320 likes | 661 Views
Students seem to be much less prepared for mechanics than they were 40 years ago. Apparently elementary physics now receives less attention in college and high school. I grew up building radios, and notions of pressure, flow and resistance are ingrained. Today's kids simply plug in electronic components.
E N D
1. APS Refresher Course Mechanics of BreathingJohn B. West, MD, PhD, DscUCSD School of MedicineExperimental Biology 2008April 5, 2008
2. Students seem to be much less prepared for mechanics than they were 40 years ago
3. Apparently elementary physics now receives less attention in college and high school
4. I grew up building radios, and notions of pressure, flow and resistance are ingrained. Today’s kids simply plug in electronic components
5. Two examples of confusion from this year’s teaching
6. In a demonstration with a lung in a Lucite box, a water manometer showed the box pressure. One student was confused about whether the pressure indicated on the manometer was above or below atmospheric pressure
7. Another example on the mechanics of the pulmonary circulation
8. An embolism completely blocks blood flow to one lobe of the lung. Which of the following is FALSE? A. Vascular resistance of the non-occluded lung is decreased.
B. Vascular resistance of the overall lung is decreased.
C. Alveolar Po2 in the occluded lobe is increased.
D. If total ventilation and blood flow remain constant, arterial Po2 will fall.
E. After 3 days, the compliance of the occluded lobe will be reduced.
9. B is a false statement. If a large part of the circulation is blocked the overall vascular resistance must increase. Astonishingly some students cannot see this. (They argue that recruitment and distension of vessels in the non-embolized area will result in a reduced overall resistance)
10. Because some students are so ill-prepared for the simple physical concepts, we now include a short primer before the lecture notes
15. Our physiology course has two lectures on mechanics, one on statics, and the other on dynamics. We also have a demonstration on pressure-volume behavior of a rabbit lung, and three small-group discussions covering some of the material.
16. Topics in the first lecture includeMuscles of respiration Inspiration ExpirationElastic properties of the lung Pressure-volume curve Compliance Surface tensionRegional differences of ventilation Airway closureElastic properties of the chest wall
17. Here are some of the slides in the first lecture taken from my book
24. Topics in the second lecture include Airway resistance Laminar and turbulent flow Measurement of resistance Pressures in the breathing cycle Factors determining resistance Dynamic compressionCauses of uneven ventilationTissue resistanceWork of breathing Work done on the lung Total work of breathing
25. Here are some of the slides in the second lecture
32. Conclusions Students are less well-prepared to understand simple physical principles than they were a few years ago
We now include a short primer at the beginning of the course
Mechanics of breathing remains a very difficult topic for some students