Download Respiratory Regulation During Exercise

Respiratory Regulation
During Exercise
Pulmonary Ventilation

Respiratory System Anatomy
(fig.
9.1)

Pulmonary Ventilation
– commonly referred to as breathing
– process of moving air in and out of the
lungs
– nasal breathing: warms, humidifies, and
filters the air we breathe
– pleural sacs suspend the lungs from the
thorax and contain fluid to prevent friction
against the thoracic cage.
Pulmonary Ventilation

Inspiration
– is an active process of the diaphragm and
the external intercostal muscles.
– air rushes in into the lungs to reduce a
pressure difference.
– forced inspiration is further assisted by
the scalene, sternocleidomastoid, and
pectoralis muscles.

Expiration
– is a passive relaxation of the inspiratory
muscles and the lung recoils.
– increased thoracic pressure forces air out
of the lungs
– forced expiration is an active process of
the internal intercostal muscles
(latissimus dorsi, quadratus lumborum &
abdominals).
Pulmonary Diffusion

Is the gas exchange in the lungs
and serves two functions:
– it replenishes the blood’s oxygen supply in
pulmonary capillaries
– it removes carbon dioxide from the
pulmonary capillaries

The respiratory membrane (fig.
9.4)
– gas eschange occurs between the air in the
alveoli, through the respiratory membrane,
to the red blood cells in the blood of the
pulmonary capillaries.
Pulmonary Diffusion

Partial Pressures of gasses
– the individual pressures from each gas in
a mixture together create a total pressure.
– air we breathe = 79% (N2), 21% (O2),
and .03% (CO2) = 760mmHg
– differences in the partial pressures of the
gases in the alveoli and the gases in the
blood create a pressure gradient. (fig.
9.5, 9.6)
Pulmonary Diffusion

Oxygen’s rate at which it diffuses
from the alveoli int the blood is
referred to as the oxygen
diffusion capacity.
– untrained (45 ml/kg/min) vs trained (80
ml/kg/min)
 due to increased cardiac output,
alveolar surface area, and reduced
resistance to diffusion across the
respiratory membranes.
– large athletes (males) vs small athletes
(females)
 due to increased lung capacity,
increased alveolar surface area, and
increased blood pressure from muscle
pumping.
Pulmonary Diffusion

Carbon dioxide’s membrane
solubility is 20 times greater than
that of oxygen, so CO2 can
diffuse across the respiratory
membrane much more rapidly.
Transport of Oxygen By
The Blood


Dissolved in the blood plasma
(2%)
Dissolved with hemoglobin of red
blood cells (98%)
– complete hemaglobin saturation at sea
level is 98%.
– many factors influence hemoglobin
saturation (fig. 9.7)
Po2 values (fig. 9.7a)
 decline in pH level from increasing lactate
levels allows more oxygen to be unloaded and
higher Po2 is needed to saturate the
hemaglobin. (fig. 9.7b)
 increased blood temperature allows oxygen to
unload more efficiently and higher Po2 is
needed to saturate the hemaglobin. (fig. 9.7c)
 anemia reduces the blood’s oxygen-carrying
capacity.

Athletes

Athletes with larger aerobic
capacities often also have
greater oxygen diffusion
capacities due to increased
cardiac output, blood pressure,
alveolar surface area, and
reduced resistance to diffusion
across respiratory membranes.
Transport of Carbon
Dioxide in the Blood

CO2 released from the tissues is
rarely (7%) dissolved in plasma.

CO2 combines with H2O, then loses a
H+ ion to form a bicarbonate ion
(HCO3) and transports 70% of carbon
dioxide back to the lungs.
– the lost H+ binds to hemoglobin which
enhances oxygen unloading
– sodium bicarbonate as an ergogenic aid
serves the same purpose as a buffer and
neutralizer of H+ preventing blood
acidification.

CO2 can also bind with the amino
acids of the hemoglobin to form
carbaminohemoglobin and is
transported to the lungs.
Gas Exchange at the
Muscles

The arterial-venous oxygen
difference
(fig. 9.8, 9.9)
– as the rate of oxygen use increases, the
a-vO2 difference increases.

Factors influencing oxygen
delivery and uptake
– under normal conditions hemoglobin is
98% saturated with O2.
– increased blood flow increases oxygen
delivery and uptake
 because of increased muscle use of
O2 and CO2 productions
 because of increased muscle
temperature (metabolism)
Gas Exchange at The
Muscles

Carbon dioxide exits the cells
by simple diffusion in response
to the partial pressure gradient
between the tissue and the
capillary blood.
Regulation of
Pulmonary Ventilation

Mechanisms of pulmonary
ventilation (fig. 9.10)
– controlled by respiratory centers of the
brainstem by sending out periodic
impulses to the respiratory muscles.
– chemoreceptors also stimulate the brain to
stimulate the respiratory centers to
increase respiration to rid the body of
carbon dioxide.
– stretch receptors of the pleurae,
bronchioles and alveoli send impulses to
the expiratory center to shorten
inspiration.
– the motor cortex of the voluntary nervous
system can control ventilation but can also
be overriden by the involuntary system.
Regulation of
Pulmonary Ventilation


The goal of respiration is to
maintain appropriate levels of
the blood and tissue gases and
to maintain proper pH for
normal cellular function.
Exercise pulmonary ventilation
(fig. 9.11)
– the anticipatory response creates a preexercise breathing increased depth &
rate of ventilation.
– gradual exercise ventilation increases
occur due to temperature and chemical
status.
– respiratory recovery creates a slow
decreased ventilation during postexercise breathing.
Regulation of
Pulmonary Ventilation

Respiratory problems hinder
performance
– Dyspnea is difficulty or labored
breathing from poor conditioning of the
respiratory muscles.
– Hyperventilation is a sudden increase in
ventilation (mainly expiration) that
exceeds the metabolic need for oxygen.
 pre-exercise hyperventilation creates
CO2 unloading (swimmers).
 Valalva maneuver occurs when air is
trapped in the lungs which restricts
venous return, and cardiac output.
Ventilation and Energy
Metabolism

Ventilatory Equivalent for
Oxygen
– is the ratio of volume of air ventilated
and the amount of oxygen consumed by
the tissues Ve/Vo2 (fig. 9.12).
– the control systems for breathing keep
the Ve/Vo2 relatively constant to meet
the body’s need for oxygen.

Ventilatory Breakpoint
– is the point at which ventilation
increases disproportionately to the
oxygen consumption of the tissues to
try to clear excess CO2.
– this usually occurs at 55% to 70% of
Vo2 max and correlates to anaerobic
threshold and lactate threshold.
Ventilation and Energy
Metabolism

Ventilatory Equivalent for
Carbon Dioxide
– is the ratio of air ventelated to the
amount of CO2 produced.
– anaerobic threshold is measured by an
increase in Ve/Vo2 without an increase
in Ve/Vco2
(fig. 9.13).
Respiratory Limitations
to Performance

Energy produced by oxidation and used by
the respiratory muscles increases from 2% to
15% during heavy exercise.
 Pulmonary Ventilation might be a limiting
factor in highly trained subjects during
maximal exhaustive exercise due to a high Vo2
max.
 Airway Resistance and Gas Diffusion in
the lungs do not limit exercise in a normal
healthy individual.

Restrictive or Obstructive Air Ways can
limit athletic performance by decreasing the
Po2 or increasing the Pco2.
– asthma
– bronchitis
– emphasema
Respiratory Regulation
of
Acid-Base Balance

Chemical Buffers
– bicarbonate, phosphates, and proteins
 baking soda as an ergogenic aid to
buffer
– increased ventilation to decrease H+
– accumulated H+ is removed by the
kidneys and urinary system
– H+ is difussed throughout the body
fluids and reach equilibrium after only
5 to 10 minutes of recovery
 this is facilitated by active recovery
(fig. 9.15).
Static Lung Volumes








Total Lung Capacity
Tidal Volume
Inspiratory Reserve Volume
Expiratory Reserve Volume
Residual Lung Volume
Forced Vital Capacity
Inspiratory Capacity
Functional Residual Volume