Which factor does NOT affect the performance of a metered-dose inhaler (MDI)?

The performance of a metered-dose inhaler (MDI) can be influenced by various factors that directly affect how the medication is aerosolized and delivered to the lungs. However, the patient’s age does not inherently impact the mechanical function of the inhaler itself.

Instead, factors such as temperature can alter the pressure within the canister, which affects the spray density and drug delivery. Nozzle size and cleanliness are crucial because a blocked or dirty nozzle can prevent proper aerosolization of the medication, leading to reduced effectiveness. Additionally, the timing of actuation intervals is important because it affects how effectively the medication is inhaled and deposited in the airways.

While age may influence overall lung function or the ability to use the inhaler correctly, it does not inherently change the actual performance characteristics of the MDI itself. Therefore, this understanding underscores the distinction between how the inhaler operates and the user's individual factors.