Pulmonary Anatomy and Physiology

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Pulmonary Anatomy and Physiology

• Ventilation Movement of air in and out of the
  lungs
• Respiration Process of gas exchange with the
  blood

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Thorax

• Thoracic cage
• Lungs
• Total volume 3.5-8.5 liters
• Lobes and segments
• Mediastinum
• Pleura visceral and parietal
• Negative pressure

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Muscles of Ventilation

• Inhalation Major muscle is diaphragm
• Exhalation Passive recoil of lung
• Accessory muscles enhance ventilation

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Conducting Airways

• Upper airways Warm, humidify and cleanse
  air
• Epiglottis Protects opening to the trachea
• Trachea
• 16-20 C-shaped rings to prevent tracheal collapse

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Bronchial Tree

• Differences in mainstem bronchi
• Bronchi branching of bronchi increases number of
  bronchi and increases surface area despite
  decreases in diameter
• Bronchioles Diameter of lt1mm in size
• Terminal bronchioles

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Defense System

• Mucociliary escalator (mucous blanket) cleanses
  air and traps material to be moved out of the
  lungs to be expectorated or swallowed
• Cough reflex

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Respiratory Airways (Terminal Respiratory
Units/Acini)

• Respiratory bronchioles Conducting airways and
  some gas exchange
• Alveoli
• Type 1 alveolar epithelial cells Gas exchange
• Type 2 alveolar epithelial cells Produce, store
  and excrete surfactant to stabilize the alveoli,
  increase lung compliance, and ease the work of
  breathing

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Ventilation

• Ventilation Created by pressure changes
• Inhalation Active
• Exhalation Usually passive
• Work of breathing
• Restrictive lung diseases
• Obstructive lung diseases

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Pulmonary Volumes and Capacities

• Ventilation/perfusion
• Physiologic dead space
• Anatomic dead space
• Alveolar dead space

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Regulation of Ventilation

• Brain stem
• Cerebral cortex Voluntary controls

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Respiration

• External respiration
• Diffusion of oxygen and carbon dioxide
• Driving pressures of gases
• Thickness of alveolar membrane
• Surface area
• Internal respiration

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Ventilation/Perfusion V/Q

• DEAD SPACE airways not participating in gas
  exchange (there are airways or alveoli with air
  but no blood vessels to exchange gases with)
• SHUNTING blood not participating in gas exchange
  (there are blood vessels but no contact with air
  filled alveoli to exchange gases with)

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• Ventilation usually approximately equals the rate
  of perfusion normal V/Q ratio is 0.8 (if they
  were exactly equal the ratio would be 1/1 or 1).
• If ventilation exceeds blood flow, the ratio is
  greater than 0.8 (V is greater than Q)
• If ventilation is less than blood flow, the ratio
  is less than 0.8 (V is less than Q)

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Ventilation/Perfusion Mismatching

• Alveolar dead space V/Q gt 0.8 (e.g. from
  pulmonary embolus)
• Intrapulmonary shunting V/Q lt 0.8
• (e.g. from mucous plug in airway)
• Hypoxic vasoconstriction
• PaO2 lt 60 in poorly ventilated alveoli
• Compensatory mechanism

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Gas Transport To and From Tissue Cells

• Oxygen content
• Oxyhemoglobin dissociation curve
• Shifting of curve by temperature, pH, PaCO2,and
  2, 3, DPG
• Shift to the right (better)
• Shift to the left
• Abnormalities of hemoglobin
• Carbon dioxide content

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Oxyhemoglobin
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Oxyhemoblobin dissociation curve
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Oxyhemoglobin dissociation curve
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Oxyhemoglobin dissociation curve
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Oxyhemoglobin dissociation curve

• Right shift
• Acidosis
• Hyperthermia
• Hypercarbia
• Increased 2,3-DPG
• Left shift
• Alkalosis
• Hypothermia
• Hypocarbia
• Decreased 2,3-DPG