bladder, when it was not the primary site for oxygen uptake. The bimodal breathing pattern of Amia is discussed relative to the distribution and behavior of the fish.

Respiration in the Crab, Cancer magister

Summary1.Hcy containing blood of the crab, Cancer magister, has a P50 value of 19.6 mm Hg at normal arterial pH (7.7). The Bohr shift (-log P50/pH) was −0.27. Temperature had a marked effect on Oxy-Hcy affinity. Average oxygen capacity was 3.44 vol %.2.Oxygen uptake was independent of ambient O2 tension down to about 50 mm Hg and showed an average value of 0.518 ml/kg/mm at 10° C in normoxic water. Oxygen extraction from the respiratory water current averaged 16 %.3.Ventilation was measured directly using an electromagnetic flow meter technique. Ventilation values were high compared to other water breathers and averaged 625 ml/kg/min.4.Arterial and venous blood were sampled from indwelling catheters in free moving, unrestrained animals. PaO2 averaged 91 mm Hg corresponding to nearly complete O2 saturation while PvO2 averaged 21 mm Hg giving a saturation of about 50 %. During activity both arterial and venous O2 tensions dropped but utilization of circulating O2 increased. The role of Hcy in O2 transport is discussed in the context of earlier studies on crustaceans which differ fundamentally from the results of the present study.5.The average cardiac output value calculated from the Fick principle was 29.5 ml/kg/min. The ventilation perfusion ratio was about 22 and somewhat higher than reported for other water breathing animals. The average PO2 gradient from water to blood was 60.5 mm Hg which closely matches values from fishes and the cephalopod Octopus dofleini.6.The results are analyzed and compared with similar information on gas exchange in other water breathers. It is concluded that effectiveness in gas exchange and gas transport is remarkably similar in widely diversified respiratory organs of aquatic animals.

Effect of chronic hypoxic hypoxia on the O2-Hb dissociation curve and respiratory gas transport in man☆

Abstract The effect of chronic hypoxic hypoxia on the O2-Hb dissociation curve and O2 and CO2 transport was determined in three groups of subjects: residents at altitude, patients with enital heart disease and patients with chronic obstructive lung disease. A shift to the right of the O2-Hb dissociation curve of normal, non hypoxic subjects, was found in all subjects of the first 2 groups (P50 = 30.6 mm Hg at pH = 7.4). The magnitude of the shift was not related to the hemoglobin concentration. In residents at altitude it was independent of the duration of the stay. In patients with chronic lung disease the direction of the shift depended upon the hematocrit, being leftward when Hct is normal (P50 = 24.7 mm Hg) and rightward in polycythemic patients (Hct 50%; P50 = 29.2 mm Hg). Our data reveal differences in CO2 transport between the 3 groups of subjects that corroborate previously reported findings. The causes and mechanisms of the shift are discussed. Low oxygen saturation in the venous blood appears to be the regulating factor, and changes occurring in the concentration of some intracellular constituents seem to be the mechanism of action. The physiological effects of the shift (left and right) are discussed.

Respiratory adaptations in selected amphibians.

Abstract In order to evaluate some of the respiratory adaptations concomitant with the transition from water breathing to air breathing, three amphibians were studied: the aquatic Necturus maculosus which possesses external gills and a poorly developed lung, Amphiuma tridactylum which has no gills but remains in water and depends on pulmonary breathing, and the bullfrog, Rana catesbeiana, which is somewhat terrestrial and uses pulmonary respiration. Respectively for Necturus, Amphiuma and bullfrog the oxygen capacity was 6.3, 7.6, and 8.0 vol %; the affinity for 02 or P50 at the physiological PCO2, was 14.5, 27 and 39 mm Hg; the Bohr effect or Δlog P50/ΔpH was −0.131, −0.205 and −0.288; the CO2 combining power at the physiological PCO2 was 20.0, 31.2 and 30.4 vol % and the buffering capacity, or ΔHCO3−/ΔpH, was −8.0, −9.2, and −16.4 mM/1/pH. The respiratory characteristics of these animals kept at 20°C was studied by in vivo blood gas measurements made at the same temperature. PaCO2 and PaCO2 of Necturus kept in water were 35 and 4.4 mm Hg respectively. When removed from water the exchange of blood gases was greatly impaired in spite of frequent air breathing. In free-breathing Amphiuma PaO2 was 81 and PaCO2 6 mm Hg. When prevented from air breathing PO2 decreased and PCO2 increased slowly suggesting that the animal uses its skin to exchange gases with water fairly effectively. In the bullfrog PaO2 was 95 and PaCO2 8 mm Hg. When the animal was immersed, PO2 decreased and PCO2 increased rapidly suggesting the absence of efficient skin respiration. These findings are regarded as expressing adaptive changes to meet an increased O2 availability of the external medium, and on elevated internal PCO2 in the transition from aquatic to aerial respiration.

The effect of cardiac disease on hemoglobin-oxygen binding

The relation between degree of cardiac functional impairment and changes in hemoglobin-oxygen affinity and 2,3-diphosphoglycerate (2,3-DPG) has been studied in 39 patients with noncyanotic heart disease. A progressive decline in hemoglobin-oxygen affinity was found with worsening cardiac function as assessed by cardiac index, arteriovenous oxygen (A-V O(2)) difference, and cardiac symptoms; this alteration in hemoglobin-oxygen binding represents a significant mechanism for adaptation to the limited oxygen supply imposed by the cardiac lesion. The highly significant correlation of mixed venous blood oxygen saturation (S[unk]V(VO2)) with 2,3-DPG and the position of the oxygen dissociation curve suggests that the level of deoxygenated hemoglobin is an important in vivo regulator of hemoglobin-oxygen affinity.

Respiratory control in the lungfish, Neoceratodus forsteri (krefft)☆

1. Respiratory control has been studied in the lungfish, Neoceratodus forsteri by measuring ventilation (Ve), oxygen uptake (VO2), per cent O2 extraction from water, breathing rates of branchial and aerial respiration and changes in blood gas and pulmonary gas composition during exposure to hypoxia and hypercarbia. 2. Hypoxic water represents a strong stimulus for compensatory increase in both branchial and aerial respiration. Water ventilation increases by a factor of 3 or 4 primarily as a result of increased depth of breathing. 3. The ventilation perfusion ratio decreased during hypoxia because of a marked increase in cardiac output. Hypoxia also increased the fraction of total blood flow perfusing the lung. Injection of nitrogen into the lung evoked no compensatory changes. 4. It is concluded that the chemoreceptors eliciting the compensatory changes are located on the external side facing the ambient water or in the efferent branchial blood vessels. 5. Elevated pCO2 in the ambient water depressed the branchial respiration but stimulated aerial respiration. 6. It is suggested that the primary regulatory effect of the response to increased ambient pCO2 is to prevent CO2 from entering the animal, while the secondary stimulation of air breathing is caused by hypoxic stimulation of chemoreceptors located in the efferent branchial vessels.

Respiratory function in the elasmobranch Squalus suckleyi G.

A signaling mechanism for gauges having an indicating pointer movable along the dial of the gauge in response to a variable supplied to the gauge and a set pointer positionable along the dial at preselected values of the variable. The signaling mechanism includes a switch operable in response to sensing of the position of the indicating pointer. The switch itself is mounted for movement relative to the set pointer and positionable along the dial independently thereof for sensing the indicating pointer when the latter precisely coincides with the position of the set pointer.