Ch 2 Ventilation Flashcards
What is the process by which oxygen is brought to the blood-gas barrier?
Ventilation
Ventilation is essential for the exchange of gases in the lungs.
What is tidal volume?
500 ml
Tidal volume is the amount of air that is inhaled or exhaled during normal breathing.
What is total ventilation?
7,500 ml/min
Total ventilation is the volume of air that leaves the lungs each minute.
What is anatomic dead space?
150 ml
Anatomic dead space refers to the volume of the conducting airways where no gas exchange occurs.
What is alveolar ventilation?
5,250 ml/min
Alveolar ventilation is the amount of fresh gas getting to the alveoli, available for gas exchange.
What is the formula for total ventilation (VT) in relation to dead space (VD) and alveolar volume (VA)?
VT = VD + VA
This equation shows the relationship between tidal volume, dead space, and alveolar volume.
What is functional residual capacity (FRC)?
Volume of gas remaining in the lungs after normal expiration
FRC cannot be measured with a simple spirometer.
Which method can be used to measure FRC using helium?
Helium dilution technique
This technique uses a known concentration of helium to determine lung volumes.
What is the significance of Boyle’s law in measuring lung volumes?
PV = K at constant temperature
Boyle’s law relates pressure and volume, allowing for calculations of lung volumes in a plethysmograph.
What is the relationship between alveolar ventilation and arterial Pco2?
If alveolar ventilation is halved, arterial Pco2 will double
This relationship highlights the importance of ventilation in regulating blood gas levels.
What is the normal ratio of dead space to tidal volume during resting breathing?
0.2 to 0.35
This ratio indicates the efficiency of gas exchange during normal respiration.
What are the two methods to measure anatomic dead space?
- Fowler’s method
- Bohr’s method
Fowler’s method uses nitrogen concentration, while Bohr’s method uses CO2 concentration.
Fill in the blank: The volume of gas in the lung after a maximal expiration is called _______.
Residual volume
Residual volume cannot be measured with a simple spirometer.
What is the primary reason that alveolar ventilation can be difficult to determine?
Measuring anatomic dead space accurately is challenging
The dead space volume affects the calculation of fresh gas available for exchange.
True or False: Alveolar gas expands by the full size of tidal volume with each breath.
True
This is because the gas from the anatomic dead space is included in each breath.
What is the Bohr equation?
VD = PACO2 - PECO2
Where VD is dead space, PACO2 is the partial pressure of CO2 in alveolar gas, and PECO2 is the partial pressure of CO2 in mixed expired gas.
What is the normal ratio of dead space to tidal volume during resting breathing?
0.2 to 0.35
What does Fowler’s method measure?
The volume of the conducting airways down to the level where rapid dilution of inspired gas occurs with gas already in the lung.
What is the anatomic dead space?
The volume of the conducting airways, about 150 ml.
What is the physiologic dead space?
The volume of the lung that does not eliminate CO2.
In normal subjects, how do the volumes of anatomic and physiologic dead space compare?
They are very nearly the same.
What is total ventilation?
Tidal volume × respiratory frequency.
How is alveolar ventilation calculated?
(VT − VD) × n
Where VT is tidal volume, VD is dead space, and n is respiratory rate.
Which regions of the lung ventilate better?
The lower regions ventilate better than the upper zones.
What method can demonstrate regional differences in ventilation?
Inhaling radioactive xenon gas.
What happens to ventilation when a subject is in the supine position?
The difference in ventilation between apical and basal regions disappears.
What lung volumes cannot be measured with a simple spirometer?
- Total lung capacity
- Functional residual capacity
- Residual volume
What is the relationship between CO2 concentration in alveolar gas and arterial blood and alveolar ventilation?
They are inversely related.
True or False: The physiologic dead space is measured by Fowler’s method.
False
What is the expected change in arterial Pco2 if CO2 production remains constant and alveolar ventilation is increased threefold?
It will decrease to 25% of its former value.
What happens to the airway pressure during an expiratory effort against a closed glottis in a body plethysmograph?
Airway pressure increases.
What is the expected change in dead space fraction if tidal volume is decreased and respiratory rate is increased?
Increase in the dead space fraction.
What is the tidal volume of the ventilator set for the patient in the emergency department?
300 ml
What factor can account for the change in total ventilation for the 20-year-old college student?
Her ability to protect her airway and potential aspiration.
What does the physiologic dead space increase in patients with lung disease indicate?
Inequality of blood flow and ventilation within the lung.
What is the volume of the FRC in liters if the original and final helium concentrations were 10% and 6%, and the spirometer volume was kept at 5 liters?
3.0
How does the ventilation of the acini at the base of the upright human lung compare to that at the apex?
It is greater at the base.
What happens to the volume of gas delivered to the alveoli with each breath during mechanical ventilation if tidal volume is decreased and respiratory rate is increased?
It may increase.
