Download Columbia College

Chapter 9
The Pulmonary System
and Exercise
Slide Show developed by:
Richard C. Krejci, Ph.D.
Professor of Public Health
Columbia College 10.5.11
Chapter 9 Objectives
1. Diagram the ventilatory system, and show the glottis,
larynx, trachea, bronchi, bronchioles, and alveoli.
2. Describe the dynamics of inspiration and expiration during
rest and exercise.
3. Describe the “Valsalva Maneuver” and its physiologic
consequences.
4. Define minute ventilation, alveolar minute ventilation,
ventilation-perfusion ratio, and anatomic and physiologic
dead spaces.
5. Explain the “Bohr Effect” and its benefit during physical
activity.
Chapter 9 Objectives (Cont.)
6. List and quantify three means for carbon dioxide transport
in blood.
7. Identify major factors that regulate pulmonary ventilation
during rest and exercise.
8. Describe how hyperventilation extends breath-holding time
but can have dangerous consequences in sport diving.
9. Graph relationships among pulmonary ventilation, blood
lactate concentrations, and oxygen uptake during
incremental exercise. Indicate the demarcation points for
the lactate threshold and onset of blood lactate
accumulation.
10.Explain what triggers exercise-induced asthma, and
identify factors that affect its severity.
Pulmonary Functions
1. Supply oxygen required in metabolism
2. Eliminate carbon dioxide produced in metabolism
3. Regulate hydrogen ion concentration [H+] to maintain
acid-base balance
Anatomy of Ventilation
• The five major structures of the Pulmonary System
include:





Nose and Mouth
Trachea
Bronchi
Bronchioles
Alveoli
Anatomy of Ventilation (Cont.)
Mechanics of Ventilation: Inspiration
• Inspiration

Diaphragm contracts, flattens out, moves
downward.


The air in the lungs expands, reducing its pressure.

Inspiration concludes when thoracic cavity
expansion ceases, and intra-pulmonic pressure
increases to equal atmospheric pressure.
Pressure differential between lungs and ambient
air sucks air in through the nose and mouth, and
inflates the lungs.
Mechanics of Ventilation: Expiration
•
•
A predominantly passive process
•
The sternum and ribs swing down, while the diaphragm
moves toward the thoracic cavity.
•
These movements decrease chest cavity volume and
compress alveolar gas; this forces it out through the
respiratory tract to the atmosphere.
Air moves out of the lungs from the recoil of stretched
lung tissue and relaxation of the inspiratory muscles.
Static Lung Volumes
•
Tidal Volume (TV): Air moved during either the inspiratory or expiratory
phase of each breathing cycle; ranges between 0.4 and 1.0 L of air per
breath.
•
Inspiratory Reserve Volume (IRV): An additional volume of 2.5-3.5 L
above TV that is the reserve for inhalation.
•
Expiratory Reserve Volume (ERV): After a normal exhalation, the
additional volume that can be exhaled; 1.0-1.5 L for men, 10-20% lower
for women.
•
Forced Vital Capacity (FVC): Total air volume moved in one breath
from full inspiration to maximum expiration; varies with body size and
body position when measuring.
•
Residual Lung Volume (RLV): Following a maximal exhalation,
volume of air that remains that cannot be exhaled; 1.2-1.6 L for men,
1.0-1.2 L for women.
Static Lung Volumes (Cont.)
Dynamic Lung Volumes
•
Dynamic measures of pulmonary ventilation depend on:


The maximum stroke volume of the lungs
The speed of moving a volume of air
•
•
FEV1.0: Percentage of FVC expelled in 1 second
•
Maximum Voluntary Ventilation: Requires rapid, deep
breathing for 15 seconds that is extrapolated to the volume
breathed for one minute; ranges between 140 and 180
L·min-1 for men, 80 to 120 L·min-1 for women
FEV1.0/FVC: Reflects expiratory power and overall
resistance to air movement in the lungs; averages ~85%
Minute Ventilation
• Minute Ventilation (VE) = Breathing Rate x Tidal
Volume)
• 6.0 L·min-1 = 12 x 0.5 L
Alveolar Ventilation
• The portion of minute ventilation that mixes with
the air in the alveolar chambers
• Determines gaseous concentrations at the
alveolar-capillary membrane (blood)
Anatomic Dead Space
•
The air that fills the nose, mouth, trachea, and other
non-diffusible conducting portions of the respiratory
tract
•
150 to 200 mL or about 30% of the resting tidal
volume in healthy people
Physiologic Dead Space
•
The portion of the alveolar volume with poor tissue
regional perfusion or inadequate ventilation
•
Physiologic dead space can increase to 50% of resting
tidal volume because of:

Inadequate perfusion during hemorrhage or blockage of the
pulmonary circulation from an embolism or blood clot

Inadequate alveolar ventilation in chronic pulmonary disease
Physiologic Dead Space (Cont.)
Disruptions in Normal Breathing
Patterns
•
Dyspnea: Shortness of breath or subjective distress in
breathing
•
Hyperventilation: An increase in pulmonary ventilation
that exceeds the oxygen needs of metabolism
Gas Concentration and Pressures
•
Gas Concentration: The amount of gas in a given
volume determined by the product of the gas’ partial
pressure and solubility
•
Gas Pressure: The force exerted by the gas molecules
against the surfaces they encounter
•
Partial Pressure = Percentage concentration x Total
pressure of gas mixture

Ambient Air: PO2 = 159 mm Hg; PCO2 = 0.2 mm Hg;
PN2 = 600 mm Hg


Tracheal Air: PO2 = 149 mm Hg; PCO2 stays the same
Alveolar Air: PO2 = 103 mm Hg; PCO2 = 39 mm Hg
Henry’s Law
• The amount of a gas dissolved in a fluid depends
on:

Pressure differential between the gas above the fluid
and dissolved in it

Solubility (dissolving power) of the gas in the fluid
Solution of oxygen in water
Gas Exchange
•
In the Body: The exchange of gases between lungs
and blood and their movement at the tissue level takes
place passively by diffusion.
•
In the Lungs: The first step in oxygen transport
involves the transfer of oxygen from the alveoli into the
blood.
•
In the Tissues: Oxygen leaves capillary blood and
flows toward metabolizing cells, while carbon dioxide
flows from the cell into the blood
Gas Exchange (Cont.)
Oxygen Transport in Blood
•
In physical solution: Dissolved in the fluid portion of the
blood; establishes the PO2 of the blood and tissue fluids
•
Combined with hemoglobin: In loose combination with
the iron-protein hemoglobin molecule in the red blood cell;
increases the blood’s oxygen-carrying capacity 65 to 70
times above that normally dissolved in plasma

Each 100 mL of blood contains approximately 15 to 16 g of Hb in
men

5-10% less for women or 14 g per 100 mL of blood
Oxyhemoglobin dissociation curve p282
Carbon Dioxide Transport in Blood
•
Physical solution in plasma (7%–10%); establishes the PCO2 of the
blood
•
•
Loose combination with Hb (20%)
Combined with water as bicarbonate (70%)
Carbon Dioxide Transport in Blood (Cont.)
Ventilatory Control During Rest:
Neural Factors
•
Respiratory cycle comes from inherent, automatic activity of
inspiratory neurons.
•
Exhalation begins by passive recoil of stretched lung tissue
and raised ribs when the inspiratory muscles relax.
•
Activation of expiratory neurons and associated muscles
that further facilitate expiration.
•
As expiration proceeds, the inspiratory center is released
once again from inhibition and progressively becomes more
active.
Ventilatory Control During Rest: Neural
Factors (Cont.)
Ventilatory Control During Rest:
Humoral Factors
•
The chemical state of the blood largely regulates pulmonary ventilation
at rest

Variations in arterial PO2, PCO2, acidity, and temperature activate
sensitive neural units in the medulla and arterial system
•
Chemoreceptors: Structures that stimulate ventilation in response to
increased carbon dioxide, temperature, and acidity, a decrease in
oxygen and blood pressure, and perhaps a decline in circulating
potassium
•
Carbon dioxide pressure in arterial plasma provides the most important
respiratory stimulus at rest.
Aortic And Carotid Cell Bodies
Ventilatory Control During Exercise:
Chemical Factors
•
Factors

Po2
• Arterial PO2 in exercise does not decrease to the
point that stimulates ventilation by chemoreceptor
activation


•
Pco2
[H+]
Chemical stimuli cannot fully explain the hyperpnea during
physical activity.
Ventilatory Control During Exercise:
Neurogenic Factors
•
Cortical Influence

•
Neural outflow from regions of the motor cortex during exercise
and cortical activation in anticipation of exercise stimulate
respiratory neurons in the medulla
Peripheral Influence

Sensory input from joints, tendons, and muscles adjust ventilation
during exercise
Integrated Regulation
•
•
No single factor controls breathing in exercise.
•
Phase II Ventilation: Central command input plus
medullary control system neurons and peripheral stimuli
from chemoreceptors and mechanoreceptors contribute to
the control of minute ventilation gradually increasing to a
steady level.
•
Phase III Ventilation: “Fine tuning” of ventilation through
peripheral sensory feedback mechanism
Phase I Ventilation: Neurogenic stimuli from the cerebral
cortex and active limbs cause the initial, abrupt increase in
breathing when exercise begins.
Integrated Regulation (Cont.)
Ventilation During Steady-Rate
Exercise
•
Ventilatory equivalent for oxygen (VE/VO2)
 Ratio of minute ventilation to oxygen uptake
 Remains relatively constant during steady-rate exercise
•
Ventilatory equivalent for carbon dioxide (VE/VCO2)
 Ratio of minute ventilation to oxygen produced
 Remains constant during steady-rate exercise because pulmonary
ventilation eliminates the carbon dioxide produced during cellular
respiration
Ventilatory Threshold
•
The point at which pulmonary ventilation increases
disproportionately with oxygen uptake during graded
exercise.
•
Relates directly to carbon dioxide’s increased output
from the buffering of lactate that begins to accumulate
from anaerobic metabolism.
Ventilatory Threshold (Cont.)
Onset of Blood Lactate Accumulation
(OBLA)
•
Indicated by the eventual sharp upswing in pulmonary
ventilation related to oxygen uptake during incremental
exercise
•
Implies an imbalance between the rate of blood lactate
appearance and disappearance
•
Occurs between 55-65% of VO2max in healthy, untrained
subjects and often equals more than 80% VO2max in highly
trained endurance athletes
•
The point of OBLA often increases with aerobic training,
without an accompanying increase in VO2max.
Onset of Blood Lactate Accumulation
(OBLA) (Cont.)
Work of Breathing
•
Breathing normally requires a relatively small oxygen cost
even during exercise.
•
In respiratory disease, the work of breathing becomes
excessive, and exercise alveolar ventilation often becomes
inadequate.
•
Factors that determine the energy requirements of
breathing:


Compliance of lungs and thorax
Resistance of airways to the smooth flow of air
Buffering
•
•
Buffers consist of a weak acid and the salt of that acid.
•
The lungs also contribute to pH regulation through
changes in alveolar ventilation that rapidly alter free H+
concentration in extracellular fluids.
•
The renal tubules act as the body’s final defense by
secreting H+ into the urine and reabsorbing bicarbonate.
•
Anaerobic exercise increases the demand for buffering,
and makes pH regulation progressively more difficult.
The bicarbonate, phosphate, and protein chemical
buffers provide the rapid first line of defense in acidbase regulation.
Buffering (Cont.)
The End