Non-Invasive Ventilation (NIV)

OVERVIEW

• Non-invasive ventilation (NIV) is the application of respiratory support via a sealed face-mask, nasal mask, mouthpiece, full face visor or helmet without the need for intubation
• In the modern era it implies the application of positive airway pressure, however some classifications include the application of a negative-pressure generator to the chest (‘iron lung’) as NIV
• Positive pressure ventilatory support may be with CPAP or bi-level modes and delivered by a range of ventilators from specifically designed devices to full-service ICU ventilators
• NIV decreases resource utilisation compared with invasive ventilation and avoids the associated complications.
• Patient selection and a well-designed clinical protocol are important to avoid delaying intubation in patients who are not suitable for and/or failing NIV

CLASSIFICATION

Negative pressure (cyclical)

• iron lung chest box
• used for COPD, neuromuscular disease

Positive pressure (non-cyclical)

• continusous positive airway pressure (CPAP)
• used for acute pulmonary edema, asthma, obstructive sleep apnoea (OSA)

Positive pressure (cyclical)

• Bilevel positive airway pressure (BIPAP), inspiratory positive airway pressure (IPAP), pressure support ventilation (PSV) and positive pressure ventilation (PPV)
• used for COPD, weaning, asthma, neuromuscular disease

Positive and negative pressure (cyclical)

• cough assist
• used for neuromuscular disease

PHYSIOLOGY

NIV can reverse many of the physiological and mechanical derangements associated with respiratory failure:

• augmentation of alveolar ventilation, helps reverse acidosis and hypercapnoea
• alveolar recruitment and increased FiO2, helps reverse hypoxia
• reduction in work of breathing and respiratory effort/ fatigue
• stabilisation of chest wall in the presence of chest trauma/surgery
• reduction in left ventricular afterload, improves LV function
• counterbalances the respiratory workload and/or reduces respiratory muscle effort, helps maintain alveolar ventilation and prevents exhaustion

INDICATIONS

Primarily for hypercapnea

• acute exacerbation of COPD – decrease work of breathing and unload respiratory muscles
• post extubation acute respiratory failure — planned strategy in selected patients
• Obstructive sleep apnoea / Obesity hypoventilation syndrome
• cystic fibrosis — e.g. bridge to transplant
• patients awaiting lung transplantation
• acute asthma (see Non-Invasive Ventilation and Asthma)

Primarily for hypoxaemia

• cardiogenic pulmonary oedema – alveolar recruitment, decreased afterload, decreased work of breathing
• post operative respiratory failure – in selected patients
• post-traumatic respiratory failure — rib fractures
• respiratory failure in AIDS and other immunosuppressed states
• patient not candidates for intubation/ treatment limitation orders who may qualify for HDU admission or admission to respiratory care units
• Pre-oxygenation prior to intubation

In reality, NIV is often used for a combination (to varying extents) of hypoxaemia, hypercapnia and respiratory weakness regardless of the underlying diagnosis

PREDICTORS OF SUCCESSFUL USE

• Younger age
• Unimpaired conscious state
• Moderate rather than severe hypercarbia
• Rapid improvement in physiological parameters

CONTRAINDICATIONS

• Cardiac / respiratory arrest
• Inability to protect airway – poor cough, excessive/ inability to clear secretions, decreased conscious state/ coma
• upper airway obstruction
• untreated pneumothorax
• marked haemodynamic instability (e.g. shock, ventricular dysrhythmias, severe acute myocardial ischaemia GI bleeding)
• Following upper GI surgery (some debate about this)
• Maxillofacial surgery
• base of skull fracture (risk of pneumocephalus)
• patient refusal
• staff inexperience
• Intractable vomiting

USE OF NIV

Starting NIV

• patient reassurance
• well fitted mask with straps (nasal, full face or helmet)
• set appropriate FiO2
• time or flow cycled
• start at low pressures e.g. 10/5 cmH2O or CPAP 5 cmH20
• increase pressures by 2-3 cmH20 every 5 minutes until satisfactory response (up to 15-17 max)
• reassess after 60 minutes plus ABG

Weaning NIV

• typical approach is trial periods off NIV during the day (e.g. 1 hour off and 2 hours) with overnight rest on NIV
• if patient condition markedly improves NIV can be stopped abruptly
• monitor closely for respiratory fatigue or deterioration

The use of NIV for preventing post-extubation respiratory failure is discussed in the CC entry titled Non-Invasive Ventilation for Weaning.

COMPLICATIONS

• pressure ulcers/necrosis (nasal bridge)
• facial or ocular abrasions
• claustrophobia/anxiety
• agitation
• air swallowing with gastric/ abdominal distension, potentially leading to vomiting and aspiration
• hypotension if hypovolaemic
• aspiration
• oronasal mucosal dryness
• raised ICP
• increased intraocular pressure
• impaired communication
• impaired nutrition

EVIDENCE

Summary of evidence for the use of NIV:

• APO – studies show decreased intubation rate and faster time to resolution of respiratory failure and reduction in mortality and hospital length of stay
• COPD – RCTs and Cochrane review (14 RCTs) showed significant improvement in intubation rates, complications, length of hospital stay and mortality rates for NIV compared with invasive ventilation
• Immunocompromised – – 2 studies, one looking at solid organ transplant recipients and one looking at patients with haematological malignancy showed benefit with NIV, i.e. fewer intubations, complications and reduced ICU and hospital mortality
• Asthma – probably beneficial but limited evidence
• Rib fractures – fewer episodes of pneumonia but no mortality benefit and limited evidence

Summary of evidence against the use of NIV:

• Use as rescue strategy for failed extubation – delays time to re-intubation. May be of benefit as part of weaning strategy and planned intervention post extubation especially in COPD patients
• ARDS – not recommended as first line therapy

Cardiogenic Pulmonary Oedema

• improves respiratory function using above mechanisms
• also allows for redistribution of extravascular lung water back into interstitial space through recruitment and surfactant production
• e.g. CPAP at ~ 10cmH2O
• BIPAP increased risk of MI in one study, but not born out
• over 20 RCTs show improvements in:

-> respiratory failure -> need to intubate -> hospital LOS -> survival -> duration of respiratory support (MV vs NIV)

Chronic Obstructive Pulmonary Disease

• often respond to both CPAP but also need BIPAP
• over 14 RCTs show improvements in:

-> hypercapnic respiratory failure -> intubation rates -> hospital mortality -> nosocomial pneumonia

Asthma

• CPAP 5cmH2O and BiLevel

-> significant increase in FEV1 -> significant decrease in hospital admission rates

ALI and ARDS

• little supportive evidence for NIV

-> high failure rates

Pneumonia and the Immunocompromised

• MV is associated with high morbidity and mortality in these patients
• thus may benefit from a reduction in intubation and MV

Post-operative and Post-traumatic Acute Respiratory Failure

• CPAP improves oxygenation and respiratory rate in general surgical and cardiothoracic patients with mild hypoxaemia.
• outcome data is less clear

NIV-assisted Weaning

• COPD patients respond well if used as a prophylactic measure, can be used for rescue but must not delay intubation if indicated
• not so clear cut for other patients

Sleep Apnoea Syndromes

• CPAP can reverse the chronic changes associated with chronic hypoxia
• if there is a central component, BiLevel or controlled ventilation can be used until can be weaned to CPAP

Chronic Hypoventilation Syndromes

• neuromuscular disease
• no real benefit in stable COPD

Blunt chest injury

• beneficial for prevention of respiratory failure, evidence unclear for rescue

AN APPROACH

• Role of NIV in the critically ill includes APO and respiratory failure in COPD and immunosuppressed patients
• Use NIV as a planned strategy post-extubation in selected patients and as ventilatory support for patients with respiratory failure and treatment directives limiting care
• Avoid the use of NIV to delay or withhold intubation in those who need it

References and Links

Journal articles

• Duggal A, Perez P, Golan E, Tremblay L, Sinuff T. The safety and efficacy of noninvasive ventilation in patients with blunt chest trauma: a systematic review. Crit Care. 2013 Jul 22;17(4):R142. [Epub ahead of print] PubMed PMID: 23876230.
• Esquinas Rodriguez AM, Scala R, Soroksky A, BaHammam A, de Klerk A, Valipour A, Chiumello D, Martin C, Holland AE. Clinical review: humidifiers during non-invasive ventilation–key topics and practical implications. Crit Care. 2012 Feb 8;16(1):203. doi: 10.1186/cc10534. Review. PubMed PMID: 22316078; PubMed Central PMCID: PMC3396215.
• Garpestad E, Brennan J, Hill NS. Noninvasive ventilation for critical care. Chest. 2007 Aug;132(2):711-20. Review. PubMed PMID: 17699147. [Free Full Text]
• Keenan, S. et.al. (2011). Clinical practice guidelines for the use of noninvasive positive-pressure ventilation and noninvasive continuous positive airway pressure in the acute care setting. Canadian Medical Association Journal. PMID: 21324867
• McNeill GBS, Glossop AJ. Clinical applications of non-invasive ventilation in critical care Contin Educ Anaesth Crit Care Pain (2012) 12 (1): 33-37. doi: 10.1093/bjaceaccp/mkr047 [Free Full Text]
• Nava S, Hill N. Non-invasive ventilation in acute respiratory failure. Lancet. 2009 Jul 18;374(9685):250-9. doi: 10.1016/S0140-6736(09)60496-7. Review. PubMed PMID: 19616722.
• Nava S, Navalesi P, Carlucci A. Non-invasive ventilation. Minerva Anestesiol. 2009 Jan-Feb;75(1-2):31-6. Epub 2008 Apr 19. Review. PubMed PMID: 18421257.
• Ram FS, Picot J, Lightowler J, Wedzicha JA. Non-invasive positive pressure ventilation for treatment of respiratory failure due to exacerbations of chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2004;(3):CD004104. Review. PubMed PMID: 15266518.
• Vital FM, Ladeira MT, Atallah AN. Non-invasive positive pressure ventilation (CPAP or bilevel NPPV) for cardiogenic pulmonary oedema. Cochrane Database Syst Rev. 2013 May 31;5:CD005351. doi: 10.1002/14651858.CD005351.pub3. PubMed PMID: 23728654.

FOAM and web resources

• DrGDH — Non Invasive Ventilation
• DrGDH — Noninvasive Ventilation in COPD
• DrGDH — More Non-Invasive Ventilation
• DrGDH — NIV in asthma? No point right?
• DrGDH — NIV in pneumonia. Is consolidation on CXR really a contraindication?
• DrGDH — NIV in cardiogenic pulmonary oedema
• EMCrit Podcast 19 – Non-Invasive Ventilation
• empem.org — Breathing part 4 – What is the role of NIV in the Paediatric Emergency Department?
• Resus.ME — Prehospital NIV
• UMEM Education Pearls — Non-invasive Ventilation (NIV): What’s the Evidence?