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  4. Non-invasive Positive Pressure Ventilation

UNCONTROLLED WHEN PRINTED
Indications
  • NIV (non-invasive ventilation) is used to support patients in acute respiratory distress who require respiratory support. It has been evidenced to reduce the need for intubation and reduces the risk for ventilator associated pneumonia.
  • Defined as ventilatory support without an invasive (endotracheal) airway.
  • May be used pre-RSI, to assist with preoxygenation needs where appropriate.
Contraindications
  • Respiratory or cardiac arrest
  • Patients unable to maintain their own airway or clear secretions
  • Haemodynamic instability
  • Arrhythmic instability
  • Base of skull fracture
  • Severe encephalopathy
  • Facial trauma or deformity
  • Upper airway obstruction
  • Untreated pneumothorax
  • Severe upper GI bleed
  • High Aspiration Risk
Patient Factors & Considerations
  • Life threatening hypoxaemia (<90% SpO2 on non rebreather mask) – don't delay RSI if required.
  • Level of consciousness.
  • Heat moisture exchangers (HMEs) are not recommended for NIV. They have been noted to cause increased dead space, increasing resistance and the patient’s work of breathing and therefore their compliance to the treatment. Moreover, the additional resistance can cause mask leaks
Procedure

Preparation

  • Perform primary and secondary survey
  • Perform 12-lead ECG
  • Establish vascular access; obtain pre-hospital blood sample
  • Consider ondansetron or metoclopramide
  • Monitor patient continuously, recording full observations
  • Use iSTAT CG8+ cartridge to determine pH, PCO2 BE to titrate therapy. Initial gas prior to commencing therapy, and subsequent at 45-60 minutes
  • Reassure and explain the process to patient, a key step to tolerance of the mask

Procedure

  • Position the patient to ensure maximal chest wall movement and to prevent airway obstruction
  • Size mask and ensure well fitting for patient comfort and successful application
  • Set up ventilator, using the following principles:
    • Set FiO2 at 1 then titrate down, as appropriate, during management
    • Start at low pressures and slowly increase pressures by 2-3cmH2O every 5 minutes as required (to a maximum of 20cm H2O)
    • For CPAP:
      • Start at 5cmH2O
      • Increase inspiratory pressures in increments of 2-3cmH2O
    • For BiPAP
      • Start with 10/5 cmH2O
      • Increase inspiratory pressures in increments of 2cm H2O and simultaneously increase the expiratory pressures by increments of 1cmH2O
  • Apply NIV

Note:

  • Pinsp on the Hamilton ventilator is Psupport
  • This is the difference between EPAP (PEEP on the Hamilton) and IPAP.
  • e.g. If you have set PEEP at 5cm H2O and want to set up a BiPAP of 10/5, then you set Pinsp at 5cmH2O (Pinsp = IPAP - EPAP).
Hamilton Ventilator BiPAP setup (cmH2O)
BiPAP10/512/614/716/818/920/10
PEEP5678910
Pinsp5678910
Success
  • Treatment aim is to achieve tidal pressures equivalent to 6-8ml/kg (ideal body weight)
  • Optimal NIV is the lowest pressures and FiO2 required to achieve SpO2 of 90%
Discontinue
  • Discontinue if patient deteriorates, and consider need for RSI
  • Discontinue if patient too anxious and intolerant of mask
  • Discontinue if promotes gastric emptying in patient
Additional Information

Potential complications / side-effects:

  • Claustrophobia
  • Haemodynamic instability
  • Gastric filling and aspiration
  • Raised ICP

Non-invasive Ventilation

The physiological benefits of NIV are similar to those of ventilator support 

  • Provides augmentation of alveolar ventilation to reverse respiratory acidosis and hypercarbia
  • Provides alveolar recruitment and increased FiO2 to reverse hypoxia
  • Offers reduction of work of breathing to reduce or prevent respiratory muscle insufficiency

Continuous Positive Airway Pressure (CPAP)

CPAP is a form of respiratory support that provides constant pressure throughout the respiratory cycle. CPAP principally addresses acute cardiac pulmonary oedema and salt water aspiration through the following measures. The positive airway pressure provided:

  • Reduces the work of breathing by increasing alveolar recruitment and increasing tidal volumes, improving oxygen saturations
  • Reduces threshold load created in the presence of positive end expiratory pressure
  • Reduction of LV afterload

Bi-level Positive Airway Pressure (BiPAP)

BiPAP allows separate settings for inspiratory (IPAP) and expiratory (EPAP) airway pressure levels. This allows incremental times for augmentation of tidal volume and minute volume reducing PaCO2. Those in type II respiratory failure benefit the most from BiPAP. i.e. COPD; neuromuscular disease.

  • The amount of pressure support (difference between inspiratory and expiratory pressures) reduces CO2 retention and decreases PaCO2
  • Increasing IPAP reduces work of breathing and improves tidal volumes
  • Increasing EPAP assists in recruiting alveoli and improves oxygen saturations
References
References
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