Critical care

Question 1

What are the components of ABG analysis?

Answer 1

pH
PaO2
PaCO2
HCO3
Base excess (BE)
SaO2

*Note: Difference between PaO2 and SaO2:
- PaO₂ measures oxygen in plasma (dissolved oxygen), while SaO₂ measures oxygen bound to hemoglobin (Reflects oxygen-carrying capacity but not the amount of oxygen dissolved in plasma)

Question 2

Difference between BIPAP and CPAP

Answer 2

BiPAP: used for pts with cardiopulmonary disorders such as CHF and lung disorders (can be used to prevent snoring & sleep apnea), have better ability to lower paCO2

CPAP: only used when alveolar collapse suspected, when continuous positive pressure is required

Question 3

Indications for mechanical ventilation (settings will not be tested)

Answer 3

inadequate ventilation to maintain pH

inadequate oxygenation

excessive breathing workload

congestive cardiac failure

++ add more

Question 4

Goals of mechanical ventilation

Answer 4

1. Reduce work of breathing
2. Minimise work of myocardium
3. Restore normal acid/base vol

4.

Question 5

Physiology, what makes up an intact ventilation

Answer 5

Breathe in oxygen, breathe out CO2

Question 6

physiology of oxygenation

Answer 6

simple diffusion process at pulmonary-capillary bed

Question 7

diffusion requirements

Answer 7

intact, non-thickened ++ READ SLIDES

Question 8

physiology of perfusion

Answer 8

process of circulating blood thru the capillary bed

Question 9

perfusion requirements

Answer 9

adequate blood volume
adequate hemoglobin
intact, non-occluded pulmonary capillaries
functioning heart

Question 10

relationship between heart and lungs (normal ventilation perfusion) (V/Q)

Question 11

impaired ventilation (low V/Q) - what treatment is it responsive to?

Answer 11

low V/Q is responsive to treatment with oxygen bc the airways are only partially obstructed, so it is possible for oxygen to enter the alveoli by diffusion

Question 13

very low V/Q treatment

Answer 13

although pulmonary shunt is similar to low V/Q in affected low arterial oxygen levels, true shunt is not responsive to oxygen therapy bc the alveoli are collapsed or consolidated and oxygen cannot gain entry into them

Question 14

causes of respi failure (type 1 and 2)

Question 15

pathophysiolofy of hyperpoxemia???

Question 16

pathophysiology of hypercapnia

Question 17

pathophysiology of ARDS

Question 18

Stages (1-4) of ARDS

Question 19

Normal range of pH in ABG

Answer 19

7.35 to 7.45

Question 20

Normal range of PaO2 in ABG

Answer 20

80 to 100 mmHg

Question 21

Normal range of PaCO2 in ABG

Answer 21

35 to 45 mmHg

Question 22

Normal range of HCO3 in ABG

Answer 22

22 to 26 mEq/L

Question 23

Normal range of base excess (BE) in ABG

Answer 23

-2 to +2 mEq/L

Question 24

Normal range of SaO2 in ABG

Answer 24

95-100%

Question 25

How do we determine respiratory acidosis from pH, pCO2 and HCO3 levels?

Answer 25

Respi acidosis:
pH: LOW
pCO2: HIGH
HCO3: Neutral

*note: pCO2 affected in Respi alkalosis/acidosis

Question 26

How do we determine respiratory alkalosis from pH, pCO2 and HCO3 levels?

Answer 26

Respi alkalosis:
pH: HIGH
pCO2: LOW
HCO3: Neutral

*note: pCO2 affected in Respi alkalosis/acidosis

Question 27

How do we determine metabolic acidosis from pH, pCO2 and HCO3 levels?

Answer 27

Metabolic acidosis:
pH: LOW
pCO2: Neutral
HCO3: LOW

*note: HCO3 affected in Metabolic acidosis/alkalosis

Question 28

How do we determine metabolic alkalosis from pH, pCO2 and HCO3 levels?

Answer 28

Metabolic alkalosis:
pH: HIGH
pCO2: Neutral
HCO3: HIGH

*note: HCO3 affected in Metabolic acidosis/alkalosis

Question 29

How to tell the difference between partially and fully compensated states?

Answer 29

Look at pH.

Has pH returned to normal?

If yes, it is fully compensated.

Question 30

How will the body compensate metabolically if pCO2 is high? How does compensation in body take place?

Answer 30

The body compensates metabolically via the renal system by:

• (Kidneys) Reabsorbing bicarbonate (HCO₃⁻) into the bloodstream
• Excreting hydrogen ions (H⁺) in the urine, often as ammonium (NH₄⁺) or dihydrogen phosphate (H₂PO₄⁻).

This increased HCO₃⁻ raises the blood pH, counteracting the acidosis caused by high pCO₂.

*note: High pCO₂ triggers renal compensation.

Question 31

What is the anion gap concept? What is it used for?

Answer 31

Used to identify the cause of metabolic acidosis (primarily due to ELECTROLYTE IMBALANCE)

Helps to distinguish between anion-gap and non-anion-gap metabolic acidosis

It represents the disparity between major measured plasma cations (Na+ and K+) and anions (Cl- and HCO3-)

Question 32

What is the normal anion gap range?

Answer 32

8-16 mmol/L

Question 33

In what cases will you see a raised anion gap? (>16 mmol/L)

Answer 33

Overdoses of paracetamol, salicylates, methanol or ethylene glycol

Question 34

In what cases will you see a normal anion gap?

Answer 34

If a metabolic acidosis is due to diarrhoea or urinary loss of bicarbonate.

Question 35

What is base excess?

Answer 35

It represents the amount of acid needed to bring the pH of the blood to 7.40, assuming a normal pCO₂ of 40 mmHg.

Question 36

How to interpret base excess in ABG?

Answer 36

Base excess guides us whether pt has metabolic acid/alkalosis

Normal range: -3 to + 3 mEq/L (METABOLIC ACIDOSIS TO METABOLIC ALKALOSIS)

e.g. if BE: -8, paO2, pCO2 normal: have metabolic acidosis

Question 37

What is non-invasive ventilation (NIV) and what types are there?

Answer 37

A method of providing ventilatory support without the need for an invasive procedure, such as intubation. It delivers pressurized air/oxygen through a tightly fitting mask

Modes of delivery:
CPAP (Continuous Positive Airway Pressure)

BiPAP (Bi-level Positive Airway Pressure)

Used for managing acute and chronic respiratory failure.