Pulmonary Structure and Mechanics of Breathing

Pulmonary Structure and Function

• Six functions of the respiratory system need to be listed.
• The hierarchical organization of the conducting zone must be described.
• The hierarchical organization of the respiratory zone must be described.
• It is important to identify the number of bronchiolar branchpoints.
• The barriers that oxygen must travel through to reach utilization need to be identified.
• Identify the alveolar cells that are secretory.
• List the main muscles involved in inspiration.
• List the muscles involved in passive expiration.
• List the muscles involved in active expiration.
• Describe the pleural sac and its functions.

Mechanics of Breathing

• Three pressures determining airflow in the lungs need to be identified.
• Details on how pleural pressure must change to cause airflow into the lungs, and how this pressure is developed are needed.
• Describe the relationship between pleural pressure and pulmonary pressure in normal lungs during inspiration.
• The sequence of events in inspiration are needed.
• The sequence of events in expiration are needed.
• A graph illustrating the change in pulmonary pressure during normal inspiration and expiration is needed.
• Information is needed on how positive pulmonary pressure is created during expiration.
• Define compliance and provide the equation to calculate it.
• Identify what determines lung compliance.
• Explain why the compliance curve differs for inspiration and expiration.
• Determine whose lung is more compliant between Will (2L increase with 5mmHg transpulmonary pressure change) and Chris (1.8L increase with the same change).
• A compliance curve graph for Will and Chris should be drawn assuming equal total lung volume.
• Identify the relative volume at which lungs are most compliant.
• The reason premature infants have lungs of low compliance must be explained.
• Describe what would happen to lung compliance if water was substituted for surfactant.
• Define surfactant, and identify its origin.
• List three factors that determine the work of breathing.
• Identify the stage in the respiratory cycle when compliance is balanced.
• Explain how compliance work is affected by fibrosis of the lung.
• Explain why exercise results in increased lung compliance.
• The equation predicting airway resistance and the factors influencing it must be stated.
• Explain why exercise results in increased resistive work.
• Discuss why the work of breathing is increased during an asthma attack.
• Identify why airway resistance is lowest in the terminal bronchioles and alveoli.

Lung Volumes

• Define obstructive disease with examples.
• Define restrictive disease with examples.
• Define spirometry and explain how it is performed.
• A representative spirometry recording should be drawn, including maximal force inspiration and expiration, labeling 4 lung volumes and 4 lung capacities.
• Average values for tidal volume and total lung volume are needed.
• Explain the presence of residual volume and how it is measured.
• Detail how to determine whether an individual's lung volumes are within normal ranges.
• It is improtant to know how FVC is measured.
• Define what FEV1 represents and how it is measured.
• Identify possible issues if FEV1 is abnormally low.
• Detail how to determine if values for FEV1 are abnormal.
• List the factors determining lung volume variability between individuals.
• Predict athletic performance based on lung volume, given Will has 6L and Chris has 5L.
• Explain the difference between anatomical and physiological dead space.
• Provide a quick estimate of individual anatomical dead space.
• List the causes of physiological dead space.
• Describe what will happen if you breathe rapidly at 30 breaths/min with shallow breaths of 250ml, weighing 250 pounds.
• Draw spirometry maximal flow-volume loops for normal individuals and those with obstructive and restrictive diseases.
• It is important to explain why these loops differ in these diseases.
• Explain how the relationships between lung volumes impact normal tidal breathing.
• Explain why patients with restrictive disease should breathe in rapid, shallow breaths.
• Explain why patients with obstructive disease should breathe in deep, slow breaths.

Gas Exchange

• Calculate the partial pressure for oxygen in the air at normal atmospheric pressure (760mmHg) if it is 50% oxygen.
• Identify what determines the gas content of fluid.
• Identify which gas has the highest concentration in water at room temperature: CO2 or O2.
• Describe how the diffusion rate of a gas in fluid is affected as:
  • The temperature of the fluid increases.
  • The pressure difference decreases.
  • The distance the gas must diffuse increases.
• Describe what happens to the diffusion of gas through a membrane if:
  • The membrane becomes thicker.
  • The pressure difference becomes smaller.
  • The surface area decreases
• Give examples of diseases that would impact each of these.
• List the four factors causing the difference between PIO2 and PAO2, and itentify steps to bring PAO2 and PIO2 closer in value.
• Calculate PIO2 at an atmospheric pressure of 600mmHg (assuming PH2O is 4mmHg), and calculate PAO2 assuming a PCO2 of 40mmHg and R of 0.8 on top of a mountain.
• Describe the impact this would have on the diffusion rate of O2 across the alveolar walls.
• State the PO2 levels in the atmospheric air, alveolar air, arterial blood, and venous blood.
• The reasons for the difference in each must be stated.
• State the PCO2 levels in the atmospheric air, alveolar air, arterial blood, and venous blood.
• Detail the reasons for the difference in each.
• Explain the mismatch between alveolar ventilation and capillary perfusion in the upper lung and how exercise helps correct this.
• Calculate the saturation of hemoglobin using the values determined for PAO2 in question 7, and whether an oxygen breathing apparatus would be helpful.
• Explain what the P50 value tells you.
• List the factors that will affect P50, how they will affect it, and why it is important that so many factors inhibit oxygen association with hemoglobin.
• Identify the predominant method of moving CO2 through the bloodstream.
• Describe what happens to blood pH as CO2 increases and why.
• Describe what happens to blood pH as CO2 decreases and why.
• Predict the effect on blood pH if you hyperventilate and significantly decrease PaCO2.

Control of Respiration

• Identify where the DRG is located and its function.
• Identify where the VRG is located and its function.
• Describe the role of the PRG, and the consequences if destroyed due to trauma.
• Describe how the hypothalamus influences breathing.
• Describe how the motor control centers influence breathing.
• Identify the protective reflexes that prevent the lungs from overinflating.
• Detail the difference between central and peripheral chemoreceptors and their methods of regulating breathing.
• Describe how exercise influences respiratory rate.
• Detail the effect of hyperventilation on normal breathing rate and why.
• Explain how breathing would be affected if the central chemoreceptors were removed from the system (e.g., drug or alcohol overdose).