Acid Base balance & arterial blood gas Flashcards
pH< 7.35
pH > 7.45
pH between 7.35 nd 7.45?
1) acidosis
2) alkalosis
3) this is either normal or has a mixed acid base balance.
what are the buffer for acid base balance?
- proteins
- haemoglobin
- carbonic acid/bicarbonate
where will acid/ alkali be excreted from?
lungs
kidneys
what are the normal values of ABG?
pH
pO2
pCO2
bicarbonate
pH= 7.35-7.45
pO2= 12-13 kPa
pCO2 = 4.5- 5.6 kPa
bicarbonate = 22-26 mol/l
when will acid base disturbances occur?
when…
- there is a problem with ventilation
- there is a problem with renal function
- overwhelming acid or base load the body can’t handle.
step 1 interpretation of ABG results
assess the oxygenation (look at pO2)
if someone is hypoxic and has a very low RR, what is most likely going on?
this would suggest that they have chronic cyanosis which means the body has become used to this increased firing.
what are the different ways to measure oxygenation?
pulse oximetry
what if there if a low pO2, what may there be a problem with?
There may be a problem with:
- getting oxygen into the lungs
- oxygen getting into the blood
- oxygenation of tissues.
high pO2, what can this cause?
- retinal damage
- mucus membrane damage
- alveoli collapse
what are the adverse effects of high oxygen levels?
- increased risk of hypercapnic respiratory failure in acute exacerbations of COPD
- increased mortality survivors of cardiac arrest
- increased mortality in intensive care patients
- increased mortality in acute severe asthma.
why are high oxygen levels bad?
- generate free radicles
- collapse of alveoli due to atelectasis
- irritation to mucus membranes
…. leads to ocular toxicity, myocardial damage, neuro damage etc …
what is the British thoracic society guidelines?
- oxygen is a treatment for hypoxia not dyspnoea alone.
- in an unstable medical emergency give high conc of oxygen then titrate to target once stable.
- target 94-96% normally
- 88-92% for type 2 respiratory failure.
step 2 interpretation of ABG results?
assess the PH
pH< 7.35 is acidosis
ph> 7.45 is alkalosis
pH between 7.35 and 7.45 = normal or mixed acid base abnormality
acidosis ?
alkalosis?
acidosis= too much pco2 and you cannot get rid of it.
alkalosis= too little pCO2.