2(b) NIV and Acute Respiratory Failure

Question 1

When might ventilatory support be required?

Answer 1

Respiratory acidosis and hypercapnia

Question 2

What is CPAP?

Answer 2

Delivery of a constant pressure during both inspiration and expiration.

• same level of pressure (above atmospheric pressure)

Question 3

How does CPAP help?

Answer 3

CPAP does NOT actively assist inspiration.
- Provides a distending pressure.

Physiologically:
Increases FRC
Opens collapsed or underventilated alveoli
Increases PaO2
Stabilises up0per airway obstruction
(maintains an open upper airway, especially during sleep
** Positive airway pressure

Question 4

How can CPAP affect cardiac output?

Answer 4

If it delivers too much pressure, can decrease the blood coming back to the heart (low BP)

or can increase cardiac output and help cardiac muscle contraction

Question 5

How does bilevel ventilatory support work? (NIV)

Answer 5

Provides two levels of airway pressure

Actively assists inspiration while providing end expiratory pressure

Physiologically: - CPAP effect + increases TV & MV
Reduces WOB

Question 6

When would CPAP be used?

Answer 6

When oxygenation is the problem or when holding the airways open is the primary goal of therapy

Question 7

When is Bilevel (NIV) indicated?

Answer 7

When CO2 is raised

When pump failure is the problem (recognised by increased CO2)

Question 8

What does Bilevel ventilatory support do during expiration and what is the effect?

Answer 8

EPAP - end positive airway pressure.

Pressure remaining in airway to hold them open: helps if there is airway closure

Question 9

What modes does Bilevel include?

Answer 9

Pt triggered breaths (spontaneous)
Machine triggered breaths ( Timed)
Combined (ST)

Question 10

What is IPAP/pressure supoort in bilevel?

Answer 10

Level of inspiratory assistance

Increases tidal volume

Question 11

What will the pressure support be limited by?

Answer 11

What the patient finds comfortable.
If too fast, patient feels like they’ve been hit in the face with a big gust of wind. If it’s too slow, can feel like they’re suffocating

Question 12

What is the rise time in bilevel?

Answer 12

How rapidly the machine goes from EPAP to IPAP.

Normal in:exp = 1:2

Question 13

What are the goals of using bilevel

Answer 13

To improve gas exchange. Decrease PaCO2 and acidosis
Reduced work of breathing
Prevent the need for invasive ventilatory support
Improve clinical outcomes

Question 14

What is the best evidence for bilevel?

Answer 14

patients with underlying hypoventilation ie raised CO2

Question 15

What sort of patients could have bilevel

Answer 15

Lung disease eg COPD, cystic fibrosis, brochiectasis
Obesity-related hypoventilastion

Neuromusclular disease
Chest wall deformity

Question 16

Benefits of Bilevel over intubation for some patients

Answer 16

Can be used for someone who is startng to struggle > non invasive ventilation > acoid intubation and break that cycle and avoid further respiratory decompensation.

Also for people who need to be ventilated but would not do well in ICU

Patients can be given NIV for palliation, some extra time, make them more comfortable

Question 17

Clinical indications for NIV

Answer 17

pH 45 mmHg
Moderate to severe dyspnoea
High WOB (access mm, increased respiratory rate)
Clinical impression of deterioration

Respiratory acidosis/hypercapnia esp COPD/SDB

Question 18

Clinical indications for NIV and not intubation

Answer 18

Respiratory deterioration but immediate intubation not required
Haemodynamically stable
Single system failure (Reversible diagnosis, cooperative/non combative)
Manageable secretions

Question 19

Who is not suitable for NIV?

Answer 19

Need for immediate intubation - imminent respiratory arrest
Refractory hypoxaemia
GCS <80 mmHg, significant ventricular arrhythmias)
Sepsis
Recent oral, oesophageal or gastric surgery
Facial trauma/burns or surgery
Undrained pneumothorax
Vomiting or bowel obstruction

Question 20

Where is the strongest evidence for the benefit of bilevel ventilation?

Answer 20

In patients with underlying COPD

• Reduces mortality
• Reduces need for intubation

Also some evidence for use in pulmonary oedema

Question 21

Where is there growing use of NIV where there is little evidence to support it

Answer 21

Pneumonia
Asthma
Sepsis
Neurologic
Other

Question 22

What is the outcome when NIV fails

Answer 22

In hospital mortality rate is higher than for patients receiving IMV without prior NIV

Question 23

What is the rate of successful weaning and what does failure after extubation mean?

Answer 23

10-20% of all pts fail first extubation attempt

Extubation failure is assoc with poor outcomes including high mortality rates of 25-50%

Question 24

What are the factors associated with extubation failure?

Answer 24

Age >65 
*Underlying chronic cardioresp disease
Rapid shallow breathing index (F/Vt)
Pneumonia as the cause of intubation
GCS< 8
* Excessive endotracheal secretions
* Weak or absent cough
Increased PaC02 > 45 mmHg or low Pa02/Fi02 during weaning trial

Question 25

What are the goals of IPAP and how is it set/does it work.

Answer 25

Goals:
Improve gas exchange
Reduce work of breathing
Alter breathing pattern

Set to maximum tolerated

Increasing pressure or swing increases tidal volume, alters respiratory rate

Question 26

What are the goals of EPAP

Answer 26

Offset PEEPi
Decrease WOB
Improve V/Q matching
Maintain UA patency

Question 27

What are the complications and side effects of NIV therapy?

Answer 27

Generally few.
Skin breakdown
Eye irritation from leak
Airway drying

Gastric distension
Pulmonary barotrauma
Aspiration pneumonia
Hypotension

Question 28

What is the role of the physio during NIV treatment?

Answer 28

Involved in the NIV team
Secretion clearance in pts on NIV
Mobilisation/early rehab of pts using NIV

Question 29

Results for airway clearance during NIV in AECOPD

Answer 29

ACBT= dec. length of time on NIV
PEP = cleared more secretions and dec. length of weaning
CPT: reduced time on NIV and better gas exchange
Intrapulmonary percussive ventilation + dec. LOS ICU and CO2

Question 30

What is mechanical in-exsufflation - cough assist, how is it applied and how does it work

Answer 30

Mechanically assisted cough technique
Applies positive pressure to the airways, followed by a rapid change to negative pressure.
Increases peak cough flow more than other airway clearance techniques

Applied via mask or trache tube