NIV Summary

Indications

  • COPD with respiratory distress & hypercapnia
  • Acute cardiogenic pulmonary oedema
  • Patients unsuitable for intubation

Contraindications

  • Need for immediate intubation
  • Severe facial deformity
  • Fixed upper airway obstruction
  • Facial burns

CPAP Settings

  • Start: 5-10 cmH₂O
  • Max: 15 cmH₂O
  • SpO₂ target: 94-98%

BiPAP Settings

  • COPD: IPAP 15-30, EPAP 3-8
  • NMD: IPAP 10, EPAP 3-8
  • SpO₂ target: 88-92%

Red Flags

  • pH < 7.25 on optimal NIV
  • RR persistent > 25
  • New confusion or distress

ICU Referral

  • Impending respiratory arrest
  • NIV failing to reduce PCO₂
  • SpO₂ < 85-88% on NIV

Non-Invasive Ventilation (NIV)

Comprehensive guide to non-invasive ventilation in acute respiratory failure

Introduction

Non-invasive ventilation (NIV) is the umbrella term used to describe the provision of ventilatory support through the patient's upper airway using a mask or similar device. NIV is principally indicated in patients with chronic obstructive pulmonary disease (COPD) with respiratory distress and hypercapnia, and in acute cardiogenic pulmonary oedema.

Important Considerations

NIV may also be used in patients who are not considered suitable for intubation. A ceiling of treatment, and whether escalation to intubation is indicated, must be defined at the outset. Do not use NIV as a substitute for intubation and invasive ventilation if the latter is more appropriate.

Monitoring Requirements

Patients treated with NIV should be managed in an environment with suitable monitoring, including continuous pulse oximetry, access to equipment for blood gas analysis, and immediate availability of resuscitation equipment. Staff should be fully trained and experienced in the use of NIV.

Indications

Indications for NIV in acute hypercapnic respiratory failure (AHRF) as per BTS:

COPD

(if persisting after bronchodilators and controlled oxygen therapy)

  • pH < 7.35
  • PCO₂ > 6.5
  • RR > 23

Neuromuscular Disease (NMD)

  • Respiratory illness with RR > 20 if usual VC < 1L even if PCO₂ < 6.5 OR
  • pH < 7.35 and pCO₂ > 6.5

Contraindications

Primary Contraindication

The most important contraindication to the use of NIV is the need for immediate tracheal intubation and invasive ventilation. NIV is not indicated in asthma/pneumonia. Many of the factors previously considered as contraindications are relative or negated if tracheal intubation is considered inappropriate and NIV is to be used as the ceiling of treatment.

Absolute Contraindications (BTS)

  • Severe facial deformity
  • Fixed obstruction of the upper airway
  • Facial burns

Relative Contraindications (BTS)

  • pH < 7.15
  • pH < 7.25 and additional adverse feature
  • GCS < 8
  • Confusion/agitation
  • Cognitive impairment

Further Relative Contraindications

  • Haemodynamically unstable patient (requiring inotropes/vasopressors, unless in ITU)
  • Significant arrhythmia
  • Untreated pneumothorax
  • Vomiting
  • Marked abdominal distension
  • Copious respiratory secretions

Type of NIV

CPAP (Continuous Positive Airway Pressure)

A constant positive pressure is applied throughout the respiratory cycle

Indications

  • Typically used for type I respiratory failure
  • E.g. acute cardiogenic pulmonary oedema, obstructive sleep apnoea

Procedure

  • Start with a CPAP at 5 - 10 cmH₂O
  • Titrate FiO₂ to achieve SpO₂ of 94 - 98%
  • If initial CPAP does not alleviate hypoxia, increase to maximum of 15 cmH₂O as tolerated
  • If CO₂ level starts to increase consider BiPAP

BiPAP (Bi-level Positive Airway Pressure)

Provides two levels of pressure support throughout the respiratory cycle: IPAP (Inspiratory) > (Expiratory) EPAP

Indications

  • Typically used for type II respiratory failure
  • E.g. COPD, neuromuscular disease

BiPAP Procedure (as per BTS for AHRF)

Pressure Settings

  • Start with initial EPAP 3 (or higher if OSA known/expected)
  • Start with an initial IPAP 15 (20 if pH < 7.25) in COPD
  • Titrate IPAP over 10 - 30 minutes to IPAP 20 -30 to achieve adequate augmentation of chest/abdo movement and slow RR (max IPAP 30 without expert review)
  • Increase EPAP if patient remains hypoxaemic (max EPAP 8 without expert review)
  • Start with an initial IPAP 10 (or 5 above usual setting) in NMD

Backup Rate

Backup rate of 16-20.

I:E Ratio

  • COPD: 1:2 to 1:3
  • NMD: 1:1

Inspiratory Time

  • COPD: 0.8 - 1.2 s
  • NMD: 1.2 - 1.5 s

Oxygenation

Aim for 88-92% in all patients

Monitoring during NIV

Observe the patient closely and assess: chest wall movement, coordination of respiratory effort with the ventilator, accessory muscle recruitment, respiratory rate, heart rate, oxygen saturations, patient comfort and mental state

Monitoring Frequency

  • Clinical observations must be recorded every 15 minutes for the first hour and every 30 minutes during the next 4 hours
  • Measure the arterial blood gas values after 1 hour of NIV therapy and after every subsequent change in settings

Red Flags in Managing AHRF (BTS)

  • pH < 7.25 on optimal NIV
  • RR persistent > 25
  • New onset confusion or patient distress

Actions if Red Flags Identified

  • Check synchronisation, mask fit, exhalation port
  • Give physiotherapy/bronchodilators, consider anxiolytic
  • CONSIDER IMV

Indications for ICU Referral

Indications for ICU Referral in AHRF (BTS)

  • AHRF with impending respiratory arrest
  • NIV failing to augment chest wall movement or reduce PCO₂
  • Inability to maintain SpO₂ > 85-88% on NIV
  • Need for IV sedation or adverse features indicating need for closer monitoring and/or possible difficult intubation

Complications

If patients are selected correctly, the majority of complications are relatively minor. Potential complications include:

Cardiovascular

  • Hypotension (due to increased intrathoracic pressure reducing preload)

Pulmonary

  • Barotrauma (due to gas trapping and overinflation, pneumothorax is a rare complication)

Gastrointestinal

  • Gastric distension
  • Pulmonary aspiration (vomiting or regurgitation into tight-fitting mask)

Local Effects

  • Pressure necrosis of the bridge of the nose
  • Discomfort from a tight-fitting mask
  • Sinus or ear discomfort and nasal mucosal congestion or drying/ulceration