What is the use of pMDI and how to use it effectively?

Pressurized metered-dose inhalers (pMDIs) have been widely used since the 1950s and are a mainstay of therapy for asthma and COPD globally. This guide explores the use of pMDI technology for respiratory treatment, detailing its function, application, and proper usage techniques.

Quick Summary

A pressurized metered-dose inhaler (pMDI) delivers a precise, aerosolized dose of medication directly to the lungs for treating respiratory conditions like asthma and COPD.

Key Points

• Targeted Delivery: The pMDI delivers medication directly to the lungs for faster, more localized action and fewer systemic side effects.

• Common Uses: pMDIs are primarily used to treat chronic respiratory conditions like asthma and COPD, administering bronchodilators for relief and corticosteroids for maintenance.

• Coordination Challenge: A major drawback is the need for precise hand-breath coordination, but this can be largely overcome by using a spacer.

• Spacer Benefits: Spacers improve medication delivery by reducing the velocity of the spray, minimizing deposit in the mouth and throat.

• Proper Technique is Key: Correct usage technique, which should be regularly reviewed with a healthcare provider, is essential for the effectiveness of the pMDI.

• Types of Medication: pMDIs can deliver both quick-relief bronchodilators for emergencies and long-term control medications like inhaled corticosteroids.

• Portability: The small size and self-contained nature of pMDIs make them a highly portable and convenient option for many patients.

Understanding the pMDI

A pressurized metered-dose inhaler (pMDI) is a small, handheld aerosol device that delivers a specific, or 'metered,' dose of medication directly to the lungs. This targeted delivery is crucial for treating respiratory diseases, as it allows the medication to act locally on the airways, leading to a faster onset of action and fewer systemic side effects compared to oral administration.

The device consists of a pressurized canister containing the medication suspended or dissolved in a propellant, a metering valve that controls the dose, and a plastic actuator with a mouthpiece. When the canister is pressed into the actuator, the propellant atomizes the drug into a fine mist for inhalation. Modern pMDIs use hydrofluoroalkane (HFA) propellants, which are more environmentally friendly than the older chlorofluorocarbon (CFC) versions.

The Specific Uses of pMDI Technology

pMDIs are central to the treatment of several chronic respiratory conditions. The type of medication delivered dictates its specific purpose, which can range from providing immediate relief to managing long-term symptoms.

• Acute Symptom Relief: Fast-acting bronchodilators, known as 'rescue inhalers,' are often administered via pMDI during an asthma attack or COPD exacerbation. Medications like albuterol relax the muscles around the airways, opening them up quickly to ease breathing.
• Long-Term Disease Management: Inhaled corticosteroids are delivered via pMDI to reduce inflammation in the lungs over time. This helps to manage chronic conditions like asthma and is a cornerstone of maintenance therapy for both asthma and COPD.
• Combination Therapies: Combination therapies are also available in single pMDIs, which can help improve patient adherence.
• Treatment of Other Conditions: pMDIs may also be used in the treatment of other diseases, such as cystic fibrosis, or even for systemic delivery of certain drugs.

Step-by-Step Guide to Proper pMDI Technique

Proper technique is paramount for effective drug delivery. While verbal instructions are standard, a demonstration is often needed to avoid critical errors. The method differs slightly depending on whether a spacer is used.

Using a pMDI Without a Spacer

Follow these steps for using a pMDI without a spacer:

1. Remove the cap from the mouthpiece.
2. If the inhaler is new or hasn't been used recently, prime it by shaking and releasing a few test sprays away from your face.
3. Shake the inhaler well for 5 seconds.
4. Exhale fully away from the inhaler.
5. Place the mouthpiece in your mouth, sealing your lips around it, and tilt your head back slightly.
6. Begin to inhale slowly and deeply through your mouth while simultaneously pressing down on the canister.
7. Remove the inhaler and hold your breath for up to 10 seconds.
8. Exhale gently.
9. If an additional puff is required, wait 30 seconds to a minute before repeating the steps.
10. If using a corticosteroid, rinse your mouth with water and spit to help prevent oral thrush.

Using a pMDI With a Spacer

Using a spacer is often recommended, especially for those who have difficulty with coordination, as it improves medication delivery to the lungs and reduces deposition in the mouth and throat. Here's how to use a pMDI with a spacer:

1. Shake the inhaler and insert it into the spacer.
2. Exhale gently and completely away from the mouthpiece.
3. Place the spacer's mouthpiece in your mouth and seal your lips around it.
4. Press down on the inhaler canister once to release a puff into the spacer chamber.
5. Take 4-5 normal breaths in and out through the mouthpiece, or take one slow, deep breath and hold it for 10 seconds.
6. If more doses are needed, wait and repeat the process.
7. After using a corticosteroid, rinse your mouth with water and spit.

Comparison of Inhaler Devices

Feature	pMDI	DPI	Nebulizer
Drug Form	Aerosol (liquid or suspension)	Fine powder	Fine mist (aqueous solution/suspension)
Coordination	Requires slow, steady inhalation synchronized with actuation.	Breath-activated; requires quick, deep inhalation.	No coordination required; patient breathes normally.
Propellant	Yes (HFA).	No.	No.
Portability	Highly portable, compact, and discreet.	Highly portable and compact.	Bulky, requires a power source.
Spacer Use	Recommended to improve delivery.	Not used.	Not applicable.
Ideal Patient	Most patients, especially with a spacer.	Patients with good inspiratory flow.	Infants, elderly, or severely breathless patients.

Benefits and Challenges of pMDIs

Advantages

• Portability: pMDIs are small and easy to carry.
• Multidose Capability: Each canister contains multiple doses.
• Cost-Effectiveness: pMDIs are often more affordable.
• Reduced Contamination: The sealed system helps minimize bacterial contamination.

Disadvantages and Limitations

• Coordination Difficulty: Synchronizing pressing the canister with inhaling can be challenging for some users.
• Oropharyngeal Deposition: Medication can deposit in the mouth and throat, potentially causing side effects like thrush. Using a spacer can help reduce this.
• Environmental Impact: While improved, HFA propellants still have some environmental concerns.
• Cold Freon Effect: The cold spray can sometimes cause users to stop inhaling prematurely.

Conclusion

The pMDI remains a vital tool in managing respiratory conditions, offering a portable and cost-effective way to deliver medication directly to the lungs. Using a spacer is highly recommended to improve the effectiveness of the pMDI. Regular review of proper technique with a healthcare professional is crucial.

For more information on respiratory health and inhaler technique, consider visiting the {Link: American Lung Association website https://www.lung.org/}.

Frequently Asked Questions

What is the primary function of a pMDI?

The primary function of a pMDI is to deliver a precise, aerosolized dose of medication directly into a patient's lungs for treating respiratory conditions like asthma and COPD.

When is it recommended to use a spacer with a pMDI?

Using a spacer is recommended for most pMDI users, especially children, the elderly, or those with difficulty coordinating the 'press and breathe' action. A spacer increases the amount of medicine that reaches the lungs.

What types of medication are delivered by pMDIs?

pMDIs can deliver bronchodilators (e.g., albuterol for quick relief) and inhaled corticosteroids (for long-term control), which are used for conditions like asthma and COPD.

Do I need to shake my pMDI before each use?

Yes, it is crucial to shake the inhaler well for about 5 seconds before each use to ensure the medication is properly mixed and an accurate dose is delivered.

What is the 'cold freon effect' associated with pMDIs?

The 'cold freon effect' is a cold sensation from the evaporating propellant that can cause a patient to prematurely stop inhaling. Newer HFA propellants are warmer and may reduce this effect.

Why do some pMDIs cause oral thrush?

When using a corticosteroid pMDI without a spacer, a significant amount of the medication can deposit in the mouth and throat. This residue can lead to an oral yeast infection (thrush). Rinsing your mouth and spitting after each use can help prevent this.

Is a pMDI more effective than a nebulizer for treating asthma attacks?

For mild-to-moderate asthma attacks, studies suggest that a pMDI used with a spacer is at least as effective as a nebulizer and may lead to fewer side effects and shorter treatment times.