Ventilation

Question 1

NIV definition and types

Answer 1

includes the use of continuous positive airway pressure (CPAP) and bi-level pressure support ventilation.

NIV - delivers positive pressure throughout.

CPAP blows constant pressure during expiration - main goal is to minimise alveolar collapse as well as during expiration.
reduces preload in systole and afterload in diastole.
- mainly for APO
- PEEP = pressure applied

BiPAP - 2 sets of pressure: high pressure during inspiration and low pressure during expiration. Setting increased tidal volume, helps with hypercapnic respiratory failure.

• useful for COPD, asthma, neuromuscular disease
• EPAP (expired positive airway pressure) - PEEP
• IPAP (inspired positive airway pressure) - combination of PEEP and pressure support

Question 2

How does ventilation function from a physiological perspective?

Answer 2

Positive pressure = alveolar requirement/less collapse increasing compliance + more interface for FiO2

increased compliance = reduced work of breathing

more alveolar opening = more gas exchange (V/Q matching)

Question 3

What are the indications for HFNP/NIV

Answer 3

increased WOB 
dyspneoa 
tachypneoa 
hypercapnic respiratory acidosis 
Hypoxaemia 

Acute HFNP= extubattion, hypoxaemic resp failure, hypercapnoeic resp failure, need for humidification (long term O2/secretions)

Acute CPAP = APO
Acute for BiPAP = COPD or neuromuscular disease with resp acidosis. or asthmatics

limit to ward with 40% and 40L flow.

Question 4

What are some CI to NIV?

Answer 4

inability to maintain patent airway?
- coma
- cardiac arrest
- respiratory arrest
Relative contraindication
- CNS or upper airway condition (potential inability to protect airway)
- High asp risk (GI bleed, ileus post surg)
- inability to have tight mask (facial fractures/facial surgery)

Question 5

What are some settings for NIV?

Answer 5

CPAP - 10cmH2O appropriate for most patients
BiPAP - EPAP 5-8, IPAP 10-15/ Adjust amount of pressure based on tidal volume
Aim 6-8mls/kg IBW
FiO2 - start at 1.0 and wean to target spO2

Question 6

Can you get pulmonary oedema despite normal ejection fraction?

Answer 6

chronic HTN and diastolic dysfunction - heart failure with preserved ejection fraction. Exacerbated by AF, fever, pain, sinus tachy

Question 7

What is a pre-intubation checklist?

Answer 7

• history of intubation with mouth opening <3cm, mallampati score 3 or 4, immobilised neck

Position - sniffing or flat 
Monitoring - ECG, BP (invasive or noninvasive), pulse oximeter with QRS tone switched off 
Equipment 
- suction 
- BMV tested
- nasal prongs 
- ETT opened and cuff checked 
- guidel, bougie
- laryngoscope

preoxygenate for >2mins with tight fitting mask

Drugs - allergies/CI to suxamethonium? (K>5mmol, prolonged immobilisation, neurological disease)

• drugs and doses communicated with team
• metaraminol

Task allocation - PPE
airway team
anaesthesia
difficult airway algorithm

Question 8

What are some standard precautions in intubated patients?

Answer 8

• pantoprazole 40mg IV (PUD prophylaxis)
• enoxaparin 40mg subcut
• chlorhex mouthwash
• daily reduction in sedation
• daily paralysis wean
• head of bed >30degrees (prevent VAP)

Question 9

What are the ventilation settings for general patients? how about in ARDS?

Answer 9

ARDS (Berlin) defintion:

• bilateral CXR infiltrates
• origin of oedema and resp failure not explained by cardiac failure
• PaO2/FiO2 ratio with PEEP >5cmH20 (mild/mod/severe)
• within 1 week of clinical insult

Parameters
VT

Question 10

What is failed extubation? What are the consequences?

Answer 10

re-intubation 48-72hrs after planned extubation 
- increased morbidity and mortality 
- increased pneumonia 
- increased length of stay 
- death 
%

Question 11

Determining timing of extubation - what are the steps in assessment?

Answer 11

1. Disease resolution
   A/B - adequate oxygenation, PaO2 >60, FiO2 <40-50, PEEP 5-10 CXR stable
   C - low vasopressor requirement, stable rhythm, SBP >90, MAP >60
   D - adequate mentation, rousable, no significant weakness (can lift head off pillow, raise arms for 15sec)
   E- no acidosis, no electrolyte abnormality
   F - adequate fluid status
2. Spontaneous breathing
   - wean screen
   - T peice trial (ETT tube breathing off ventilator) or on ventilator but with minimal supports
   30-120mins is predictor of successful extubation
   PEEP 5-10, PS <10, fiO2 <0.5
3. Trial of extubation
   - rousable
   - follow commands
   - minimal secretions
   - intact gag/cough reflex
   - cuff leak test (laryngeal oedema)
4. Post extubation care
   - positioning
   - suction
   - oxygen
   - monitoring - for stridor/laryngospasm

Question 12

What are the steps in extubation?

Answer 12

1. ETT and oral cavity suctioned
2. Deep breath then exhale and at the same time deflate the cuff with ETT removed
3. Suction oral cavity again
4. Apply supplemental O2