Respiratory Regulation During Exercise

1
Respiratory Regulation During Exercise

2
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.

3
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).
  

4
Pulmonary Diffusion

• Is the gas exchange in the lungs and serves two
  functions
  
• it replenishes the bloods 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.

5
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)
  

6
Pulmonary Diffusion

• Oxygens 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.

7
Pulmonary Diffusion

• Carbon dioxides membrane solubility is 20 times
  greater than that of oxygen, so CO2 can diffuse
  across the respiratory membrane much more
  rapidly.

8
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 bloods oxygen-carrying
  capacity.

9
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.

10
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.

11
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)

12
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.

13
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.

14
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 pre-exercise
  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 post-exercise breathing.

15
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.
  

16
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 bodys 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.

17
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).
  

18
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

19
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).

20
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