Ventilation Flashcards
What is pulmonary ventilation?
The cyclic process of inspiration and expiration.
What happens when the sternocleodomastoid contracts?
They elevate the sternum and clavicle (front)
What happens when the trapezius contracts?
They stabilize and move the scapula (back)
What happens when the scalenes (anterior, middle, posterior) contract?
They elevate the upper ribs
How many time do the airways branch?
23 generations
How many branching points are included in the conducting zone
16 generations
What is an acinus?
Smallest functional unit of the lungs.
It consists of a cluster of alveolar ducts, alveolar sacs and alveoli supplied b a bronchiole.
Typically, tidal volume is about … at rest, but can increase up to … with exercise.
Typically, tidal volume is about 500mL at rest, but can increase up to 3 L or more with exercise.
What is minute ventilation? What is the formula for minute ventilation?
Total amount of air inhaled or exhaled from the lungs in one minute.
VE = f x Vt
What is alveolar ventilation? What is the formula?
The volume of fresh air reaching the respiratory zone (alveoli) per minute.
VA = f x (Vt-Vds)
What is dead space ventilation? What is the formula?
Volume of fresh gas reaching the anatomic dead space per minute (i.e. that does not participate in gas exchange because it occupies areas of the respiratory system where no alveoli are present or where alveoli are not functioning properly).
What is the anatomic dead space?
Volume of inspired gas (~150 mL) that never makes it past the conducting zone and never participates in gas exchange.
What must be the relationship of tidal volume (Vt) relative anatomic dead space volume (Vd) for gas exchange to occur?
Tidal volume must be greater than the volume of the anatomic dead space.
Under what circumstances can the anatomic dead space appear increased?
When increases in minute ventilation are not matched by increases in alveolar ventilation (i.e. minute ventilation increases but alveolar ventilation stays the same).
Under what circumstances can someone have a relatively high minute ventilation, yet a normal or even increased PaCO2?
In certain diseases that dissociate minute ventilation from alveolar ventilation.
In other words, it is possible to hypoventilate DESPITE having a high minute ventilation!
What is physiological dead space?
Total dead space, i.e. volume of inspired gas that does not exchange CO2. It is the sum of anatomic dead space and alveolar dead space
What is alveolar dead space?
When air reaches the alveoli but does not participate in gas exchange (when alveoli become dysfunctional and no longer participate in gas exchange, they contribute to alveolar dead space).
Minute ventilation is the sum of …
dead space ventilation and alveolar ventilation (all expressed in L/minute)
What is a partial pressure?
The pressure that a specific gas in a mixture would exert if that gas alone would occupy the entire volume of the mixture.
The relative amounts of each gas in a mixture are reflected by their…
partial pressures
Partial pressures are exerted in proportion to…
the number of molecules present in the mixture.
What is the sea level atmospheric pressure?
760 mmHg
At body temperature (37°C), what is the water vapour pressure?
47 torr (47 mmHg)
