pulse oximetry and ABGs

Question 1

pulse oximetry

Answer 1

measures arterial oxygen saturation. oxygen is transported in RBC by haemoglobin molecule (Hb), each molecule being able to carry 4 oxygen mules= fully saturated. Saturated Hb and unsaturated Hb absorb different amounts of light

Question 2

haemoglobin structure

Answer 2

2 alpha chain, 2 beta chains haem molecules on each chain- haem.

Question 3

how does pulse ox work

Answer 3

light source passes infrared light through finger to photodetector on other side

Question 4

pulse oximetry and its relationship with Pa02

Answer 4

arterial saturation has a relationship with actual arterial oxygenation. 92% saturation correlates with adequate arterial oxygenation. less than 90% correlates with hypoxaemia

Question 5

clinical use

Answer 5

sensor usually attached to finger but can use toe or ear lobe (pulsating arteriolar bed), gives instant feedback of arterial oxygen saturation
assessment tool- pre-treatment and during treatment, outcome measure- post treatment

Question 6

what is sensor affected by

Answer 6

movement, nicotine stains, clubbing, bruising, nail posh

Question 7

arterial blood gases

Answer 7

a diagnostic performed on blood taken from artery. it gives information on the acid-base balance and the oxygenation of arterial blood. changes in respiratory mechanics (disorders of ventilation) and changes in the respiratory system that impedes diffusion (disorders of oxygenation) results in a change in the levels O2 and CO2. changes to the renal system will also alter bicarbonate levels

Question 8

procedure- how is sample obtaiend

Answer 8

sample is obtained either through a catheter placed in an artery or by using a needle and syringe to puncture an artery.

Question 9

arterial stab

Answer 9

radial (1st choice), brachial, femoral

Question 10

complications

Answer 10

arteriospasm, haematoma, nerve damage, fainting or vasovagal response, others- decreased BP, sweating

Question 11

acid-base balance- pH

Answer 11

is a measurement of acidity or alkalinity of the blood, pH of solution is measured on a scale of 1 (very acidic) to 14 (very alkoltic). A liquid with a pH of 7, such as water in neutral

Question 12

blood pH

Answer 12

normal blood range 7.35-7.45, in order for normal metabolism, in order for normal metabolism to take place, the body must maintain this narrow range at all times through homeostatic mechanisms

Question 13

what values are we looking at with ABGs

Answer 13

pH (hydrogen ion)- 7.35 -7.45, paCO2- 4.7-6kPa, HCO3- 22-26 mEq/l,
oxygenation- PaO2- partial pressure of oxygen= 10-14kPA

Question 14

common terminology

Answer 14

acid- gives up hydrogen ions, base- receives hydrogen ion, acidosis- abnormal process that lowers pH, alkalosis- abnormal process that raises pH, compensation- the process that returns pH to normal

Question 15

what can go wrong- acidosis

Answer 15

when the pH is below 7.35, the blood is said to acidic, there are only 2 ways in which an acidotic state can exist- too much CO2 in the blood PaCo2, too little bicarbonate in the blood HC03

Question 16

what can go wrong- alkalosis

Answer 16

when the pH is above 7.45, the blood is said to be alkalotic, there are only 2 ways in which an alkalotic state can exist- too little carbon dioxide in the blood (PaCO2), too much bicarbonate in the blood (HCO3)

Question 17

what can significant changes in blood pH

Answer 17

7.8-6.8 will interfere with cellular functioning, enzyme action, and if uncorrected, will lead to death

Question 18

acid/ base disturbances

Answer 18

respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis