oxygen, respiratory failure and oxygen therapy

Question 1

what is PiO2?

Answer 1

partial pressure of inspired oxygen

Question 2

what is PaO2?

Answer 2

partial pressure of oxygen in arterial blood

Question 3

what is PAO2?

Answer 3

partial pressure of alveolar oxygen

Question 4

what is FiO2?

Answer 4

fraction of inspired oxygen

Question 5

what is ViO2?

Answer 5

volume of oxygen

Question 6

what is R?

Answer 6

respiratory quotient

Question 7

what is PaCO2?

Answer 7

partial pressure of CO2

Question 8

what is VA?

Answer 8

alveolar ventilation

Question 9

what is SVP?

Answer 9

saturated vapour pressure - measurement of amount of moisture in the air

Question 10

what is the oxygen cascade?

Answer 10

the decrease in oxygen as it passes from the atmosphere into the body and into the arterial circulation.

Question 11

what is the concentration of O2 in the air?

Answer 11

20.94%

Question 12

what is tracheal gas?

Answer 12

PO2 after humidification

Question 13

how do you calculate tracheal gas?

Answer 13

fractional concentration of oxygen in the dry gas phase x (barometric pressure – saturated vapor pressure)

Question 14

what factors affect alveolar gas?

Answer 14

• Hypo or ventilation
• Oxygen consumption
• CO2 production

Question 15

what is the equation for alveolar gas?

Answer 15

PAO2 = dry barometric pressure x (FiO2 – VO2/ VA).

Question 16

what is the normal PaO2?

Answer 16

13.6kPa

Question 17

what determines the alveolar to arterial PO2 difference?

Answer 17

shunting

Question 18

what is shunting?

Answer 18

an area of the lung that is perfused but not ventilated

Question 19

what happens to shunting in disease?

Answer 19

in disease, the amount of shunting increases

Question 20

what is the equation that shows the amount of oxygen delivered to the body in one minute?

Answer 20

(Hb) x Oxygen Saturation of Hb x 1.34 x CO.

1.34 is the oxygen binding capacity of Hb

Question 21

what is respiratory failure?

Answer 21

= Inadequate gas exchange, meaning that either PaO2 or PAO2 is not maintained at normal levels.

Question 22

why does oxygen decrease first in respiratory problems?

Answer 22

CO2 is easier to exchange than O2

Question 23

what are signs of respiratory failure?

Answer 23

• signs of respiratory compensation
• increased sympathetic tone
• end-organ hypoxia
• haemoglobin desaturation
• CO2 retention

Question 24

what are signs of respiratory compensation?

Answer 24

tachypnoea, use of accessory muscles, nasal flaring, intercostal or suprasternal recession

Question 25

what are signs of increased sympathetic tone?

Answer 25

tachycardia, hypertension, sweating

Question 26

what are signs of end organ hypoxia?

Answer 26

altered mental status, bradycardia and hypotension (late)

Question 27

what are signs of haemoglobin desaturation?

Answer 27

cyanosis

Question 28

what are signs of CO2 retention?

Answer 28

flap | bounding pulse

Question 29

what is type 1 respiratory failure?

Answer 29

hypoxia only

Question 30

why does type 1 respiratory failure occur?

Answer 30

Occurs because of damage to lung tissues. Damage prevents adequate oxygenation of the blood but the normal lung is still sufficient to excrete CO2 made by tissue metabolism.

Question 31

name examples of type 1 respiratory failure

Answer 31

* Pulmonary oedema * Pulmonary fibrosis * Asthma * Pneumothorax * Pneumonia * Obesity

Question 32

what is type 2 respiratory failure

Answer 32

type 1 with fatigue; hypoxaemia and hypercapnia (PaO2 < 8 and PaCO2 > 6.5).

Question 33

name types of type 2 respiratory failure

Answer 33

* Drug overdose  most common cause * Severe asthma (fish diagram) * Poisonings * Head/cervical cord injury.

Question 34

what are causes of hypoventilation?

Answer 34

brainstem, metabolic encephalopathy, depressant drugs, spinal cord, nerve root injury, nerve trauma, neuropathy, neuromuscular junction, respiratory muscles, airway obstruction, decreased lung or chest wall compliance

Question 35

what is the first line of treatment of respiratory failure?

Answer 35

oxygen

Question 36

what are indications of O2 therapy?

Answer 36

* Respiratory failure * Cardiac arrest * Tachypnoea * Cyanosis * Hypotension * Metabolic acidosis

Question 37

what patients are given oxygen masks with nasal cannula?

Answer 37

patients with normal vital signs

Question 38

what patients are given face masks with reservoir bags and why?

Answer 38

patients in an emergency - higher O2 concentration

Question 39

when are venturi masks used?

Answer 39

controlled treatment in long term respiratory failure

Question 40

what are low flow masks?

Answer 40

nasal cannulase, face mask, mask with reservoir bag

Question 41

what are high flow masks?

Answer 41

Venturi masks: deliver O2 at a rate above peak IFR, deliver fixed concentration

Question 42

when should pulse oximetry be started?

Answer 42

should be started immediatel

Question 43

what is the critical threshold for pulse oximetry?

Answer 43

94%

Question 44

what is the purpose of arterial blood gases?

Answer 44

Used to keep the FiO2 (fraction of inspired O2) at a minimum required to achieve adequate O2

Question 45

why is oxygen toxic?

Answer 45

produces free radicals that can damage the body

Question 46

in how many COPD patients will the CO2 go up if given O2?

Answer 46

10%

Question 47

what treatment do you give if the CO2 retention isnt known?

Answer 47

o Start high flow of oxygen. o Monitor for drowsiness. o Check ABG after 30 minutes.

Question 48

what treatment is given if CO2 retention is known?

Answer 48

o Set up a controlled mask. o Titrate for lowest possible O2. o Measure ABG as soon as possible. o Repeat ABG 30 minutes later.

Question 49

what is ventilation used for?

Answer 49

* Not for hypoxia | * Used for hypercapnia (due to hypoventilation).