Asthma Management Handbook

Assessing response to treatment

Recommendations

Assess clinical response after each dose of bronchodilator:

  • If dyspnoea/increased work of breathing is partially relieved within first 5 minutes, reassess at 15 minutes.
  • If dyspnoea/increased work of breathing is not relieved, repeat bronchodilator dose and consider add-on options.
  • If condition deteriorates at any time, consider add-on treatment options.
  • Reduced wheezing alone is an unreliable indicator of improvement, as it may indicate deterioration

Table. Add-on treatment options for acute asthma Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/61

How this recommendation was developed

Consensus

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

Last reviewed version 2.0

Review treatment response again 10–20 minutes after third dose (approximately 1 hour after first dose).

If respiratory distress or increased work of breathing persists, continue giving salbutamol every 20 minutes and consider add‑on treatment options.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion after literature review yielded insufficient evidence for an evidence-based recommendation

Key evidence considered:

  • Karpel et al (1997)1

Last reviewed version 2.0

Perform blood gas analysis in adults with features of life-threatening acute asthma (any of):

  • unable to speak due to dyspnoea
  • reduced consciousness or collapse
  • exhaustion
  • cyanosis
  • SpO2 <92%
  • poor respiratory effort
  • cardiac arrhythmia.
How this recommendation was developed

Adapted from existing guidance

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

  • Beasley et al. 20152

Last reviewed version 2.0

Monitor for signs of salbutamol toxicity (e.g. (e.g. worsening tachycardia, metabolic acidosis, hypokalaemia).

If toxicity is detected or suspected, consider alternative bronchodilators and start supportive treatment to reduce reliance on salbutamol and to minimise adverse effects. Correct hypokalaemia as required.

  • Salbutamol may occur with inhaled or IV salbutamol
How this recommendation was developed

Evidence-based recommendation

Based on literature search and formulated by multidisciplinary working group

Key evidence considered:

  • Travers et al. 20013
  • Travers et al. 20124
  • Travers et al. 20125
  • Cates et al. 20136
  • Castro-Rodriguez et al. 20157
  • Australian Medicines Handbook 20188

Last reviewed version 2.0

Perform spirometry and record FEV1 when feasible during the acute episode.

Note: Do not attempt spirometry in young children. Most children aged 6 and over can perform spirometry reliably.

  • Patients with severe acute asthma are unlikely to be able to perform spirometry
  • Do not continue attempting to obtain a spirometry reading if the patient is distressed

Table. Tips for performing spirometry in patients with acute asthma

  • Ask the patient to sit straight upright, either in a chair or on a stretcher with their legs over the side.
  • Make sure the person forms a tight seal around the mouthpiece.
  • Tell the patient to take as deep a breath as possible, then blast out air as fast and hard as they can, then keep blowing until asked to stop. Aim for exhalation of maximal force for at least 2 seconds (6 seconds if FVC is measured).

You may need to give the patient lots of coaching, repeat instructions, and give immediate feedback on technique.

Last reviewed version 2.0

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How this recommendation was developed

Consensus

Based on clinical experience and expert opinion after literature review yielded insufficient evidence for an evidence-based recommendation

Key evidence considered:

  • Tan et al. 20149
  • Schneider et al. 201410
  • Wilson et al. 200311
  • Arnold et al. 201312
  • Arnold et al. 201213

Last reviewed version 2.0

In adults, consider admitting patient to hospital if (any of):

  • hypoxia at presentation
  • FEV1 <60% predicted (or 50% of usual, if known) at 1-hour check
  • respiratory distress/increased work of breathing unresolved or unable to lie flat without dyspnoea 1–2 hours after presentation
  • a history of ICU admission for asthma
  • presentation for acute asthma within the past 4 weeks
  • frequent presentations for acute asthma (e.g. several over previous year)
  • high recent use of beta2 agonists
  • patient cannot be monitored adequately at home or cannot easily return to hospital if needed
  • other risk factors for adverse outcomes.

Table. Risk factors for adverse asthma outcomes in adults and adolescents Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/40

How this recommendation was developed

Consensus

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

  • Wilson et al. 200311
  • Aldington & Beasley. 200714

Last reviewed version 2.0

In children, consider admitting patient to hospital if (any of):

  • hypoxia at presentation
  • respiratory distress/increased work of breathing unresolved 1–2 hours after presentation
  • a history of ICU admission for asthma
  • presentation for acute asthma within the past 4 weeks
  • frequent presentations for acute asthma (e.g. several over previous year)
  • high recent use of beta2 agonists
  • patient cannot be monitored adequately at home or cannot easily return to hospital if needed
  • confirmed food allergy
  • other risk factors for adverse outcomes.

Table. Risk factors for life-threatening asthma flare-ups in children

Asthma-related factors

Poor asthma control

Admission to hospital in preceding 12 months

History of intubation for acute asthma

Over-use of short-acting beta2 agonist reliever

Abnormal spirometry findings

Reversible expiratory airflow limitation on spirometry despite treatment

Poor adherence to preventer

Incorrect inhaler technique for preventer

Poor adherence to asthma action plan

Exposure to clinically relevant allergens

Exposure to tobacco smoke

Other clinical factors

Allergies to foods, insects, medicines

Obesity

Family-related factors

Frequent failure to attend consultations/lack of follow-up after an acute flare-up

Significant parental psychological or socioeconomic problems

Parent/carer unequipped to manage asthma emergency

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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 named source(s):

  • Burks et al. 201215

Last reviewed version 2.0

More information

Assessment of oxygen status in acute asthma

Hypoxia is the main cause of deaths due to acute asthma.16

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. It should be available in all situations in which oxygen is used.2

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. Thoracic Society of Australia and New Zealand clinical practice guidelines for acute oxygen use in adults2 recommend that arterial blood gas analysis should be considered if oxygen saturation falls below 92% and in those at risk of hypercapnoea. Venous blood gas analysis can be used to assess acid–base balance and lactate,2 but performs poorly in identifying hypercapnoea.17

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Spirometry in acute asthma

Spirometry is used alongside clinical assessment and oximetry to assess severity of acute asthma and response to treatment. Clinical assessment alone may underestimate the severity of airflow limitation.11

However, no recent clinical trials have compared outcomes of spirometry-guided treatment of acute asthma with non-spirometry-guided treatment.

A study in adults with acute asthma found that, on its own, FEV1 (measured by spirometry) at 1 hour after admission to the emergency department did not closely correlate with clinicians’ decision for or against hospital admission, as assessed clinically.11 However, the combination at 1 hour of FEV1 and the patient’s ability to lie flat was significantly predictive of the decision for hospital admission.11

In adults with poor response to initial bronchodilator treatment, dyspnoea scores at 3 hours from presentation may predict relapse or clinicians’ assessment of the need for hospitalisation better than FEV1, but neither is a strong predictor.10

In children with acute asthma, clinical severity scores may be more sensitive than spirometry to detect change clinical status beyond the first 2 hours of treatment.12 The value of performing spirometry in children before hospital discharge is unclear.9

Feasibility and technique

Although some clinical guidelines recommend spirometry before treatment to assess baseline lung function, most children with severe acute asthma and many with mild-to-moderate acute asthma cannot perform spirometry at this time.13 Younger children (most children under 6 years) are unlikely to be able to perform spirometry, even when they do not have a flare-up.

Most adults with acute asthma can perform spirometry within the first hour of admission to the emergency department.18 (Hospital staff and primary care health professionals may need specific training in spirometry technique to be able to obtain acceptable spirometry in patients with acute asthma.18)

It may not be feasible to apply standard spirometry technique and manoeuvre acceptability criteria in patients with acute asthma:13, 18

  • 80% of patients older than 12 years with acute asthma can perform an FEV1 manoeuvre. A forced exhalation from total lung capacity for 2 seconds is sufficient and provides useful information about the severity of airflow obstruction
  • two attempts may suffice if patients are unable to make three attempts
  • variability between manoeuvres of < 10% should be considered acceptable
  • patients may not be able to tolerate nose clips
  • patients are unlikely to be able to exhale for long enough to demonstrate the time-volume plateau. Although patients should aim for forced exhalation of at least 6 seconds, 2 seconds is acceptable for measuring FEV1 in clinical assessment during acute asthma. A spirometry manoeuvre might be considered acceptable if back-extrapolated volume is either < 5% of FVC or 0.15 L (whichever is greater), or a time to peak flow < 120 ms.

Table. Tips for performing spirometry in patients with acute asthma

  • Ask the patient to sit straight upright, either in a chair or on a stretcher with their legs over the side.
  • Make sure the person forms a tight seal around the mouthpiece.
  • Tell the patient to take as deep a breath as possible, then blast out air as fast and hard as they can, then keep blowing until asked to stop. Aim for exhalation of maximal force for at least 2 seconds (6 seconds if FVC is measured).

You may need to give the patient lots of coaching, repeat instructions, and give immediate feedback on technique.

Last reviewed version 2.0

Asset ID: 66

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Last reviewed version 2.0

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Peak expiratory flow measurement in acute asthma

Peak expiratory flow rate obtained using a peak flow meter underestimates the severity of airflow limitation in patients with acute asthma, compared with FEV1 obtained by spirometry.19

Peak expiratory flow is not a sensitive measure of small clinical improvements as perceived by the patient.20

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References

  1. 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
  2. Beasley R, Chien J, Douglas J et al. Thoracic Society of Australia and New Zealand oxygen guidelines for acute oxygen use in adults: ‘Swimming between the flags". Respirology. 2015; 20: 1182–91. Available from: https://www.ncbi.nlm.nih.gov/pubmed/26486092/
  3. Travers, A A, Jones, A P, Kelly, K D, et al. Intravenous beta2-agonists for acute asthma in the emergency department. Cochrane Database Syst Rev. 2001; Issue 1: CD002988. Available from: http://cochranelibrary-wiley.com/doi/10.1002/14651858.CD002988/full
  4. Travers AH, Jones AP, Camargo CA et al. Intravenous beta2-agonists versus intravenous aminophylline for acute asthma. Cochrane Database Syst Rev 2012; Issue 12: CD010256. Available from:https://www.ncbi.nlm.nih.gov/pubmed/23235686/
  5. Travers, A H, Milan, S J, Jones, A P, et al. Addition of intravenous beta. Cochrane Database Syst Rev. 2012; Issue 12: CD010179. Available from: http://cochranelibrary-wiley.com/doi/10.1002/14651858.CD010179/full
  6. 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
  7. Castro-Rodriguez, J. A., Rodrigo, G. J., Rodriguez-Martinez, C. E.. Principal findings of systematic reviews for chronic treatment in childhood asthma. J Asthma. 2015; 52: 1038-45. Available from: https://www.ncbi.nlm.nih.gov/pubmed/26303207
  8. Australian Medicines Handbook. Last modified July 2018: Australian Medicines Handbook Pty Ltd. 2018
  9. Tan CC, McDowell KM, Fenchel M et al. Spirometry use in children hospitalized with asthma. Pediatr Pulmonol 2014; 49: 451-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24000189/
  10. Schneider JE, Lewis LM, Ferguson I et al. Repeated dyspnea score and percent FEV1 are modest predictors of hospitalization/relapse in patients with acute asthma exacerbation. Respir Med 2014; 108: 1284-91. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25087835/
  11. Wilson MM, Irwin RS, Connolly AE, et al. A prospective evaluation of the 1-hour decision point for admission versus discharge in acute asthma. J Intensive Care Med. 2003; 18: 275-285. Available from: http://www.ncbi.nlm.nih.gov/pubmed/15035763
  12. Arnold DH, Gebretsadik T, Hartert TV. Spirometry and PRAM severity score changes during pediatric acute asthma exacerbation treatment in a pediatric emergency department. J Asthma 2013; 50: 204-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/23259729/
  13. Arnold DH, Gebretsadik T, Abramo TJ, Hartert TV. Noninvasive testing of lung function and inflammation in pediatric patients with acute asthma exacerbations. J Asthma. 2012; 49: 29-35. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22133263
  14. Aldington S, Beasley R. Asthma exacerbations. 5: assessment and management of severe asthma in adults in hospital. Thorax 2007; 62: 447-58. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2117186/
  15. Burks AW, Tang M, Sicherer S et al. ICON: food allergy. J Allergy Clin Immunol 2012; 129: 906-20. Available from: https://www.ncbi.nlm.nih.gov/pubmed/22365653/
  16. Hodder R, Lougheed MD, Rowe BH, et al. Management of acute asthma in adults in the emergency department: nonventilatory management. CMAJ. 2010; 182: E55-67. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817338/
  17. Byrne AL, Bennett M, Chatterji R et al. Peripheral venous and arterial blood gas analysis in adults: are they comparable? A systematic review and meta-analysis. Respirology. 2014; 19: 168-75. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24383789
  18. Silverman RA, Flaster E, Enright PL, Simonson SG. FEV1 performance among patients with acute asthma: results from a multicenter clinical trial. Chest. 2007; 131: 164-171. Available from: https://www.ncbi.nlm.nih.gov/pubmed/17218571
  19. Choi IS, Koh YI, Lim H. Peak expiratory flow rate underestimates severity of airflow obstruction in acute asthma. Korean J Intern Med. 2002; 17: 174-179. Available from: http://www.ncbi.nlm.nih.gov/pubmed/12298428
  20. Karras DJ, Sammon ME, Terregino CA, et al. Clinically meaningful changes in quantitative measures of asthma severity. Acad Emerg Med. 2000; 7: 327-334. Available from: http://onlinelibrary.wiley.com/doi/10.1111/j.1553-2712.2000.tb02231.x/abstract