June 16, 2024

Understanding Spirometer and its importance in Diagnosing Respiratory Diseases

A spirometer is a medical device used to measure lung capacity and how well a person can exhale air from their lungs. It measures the volume of air inhaled or exhaled over a period of time. The test that uses a spirometer is called spirometry. Spirometry is one of the basic and most common types of pulmonary function tests used to evaluate lung health. Some key facts about spirometers:

– Spirometers come in both disposable and reusable models. Disposable spirometers are used once to avoid risk of cross-contamination, while reusable models can be sterilized between each use.

– The patient blows into a mouthpiece attached to the spirometer. Their breath moves an indicator such as a spinning dial, floating marker or digital readout to measure exhaled volumes.

Spirometer measure volumes like forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEF) and other parameters.

– Data from the test is downloaded onto a computer for analysis and comparison to reference values based on age, height, sex and ethnicity.

Uses and Importance of Spirometry

Spirometry is an important tool used by doctors to diagnose and monitor respiratory diseases. Some key uses and importance of spirometry include:

– Diagnose obstructive diseases: Spirometry can detect airway obstruction that occurs in conditions like asthma, chronic obstructive pulmonary disease (COPD) and bronchitis. An abnormally low FEV1/FVC ratio suggests airway blockage.

– Diagnose restrictive diseases: Lung restriction from interstitial lung disease or chest wall disorders cause reduced FVC. Spirometry may assist in differentiating restrictive from obstructive defects.

– Evaluation of asthma and COPD severity: Spirometry is essential for determining disease severity, control and risk of exacerbations in asthma and COPD patients. It helps guide treatment decisions.

– Pre-operative evaluation: Spirometry can identify high-risk patients and optimise treatment before major surgery to prevent complications from poor oxygenation and ventilation.

– Occupational lung disease screening: It can detect work-related lung problems caused by inhaled dusts, chemicals or gases, allowing early interventions to slow disease progression.

– Monitor response to treatment: Spirometry enables objective monitoring of treatment response over time. Improvements in FEV1 and other parameters with appropriate therapies indicate treatment is effective.

– Longitudinal tracking of lung health: Regular spirometry provides quantitative data to track annual decline in lung function with age, detect accelerated losses indicating chronic lung damage.

How is a Spirometry Test Performed?

Here are the basic steps involved in performing a spirometry test:

– The patient is made to sit upright and wear a nose clip to ensure accurate mouth measurements are obtained.

– They are taught how to seal their lips tightly around the mouthpiece and blow out as fast and hard as possible after a deep breath.

– They practice the maneuver without the instrument a few times until the technician is sure they can do it correctly.

– For the actual test, the patient places the mouthpiece in their mouth and breaths in deeply.

– On cue from the technician, they blast out air as fast and completely as possible until no more can be expelled.

– The maneuver may be repeated several times to obtain reproducible results, with at least 3 acceptable flows recorded.

– Key parameters like FVC, FEV1, FEV1/FVC ratio etc. are measured and interpreted against normal standards.

– Post-bronchodilator tests may be done 15-20 minutes later to detect reversibility suggesting bronchospasm.

– The printed report is analyzed by the treating pulmonologist to diagnose any lung function abnormalities.

Advantages and Limitations of Spirometry

Spirometry has some clear advantages but also certain limitations one must be aware of:


– Objective, quantitative and reproducible measurements of lung function
– High sensitivity and specificity for detecting obstructive and restrictive defects
– Non-invasive procedure without radiation exposure
– Inexpensive and widely available testing


– Requires patient effort and coordination which can alter results in elderly or pediatric patients
– Cannot distinguish between small airway vs. large airway disease
– Does not indicate underlying etiology or disease severity in all cases
– Post-bronchodilator testing needed to diagnose reversibility of obstruction
– Normal spirometry does not entirely exclude lung pathology

Spirometer is a simple, non-invasive yet powerful pulmonary function test invaluable for diagnosing and monitoring a wide variety of respiratory diseases from asthma to COPD. When properly performed and interpreted by trained professionals, it provides highly reproducible and quantifiable data on lung volumes and flows for effective management of patients with lung disorders. Spirometry should be more widely incorporated in pulmonary medicine practice to aid early detection and optimal treatment of lung problems.

1. Source: Coherent Market Insights, Public Source, Desk Research
2. We have leveraged AI tools to mine information and compile it