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Flashcards in Ventilation and Oxygenation Deck (37):
1

High PaCO2

Hypoventilation; hypercarbia

2

Low PaCO2

Hyperventilation; hypocarbia

3

Normal arterial CO2

~35-45mmHg

4

What causes hypercarbia?

1. Inadequate elimination (hypoventilation)
2. Increased metabolism (malignant hyperthermia)

Make sure the equipment is working properly!!!

5

What causes hypocarbia?

1. Hyperventilation
2. Hypothermia

6

T/F: CO2 is the main stimulus to breathing.

True, controlled by medullary centers of the brain stem

7

T/F: all anesthetics are respiratory depressants

True, more profound depths of anesthesia have more respiratory depression by increasing the CO2 stim threshold

8

What else can contribute to respiratory depression

1. Mechanical obstruction (obesity, pregnancy, mass)
2. Positional (head down/butt up position

9

What causes decreased compliance in the lungs?

Pneumothorax, pulmonary edema, rigid chest wall

Anything that prevents the chest the expand

10

What does a respirometer measure?

Volume that is exhaled

11

Is it better to measure CO2 or RR as an assessment of adequate ventilation?

CO2

Breathing rate can be slow if the depth of breath is increased

12

What is the standard for measuring CO2 levels?

Capnometry

13

T/F: ETCO2 is a good approximation of the PaCO2.

True

14

Two types of capnometry

1. Sidestream- sensor and display are diverted from airway
2. Mainstream- sensor is in line with the airway

15

Advantages of mainstream capnometry

Not as affected by dilution with fresh gaas

16

Disadvantages of mainstream capnometry

More expensive if cuvette is damaged

Adds dead space

17

Advantages of sidestream capnometry

Tubing less expensive

Less added dead space

18

Disadvantages of sidestream capnometry

Large underestimation in small patients due to gas dilution

Tubing collects a lot of moisture and needs to be replaced more often

19

What is the target EtCO2 in a healthy patient?

up to 50-60mmHg usually acceptable but should be kept below 60mmHg

20

Is EtCO2 typically higher or lower than PaCO2?

Lower; usually ~3-7mmHg but can be much larger

21

Consequences of high PCO2

1. Respiratory acidosis
2. Hypoxia
3. Sympathetic activation
4. Unconsciousness, coma, hypotension
5. Atelectasis

22

Why is keeping PCO2 low especially important for neurologic patients?

Increased CO2 can lead to dilation of the cerebral pressure and increased ICP

Should be kept 2540mmHg

23

Consequences of low PCO2

1. Respiratory alkalosis and metabolic acidemia

24

When EtCO2 is low there is less/more circulation to the lungs.

Less

25

T/F: EtCO2 is a good predictor for recovery during CPR.

True; if EtCO2 is low, it is unlikely the animal will recover

26

T/F: It is normal to find small depressions in the capnograph.

True; cardiac oscillations pushing against the lungs

27

Rebreathing capnograph

Wave does not return to baseline

28

What does pulse oximetry tell us

HR, O2 saturation%

29

What does pulse oximetry estimate?

Hemoglobin-O2 saturation

30

Transmission probes

LED light passes through tissues and transmitted light is measured

31

Reluctance probe

Both LEDs on the same side and reflected light is measured

32

What is a normal SpO2

>97%

Horses

33

Causes of hypoxemia

1. Pulmonary dysfunction (decreased perfusion or atelectasis)
2. Pneumo- or hemothorax
3. Respiratory depression with no O2 supplementation

34

Why do we use pulseox?

Monitor oxygen levels especially for at-risk patients

35

Limitations of pulseox

1. Vasoconstriction
2. Fur/pigmentation
3. Movement
4. Usually over estimates at low end and under estimates at high end
5. Cannot distinguish from other types of hemoglobins
6. Ambient light may interfere

36

Does anemia effect the SpO2?

Shape of the curve stays the same but the O2 content is reduced

37

Does inspired O2% effect SpO2?

No, it has a profound effect on PaO2 but hypoxemia is more likely if breathing room air