pk2 Pressure and Compliance Flashcards
List 5 variables that affect lung volume.
1 - Height 2 - Sex 3 - Age 4 - Race 5 - Respiratory Diseases
What is Boyle’s Law?
P1V1=P2V2
Why must respiratory muscles do work to increase the volume of the lungs?
1 - To stretch the elastic components of the respiratory system.
2 - To overcome the resistance to flow.
Which two surfaces surround the pleural space?
1 - Visceral pleura (deep).
2 - Parietal pleura (superficial).
What is contained within the pleural space?
Pleural fluid.
What is the function of pleural fluid?
To create a sub-atmospheric pressure in the pleural space.
How are the lungs coupled to the thoracic cage?
Via the intrapleural pressure (not mechanically).
What is compliance? What is the equation for compliance? What are its units?
A measure of distensibility of an elastic structure.
Compliance = ΔV / ΔP
L * kPa^-1
What is thoracic cage distending pressure?
Pressure across the thoracic cage:
= pressure inside - pressure outside.
What is lung distending pressure?
Pressure across the lung:
= pressure inside - pressure outside.
What is the total system compliance and how is it calculated?
The compliance of the ‘total’ respiratory system, including the lungs and the thoracic cage.
1/Total System Compliance = 1/Lung Compliance + 1/Thoracic Cage Compliance
What is FRC? What does it show?
Functional residual capacity.
The volume of the lungs where the total distending pressure of the system is 0 (the system is at equilibrium).
What is a pneumothorax?
A collapsed lung caused by air entering and filling the pleural space through perforations in the lung.
This results in a loss of distending pressure (to 0).
What is the equation for specific compliance?
Compliance / Functional residual capacity
What is a primary spontaneous pneumothorax caused by?
Spontaneous = Not by an injury.
Due to the formation of small sacs of air (blebs) in lung tissue that rupture, causing air to leak into the pleural space.
