Essentials of Pathophysiology
CHAPTER 21
CONTROL OF RESPIRATORY
FUNCTION
PRE LECTURE QUIZ
F

F

T

T

T

Pulmonary ventilation is the movement of blood
through the lungs.
Deoxygenated blood leaves the right heart through
the pulmonary veins.
The peripheral chemoreceptors monitor arterial
oxygen levels and will stimulate respirations when the
PO2 has dropped below 60 mm Hg.
Lung compliance refers to the ease with which the
lungs can be inflated.
The effects of airway resistance on airflow can be
illustrated by using Poiseuille’s law, which states that
resistance to flow is inversely related to the fourth
power of the radius.
PRE LECTURE QUIZ
Diffusion

__________ exerts very important effects on lung inflation,
including lowering the surface tension, increasing lung
compliance and ease of inflation, and assisting in preventing
pulmonary edema by keeping the alveoli dry.

The relation between the oxygen carried in combination with
hemoglobin and the PO2 of the blood can be described using
the oxygen–hemoglobin __________ curve.

The most important chemoreceptors for sensing changes in
blood carbon dioxide content are the __________
chemoreceptors.

__________ refers to the movement of gases in the alveoli and
across the alveolar–capillary membrane.

The blood vessels in the pulmonary circulation undergo
marked ________________ when they are exposed to hypoxia.
dissociation
peripherial
Surfactant
Vasoconstriction
LUNG FUNCTIONS



Gas exchange
 Moves O2 into blood
 Removes CO2 from blood
Blood storage
Regulate vasoconstricting substances
formed locally in injured tissue, acts in vasodilation of small
 Bradykinin- arterioles, is considered to play a part in inflammatory processes
 Angiotensin II
 Heparin- sulfuric acid ester that occurs especially in the liver and lungs, that
prolongs the clotting time of blood by preventing the formation of
fibrin
obtained from the liver and lungs of domesticated food animals
protamine sulfate- is a heparin antagonist
CONDUCTING AIRWAYS



Move air into
lungs
Warm and
humidify air
Trap inhaled
particles (Mucus
escalator)
CONDUCTING & RESPIRATORY AIRWAYS
Note Change of Cell Type & Thinning of Air to Blood
Distance
MEMBRANES AND CAVITIES




Parietal pleura
Visceral pleura
Pleural space (between
pleurae)
Mediastinum
RESPIRATORY AIRWAYS

Bronchioles

Alveoli

Gas is exchanged
with the blood
QUESTION
Which serous membrane lines the thoracic
cavity?
a. Viscera pleura
b. Parietal pleura
c. Visceral mediastinum
d. Parietal mediastinum
ANSWER
Parietal pleura
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.
b.
RESPIRATORY MUSCLES



Diaphragm
Accessory muscles of
inhalation
 External intercostals
 Scalene
 Sternocleidomastoid
Accessory muscles of
exhalation
 Internal intercostals
 Abdominal muscles
QUESTION
Tell whether the following statement is true or
false:
During inhalation, the diaphragm contracts and
flattens.
ANSWER
True
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.
COMPLIANCE

How easily lungs can be inflated depends on:
 Elastin
 Water
and collagen fibers
content
 Surface
tension
SURFACTANT REDUCES SURFACE TENSION
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?
LUNG VOLUMES
Time
LUNG CAPACITIES

Vital capacity

Inspiratory
capacity

Functional
residual capacity

Total lung capacity
LUNG VOLUMES

Tidal volume

Inspiratory
reserve

Expiratory
reserve

Residual
volume
DYNAMIC LUNG FUNCTION

Forced vital capacity

Forced expiratory volume

FEV1.0

Minute volume

Maximum voluntary ventilation
FORCED VITAL CAPACITY
A
B
Volume diagram
Flow diagram
C

MMEF =Mean Mid
Expiratory Flow

Matching:
A  Normal expiration
B  Obstructive expiration
C  Restricted Lungs
QUESTION
Which measure of lung function indicates the
total amount of air that the lungs can hold?
a. Tidal volume
b. Functional residual capacity
c. Vital capacity
d. Total lung capacity
ANSWER
d. Total lung capacity is the maximum amount of
air that the lungs can hold—everything (volumewise) at the end of a maximal inhalation (the
deepest breath one can possibly take). Normal
TLC is approximately 6 L.
GAS EXCHANGE


Oxygen moves from alveolar air into blood
Carbon dioxide moves from blood into alveolar air
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?
VENTILATION–PERFUSION MISMATCHING

Blood with no
air
Air with no
Blood


Air and blood
In mismatch Blood
goes to parts of the
lung that do not have
oxygen, and
Blood does not go to
parts of the lung that
have oxygen
In normal function
blood perfusion is
routed opposite of
other body tissues.
QUESTION
Tell whether the following statement is true or
false:
Ventilation-perfusion mismatch results in
hypoxia.
ANSWER
True
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.
BLOOD GASES—OXYGEN

Dissolved oxygen = PaO2 or PO2


Normal value >80 mm Hg
Oxygen bound to hemoglobin = oxyhemoglobin

Normal value 95% to 97% saturation
HEMOGLOBIN HOLDS 4 OXYGEN MOLECULES
• How saturated is this molecule of hemoglobin?
• How could a person have a hemoglobin saturation
of 95%?


Amount of oxygen the
blood can hold
What is the oxygen
capacity of normal
blood?
What is the oxygen
capacity of anemic
blood?
mg/dL

mg/dL
OXYGEN CAPACITY
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?
OXYGEN RELEASE (CONT.)



Most body tissues have a PO2 of 40-60
mm Hg
How much oxygen does the normal blood
release at a PO2 of 40 mm Hg?
The anemic blood?
OXYGEN AFFINITY

A

B
C

PO2
Factors that shift the curve:
CO2, pH, DPG, Fetal Hb
How tightly the
hemoglobin holds
onto the oxygen
Which of these
hemoglobin
samples has the
highest oxygen
affinity?
Which will release
the most oxygen to
the tissues?
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+
 When you exhale you remove CO2 from your
blood and also decrease the amount of
carbonic acid, raising your blood pH
 CO2 + H2O H2CO3 H+ + HCO3
QUESTION
Tell whether the following statement is true or
false:
The relationship between PCO2 and pH is direct.
ANSWER
False
The relationship is indirect. As PCO2 levels rise, the
amount of carbonic acid in the blood increases,
making the pH more acidic (decreasing it).
CO2 + H2O H2CO3 H+ + HCO3pH= 𝑙𝑜𝑔
1
[𝐻 + ]
Respiratory Control
lungs
inflate
stretch receptors
note increased lung
volume
pneumotaxic
begins inspiration
respiratory
centers
apneustic
stretch receptors
note decreased lung
volume
stops inspiration;
begins exhalation
lungs
deflate
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
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?