Asthma Management Handbook

Giving bronchodilator treatment according to severity and age

Recommendations

Give initial salbutamol by inhalation, using doses, routes of administration and dosing schedules according to the patient’s age and the severity of acute asthma.

Table. Rapid primary assessment of acute asthma in adults and children

Mild/Moderate

Severe

Life-threatening

Can walk, speak whole sentences in one breath

(For young children: can move around, speak in phrases)

Oxygen saturation >94%

Any of these findings:

  • Use of accessory muscles of neck or intercostal muscles or 'tracheal tug' during inspiration or subcostal recession ('abdominal breathing')
  • Unable to complete sentences in one breath due to dyspnoea
  • Obvious respiratory distress
  • Oxygen saturation 90–94%

Any of these findings:

  • Reduced consciousness or collapse
  • Exhaustion
  • Cyanosis
  • Oxygen saturation <90%
  • Poor respiratory effort, soft/absent breath sounds

Notes

The severity category may change when more information is available (e.g. pulse oximetry, spirometry) or over time

The presence of pulsus paradoxus (systolic paradox) is not a reliable indicator of the severity of acute asthma.

If oxygen therapy has already been started, it is not necessary to cease oxygen to measure pulse oximetry.

Oxygen saturation levels are a guide only and are not definitive; clinical judgment should be applied.

Definitions of severity classes for acute asthma used in this handbook may differ from those used in published clinical trials and other guidelines that focus on, are or restricted to, the management of acute asthma within emergency departments or acute care facilities.

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Table. Initial bronchodilator treatment in acute asthma (adults and children 6 years and over)

  • Do not use IV short-acting beta2 agonists routinely for initial bronchodilator treatment.

  • Do not give oral salbutamol.

  • Monitor for salbutamol toxicity (e.g. tachycardia, tachypnoea, metabolic acidosis, hypokalaemia) – may occur with inhaled or IV salbutamol.

Mild/Moderate

Severe

Life-threatening

Give salbutamol 4-12 puffs (100 mcg/actuation) via pMDI and spacer

Repeat every 20-30 minutes for the first hour if required (sooner, if needed to relieve breathlessness)

Give salbutamol 12 puffs (100 mcg/actuation) via pMDI and spacer

If patient unable to breathe through a spacer, give 5 mg nebule via nebuliser

Start oxygen therapy if oxygen saturation <95% and titrate to target:

Adults: 92–95%
Children: 95% or higher

Repeat salbutamol as needed. Give at least every 20 minutes for first hour (3 doses)

Give salbutamol 2 x 5 mg nebules via continuous nebulisation driven by oxygen

Maintain oxygen saturations:

Adults: 92% or higher
Children: 95% or higher

Arrange immediate transfer to higher-level care

When dyspnoea improves, consider changing to salbutamol via pMDI plus spacer or intermittent nebuliser (doses as for severe acute asthma)

† Give one puff at a time followed by 4 breaths (See Table. Using pressurised metered-dose inhalers in acute asthma)

‡ See Table. Using nebulisers in acute asthma

Note: To deliver nebulised bronchodilators in a patient receiving oxygen therapy, use an air-driven compressor nebuliser and administer oxygen by nasal cannulae.

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Table. Initial bronchodilator treatment in acute asthma (children 0–5 years)

  • Do not use IV short-acting beta2 agonists routinely for initial bronchodilator treatment.

  • Do not give oral salbutamol.

  • Monitor for salbutamol toxicity (e.g. tachycardia, tachypnoea, metabolic acidosis, hypokalaemia) – may occur with inhaled or IV salbutamol.

  • Closely monitor level of consciousness, fatigue, oxygen saturation, respiratory rate and heart rate. If symptoms do not respond, contact a paediatrician or senior clinician and reconsider the diagnosis. 

  • In children under 12 months old, asthma is less likely to be the cause of wheezing than other conditions (e.g. bronchiolitis, pneumonia).

Mild/Moderate

Severe

Life-threatening

Give salbutamol 2-6 puffs (100 mcg/actuation) via pMDI and spacer plus mask

Repeat every 20-30 minutes for the first hour if needed (sooner, if needed to relieve breathlessness)

Give salbutamol 6 puffs (100 mcg/actuation) via pMDI and spacer plus mask

If patient unable to breathe through a spacer, give 2.5 mg nebule via nebuliser

Start supplementary oxygen if oxygen saturation <95%

Titrate to 95% or higher

Repeat salbutamol as needed. Give at least every 20 minutes for first hour (3 doses)

Give salbutamol 2 x 2.5 mg nebules via continuous nebulisation driven by oxygen

Maintain  oxygen saturation at 95% or higher

Arrange immediate transfer to higher-level care

When dyspnoea improves, consider changing to salbutamol via pMDI plus spacer or intermittent nebuliser (doses as for severe acute asthma)

† Give one puff at a time followed by 4 breaths (See Table. Using pressurised metered-dose inhalers in acute asthma)

‡ See Table. Using nebulisers in acute asthma

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Table. Using pressurised metered-dose inhalers in acute asthma

Administration of salbutamol by health professionals for a patient with acute asthma

  1. Use a salbutamol pressurised metered-dose inhaler (100 mcg/actuation) with a spacer that has already been prepared (see note).
  2. Shake inhaler and insert upright into spacer.
  3. Place mouthpiece between the person’s teeth and ask them to seal lips firmly around mouthpiece.
  4. Fire one puff into the spacer.
  5. Tell person to take 4 breaths in and out of the spacer.
  6. Remove the spacer from mouth. Shake the inhaler after each puff before actuating again. (This can be done without detaching the pressurised metered-dose inhaler from the spacer.)

Notes

The process is repeated until the total dose is given (e.g 12 puffs for an adult, 6 puffs for a child). Different doses are recommended for patients and carers giving asthma first aid in the community.

New plastic spacers should be washed with detergent to remove electrostatic charge (and labelled), so they are ready for use when needed. In an emergency situation, if a pre-treated spacer is not available, prime the spacer before use by firing at least 10 puffs of salbutamol into the spacer. (This is an arbitrary number of actuations in the absence of evidence that would enable a precise guideline.)

Priming or washing spacers to reduce electrostatic charge before using for the first time is only necessary for standard plastic spacers; antistatic polymer spacers (e.g. Able A2A, AeroChamber Plus, Breathe Eazy, La Petit E-Chamber, La Grande E-Chamber, OptiChamber Diamond) and disposable cardboard spacers do not require treatment to reduce electrostatic charge.

For small children who cannot form a tight seal with their lips around the spacer mouthpiece, attach a well-fitted mask to the spacer.

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Table. Using nebulisers in acute asthma

Driving nebuliser

Nebulisers can be driven by air, piped oxygen, or an oxygen cylinder fitted with a high-flow regulator capable of delivering >6 L/min.

Intermittent nebulisation

Use one nebule:

Adults: 5 mg nebule

Children 6 years and over: 5 mg nebule

Children 0–5 years: 2.5 mg nebule

Continuous nebulisation using nebules

Put two nebules into nebuliser chamber at a time and repeat to refill when used up.

Adults: use two 5 mg nebules (10 mg) at a time

Children 6 years and over: use two 5 mg nebules (10 mg) at a time

Children 0–5 years: use two 2.5 mg nebules (5 mg) at a time

  • If using oxygen to drive a nebuliser, do not exceed 8–10 L/minute and avoid over-oxygenation (increases risk of hypercapnoea).
  • The use of nebulisers increases the risk (to staff and patients) of nosocomial aerosol infection. If using a nebuliser, follow your organisation’s infection control protocols to minimise spread of respiratory tract infections.

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How this recommendation was developed

Based on selected evidence

Based on a limited structured literature review or published systematic review, which identified the following relevant evidence:

  • Camargo et al. 20031
  • Cates et al. 20132
  • Chandra et al. 20053
  • Dhuper et al. 20114
  • Direkwatanachai et al. 20115
  • Emerman et al. 19996
  • Fayaz et al. 20097
  • Kaashmiri et al. 20108
  • Karpel et al. 19979
  • Travers et al. 201210
  • Yasmin et al. 201211

For patients with severe acute asthma who are unable to breathe through a spacer, salbutamol can be given by intermittent nebulisation.

Table. Using nebulisers in acute asthma

Driving nebuliser

Nebulisers can be driven by air, piped oxygen, or an oxygen cylinder fitted with a high-flow regulator capable of delivering >6 L/min.

Intermittent nebulisation

Use one nebule:

Adults: 5 mg nebule

Children 6 years and over: 5 mg nebule

Children 0–5 years: 2.5 mg nebule

Continuous nebulisation using nebules

Put two nebules into nebuliser chamber at a time and repeat to refill when used up.

Adults: use two 5 mg nebules (10 mg) at a time

Children 6 years and over: use two 5 mg nebules (10 mg) at a time

Children 0–5 years: use two 2.5 mg nebules (5 mg) at a time

  • If using oxygen to drive a nebuliser, do not exceed 8–10 L/minute and avoid over-oxygenation (increases risk of hypercapnoea).
  • The use of nebulisers increases the risk (to staff and patients) of nosocomial aerosol infection. If using a nebuliser, follow your organisation’s infection control protocols to minimise spread of respiratory tract infections.

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How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to the following source(s):

  • Camargo et al. 20031

For patients with life-threatening asthma, deliver salbutamol via continuous nebulisation driven by oxygen until breathing improves, then consider changing to a pressurised metered-dose inhaler plus spacer or intermittent nebuliser.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to the following source(s):

  • Camargo et al. 20031

If using a nebuliser, follow your organisation’s infection control protocols to minimise spread of respiratory tract infections.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to the following source(s):

  • Hui, 201312

To deliver intermittent nebulised bronchodilators in a patient receiving oxygen therapy, use an air-driven compressor nebuliser and administer oxygen by nasal cannulae. Titrate to oxygen saturation target of 92–95% in adults or at least 95% in children.

If needed, salbutamol can be delivered by piped (‘wall’) oxygen or an oxygen cylinder fitted with a high-flow regulator capable of delivering >6 L/min. The patient should be changed back to their original oxygen mask once nebulisation is complete.

How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • O'Driscoll et al. 200813

To deliver salbutamol in a patient undergoing non-invasive ventilation, either of the following options can be used:

  • Deliver salbutamol by nebuliser via an attachment to the ventilator circuit. For optimal delivery of salbutamol, the nebuliser should be attached with the expiration port between the facemask and nebuliser.
  • Briefly interrupt ventilation to deliver salbutamol via pressurised metered-dose inhaler and spacer.
How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to the following source(s):

  • Calvert et al. 200614

Do not give oral salbutamol.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

Do not use IV short-acting beta2 agonists routinely.

How this recommendation was developed

Based on selected evidence

Based on a limited structured literature review or published systematic review, which identified the following relevant evidence:

  • Travers et al. 201210
  • Travers et al. 201215

More information

Salbutamol in acute asthma: dosing regimens

One placebo-controlled study showed that, for patients who showed clear improvement after the first dose of salbutamol via pressurised metered-dose inhaler and spacer, there was no advantage in repeating the dose more often than every 60 minutes until full recovery (extra doses can be given as needed).9

However, in patients who did not show a clear response to the first salbutamol dose, repeating the dose at intervals of 30 minutes or less was more effective than every 60 minutes.9

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Salbutamol in acute asthma: route of administration

Inhaler plus spacer, or nebuliser

Salbutamol delivered via a pressurised metered-dose inhaler with spacer is at least as effective as salbutamol delivered via nebuliser in patients with moderate-to-severe acute asthma who do not require ventilation.4217 The use of nebulisers increases the risk of transmitting respiratory infections to staff and other patients.

Intravenous salbutamol

Overall, intravenous short-acting beta2 agonists do not appear to be superior to inhaled short-acting beta2 agonist.10

Benefits have not been demonstrated in adults.10 Very limited evidence from one study suggested that the addition of IV salbutamol to inhaled salbutamol reduced recovery time in children with severe acute asthma in the emergency department.10

However, there is a lack of consensus on the appropriate dose of IV salbutamol for children.18 Recommendations differ between guidelines in Australia19 and elsewhere.18 Doses have not been calculated based on age-specific pharmacokinetic and pharmacodynamic data. The doses recommended in guidelines are generally relatively higher than for adults on a micrograms per kilogram body weight basis.

Compared with inhaled salbutamol, intravenous salbutamol is associated with increased risk of adverse effects including tremor and hypokalaemia.1018  Concomitant use of the inhalation and IV routes may increase the risk of salbutamol toxicity.20

Note: Salbutamol concentrate for infusion is available in 5 mL ampoules containing salbutamol sulfate equivalent to 5 mg (1 mg/mL) salbutamol in a sterile isotonic solution (Ventolin obstetric injection). Salbutamol for injection is also available in ampoules of salbutamol sulphate equivalent to 500 mcg salbutamol in 1 mL sterile isotonic solution (Ventolin injection).

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Technical notes: pressurised metered-dose inhalers with spacers

Manufacturers of most delivery devices recommend shaking the device before actuating. The physical characteristics of each formulation, including the effects of shaking, differ widely,21 but for simplicity it is best always to recommend shaking.

Pressurised metered-dose inhalers (except for those that are breath-actuated) can be used with a spacer. When a spacer is used with a pressurised metered-dose inhaler, delivery of the medicine to the patient’s airways is maximised when the patient takes a slow, deep breath from the spacer after each actuation.2223 Multiple actuations of a pressurised metered-dose inhaler into a spacer can reduce the amount of respirable medicine available because aerosol particles can agglomerate into larger particles or become attached to the spacer walls.22

Therefore, the ideal way to deliver inhaled medicines via pressurised metered-dose inhaler and spacer is to shake the device, ask the person to breathe out all the way into the spacer, fire a single actuation into the spacer, and have the person immediately take a slow deep breath from the spacer, then hold their breath for 5 seconds. This process should be repeated until the total intended number of actuations is taken. Patients should be trained to follow these instructions when using their inhalers. Inhaling slowly with a single breath maximises delivery of the medicine to the lungs and minimises deposition in the upper airways when using a manually actuated pressurised metered-dose inhaler with or without a spacer, or when using a breath-actuated pressurised metered-dose inhaler.24 However, slow breathing may not be possible for patients with acute asthma. Tidal breathing through the spacer (e.g. four breaths in and out without removing the spacer) is used in acute asthma and for very young children. First aid instructions should include how to use inhaler and spacer.

In practice, optimal delivery of inhaled medicines involves a balance between maximising the proportion of respirable medicine and maximising efficiency of inhalation by the patient within real-world constraints. The optimal delivery of salbutamol in real-world circumstances is not well defined. For day-to-day use of salbutamol, most adults gain sufficient relief from symptoms when using a pressurised metered-dose inhaler on its own. A spacer may only be needed during a flare-up. By contrast, the use of a spacer is always recommended for inhaled corticosteroids delivered by manually actuated pressurised metered-dose inhalers, to reduce the risk of local adverse effects and increase delivery to the airways.

Many available in vitro studies of aerosol particle deposition in the airways were performed using older CFC-propelled formulations, which are now obsolete. Similar studies have not been performed for current non-CFC pressurised metered-dose inhalers.

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Assessment of oxygen status in acute asthma

Hypoxia is the main cause of death that is due to acute asthma.25

Routine objective assessment of oxygen saturation at initial assessment of acute asthma is needed because clinical signs may not correlate with hypoxaemia.

Pulse oximetry is the internationally accepted method for routine assessment of oxygen status in patients with acute asthma.26

The risk of hypercapnoea increases when oxygen saturation falls below 92%.27

Pulse oximetry does not detect hypercapnoea, so blood gas analysis is necessary if hypercapnoea is suspected in patients with severe or life-threatening acute asthma.

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Oxygen therapy in acute asthma

Oxygen is a treatment for hypoxaemia, not breathlessness. Oxygen has not been shown to improve the sensation of breathlessness in non-hypoxaemic patients.13 When oxygen supplementation is used, pulse oximetry is necessary to monitor oxygen status and titrate to target.

The aim of titrated oxygen therapy in acute care is to achieve normal or near-normal oxygen saturation, except in patients who are at risk of hypercapnoeic respiratory failure,13 such as patients with overlapping asthma and COPD.

Adults

In adults with acute asthma, titrated oxygen therapy using pulse oximetry to maintain oxygen saturation at 93–95% while avoiding hyperoxaemia achieves better physiological outcomes than 100% oxygen at high flow rate (8 L/min).28 High-concentration and high-flow oxygen therapy cause a clinically significant increase in blood CO2 concentration in adults with acute asthma.2829

National guidelines for the management of acute exacerbations of COPD recommend that hypoxic patients should be given controlled oxygen therapy via nasal prongs at 0.5–2.0 L/minute or a venturi mask at 24% or 28%, with target oxygen saturation of over 90% (PaO2 >50 mmHg, or 6.7 kPa).30 Excessive oxygen administration should be avoided because it can worsen hypercapnoea.30

Children

Drying of the upper airway is a potential complication of oxygen therapy in children,3132 which might contribute to bronchoconstriction.32 Humidified oxygen can be considered if necessary. Humidification is usually not needed for low flow oxygen (<4 L/minute in children or 2 L/minute in infants) for short term. Humidification may be considered if the oxygen is required for longer than 48 hours or if the nasal passages are becoming uncomfortable or dry.31

Guidance on oxygen delivery techniques and practical issues is available from  Sydney Children's Hospital Network and The Royal Children's Hospital Melbourne.

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Non-invasive positive pressure ventilation in acute asthma

Efficacy

Few randomised clinical trials have evaluated non-invasive positive pressure ventilation (biphasic positive airway pressure or continuous positive airway pressure) for adults with severe acute asthma.33 This technique has not been shown to reduce risk of death or the need for intubation, but may reduce hospital admissions, length of hospital stay and length of ICU stay.33 It may also improve lung function, but evidence is inconsistent.33

Delivering bronchodilators in patients undergoing noninvasive positive-pressure ventilation

When delivering nebulised salbutamol while using noninvasive positive-pressure ventilation set at pressures commonly used in clinical practice, the amount of salbutamol inhaled is likely to be significantly higher than with a nebuliser alone (based on a bench model of a spontaneously breathing adult). This increase may be because the ventilator tubing acts as a spacer.14

The position of the nebuliser in the ventilator circuit significantly affects the total dose of salbutamol inhaled. Salbutamol is delivered most effectively when the nebuliser is positioned immediately after the expiration port (i.e. starting from the facemask, the expiration port is positioned before the nebuliser).14

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References

  1. Camargo CA, Spooner C, Rowe BH. Continuous versus intermittent beta-agonists for acute asthma. Cochrane Database Syst Rev. 2003; Issue 4: CD001115. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD001115/full
  2. Cates CJ, Welsh EJ, Rowe BH. Holding chambers (spacers) versus nebulisers for beta-agonist treatment of acute asthma. Cochrane Database Syst Rev. 2013; 9: Cd000052. Available from: http://www.ncbi.nlm.nih.gov/pubmed/24037768
  3. Chandra A, Shim C, Cohen HW, et al. Regular vs ad-lib albuterol for patients hospitalized with acute asthma. Chest. 2005; 128: 1115-1120. Available from: http://journal.publications.chestnet.org/article.aspx?articleid=1083722
  4. Dhuper S, Chandra A, Ahmed A, et al. Efficacy and cost comparisons of bronchodilatator administration between metered dose inhalers with disposable spacers and nebulizers for acute asthma treatment. J Emerg Med. 2011; 40: 247-55. Available from: http://www.ncbi.nlm.nih.gov/pubmed/19081697
  5. Direkwatanachai C, Teeratakulpisarn J, Suntornlohanakul S, et al. Comparison of salbutamol efficacy in children–via the metered-dose inhaler (MDI) with Volumatic spacer and via the dry powder inhaler, Easyhaler, with the nebulizer–in mild to moderate asthma exacerbation: a multicenter, randomized study. Asian Pac J Allergy Immunol. 2011; 29: 25-33. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21560485
  6. Emerman CL, Cydulka RK, McFadden ER. Comparison of 2.5 vs 7.5 mg of inhaled albuterol in the treatment of acute asthma. Chest. 1999; 115: 92-96. Available from: http://journal.publications.chestnet.org/article.aspx?articleid=1076742
  7. Fayaz M, Sultan A, Rai ME. Comparison between efficacy of MDI+spacer and nebuliser in the management of acute asthma in children. J Ayub Med Coll Abbottabad. 2009; 21: 32-34. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20364736
  8. Kaashmiri M, Shepard J, Goodman B, et al. Repeat dosing of albuterol via metered-dose inhaler in infants with acute obstructive airway disease: a randomized controlled safety trial. Pediatr Emerg Care. 2010; 26: 197-202. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20179658
  9. Karpel JP, Aldrich TK, Prezant DJ, et al. Emergency treatment of acute asthma with albuterol metered-dose inhaler plus holding chamber: how often should treatments be administered?. Chest. 1997; 112: 348-356. Available from: http://www.ncbi.nlm.nih.gov/pubmed/9266868
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  11. Yasmin S, Mollah AH, Basak R, et al. Efficacy of salbutamol by nebulizer versus metered dose inhaler with home-made non-valved spacer in acute exacerbation of childhood asthma. Mymensingh Med J. 2012; 21: 66-71. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22314457
  12. Hui DS. Severe acute respiratory syndrome (SARS): lessons learnt in Hong Kong. J Thorac Dis. 2013; 5: S122-6. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3747521/
  13. O’Driscoll BR, Howard LS, Davison AG, British Thoracic Society (BTS) Emergency Oxygen Guideline Development Group. BTS guideline for emergency oxygen use in adult patients. Thorax. 2008; 63 (Suppl 6): vi1-vi68. Available from: http://thorax.bmj.com/content/63/Suppl_6/vi1.full
  14. Calvert LD, Jackson JM, White JA, et al. Enhanced delivery of nebulised salbutamol during non-invasive ventilation. J Pharm Pharmacol. 2006; 58: 1553-7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/17132219
  15. Travers AH, Jones AP, Camargo CA, et al. Intravenous beta(2)-agonists versus intravenous aminophylline for acute asthma. Cochrane Database Syst Rev. 2012; 12: CD010256. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD010256/full
  16. Cates CJ, Bestall J, Adams N. Holding chambers versus nebulisers for inhaled steroids in chronic asthma. Cochrane Database Syst Rev. 2006; Issue 1: CD001491. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD001491.pub2/full
  17. Ferguson C, Gidwani S. Delivery of bronchodilators in acute asthma in children. Emerg Med J. 2006; 23: 471-472. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2564350/
  18. Starkey ES, Mulla H, Sammons HM, Pandya HC. Intravenous salbutamol for childhood asthma: evidence-based medicine?. Arch Dis Child. 2014; 99: 873-877. Available from: http://adc.bmj.com/content/99/9/873.abstract
  19. Babl FE, Sheriff N, Borland M, et al. Paediatric acute asthma management in Australia and New Zealand: practice patterns in the context of clinical practice guidelines. Arch Dis Child. 2008; 93: 307-312. Available from: http://adc.bmj.com/content/93/4/307.abstract
  20. Abramson MJ, Bailey MJ, Couper FJ, et al. Are asthma medications and management related to deaths from asthma?. Am J Respir Crit Care Med. 2001; 163: 12-18. Available from: http://www.ncbi.nlm.nih.gov/pubmed/11208619
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  22. Barry PW, O'Callaghan C. Multiple actuations of salbutamol MDI into a spacer device reduce the amount of drug recovered in the respirable range. Eur Respir J. 1994; 7: 1707-1709. Available from: http://www.ncbi.nlm.nih.gov/pubmed/7995401
  23. Rau JL, Restrepo RD, Deshpande V. Inhalation of single vs multiple metered-dose bronchodilator actuations from reservoir devices : An in vitro study. Chest. 1996; 109: 969-974. Available from: http://www.ncbi.nlm.nih.gov/pubmed/8635379
  24. Laube BL, Janssens HM, de Jongh FHC, et al. What the pulmonary specialist should know about the new inhalation therapies. Eur Respir J. 2011; 37: 1308-1417. Available from: http://erj.ersjournals.com/content/37/6/1308.full
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  26. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. GINA, 2012. Available from: http://www.ginasthma.org
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  28. Perrin K, Wijesinghe M, Healy B, et al. Randomised controlled trial of high concentration versus titrated oxygen therapy in severe exacerbations of asthma. Thorax. 2011; 66: 937-41. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21597111
  29. Rodrigo GJ, Rodriquez Verde M, Peregalli V, Rodrigo C. Effects of short-term 28% and 100% oxygen on PaCO2 and peak expiratory flow rate in acute asthma: a randomized trial. Chest. 2003; 124: 1312-7. Available from: http://journal.publications.chestnet.org/article.aspx?articleid=1081910
  30. Abramson MJ, Crockett AJ, Dabscheck E, et al. The COPD-X Plan: Australian and New Zealand guidelines for the management of chronic obstructive pulmonary disease. Version 2.34. The Australian Lung Foundation and The Thoracic Society of Australia and New Zealand, 2012. Available from: http://www.copdx.org.au/
  31. Sydney Children's Hospital. Oxygen therapy and delivery devices – SCH. Practice guideline. Guideline No: 0/C/13:7019-01:00. Sydney Children's Hospital Westmead, Sydney, 2013. Available from: http://www.chw.edu.au/about/policies/alphabetical.htm
  32. The Royal Children's Hospital of Melbourne, Oxygen Delivery. Clinical Guidelines (Nursing), The Royal Children's Hospital 2013. Available from: http://www.rch.org.au/rchcpg/hospitalclinicalguidelineindex/Oxygendelivery/
  33. Lim WJ, Mohammed Akram R, Carson KV, et al. Non-invasive positive pressure ventilation for treatment of respiratory failure due to severe acute exacerbations of asthma. Cochrane Database Syst Rev. 2012; 12: CD004360. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD004360.pub4/full