West Pulmonary Book (end of chapter summary notes) Flashcards
Tidbits from the summaries and key points for the first few chapters
What two zones are the airways divided into?
- conducting zone
- respiratory zone
The volume of the anatomic dead space is about how much?
150 mL
The volume of the alveolar region is about how many liters?
2.5 - 3 L
Gas movement in the alveolar region is done chiefly by ______.
diffusion
The approximate surface area of the alveoli is about how much?
50 - 100 meters squared
In the alveolar ducts, the predominant mode of gas flow is _______ rather than _______.
- diffusion
- convection
When you take a maximal inspiration followed by a maximal expiration, the exhaled volume is called what?
vital capacity
The gas that remains in the lungs after maximal expiration is known as what?
residual volume
The volume of gas in the lung after a normal expiration is known as what?
functional residual capacity
The amount inspired and expired during normal ventilation is called what?
tidal volume
How do you calculate total ventilation?
tidal volume x respiratory frequency
With normal ventilation, which areas ventilate better, the upper or lower areas?
the lower areas ventilate better than the upper areas
(regardless of what position the patient is in (supine, lateral, etc) the dependent part of the lung will have better ventilation, d/t the effects of gravity)
Which lung volumes cannot be measured with a simple spirometer?
- total lung capacity
- functional residual capacity
- residual volume
Is the concentration of CO2 (and therefore its partial pressure) in alveolar gas and arterial blood directly or inversely related to the alveolar ventilation?
inversely related
Fick’s Law of diffusion states that the diffusion rate of a gas is directly proportional to what (3 things), and inversely proportional to what (1 thing)?
directly proportional:
- partial pressure gradient
- membrane area
- solubility of the gas
inversely proportional:
1. membrane thickness
The rate of transfer of a gas is proportional to a diffusion constant, which depends on the properties of the tissue and the particular gas. What is directly and inversely proportional to this constant?
- directly proportional to the solubility of the gas
- inversely proportional to the square root of the molecular weight
The diffusion process can be challenged by what 3 things?
- exercise (d/t increased blood transit time through the pulm capillaries and less time for exchange)
- alveolar hypoxia (not enough O2 hopping on the RBCs)
- thickening membrane (can’t get through)
In normal lungs, when pulmonary vascular pressures are increased (ie with exercise), the pulmonary vascular resistance is decreased by what two mechanisms?
- recruitment (opening of previously closed vessels)
- distention (increased in caliber of the vessels)
Define hypoxic pulmonary vasoconstriction.
the contraction of smooth muscle in the walls of the small pulmonary arterioles in hypoxic regions of the lungs
At what point in one’s life is the release of hypoxic pulmonary vasoconstriction critical?
at birth in the transition from placental to air breathing
for knowledge!
What is the approx. ratio of the pressures in the pulmonary circulation to that of the systemic circulation?
1:10
pulm ~ 10 mmHg, systemic ~ 100 mmHg
If capillary pressure is less than alveolar pressure at the top of the lung, what happens to the capillaries?
they collapse
Fluid movement across the capillary endothelium is governed by what concept?
the Starling equilibrium
basically has to do with the differences in hydrostatic and osmotic pressures in the vasculature and the interstitium
In zone 2 of the lung, blood flow is determined by _______ _______ minus _______ _______.
arterial pressure minus alveolar pressure
Define hypoxemia.
abnormally low PO2 in arterial blood
What is the partial pressure of O2 in the atmosphere? What is the partial pressure of O2 in the alveoli?
atmosphere - 150 mmHg
alveoli - 100 mmHg
(the lower value in the alveoli is due to the removal of O2 by pulmonary capillary blood and its continual replenishment by alveolar ventilation)
What are the 4 causes of hypoxemia?
- hypoventilation
- diffusion limitation
- shunt
- ventilation-perfusion inequality
Fun facts about hypoventilation. (3)
- always increases the alveolar and arterial PCO2
- decreases the PO2 unless additional O2 is inspired
- hypoxemia is easy to reverse by adding O2 to the inspired gas
Fun facts about shunts. (3)
- hypoxemia responds poorly to added inspired O2 **
- when 100% O2 is inspired, the arterial PO2 does not rise to the expected level (a useful diagnostic test) **
- if the shunt is caused by mixed venous blood, its size can be calculated from the shunt equation
What does the ventilation-perfusion ratio determine?
the gas exchange
What does a ventilation-perfusion inequality impair?
the uptake and elimination of all gases by the lung
The elimination of CO2 is impaired by V/Q inequality, but can this be corrected with increased ventilation?
yes. yes it can.
The uptake of O2 is impaired by V/Q inequality, but can this be corrected with increased ventilation?
no. no it can’t.
What are two causes of hypercapnia?
- hypoventilation
- V/Q inequality
The different behaviors of O2 and CO2 is attributable to what?
the differences between their dissociation curves
A shift to the right of the oxygen dissociation curve is cause by what 4 things?
- increase in H+
- increase in PCO2
- increase in temp
- increase in 2,3-DPG
CO2 is carried in the blood in three forms:
- as bicarbonate
- combined with proteins
- dissolved
What is the Haldane effect?
This describes how oxygen concentrations determine hemoglobin’s affinity for carbon dioxide.
(For example, high oxygen concentrations enhance the unloading of carbon dioxide. The converse is also true: low oxygen concentations promote loading of carbon dioxide onto hemoglobin. In both situations, it is oxygen that causes the change in carbon dioxide levels.)
What is the Bohr effect?
This describes how carbon dioxide and H+ affect the affinity of hemoglobin for oxygen.
(High CO2 and H+ concentrations cause decreases in affinity for oxygen, while low concentrations cause high affinity for oxygen.)
The maximum amount of oxygen that can be bound to hemoglobin is known as what?
O2 capacity
The amount of oxygen combined with hemoglobin divided by the capacity is known as what?
O2 saturation
