Respiratory Physiology the Ins and Outs

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Respiratory Physiologythe Ins and Outs

• Jim Pierce
• Bi 145b
• Lecture 3, 2008-09

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Pulmonary Perfusion

• The right heart pumps blood to the lungs
• The left heart pumps blood to the body
• What is different about
• the Pulmonary Circulation?

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Pulmonary Perfusion

• The Cardiac Output is the same
• The Pressures are different
• Therefore, the Pulmonary Vascular Resistance is
  different
• (Resistance independent variable)
• (Pressure dependent variable)

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Pulmonary Blood Flow
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Pulmonary Perfusion

• The macrovasculature is different
• The large arteries and veins are held open by
  elastic forces from the lung
• The large vessels are exposed to transthoracic
  pressure

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Pulmonary Perfusion

• The microvasculature is different
• There is a richer network of capillaries in the
  lung parenchyma
• The lung microvasculature is exposed to alveolar
  pressure

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Pulmonary Blood Flow
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Pulmonary Blood Flow
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Pulmonary Blood Flow
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Pulmonary Blood Flow
What aboutcompensation When there isan acute
changein pressure?
If something elsetries to raise pressure The
resistance drops!
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Pulmonary Blood Flow
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Pulmonary Blood Flow
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Pulmonary Perfusion

• There are regional differences
• in blood flow
• The lung is a column of blood
• Blood tends to follow gravity

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Pulmonary Blood Flow
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Pulmonary Ventilation
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Pulmonary Ventilation
Compare and Contrast
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Ventilation and Perfusion
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Pulmonary Blood Flow
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Pulmonary Blood Flow
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Pulmonary Blood Flow
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Pulmonary Blood Flow

• Alveolar Pressure is not the only way that the
  alveoli affect pulmonary blood flow
• Alveolar gas concentration affects it, too.

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Pulmonary Blood Flow
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Interstitial Fluid Flow
Lymphatic Flow
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Interstitial Fluid Flow
Lymph is produced in the usual fashion Too much
can fill up the alveolar membrane!
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Perfusion

• Blood flows to the lung throughthe Pulmonary
  Artery
• Blood exits the lung through the Pulmonary Veins

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Perfusion

• The properties of the vessels are affected by
  gravity and thoracic pressure
• Macrovasculature is held open bylung parenchyma
  and squeezed bythoracic pressure
• Microvasculature function is affectedby rate of
  interstitial flow (lymph)

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Ventilation Perfusion Matching

• We have seen that proper gas exchange depends on
  both ventilation and perfusion
• How do we make sure that each lung unit is both
  ventilated and perfused?

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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Ventilation Perfusion Matching
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Shunt
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Shunt
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Ventilation Perfusion Matching

• How do we match ventilation and perfusion?

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Ventilation Perfusion Matching

• When a lung is not ventilated, the pAO2 falls
• Then, the vasculature constricts
• Then, the perfusion decreases

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Ventilation Perfusion Matching

• When a lung is not perfused, the pACO2 falls
• This causes bronchoconstriction
• This leads to decreased ventilation.

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Ventilation Perfusion Matching

• Thus, VQ matching is based on
• Airways and the vessels sending air and blood
  away from mismatched areas.

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Ventilation Perfusion Matching

• This is a great system to compensate for a focal
  problem (like pneumonia)
• It can be dangerous, however

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Ventilation Perfusion matching

• If there is a global problem with ventilation or
  perfusion, the whole lung tries to send air or
  blood elsewhere.
• This is a problem.
• ARDS

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Pulmonary Function

• How do we adjust pulmonary function to compensate
  for changes in the periphery?

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Pulmonary Function

• Ultimately, the job of the cardiopulmonary system
  is to deliver oxygen to the periphery
• As oxygen is used by the periphery, carbon
  dioxide is returned.

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Pulmonary Function

• The cardiovascular system is responsible for
  delivering the oxygen to the periphery.
• The periphery is responsible for extracting
  oxygen from the blood
• The venous blood carries the resulting carbon
  dioxide back to the lung
• The pulmonary system, then, needs to compensate
  to excrete that carbon dioxide.

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CardioPulmonary Control
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Pulmonary Function

• How do we increase the delivery of oxygen to the
  periphery?
• DO2 CartO2 CO
• CO HR SV
• CO BP / SVR

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Pulmonary Function

• Why doesnt an increase in the CO cause a
  decrease in the oxygenation of the blood?

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Pulmonary Function
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Pulmonary Function

• Answer
• Built-in Reserve

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Pulmonary Function

• What kinds of Carbon Dioxide stresses do we need
  to deal with?
• Increased / Decreased production of CO2
• pH abnormalities affecting CO2 excretion

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Pulmonary Function

• There are two types of protons carried in the
  blood
• Volatile acids that result from CO2 conversion
  to bicarbonate and protons
• Non-volatile acids that result from proton
  dissociation from other molecules (lactic acid,
  protein metabolism)

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Respiratory Acid-Base Balance
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Respiratory Acid-Base Balance
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Pulmonary Function

• To increase the disposal of CO2 and remove
  volatile protons, we simply increase alveolar
  ventilation
• Minute Ventilation
• Respiratory Rate Tidal Volume

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Pulmonary Function

• Increased production of CO2 and volatile acid
  occurs primarily because of a change in metabolic
  substrates to fats

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Pulmonary Function

• What about pH problems not related to carbon
  dioxide?
• They can occur by two mechanisms
• 1) the wrong number of protons
• 2) the wrong amount of buffer

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Pulmonary Function

• The wrong number of protons can happen for a
  variety of reasons
• Too many made (lactic acid, protein metabolism)
• Too many lost (vomiting stomach acid, renal
  losses)
• Not enough lost (renal failure)

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Pulmonary Function

• The wrong amount of buffer can happen for two
  reasons
• Too much buffer (ingestion of alkali, infusion of
  buffer)
• Too little buffer (loss of buffer with diarrhea,
  loss of buffer through kidney)

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Pulmonary Function

• Since pH changes can affect cellular respiration
  and CO2 excretion, the lung must be able to
  compensate for pH changes.
• Ventilation changes cause pCO2 changes
• pCO2 changes cause pH changes

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Pulmonary Function

• A high pH is called an alkalemia
• A low pH is called an acidemia
• A particular derangement that causes an increase
  in pH is called an alkalosis
• A particular derangement that causes a decrease
  in pH is called an acidosis.

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Pulmonary Function

• If an acidosis or alkalosis is caused by changes
  in ventilation, it is called a Respiratory
  acidosis/alkalosis
• If is not caused by ventilation, then it is
  called a Metabolic acidosis/alkalosis

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Respiratory Acid-Base Balance
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Pulmonary Function

• As we will see in acid-base physiology, the lung
  compensates for pH changes by changing
  ventilation and therefore changing pCO2

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Questions?