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The re-usable Respimat® Soft Mist™ inhaler

Dr Kevin Gruffydd-Jones, FRCGP, GP, Box, Wiltshire

Introduction

The Respimat® Soft Mist™ inhaler (SMI) is a handheld propellant-free device that produces a slow-moving, long-lasting mist of drug for inhalation. The original Respimat inhaler has been available since 2007, but in September 2019 it became available in the UK as a re-usable device. 

This article highlights the main features of the Respimat SMI, compares it with other inhaler types, describes the key features of the re-usable device, and discusses the environmental impact of its use. 

 

 

Mechanism of action of the Respimat SMI

The active drug used with the Respimat inhaler is formulated in aqueous solution with benzalkonium chloride as a preservative.1 When a cartridge containing the drug is inserted into the base of the inhaler, the device needs to be primed to expel air from the drug solution flow path. To load a dose, the patient has to turn the base of the device by half a turn. This tightens the helical spring that lowers and opens up the non-return valve, drawing a metered volume of the drug solution via the capillary tube into the loading chamber. The drug is delivered when the patient presses the dose-release button, which uncoils the spring.1 Figure 1 shows the internal design of the Respimat inhaler. 

Figure 1 Respimat supplement - internal mechanism

Figure 1: Schematic diagram of the internal mechanism of the Respimat inhaler.2

The mechanical power of this action drives the drug solution through a series of fine channels of silicon wafer enclosed in a ‘uniblock’ (see Figure 2), causing two fine jets of liquid to emerge through the twin nozzles of the uniblock. These fine jets converge on each other at such an angle that a slow-moving aerosol, ‘soft mist’, is produced.1

The soft mist is delivered with a high fine particle fraction of 75% (nearly double the value reported for aerosols emitted by a standard pressurised metered dose inhaler [pMDI] or dry powdered inhaler [DPI]) and with a slow velocity (3–10 times slower than the aerosol emitted from a pMDI).1 This allows low oropharyngeal deposition and high lung deposition, minimising oropharyngeal side-effects and reducing the dose of drug that needs to be used to be effective. In addition, the spray duration of the Respimat SMI is considerably longer than for pMDIs (1.2 seconds vs. 0.15–0.36 seconds, respectively), allowing a longer time for the patient to coordinate their inhalation with the release of the drug.1

nozzle

 

Figure 2: Schematic diagram of the Respimat uniblock nozzle.3

Respimat SMI vs other devices

Lung deposition

A study analysing lung and oropharyngeal deposition of fenoterol[A] (a short-acting beta2 - agonist) when administered via the Respimat SMI compared to when administered via a pMDI or pMDI plus spacer in healthy volunteers, showed that the mean oropharyngeal deposition of fenoterol was significantly lower via Respimat SMI than via pMDI (37.1% vs 71.1%, respectively). Lung deposition was significantly higher via Respimat SMI than via pMDI (39.2% vs 11%, respectively).4 Comparable results were obtained in a similar study performed on patients with asthma.5

The re-usable Respimat SMI 

In the UK, the re-usable version of the Respimat inhaler was launched in September 2019. The original Respimat inhaler was updated to simplify assembly, improve handling, and make it re-usable.

Figure 3 highlights the differences and retained features between the disposable and re-usable inhalers.

Disposable vs reusable

Figure 3: Differences between the disposable (left) and the re-usable (right, front and back) Respimat SMI; features that have been added or changed in the re-usable version are labelled in red.

Key features of the re-usable device compared to the disposable are:

  • a locking device attached to the cartridge rather than to the device, which prevents further use of the device when the cartridge is empty and releases a safety catch allowing the clear base to be pushed away, alerting the user that the cartridge needs replacing
  • an improved dose counter on the cartridge, with the number of doses left clearly displayed; the dose counter changes colour when only 10 doses are left, clearly indicating to the patient that the cartridge will need to be replaced soon (Figure 4)
  • a longer base to improve grip and to make twisting the device easier. 

Comparative studies performed by Dhand et al. showed that the re-usable Respimat inhaler has improved usability compared to the disposable device, but no differences in drug delivery, aerosol particle size, and required inhalation method across multiple cartridge use.6 Performance of the re-usable Respimat inhaler has been shown to be comparable to that of the disposable inhaler, so lung deposition and clinical data established on the disposable inhaler can be applied to the re-usable one.6

Moreover, small-scale studies in patients with asthmas and/or COPD (n=16) showed that 4 people out of 16 felt that the process was ‘equally easy’ in both inhalers, while the remaining 12 people considered the cartridge insertion process to be ‘easier’ or ‘much easier’ with the reusable Respimat than with the disposable Respimat. Patients particularly liked the easily readable dose counter.6

Respimat cartridge

Figure 4: New cartridge dose counter

Environmental benefits of the re-usable Respimat SMI 

The NHS Long Term Plan for England 20197 has committed the NHS to reducing greenhouse gas emissions from inhalers. Traditional pMDIs use hydrofluoroalkane (HFA) propellants, which have a high global warming potential.

The re-usable Respimat SMI is propellant-free, and, due to its re-usability, is potentially more environmentally friendly. In fact, re-using the inhaler with more than one cartridge further reduces its product carbon footprint (PCF).

These potential environmental benefits were examined in a study which compared the PCF of Respimat with that of pMDIs.8 The PCF looks at the carbon footprint of the product during its life cycle, including production, packaging, usage, and disposal, and is expressed in kg CO2 equivalent (eq). This study found that the PCF of the Respimat was approximately 20 times lower than a pMDI (0.78 kgCO2 eq vs. 14.59 kgCO2 eq, respectively), mainly due to the lack of propellant in the Respimat, and found a further reduction of 73% in the PCF after 6 months’ use of the re-usable versus disposable Respimat when six cartridges are used with one inhaler (due to the lower carbon impact of using less material in manufacturing the device).8

Use of the re-usable Respimat SMI in clinical practice

International9,10 and national11,12 asthma and COPD guidelines emphasise the importance of inhaler choice and technique linked to outcomes. It is generally acknowledged that there is no one inhaler type that ‘fits all’ and inhaler prescription should be tailored to the individual patient. The National Institute for Health and Care Excellence (NICE) produced a clinical decision aid for patients with asthma to help them and the prescriber to come to a decision on which inhaler to prescribe.13

The key features that a patient is asked to consider are:

  • being able to use the inhaler correctly and easily
  • being able to tell how many doses are left in the inhaler
  • having to clean the inhaler frequently
  • being able to carry the inhaler around
  • that the inhaler has a low carbon footprint.

In line with this, the re-usable Respimat SMI has been shown to have high patient acceptability,1 a distinct cartridge counter, a clear dose indicator,6 and lower carbon footprint compared to pMDIs.8

Instructions on how to use the re-usable Respimat SMI are shown in Figure 5.

How to use Respimat

Figure 5: How to use the re-usable Respimat SMI

Summary

The re-usable Respimat SMI was introduced in the UK in September 2019. It incorporates many of the features of the original Respimat device, which delivers a propellant-free slow-moving, long-lasting soft mist aerosol with improved lung deposition, lower environmental impact, and more time for co-ordinated inhalation with release of drug, than traditional pMDIs. The re-usable inhaler has the additional advantage of an updated design to improve cartridge exchange and a clearer dose counter.

The ability to use the same device with up to six cartridges increases convenience for the patients and further reduces the environmental impact of inhaler use. 

Conflicts of interest

Kevin Gruffydd-Jones has acted as a consultant and spoken on behalf of GlaxoSmithKline, AstraZeneca, Teva, Napp, Boehringer Ingelheim, Novartis, and Chiesi. He is a member of the NHS England Sustainable Inhaler Committee.

References

  1. Dalby R, Eicher E, Zierenberg B. Development of Respimat® Soft MistTM Inhaler and its clinical utility in respiratory disorders. Med Devices (Auckl) 2011; 4: 145–155.
  2. Boehringer Ingelheim Ltd. Data on file. Pharmaceutical development report for Respimat® ReUsable® 2017; document number: q00240658-01.
  3. Watchel H, Kattenbeck S, Dunne S et al. The Respimat® development story: patient-centered innovation. Pulm Ther 2017; 3: 19–30.
  4. Newman S, Brown J, Steed K et al. Lung Deposition of fenoterol and flunosolide delivered using a novel device for inhaled medicines. Chest 1998; 113: 957–963.
  5. Pitcairn G, Reader S, Pavia D et al. Deposition of corticosteroid aerosol in the human lung by Respimat Soft Mist inhaler compared to deposition by metered dose inhaler or by Turbohaler dry powder inhaler. J Aerosol Med 2005; 18: 264–272.
  6. Dhand R, Eicher J, Hansel M et al. Improving usability and maintaining performance: human-factor and aerosol—performance studies evaluating the new reusable Respimat inhaler. Int J COPD 2019; 14: 509–523.
  7. NHS England. NHS Long Term Plan 2019. Available at: www.longtermplan.nhs.uk (accessed 26 November 2019).
  8. Hänsel M, Bambach T, Wachtel H. Reduced Environmental Impact of the reusable Respimat® Soft MistTM Inhaler compared with pressurised metered-dose inhalers. Adv Ther 2019; doi.org/10.1007/s12325-019-01028-y
  9. Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. 2019 report. Available at: goldcopd.org/gold-reports/ (accessed 26 November 2019).
  10. Global Strategy for Asthma Management and Prevention 2019. Global Initiative for Asthma (GINA) 2019. Available at: www.ginasthma.org (accessed 26 November 2019).
  11. NICE. Chronic obstructive pulmonary disease in over 16s: diagnosis and management. NICE guideline 115. NICE, 2019. Available at: www.nice.org.uk/NG115
  12. British Thoracic Society/Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. SIGN 158. Available at: www.sign.ac.uk/assets/sign158.pdf (accessed 26 November 2019).
  13. NICE. Asthma: diagnosis, monitoring and chronic asthma management. Tools and resources. NICE guideline 80. NICE, 2017 www.nice.org.uk/ng80/resources (accessed 26 November 2019).
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This supplement has been commissioned and funded by Boehringer Ingelheim Ltd and developed in partnership with Guidelines. Boehringer Ingelheim Ltd suggested the topic and author, and carried out full medical approval on all materials to ensure factual accuracy and compliance with the ABPI Code of Practice. The sponsorship fee included an honorarium for the author. The views and opinions of the author are not necessarily those of Boehringer Ingelheim Ltd, or of Guidelines, its publisher, advisers, or advertisers. No part of this publication may be reproduced in any form without the permission of the publisher.

PC-GB-100150 V1

Date of preparation: January 2020