Non-Invasive Ventilation
Mechanical ventilatory support delivered without an ETT, usually via delivery of positive pressure to the airway. Any invasive mode of ventilation can be given non-invasively:
The oldest form of NIV is negative-pressure, and is the iron lung.
- CPAP
Administration of a single pressure throughout the respiratory cycle. - PSV
Administration of pressure that is provided only when inspiratory flow is detected. - Bilevel/Bipap
Combination of CPAP and PSV.
Indications
Acute:
- Reversible respiratory failure
- APO
↓ LV afterload and ↑ recruitment.- CPAP ~10cmH2O ideal in most
- T2RF in COAD
↓ Mortality and need for intubation, and re-intubation when extubated onto CPAP.- CPAP appropriate for reversible obstruction
- Bilevel/PSV (5-20cmH2O) for hypercarbia
- Mask intolerance higher for COAD than APO
- Asthma
- Pneumonia
May be preferred in immunosuppressed patients or other groups with very poor outcomes from mechanical ventilation. - Post-operative
- Chest wall trauma
Chronic:
- APO
- OSA
- Neuromuscular disease
Contraindications
- Obtundation
Risk of aspiration with an unprotected airway. - Dyssynchrony
Patient discomfort or poor mask fit may lead to leaking and failure of pressure to augment appropriately. - Inability to clear secretions
Continuous Positive Airway Pressure
Applies an unchanging positive pressure throughout the respiratory cycle, leading to:
- ↓ Work of breathing
↓ Elastic work by ↑ alveolar recruitment. ↓ Inspiratory threshold work of breathing if iPEEP is ↑. - ↑ SpO2
Via alveolar recruitment. - ↓ LV afterload
Pressure Support Ventilation
Inspiration is detected via a flow or pressure trigger, and a positive airway pressure is provided which:
- ↑ Vt
Leads to ↑ Va and ↓ PaCO2. - ↓ elastic and resistive work of breathing
- Induces pulmonary surfactant release
Anatomy
Equipment
Technique
Complications
- B
- Aspiration
- D
- Discomfort
- Agitation
- E
- Pressure injuries
- G
- Gastric distension