Ventilation and Ventilators in Veterinary Anesthesia

Question 1

What is ventilation?

Answer 1

Movement of gas between the lungs and atmosphere

Question 2

What is ventilation defined by?

Answer 2

PaCo2, not PaO2

Question 3

What is hyperventilation?

Answer 3

Decreased PaCO2

Question 4

What is hypoventilation?

Answer 4

Increased PaCO2

Question 5

What is apnea?

Answer 5

Absence of ventilation

Question 6

How do you calculate minute ventilation?

Answer 6

Tidal volume x RR

Question 7

What is spontaneous ventilation?

Answer 7

Patient controls their own ventilation

Question 8

True or False: Most anesthetic drugs will depress ventilation

Answer 8

True

Question 9

If a patient is under anesthesia with 100% O2 but is only taking 2 breaths per minute, what will happen to PO2 and PCO2

Answer 9

PO2 could be normal, but it will not allow for normal minute volume and the PaCO2 will be up and the patient will be hypoventilating

Question 10

What is the effect on the depth of inhalant anesthesia if a patient is hypoventilating?

Answer 10

Less inhalant is reaching the lungs and therefore the brain

Question 11

What is assisted ventilation?

Answer 11

Periodic ventillatory support (assisted breaths at variable rate –> patient respiratory initiate efforts)

Question 12

What is controlled ventilation?

Answer 12

Complete control of patient’s ventillation

Question 13

How can you control ventilation?

Answer 13

Reservoir bag
Demand valve
Automatic ventilator

Question 14

What is peak inspiratory pressure?

Answer 14

The peak pressure reached during the ventilatory cycle (20 cmH2O SA, 20-60 LA)

Question 15

What is positive end-expiratory pressure?

Answer 15

Pressure in the system is always positive (never returns to zero –> ventilators with ascending bellow always have a PEEP of 2 cmH2O)

Question 16

What is inspiratory:expiratory ratio?

Answer 16

The ratio of time: inspiratory and expiratory phases –> usually set to 1:2, as normal ventilation has an expiratory pause

Question 17

What are indications for controlled ventilation?

Answer 17

Hypoventilation (PaCO2 >55 mmHg)
Intra-thoracic surgery
CNS disease
Large animal anesthesia
Patients who have received neuromuscular blocking agents
Control depth of inhalant anesthesia

Question 18

What are the components of an anesthesia ventilator?

Answer 18

Power source
Major control variable
Drive mechanism
Cycling mechanism
Bellows configuration

Question 19

What is required to power the ventilator?

Answer 19

Electricity and/or compressed gas (usually both)

Question 20

What is the major control variable?

Answer 20

Determines the patient’s delivered tidal volume

Question 21

What is a volume-controlled ventilator?

Answer 21

Most anesthesia ventilators

Means that there is a set tidal volume and that is what is administered

Question 22

What is a pressure-controlled ventilator?

Answer 22

Means that you set a certain pressure and tidal volume is adjusted to reach this airway pressure

Question 23

What is the drive mechanism?

Answer 23

This is how a breath is delivered to the patient

Question 24

What is a pneumatically-driven bellow?

Answer 24

Dual-circuit ventilator

Means you have separate driving gas chamber and then the patient circuit

Question 25

What is an electronically-drive piston ventilator?

Answer 25

Single-circuit ventilator | Only one gas circuit, which is the patient circuit

Question 26

What is the cycling mechanism?

Answer 26

This is what determines how the ventilator cycles from inspiration to expiration and back again

Question 27

What is the cycling mechanism of most ventilators?

Answer 27

Time-cycled

Question 28

What are the options for bellows configurations?

Answer 28

Ascending | Descending

Question 29

How do you set up a ventilator?

Answer 29

Turn tidal volume all the way down (to ensure no surprise large breaths) Connect hose to where reservoir bag attaches Close APL valve (pop-off valve) Attach scavenge to ventilator Turn on ventilator, set respiratory rate, and slowly increase to the desired tidal volume and PIP

Question 30

What does capnography do?

Answer 30

Uses end-tidal CO2 to estimate PaCO2

Question 31

What is normal ETCO2?

Answer 31

35-45 mmHg

Question 32

What are the 2 main types of capnometers?

Answer 32

Mainstream | Sidestream

Question 33

What is a mainstream capnometer?

Answer 33

ETCO2 is analyzed at the site of the capnometer placement

Question 34

What is a sidestream capnometer?

Answer 34

A sample of the expired gas is diverted to a measuring site within the monitor

Question 35

What is the adjustment of the ventilator based on?

Answer 35

Patient's ETCO2

Question 36

What patient factors must be considered when adjusting the ventilator?

Answer 36

``` Type of procedure (open thorax or not) Pulmonary disease Pleural or pericardial disease CNS disease Compliance and PIP ```

Question 37

What are physiolocal effects of IPPV?

Answer 37

Possible volutrauma and/or barotrauma Decreased compliance over time Decreased venous return and therefore decreased BP