The present study was aimed to elucidate the relationships between the capacity of oxygen uptake and low atmospheric pressure.
Four anesthetized male dogs were exposed to low pressure of different grades ; 560 mmHg, 460 mmHg, 360 mmHg, and 260 mmHg in a decompression chamber. Blood was drawn from femoral artery and vein through polyethylen tube to outside the chamber. The tube was filled with heparin in order to avoid coagulation when it was not in use. The blood was subjected to determination of oxygen content and oxygen capacity by means of Van Slyke method. Oxygen tension was determined from Hb-Oxygen dissociation curve at pH 7.40.
Arterial and venous oxygen content decreased with lowering the pressure, and the rate of decrease was higher in CaO₂ than in CvO₂. Thus Ca-vO₂ difference decreased from 5.5 vol% (at the control level) to 2.6 vol% (at 260 mmHg.) .
Though the mean oxygen capacity was 20.0 vol% and did not change at 560 mmHg, a significant increase was found at 460 mmHg and 360 mmHg ; they were 20.3 vol% and 20.9 vol% respectively.
PaO₂ fell parallel with lowering of environmental pressure from 92.0 mmHg at 760 mmHg to 29.7 mmHg at 260 mmHg ambient pressure. As venous oxygen tension exhibited a slight decline in contrast to PaO₂, Pa-vO₂ difference became smaller according to lowering the environmental pressure. The difference was 41.4 mmHg at the control level and 4.2 mmHg at 260 mmHg.
In conclusion, we should say that there seems to be two phases in the change of DLO₂ in hypoxic condition. In the first phase, the diffusion gradient decreases lineally with the ambient pressure and VO₂ is unchanged or shows only a slight decrease even in a relatively lower pressure. There may be an increase of DLO₂ accompanied with increase of cardiac output. In much lower ambient pressure, however, there appears the other phase in which QH and also DLO₂ decrease and in turn an apparent decrease of VO₂ can be seen.

To estimate the subjective or physiological intensity of work, many index have been employed concerning the functional responses of oxygen transport system. In this study the validity of the index VO₂/VO₂max was discussed.
22 untrained healthy boys aged 16 were selected for the program, and the work was performed with a bicycle ergometer. Work load was increased progressively; 720 kpm/ min (2kp × 60rpm) for the first two minutes, and then increased 180 kpm/min (0.5 kp × 60 rpm) every successive minute to exhaustion. VO₂ and heart rate were measured at each step of load intensity. The expired air was collected in Douglas bag and was analyzed by Sholander apparatus for oxygen and carbon dioxyde.
There were some individual differences in correlation curves of VE to VO₂ and of FEO₂ to VO₂. The differences, however, were reduced and almost the similar curves were obtained when VE and FEO₂ were plotted against VO₂/VO₂ max instead of VO₂.
VO₂/VO₂ max and HR/HR max gave a very high correlation, 0.96. Though the correlation between VO₂ max and total work performed in exercise was 0.68, the correlation between VO₂/VO₂ max and total work was-0.89.
From these results, we should say that the index VO₂/VO₂ max and other functional index using their maximal values as denominator may be quite useful. And also we may assume that the work can be done with the highest efficiency when VO₂, heart rate, FEO₂, VE and probably some other physiological functions are at about 60% of their maximum. At least, we may say that there might occur some changes at this point in physiological conditions relating to the work capacity.

BACKGROUND/AIMS: Twenty-four-hour esophageal impedance and pH monitoring allows detection of all types of reflux episodes and is considered the best technique for identifying gastroesophageal refluxes. However, normative data for the Japanese population are lacking. This multicenter study aimed to establish the normal range of 24-hour esophageal impedance and pH data both in the distal and the proximal esophagus in Japanese subjects. METHODS: Forty-two healthy volunteers (25 men and 17 women) with a mean ± standard deviation age of 33.3 ± 12.4 years (range: 22–72 years) underwent a combined 24-hour esophageal impedance and pH monitoring. According to the physical and pH properties, distal or proximal esophageal reflux events were categorized. RESULTS: Median 45 reflux events occurred in 24 hours, and the 95th percentile was 85 events. Unlike previous reports, liquid-containing reflux events are median 25/24 hours with the 95th percentile of 62/24 hours. Acidic reflux events were median 11/24 hours with the 95th percentile of 39/24 hours. Non-acidic gas reflux events were median 15/24 hours with the 95th percentile of 39/24 hours. Proximal reflux events accounted for 80% of the total reflux events and were mainly non-acidic gas refluxes. About 19% of liquid and mixed refluxes reached the proximal esophagus. CONCLUSIONS: Unlike previous studies, liquid-containing and acidic reflux events may be less frequent in the Japanese population. Non-acidic gas reflux events may be frequent and a cause of frequent proximal reflux events. This study provides important normative data for 24-hour impedance and pH monitoring in both the distal and the proximal esophagus in the Japanese population.
Asian Continental Ancestry Group* ; Electric Impedance* ; Esophagus ; Gastroesophageal Reflux ; Healthy Volunteers ; Humans ; Hydrogen-Ion Concentration* ; Male ; Reference Values*