Human Blood Pressure and Respiration (Ex. 18, 19, 21)

Procedure:

Today you will choose one of your group members as the experimental subject. You do not want to use the person who is the most or least fit. You will be using three channels on the Physiograph machine. Channel 1 will be the EKG and will be used to measure heart rate. The EKG is attached to the machine using a High Gain Coupler (special equipment). To hook it up, place the disk electrodes on the subject's chest (you can do this in the restroom if you would like) in an area where there is respiratory movement, low on the rib cage. You need to put electrode cream in the cups on the electrodes so they will contact the skin. You should tape them into place and wrap the brown bandage around the chest over them to hold them securely. Tape a third electrode near the belt area for a ground. Channel 2 will be the Impedence Pneumograph. This is not a transducer because it only measures the amount of electrical impedence between the electrodes. You will connect this to the coupler in channel one using a silver cord, to allow you to read impedence through the same electrodes as EKG. Channel 3 will be the Electrosphygmograph (ESG). This will be used to measure and record blood pressure. Be very careful with the grey wire attached to it. It is very fragile. You need to balance and calibrate this according to the instructions on pages 143 and 144 in the lab manual. To measure blood pressure in the subject follow the instructions (p. 144 - 146). Be sure not to undo the cuff (Velcro) while the record button is on. A very sensitive microphone records the Korotkoff sounds, and it could be damaged by such a loud noise. To measure blood pressure, make sure the subject remains still while the reading is made or the noises will interfere, follow lab manual instructions. Now you are ready to begin the experiments.

Part A: Effects of Posture on Blood Pressure (Ex. 18)

For this exercise you will record only blood pressure. You need to record 5 different records.
  1. Blood pressure while sitting (control record for comparison)
  2. Blood pressure after lying flat for 5 minutes. This posture distrubutes the blood evenly so that not as much force is needed to push the blood around the body. (decrease in BP).
  3. Blood pressure immediately after standing. Pump the cuff up, then stand and take the reading. This posture will allow gravity to pull blood down towards the feet quickly and blood pressure must counteract this drain. (increase in BP). If you don't get it the first time try again.
  4. Blood pressure while performing the valsalva maneuver, p. 146. Pump the cuff up first, then take the reading while the subject is doing this maneuver. High intrathoracic pressure compresses the veins and decreases venous return (decrease in BP).
  5. Have the subject immerse their forearm in an ice water bath for a few minutes. Immerse the arm that is attached to the ESG being careful not to get the equipment wet. Take the BP reading immediately after the subject removes their arm from the water and rests it on the lab bench. (increase in BP).
Recording Criteria:
Title: Effects of Posture on Blood Pressure
Transducer: ESG
Paper Speed: 0.25 cm/sec
Timer: 60 sec.
Special Equipment: ESG coupler
Label systolic and diastolic blood pressure in mm of Hg on all records.
Discuss how blood pressure is effected by these postures. Why did you have to measure BP immediately after standing? What would happen to BP if you wait? How does the brain detect changes in BP and how is BP adjusted?

Part B: Human Respiration and Asphyxia (Ex. 19)

For these records you will be using only channel 2. You will do two records.
1. Control Record - 1/2 page of respirations
2. Effect of Asphyxia on Respiration- record 1 minute with a paper bag over the subjects mouth then 1/2 after (returning to normal). Make sure the subject doesn't conciously change their respiratory rate while the bag is over their mouth, they should relax and breath normally.
Recording Criteria:
Title: Human Respiration and Asphyxia
Paper Speed: 0.25 cm/sec
Timer: 60 sec.
Special Equipment: Impedence pneumograph
Label average amplitude (cm of pen deflection) and rate (respiration per min) on all records. Label points on records where paper bag was placed over the mouth and taken off. where hyperventilation begins and ends, and where subject was startled.
Discussion: Effect of asphyxia on blood pCO2 and pH. Where does the CO2 go in the brain? What effect does the resulting stimulus have on respiratory rate?

Part C: Human Respiration (Hyperventilation and Cord Facilitation) Ex. 19

For these records you will be using only channel 2. You will do two records.
1. Hyperventilation - Record 1/2 page of control, hyperventilation for 1-2 minutes, 1/2 page of return to normal. To hyperventilate correctly you must take deep controlled breaths, not quick shallow ones. Do not continue to hyperventilate if you feel uncomfortable!
2. Cord Facilitation - Leave the record running and try to surprise the subject. With the subject lying across the bench with their foot hanging off, have one group member divert the subject's attention by telling a story. Have another person hold a bucket of ice water under the subject's foot. When the subject isn't expecting it lift the bucket onto their foot. The record should show a gasp, or involuntary apnea.
Recording Criteria:
Title: Human Respiration (Hyperventilation and Cord facilitation)
Paper Speed: 0.25 cm/sec
Timer: 60 sec.
Special Equipment: Impedence pneumograph
Label average amplitude (cm of pen deflection) and rate (respiration per min) on all records. Label points on records where hyperventilation begins and ends, and where subject was startled.
Discussion: What happens to blood pCO2 and pH during hyperventilation? Where does the CO2 go in the brain? What effect does the resulting decrease in stimulus (because of decrease in CO2) have on respiratory rate? What caused the reflex apnea observed?

Part D: Human Exercise Physiology (Ex. 21)

For this experiment you will use all three channels at the same time. Each of the following records are 1/2 page long. You will make one record before exercise, the control record. Then you will exercise for aproximately 10 minutes. The next records are (1) immediately after exercise (2) 1 minute post exercise (3) 2 minutes post exercise, and (4) 3 minutes post exercise. To make these records start recording and measure blood pressure once during each record.
Recording Criteria:
Title: Human Exercise Physiology
Transducer: ESG
Paper Speed: 0.25 cm/sec
Timer: 60 sec.
Special Equipment: ESG coupler, Impedence pneumograph
Label Systolic and diastolic blood pressure (ESG) in mm of Hg, heart rate (EKG) in beats per minute, and respiratory rate in breaths per minute and respiratory depth in average cm of pen deflection for each record.
Discuss the theories that explain how the body "knows" when to increase respiratory movements even though blood H+, CO2, and O2 remain constant.

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