Physiology Flashcards
What is tidal volume
The volume of air inhaled and exhaled in normal breathing
What is normal tidal volume
500ml in both men and women
What is inspiratory reserve volume
the extra volume of air that can be inspired after a forceful inspiration
What is expiratory reserve volume
the extra volume of air that can be expired after forceful expiration
What is residual volume
The amount of air remaining in lungs after maximal expiration
What is functional residual capacity
The volume of air remaining in lungs after a normal exhalation
Difference between residual volume and functional residual volume
Residual volume = the remaining air after maximal expiration
Functional reserve volume = the remaining air after normal expiration
Formula of functional residual volume
ERV + RV
What is vital capacity
The maximum volume of air that can be expired after maximum inspiration
Formula for vital capacity
IRV + ERV + tidal volume
Formula for total lung capacity
IRV + tidal volume + ERV + RV
IRV + tidal volume + functional residual capacity
What is physiological dead space
anatomical dead space + alveolar dead space
What is anatomical dead space
Air filling in the respiratory tract but not used in gas exchange (eg. in bronchioles)
What is alveolar dead space
volume of air that is ventilated but not perfused in alveoli (not all alveoli are perfused)
What conditions increases alveolar dead space
Emphysema
What does ERV + RV represent
functional residual capacity
What does IRV + ERV + tidal volume represent
vital capacity
What is the formula for physiological dead space
(PaCO2−PeCO2)/PaCO2
What does spirometry measure
the maximum volume of air forcefully expired after maximum inspiration
What does “maximum volume of air expired after maximum inspiration” represent
forced vital capacity
What is FEV1
FVC expelled after 1 second
What does FEV1/FVC represent
Proportion of FVC expelled in 1 second of forceful expiration
How do obstructive diseases affect spirometry
Reduction in FEV1
Reduction in FEV1 greater than reduction in FVC
FEV1 / FVC < 70%
How do restrictive diseases affect spirometry
Reduction in FVC and FEV1
Normal FEV1 / FVC ratio
What are the values of FEV1 and FVC for restrictive lung disease like
FEV1 and FVC < 70% expected
FEV1/FVC > 80% expected = normal
Causes of restrictive pattern
Pulmonary fibrosis Pleural effusion Pulmonary oedema Obesity Neuromuscular disorder Empyema
Why do restrictive diseases cause such pattern
Due to reduction in total lung capacity - unable to hold that much air
