Pulmonary Ventilation
Pulmonary Structure and Function
Pulmonary
Ventilation –
Process by which
ambient air is
moved into and
exchanges with air
in the lungs
…Different from
oxygen
consumption
Figure 12.1
Pulmonary Structure and Function
Gas exchange (O2 and
CO2) occurs in the
alveoli
O2 transfers from alveolus
to capillary blood
CO2 transfers from
capillary blood to alveolus
Each minute at rest
250 ml of O2 and 200
ml of CO2 diffuse in
opposite directions
Fig 12.1
Pulmonary Structure and Function
Lungs contain 600
million alveoli
Extremely thinwalled sacs (0.3
mm thick)
Lie side by side
with thin walled
capillaries
Alveoli receive
largest blood
supply of any
organ in the body
Fig 12.1
Pulmonary Structure and Function
Lungs provide
the gas exchange
surface
separating blood
from alveolar
gases
Lungs –
Extremely large
surface area for
gas exchange
Figure 12.2
Adult lung weighs 1 kg and hold 4-6 L of air
Pulmonary Structure and Function
Pulmonary ventilation functions
primarily to maintain a constant and
favorable concentration of O2 and CO2 in
the alveoli during rest and exercise
Adequate pulmonary ventilation ensures
complete gas exchange before blood
leaves lungs for transport to tissues
Pulmonary Structure and Function
Breathing mechanics
Fig 12.3
Inspiration – diaphragm descends, ribs are
raised, volume increases, intrapulmonic pressure
decreases, air rushes in (chest cavity size
increases)
Contributing muscles: external intercostals,
sternocleidomastoids, scalenes, spinal extensors
Pulmonary Structure and Function
Breathing mechanics
Fig 12.3
Expiration – Passive process
diaphragm relaxes, ribs lower, volume
decreases, intrapulmonic pressure increases, air
rushes out (chest cavity size decreases)
Contributing muscles: rectus abdominus,
internal intercostals, posterior inferior serratus
Pulmonary Structure and Function
Ventilatory System:
Conducting Zone –
Trachea to Bronchioles
No alveoli
Air transport, warming,
humidification, particle
filtration
Anatomic "Dead" Space
*Respiratory Zone –
Bronchioles to Alveoli
Surface area for gas
exchange
Fig 12.4
Pulmonary Structure and Function
Measuring Lung Volume:
Lung volumes measurements (static or
dynamic) can help identify potential
obstructive or restrictive lung diseases
Lung volumes vary
with age, gender,
body size, body
composition and
stature
Water-sealed, volume
displacement recording
spirometer
Fig 12.6
Pulmonary Structure and Function
Static Lung
Volume
Measurements:
Provides record of
ventilatory volume
and breathing rate
Fig 12.6
Tidal Volume (TV) – volume inspired or expired per breath (600 ml)
Inspiratory Reserve Volume (IRV) – maximal inspiration at end of
tidal inspiration (3000 ml)
Expiratory Reserve Volume (ERV) – maximal expiration at end of
tidal expiration (1200 ml)
Force Vital Capacity (FVC) – maximal volume expired after maximal
inspiration (TV+IRV+ERV; 4800 ml)
Pulmonary Structure and Function
Static Lung
Volume
Measurements:
Fig 12.6
Residual Lung Volume (RLV) – air volume remaining in lungs after
maximal expiration (1200 ml)
-allows uninterrupted gas exchange between blood and alveoli
Functional Residual Capacity (FRC) – Volume in lungs after tidal
expiration (ERV + RLV; 2400 ml)
Total Lung Capacity (TLC) – volume in lungs after maximal
inspiration (FVC + RLV; 6000 ml)
Pulmonary Structure and Function
Dynamic Lung Volumes:
Adequate pulmonary ventilation depends on
ability to sustain high airflow levels (not air
movement in single breath)
Dynamic Ventilation depends on:
1) FVC (“stroke volume” of the lungs)
2) Breathing rate
High airflow levels (velocity) depends on lung
compliance (ability to stretch or expand):
“loose” (high compliance) – emphysema, asthma
“stiff” (low compliance) – fibrosis
Pulmonary Structure and Function
Dynamic Lung Volumes
No Elastic Recoil
(loose)
Too Much
Elastic Recoil
(stiff)
Fig 12.8
Forced Expiratory Volume (FEV) to FVC ratio:
FVC measured over 1 s (FEV1.0) – measures pulmonary
airflow capacity, or overall resistance to air movement
upstream in the lungs (normal value = 80-85% of FVC)
Pulmonary Structure and Function
3. Minute Ventilation (VE):
•Volume of air moved in and out of respiratory
tract per minute
•VE=Breathing Rate (BR) x TV
At rest
VE = 12 breaths/min x 0.5 L/breath
VE = 6 Lmin
Exercise
VE = 30 x 2.5
VE = 75 Lmin
Moderate
VE=50 x 3.5
VE=150 Lmin
Vigorous
Pulmonary Structure and Function
Dynamic Lung Volumes:
•
Measurements of dynamic lung function can
indicate the severity of obstructive or
restrictive lung diseases
•
FEV/FVC - Normal or increased for restrictive lung
disease (80% or greater)
•
FEV/FVC - <70% indicates obstructive lung disease
Pulmonary Structure and Function
Aging and lifestyle
affect lung volumes
and pulmonary
function
Aging: Decreased lung
compliance
FEV1.0 and FVC decrease
after age 20
Diffusion capacity
decreases
Partial Pressure of O2
decreases
Diaphragm muscles
weakens by ~25%
Pulmonary Structure and Function
Dynamic Lung Volumes:
Provide no
information
about aerobic
fitness:
No difference in
healthy vs
olympic athletes
Not predictive of
track or marathon
performance,
distance running
Pulmonary Structure and Function
Dynamic Lung Volumes:
•
Important part of standard medical/health
examination for “at risk” exercisers (smokers,
asthmatics)
Pulmonary Structure and Function
How do we ensure
sufficient air
reaches the alveoli
during exercise?
By increasing rate
and depth of
breathing increases alveolar
ventilation
•TV increases at start of moderate exercise
Fig 12.10
•As intensity increases, TV plateaus at 60% of FVC
•Breathing rate provides alveolar ventilation at higher
exercise intensities
Pulmonary Structure and Function
Definitions:
Hyperventilation – increase in pulmonary
ventilation that exceeds the O2 needs of
metabolism (“overbreathing”)
Unloads CO2 excessively (which constricts
arteries with less O2 to brain)
Can lead to unconsciousness.
Pulmonary Structure and Function
Definitions:
Dyspnea – shortness of breath or subjective
distress in breathing (sense of inability to
breathe)
Occurs in physical exertion (novel exercisers),
at altitude, or with obstructive or restrictive
pulmonary disorders
Result of elevated CO2 and H+ in blood from
fatigue of poorly trained respiratory muscles
(shallow, ineffective breathing)
Pulmonary Structure and Function
Definitions:
Valsalva Maneuver – Increases intrathoracic
pressure that occurs when exhalation is
forced against a closed glottis
Results:
Collapse of veins in thoracic region
Impaired venous return
Acute DROP in arterial blood pressure
Decreased blood supply to brain
"spots before the eyes" "fainting"
Pulmonary Structure and Function
Definitions:
Valsalva Maneuver
Acute drop in blood
pressure
Fig 12.11
Blood pressure
overshoot
Pulmonary Structure and Function
Valsalva Maneuver
*Valsalva
Maneuver does
NOT cause the
acute rise in
blood pressure
with
resistance
training
Fig 12.11