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Respiratory Mechanics

Pulmonary Ventilation
1. Inspiration & Expiration
2. Volume change of thoracic cavity and lungs
  1. Boyle's Law P~1/V
Quiet Breathing
1. Diaphragm: Increase thoracic volume
2. External Intercostal: raise ribs and increase thoracic volume
3. Expiration: passive recoil (elastin)
Deep Breathing
1. Inhalation
2. Scalene, Sternocleidomastoid
  1. Raise ribs and increase thoracic volume
3. Expiration
  1. Internal intercostal & abdominals
What controls breathing factors
1. Medulla Respiration Centers
  1. Brainstem
  2. Starts at the Medulla Oblongata (NTS)
  3. Basic breathing rhythm
  4. if medulla destroyed you will have trouble breathing
2. Pons Respiratory Centers
  1. Influence breathing rhythm
  2. Two respiratory centers
    1. Apneustic Center
      1. Stimulates inspiratory neurons of the medulla
      2. Makes breathing increases
    2. Pneumotaxic Center
      1. Antagonizes apneustic center
        Reduction of Breathing
3. Peripheral and Central Chemoreceptors
  1. Influenced breathing rhythm (rate and depth)
  2. Sensitive to blood CO2, O2 and pH
  3. Location
    1. Medulla Oblongata CENTRAL
    2. Aortic and carotid bodies (PERIPHERAL)
Phrenic nerve innervates the diaphragm
Intercostal nerves innervates the intercostal muscles
Chemoreceptors Mechanism
1. Central Chemoreceptors
  1. Greatest effect on Ventilation
  2. BBB impermeable to H+ bond enters CSF (lowest pH)
  3. Formation of H2CO3 by carbonic anhydrase
  4. H+ activates central chemoreceptors
2. Peripheral Chemoreceptors
  1. Respond to blood pH levels
3. Most sensitive to PCO2 & pH
  1. PCO2 influence blood pH
4. Hyperventilation
  1. Low CO2 (HYPOCAPNIA)
5. Hypoventilation
  1. Low CO2 (HYPERCAPNIA)
6. Adjusted to maintaIn 40mmHg PCO2
Effects of blood PO2 on Ventilation
1. low blood PO2 (Hypoxamia) has little affect on ventilation
  1. Blood PO2 ust decrease from 100 mmHg to 50 mmHg to influence ventilation
Cerebral Cortex
1. Voluntary override
  1. Breath hold
    1. Panting
      1. Sighing
        Emotions
Other Ventilation Regulatory Mechanisms
1. Proprioreceptors
  1. Temperature and pain receptors
    1. Irritant receptors
      1. Rapidly adapting respond to smoke smog and particulates
        Causes cough sneezing bronchoconstriction
2. Hering-Stretch receptors activated during inspiration
  1. Located in smooth muscle of airways
    1. Inhibits respiratory centers to prevent overinflation of lungs
Assessing Pulmonary function
1. Spirometry
  1. Tidal volume amount of air expired/breath
  2. Tidal capacity: amount of air forcefully exhaled after a maximum inhalation
    1. TV+IRV+ERV
      1. Tv=tidal volume
        Volume of gas inspired or expired in a unforced respiratory cycle
      2. IRV=Inspiration Reserve Volume
        Maximum volume of gas that can be inspired during forced breathing in addition
      3. ERV= Expiration reserve volume
        Maximum volume of gas that can be expired during forced breathing in addition
Terms
1. ANATOMICAL DEAD SPACE
  1. air in conducting Zone
2. FORCED EXPIRATORY VOLUME )FEV1)
  1. Air exhaled in forced breath in 1 second
3. FORCED VITAL CAPACITY
  1. Total amount of air exhaled in FEV test

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Respiratory Mechanics

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