Flashcards in Pulm Deck (11):
What volumes can be added to get total lung capacity (TLC)
TLC = VC + RV
TLC = IC + FRC
TLC = RV + ERV + TV + IRV
VC = vital capacity
RV = residual volume
FRC = functional residual capacity
IC = inspiratory capacity
ERV = expiratory reserve volume
TV = tidal volume
IRV = inspiratory reserve volume
What kind of pulmonary disease (restrictive or obstructive) is pulmonary fibrosis? What changes in lung volumes could we expect?
Pulmonary fibrosis is a restrictive lung disease.
How does the body compensate for hypoxia during acclimatization?
In full acclimatization to hypoxia, the body's hematocrit can increase from a normal sea-level value of approximately 45% to 60-65%, with a proportional increase in blood hemoglobin (Hb) levels. This increased level of Hb in the blood makes it possible to carry a normal amount of O2 (normal O2 content) even though the arterial PO2 and oxygen saturation are far lower than (sea-level) normal.
What is the equation for forced vital capacity?
FVC = TLC - RV
as calculated from a maximum expiratory flow-volume curve
How does a right or left shift of the oxygen dissociation curve affect oxygen loading or unloading of Hb?
A right shift of the curve facilitates unloading of O2
A left shift of the curve facilitates loading of O2
What factors would cause a right-shift of the O2 dissociation curve?
-decrease in pH
-increase in temperature
-increase in PCO2
-increase in 2,3-BPG
-exercising muscle is hot, acidic, and hypercarbic
What factors would lead to a left-shift of the O2 dissociation curve?
-increase in pH
-decrease in temperature
-decrease in PCO2
-decrease in 2,3-BPG
-CO poisoning (this would also cause the maximum saturation of Hb to decrease)
What is FRC?
The amount of air that remains in the lungs after a normal expiration.
Because this volume cannot (be definition) be expired in its entirety, it cannot be measured by spirometry.
*In general, any lung volume that contains the residual volume, which is the amount of air remaining in the lungs after a maximal expiration, cannot be measured using spirometry.
What methods can be used to measure lung volumes that include the RV (TLC and FRC)?
(1) Helium dilution techniques, coupled with spirometry
Describe the physiologic changes that occur in a person who is living at high altitude.
The decreased barometric pressure at high altitude leads to alveolar hypoxia and consequently arterial hypoxia. Pulmonary vasoconstriction occurs in response to alveolar hypoxia. (Therefore, the diameter of the pulmonary vessels will be greater in a person who is living at sea level relative to a person who is living at altitude.)
Arterial hypoxia --> inc. EPO production --> inc. hematocrit. This is the physiologic change that allows an acclimatized person to have a normal O2 content despite decreased O2 tension and decreased HB saturation with O2.
hypozemia --> inc. in muscle capillary density
Ventilation increases --> respiratory alkylosis --> renal compensation by increasing bicarbonate excretion