Acid/Base Balance Changes During Exercise and Ventilation Scenario: You are a st

Question

Acid/Base Balance Changes During

Exercise and Ventilation

Scenario: You are a student in a large physiology class researching the causes of metabolic and respiratory acid/base balance disorders.   As a part of your lab, you have been asked to perform various exercises and give consent to have blood drawn before and after exercising.   

Experiment 1:

After consent is given, you take your seat on an exercise bike. You place your hand in hot water (45 degrees C) for 5 minutes. The hot water dilates your capillary beds increasing blood flow to your fingers where the blood sample will be taken. You are given instructions to cycle on the bike slowly without any significant workload. Blood samples are taken after 5 minutes to provide baseline measurements of blood gas, pH, and hematocrit.

While keeping your hand in the hot water, begin cycling with a 4 kilogram weight as fast as you can for 15 seconds. Rest for 30 seconds by cycling at a slow pace.   Repeat this period of fast cycling for 15 seconds and a rest period of slow cycling for 30 seconds for a total of 4 more rounds. After the final rest period, blood samples are taken and kept on ice. You can now vacate the exercise bike and wait your turn to complete the next experiment.   

The next experiment will require you to hyperventilate. If you do not know what hyperventilation is, skip to the bottom of this page.

Experiment 2:

As a part of your lab, you have been asked to perform hyperventilation and give consent to have blood drawn before and after the experiment.   After taking your seat in the designated chair, place your hand in the hot water for 5 minutes. In this time, you maintain a normal breathing rate and depth. At the end of 5 minutes, baseline blood samples are drawn.

Your instructor asks you to start hyperventilating for 30 seconds. After 30 seconds has elapsed, rest and

try to breathe normally for 30 seconds. Your instructor asks you to hyperventilate a second time. Do this for 30 seconds with a 30 second rest period. After the rest period, blood samples are taken.

Hyperventilation

Hyperventilation occurs as one inhales and exhales as much air as possible in a short amount of time. You can watch the following video to see someone hyperventilating. Start the video at 40 seconds and stop watching at 55 seconds. https://www.youtube.com/watch?v=EqXzBfCjbSs

1. Provide a statement of general acid/base principles being studied.

2. Explain the importance of buffers in the ECF and ICF compartments.

3. Provide the chemical reaction for the carbonic acid/bicarbonate buffer system.

Explanation / Answer

1. Acid base principle:- There are two types of acid base balance, respiratory and metabolic. The respiratory acid base balance is based on the concentration of carbon dioxide. Increase in concentration of carbon dioxide causes respiratory acidosis and decrease in carbon dioxide concentration causes respiratory alkalosis. Bicarbonate ion is associated with metabolic balance. Increased concentration of bicarbonate ion causes metabolic alkalosis and decreased concentration of bicarbonate causes metabolic acidosis.

2. The main function of buffer system is to resist the change in pH of the fluid. The most important buffer in the extra cellular fluid is carbon dioxide-bicarbonate buffer. It is important for metabolic balance but not for respiratory balance. The buffer in the intracellular fluid is mainly protein and phosphates. The buffer maintain the pH and fluid balance.

3. The carbonic acid bicarbonate buffer system maintain the fluid balance in the extracellular fluid. The chemical reaction is as follows:-

CO2 + H2O -> H2CO3 -> HCO3 + H +

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