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CVPR: Pulmonary > Ventilation > Flashcards

Flashcards in Ventilation Deck (17)
1

Ventilation (general) definition

  • amount of air-flow in the lungs

2

Minute ventilation vs. Alveolar ventilation

  • minute = volume of air that flows into or out of the lung in one minute
    • @ rest ≈ 6L
  • alveolar = volume of air that flows into or out of the alveolar spance in one minute

    • @ rest ≈ 4.2L
       

  • minute is always > alveolar b.c it includes alveoli + conducting paths

3

Factors that impact alveolar ventilation

  1. bronchodilators/constrictors
  2. exercise
  3. altitude
  4. obstructive/restrictive diseases
  5. gravity

4

Excercise impact on alveolar ventilation

  • moderate excerise ==> ~10x increase in ventilation

5

Bronchodilators/contrictors impact on alveolar ventilation

  • bronchodilators ==> increased ventilation
  • bronchoconstrictors ==> decreased ventilation

6

Obstructive/restrictive disease impact on alveolar ventilation

  • reduces ventilation by incresing airway resistance and/or altering lung compliance
    • e.g. emphysema
  • in mild-moderate, overal ventilation may stay the same but w/regional reductions and increases elsewher

7

Gravity impact on alveolar ventilation

  • contributes to regional differences in ventilation
  • | PIP @ apex | > | PIP @ base | ==> larger volumes ==> more poorly ventilated (b/c alveoli are less compliant at high volumes)
  • reduced compliance @ apex ==> smaller change in volume vs. @ base ==> base ventilates 2.5x more than apex

8

Factors that impact work of breathing

  • work of breathing ≈ "work" done by respiratory muscles on lungs
  • increased work of breathing occurs b/c:
    1. increase in elastic recoil (decreased compliance)
    2. increase in airway resistance
    3. combination of #1 & #2

9

Changes in work of breathing at high/low tidal volumes

  • @ low tidal volumes: elastic work is small, but resistance work is large (high frequency of breaths = smaller lung volumes)
  • @ high tidal volumes: elastic work is large, but resistance work is small 

10

Dead-space characteristics

  • ~150ml out of 500ml or air/breath remains in conducting path ==> "anatomic dead-space"
  • "alveolar dead-space" = well-ventilated but don't exchange gas
    • occur @ unperfused regions of lung
  • "physiologic dead-space" = anatomic + alveolar
    • @ healthy ppl ==> anatomic ≈ physiologic
    • large difference btwn physiologic and anatomic ==> disease

11

Residual volume/functional residual capacity definition

  • RV=volume or air remaining in lungs after maximal expiration
    • RV = ~1.5L
  • FRC=volume of gas present in lung/upper airways @ end of normal expiration
    • FRC = ~2.5L

12

Total lung capacity definition

  • TLC = volume of air inside lungs @ maximal inspiration
  • TLC = ~7.5L

13

Tidal volume/Vital capacity definition

  • VT = difference in lung volume between normal inspiration and normal expiration
    • volume of air that enters and exits during one breathing cycle
    • VT ≈ 500ml
  • VC = volume of air exhaled after maximal inpiration followed by maximal expiration
    • VC = TLC - RV

14

Minute ventilation/volume definition

  • total volume of air breathed per minute
  • MV = tidal volume x frequency of breathing

15

Measurements of lung volumes

  • VT and Vc ==> spirometer
  • FRC ==> body plethysmograph: breath through moutpience in airtight chambger
  • forced expirogram = dynamic measurement ==> separates normal from obstructive/restrictive disease
    • spirometer measuring volume when subject inspires maximally and expires maximally
    • FEV1.0 = volume expired in first second
    • FVC = VC = total volume expired
    • FEV1.0/FVC = 80% when normal

16

Restrictive disease results on pulmonary function tests

  • e.g. pulmonary fibrosis ==> decreased compliance/difficult inspiration
  • ==> decrease in vital capacity
  • may not show significantly reduced FEV1.0/FVC

17

Obstructive disease results on pulmonary function tests

  • e.g. chronic brochitis or asthma ==> increased airway resistance
  • FEV1.0/FVC decreases significantly
  • increase in FRC (functional residual capacity) and RV (residual volume)
  • VC may be normal, slightly decreased or increased