November 3, 2023 Flashcards
what is Transit time:
0.3 sec (usually) or .75 seconds (amount of time that blood goes from 40-100mmHg)
the amount of time blood spends interfacing with the alveoli (where gas exchange occurs)
What amount of PaO2 fully saturates hemoglobin?
100mmHg
Cardiac output can increase from 5L/min; can go up to ________L/min during exercise;
25L/min
flow is much faster
During exercise, flow is faster so the transit time decreases, from .75 seconds to …….. for oxygen
to about 0.45 seconds
(still more than 0.3) so we still have excess time
is CO2 a more diffusible gas than O2?Why?
yes
goes through membranes more easily
how long does it take PaCO2 to go from 46mmHg to 40mmHg
Within 0.15 seconds, the PaCO2 goes from 46mmHg to 40mmHg (half the time as O2)
In a moderately limited diffusion situation, does it takes longer for the PaO2 to get from 40 to 100mmHg
yes
what are the two reasons why CO2 diffuses faster than oxygen
- Not as big change in PaCO2(46-40 mmHg) compared to PaO2(40-100mmHg)
- diffuses through membrane easier
what test is used to diagnose underlying pathology
Exercise stress test is used to diagnose underlying pathology
i.e. riding a bicycle for a couple minutes
is a stress test needed to determine underlying
conditions in a person with a severe diffusion limitation
no, because at rest there PO2 is already lower than 100mmHg
is a stress test needed to determine underlying
conditions in a person with a moderate diffusion limitation
yes, because at rest there PO2 might be normal (100mmHg) but exercise can reveal a lower PO2 (compared to normal)
what can happen as a result of diffusion limitations during exercise
hypoxemia (restrictive diseases)
Does knowing that a person is hypoxemic mean that they’re also hypercapnic?
No, but the other way around is probably true
what is a Restrictive Disease
Restrictive Disease: makes it harder to inflate the lung
what is an obstructive disease
easy to inflate lung, hard to deflate lung
what is Pulmonary Fibrosis (Restrictive Disease)
Pulmonary Fibrosis (Restrictive Disease)
Thickening of the alveolar membrane due to scar tissue (caused by infection, or inhalation of noxious chemicals)
Can Pulmonary Fibrosis (Restrictive Disease) lead to increased diffusion time
yes
Does pulmonary Fibrosis (Restrictive Disease) lead to increased or decreased lung compliance
Leads to decreased lung compliance (stiff lung, hard to open), which restricts airflow in, but no problem out
Lung Compliance:
the ability of the lung to expand in response to a difference in pressure
what is Pulmonary Edema
the accumulation of excess fluid in the lungs.
how does Pulmonary Edema occur
- Poor Left Ventricle function due to congestive heart failure or post-myocardial infarction (not injecting enough from the ventricle); forces fluid between alveoli and capillary which increases diffusion distance
- Increased left atrial pressure
3.increase in pulmonary venous pressure
- This forces fluid into the interstitial space (edema) from pulmonary capillaries causing an increased space between membranes and limits diffusion
5.More effort to inflate the lung (decreased lung compliance, laboured breathing:
dyspnea)
what is a possible treatment for both Pulmonary Edema and Pulmonary Fibrosis
a moderately progressive program of physical activity
–>
improves LV function and respiratory muscle strength
During exercise, there is an increase in free ADP and an increase in mitochondrial respiration this leads to……..
decrease in PvO2 and an increase in PvCO2 (production of Krebs and “extra” CO2)
We are using more O2 and giving up more CO2
PaO2 is always maintained at _______ even during exercise
100mmHg (does not curve downwards like in the
graph)
page 107
During exercise, despite the fact that PvO2 comes in at a lower pressure (20mmHg instead of 40mmHg), does it still reach 100mmHg in the same amount of time (0.3 seconds)
yes
during exercise, despite the fact that PvO2 comes in at a lower pressure (20mmHg instead of 40mmHg), it still reaches 100mmHg in the same amount of time (0.3 seconds)
check this by looking at PaO2 , it remains constant
page 107
During exercise, despite the fact that PvCO2 starts at 46mmHg and continues to increase do we become hypercapnic
no, look at PaCO2, it remains constant at 40mmHg even during maximal exercise, therefore we don’t become hypercapnic
why do highly trained elite endurance athletes sometimes produce hypoxemia (low O2) during exercise. why
A very high cardiac output
A higher than normal O2 extraction at the tissues
In-depth explanation: they have a transit time of about 0.25 seconds (which is lower than regular people of 0.45 seconds), because their flow is faster, because their cardiac output is faster. They also start at a lower PvO2 (about 10 mmHg), so their PvO2 has to increase a greater amount to get back up to 100mmHg compared to regular people.
That gap from 10mmHg to 100mmHg can be achieved, just not in 0.3 seconds
Summary:
-Start at a lower PvO2
-Have a shorter transit time
page 108
O2 Transport is dependent on?
Partial Pressure of Oxygen (PO2)
what are the two places O2 goes in the blood
1.Dissolved in plasma
2.Dissolved in plasma bound to Hb
how many mls/100mls of blood per every mmHg of partial pressure
0.003mls/100mls of blood per every mmHg of partial pressure
0.003mls/100mls of blood per every mmHg of partial pressure
what is Dissolved PaO2 at 100 mmHg
Dissolved:
➢ At PaO2 = 100 mmHg
➢ This means 0.3mls O2 /100mls of blood is dissolved
➢ “0.3 volumes %”
page 109
what is Dissolved PaO2 at 700 mmHg
since 0.3 volume % = 100mmHg
2.1 volume % = 700mmHg
how many mls of O2 can bind to Hemoglobin (Hb) when 100% fully saturated
1.34 mls of O2 when hemoglobin 100% fully saturated
Males have: _____g of Hb/100mls of blood
16
Females have: ______g of Hb/100 mls of blood
14
if you go up to high altitude, and the lower PO2 produces less Hb saturation (say 50%), how many mls of O2 can 1 gram of Hb hold
1.34 mls = 100%
0.67 mls = 50%
Calculate the total O2 carried by the blood at 100% Hb saturation and a PO2 of 100mmHg, when the Hb is 16g/100mls
answer on page 109
true of false: the higher the PO2 the higher the % saturation of Hb
true
100% saturation of Hb = 100 mmHg PO2
Solve Ryan’s problem (page 110)
Solve Ryan’s problem
➢ Hb = 12g/100mls
➢ PaO2 = 32mmHg (use this to find % saturation)
➢ % saturation = 0.63 (multiply this by 1.34)
➢ 0.63 x 1.34 = 0.8442 (multiple this by 12gHb/100mls)
➢ 10.1 vol%
