Lung plethysmography: why breathe inside a booth?

New breathlessness without distress needs medical assessment the same day. Call 15 or 112 in France for short shallow breathing at 30 or more per minute even while seated, visible effort to breathe, difficulty speaking, blue lips or fingers, sweating, altered alertness, a very fast pulse (at least 120), a weak or slow pulse, or falling blood pressure. With breathlessness, chest pain, palpitations, leg swelling, recent weight gain or facial swelling are also emergency signs.

Lung plethysmography is one of the pulmonary function tests. It measures lung volumes, including residual volume: the air remaining in the lungs after breathing out as fully as possible.

Spirometry measures the volume of air moved and breathing flow rates, but does not directly measure this residual air. The tests therefore provide complementary information, interpreted by the specialist with the rest of the assessment.

The person sits inside a booth with a mouthpiece and nose clip. Staff ask them to breathe normally and then perform different exercises, including deep breaths and rapid breathing movements; these are repeated to obtain usable measurements.

Tell the centre about recent eye surgery, unstable cardiovascular disease or a recent pneumothorax: Nancy University Hospital lists these as contraindications to its examination. Also ask for instructions about your medicines and documents.

If the booth worries you or you feel discomfort or fatigue during the test, tell the team. Ask when the respiratory specialist will explain the results and which other measurements are needed in your situation.