Homemade spirometer: what to know

Spirometry measures how much air you breathe out and how quickly you can do so. A homemade bottle, balloon, or tube cannot reliably control calibration, resistance, leaks, posture, or technique. Its result may look precise while failing to reflect your airway function. It also cannot determine whether breathlessness comes from asthma, infection, heart disease, anxiety, or another cause. A home experiment must not be used to rule out serious illness or change prescribed treatment.

If you need a baseline or have ongoing cough, wheeze, or breathlessness, arrange an assessment with a clinician. They may recommend spirometry using a calibrated spirometer, explain the breathing manoeuvre, and repeat the test when technique is adequate. Bring any symptom diary and your medicines, and ask whether you should use an inhaler before testing. Do not share mouthpieces or blow into an improvised device, since hygiene and measurement quality are uncertain.

Call emergency services for severe breathlessness, blue or grey lips, confusion, fainting, inability to speak in full sentences, or rapidly worsening symptoms. Seek prompt medical care for new breathing difficulty, chest pain, coughing blood, or a high fever with breathing problems. A normal-looking homemade reading would not make these symptoms safe.

Do I need spirometry or another lung test? Should I pause any inhaler before testing? Could my symptoms suggest asthma or another condition? Would a validated home monitor help me track changes between appointments?