Small Group Questions Flashcards
How do the following change in Hypoxic Hypoxia?
- PaO2
- Arterial Hemoglobin Saturation
- O2 extraction
- Venous Hemoglobin Saturation
- PvO2
Cyanotic or Not?
Hypoxic hypoxia: reduction of oxygen entering the blood
Line A - lower PaO2
Line B - lower arterial hemoglobin saturation
Line C - same O2 extraction (no metabolism change)
Line D - lower venous hemoglobin saturation
Line E - lower PvO2
Possibly cyanotic (must be lower than 60% Hb sat.)
If equal volumes of blood are mixed, what would be the equilibrating oxygen partial pressure (mm Hg) if the PO2 of one sample is 100 mm Hg and the PO2 of the other sample is 50 mm Hg? What does this simple example teach you about venous admixture and shunt blood flow in the circulatory system?
60 mm Hg.
just a small amount of shunted blood can pull blood pressure down a significant amount because of the hemoglobin curve.
What are normal values (mm Hg) for PaO2 and PvO2? What would you predict would happen to these values during a voluntary breath hold? Would the oxygen extraction increase, decrease or remain the same? Would the subject become
cyanotic? Defend your reasoning.
Normal values:
PaO2: 100 mm Hg
PvO2: 40 mm Hg
When you hold your breath, PaO2 decreases and PvO2 gets lower..
O2 extraction is the same since it is defined by the a-v difference in oxygen pressures.
The subject would not become cyanotic since it is voluntary and you would pass out first.
Define arterial hypoxemia. What is the most common clinical cause for arterial hypoxemia?
Decreased partial pressure of oxygen in the arteries.
V/Q inequality is the most common cause.
What is Hypemic hypoxia?
How do the following change in Hypemic Hypoxia?
- PaO2
- Arterial Hemoglobin Saturation
- O2 extraction
- Venous Hemoglobin Saturation
- PvO2
Cyanotic?
(anemia with hematocrit of 22% Line A - same PaO2
Line B - same arterial hemoglobin saturation
Line C - much higher oxygen extraction (doubled)
Line D - much lower venous hemoglobin saturation
Line E - much lower PvO2
reduction in the capacity of the blood to carry oxygen
What is Stagnant hypoxia?
How do the following change in Stagnant Hypoxia?
- PaO2
- Arterial Hemoglobin Saturation
- O2 extraction
- Venous Hemoglobin Saturation
- PvO2
Cyanotic?
Stagnant Hypoxia - inadequate oxygen delivery due to poor blood circulation Line A - normal PaO2
Line B - normal arterial hemoglobin saturation
Line C - higher oxygen extraction
Line D - lower venous hemoglobin saturation
Line E - lower PvO2
probably cyanotic
What is Histotoxic hypoxia?
How do the following change in Histotoxic Hypoxia?
- PaO2
- Arterial Hemoglobin Saturation
- O2 extraction
- Venous Hemoglobin Saturation
- PvO2
Cyanotic?
Histotoxic Hypoxia - tissues can’t use oxygen line
A - normal PaO2
Line B - normal arterial hemoglobin saturation
Line C - lower O2 extraction
Line D - higher venous hemoglobin saturation
Line E - higher PvO2
probably not cyanotic
How do you calculate the cyanotic threshold?
Hb content - 6/ Hb content
Ex: Hb = 7g/dL
7-6/7 = 20% saturation
At what depth does ambient pressure exceed 90 mmHg, the pressure generated by the inspiratory muscles?
What does a snorkel above 0.5 m in length add?
At 1.2 m under water
Considerable deadspace –> alveolar ventilation will become inadequate
Dead space can be increased (and better envisioned) by breathing through a long tube, such as a snorkel. Even though one end of the snorkel is open to the air, when the wearer breathes in, they inhale a significant quantity of air that remained in the snorkel from the previous exhalation. Thus, a snorkel increases the person’s dead space by adding even more “airway” that doesn’t participate in gas exchange.
In physiology, dead space is the volume of air which is inhaled that does not take part in the gas exchange, either because it (1) remains in the conducting airways, or (2) reaches alveoli that are not perfused or poorly perfused
What is the most important stimulus for breathing?
The PaCO2
