Robert Adams and Dr. Robert Conlee, Health and Human Performance
Oxygen is the essential element in the air we breathe. The concentration of oxygen is constant in the atmosphere at approximately 21%. However barometric pressure is not constant throughout the atmosphere. The barometric pressure measures the amount of pressure the particles in the atmosphere exert and varies depending on altitude and weather. At sea level the barometric pressure is 760mmHg. The oxygen molecules accessible for respiration exert 21% of that pressure. The pressure of these oxygen molecules is 160mmHg and is referred to as the partial pressure of oxygen. As the altitude increases the total barometric pressure decreases from 760mmHg to 448mmHg at 14,000ft. The partial pressure of oxygen lowers to 94mmHg at this altitude. This difference in the partial pressure decreases the oxygen available to the body by 42% from sea level to 14,000 ft. The body must adjust to this decreased amount of oxygen. It does so by increasing the amount of breathing. This increase in respiration is referred to as the Respiratory Response and is measured by minute ventilation (Liters/minute). It is the body’s key adaptation for adjusting to lower oxygen levels at higher altitudes.
The present study investigates the difference in the blood oxygen concentration [(Hb)(% saturation)(1.34 ml oxygen/g Hb) +0.03] that may exist among individuals relative to their respiratory response.
To test this difference ten individuals had arterial blood samples taken by a respiratory therapist at the Provo airport (4,300 ft.) and in an ambient air aircraft at an elevation of 14,000 ft. The participant’s minute ventilation was also recorded at each altitude. Each blood sample was then placed in an ice chest and taken to Utah Valley Regional Medical Center and inserted into a computerized Radiometer for analysis of the blood gasses.
To measure the amount of variance the standard deviations were derived from the data and are listed in the chart below. The increase in the minute ventilation’s standard deviation from 1.91 L/min. at 4,300 ft. to 2.02 L/min. at 14,000 ft. shows an increase in the respiratory response. The standard deviation of the oxygen concentration went form 1.41 % oxygen concentration at 4,300 ft. to 1.32 % oxygen concentration at 14,000 ft. This shows no significant variance in the oxygen concentration in relation to minute ventilation variance.
The experiment had many factors that were difficult to control for which may have affected the results of the experiment. The barometric pressure was measured at the time of the 4,300 ft. measurements and at the time of the 14,000 ft. measurements. Four of the ten cases were found to have some degree of change in the barometric pressure. This variance in the barometric pressure was beyond the expected variance that was a part of the altitude change. Additionally the average time that elapsed between the drawing of the blood samples and their insertion into the Radiometer varied from an average 56 min. for the 4,300 ft. samples to 77min. for the 14,000 ft. samples. The oxygen-hemoglobin complex begins to break down at approximately 60 minute from the time that it leaves the body. The number of participants was also low. Since Hb is a factor in the equation to find the oxygen concentration and Hb varies between males and females, there need to be enough participants to give readings for each respective group. Controlling these factors in a repeated experiment would yield greater confidence in the outcome of the results.