Ventilation Flashcards
1
Q
Ventilation (general) definition
A
- amount of air-flow in the lungs
2
Q
Minute ventilation vs. Alveolar ventilation
A
- 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
Q
Factors that impact alveolar ventilation
A
- bronchodilators/constrictors
- exercise
- altitude
- obstructive/restrictive diseases
- gravity
4
Q
Excercise impact on alveolar ventilation
A
- moderate excerise ==> ~10x increase in ventilation
5
Q
Bronchodilators/contrictors impact on alveolar ventilation
A
- bronchodilators ==> increased ventilation
- bronchoconstrictors ==> decreased ventilation
6
Q
Obstructive/restrictive disease impact on alveolar ventilation
A
- 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
Q
Gravity impact on alveolar ventilation
A
- 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
Q
Factors that impact work of breathing
A
- work of breathing ≈ “work” done by respiratory muscles on lungs
- increased work of breathing occurs b/c:
- increase in elastic recoil (decreased compliance)
- increase in airway resistance
- combination of #1 & #2
9
Q
Changes in work of breathing at high/low tidal volumes
A
- @ 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
Q
Dead-space characteristics
A
- ~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
Q
Residual volume/functional residual capacity definition
A
- 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
Q
Total lung capacity definition
A
- TLC = volume of air inside lungs @ maximal inspiration
- TLC = ~7.5L
13
Q
Tidal volume/Vital capacity definition
A
- 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
Q
Minute ventilation/volume definition
A
- total volume of air breathed per minute
- MV = tidal volume x frequency of breathing
15
Q
Measurements of lung volumes
A
- 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
Q
Restrictive disease results on pulmonary function tests
A
- e.g. pulmonary fibrosis ==> decreased compliance/difficult inspiration
- ==> decrease in vital capacity
- may not show significantly reduced FEV1.0/FVC
17
Q
Obstructive disease results on pulmonary function tests
A
- 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
