Do I need to hold my breath for a lung function test during a physical examination?

Pulmonary function tests usually require a decision on whether to hold your breath based on specific items, with some items requiring brief breath holding and others requiring continuous breathing movements. The diffusion function test in pulmonary function examination requires the subject to hold their breath for 5-10 seconds at the end of inhalation, during which the gas exchange process between alveoli and capillaries can be accurately measured. Forced lung capacity test requires deep inhalation followed by rapid exhalation with explosive exhalation during the initial stage, and maintaining a stable exhalation flow rate in the middle and later stages. The bronchial dilation test may require multiple respiratory cycle tests before and after inhalation of medication, during which the breathing rhythm must be strictly adjusted according to the technician's instructions. New detection methods such as pulse oscillation technology only require calm breathing and evaluate airway resistance through the principle of sound wave oscillation, without the need for deliberate holding of breath. The residual gas measurement is carried out using gas dilution method or volumetric chamber method. The former requires the subject to breathe continuously for several minutes at a specific respiratory rate, while the latter requires the completion of different respiratory state transitions in a closed chamber. Smoking, alcohol consumption, and vigorous exercise should be avoided 24 hours before the SEP examination, and bronchodilators should be temporarily suspended according to medical advice. Wearing loose clothing facilitates chest and abdominal breathing and movement, and those with dentures should remove them in advance to prevent affecting the sealing of the oral cavity. During the inspection, maintain a proper sitting posture, tightly wrap your lips around the bite device to prevent air leakage, and seal your nasal cavity with a nose clip. If there is hemoptysis, pneumothorax, myocardial infarction or unstable angina recently, one should proactively inform the doctor. Patients with chronic obstructive pulmonary disease may experience severe coughing during testing and may request a brief rest before resuming. After the examination, normal drinking and eating are sufficient, but it is necessary to observe whether there are any discomfort symptoms such as dizziness and chest tightness. Elderly people and cardiovascular disease patients are recommended to rest for 15 minutes after the test before leaving.