CVR arterial blood gases + AB regulation Flashcards
what is PO2?
the partial pressure of oxygen
what does the partial pressure of oxygen indicate?
how much O2 is dissolved in the arterial blood
what is PCO2?
the partial pressure of carbon dioxide
what does the partial pressure of carbon dioxide indicate?
how much CO2 is dissolved in arterial blood.
what can high pCO2 indicate and/or low pO2 indicate?
inadequate gas exchange in the lungs
what does pH describe?
This variable describes the acidity, neutrality or alkalinity of the blood.
The pH of arterial blood is finely tuned and small deviations can affect oxygen transport and delivery
what is HCO3-
plasma bicarbonate
This variable describes the concentration of bicarbonate dissolved in arterial blood. If plasma bicarbonate is higher or lower than normal, this could be evidence of gas exchange imbalance
what is BE?
this variable describes the concentration of bases (predominantly bicarbonate) compared with the ‘expected concentration’
what is BE when an exact match occurs?
0
- > excess of base is +ve
- > base deficit is -ve
pulmonary transit time:
how long erythrocytes are close enough to resp exchange surface to exchange gases
what is a normal pulmonary transit time (healthy person)
0.75 secs
how to convert [H+] into pH
-log10[H+]
What does the haematocrit show
proportion of RBC in whole blood
- %
what is an acid?
any molecule that has a loosely bound H+ that it can donate
-> called protons
what does unregulated pH cause?
alteration of the 3D structure of proteins
what term describes the charge of a base?
anionic charge - capable of reversibly binding protons
what are the 2 types of acids in the body (Categories)
- respiratory
- metabolic
what % of the acid we produce is respiratory?
99%
what is CO2 flux?
comparison of amount of CO2 in blood before and after it gets to tissues
-> around 200ml CO2/min (for each CO)
is blood the blood an effective acid/base buffer?
yes, it has an enormous capacity to do so.
what can changes in ventilation trigger?
rapid compensatory response to change CO2 and alter pH
what can slow a compensatory response to inc/dec pH?
HCO3 - and H+ retention/secretion
what does it mean if the term ends in ‘osis’ e.g. acidosis
describing circumstances that lead to a change
what does it mean if the term ends in ‘aemia’ e.g. acidaemia
the state that the body is in
is it possible for the body to be in acidosis whilst in a state of alkalaemia?
yes, this is a compensatory response
Interpretation procedure for arterial blood gases
- type of imbalance?
- aetiology of imbalance?
- any homestatic compensation?
- oxygenation?
options for interpreting arterial blood gases
1–>Type of imbalance:
- acidosis
- alkalosis
- normal
options for interpreting arterial blood gases
2–>aetiology of imbalance:
- Acidosis
- -> resp
- -> metabolic - Alkalosis
- -> resp
- -> metabolic
options for interpreting arterial blood gases
3–>any homeostatic compensation:
- uncompensated
- partially compensated
- Fully compensated
options for interpreting arterial blood gases
4–>oxygenation:
- hypoxaemia
- normoxaemia
- hyperoxaemia
how does bicarbonate move out of an erythrocyte?
AE1 transporter
cause of metabolic acidosis
diarrhoea
increased lactic acid production
cause of metabolic alkalosis
vomiting
