Non-invasive ventilation (NIV) and asthma

OVERVIEW

Non-invasive ventilation (NIV) is widely used for severe asthma in Australasia yet remains a controversial topic

USES

  • improve rate of recovery and limit drug side effects (e.g. salbutamol, aminophyline)
  • to avoid intubation (improved gas exchange and avoidance of fatigue)
  • pre-oxygenation and ventilatory support while preparing for intubation — can use with ketamine as part of a delayed sequence intubation (DSI) approach
  • part of a post-extubation strategy to prevent reintubation

RATIONALE

Mechanical ventilation in asthma is difficult and has significant risks:

  • dynamic hyperinflation
  • ventilator dyssynchrony
  • risk of barotrauma
  • often requires neuromuscular blockers together with corticosteroids resulting in high risk of ICU-acquired weakness, and is associated with increased length of stay and mortality

NIV has numerous possible advantages (see below)

PROS AND CONS

Advantages

  • decreased work of breathing on inspiration
    • occurs if external PEEP is set to match iPEEP in a spontaneously breathing patient
    • PEEPi would otherwise need to be overcome by increased negative pleural pressure to initiate inspiration in a in a spontaneously breathing patient
  • less fatigue
  • improved V/Q mismatch and gas exchange
  • decreased dead space
  • prevent atelectasis and maximise recruitment
  • direct bronchodilation (PPV leads to increased FEV1 and PEFR in some studies)

Disadvantages

  • dynamic hyperinflation if external PEPP > intrinsic PEEP
  • increased risk of barotrauma
  • incorrect patient selection may lead to delayed intubation (risk complications)
  • usual risks of NIV

EVIDENCE

There is a lack of high-level evidence to guide practice

  • no large well-designed RCTs
  • A 2012 Cochrane Review found 5 trials with 206 patients but was inconclusive
  • some support in observational studies, case series, and small trials

PATIENT SELECTION

Consider NIV if intubation is not imminently required and any of the following are present:

  • Tachypnea RR >25/min
  • Tachycardia 110/min
  • Use of accessory muscles of respiration
  • Hypoxia with a PF ratio <200
  • Hypercapnia with PaCO2 <60 mmHg
  • FEV1 <50% predicted

In general, avoid NIV if:

  • decreased level of consciousness
  • agitated
  • vomiting
  • profuse secretions
  • significant haemodynamic instability

SETTINGS

Typical initial BiPAP settings:

  • PEEP at 3-5 cmH20 (low)
  • iPAP at 7-15 cmH20, adjust to target RR <25/min
  • high inspiratory flow rate, low I:E ratio (e.g. 1:5) and prolonged expiratory time

AN APPROACH

Use non-invasive ventilation in severe asthma

  • unless contra-indicated
  • as part of a multi-modal approach including maximal pharmacological therapy
  • as long as it does not delay intubation when indicated

Monitor these patients carefully, treat aggressively and be prepared to intubated if they deteriorate

References and Links

LITFL

Journal articles

  • Agarwal R, Malhotra P, Gupta D. Failure of NIV in acute asthma: case report and a word of caution. Emerg Med J. 2006 Feb;23(2):e9. [pubmed] [article]
  • Gupta D, Nath A, Agarwal R, Behera D. A prospective randomized controlled trial on the efficacy of noninvasive ventilation in severe acute asthma. Respir Care. 2010;55(5):536-43. [pubmed] [article]
  • Landry A, Foran M, Koyfman A. Does Noninvasive Positive-Pressure Ventilation Improve Outcomes in Severe Asthma Exacerbations? Ann Emerg Med 2013;62(6):594-596 [pubmed]
  • Lim WJ, Mohammed Akram R, Carson KV, Mysore S, Labiszewski NA, Wedzicha JA, Rowe BH, Smith BJ. Non-invasive positive pressure ventilation for treatment of respiratory failure due to severe acute exacerbations of asthma. Cochrane Database Syst Rev. 2012 Dec 12;12:CD004360. [pubmed] [article]
  • Murase K, Tomii K, Chin K, Niimi A, Ishihara K, Mishima M. Non-invasive ventilation in severe asthma attack, its possibilities and problems. Panminerva Med. 2011 Jun;53(2):87-96. [pubmed] [article]
  • Soroksky A, Klinowski E, Ilgyev E, Mizrachi A, Miller A, Ben Yehuda TM, Shpirer I, Leonov Y. Noninvasive positive pressure ventilation in acute asthmatic attack. Eur Respir Rev. 2010 Mar;19(115):39-45. doi: 10.1183/09059180.00006109. Review. [pubmed] [article]
  • Stefan MS, Nathanson BH, Lagu T, et al. Outcomes of Noninvasive and Invasive Ventilation in Patients Hospitalized with Asthma Exacerbation. Ann Am Thorac Soc. 2016;13(7):1096-104. [pubmed] [article]
  • Stefan MS, Nathanson BH, Priya A, et al. Hospitals’ Patterns of Use of Noninvasive Ventilation in Patients With Asthma Exacerbation. Chest. 2016;149(3):729-36. [pubmed] [article]

CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health, a Clinical Adjunct Associate Professor at Monash University, and the Chair of the Australian and New Zealand Intensive Care Society (ANZICS) Education Committee. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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