1. Respiratory Physiology Review

2. Lung Functions
• Gas exchange
– Moves O2 into blood
– Removes CO2 from blood
• Blood storage
• Regulate vasoconstricting substances
– Bradykinin
– Angiotensin II
– Heparin

3. Conducting Airways
• Move air into lungs
• Warm and
humidify air
• Trap inhaled
particles

4. Respiratory
Airways
• Bronchioles
• Alveoli
• Gas is exchanged
with the blood

5. Membranes and Cavities
• Parietal pleura
• Visceral pleura
• Pleural space (between
pleurae)
• Mediastinum

6. Question
Which serous membrane lines the thoracic
cavity?
b. Visceral pleura
c. Parietal pleura
d. Visceral mediastinum
e. Parietal mediastinum

7. a. Parietal pleura Answer
Rationale: The organs and walls of the thoracic and
abdominal cavities are covered with serous
membranes. Visceral membranes cover the
organ; parietal membranes line the cavity walls.
The two membranes and the space between
them allow for ease of movement. The thoracic
cavity is lined by parietal pleura; the lungs are
covered by visceral pleura.

8. Respiratory Muscles
• Diaphragm
• Accessory muscles of inhalation
– External intercostals
– Scalene
– Sternocleidomastoid
• Accessory muscles of exhalation
– Internal intercostals
– Abdominal muscles

9. Question
Tell whether the following statement is true or
false.
During inhalation, the diaphragm contracts and
flattens.

10. True Answer
Rationale: The diaphragm is the main muscle of
inhalation/inspiration. During inhalation, the
diaphragm contracts and flattens (it moves
downward in order to accommodate the
volume of air you are taking in, allowing space
for the lungs to expand). During exhalation,
the diaphragm relaxes and moves back up.

11. Compliance
• How easily lungs can be inflated depends on:
– Elastin and collagen fibers
– Water content
– Surface tension

12. Surfactant Reduces Surface Tension

13. Scenario
• A man’s lungs were damaged during a fire
• He developed severe respiratory distress
• The doctor said smoke inhalation had caused an inflammation of his alveoli
• The damage had also destroyed some of his surfactant
Question:
• What had happened to his lung compliance?
• Why was he given positive-pressure ventilation?

14. Lung Volumes
• Tidal volume
• Inspiratory reserve
• Expiratory reserve
• Residual volume

15. Lung Capacities
• Vital capacity
• Inspiratory capacity
• Functional residual capacity
• Total lung capacity

16. Dynamic Lung Function
• Forced vital capacity
• Forced expiratory volume
• FEV1.0
• Minute volume
• Maximum voluntary ventilation

17. Question
Which measure of lung function indicates the
total amount of air that the lungs can hold?
b. Tidal volume
c. Functional residual capacity
d. Vital capacity
e. Total lung capacity

18. Answer
a. Total lung capacity
Rationale: Total lung capacity is the maximum
amount of air that the lungs can hold—
everything (volume-wise) at the end of a
maximal inhalation (the deepest breath one
can possibly take). Normal TLC is
approximately 6 L.

19. Gas Exchange
• Oxygen moves from alveolar
air into blood
• Carbon dioxide moves from
blood into alveolar air

20. Ventilation and Perfusion
Scenario:
A child has inhaled a peanut, blocking her left primary bronchus.
Question:
• How will the ventilation in her two lungs change?
• How will the composition of the air in her two lungs differ?
• Which lung should she send more blood to?
• How should her body alter perfusion of the lungs?

21. Ventilation–Perfusion Mismatching
• Blood goes to parts
of the lung that do
not have oxygen to
give it
• Blood does not go to
parts of the lung
that have oxygen

22. Question
Tell whether the following statement is true or
false.
Ventilation–perfusion mismatch results in
hypoxia.

23. True Answer
Rationale: In either case (ventilation without
perfusion or perfusion without ventilation),
oxygen is not picked up by the capillaries and
delivered to the tissues. The result of
decreased oxygen at the tissue level is termed
hypoxia.

24. Blood Gases—Oxygen
• Dissolved oxygen = PaO2 or PO2
– Normal value >80 mm Hg
• Oxygen bound to hemoglobin = oxyhemoglobin
– Normal value 95% to 97% saturation

25. Hemoglobin Holds Four Oxygen
Molecules
• How saturated is
O2 this molecule of
O2 hemoglobin?
• How could a person
O2 have a hemoglobin
saturation of 95%?

26. Oxygen Capacity
• Amount of
oxygen the
blood can hold
• What is the
oxygen capacity
of normal
blood?
• What is the

27. Oxygen Release
• If the blood released
half of its oxygen to the
tissues:
– How much oxygen
would the normal
tissues receive?
– How much would
the anemic person’s
tissues receive?

28. Oxygen Release (cont.)
• Most body
tissues have a
PO2 of 40–60
mm Hg
• How much
oxygen does
the normal
blood release

29. Oxygen Affinity
• How tightly the
hemoglobin holds
A onto the oxygen
B • Which of these
hemoglobin
C samples has the
highest oxygen
affinity?
• Which will release
the most oxygen to
the tissues?

30. Blood Gases—Carbon Dioxide
• Dissolved carbon dioxide = PaCO2 or PCO2
– Normal value 35–45 mm Hg
• Carbon dioxide bound to hemoglobin =
carbaminohemoglobin
• Carbonic acid  bicarbonate ion and H+

31. Question
Tell whether the following statement is true or
false.
The relationship between PCO2 and pH is direct.

32. False Answer
Rationale: The relationship is indirect. As PCO2
levels rise, the amount of carbonic acid in the
blood increases, making the pH more acidic
(decreasing it).

33. lungs
inflate
stretch receptors
note increased lung begins inspiration
volume
pneumotaxic respiratory apneustic
centers
stretch receptors
stops inspiration;
note decreased lung
begins exhalation
volume
lungs
deflate

34. Chemoreceptors Can Adjust
Respiration Rate
• Central chemoreceptors
– Measure PCO2 and pH in cerebrospinal fluid
– Increase respiration when PCO2 increases or pH
decreases
• Peripheral chemoreceptors
– Measure PO2 in arterial blood
– Increase respiration when PO2 <60 mm Hg

35. Scenario
• You are caring for a COPD client
• He has chronically high PCO2
• He is being given low-flow oxygen and complains all the time
that he “needs more air,” so you turn up his oxygen.
Question:
• When you check on him later, he is unconscious and not
breathing. What happened?