Ventilator Management

Question 1

Extubation criteria:

Answer 1

Vital Capacity > 15 cc/kg, Negative Inspiratory Force < -25 mmH2O, Rate < 30/min, Tidal Volume > 5 cc/kg, PaO2 > 300 mmHg on FiO2 1.0, PaO2 > 70 mmHg on FiO2 0.21, PaCO2 < 45 mmHg, Sustained Head Life > 5 seconds, Normothermic, Hemodynamically Stable

Question 2

Iron lungs resemble normal lung mechanics, provide negative pressure for chest wall/lung to expand. Y/N?

Answer 2

Y

Question 3

What are the two types of ventilators?

Answer 3

Manual (bag mask–ambu bag; T piece–mapleson); Mechanical (bellow–ascending vs descending; piston)

Question 4

Contraindications for bag mask ventilation?

Answer 4

Severe facial trauma or open eye injuries; foreign body in oral cavity

Question 5

What’s Volume-Cycled Ventilation?

Answer 5

Lung inflation to a pre-set value; Alveolar ventilation stable despite pulmonary compliance

Question 6

What’s Pressure-Cycled Ventilation

Answer 6

Lung inflation to a pre-set pressure; Decrease risk of barotraumas.

Question 7

Pros and Cons for pressure controlled?

Answer 7

Better control of peak airway pressure, Inspiratory flow decreases exponentially during inflation (constant in volume cycled ventilation), Decreasing flow reduces peak airway pressure and can improve gas exchange; Volumes more prone to change with changes in pulmonary compliance

Question 8

Pros and Cons for pressure support?

Answer 8

Supply pressure to overcome resistance in breathing circuit, Allows patient to determine respiratory parameters, Augmentation of spontaneous breathing; Does not provide full ventilatory support (if pt doesn’t trigger, it won’t give a breath)

Question 9

Indications for volume controlled ventilation?

Answer 9

Consistent tidal volume is desired; excess pressure is not a major concern; no circuit leaks

Question 10

Indications for pressure controlled ventilation?

Answer 10

Small leaks in circuit (eg, uncuffed ETT); older anesthesia ventilators not capable of accurate volume ventilation; pts with respiratory distress syndrome requiring increased inspiratory pressures

Question 11

Tachypnea can lead to alkalosis and auto PEEP under assist-controlled ventilation mode. Y/N?

Answer 11

Y

Question 12

In assist-controlled ventilation mode, pt can trigger a breath if they generate enough negative pressure, and it delivers a full breath. Y/N?

Answer 12

Y

Question 13

What’s pressure support ventilation?

Answer 13

Detects inspiration and augments spontaneous breath by adding pressure during inspiration. Can also provide a set amount of PEEP

Question 14

What’s SIMV?

Answer 14

Spontaneous efforts trigger breaths which are pre-set with either volume control or pressure control and respiratory rate. Spontaneous breaths exceed the pre-set rate can trigger pressure support breaths if PSV is combined with SIMV in the setting

Question 15

Most often used mode in the OR for adults?

Answer 15

Volume controlled

Question 16

Best mode for transfusion-reaction pt, aspiration risk pt, ARDS pt?

Answer 16

Pressure controlled

Question 17

Difference between peak pressure and plateau pressure is the resistive pressure - due to _____?

Answer 17

tube kinking, bronchospasm, increased secretions

Question 18

Increase in airflow will also increase resistive pressure. Y/N?

Answer 18

Y

Question 19

What affects end inspiratory peak pressure?

Answer 19

inflation volume; flow resistance; elastic recoil force of the lungs & chest

Question 20

Causes for increased peak inspiratory pressure and increased plateau pressure?

Answer 20

Increased tidal volume, decreased pulmonary compliance (pulmonary edema, trendelenburg, pleural effusion, tension pneumothorax, endobronchial intubation, abdominal gas insufflations)

Question 21

Causes for increased peak inspiratory pressure and unchanged plateau pressure?

Answer 21

Increased fresh gas flow, increased airway resistance (kinked ETT, bronchospasm, secretions/blood, foreign body aspiration, airway compression, ETT cuff herniation)

Question 22

PEEP ➙ Alveolar pressure > Atmospheric pressure at end expiration. Y/N?

Answer 22

Y

Question 23

PaO2 can be manipulated by:

Answer 23

FiO2, Alveolar Pressure, Ventilation, Ventilation - Perfusion Matching

Question 24

Intrinsic PEEP can be bad because it can stack up the volume and over extend pt’s lung. Y/N?

Answer 24

Y

Question 25

Low tidal volumes can lead to___; High tidal volumes can lead to____

Answer 25

atelectasis; auto-PEEP

Question 26

Pros and Cons for longer inspiratory time(bigger I:E ratio):

Answer 26

improve oxygenation, increase mean airway pressure, redistribute gas from less to more compliant alveoli, increase risk for auto-PEEP, decrease peak airway pressure, less well tolerated by patients

Question 27

Know how high flow rate increases tidal volume.

Answer 27

Example: RR = 10, TV = 500 cc, I:E = 1:2 (1/3 of time there’s inspiratory flow delivered) O2 Flow = 10 l/min. Ve = 10 * 500 = 5000 cc , Flow = 10 l/min * 1/3 = 3300cc, Delivered Ve =5000+3300cc=8300cc O2 Flow= 1 l/min Ve = 10 * 500 = 5000 cc , Flow = 1 l/min * 1/3 = 330cc, Delivered Ve =5000+330cc=5300cc

Question 28

What’s CPAP:

Answer 28

Positive pressure delivered throughout the breathing cycle, Decreases the energy to overcome negative airway pressure, Mainly used for stenting the upper airway in non-intubated patients, Used to improve oxygenation during one lung ventilation