Intended Learning Outcomes
Predict the changes in chest wall, pulmonary and respiratory system compliances when a patient is placed in the prone position; draw these predictions on the Rahn diagram.
Relate right ventricular [RV] preload to pleural pressure and RV afterload to trans-pulmonary pressure when combining the Guyton diagram and the Rahn diagram.
Explain how mediastinal weight changes esophageal pressure in the prone and supine positions
Reexamine how changes in intrathoracic pressure and transpulmonary pressure alter right ventricular preload, afterload and size.
Explain how the driving pressure & stress index are expected to change upon pronation.
Part A [complete alone] ----------------
Reflect on the cases that you worked through in learning modules 5 & 6; consider the differences you and your learning partner observed between these two patients with respect to their right ventricular preload and afterload.
Read the case presented in this article.
Which of the cases in module 5 & 6 most closely relate to the patient who is placed in the prone position in the article above? Think back to a patient with severe ARDS that you have encountered. Did you prone the patient or did you consider it? What is your understanding on how this changes pulmonary mechanics & physiology? How might these changes alter a patient’s hemodynamics? Imagine that you are meeting with the patient’s family and you are asked how turning the patient will affect her heart? How would you respond?
Part B [complete alone] ----------------
Read the rest of the article from above and watch its accompanying vodcast below.
Learning Module Seven
Part C [complete together] ----------------
1. Return to the learning activities that you completed for modules 5 & 6; focus on the cartoon of the alveolus that you drew with you partner. Now draw a cartoon of an upper lobe alveolus in the supine and prone position for the patient in this module.
2. Explain to your partner how the stress index is expected to change from the supine to prone position in this patient. What about the driving pressure? Draw the changes on the Rahn diagram and relate this to the cartoon of the alveolus that you drew above.
3. Draw the combined Guyton-Rahn diagram for the patient in the supine position. Label on the picture: the plateau pressure, the pleural pressure and the trans-pulmonary pressure. Which of these relates to the stress across the alveolus you drew in activity 1.? In the supine position, how does the measured esophageal pressure relate to the actual pleural pressure? Add the measured esophageal pressure to this diagram and describe how is affects the trans-pulmonary pressure.
4. Which pressure on the combined Guyton-Rahn diagram that you drew in exercise 3 relates to the stress across the right ventricle? Predict with you partner what an ultrasound of the right ventricle superior and inferior vena cava might look like in this patient in the supine position.
5. Return to the idea of ‘volume responsiveness’ that you encountered in the very first module. How does volume responsiveness relate to the patient in the prone position? How has this concept changed in this patient from the supine to prone position and why?
6. Return to the idea of ‘volume status’ that you encountered in the very first module. How did the patient’s volume status change from supine to prone? Is the patient’s SVC & IVC size expected to change from supine to prone? Why? Reconcile this with the idea of volume status.
7. Use the combined Guyton-Rahn diagram to predict the hemodynamic consequences of placing the emphysematous patient (in module 5 & 6) into the prone position. One of you should construct the Rahn diagram to predict changes in pleural pressure, plateau pressure and trans-pulmonary pressure. The other should then construct the Guyton diagram on top of this. How will the diameter of the SVC change?
8. Review the intended learning outcomes with your partner. With your partner, create a power-point presentation of no more than 4 slides that you will give to another group. Incorporate the drawings that you made if you can. Use the presentation to explain the 4 most important points from the intended learning outcomes; peer-review another group’s presentation.
Heart-lung.org will provide a comprehensive, on-line tutorial in cardiovascular and respiratory physiology for the interested medical student, resident and fellow.
The first 4 chapters will cover basic physiology and pathophysiology with an emphasis on the Campbell and Guyton Diagrams.
The remaining 4 chapters will focus on clinically-relevant topics in the intensive care unit; the discussions will be largely drawn from the physiology covered in the first half of the textbook.