oxygen transport Flashcards
what are the effects of the following factors on the O2 disassociation curve: increased PCO2 decreased pH fetal Hg increased 2,3 DPG increased temperature
increased PO2, decreases pH, 2,3-DBG and increased temp all shift curve to right
fetal hg has a L shifted curve
what does fetal Hg have a left shifted curve
because it doesn’t have beta subunits
where does 2,3 DPG bind on hemoglobin?
the beta subunit
the bohr effect is referring to the effects of what to stimuli?
increased PCO2 and decreased pH
what does a curve shifted to the Right mean?
higher oxygen disassociation
can we measure the rate of O2 usage by the tissues?
not directly
what are the two ways oxygen can go after being delivered to the tissues?
it can be used by the tissues or it can be taken up by the venous blood
what is the equation of the rate of delivery of O2 to the tissues?
oxygen content in the blood x cardiac output
what characterizes stagnant hypoxia?
- normal arterial partial pressure and concentration of O2
- decreased venous oxygen partial pressure and concentration
- cardiac output is decreased
- Extraction is increased
what characterizes hypoxic hypoxia?
decreased partial pressure and concentration of O2 in both the arteries and veins while the extraction stays normal
what is the main cause of stagnant hypoxia
CHF
what are some causes of hypoxic hypoxia?
high altitude
diffusion problems
hypoventilation
what characterizes histotic hypoxia? when can this occur?
- Normal partial pressure and concentration in arteries of O2
- Increased partial pressure and concentration of O2 in the veins
- Because extraction is reduced
- This can occur when there is poisoning of tissue metabolism by heavy metals, cyanide or other toxins
what characterizes anemic hypoxia?
- Normal partial pressure of O2 but decreased O2 concentration
- Decreased venous partial pressure and concentration
- Normal extraction
what characterizes CO poisoning?
- Results from substitution of CO for oxygen bound to Hg
- CO takes up the O2 binding sites
- Minor effect: left shift of the oxygen dissociation curve
describe the correlation of smoking with CO
Cigarette smoke contains up to 4% CO which can result in 5-10% reduction in O2 transport capacity
Where is the pneumotaxic center/ pontine respiratory group located?
In the pons….the nucleus parabrachialis medialis and the Kolliker fuse nucleus
Where is the DRG located?
Bilaterally in the nucleus of the tracts solitaries
What does the DTS consist of mostly?
Inspiratory neurons
Where is the VRG located?
Bilaterally in the retro facial nucleus, the nucleus ambiguous, and the nucleus retroambifualis
What type of neurons does the VRG primarily consist of?
Inspiratory and expiratory neurons
What is the Botzlinger complex?
A cluster of expiratory neurons in the VRG that generate pacemaker activity associated with the respiratory rhythm
What is the function of the pontine respiratory group?
Fine tune the resp pattern
No respiration is a characteristic of what level transaction?
Level IV
Irregular, gasping breathing is a characteristic of what level transaction?
Level III
Slower frequency and larger tidal volumes with lower infrequency breathing is characteristic of what level transaction?
Level II
Normal breathing is characteristic of transaction at what level?
Level I
When does apneusis occur?
Is occurs when there is a transaction at level II and the vagus is cut. It is characterized by longer inspiration phases ans short passive expirations.
What happens when there is both a transaction at level I and the vagus is cut?
Increased tidal volume with decreased frequency, but rhythmic breathing
Describe Cheyenne-stokes respiration
Abnormal form of breathing pattern characterized by altering periods of hypernea and apnea. You see this in injuries to the brain.
Describe cluster breathing (biot’s respiration)
Abnormal form of breathing associated with stroke, head trauma, pressure or a lesion in the lower pontine region of the brainstorm.
Take a few breaths and then stop, repeating this cycle.
Describe ataxic breathing
Characterized by completely irregular series of inspirations and expirations with irregular pauses and increasing periods of apnea
Why do the capillary partial gas pressures equilibrate with the alveolar, and not the other way around?
- The alveolar compartment has much more volume than the capillaries
What happens to DLCO in severely anemic patients?
- ventilation rate is increased, and cardiac output is increased since there is not enough O2 in the blood —>DLO2 is actually increased
- however there is a decrease of hemoglobin (due to the anemia) so it appears that DLCO is decreased
Is dissolved oxygen alone enough to meet the metabolic demands of the body?
N0o0o this is why hemoglobin exists
Define extraction?
Difference between the percent of O2 in arterial blood minus the percent in venous blood
What is P50=?
26 mmHg
This means at 50% saturation of hemoglobin
At PaO2=100 mmHg, what percent of hemoglobin is saturated? What percent of the total blood volume is this?
98.5% bound to hemoglobin
20% of total volume
At Pao2=40 mmHg,what percent of hemoglobin is saturated? What percent of the total blood volume is this?
75% saturated hemoglobin
What is the normal extraction percentage from arterial to venous blood of O2?
4-5%
Why is the extraction of O2 such a small number?
It occurs at the plateau of the sigmoid dissociation curve – cooperative binding
How many molecules of O2 does one hemoglobin bind?
4 molecules of O2
How is the dissociation curve shifted for venous blood?
To the right since pH is lower
What is the function of the plateau in the oxygen dissociation curve?
It permits toleration for hypoxemia
-ensures constant O2 content despite wide variations in PO2
How is the oxygen dissociation curve shifted in polycythemia?
Up
-hematocrit and therefore the percent of O2 of the volume of the blood is increased to 30%
How is the oxygen dissociation curve shifted in anemia?
Down
-hematocrit is decreased
How does P50 change in polycythemia or anemia?
It does not change
How does hypoxia influence the amount of hemoglobin?
It upregulates EPO mRNA and protein synthesis
-increases the amount of erythrocytes and therefore hemoglobin
