PULMONARY PHYSIOLOGY

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PULMONARY PHYSIOLOGY

• Gary L. Weinstein M.D.
• Director of Pulmonary and Critical Care Medicine
• Presbyterian Hospital of Dallas

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Physiology for Dummies

• Good Air In, Bad Air Out

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Physiology for Psychologists

• Take Slow, Deep, Cleansing Breaths

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Physiology for Internists

• Remember (review ?) your little orange book from
  1st year med school on Respiratory Physiology by
  Dr. West
• You MUST understand normal physiology to
  understand abnormal physiology
• You may BORROW my tape on normal lung sounds
  (especially if you have insomnia)

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Physiology

• The respiratory system is composed of
• the conducting airways (nose, mouth, larynx,
  trachea, bronchial tree)
• the lungs (terminal bronchioles, alveoli)
• the parts of the CNS concerned with control of
  the system (pons, medulla, cortex, Vagus)
• the chest wall (muscles of respiration, rib cage)

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Physiology

• Functions of the respiratory system include
• O2 extraction from the external environment
• CO2 elimination from the body
• maintenance of acid-base balance (along with
  other TRIVIAL organs)
• phonation
• defense from the outside world
• metabolism (e.g. ACE I ACE II)

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Physiology
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Physiology
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Physiology

• Defense each day about 10,000 liters of air is
  inspired along with dust, pollen, ash,
  microorgansims, toxic gases, particulates
• Jobs include
• air conditioning - by the time air reaches the
  alveoli, it is at body temp and 100 humidified
• olfaction - a shallow sniff bring air to the nose
  but not to the lung allowing retreat

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Physiology

• Jobs (contd)
• filtration
• nasal hairs trap 10 - 15 um particles
• in addition, particles gt 10 um impact onto the
  septum and turbinates as well as the nasopharynx
• tonsils and adenoids provide immunologic defense
  against biologically active materials
• particles 2 - 5 um sediment via gravity in the
  smaller airways and become trapped in the mucous
  that lines the airways, then are transported up
  and out
• particles 0.1- 0.5 um mainly stay suspended as
  aerosols and about 80 of them are exhaled

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Physiology
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Physiology
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Physiology
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Physiology
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Physiology
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Physiology
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Physiology
Control of Ventilation Central Controller Pons,
medulla, ... Input
output Sensors Effectors Chemorecepto
rs, Respiratory muscles lung and other
receptors
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Physiology
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Physiology

• Lung and other receptors
• 1) pulmonary stretch receptors
• lie within the airway smooth muscle
• impulses travel in the vagus nerve
• result in a slowing of respiratory rate
  
• 2) irritant receptors
• lie between airway epithelial cells
• stimulated by noxious gases, cigarette smoke,
  inhaled dusts and cold air
• impulses travel up the vagus and the reflex
  effects include bronchoconstriction and hyperpnea

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Physiology

• 3) J receptors (juxta-capillary)
• impulses pass up the Vagus and result in rapid,
  shallow breathing
• may play a role in the dyspnea a/w left heart
  failure and ILD
• 4) Nose and upper airway receptors
• respond to mechanical and chemical stimulation
  with sneezing, coughing and bronchoconstriction

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Physiology

• 5) Joint and muscle receptors
• Impulses from moving limbs are believed to be
  part of the stimulus to ventilation during
  exercise

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Physiology

• Fun Facts
• Alveolar surface area is 50-100 square meters
• There are approx. 300 million alveoli, each 1/3
  mm in diameter
• The blood-gas interface is approx. 0.5 microns
• O2 and CO2 move by simple diffusion
• Anatomic dead space is approx. 1 ml/lb. body wt
• Each RBC spends about 1 sec in the capillary
  network and transverses 2 - 3 alveoli
• Surfactant, made by type II pneumocytes,
  dramatically lowers alveolar surface tension