Ventilation

Question 1

All ventilators need to provide adequate gas exchange to patients.

What are the 4 basic settings used to do this?

Answer 1

1) Respiratory rate

2) Tidal volume i.e. the amount of air that moves in or out of the lungs with each respiratory cycle

3) FiO2 (fraction of inspired O2)

4) PEEP

Question 2

What is PEEP?

Answer 2

Peak end expiratory pressure

This helps to maintain alveolar recruitment & stops them collapsing at the end of respiration –> keeps lungs open and allows more gas exchange to take place.

Question 3

What 2 settings on mechanical ventilation aid CO2 removal?

Answer 3

1) RR
2) Tidal volume

Increasing these will INCREASE CO2 removal

Question 4

What 2 settings on mechanical ventilation aid O2 delivery?

Answer 4

1) FiO2

2) PEEP

Increasing these will INCREASE CO2 delivery

Question 5

What are the 2 ways that a ventilator can provide a tidal volume to a patient?

Answer 5

1) Pressure control

2) Volume control

Question 6

What is the ‘pressure control’ method of ventilation?

Answer 6

The ventilator provides a flow of gases to the lung until a SET PRESSURE is reached.

This is primarily used when the patient has no spontaneous breathing but will support the patient if they are able to trigger a breath.

I.e. the ventilator delivers a breath to a set pressure, and at a set rate.

Question 7

What is the ‘volume control’ method of ventilation?

Answer 7

In volume control mode a preset tidal volume is delivered at a set rate.

The ventilator provides a flow of gases to the lung until a SET VOLUME is reached.

Question 8

Describe the invasive ventilation journey for a patient

Answer 8

1) Mandatory ventilation

2) Intermittent mandatory ventilation

3) Spontanoeus ventilation with pressure support

4) Spontaneous ventilation

Question 9

What happens in mandatory ventilation?

Answer 9

The patient makes no effort to breathe and ventilator is set to a mandatory ventilation mode.

Ventilator provides tidal volumes to patient in a very set and mandatory way.

Question 10

What happens in intermittent mandatory ventilation?

Answer 10

The patient is able to take some spontaneous breaths, this triggers the ventilator.

The ventilar recognsies the patient is trying to take a breath and provides the patient with some pressure support for that breath.

When the patient is no longer able to take spontanoeus breaths, the ventilator will provide the patient with a mandatory breath.

Question 11

What happens in sponeantous ventilation with pressure support?

Answer 11

The patient’s condition continues to improve and they are able to take all their spontaneous breaths.

The patient triggers the ventilator with their effort to breathe, the ventilator recognises this and provides them with some pressure support.

As the patient’s breathing gets stronger, this pressure support is gradually reduced until they are able to breathe spontaneously without any support for their breathing.

Question 12

In order to ensure that patients are not distressed or uncomfortable by having an endotracheal tube or being on a ventilator, what it is necessary to administer?

Answer 12

Sedation & analgesia to the patient as an infusion

Question 13

What is usually used for sedation & analgesia for patients on a ventilator/ET tube?

Answer 13

Propofol + short acting opioid (e.g. alfentanil)

Question 14

What are some side effects of using propofol & opioids in ventilation/ET tube?

Answer 14

Hypotension, bradycardia, constipation, hallucinations, nausea, delirium.

Question 15

What are some iatrogenic complications of mechanical ventilation?

Answer 15

1) Volutrauma - lungs expanded too much, can cause pneumothorax or increasing inflammation

2) Barotrauma - lungs exposed to too high pressure, can cause pneumothorax or damage to alveoli

3) Ventilator assocatied pneumonia (VAP)

4) Vocal cord trauma

5) Tracheal stenosis

6) Haemodynamic instability (from drugs)

7) Delirium (from drugs)

Question 16

What leads to VAP?

Answer 16

Cilia action in bronchioles that normally remove secretions from lungs don’t work as effectively –> higher risk of infections.

Question 17

Most common organisms causing VAP? (4)

Answer 17

1) S. aureus (including MRSA)

2) P. aeruginosa

3) Klebsiella

4) Enterobacter species

Question 18

What are the 4 key indications for BiPAP?

Answer 18

1) COPD with respiratory acidosis; pH 7.25-7.35 (despite max optimal medical mx)

2) Type 2 respiratory failure 2ary to chest wall deformity, neuromuscular disease, or obstructive sleep apnoea

3) Cardiogenic pulmonary oedema unresponsive to CPAP

4) Weaning from tracheal intubation

Question 19

When should BiPAP be considered in patients with acute exacerbation of COPD?

Answer 19

Respiratory acidosis (PaCO2 >6kPa, pH <7.35) despite immediate maximum standard medical treatment.

Question 20

When would you consider intubation or admission to HDU in patients with acute exacerbation of COPD?

Answer 20

pH <7.25 (despite trying BiPAP)

Question 21

In patients with severe acute respiratory distress syndrome (ARDS) who are receiving mechanical ventilation, what positioning may be helpful?

Answer 21

Prone positioning

Question 22

How does prone positioning help in ARDS?

Answer 22

1) Prompts more uniform lung inflation, which in turn helps to alleviate atelectasis (collapse of lung tissue) and prevent over-distention of the lung.

2) Reduces the ventilation-perfusion mismatch by improving blood flow to well-ventilated areas of the lung –> better gas exchange.

3) Can help recruit alveoli, further enhancing oxygenation and potentially reducing lung injury.

Question 23

Assessment for long term O2 therapy in COPD is done by measuring ABG results.

How many ABGs are required?

Answer 23

Assessment is done by measuring ABGs on TWO occasions at least THREE weeks apart, in patients with stable COPD on optimal management.

Question 24

How many ABGs are required in the assessment of LTOT requirement in patients with COPD?

How far apart must they be taken?

Answer 24

2

Must be taken 3 weeks apart

Question 25

Who should LTOT be offered to in COPD?

Answer 25

Patients must have stable COPD on optimal management.

Offer LTOT to patients:

1) pO2 <7.3 kPa

or

2) pO2 7.3-8kPa AND one of the following:
a) 2ary polycythaemia
b) peripheral oedema
c) pulmonary HTN

Question 26

What is lowest flow rate (L/min) of oxygen that is recommended through a nasal cannulae as emergency oxygen therapy?

Answer 26

1L/min

Question 27

What is the highest flow rate (L/min) of oxygen that is recommended through nasal cannulae as emergency oxygen therapy?

Answer 27

6L/min

Question 28

What is the lowest flow rate (L/min) of oxygen that is recommended through a simple face mask as emergency oxygen therapy?

Answer 28

5L/min

Question 29

What is the highest flow rate (L/min) of oxygen that is recommended through a simple face mask as emergency oxygen therapy?

Answer 29

10L/min

Question 30

A 33 year old woman arrived in the ED in status epilepticus. Her seizure has been terminated with 4mg of intravenous lorazepam. She is now snoring and gurgling despite having a nasopharyngeal airway. Observations show: Temperature 36.9℃, P 90 bpm regular, BP 110/65mmHg, RR 10, SpO2 90% on 15L/min via a NRBM. Her GCS is (3)E1 V1 M1.

Which airway device is most appropriate to initially manage this patient’s airway at this time?

Answer 30

Oropharyngeal airway

Further airway support is required due to signs of respiratory compromise. The anticipated course is that after this short period of sedation (benzos to terminate her seizure), this patient’s GCS will improve –> OPA most appropriate given situation).

Question 31

An unidentified man has arrived in the ED. He is unconscious, with a GCS of (5) E1V1M3. Observations show: Temperature 36.9℃, P 90 bpm regular, BP 150/80mmHg, RR 12, SpO2 97% on 15L/min via a NRBM. There is some snoring but no gurgling or stridor. He has a scalp laceration on the right side of his head, his pupils are: (R) 5mm - (L) 2mm +

Which airway device is most appropriate to initially manage this patient’s airway at this time?

Answer 31

ET tube

The likelihood is that this is a serious head injury given the clinical findings. The anticipated clinical course is that this patient needs an urgent CT and then, depending upon the findings, he may need to go to theatre or neurointensive care. The safest decision is to intubate prior to going for the scan. This will secure his airway.

Question 32

An unidentified man has arrived in the ED. He is in cardiac arrest having collapsed in the street. He is currently being ventilated using a bag-valve-mask and an his airway is supported by an oropharyngeal airway. During the initial assessment, the FY2 who is trying to ventilate the patient, reports that they are struggling to get adequate chest expansion despite repositioning manoeuvres.

Which airway device is most appropriate to initially manage this patient’s airway at this time?

Answer 32

ET tube or supraglottic device (LMA or iGel) - depends on competency of practitioner