Physiology Flashcards
What is functional residual capacity and what is the normal value (in Litres)?
Functional residual capacity (FRC), is the volume remaining in the lungs after a normal, passive exhalation.
Normal value = 3L
Usually around 40% of total lung capacity.
What is tidal volume (TV)?
Volume of air entering or leaving lungs
during a single breath
Normal value = 0.5L
What is inspiratory reserve volume?
Extra volume of air that can be maximally inspired over and above the typical resting tidal volume
Normal value = 3L
What is expiratory reserve volume?
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
Normal value = 1L
What is the residual volume?
Minimum volume of air remaining in
the lungs even after a maximal
expiration
Normal value = 1.2L
What is inspiratory Capacity?
Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)
Normal value = 3.5L
What is functional residual capacity?
Volume of air in lungs at end of normal passive expiration
(FRC = ERV + RV)
Normal value = 2.2L
What is vital capacity?
Maximum volume of air that can be moved out during a single breath following a maximal inspiration
(VC = IRV + TV + ERV
Normal value = 4.5L
What is total lung capacity?
Total volume of air the lungs can hold
(TLC = VC + RV)
Residual volume can be measured by spirometry. true/false?
False
As a result of this it is also not possible to measure functional residual capacity or total lung capacity by spirometry
When does residual volume increase?
Residual volume increases when the elastic recoil of the
lungs is lost e.g. in emphysema
What is the FEV1/FVC ratio?
FEV1/FVC ratio is a calculated ratio used in the diagnosis of obstructive and restrictive lung disease.
It represents the percentage of a patient’s vital capacity that they are able to expire in the first second of forced expiration.
Values for normal FEV1/FVC?
Normal FEV1
Normal FVC
Normal FEV1/FVC%
Values for FEV1/FVC in airway obstruction?
Low FEV1
Low or normal FVC
Low FEV1/FVC%
Values for FEV1/FVC in lung restriction?
Low FEV1
Low FVC
Normal FEV1/FVC%
Values for FEV1/FVC in combination of restriction and obstruction in lungs?
Low FEV1
Low FVC
Low FEV1/FVC%
What is the normal range for FVC and FEV1?
Value equal to or greater than 80% of predicted
What is the normal range for FEV1/FVC ratio?
Value equal to or greater than 70% of predicted
Abnormal values for FVC and FEV1?
Mild: 70-79%
Moderate: 60-69%
Severe: less than 60%
Abnormal values for FEV1/FVC ratio?
Mild: 60-69%
Moderate: 50-59%
Severe: less than 50%
What 4 factors influence the rate of gas transfer across the alveolar membrane?
Partial pressure gradient of O2 and CO2 - Rate of transfer increases as partial pressure increases.
Diffusion coefficient (solubility of gas in membranes) - Rate of transfer increases as diffusion coefficient increases.
Surface area of alveolar membrane - Rate of transfer increases as surface area increases
Thickness of alveolar membrane - Rate of transfer decreases as thickness increases
What is lung compliance?
Compliance is measure of effort that has to go
into stretching or distending the lungs.
Lung compliance is: change in lung volume per
unit change in transmural pressure gradient
across the lung wall.
What does a low vs high lung compliance mean?
Low compliance indicates a stiff lung (one with high elastic recoil) and can be thought of as a thick balloon – this is the case often seen in fibrosis.
High compliance indicates a pliable lung (one with low elastic recoil) and can be thought of as a grocery bag – this is the case often seen in emphysema.
A lower lung compliance means that there is a lower change in pressure. True/false?
False
Means greater change in pressure is needed to produce a given
change in volume (i.e. lungs are stiffer). This causes shortness of breath especially on exertion
What happens to intrapleural pressure during inspiration and expiration?
During inspiration the airways are pulled open by the expanding thorax intrapleural pressure falls during inspiration.
During expiration the chest recoils intrapleural pressure rises during expiration
What is dynamic airway compression?
Dynamic compression of the airways results when intrapleural pressure equals or exceeds alveolar pressure, which causes dynamic collapsing of the lung airways.
Dynamic airway compression causes no problems in normal people.
Why is dynamic airway compression problematic in obstructive lung diseases?
Dynamic airway compression makes active expiration to be more difficult in patients with airway obstruction.
The rising intrapleural pressure during active expiration compresses the alveoli and airway
Why is it important not to give excessive oxygen to
COPD patients with chronic CO2 retention?
Excessive oxygen can lead to hypercapnic (high CO2) respiratory failure in COPD patients with chronic CO2 retention.
What are the reasons why giving excess oxygen is contraindicated in chronic CO2 retention?
Excessive oxygen given to patients with COPD may:
- Increase V/Q mismatch by diverting blood flow to poorly
ventilated alveoli - increase the release of CO2 from oxygenated haemoglobin (the Halden effect). But, COPD patients are unable to increase their ventilation to match increase in CO2 release.
Due to potential hypercapnic respiratory failure in patients with chronic CO2 retention, what is the desired range for oxygen saturations?
Target is to maintain a lower SaO2 (88-92%) in
these patient
What is pneumothorax?
Air in the pleural space.
What are some symptoms of pneumothorax?
Symptoms of pneumothorax include:
Shortness of breath and chest pain
What are the physical signs of pneumothorax?
Physical signs include hyper resonant percussion note and decreased/absent breath sounds.
What can impair oxygen delivery to the body tissues?
Respiratory disease
Heart failure
Anaemia
