Chapter 22 Marieb Hoehn 2019 p 8181 Ch

Chapter 22 Marieb & Hoehn (2019), p. 8181

Ch. 22: Test Question Templates • Q 1. If given an appropriate graph of volume of air in lung vs. time, estimate or calculate FEV 1/FVC ratio, FVC, residual volume, TLC, tidal volume, and/or minute ventilation. • Example (from Winter 2019 exam): 2

• Q 2. If given two of the three values, calculate third one: minute ventilation, respiratory rate, and tidal volume. • Example: Lola takes 10 breaths per minute, and her minute ventilation is 6000 m. L air per minute. What is her tidal volume? • Q 3. If given spirometry data and reference values, determine whether the data are consistent with obstructive pulmonary disease, restrictive pulmonary disease, both, or neither. • Example [from Fall 2019 test]: Rik is put through various pulmonary function tests. At time 0 in the table below, he begins deflating his fully inflated lungs as forcefully and rapidly as he can. You can assume that by the time of 4 seconds, he has reached his residual volume (RV). Based on these data, is he likely to have an obstructive lung disease? Explain your reasoning, citing any relevant math. 3

• Q 4. Given changes to components of Fick’s Law of Diffusion, say whether the diffusion rate will increase or decrease, or whether the information given is insufficient to determine this. • Example: The conditions in a patient’s lungs change such that the O 2 concentration gradient from lungs to pulmonary capillary blood increases, and the diffusion barrier thickness also increases. What will be the net effect of these two changes on O 2 diffusion rate into the blood? Explain the direction of change (increase or decrease), or explain why you can’t tell from the information given. 4

Functions of the Respiratory System • 2 main ones • Bulk flow in and out of lungs (Poiseuille) • Diffusion of O 2 and CO 2 (Fick) S. Freeman et al. (2014), Figure 45. 1 (like Marieb & Hoehn, Figure 22. 1) 5

The most important muscles for breathing Q 1. What are they? Q 2. Do they contract during inhalation or exhalation? Q 3. How does their contraction change thoracic cavity? Q 4. How does their relaxation change thoracic cavity? Marieb & Hoehn (2019), Figure 22. 16 6

Why does air move in and out of the lungs? A simple description of breathing is this: The contraction of your diaphragm and external intercostal muscles expands your thorax. Since your lungs are tethered to the thorax walls, they expand too, and additional air enters the now-enlarged lungs. Then your inspiratory muscles relax and the process reverses. This description is true, but incomplete. It doesn’t explain scenarios such as pneumothorax, when a hole in the chest wall impairs breathing even if the lungs themselves are still intact. The thorax can still expand shrink – so why don’t the lungs follow along any more? Clearly, the pressures in the different compartments must be important. For a fluid (air) to flow in bulk, there must be a pressure gradient. Our respiratory system manipulates volumes to create the desired pressure gradients and thus the desired flow (see following slides). 7

Changing a compartment’s pressure by changing its volume Boyle’s Law states that for a given quantity of gas molecules, the pressure and volume are inversely proportional -- as one goes up, the other goes down. Thus, to decrease the pressure of a compartment, increase its volume. To increase the pressure of a compartment, decrease its volume. Martini et al. (2015), Figure 23. 12 8

The lungs are often represented as a balloon in a jar. Balloon = lungs, jar = thorax wall, space between them = pleural cavity. Contract inspiratory muscles, ↑ pleural cavity volume, ↓ pleural cavity pressure, ↑ transpulmonary pressure gradient, lung inflates Freeman et al. (2017), Figure 44. 12 Relax inspiratory muscles, ↓ pleural cavity volume, ↑ pleural cavity pressure, ↓transpulmonary pressure gradient, lung deflates 9

Questions regarding the previous slide… Q 1. Would the balloon still inflate if there was a hole in it? Q 2. Would the balloon still inflate if there was a hole in the side of the jar? One more point…. Why doesn’t the balloon ever expand all the way to the sides of the jar? There must be an opposing force! Thus, the actual volume of normal lungs at any given time reflects the balance of 2 opposing forces… Finally, note differences between the balloon model and actual lungs. 1. The two lungs are in separate pleural cavities. 2. Our actual pleural cavity volume is TINY. 3. Diaphragm shapes/changes are different. 10

Pneumothorax Q 1. What does the word “pneumothorax” mean, based on its roots? Q 2. A knife blade goes through the skin into the left pleural cavity, but does not touch the lungs. Which lungs will collapse, if any? youtube. com/watch? v=0 v. Z 9 g. Vy. Wreo 11

Quantifying ventilation Q 1. Definition of tidal volume? Q 2. Definition of residual volume? Q 3. Definition of Vital Capacity (VC or FVC)? What is it in this particular example? Marieb & Hoehn (2019), Figure 22. 19 12

Minute ventilation: just like cardiac output! Stroke Volume m. L/beat Tidal Volume m. L/breath x Heart Rate = Cardiac Output x beats/min = m. L/min x Respiration Rate = Minute Ventilation x breaths/min = m. L/min Two Equations in One! Volume moved per beat Times number of beats per minute Is volume of blood per minute; That’s all this equation has in it! faculty. washington. edu/crowther/Misc/Songs/2 equations. shtml Volume moved per breath Times number of breaths per minute Is volume of air per minute; That’s all this equation has in it! 13

Q 1. What is the minute ventilation based on the data below? (Hint: this should remind you of CO calculations!) 14

To our previous spirometry terms we now add one more: FEV 1. Time (sec) 1 2 3 4 5 6 7 FEV 1 stands for Forced Expiratory Volume in 1 second. To measure FEV 1, the patient is instructed to inflate maximally and then exhale as quickly and as fully as possible. How much air leaves in that first second? Q 1. What is the approximate FEV 1 in this example? Marieb & Hoehn (2019), Figure 22. 19 a 15

FEV 1 could be low for different reasons: • Maybe the patient can’t get air out quickly. • Or maybe there isn’t much air in the lungs at the start of exhalation, so FEV 1 will be small regardless of how quickly the air leaves. To distinguish between these options, FEV 1 is often expressed as a percentage of the FVC. In other words, “Out of all the air that COULD come out of your lungs, how much of it can you get out in 1 second? ” Rule of thumb: less than 80% is bad; 80% or above is fine. Q 1. Does the previous slide represent a FEV 1/FVC ratio that is normal, or low? 16

Two general types of lung disease… NORMAL OBSTRUCTIVE RESTRICTIVE Problem Example For each box: Normal, or Low? FVC FEV 1/FVC 17

Case study: “I can’t stop coughing!” Marya moved from Southern California to play soccer at Northern Minnesota University (NMU) as a highly recruited player. All was well until she got sick with a miserable cold. She soon recovered, but now she finds herself with a lingering dry cough and difficulty catching her breath any time she exerts herself, which is every day! She also notices it has gotten worse as the weather has become colder. You guessed it – Marya has asthma. Q 1. Is this an obstructive problem or a restrictive problem? Q 2. This disorder is often treated with an inhaler that mimics the autonomic nervous system. How does that work? Marieb & Hoehn (2016) instructor materials; Image from www. chkd. org 18

Neural control of breathing Q 1. Which part of the brain is the most important controller of breathing, according to this figure? Note the spinal cord levels involved. www. nataliescasebook. com/tag/neural-control-of-breathing 19

Chemoreceptors & negative feedback Q 1. These chemoreceptors are called “central” or “peripheral. ” WHY? Q 2. Why do hypoventilation and hyperventilation usually resolve spontaneously? Marieb & Hoehn (2019), Fig. 22. 27 20

Ch. 22: Additional Resources • Pearson Mastering has an Interactive Physiology video on Pulmonary Ventilation. • Respiratory chemoreceptor song: • https: //faculty. washington. edu/crowther/Misc/Songs/exchange. shtml • Other suggestions? Let me know…. 21

Answer key for Suggested Lecture Outline file • You should already have access to answers to some of the questions (Check Your Understanding, online Practice Quiz, online Practice Test) • Answers to pre-lecture questions and end-of-chapter Review Questions will be in the Presenter Notes that accompany this slide. 22