Mechanical Ventilation Flashcards Preview

Anesthesiology > Mechanical Ventilation > Flashcards

Flashcards in Mechanical Ventilation Deck (61):
1

How does anesthesia affect ventilation?

1. Alters CO2 sensitivity
2. Relaxes respiratory muscles
3. Develops atelectasis
4. Worsens V/Q match issues

2

How can ventilation affect anesthesia?

1. Uptake depends on ventilation
2. Controlled ventilation facilitates reliable uptake and smooth plane of anesthesia

3

What is ventilation defined by?

PaCO2

Patient should have normal resp rate, rhythm and effort

4

What is oxygenation?

Process of oxygenation of arterial blood

Defined by PaO2

5

What is oxygenation monitored by?

Arterial blood gas or pulse oximetry

6

What does oxygenation depend on?

Inspired O2%

100% O2 typically insures good oxygenation

7

What are the two phases of respiration?

Inspiration and expiration

8

What does resistance do?

Limits flow

9

What does compliance do?

Limits volume

10

Indications for mechanical ventilation?

1. Need to decrease PaCO2
2. Need to increase PaO2
3. Need to decrease respiratory effort (mostly ICU)

11

Indication for mechanical ventilation during anesthesia

1. Control of respiratory function
2. Prolonged anesthesia
3. Maintain stable anesthesia plane
4. Neuromuscular blockade
5. Thoracic surgery, chest wall, hernia
6. Obesity, increased abdomen pressure
7. head down positioning
8. Laparoscopy
9. Control ICP

12

Side effects of MV

1. Impairs venous return and cardiac output
2. May cause hypotension especially in hypovolemic patients
3. Pneumothorax and lung injury

13

Direct effects of hypercapnia

1. Peripheral vasodilation
2. Decreased myocardial contractility
3. Bradycardia and possible arrest
4. Increased ICP

14

Indirect effects of hypercapnia

1. Tachycardia, arrhythmias
2. Increased myocardial contractility
3. Increased blood pressure

15

CO2 narcosis levels

>95 mmHg progressive narcosis
>245 mmHg complete narcosis

16

What may happen if not ventilating properly?

CO2 accumulation, hypoxemia, sudden death

17

Should horses be ventilated?

Debated issue

18

Types of ventilation

Spontaneous- patient breathing
Assisted- patient timed, machine assists
Mandatory/Controlled- ventilator controls
Manual- bag
Mechanical- machine driven

19

Ventilation modes

Volume controlled
Pressure controlled

20

What can result from volume ventilation?

Pneumothorax if compliance is decreased

21

Which ventilation mode is preferred if lung volume changes during a procedure?

Pressure controlled

22

Which ventilation mode is preferred if trans-pulmonary pressure changes during a procedure?

Volume controlled

23

Which ventilation mode works well for all patient sizes?

Pressure controlled

24

Classification of ventilators

1. Source of driving power
2. Control variable
3. Cycle variable
4. Trigger variable
5. Limit variable

25

Source of driving power

1. Electronically driven
2. Pneumatically driven (pressurized gas)

26

Which source of driving power is more common?

Pneumatically driven

27

Control variables

1. Flow- delivers constant flow
2. Pressure- delivers constant patient

28

Cycle variables

Triggers expiration when a set value is reached

1. Volume
2. Pressure
3. Time
4. Flow- diminishing flow

29

What is flow variable useful for?

Pressure support ventilation- helps accommodate the patients breathing pattern

30

Trigger variable

Triggers inspiration when a set value is reached

1. Pressure- negative pressure
2. Flow- inpiratory flow

31

Trigger variables are used during what ventilation modes?

Assisted

32

Limit Variable

When value is reached, inspiration will be terminated

1. Volume limit
2. Pressure limit

33

What does a pressure limit prevent?

Barotrauma if ventilator is set inappropriately

34

How can volume controlled ventilation be achieved?

Flow controlled, time cycled ventilator
OR
Flow controlled, volume limited, time cycled ventilator

35

How can pressure controlled ventilation be achieved?

-Pressure controlled, time cycled ventilator
- Pressure controlled, pressure cycled ventilator
- Flow controlled, pressure cycled ventilator

36

I:E Ratio

Ratio of inspiratory/expiratory times

37

What does the I:E ratio define?

Tidal volume (Vt)

38

Does the RR affect inspiratory time and Vt?

Nope

39

PIP

Peak inspiratory pressure- inflates alveoli

40

PEEP

Positive end expiratory pressure- keeps alveoli open

41

Indications for PEEP

1. Open thorax
2. Lung parenchymal disease
3. Following alveolar recruitment maneuver

42

Should PEEP be used during routine anesthesia?

Benefits are questionable

43

IMV

Intermittent mandatory ventilation- allowed to breath freely between mechanical breaths

44

SIMV

Synchronized IMV- each spontaneous breath is assisted

45

PSV

Pressure Support Ventilation- patient is breathing freely but supported with pressure

Flow termination, better synchrony than SIMV

46

CPAP

Continuous Positive Airway Pressure- assisted ventilation mode when both insp/exp pressures are positive

47

Ventilating healthy lung values

Tidal volume : 10-15mL/kg
RR: 10-15 bpm
Inspiratory time: 1-2sec
PIP: 10-20 cmH2O
PEEP: 0-2 cmH2O

48

Ventilating sick lungs

Tidal volume : 4-8mL/kg
RR: up to 60 bpm
Inspiratory time: may be increased but watch expiration
PIP: 35-60max cmH2O
PEEP as needed: 5-20 cmH2O

49

Which lung typically collapses during anesthetic procedures?

The most dependent one very rapidly after induction

50

Can a collapsed lung persist for hours/days after surgery?

Yes

51

What is cyclic recruitment?

Opening and collapse of alveoli with each breath, may lead to lung injury

52

Mechanisms of atelectasis formation

1. Compression
2. Absorption
3. Lack of surfactant

53

Alveolar recruitment maneuver (ARM)

Therapeutic maneuver aiming to open lung atelectasis and improve oxygenation

54

Types of ARM

CPAP and Cycling

Should be followed by PEEP

55

Open Lung concept

Therapeutic approach aiming to reverse atelectasis, prevent cyclic recruitment, and ventilator inducted lung injury

ARM followed by optimal PEEP

56

Clinical application of ARM

Safe airway pressures are highly individual variation

Should only be performed if you have sufficient monitoring/equipment and clinical indication

57

Patient-ventilator asynchrony

Patient attempts to breath out of phase with the ventilator

58

Common causes of patient-ventilator asynchrony

Inadequate anesthetic depth
Inadequate lung volume or tidal volume

ICU: pneumothroax, atelectasis, hypotension, hyperthermia

59

Treatment for patient-ventilator asynchrony

Treat underlying cause; may cause rapid deterioration of oxygenation and ventilation

60

Weaning from ventilator after surgery

If a normal healthy animal it's simple

Decrease ventilator setting or continue ventilating until fully awake

May use opioid antagonists if necessary

61

Weaning from ventilator in the ICU

More difficult since lungs are probably not healthy

Spontaneous ventilation trials may be used