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KNOW HOW Inhaler devices

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VOL: 96, ISSUE: 37, PAGE NO: 16

Linda Pearce, MSc, RN, SCM, OHNc, NPDip, respiratory specialist nurse, West Suffolk Hospital

Sponsored by an education grant from Allen & Hanburys

Types of metered dose inhalers

Types of metered dose inhalers
Unadapted
In these metered-dose inhalers (Fig 1), the aerosol leaves the canister at speeds of 60-90mph (slower for some CFC-free aerosols).

It is difficult to learn the technique of coordinating actuation and inhalation efficiently, and to inhale at the correct inspiratory flow rate. These inhalers should be reserved for patients who can consistently show they are able to use them correctly.

Technique

1. Remove mouthpiece cover;

2. Shake the MDI and breathe out;

3. Close lips and teeth around mouthpiece;

4. At the start of inspiration, press the canister down and continue to inhale slowly and deeply (ideal rate 20-40L/min);

5. Remove device from mouth and close lips;

6. Hold breath for 10 seconds, or as long as is comfortable.

If a second dose is required, wait 30-60 seconds and repeat steps 2 to 6 before replacing the cover.

Points to consider

- MDIs are often misused, with the most common fault being a failure to inhale, at the appropriate rate at the same time the device is actuated;

- They are generally not suitable for children;

- CFC-free inhalers for the delivery of salbutamol, beclomethasone dipropionate, fluticasone propionate and salmeterol/ fluticasone propionate combination are available.

Adapted
Various modifications have been developed for MDIs, with the purpose of reducing the problems associated with coordinating actuation and inspiration. Some also improve deposition of the drug in the lungs.

Extension tubes are used to reduce the speed at which the aerosol cloud is travelling when it reaches the mouth.

Technique

1. Remove cap;

2. Fit or extend the spacer tube;

3. Shake MDI and breathe out;

4. Close lips and teeth around mouthpiece;

5. At the start of inspiration, press the canister down and continue to inhale slowly and deeply (ideal rate 20-40L/min);

6. Remove device from mouth and close lips;

7. Hold breath for 10 seconds, or as long as is comfortable;

If a second dose is required, wait 30-60 seconds and repeat steps 2 to 7 before removing or closing the tube and replacing the cap.

Points to consider

- These modifications assist but do not remove the need for coordination of actuation and inhalation;

- Aerosols with a fixed extended mouthpiece and vortex technology fit into this category. A vortex slows the aerosol cloud to less than 10mph.

Spacer devices
This includes Volumatic (Fig 2), Nebuhaler, Babyhaler (Fig 3), Aerochamber and Able Spacer.

These are chambers of various sizes that act as a reservoir for the aerosol cloud, removing the need for coordination. Retention of the larger particles in the device reduces systemic deposition, which may be a consideration when steroids with oral bioavailability are being used. The devices may be fitted with a mask, which can aid administration of medication to infants (McCarthy, 1990). Where a mask is fitted to a Volumatic or Nebuhaler device, the inhaler may be tilted to help the valve fall open.

Although these devices are more effective and easier to use than metered-dose inhalers alone, they are bulky and have limitations in terms of peer acceptability and lifestyle.

Technique

1. If necessary, fit the halves of the spacer together;

2. Remove the cap from the MDI;

3. Fit the MDI to spacer device;

4. Shake the MDI and breathe out;

5. Close lips and teeth around mouthpiece;

6. Actuate the device;

7. Inhale deeply and slowly (ideal rate 20-40L/min);

8. Remove the device from mouth, and close lips;

9. Hold breath for 10 seconds;

If a second dose is required, wait 30-60 seconds and repeat steps 4 to 9.

NB Tidal breathing may be used instead of steps 7-9. It may make using the device easier, especially for children and older people.

Points to consider

- The dose should be inhaled within 10 seconds, as settling of the drug reduces deposition (O'Callaghan et al, 1993);

- Spacers should be washed and air-dried, as static can halve the amount of drug available (Pierart et al, 1997).

- Single rather than multiple actuations should be used, as the latter will reduce the drug available for inhalation;

- MDIs are not necessarily compatible with all spacer devices. Deposition differences may be as great as 50% between models (Barry and O'Callaghan, 1996);

- When masks are used they should be closely applied, as a gap of more than 1cm between mask and face will greatly diminish drug deposition;

- Spacers are important in treating acute severe asthma; they are as effective as nebulisers for administering b2 agonist medication (Cates, 1997).

Breath-actuated inhaler devices
The Easibreathe and Autohaler devices are examples of this type of inhaler. A vacuum-operated trigger mechanism actuates the device when the patient inhales. The technique to use it is simple to teach, but these devices are bulkier than unadapted MDIs.

Technique

1. Remove or open cap;

2. If necessary, prime the device;

3. Shake device and breathe out;

4. Close lips and teeth around mouthpiece;

5. Inhale deeply and slowly (ideal rate 20-40L/min);

6. Remove the device from mouth and close lips;

7. Hold breath for 10 seconds (or as long as is comfortable);

8. Close cap (this action primes the Easibreathe);

9. With the Autohaler, push the lever back down.

If a second dose is required, wait 60 seconds and repeat steps 1 to 9.

Points to consider

- Some of these devices produce a click on inspiration, which may inhibit full inhalation;

- They are unsuitable for children under five;

- There is no need for coordination of actuation and inhalation when using these devices.

Types of dry powder inhalers
These devices are breath-operated, removing the need for coordinating actuation and inhalation.

A degree of internal resistance is built into them so that, on inhalation, the powder will be disaggregated into particles of different sizes to produce a respirable fraction (generally regarded as 2-5 microns). This is important, as only particles that are smaller than 5 microns will penetrate the smaller airways.

The internal resistance varies between devices and determines the effort needed to achieve a given inspiratory flow rate. For example, to achieve an inspiratory flow rate of 60L/min through a Turbohaler requires nearly three times the effort needed with a Diskhaler (Richards and Saunders, 1993). The Rotahaler, Diskhaler and Accuhaler have low internal resistance compared with the Spinhaler or Turbohaler.

It is important that patients do not breathe out into any of these devices after they have been loaded, as the moisture may cause the powder to clog.

Lactose is added to the drug in some devices to act as a bulking agent and to aid disaggregation; it can also provide a taste reassurance that the dose has been taken.

Dry-powder inhalers come as single and multiple-dose devices.

Single-dose devices
Examples of single-dose inhalers are the Rotahaler, Spinhaler and Aerohaler. These hold the drug in gelatin capsules. Each dose must be loaded separately; however, loading the devices may be fiddly, and careful instruction is needed.

The way the capsule is pierced or broken varies between devices. In the Spinhaler and Aerohaler, pins are used to pierce the capsule; in the Rotahaler, twisting the two halves of the device breaks the capsule.

Technique

1. Fit capsule into the device;

2. Pierce or break capsule;

3. Breathe out;

4. Close lips and teeth around mouthpiece;

5. Inhale sharply and deeply (ideal rate 30-60L/min);

6. Remove device from mouth and close lips;

7. Hold breath for 10 seconds, or as long as is comfortable.

Points to consider

- Careful instruction is needed on how to load and remove the capsules;

- More than one inhalation may be needed to empty all the powder from the device;

- The capsules must be kept in a cool dry place, as changes in temperature and humidity affect their effectiveness.

Multiple-dose devices
Multiple-dose inhalers include the Accuhaler, Clickhaler, Diskhaler and Turbohaler.

They hold the medication in a drug reservoir, or in individually sealed doses. The individual doses have greater through-life dose consistency (Malton et al, 1995).

Accuhaler
The Accuhaler holds 60 individually sealed doses (Fig 4).

Technique

1. Open the case;

2. Slide the lever as far as it will go until it clicks;

3. Breathe out;

4. Close lips and teeth around the mouthpiece;

5. Inhale deeply (ideal rate 30-90L/min);

6. Remove device from mouth and close lips;

7. Hold breath for 10 seconds, or as long as is comfortable;

8. Close the case.

Points to consider

- If the dose is not inhaled after loading the device, powder will collect inside it, which will result in a gritty feel when the trigger is subsequently pressed. This can indicate that the device is being used incorrectly, or that doses are being wasted. This feature can support adherence and technique checks;

- The dose counter registers individual doses from 60 to 0, with the last five doses indicated in red.

Clickhaler
The Clickhaler carries 200 doses in a reservoir.

Technique

1. Remove mouthpiece cover;

2. Shake the device well;

3. Hold it upright and press the top once until a click is heard;

4. Breathe out;

5. Close lips and teeth around mouthpiece;

6. Inhale deeply;

7. Remove the device from mouth and close lips;

8. Hold breath for 10 seconds, or as long as is comfortable;

9. Replace mouthpiece cover.

Points to consider

- The device must be kept in a dry place, as the drug reservoir is susceptible to the effects of moisture;

- The cap must always be replaced;

- Once the foil pouch has been opened and the inhaler removed, it must not be used for more than six months;

- The Clickhaler counts individual doses up to 190, with the last 10 doses indicated in red and counted in reverse - down to zero.

Diskhaler
The Diskhaler carries four or eight individually sealed doses in a disk.

Technique

1. Remove mouthpiece cover;

2. Fit disc into device, numbers uppermost, slide tray in and out to rotate disk, until the highest number appears in the window;

3. Hold the device level, lift lid until it is upright, so the needle pierces the blister;

4. Close lid;

5. Breathe out;

6. Close lips and teeth around mouthpiece, do not cover air holes on either side of mouthpiece;

7. Inhale deeply (ideal rate 30-40L/min);

8. Remove device from mouth and close lips;

9. Hold breath for 10 seconds, or as long as is comfortable;

10. Slide tray in and out ready for next dose;

11. Do not pierce the next blister until the device is to be used;

12. Replace mouthpiece cover.

Points to consider

- The technique for using this device may be regarded as fiddly, so careful instruction is necessary;

- The patient must be shown how to replace the disk once all doses have been used.

Turbohaler
The Turbohaler carries 50 to 200 doses in a reservoir.

Technique

1. Remover cap;

2. Holding device upright, twist base fully anticlockwise, then clockwise until click is heard;

3. Breathe out;

4. Close lips and teeth around mouthpiece;

5. Inhale forcefully and deeply (ideal rate 60-90L/min);

6. Remove device from mouth and close lips;

7. Hold breath for 10 seconds, or as long as is comfortable;

8. Replace cap.

Points to consider

- If a sufficient inspiratory flow (at least 60L/min) is not achieved, the proportion of fine particles available for inspiration may be halved (Persson et al, 1997);

- The patient should be instructed not to handle the device roughly (Devadason et al, 1996);

- The device should be loaded at an angle of no more than 45° from the vertical;

- It should not be kept in humid conditions unless the cap is tightly closed;

- A red mark will appear in the window when about 20 doses remain.

Nebulisers
Nebulisers (Fig 5) play an important part in managing asthma. Their role in asthma management should be limited to emergencies only, where high doses of drug are required, and in situations where the patient is unable to use any other form of inhaler device.

There are two main types of nebuliser - compressor-driven and ultrasonic.

Technique

1. The tubing is connected to the compressor/ultrasonic generator and the nebuliser chamber;

2. The medication is placed in the nebuliser chamber;

3. A mask is fitted and placed over the patient's nose and mouth, or a mouthpiece may be used;

4. The compressor/ultrasonic generator is switched on;

5. The patient should mouth-breathe for 5-10 minutes (until the dose has been taken);

Points to consider

There are several points that the health professional should consider before recommending the use of nebulisers.

- They are expensive;

- They need to be regularly cleaned and maintained;

- They are time-consuming to use;

- They achieve about the same deposition as an MDI, but are less efficient and effective compared with an MDI or large-volume spacer device;

- Patients often use them to administer bronchodilators. An undue reliance on their effectiveness may delay the seeking of appropriate medical advice;

- The droplet size and dose delivery of nebulisers can vary;

- Ultrasonic nebulisers do not nebulise corticosteroid suspensions effectively, so these should be avoided.

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