BSF. TBL2 Respiratory System

Created by pj_schmidlein Plus

Upgrade to
remove ads

1. Chronic Obstructive Pulmonary Disease 2. Asthma Attack

Case 25: Chronic Obstructive Pulmonary Disease (COPD)

Bernice Betweiler is a stupid old spinster, I mean seamstress, who won't stop smoking even tho no one likes her for it. So her lungs are as useless as she is.

1. Chronic bronchitis is associated w/ inflammation of airways & mucus hypersecretion, which ↑airway resistance. How does this explain her pulmonary function tests?

- ↑airway resistance → ↓airflow, esp. in expiration
→ expiratory phase compromised
→ air is trapped in lungs, so ↑residual volume (RV) & FRC
→ ↓vital capacity, b/c RV encroaches on it (greater fraction of TLC)

1. Her emphysema is associated w/ loss of alveolar-capillary units & ↓lung elasticity. How does this explain her pulmonary function tests?

- ↓elastance = ↑compliance
→ ↓elastic recoil force that drives air out of lungs, so expiration impaired
- also, airways us. kept open in expiration by radial traction by elastic recoil forces
→ airways may collapse in expiration, trapping air in lungs
→ ↑RV, ↑FRC, ↓VC

2. How is her ↑anteroposterior (AP) chest diameter explained by the results of her pulmonary function tests?

- compromised expiratory functions
→ air trapping, ↑RV, ↑FRC
→ barrel-shaped chests to breathe at higher lung volumes, b/c need more volume to compromise that left to residual volume

3. Why does she have a decrease in arterial P(O₂) (Pa(O₂))?

- Pa(O₂) was 48 mmHg (instead of 100)
- normal oxygenation of blood in lungs needs ventilation-perfusion matching
- she had impaired ventilation, so ↓V/↑Q
→ part of pulm. blood flow not ventilated (oxygenated), mixed w/ oxygenated blood to ↓P(O₂) overall

4. Why is her % O₂ saturation decreased, & what are the implications for O₂ delivery to the tissues?

- ↓P(O₂) causes ↓saturation, according to O₂-Hb dissociation curve
- O₂ content in blood largely depends on Hb binding (very little free O₂)

5. Her hemoglobin concentration is normal. If it had been decreased, would that have altered her Pa(O₂)? In what direction?

- ↓Hb → ↓O₂ content of blood (total amount decreased)
- BUT Pa(O₂) is determined by free, unbound O₂, so NOT directly affected by Hb conc.

6. Why does she have an increase in arterial P(CO₂)?

= hypercapnia
- b/c she could not eliminate all the CO₂ that her tissues made
→ unable to maintain alveolar ventilation, so retained CO₂

7. What acid-base disorder does she have, and what is the cause? Why is her HCO₃⁻ concentration increased?

- respiratory acidosis, secondary to CO₂ retention
- pH = 6.1 + log ([HCO₃⁻]/(P(CO₂)x.03))
= 6.1 + log(34/(69x.03)) = 7.32 < 7.4
- ↑[HCO₃⁻] b/c chronic resp. acidosis → renal compensation (HCO₃⁻ reabsorption), so only small ↓pH even tho ↑CO₂ (H₂CO₃)

8. How does respiratory acidosis alter the delivery of O₂ to the tissues?

- ↑P(CO₂) & ↓pH → right shift in O₂-dissociation curve (Bohr effect)
→ for given P(O₂), ↓% Hb saturation, so unloads easier in tissue, BUT loads worse in lungs to begin with

Case 24?: Asthma attack

Mary is a hottie with a body. A body that can't breathe. She wheezes and can't exhale so well.

1. Is this primarily a restrictive or obstructive disorder? Why?

- obstructive disease:
- airways narrow → ↑resistance to airflow into & out of lungs

2. Why is exhalation more difficult than inspiration in this person?

- ↑airway resistance → harder to expire
- esp. in forced expiration, when intrapleural pressure is pos. & compresses airways
→ airways close prematurely in expiration
→ air trapping, air stays in lungs

3. Why is wheezing more prominent on exhalation?

- wheezes are sounds made when air is forced thru narrowed airways
- In expiration, airways compress & close prematurely, instead of inspiration, so further narrowed and forced flow
→ more prominent sounds made on exhalation

4. Why is it easier to breathe at higher lung volume? Was she breathing at higher lung volume? Explain youself.

- ↑volume (↑radius)
→ ↓airflow resistance
→ ↑airflow, inspiration, breathing
- she had ↑residual volume, which would try to compensate for ↓resistance from inflammation

5. Why does the bronchodilator (epinephrine) exaggerate the tachycardia?

- even tho she already showed tachycardia, heart rate ↑ more b/c β₂-AR's on heart pacemaker cells respond to epinephrine

6. An anticholinergic agent was also suggested as a possible nebulizer agent. How might this help the breathing problem?

- anticholinergic → ↓parasymp. pathways:
→ bronchodilation
→ ↓inflammation, ↓hyper-responsiveness to NO
→ does not induce tachycardia (lowers parasymp, doesn't activate symp)

7. How does breathing in an oxygen-helium gas mixture help patients who have an asthma attack?

- He:O₂ mixture has ρ/η = 0.31 (density over viscosity), much lower than pure O₂ (1.00)
→ low ρ/η → ↓turbulence → ↓airflow resistance → ↑airflow rate
→ delivers O₂ in same conc. as atmosphere

8. What is the residual volume before & after treatment with a bronchial smooth muscle dilator? Explain the changes.

TLC = VC + RV:
→ RV(before) = 6.82 - 2.5 = 4.32 L
→ RV(after) = 5.96 - 4.15 = 1.81 L
- RV ↓ after bronchodilator b/c airways stay open, don't close early & trap air
→ more air expired, so ↓RV

9. Draw a normal flow-volume curve. How would it change with restrictive lung disease? Obstructive lung disease?

A: normal
B: restrictive lung disease: ↓VC, ↓TLC, ↓RV, ↑FEV₁/FVC
C: obstructive lung disease: ↓VC, ↑TLC, ↑RV, ↓FEV₁/FVC, ↓FEF₂₅-₇₅

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set