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Biological Sciences
Stephen Reid

1 BGYC34 PhysioEx Lab 7 Respiratory Systems Mechanics Marking Scheme Part 1 Complete PhysioEx lab #7. Hand-in all of the pages associated with the lab. Note that there are 5 activities to be completed. You DO NOT need to hand in the histology review supplement. (5 marks) MARKING NOTE: Ten of the questions (activities) below are each worth 0.5 marks. Activity 1: Measuring Respiratory Volumes Compute the minute respiratory volume (i.e., minute ventilation) using the following formula: MRV = TV X BPM = 500 ml X 15 breaths/min = 7.5 L/min. Does expiratory reserve volume (ERV) include tidal volume (VT)? No, ERV is the amount of air that can be exhaled following a normal tidal exhalation. **(0.5 marks)** Activity 2: Examining the Effect of Changing Airway Resistance on Respiratory Volumes Copy the FEV a1d vital capacity values from the computer screen to the chart below and then calculate the FEV1(%) by dividing the FEV1volume by the vital capacity and multiplying by 100. Record the FEV 1%) (also called FEV1/FVC) in chart 1. Radius (mm) FEV 1 FVC FEV 1%) 5.0 3541 4791 73.9 4.5 2303 3143 73.3 4.0 1422 1962 72.4 3.5 822 1150 71.4 3.0 436 621 70.2 **(0.5 marks)** (for completing the table) Explain your answer (should read explain your observations) FEV , FVC and FEV (%) all decrease as airway radius decreases because airway 1 1 diameter (radius) has decreased and it is harder to exhale (increased resistance). This is akin to an obstructive lung disease. **(0.5 marks)** 2 Activity 3: Examining the Effect of Surfactant The first two questions in this section are out of place. They should have been in activity 2. What happened to the FEV (%)1as the radius of the airways was decreased? FEV 1%) decreased as the radius of the airway was decreased. How has the air flow changed compared to the baseline run? Airflow decreased as the radius of the airway was decreased. Premature infants often have difficulty breathing. Explain why this might be so. Premature infants don’t produce enough surfactant making it hard for the lungs to expand. Activity 4: Investigating Intrapleural Pressure What happened to the lung in the left side of the bell jar? The lung deflated. How did the pressure in the left lung differ from that in the right lung? The pressure in the left lung was zero. Pressure in the right lung did not change. Explain your reasoning. The left lung deflated because the intrathoracic pressure was equal to atmospheric pressure. **(0.5 marks)** How did the total air flow in this trial compare with that in the previous trial when both pleural cavities were intact? Total flow was reduced by half. What do you think would happen if the two lungs were in a single large cavity instead of separate cavities? Both lungs would have deflated due to equal pressure inside and outside the thoracic cavity.** (0.5 marks)** Did the deflated lung re-inflate? No. Explain your answer.
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