Lecture #22: Pulmonary Ventilation Flashcards
Which muscles are used in passive and forced expiration?
- expiration is passive at rest
- forceful expiration:
> abdominal muscles
> internal intercostals
What is the difference between volume and capacity?
- Capacity is a combination of 2 or more volumes.
Total lung capacity = maximum volume of gas the lungs can hold
Total lung capacity is made up of distinct, non-overlapping sub-compartments referred to as lung volumes.
Combinations of lung volumes form lung capacities.
What is the volume and definition of tidal volume?
> 500 ml
> Volume of air that is inspired or expired with each breath at rest.
What is the volume and definition of inspiratory reserve volume?
> 3000 ml
> volume of air that can be inspired in addition to tidal volume with forceful inspiration.
What is the volume and definition of expiratory reserve volume?
> 1100 ml
> Additional volume of air that can be expired at end of tidal volume by forceful expiration.
What is the volume and definition of residual volume?
> 1200 ml
> volume of air remaining in lungs after forceful expiration.
What is the average capacity and definition of vital capacity?
> 4600 ml
sum of all the volumes that can be inspired or exhaled.
Inspiration to the maximum extent + expiration to the maximum extent.
What is the average capacity and definition of total lung capacity?
> 5800 ml
> Sum of all the volumes = vital capacity + residual volume
What is the average capacity and definition of inspiratory capacity?
> 3500 ml
> Sum of volumes above resting capacity = tidal volume + inspiratory reserve volume
What is the average capacity and definition of function residual capacity?
> 2300 ml
> Sum of volumes below resting capacity = expiratory reserve volume + residual volume
What is the definition of minute ventilation and how do you calculate it? Also, what is the average minute ventilation?
Total volume of gases moved into or out of the lungs per minute = minute ventilation (VE)
Minute Ventilation = (breaths per minute) x (tidal volume)
8000 ml/min or 8 L/min
What is the definition of alveolar ventilation and how is it calculated? Also, what is the average alveolar ventilation?
Total volume of gases that enter spaces participating in gas exchange per minute = alveolar ventilation (VA)
Alveolar Ventilation = (breaths/min) x (tidal volume - dead space)
5600 ml/min or 5.6 L/min
What organs make up the anatomic dead space?
> trachea
bronchi
bronchioles
What makes up physiological dead space?
anatomic dead space + ventilated alveoli with poor or absent perfusion
What is the total dead space in a normal individual?
0.15 liters
What are the two formulas for minute and alveolar ventilation?
Minute Ventilation = 0.5 x breathing rate
Alveolar Ventilation = 0.35 x breathing rate
What are the two observations that have to be taken into account when calculating dead space?
> dead space does not participate in ventilation and contains negligible CO2
> amount of CO2 in regions of lungs involved in gas exchange = that of arterial blood (PaCO2)
What is the definition of trans-pulmonary pressure and how do you calculate it?
Transpulmonary pressure -> difference between the alveolar pressure and the pleural pressure during any point in the inspiration of expiration cycles.
- measured in centimeters of water
What is the pleural pressure?
Pressure of fluid in the space between the visceral and parietal pleura.
- measured in centimeters of water
- during inspiration = -5 to -7.5 cm H20
- during expiration = -7.5 to -5 cm H20
What is alveolar pressure?
Pressure of air inside the alveoli.
- measured in centimeters of water
- during inspiration = 0 to -1 cm H20
- during expiration = 0 to +1 cm H20
Know the definition of compliance as it applies to the lungs and compare it with elastance?
Compliance is a measure of the ease with which a hollow viscus may be distended; i.e., the volume change resulting from the application of a unit pressure differential between the inside and outside of the viscus; the reciprocal of elastance.
Elastance is a measure of the tendency of a hollow viscus to recoil toward its original dimensions upon removal of a distending or collapsing force.
Compliance -> the extent (volume) to which lungs will expand for each unit increase in the transpulmonary pressure.
Compliance is expressed in liters (volume of air) per centimeter of water (pressure)
- normal = 200 ml air/ cm H20
Compliance is a measure of the expansibility of the lungs and trachea.
Compliance (capacitance) = increase in volume/increase in pressure
What is surface tension?
When water forms a surface with air, the water molecules on the surface of the water have an especially strong attraction for one another. As a result, the water surface is always attempting to contract. In lungs, this would cause the alveoli to try to collapse.
What are the most important components of surfactant?
> dipalmitylphophatidylcholine (a phospholipid)
surfactant apoproteins
calcium ions
What type of cells produce surfactant?
Type II alveolar cells
True or False:
If there is not surfactant, the pressure would calculate to about 18 cm of water pressure; about 4.5 times as great.
True
True or False:
If air passages leading from the alveoli are blocked, the surface tension in the alveoli collapses the alveoli. This creates negative pressure in the alveoli.
False - this creates positive pressure in the alveoli.
Which muscles are used in inspiration?
- respiratory diaphragm
- external intercostal muscles (limited)
- sternomastoids
- serratus anterior muscles
- scalene muscles
