blood gas analysis 1

Question 1

role of blood gas analysis

Answer 1

to asses respiratory function
- oxygenation of blood
- removal of carbon dioxide
and, in practise
- diagnosis and monitoring of acid base disorders
- and more broadly, rapid point of care measurement of a range of analytes

Question 2

blood gas analysis is done with

Answer 2

point of care instruments

Question 3

disadvantages of POC testing

Answer 3

• may not be as accurate/precise - hard to troubleshoot
• usually significantly more expensive
• required training of clinicians
• time off floor for clinicians

Question 4

core tests

Answer 4

pCO2, pO2, pH, HCO3

often configured to measure na, K, Cl, heamoglobin, creatinine, glucose, ionised calcium, others

Question 5

arterial sample for blood gas

Answer 5

• more painful
• more technically difficult, usually requires a doctor to obtain
• provides useful information on oxygenation
• patients with arterial lines (ICU) are easily serially tested

Question 6

venous blood gas sample

Answer 6

• easier to obtain - unless patient has an arterial line
• rapid TAT at POC for a range of analytes
• provides nearly all the utility of arterial but no useful information on oxygenation (even if pO2 reported)

Question 7

PaO2

Answer 7

partial pressure of oxygen in aqueous part of arterial blood

Question 8

SaO2

Answer 8

percentage of oxygen binding sites in RBCs carrying oxygen in arterial blood

Question 9

SpO2

Answer 9

percentage of oxygen binding sites in RBCs carrying oxygen in arterial blood

Question 10

SaO2 is calculated from

Answer 10

calculated from haemoglobin concentration and PaO2 using formula, or measured by oximetry

Question 11

hypoxaemia is caused by

Answer 11

• hypoventilation
• dead space
• shunt
• diffusion limitation
  called type 1 respiratory failure

Question 12

hypercapnoea

Answer 12

• raised CO2
• caused by hypoventilation
• usually also associated with hypoxaemia, may not notice if patient is on supplemental oxygen
• supplimental oxygen does not correct hypercapnoea
  called type 2 respiratory failure

Question 13

hypoventilation causes

Answer 13

• decreased respiratory rate
• decreased respiratory volume
• restricted airways
• obesity

Question 14

type 1 respiratory failure is

Answer 14

hypoxaemia

Question 15

type 2 respiratory failure is

Answer 15

hypercapnoea

Question 16

conditions causing type 1 resp failure

Answer 16

pneumonia
interstitial lung disease
PE
pulmonary oedema

Question 17

conditions causing type 2 resp failure

Answer 17

COPD
asthma
neuromuscular disease (Guillain-barre, MND)
chest wall abnormalities

Question 18

3 major ways in which blood pH is controlled

Answer 18

• chemical buffer system - instant
• lungs - minutes
• kidneys - hours to days

Question 19

respiratory regulation

Answer 19

hydrogen ions stimulate respiratory centre causing increased respiration
increased alveolar ventilation removed more CO2
decreased alveolar ventilation permits retention of CO2

Question 20

increased pCO2 may indicate

Answer 20

primary respiratory acidosis

respiratory compensation for metabolic alkalosis

Question 21

decreased PCO2 may indicate

Answer 21

• primary respiratory alkalosis

- respiratory compensation for metabolic acidosis

Question 22

increased HCO3- may be

Answer 22

• primary metabolic alkalosis

- metabolic compensation for respiratory acidosis

Question 23

decreased HCO3- may be

Answer 23

• primary metabolic acidosis

- metabolic compensation for respiratory alkalosis