According to Dr. Dang Thi Mai Khue, Deputy Head of the General Internal Medicine Department at Tam Anh General Hospital, Ho Chi Minh City, polysomnography and spirometry are distinct techniques. Depending on the patient's respiratory condition, doctors may recommend one or both methods.

**Polysomnography (Sleep Respiratory Polygraphy)**

This method records multiple parameters during a patient's sleep, helping to assess respiratory status and sleep-related disorders. Polysomnography parameters can include brain electrical activity, eye movements, muscle activity, airflow through the nose and mouth, respiratory effort, blood oxygen levels, heart rate, and sleep position. It is the standard method for diagnosing sleep apnea syndrome.

Doctors typically consider this test for patients exhibiting symptoms suggestive of obstructive sleep apnea. These include frequent loud snoring, observed breathing pauses during sleep by family members, or frequent awakenings due to choking, gasping, and restless sleep. Uncontrolled hypertension is also a factor prompting doctors to assess the risk of sleep apnea. During the day, patients may experience fatigue, unrefreshing sleep, excessive daytime sleepiness, irritability, or even accidents at home or in traffic due to drowsiness.

Not everyone who snores requires polysomnography. According to guidelines from the American Academy of Sleep Medicine, adults at risk for obstructive sleep apnea may undergo sleep respiratory polygraphy, as it can help patients fall asleep more easily.

A doctor explains sleep respiratory polygraphy results to a patient during a health check-up. Illustration: Tam Anh General Hospital

In-facility polysomnography is prioritized for patients with severe cardiopulmonary disease, neurological conditions causing hypoventilation while awake, suspected sleep-related hypoventilation, chronic opioid use, a history of stroke, or severe insomnia. These cases require a comprehensive evaluation of sleep stages, periodic limb movements, or associated neurological disorders.

**Spirometry**

This technique measures the volume and flow rate of air during inhalation and exhalation, helping to assess small airway obstruction. Spirometry is widely used in diagnosing bronchial asthma and chronic obstructive pulmonary disease (COPD).

Dr. Khue states that spirometry is indicated for patients with persistent cough, wheezing, shortness of breath, chest tightness, or recurrent respiratory symptoms of unknown cause. Long-term smokers, individuals regularly exposed to dust and chemicals, or those with a history of respiratory illness may also undergo spirometry to assess lung function.

For bronchial asthma, spirometry helps identify airflow obstruction and can be performed before and after bronchodilator administration. However, a normal spirometry result does not completely rule out asthma if clinical suspicion remains. Doctors may order additional tests, such as measuring exhaled nitric oxide, to assess allergic airway inflammation, a key mechanism in bronchial asthma.

For COPD, spirometry helps confirm small airway obstruction and its severity in patients with symptoms and risk factors. Concurrently, doctors also rely on patient presentation, medical history, and exposure levels for diagnosis.

Spirometry can also monitor disease progression and evaluate treatment response in respiratory patients. Individuals should not self-purchase or perform these tests based on a single symptom. Specifically, snoring does not equate to sleep apnea, and coughing does not necessarily mean COPD or asthma. If abnormal airway symptoms occur, consult a respiratory specialist. The doctor will take a medical history, perform an examination, and assess risk factors before determining the appropriate tests.

Nhat Thanh