Common Mistakes with inhaler Technique

Transcription

1 Common Mistakes with inhaler Technique Inhaling medication into the lungs can be very effective - but frequently it is not. The most common reasons for patients not responding to treatment are:- Being given an inappropriate inhaler Not using the inhaler device properly Failing to take the medication as directed Over recent years, more health professionals have received specialist training on respiratory medicine, but until the differences between devices are fully understood by all prescribers, there is a risk that patients may not be given the delivery device best suited to their needs and abilities. Recent developments that help have included an instrument that measures the ability to use different inhalers (the "In-Check" device from Clement Clarke) and national funding for "Medicines Usage Reviews" by speciallytrained UK pharmacists (their recommendations on inhaler device use are noted by the patient's family doctor). The most common mistakes seen when patients use a pmdi are:- 1. Not shaking the canister before use 2. Not breathing out before inhaling 3. Inhaling too early before pressing the canister 4. Inhaling too late after pressing the canister 5. Inhaling too fast 6. Not continuing to breathe in after pressing the canister 7. Not holding your breath after inhalation Each is discussed below, with an explanation of how they affect the user. 1. Not shaking the canister before use When the canister is pressed, a measuring system at the base of the canister releases a precise volume of liquid into the inhaler's nozzle, which then rapidly evaporates to produce the aerosol cloud or "mist". If the contents of the canister (propellant and medication) are not mixed thoroughly, then too much or too little of one component will be released. Inconsistent dosing and poorly-functioning inhalers often result from not shaking the canister properly. 2. Not breathing out before inhaling For medication to work effectively, it is important that the aerosol created by the inhaler reaches the small airways deep inside the lungs. Obviously, the only way for a cloud of aerosol to reach these areas is by being carried along with the next breath in.

2 Breathing out fully (or as much as is comfortable), reduces the amount or air in the small airways, and increases space available for air from the next breath. The result is a deeper than normal inhalation, that can last longer, maximising the opportunity to carry all of the aerosol "cloud" created by the inhaler to where it is needed. Not breathing in deep enough reduces the amount of drug reaching the small airways, and means less time to coordinate pressing the canister. 3. Inhaling too early before pressing the canister To deliver the medication to the lungs, the patient must coordinate breathing in with pressing the canister, so the aerosol cloud is carried in the air inhaled into the lung. Starting too early can mean the breath in has finished (and the lungs are full) even before the canister has been pressed, particularly if the inhalation is very fast. The result is medication being sprayed into the mouth, but going nowhere. Breathing in too early can mean little or no medication gets to the lungs, as the lungs are full before the aerosol is released. Side-effects risk is increased. 4. Inhaling too late after pressing the canister To deliver the medication to the lungs, the patient must coordinate breathing in with pressing the canister, so the aerosol cloud is carried in the air inhaled into the lung. The time between pressing the canister and the last part of the medication being released form the inhaler is less than half a second - any delay between pressing the canister and starting the inhalation means some of the medication will just impact in the mouth and throat. Starting your breath in too late can mean little or no medication gets to the lungs, as the aerosol has already been released. Side-effect risk is increased. Mistakes of technique are common to both patients and health professionals For many years researchers have investigated how well patients use inhaler devices, and frequently report on the "misuse" of inhalers and how specific steps in the recommended technique for each device are not followed. However, the ability to perform all steps correctly has also been found to be a problem for health professionals - many Doctors, Nurses and Pharmacists have all been found unable to demonstrate the optimum techniques - a powerful reminder of the need for improved education, even for the professionals. More than 83% of patients demonstrated inadequate technique when using their pmdi Erickson S et al, J Asthma Only 1 health professional in 206 could inhale at the optimum speed for the commonly-used pmdi

3 Pearce L, Am J Respir Crit Care Med Inhaling too fast It is the Laws of Physics that can help explain why breathing in too quickly is not helpful; particles in moving air will follow the path that the air takes until a change in direction occurs, at which time they will try to continue to move in the same direction they were travelling in (their "momentum"). If the change in direction is more than small, there is a risk the particles will impact on the airway wall. The risk of impaction increases as the particles get larger, and also as the speed of the air increases. Too fast an inhalation results in more impaction of aerosol at the points where the airways change direction significantly - particularly at the throat and where the main airways of the lung branch out. When the site of action of most drugs is the small airways, then medication being deposited at these places is not beneficial. A second problem occurs when MDI users breathe in too quickly; there is less time to coordinate pressing the canister. The ideal inspiratory flow rate for using a pmdi is less than 60 l/min, but many users inhale at over 180 l/min. As the volume of air someone inhales remains the same no matter how fast they breathe in, then a fast inhalation occurs in one third of the time, leaving much less time to press the canister. A reduction in the amount of medication that reaches the lungs is seen when the inhalation through an MDI is too fast - it also increases the (unwanted) deposition in the throat. Coordination suffers if inhalation is too fast, because the time taken to fill the lungs is reduced. 6. Not continuing to breathe in after pressing the canister Inhaling deeply maximises the opportunity for the aerosol particles to reach the furthest parts of the lungs, where they have maximum effect. Stopping the breath in as soon as the inhaler has been "fired" will mean that some air/medication mix will not have reached the bronchioles and alveoli (the small airways that respond to the medication). Instead, it will remain in the larger airways, as no additional air was inhaled. Inhaled aerosols are likely to penetrate deeper into the lungs if the inhalation is full, and the user continued to inhale after the canister was pressed. 7. Not holding your breath after inhalation Having ensured the aerosol of medication particles has reached the small airways (by following all the other recommended steps), the "breath hold" increases lung deposition through the process of "sedimentation". By keeping the air still for a few seconds, a greater number of particles will fall onto the airways walls (due to gravity). It has been found that 10 seconds breath hold

4 is ideal, but even if this is not possible, many people can benefit from holding their breath for as long as is comfortable after inhaling. Breathing out too soon after inhaling through an MDI means a part of the dose that has managed to reach the small airways is lost during exhalation. Using an inhaler properly during an asthma attack? It should be remembered that unlike COPD, asthma is a disease where the ease of getting air into and out of the lungs varies - during an attack it may be more difficult for the asthmatic to inhale through their inhaler (which may be important if they are using dry powder inhaler). For the low resistance of a pmdi, it will usually be possible to achieve the flows required for best performance, but only if the user can avoid rushing the use of the device (most often because they want to get relief from their inhaler as quickly as possible). At a time when optimum drug delivery would benefit the patient most, correct use of the pmdi may not occur - unless the user has learnt how to get the technique right previously, and can remember each of the recommended steps. Useful websites: Asthma UK is the charity dedicated to changing the outlook on asthma. It has patient management plans, leaflets and an inhaler demonstration video. How to make the most of being asthmatic Your health, your choices. Has videos on asthma and inhaler technique. Offers medical information and support with printable leaflet Video demonstrations on correct inhaler technique

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