Ventilators

Question 1

Pleateau pressures should generally be kept below ___

Answer 1

Pleateau pressures should generally be kept below 30 mmHg

To limit barotrauma

Question 2

Anyone being mechanically ventilated should have ___ to prevent aspiration and VAP

Answer 2

Anyone being mechanically ventilated should have the head of the bed elevated to at least 45 degrees to prevent aspiration and VAP

Question 3

Atrophy of the diaphragm may occur in ___ if a patient is not actively participating in ventilation

Answer 3

Atrophy of the diaphragm may occur in 2 weeks or less if a patient is not actively participating in ventilation

Question 4

Most patients will be started on ___ for mechanical ventilation

Answer 4

Most patients will be started on assist control mode for mechanical ventilation

AC mode entails: Fixed tidal volume either at set intervals or whenever the patient initiates a breath. Volume will always be the same irrespective of pressures required to achieve it.

You will want to wean patients off of this mode onto pressure support as soon as feasible to maintain the patient’s respiratory control and respiratory muscle strength.

Question 5

Best initial settings for a patient requiring AC mechanical ventilation

Answer 5

6 mL/kg TV

Pleateau pressure < 30 cm H2O

PEEP of 5 cm H2O

FiO2 100%

Acceptable RR

Question 6

IV lidocaine prior to intubation

Answer 6

May decrease risk of cardiac arrhythmia and reduce the bronchospasm induced by ETT insertion into the trachea.

Question 7

MV-associated anxiety

Answer 7

Best way to minimize this is with a mode that utilizes patient-initiated breaths

Question 8

Synchronized intermittent mandatory ventilation (SIMV)

Answer 8

Delivers a mandatory number of breaths with a set volume while at the same time allowing spontaneous breaths.

Associated with improved synchronization between the patient’s natural breathing pattern and the MV. So, it may be a good weaning mode (AC -> SIMV -> Pressure support)

Question 9

When is extubation considered successful?

Answer 9

When reintubation is not required within the next 48 hours

Question 10

Who gets daily CXRs for ventilator positioning and complications?

Answer 10

Everyone on MV who is in the acute phase of disease

Once they are relatively stabilized, you no longer need to check unless there is a specific concern

Question 11

Recommended placement of the EET with respect to the carina

Answer 11

3-4 cm above the carina

To avoid descending into a mainstem bronchus with chin motion

Question 12

Volume vs time for different modes of mechanical ventilation:

• Controlled ventilation
• Assist-controlled ventilation
• Synchronous intermittent mandatory ventilation
• Pressure support ventilation + SIMV
• High frequency positive pressure ventilation
• Volume diffusive respirator

Answer 12

Question 13

Risks of auto-PEEP

Answer 13

Auto-PEEP is notorious for causing hypotension and hemodynamic instability if unmonitored

Ensuring that the patient has adequate circulating volume helps to prevent these complications by reducing the compressibility of small pulmonary vessels.

Question 14

What is auto-PEEP?

Answer 14

Auto-PEEP is the result of ventilator tachypnea with breath-stacking due to insufficient exhalatory time

Lengthening the expiratory time will decrease auto-PEEP, but may also result in aoveolar de-recruitment

Question 15

With SIMV, at least ___ should always be applied

Answer 15

With SIMV, at least 5 cm H2O of PEEP should always be applied

This helps prevent alveolar derecruitment on irregular breathing

Question 16

Difference between PCV and PSV modes

Answer 16

With PCV, there is a minimum preset pressure that MUST be achieved with every patient-initiated breath

PCV will only activate if the patient’s own pressure is insufficient to reach this goal

Question 17

PSV and PCV are best used when. . .

Answer 17

. . . there is concern for barotrauma and low airway pressures are required

As in patients with pneumothorax

Question 18

Jet ventilation

Answer 18

Rarely used in clinical practice

Bronchopleural fistula is the main situation where it may be required, typically in neonates.

High frequency (RR 180-600), low volume ventilation. Patient must be paralyzed for this type of ventilation.

Question 19

Volumetric diffusive respiration

Answer 19

High frequency ventilation, “percussive” ventilation

Helps clear the airways of secretions.

Indications include cystic fibrosis and smoke inhalation injury, both due to copious secretions.

Question 20

“Ventilator bundle”

Answer 20

• Head elevation at 45 degrees
• Sedation with daily sedative interruption
• DVT prophylaxis (pneumoboots, SQH)
• GI prophylaxis (famotidine or PPI)
• Daily spontaneous breathing trial

Question 21

When using an ETT, aerosolized medications. . .

Answer 21

. . . must have their dosage doubled

Since you lose a lot of medication in the tubing

Question 22

AC ventilation mode is likely to result in atypical __ values

Answer 22

AC ventilation mode is likely to result in atypical pCO2 values

This is because AC does not take into account the patient’s own regulation of respiratory drive, frequently resulting in hypocapnia or, less likely, hypercapnia.

For this reason, PS-SIMV is superior if a patient has low pCO2.

Question 23

How do you want to ventilate a patient with ARDS?

Answer 23

Low volume ventilation with PEEP

This minimizes barotrauma while recruiting alveoli for gas exchange.

Question 24

Do you need neuromuscular blockade on a ventilated patient?

Answer 24

No! Only for intubation, if even that.

It should be avoided since it is associated with long-term neurologic side effects.

Question 25

Unnecessary changing of or finagling with the tubing of the ventilator. . .

Answer 25

. . . increases the risk of VAP

Question 26

Artificial noses

Answer 26

Basically internal humidifiers that are part of the ventilator

These redue the risk of waterborne respiratory infections when compared with external in-line humidifiers.

Question 27

Steps of the ventilator weaning process

Answer 27

1. Treatment of acute respiratory failure
2. Clinical judgement that weaning may be possible based on clinical status
   
   • Usually PaO2 < 60 mmHg, FiO2 < 60%, RR < 25
3. Assessment of the readiness to wean
   
   • RSBI index: RR / TV_Liters < 105
4. Spontaneous breathing trial while on sedation vacation
5. Extubation (may use BiPAP bridge)
6. Possible reintubation

Question 28

Optimal nutrition for a patient on a ventilator

Answer 28

Avoidance of carbohydrates is optimal, as they increase the respiratory coefficient and will produce extra CO2 requiring additional ventilation.

Fatty acids are preferred for their increased energy density and reduced CO2 production.

Question 29

A negative inspiratory force greater than ___ is predictive of successful weaning from mechanical ventilation.

Answer 29

A negative inspiratory force greater than -25 cm H2O is predictive of successful weaning from mechanical ventilation.

Question 30

Utilizing a tracheostomy in ventilation

Answer 30

Very useful for weaning difficult patients. A tracheostomy tube is usually far less irritating to the patient than an ETT, and the reduced need for sedation facilitates weaning.

Also provides a secure airway, minimizing the work of breathing and minimizing the risk of VAP.

Question 31

Simplest and most effective way to wean patients from mechanical ventilation

Answer 31

Pressure support ventilation (with gradually decreasing support as tolerated)

Question 32

Cardiopulmonary stress of extubation

Answer 32

When a patient is no longer being mechanically ventilated, their respiratory effort and myocardial oxygen demand increase in order to take over the work of ventilation

This cardiac stress may produce hypotension and hemodynamic instability in critically ill patients.

The solution is to avoid reintubating unless absolutely necessary and instead provide external noninvasive ventilatory support.

Question 33

Parameters you are looking for to gauge that a patient is ready for extubation

Answer 33

RSBI ( RR / V_{T, Liters} ) < 105

Inspiratory force > 25 cm H2O