Mechanism of ventilation pt.2 Flashcards
What determines VC
Strength of respiratory muscles
Elastic resistance of lungs
What affects VC
Gender, age, body build and posture
What is the ratio of FEV1/FVC of normally pulmonary function
0.8/ 80%
What is the main problem with acute obstructive disease, give an example
Increased airway resistance
Bronchial asthma
What is the main problem with chronic obstructive disease, give an example
decreased elasticity
Emphysema
What is the main problem with obstructive lung diease
Difficulty exhalation
What is the main problem with restrictive lung disease, give an example
Difficulty inhalation
pulmonary fibrosis
Which one has much reduced FVC, why
Restrictive lung disease
Lungs don’t stretch as much -> less air is inhaled -> lower FVC
which one has much reduced FEV1, why
Obstructive lung disease
Poor elastic recoil -> difficult to exhale quickly
which has lower and which has higher FEV1/FVC
Lower: Obstructive lung disease
higher: Restrictive lung disease
Spirometry Findings in obstructive vs Restrictive
RV
FRC
TLC
VC
FVC
FEV1
FEV1/FVC
Obstructive
RV: higher
FRC: higher
TLC: higher
VC: lower
FVC: lower
FEV1: much lower
FEV1/FVC: much lower (hallmark)
Restrictive:
RV: lower
FRC: lower
TLC: lower (hallmark)
VC: lower
FVC: lower
FEV1: much lower
FEV1/FVC: much lower (hallmark)
What is pulmonary ventilation
The volume of air that flows into and out of the respiratory track/ minute
How to calculate it
Tidal volume x breaths per minute
what is dead space
Part of the respiratory system where no gas echange takes place
what is the function of dead space
Warms, Humidifies and purifies air
what is the value of dead space
150 cm³ (⅓ TV)
What causes alveolar dead space
Non functioning/ dead alveoli
Non perfused alveoli (embolism or thrombus in pulmonary capillary)
In normal lungs ??=??
Physiological d.s = Anatomical d.s
in diseased lung ??>??
Physiological d.s (e.g. damaged alveoli) > anatomical d.s
what are the factors affecting anatomical dead space
Physiological: Large body size/ weight/ upright position/ neck extension
Bronchodilatation: By β-adrenergic/ anticholinergic drugs
Breathing through artificial airways: increases anatomical d.s -> less volume reaching the lungs
What is the significance of dead space
Difference in composition between alveolar and expired air
Difference between pulmonary ventilation and alveolar ventilation
How to calculate anatomical dead space
body weight in lbs
kg= 2.2 lbs
What is the significance of dead space
Difference in composition between alveolar air and expired air
Difference between pulmonary ventilation and alveolar ventilation
How to calculate dead space ventilation (VD)
dead space volume x respiratory rate
How to calculate alveolar ventilation
Pulmonary ventilation (VE) - dead space ventilation (VD)
OR
(TV-DS) x respiratory rate
Which is more beneficial, doubling tidal volume or respiratory rate
Doubling tidal volume
Which is more beneficial, shallow rapid or slow deep breathing
Slow deep breathing
What does hyper/ hypo ventilation apply to
Alveolar ventilation
How does hypoventilation affect alveolar PCO₂ and why
Increases it as less air is expired out
How does hyperventilation affect alveolar PCO₂ and why
Decreases it as more air is expired out
how to calculate VA using VCO₂ and PACO₂
VA = (VCO₂ / PACO₂) x constant (0.863 if mmgH or 115.1 if pKa)
