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Anesthesiology > Ventilation and Oxygenation > Flashcards

Flashcards in Ventilation and Oxygenation Deck (37)
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1
Q

High PaCO2

A

Hypoventilation; hypercarbia

2
Q

Low PaCO2

A

Hyperventilation; hypocarbia

3
Q

Normal arterial CO2

A

~35-45mmHg

4
Q

What causes hypercarbia?

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

Make sure the equipment is working properly!!!

5
Q

What causes hypocarbia?

A
  1. Hyperventilation

2. Hypothermia

6
Q

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

A

True, controlled by medullary centers of the brain stem

7
Q

T/F: all anesthetics are respiratory depressants

A

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

8
Q

What else can contribute to respiratory depression

A
  1. Mechanical obstruction (obesity, pregnancy, mass)

2. Positional (head down/butt up position

9
Q

What causes decreased compliance in the lungs?

A

Pneumothorax, pulmonary edema, rigid chest wall

Anything that prevents the chest the expand

10
Q

What does a respirometer measure?

A

Volume that is exhaled

11
Q

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

A

CO2

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

12
Q

What is the standard for measuring CO2 levels?

A

Capnometry

13
Q

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

A

True

14
Q

Two types of capnometry

A
  1. Sidestream- sensor and display are diverted from airway

2. Mainstream- sensor is in line with the airway

15
Q

Advantages of mainstream capnometry

A

Not as affected by dilution with fresh gaas

16
Q

Disadvantages of mainstream capnometry

A

More expensive if cuvette is damaged

Adds dead space

17
Q

Advantages of sidestream capnometry

A

Tubing less expensive

Less added dead space

18
Q

Disadvantages of sidestream capnometry

A

Large underestimation in small patients due to gas dilution

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

19
Q

What is the target EtCO2 in a healthy patient?

A

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

20
Q

Is EtCO2 typically higher or lower than PaCO2?

A

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

21
Q

Consequences of high PCO2

A
  1. Respiratory acidosis
  2. Hypoxia
  3. Sympathetic activation
  4. Unconsciousness, coma, hypotension
  5. Atelectasis
22
Q

Why is keeping PCO2 low especially important for neurologic patients?

A

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

Should be kept 2540mmHg

23
Q

Consequences of low PCO2

A
  1. Respiratory alkalosis and metabolic acidemia
24
Q

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

A

Less

25
Q

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

A

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

26
Q

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

A

True; cardiac oscillations pushing against the lungs

27
Q

Rebreathing capnograph

A

Wave does not return to baseline

28
Q

What does pulse oximetry tell us

A

HR, O2 saturation%

29
Q

What does pulse oximetry estimate?

A

Hemoglobin-O2 saturation

30
Q

Transmission probes

A

LED light passes through tissues and transmitted light is measured

31
Q

Reluctance probe

A

Both LEDs on the same side and reflected light is measured

32
Q

What is a normal SpO2

A

> 97%

Horses

33
Q

Causes of hypoxemia

A
  1. Pulmonary dysfunction (decreased perfusion or atelectasis)
  2. Pneumo- or hemothorax
  3. Respiratory depression with no O2 supplementation
34
Q

Why do we use pulseox?

A

Monitor oxygen levels especially for at-risk patients

35
Q

Limitations of pulseox

A
  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
Q

Does anemia effect the SpO2?

A

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

37
Q

Does inspired O2% effect SpO2?

A

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