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Acute > W4: MC > Flashcards

W4: MC Flashcards

1
Q

What does oxygen saturation indicate?

A

The oxygen carrying capability of blood

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2
Q

What is the difference between Sa02 or Pa02?

A

Sa02 = oxygen bound to haemoglobin
Pa02 = oxygen dissolved in blood

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3
Q

What is haemoglobin?

A

A protein in RBCs that carries oxygen from the lungs to the tissues throughout the body

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4
Q

Oxygen loading

When red blood cells pass through the lungs, …… molecules in the cells bind to oxygen molecules. This binding happens because the lungs have a …… concentration of oxygen so oxygen molecules diffuse into the RBCs and bind to the iron atoms in haemoglobin. At this point haemoglobin is considered ….. ….. with oxygen.

Oxygen release

As the red blood cells reach the …… (the smallest blood vessels) in the tissues, the oxygen concentration in the surrounding tissues is …… than in the red blood cells. This concentration gradient causes the haemoglobin to release the …… molecules. Essentially, haemoglobin unloads its oxygen where it’s needed most.

A

Haemoglobin
High
Well saturated
Capillaries
Lower
Oxygen

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5
Q

There are two ways to measure oxygen saturation - what are they? What are the normal ranges for each?

A

Sp02 = pulse oximetry (95-100%)
Sa02 = ABGs (normal range 80-100mmHg)

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6
Q

What is the medical term for when Pa02 & Sp/Sa02 are low? What is the range for this? What does this result in?

A

Hypoxaemia. <60-80 (increasing degree of brain dysfunction - prefrontal, cerebellar, muscle paralysis)

This causes hypoxia which is when insufficient oxygen is transported and delivered to the tissues

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7
Q

How does pulse oximetry work?

A

It shines two separate light beams into the blood circulating in the capillaries.

These light beams reflect oxygen saturation, expressed as a %, along with the pulse rate.

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8
Q

What can pulse oximetry detect and how accurate is it?

A
  • Accurate in high saturation readings, but not in low readings, with an overall accuracy of +/- 2%.
  • Doesn’t detect an increase in the partial pressure of carbon dioxide (PaCO2) (i.e., with oxygen therapy, you may have a normal SpO2 but abnormal PaCO2)
  • Inaccurate in the presence of poor peripheral circulation (e.g., cold extremities, cardiac failure).
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9
Q

What do arterial blood gases measure?

A

The partial pressure of oxygen (Pa02). Pa02 is the actual oxygen content of oxygen in arterial blood.

As well as the amount of carbon dioxide and pH level of blood.

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10
Q

What is a downside to ABG’s compared to pulse oximetry?

A

More invasive- it requires a blood sample and also takes longer for results (lab testing)

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11
Q

Normal ABG reading?

A

80-100mmHg –> good delivery of 02 to the tissues

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12
Q

What would a higher Pa02 suggest?

A

Hamoglobin rapidly binds with oxygen until it reaches its maximum capacity, or saturation. This is because hemoglobin has a higher affinity for oxygen when there’s plenty of it around.

Once haemoglobin is fully saturated, it can’t carry any more oxygen, so any additional oxygen in the blood is not taken up by haemoglobin but remains dissolved in the plasma.

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13
Q

Acute hypoxaemia

Pa02 < 60mmHG: stimulates …… (Decreased …..)
Pa02 < 55mmHG: symptoms?
Pa02 < 30mmHg: results in?

A
  • Stimulates ventilation (decreased PaC02)
  • Short-term memory alteration, confusion & euphoria
  • Loss of consciousness
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14
Q

General symptoms of acute hypoxaemia

A
  • Tachycardia, increased CO, arrythmias, systemic hypotension (peripheral vasodilation)
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15
Q

Chronic hypoxaemia - consequences?

A
  • Polycythemia hypoxaemia
  • Pulmonary hypertension
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16
Q

What is the relationship between Sa02 and Pa02?

A

Sigmoidal shape (S-shape)
- When Pa02 is low, Sp02 will be low (& vice versa)
- The relationship is NOT proportional

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17
Q

Estimated Sa02 based of Pa02?
- 80-100mmHg
- < 80mmHg
- <60mmHg

A
  • 95-100%
  • <95%
  • <90%
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18
Q

S-shape relationship of Sa02 and Pa02

Sigmoidal shape: This means that as one oxygen molecule binds to a heme group, it …… …… ….. of the remaining heme groups for oxygen

Steep Slope: At lower PaO2 levels (below ….. mmHg), the curve is ……. Small changes in PaO2 result in …… changes in SaO2. This is crucial for oxygen loading in the lungs and unloading in the tissues

Plateau Phase: At higher PaO2 levels (above 60 mmHg), the curve ……. Here, even large increases in PaO2 cause only ….. increases in SaO2. This plateau provides a safety margin, ensuring that haemoglobin remains ….. …….. with oxygen even if Pa02 drops slightly

A

It increases the affinity
60mmHg
Steep
Significant
Plateaus
Small
Highly saturated

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19
Q

Three main features of the Sa02 & Pa02 curve?

A
  • Sigmoidal shape
  • Steep slope
  • Plateau phase
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20
Q

Pa02 can only be measured by?

A

Arterial blood gas sample

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21
Q

Spa02 can be measured by?

A

Arterial blood gas sample
Pulse oximetry

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22
Q

When recording Pa02 and Spa02, you must record what?

A
  1. Level of oxygen the patient is on
  2. What sort of oxygen therapy (nasal prongs, mask)
23
Q

Interpreting Pa02

  • When we breathe in air, the concentration of oxygen is not ….%. It is a mix of …..
  • The fraction of inspired O2 (FiO2) is …… when we are breathing room air (RA).
  • To interpret PaO2 values, the ……
A
  • 100%
  • Oxygen combined with other gases
  • 0.21 (21%)
  • % oxygen they are breathing in must be considered.

Note: a PaO2 of 90 when a person is breathing room air has a different meaning to a PaO2 of 90 when the person is receiving supplementary oxygen.

When patients are on 02 therapy, the Fi02 will be > 0.21

24
Q

What is the formula used to interpret Pa02? What is the normal level?

A

Pa02/Fi02 (P/F ratio).
>500mmHg

25
Q

In terms of acute respiratory disease syndrome (ARDS) what is the mild rating of Pa02/Fi02 & mortality?

A

Mild 200-300
Mortality: 27%

26
Q

Respiratory reserve….
- 300 indicates….
- 200 to 300 indicates…
- <200 indicates….

A
  • 300 = sufficient respiratory reserve
  • 200-300 = a marginal reserve
  • <200 = little or no reserve & need for extreme care when mobilising
27
Q

In terms of acute respiratory disease syndrome (ARDS) what is the moderate rating of Pa02/Fi02 & mortality?

A

Moderate: 100-200
Mortality: 32%

28
Q

In terms of acute respiratory disease syndrome (ARDS) what is the severe rating of Pa02/Fi02 & mortality?

A

Severe < 100
Mortality: 45%

29
Q

Summary of normal oxygen values
- Fi02: normal?
- Pa02: Normal, hypoxemia & severe hypoxemia?
- Sa02: Normal, hypoxemia & severe hypoxemia

A
  • Normal: 21%
  • Normal 80-100, < 80 =hypoxemia, severe hypoxemia = <60
  • Normal: 95-100%, hypoxemia = <95%, severe hypoxemia = <90%
30
Q

If any of the following are impaired what impairment can you say the patient has?

  • Sp02
  • Sa02
  • Pa02
  • Pa02/Fi02
A

Oxygen movement impairment

31
Q

What does pH refer to?

A
  • pH refers to the acid-base balance of the body which is required for homeostasis and many biological processes
32
Q

What is the normal pH level? Range compatabile with life

A

7.35-7.45

Maximum range compatible with life: 6.80-7.80

33
Q

Define acidemia?

A

A low pH level in the blood (pH <7.35)

34
Q

Define alkalemia

A

A high pH level in the blood (pH > 7.45)

35
Q

Define acidosis

A

A physiological process that lowers the blood pH (causes acidemia)

36
Q

Define alkalosis

A

A physiological process that raises the pH of blood

37
Q

Carbon dioxide is a by product of….

A

Metabolism

38
Q

Carbon dioxide is transported by the ….. to the ….. where it is removed from the body via ….

A

Bloodstream
Lungs
Exhalation

39
Q

C02 has a role in regulating…..

A

pH and respiratory drive

40
Q

Normal C02 is …..mmHg

A

35-45mmHg

41
Q

When there are high levels of C02 in the blood, the rate of respiration may …….

Hypoventilation vs hyperventilation? Do these mechanisms result in high or low Pac02? Explain

A

Change to assist with its removal
Hypoventilation (slow breathing) –> high PaC02 (acidosis)
Hyperventilation (fast breathing) –> low PaC02 (Alkalemia)

42
Q

Describe the effects of C02 on ventilation (5 steps)

A
  1. Increase in C02 level in the blood (hypercapnia)
  2. Decrease in blood pH (acidosis)
  3. Stimulates central chemoreceptors
  4. Stimulates phrenic nerve and intercostal muscles
  5. Increased respiration muscle activity to increase the depth/rate of respiration (alveolar hyperventilation) until normal PaC02 and pH levels are restored
43
Q

If you have an increased PaC02 (or respiratory acidosis) you can say that the patient has a …..

A

Carbon dioxide movement impairment

44
Q

PaCO2 is the …..

A

partial pressure of carbon dioxide dissolved in arterial blood (N 35-45).

45
Q

What is bicarbonate (HC03)

A
  • The bicarbonate ion (HCO3–) is the acid-base component regulated by the kidneys.
  • Acting as the body’s buffer system, the kidneys retain or excrete the alkalotic HCO3– as needed.
46
Q

Normal levels of bicarbonate?

A
  • Normal HCO3 is 22-26 mEq/L.
47
Q

If the Hc03 decreases what happens to the reaction?

A
  • Reaction shifts to (right) pH acidaemia
48
Q

If the Hc03 increases what happens to the reaction?

A
  • Reaction shifts to the left
49
Q

What is base excess?

A
  • Base Excess (BE) is the amount of acid required to restore a litre of blood to its normal pH at a PaCO2 of 40 mmHg
50
Q

What happens to base excess in metabolic alkalosis and in metabolic acidosis? Normal range?

A

Metabolic alkalosis: Increases
Metabolic acidosis: Decreases
Normal range (-2 to +2 mEq)

Note:
* If BE is < -2, it means the body has a base DEFICIT
* If BE is > +2, it mean the body has a base EXCESS

51
Q

Effect of pH, PaC02, HCO3, Base excess in abnormal acidic?

A

pH = L
Pac02 = H
HC03 = L
Base excess = L

52
Q

Effect of pH, PaC02, HCO3, Base excess in abnormal alkalinic?

A

pH = H
Pac02 = L
HC03 = H
Base excess = H

53
Q

If the CO2 or HCO3 moves in the opposite direction to the pH, there is a system compensating. Explain?

A

Respiratory system imbalanced = metabolic system compensating

Metabolic system imbalanced= respiratory system compensating

Acute (14 decks)

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