Respiration 2 Flashcards
What is compliance?
The measure of elasticity so how easy it is to expand and relax your lungs
What is the equation for compliance?
Compliance= change in volume / change in pressure
What characterises high compliance in lungs?
Easier to expand lungs BUT more difficult to expire DUE TO LOSS OF ELASTIC RECOIL
What happens to lung compliance in pulmonary fibrosis?
Compliance DECREASES
Lungs become more rigid
More work required for inspiration
What happens to lung compliance in emphysema?
Compliance INCREASES
Loss of elastic recoil in lung tissue
Easier to inflate lungs but harder to expire
What are the 2 major components of elastic recoil in lungs?
Anatomical component- elastic and collagen fires in lung tissue
Surface tension generated at air-fluid interface
What is surface tension in lungs?
Alveoli have a fluid lining and air inside. This creates an air and fluid interface. Whenever water and air come in contact, the water molecules attract each other and form a sphere structure. THIS CREATES TENSION AND SO SURFACE TENSION IN LUNGS
What can increased surface tension do to alveoli?
Collapse them
What is surfactant and what is its role?
Acts to reduce surface tension
Produced by Type II pneumocytes
Composed of lipids and proteins
Prevents smaller alveoli from collapsing into larger ones
*Without intervention, this would cause smaller alveoli to collapse into larger ones
recall how a basic spirometer works and the different lung volumes that can be measured
A spirometer is a device that measures the volume of air breathed in and out. The basic working principle is:
The person breathes into a mouthpiece connected to a chamber
The chamber either moves up and down (in older water-sealed spirometers) or has sensors that detect airflow
This creates a trace that shows volume changes over time
it can measure:
Tidal Volume (TV)
Inspiratory Reserve Volume (IRV)
Expiratory Reserve Volume (ERV)
Vital Capacity (VC)
wat volume cannot be measured by a simple spirometers?
residual volume because it’s the air that remains in the lungs after maximum expiration.
What is anatomical dead space?
Volume of conducting airways
What is physiological dead space?
Volume of lungs not participating in gas exchange
Includes conducting zone + non-functional areas of respiratory zone
Normally almost identical to anatomical dead space
Is physiological dead space and anatomical dead space volumes meant to be similar?
Yes
At least for a healthy individual
when would the physiological dead space volume increase?
when there is a blockage restricting gas exchange
What is Tidal Volume (TV)?
Volume of air moved during normal breathing
What is Inspiratory Reserve Volume (IRV)?
Extra volume that can be forcefully inhaled after a normal tidal inspiration
What is Expiratory Reserve Volume (ERV)?
Extra volume that can be forcefully exhaled after a normal tidal expiration
What is Residual Volume (RV)?
Volume of air remaining in lungs after maximum expiration
What is Vital Capacity (VC)?
Maximum volume that can be exhaled after maximum inhalation
What is Total Lung Capacity (TLC)?
Maximum volume of air lungs can contain
What is Functional Residual Capacity (FRC)?
Sum of Expiratory Reserve Volume + Residual Volume
What is Inspiratory Capacity (IC)?
Sum of Tidal Volume + Inspiratory Reserve Volume
What determines airflow in the lungs according to Poiseuille’s law?
Airflow is:
Proportional to pressure gradient
Inversely proportional to resistance
*Resistance is inversely proportional to the fourth power of radius
Small changes in airway diameter have large impacts on flow rate
What was the take home message from Poiseuille’s law?
resistance = 1 /radius 4 (to the power of 4)
*Resistance is inversely proportional to the fourth power of radius
well what does that mean?
A small change in the radius has a big impact on the resistance and hence flow rate. AS RESISTANCE GOES UP, BREATHING BECOMES HARDER
What is the distribution of airway resistance in a normal individual (total 1.5cm H2O.s.litres-1)?
Pharynx-Larynx: 40%
Airways >2mm diameter: 40% (in larger airways, RESISTANCE IN SERIES)
Airways <2mm diameter: 20% (in smaller airways, RESISTANCE IN PARALLEL)
How does the parasympathetic nervous system affect bronchial smooth muscle?
Acetylcholine is released from the vagus
Acts on muscarinic receptors
Leads to airway CONSTRICTION
How does the sympathetic nervous system and epinephrine affect bronchial smooth muscle?
Sympathetic: Norepinephrine release (weak agonist) → DILATION
What is laplace’s law/ equation?
Pressure = 2 x surface tension
——————————
Radius
SO
The bigger the radius, the less pressure is needed to keep the alveoli opened
