Biggest Loser

Introduction

A female patient is brought into the emergency room. She is complaining of shortness of breath and extreme difficulty in breathing after a vigorous run. Suspecting respiratory acidosis, a condition in which the blood pH is too acidic, the emergency room doctor orders a blood gas test.

What is blood gas? A blood gas is exactly that...it measures the dissolved gases in your bloodstream. This provides one of the best measurements of what is known as the acid-base balance. The body is an active chemical reaction, requiring a precise balance of the acids and bases, a measurement known as pH. The normal pH is 7.40. There are four parameters which are measured: Oxygen (O2), Carbon Dioxide (CO2), Bicarbonate (HCO3-), and pH (Reece, 2002).

Many people today exercise as a way of improving their health and physical abilities. When we exercise, our heart rate, systolic blood pressure, and cardiac output (the amount of blood pumped per heart beat) all increase. Blood flow to the heart, the muscles, and the skin increase. The body's metabolism becomes more active, producing increased levels of carbon dioxide (CO2) and hydrogen ions (H+) in the muscles. This metabolism is cellular respiration (Silverthorn, 2002).

Cellular Respiration is the process used by living cells to break down sugar molecules (glucose) that living things get when eating plants or animals. This breakdown involves oxygen and results in the production of energy, carbon dioxide and water: Glucose + oxygen --> CO2 + H2O + ATP (energy) (Silverthorn, 2004). ATP is used as our energy source; however, CO2 is a byproduct and must be removed from the body. When CO2 mixes with water in the interstitial fluid, the reaction is carbonic acid (H2CO3). Additionally, carbonic acid breaks apart into bicarbonate (HCO3-) and H+. It is the free H+ that lowers the pH level, thus lead to the disruption of the acid-base balance. Fortunately the body has a wide array of mechanisms to maintain homeostasis.

One of these mechanisms is maintaining the amount of CO2 and the pH level in balance during exercise. This is due to the counterpart elimination of CO2 via respiratory ventilation (Thompford, 2005). Simply put, the increase in production of CO2 and carbonic acid is equally eliminated by the increased breathing, during exercise. This event is called hypernea. If a person does not exhibit hyperpnea when exercising, the outcome may be hypoventilating, not breathing deeply and/or frequently enough to eliminate the accumulating CO2 in the body. The opposite effect is hyperventilating. Hyperventilating while resting causes excessive elimination of CO2, which causes low carbonic acid levels and an increase in pH. Another way that our body maintains homeostasis is through chemical buffers.

Chemical or pH buffers are utilized to prevent too much carbonic acid from lowering the pH level or too little carbonic acid from increasing the pH level. The mechanism of chemical buffers is the ability to either donate or receive H+. Remember that excess H+ is floating around when carbonic acid breaks down. So, amino acids found in proteins like blood plasma and hemoglobin will absorb the free floating H+. And, the carboxyl group from the proteins will give off an H+ if too little carbonic acid is present (Thompford, 2005). These two examples demonstrate how our body utilizes various methods to keep an optimum CO2 and pH levels. High concentration of CO2 after exercise will lower the blood pH level. However, chemical buffers will slow pH levels from fluctuating from normal levels, even in the presence of high CO2 levels.

Material and Methods

In order to test the negative correlation of increased CO2 and the decrease in pH level, a laboratory experiment within a lab manual, designed by Dr. John Thompford, professor of Physiology at Mira Costa College, was used.

A basic solution was utilized in all of the following exercises. The purpose of this medium is to indicate pH levels when various amounts of CO2 are present. It was also used to demonstrate the effects of buffers. The solution is a very strong base, which has a pH level of 8-10. When CO2 is introduced, the carbonic acid will eventually turn the high pH level of the solution to below 8.0.

• The basic solution was formulated as follows:

400 ml of deionized water was mixed with 10 ml 0.1 Molar NaOH (sodium hydroxide, strong base), and 12 drops of Phenolphthalein indicator (Phenolphthalein is an indicator that is pink in alkaline solutions between pH 8-10, red at pH > 10 and clear in solutions that have pH < 8.0.). This solution was used for part I, II, and III of our experiment.

PART I: Effects