Lungs

Lungs are a pair of spongy, air-filled organs located in the thoracic cavity, responsible for gas exchange between the air we breathe and the bloodstream. The lungs are divided into lobes; the right lung has three lobes (superior, middle, and inferior), while the left lung has two lobes (superior and inferior) to accommodate the heart. The lungs are protected by the rib cage and are connected to the trachea (windpipe) via the bronchi. The bronchi further divide into smaller branches called bronchioles, which eventually lead to tiny air sacs called alveoli. The alveoli are the primary sites of gas exchange, where oxygen from the inhaled air diffuses into the bloodstream, and carbon dioxide from the blood diffuses into the alveoli to be exhaled. The lungs are surrounded by a thin membrane called the pleura, which helps reduce friction during breathing movements. The lungs receive blood supply from the pulmonary arteries, which carry deoxygenated blood from the heart to the lungs, and the pulmonary veins, which return oxygenated blood back to the heart. The lungs also have a rich network of lymphatic vessels and nerves that help regulate their function.

Spirometry is a common pulmonary function test that measures lung function, specifically the volume and flow of air that can be inhaled and exhaled. It is used to diagnose and monitor respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other disorders that affect breathing. During a spirometry test, the patient takes a deep breath and exhales forcefully into a device called a spirometer. The spirometer records the amount of air exhaled and the speed of the exhalation. Key measurements obtained from spirometry include:

Forced Vital Capacity (FVC): The total volume of air that can be forcefully exhaled after taking a deep breath.
Forced Expiratory Volume in 1 second (FEV1):The volume of air that can be forcefully exhaled in the first second of the FVC maneuver.
FEV1/FVC Ratio: The ratio of FEV1 to FVC, expressed as a percentage. This ratio helps to differentiate between obstructive and restrictive lung diseases.
Peak Expiratory Flow (PEF): The maximum speed of exhalation during the FVC maneuver.

Spirometry results are typically compared to predicted values based on the patient's age, gender, height, and ethnicity. Abnormal spirometry results can indicate the presence of respiratory conditions:

Obstructive Lung Diseases: reduced FEV1 and a decreased FEV1/FVC ratio, indicating airflow obstruction. For example, asthma and COPD.
Restrictive Lung Diseases: reduced FVC with a normal or increased FEV1/FVC ratio, indicating restricted lung expansion. For example, pulmonary fibrosis and sarcoidosis

Spirometry is a valuable tool for assessing lung function, guiding treatment decisions, and monitoring disease progression in patients with respiratory conditions.