7: Respiratory System Mechanics
Chart 1
Radius
Flow
TV (ml)
(mm) (ml/min)
ERV
(ml)
IRV
(ml)
RV (ml) VC (ml)
FEV1
(ml)
TLC
(ml)
5.00
7485
499
—-
—-
—-
—-
—-
—-
5.00
7500
500
1200
3091
1200
4791
3541
5991
4.50
4920
328
787
2028
1613
3143
2303
4756
4.00
3075
205
492
1266
1908
1962
1422
3871
3.50
1800
120
288
742
2112
1150
872
3262
3.00
975
65
156
401
2244
621
436
2865
1.What would be an example of an everyday respiratory event the ERV button simulates? The ERV button
simulates a forced expiration.
2. What additional skeletal muscles are utilized in an ERV activity? In forced expiration, abdominal-wall
muscles and the internal intercostal muscles contract.
3. What was the FEV1 (%) at the initial radius of 5.00 mm? The FEV1 (%) at a radius of 5 mm is 73.9%
(3541/4791 100%).
4. What happened to the FEV1 (%) as the radius of the airways decreased? How well did the results compare
with your prediction? The FEV1 (%) decreased proportionally as the radius decreased.
5. Explain why the results from the experiment suggest that there is an obstructive, rather than a restrictive,
pulmonary problem. The FEV1 (%) decreased proportionally as the radius decreased which is
characteristic of an obstructive pulmonary problem.
Activity 2: Comparative Spirometry
Chart 2
Patient type
TV
(ml)
ERV
(ml)
IRV
(ml)
RV
(ml)
FVC
(ml)
TLC
(ml)
FEV1
(ml)
FEV1
(%)
Normal
500
1500
2000
1000
5000
6000
4000
80%
Emphysema
500
750
2000
2750
3250
6000
1625
50%
Acute Asthma
Attack
300
750
2700
2250
3750
6000
1500
40%
Plus Inhaler
500
1500
2800
1200
4800
6000
3840
80%
Moderate
Exercise
187
5
1125
2000
1000
ND
6000
ND
ND
Heavy
Exercise
365
0
750
600
1000
ND
6000
ND
ND
1. What lung values changed (from those of the normal patient) in the spirogram when the patient with
emphysema was selected? Why did these values change as they did? How well did the results compare with
your prediction? The values that change for the patient with emphysema are ERV, IRV, RV, FVC, FEV1 and
the FEV1 (%). These changes are due to the loss of elastic recoil.
2. Which of these two parameters changed more for the patient with emphysema, the FVC or the FEV1? The
FEV1 decreased significantly more than the FVC for the patient with emphysema.
3. What lung values changed (from those of the normal patient) in the spirogram when the patient experiencing
an acute asthma attack was selected? Why did these values change as they did? How well did the results
compare with your prediction? The values that changed for the patient with the acute asthma attack are TV,
ERV, IRV, RV, FVC, FEV1 and the FEV1 (%). These changes are due to the restriction of the airways.
4. How is having an acute asthma attack similar to having emphysema? How is it different? Both are similar
because they are obstructive diseases characterized by increased airway resistance. It is more difficult to
exhale with emphysema than with asthma.
5. Describe the effect that the inhaler medication had on the asthmatic patient. Did all the spirogram values
return to “normal”? Why do you think some values did not return all the way to normal? How well did the
results compare with your prediction? The values that returned to normal were TV, ERV, FEV1 (%). The
smooth muscles in the bronchioles didn’t return to normal plus mucus still blocks the airway.
6. How much of an increase in FEV1 do you think is required for it to be considered significantly improved by
the medication? A significant improvement would be at least 10–15% improvement. Student answers will
vary on this response.
7. With moderate aerobic exercise, which changed more from normal breathing, the ERV or the IRV? How
well did the results compare with your prediction? The lung value that changed more with moderate
exercise was IRV.
8. Compare the breathing rates during normal breathing, moderate exercise, and heavy exercise. The breathing
rate increased with moderate and heavy exercise. A greater increase in breathing rate was seen with heavy
exercise.
Activity 3: Effect of Surfactant and Intrapleural Pressure on Respiration
Chart 3:
Surfactant
Intrapleural
pressure left
(atm)
Intrapleural
pressure
right (atm)
Airflow left
(ml/min)
Airflow right
(ml/min)
Total
airflow
(ml/min)
0
–4
–4
49.69
49.69
99.38
2
–4
–4
69.56
69.56
139.13
4
–4
–4
89.44
89.44
178.88
0
–4
–4
49.69
49.69
99.38
0
0.00
–4
0.00
49.69
49.69
0
0.00
–4
0.00
49.69
49.69
0
–4
–4
49.69
49.69
99.38
1. What effect does the addition of surfactant have on the airflow? How well did the results compare with your
prediction? The surfactant addition further increased airflow because the surface tension in the alveoli
decreased allowing the alveoli to expand more.
2. Why does surfactant affect airflow in this manner? Surfactant serves to decrease the surface tension.
3. What effect did opening the valve have on the left lung? Why does this happen? It caused the lung to
collapse because the pressure in the pleural cavity is less than the intrapulmonary pressure. Air flows from
the lungs causing the collapse of the lung.
4. What effect on the collapsed lung in the left side of the glass bell jar did you observe when you closed the
valve? How well did the results compare with your prediction? The lung did remain collapsed and did not
reinflate after the valve was closed.
5. What emergency medical condition does opening the left valve simulate? Opening the left valve simulates a
pneumothorax.
6. In the last part of this activity, you clicked the Reset button to draw the air out of the intrapleural space and
return the lung to its normal resting condition. What emergency procedure would be used to achieve this
result if these were the lungs in a living person? Emergency professionals will insert a chest tube to pull a
partial vacuum out of the intrapleural space to return it to a value below atmospheric pressure.
7. What do you think would happen when the valve is opened if the two lungs were in a single large cavity
rather than separate cavities? Both lungs would collapse if the lungs were not separated. Breathing would
stop and the person would die.