Inhalers are medical devices that deliver medicine directly to the lungs, where many breathing problems begin. They are commonly used for asthma, chronic obstructive pulmonary disease, and other conditions that narrow or inflame the airways. By sending a small dose to the respiratory system, an inhaler can act faster and often uses less medicine than a pill or injection.
This makes inhalers a powerful example of engineering, chemistry, and human biology working together.
Key Facts
- A metered-dose inhaler uses a pressurized canister to release a fixed volume of drug aerosol with each actuation.
- Dose delivered per use can be estimated by total drug mass divided by number of labeled doses, dose = total mass / number of doses.
- A dry-powder inhaler relies on the patient's inhalation to pull powdered medicine into the airways.
- Good inhaler technique increases lung deposition and reduces medicine left in the mouth and throat.
- Small aerosol particles can travel deeper into the lungs than large droplets because they follow airflow through branching airways.
- Flow rate is airflow per time, Q = V / t, and it affects how well dry powder separates and enters the lungs.
Vocabulary
- Metered-dose inhaler
- A pressurized inhaler that releases a measured spray of medicine when the canister is pressed.
- Dry-powder inhaler
- An inhaler that delivers medicine as a dry powder pulled into the lungs by the user's breath.
- Aerosol
- A mixture of tiny liquid or solid particles suspended in a gas, such as medicine particles carried in air.
- Bronchioles
- Small branching airways in the lungs that help carry air toward the gas-exchange regions.
- Spacer
- A chamber attached to a metered-dose inhaler that holds the spray briefly so the user can inhale it more effectively.
Common Mistakes to Avoid
- Pressing an MDI too late or too early, which is wrong because the spray and inhalation must be coordinated for medicine to reach the lungs.
- Inhaling too weakly through a DPI, which is wrong because dry-powder inhalers need enough airflow to break up and carry the powder.
- Skipping the breath hold after inhalation, which is wrong because holding the breath for several seconds gives particles more time to settle in the airways.
- Assuming more puffs always means better treatment, which is wrong because inhalers are designed for precise dosing and extra doses can increase side effects.
Practice Questions
- 1 An MDI canister contains 24 mg of medicine and is labeled for 120 puffs. What mass of medicine is released per puff?
- 2 A patient inhales 1.5 L of air through a DPI in 3.0 s. What is the average airflow rate in L/s using Q = V / t?
- 3 Compare an MDI with a DPI. Explain why an MDI depends strongly on timing, while a DPI depends strongly on the strength of the user's inhalation.