RESPIRATORY PHYSIOLOGY Anatomy review

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RESPIRATORY PHYSIOLOGYAnatomy review
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Pressures

• Atmospheric pressure
• Alveolar pressure (intrapulmonary pressure)
• Intrapleural pressure
• Boyles Law
• More volumeless pressure
• Less volumemore pressure

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• Diaphragm is chief respiratory muscle (80)
• Intercostal muscles are secondary (20)
• - Diaphragm is controlled by phrenic nerve
  (C3,4,5)
• - Range of movement from 1 cm (normal breathing)
  to 10cm in heavy breathing.
• Parietal pleura attaches to diaphragm
• Visceral pleura attaches to parietal pleura (thin
  space in b/w filled with serous fluid)
• Lungs attach to visceral pleura.

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• Inspiration
• Before inspiration pressure in lung equals
  atmospheric pressure 760 mm Hg or 1 atm
• Increasing the size of the lungs will cause
  pressure to drop and air to rush in. How does
  lung increase in size?
• Boyles law the pressure of a gas in a closed
  container is inversely proportional to the volume
  of the container.
• - incr. in size of container pressure will
  decrease pressure..
• Intrapleural pressure is 756 mm Hg and during
  inspiration (as diaphragm is pulling down)
  pressure drops to 754 mm Hg.
• External intercostals contract and pull rib cage
  up and forward (anterior) causing a-p diameter to
  increase.

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• When volume increases, pressure inside lung
• (alveolar, intrapulmonic pressure) drops from
  760 to 758. A pressure gradient is established
  between the atmosphere and the alveoli.
• Air rushes in (pressure gradient) to alveoli from
  atm.
• Expiration pressure in lungs is greater than
  atm.
• - diaphragm relaxes and dome shape muscle pushes
  up (elasticity). Internal intercostals cause a-p
  diameter to decrease
• - lung pressure increases to 762. Air will flow
  from higher to lower pressures.

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Thoracic Volume and Inspiration
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Thoracic Volume and Expiration
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Changes in Thoracic Volumes
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Factors Influencing Pulmonary Ventilation

• Airway Resistance
• Amount of drag air encounters in respiratory
  passageways not significant since airway
  diameters are large and at terminal bronchioles
  gasses travel by diffusion
• Surface Tension
• At gas-liquid boundaries, liquids are more
  attracted to each other (cohesiveness), surfacant
  at the alveoli keeps water from being cohesive
  and allows alveoli to be more functional (less
  energy needed for breathing)
• Lung Compliance
• The distensibility of the lungs, ability to
  stretch higher compliance leads to better
  ventilation (fibrosis, airway blockages,
  decreased surfacant, and decreased thoracic cage
  flexibility lead to less compliance)

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Respiratory Volumes and Capacities
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Respiratory Volumes

• Tidal Volume
• The amount of air that moves in and out of the
  lungs with a normal breath at rest (500 mL)
• Inspiratory Reserve Volume
• The amount of air that can be inspired forcibly
  beyond the tidal volume (2100-3200 mL)
• Expiratory Reserve Volume
• The amount of air that can be expired forcibly
  beyond a tidal expiration (1000-1200 mL)
• Residual Volume
• The amount of air remaining in the lungs even
  after the most forceful expiration (1200 mL)

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Respiratory Capacities

• Inspiratory Capacity
• Total amount of air that can be inspired after a
  tidal expiration TV IRV
• Functional Residual Capacity
• Total amount of air remaining in lungs after a
  tidal expiration ERV RV
• Vital Capacity
• Total amount of exchangeable air TV IRV ERV
• Total Lung Capacity
• Sum of all lung volumes

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Volumes and Capacities
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Dead Space

• Anatomical dead space
• The volume of air found in the conduits of the
  respiratory system NOT involved in gas exchange
• Alveolar dead space
• Regions where alveoli cease to function due to
  collapse or obstruction
• Total dead space
• Alveolar dead space Anatomical dead space

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Non-Respiratory Air Movements

• Cough
• Sneeze
• Crying

• Laughing
• Hiccups
• Yawn

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Regulation of Respiration

• Medullary respiratory center
• Dorsal respiratory center (DRC)
• Ventral respiratory center (VRC)
• Pontine center
• formerly called the Pneumotaxic center
• Hypothalamus

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Gas Transport

• Oxyhemoglobin HbO2
• Deoxyhemoglobin HHb
• Carbaminohemoglobin HbCO2
• External Respiration
• Oxygen and Carbon Dioxide concentration is
  measured as a unit of pressure called partial
  pressure (p)
• Blood coming into the lungs (pulmonary
  artery-capillary) is deoxygenated blood PO2 is
  40 mm Hg. PCO2 is 45 mm Hg

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• Air in the alveoli
• PO2 105 mm Hg
• PCO2 40 mm Hg
• Oxygen and Carbon dioxide are highly fat soluble
  and can diffuse through membranes with ease.
• As gases pass from the blood pass an alveolus
  gases will diffuse from areas of higher
  concentration to lower. (diffusion gradients)
• PO2 in blood after passing alveolus is 105 mm Hg
• PCO2 in blood after passing alveolus is 40 mm Hg

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• Internal respiration Exchange of gases in the
  tissues.
• CO2 is a byproduct of cellular metabolism.
• PCO2 in tissue space 45 mm Hg
• PO2 in tissue spaces 40 mm Hg
• O2 will diffuse into tissue spaces (105) and CO2
  will diffuse into blood (45)

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Gas Transport at the Tissues

• Carbon dioxide transported to and from the lungs
  and tissues in three ways
• Dissolved in plasma 7
• Chemically bound to hemoglobin (carbaminohemoglobi
  n) 23
• As Bicarbonate in plasma (Reaction between carbon
  dioxide and water, catalyzed by carbonic
  anhydrase) ? pH buffer system. 70 of CO2 is
  transported this way.
• Chloride shift (Chloride anions diffuse into RBCs
  to counteract bicarbonate anions leaving RBCs)
• Process results in diffusion of Oxygen from RBC
  to tissues and from Carbon dioxide from tissues
  to RBCs
• This process is reversed in the Lungs

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At the Lungs
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At the Tissues
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Oxygen Transport

• Molecular oxygen carried in blood or bound to
  hemoglobin
• HbO2- hemoglobin bound to oxygen
• HHb O2 --? HbO2 H
• Hb can bind 4 oxygens after first binding, there
  is a higher affinity for other 3
• Hemoglobin is fully saturated when all 4 heme
  sites bound to oxygen

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Clinical corner

• Eupnea - quiet breathing
• Tachypnea - rapid breathing
• Costal breathing - shallow Diaphragmatic
  breathing - deep Atelectasis - collapse or
  incomplete expansion of lungs
• Cheyne-Stokes respiration - irregular breathing
  (increase/decrease in depth and rapidity)

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• Laryngitis - inflammation of the vocal cords
• Pleurisy - inflammation of the pleura Infant
  respiratory distress syndrome (IRDS) -
  insufficient surfactant produced, surface tension
  forces collapse of the alveoli
• Hypoxia - inadequate amount of oxygen is
  delivered to body tissues anemic - to few RBCs,
  or RBCs with inadequate hemoglobin stagnant -
  blood circulation is impaired or blocked
  interference with gas exchange
• Hypercapnia - apnea (breathing cessation)
  increase in carbon dioxide levels in
  cerebrospinal fluid, causing pH to decrease,
  exciting chemoreceptors to increase rate of
  breathing (compensating)
• Hypocapnia- low levels of CO2 in plasma and CSF
  due to depth and rate of breath increase
  (hyperventilation)

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• Chronic Obstructive Pulmonary Disease (COPD),
  common features
• 1- Patients with history of smoking
• 2- Dyspnea - difficult or labored breathing
• 3- Coughing and frequent pulmonary infection
• 4- Will develop respiratory failure
• COPDs Obstructive emphysema - permanent
  enlargement of the alveoli, deterioration of
  alveolar walls
• Chronic inflammation leads to lung fibrosis
  (lungs lose their elasticity)
• Victims sometimes called "pink puffers" -
  breathing is labored, but doesn't become cyanotic
  because gas exchange remains adequate until late
  in the disease
• Chronic bronchitis - inhaled irritants lead to
  chronic excessive mucus production by the mucosa
  of lower respiratory passageways and inflammation
  and fibrosis of that mucosa
• Victims sometimes called "blue bloaters" -
  hypoxia and carbon dioxide retention occur