Understanding Pulmonary Function: Tests and Regulation

Posted on Feb 6, 2025 in Biology

Pulmonary Function

The breathing mechanism aims to provide an uninterrupted flow of oxygen from the environment to cells.

To carry out this function, the lungs, blood, and mitochondria work together.

The lung is the gas exchange organ, the blood carries oxygen to tissues, and mitochondria enable its use.

The speed and depth of breathing are controlled by involuntary processes in the brainstem.

In each inhalation and exhalation, more than half a liter of air is exchanged.

Respiratory function can be divided into seven interrelated components:

1. Ventilation: Inspired air reaches the alveoli, and alveolar air enters the atmosphere.
2. Diffusion: Gases flow through the alveolar walls.
3. Perfusion: Blood withdraws carbon dioxide from the lung and releases oxygen into it.
4. Ventilation-Perfusion Balance: Ventilation and blood flow are balanced between lung regions for proper gas exchange.
5. Gas Transport: Oxygen and carbon dioxide are transported in the blood to and from tissues.
6. Mechanics of Breathing: Muscles, elastic properties, and resistance move the lung and chest wall.
7. Control of Ventilation: Mechanisms regulate gas exchange.

Pulmonary Function Testing

What are the indications for pulmonary function tests?

Pulmonary function tests are aimed at:

1. Detecting the presence or absence of lung disease.
2. Quantifying the extent of lung function impairment.
3. Determining treatment effect.
4. Measuring the effect of occupational or environmental exposure.
5. Assessing pulmonary disability.
6. Preoperative evaluation for lung resection surgery.
7. Preoperative anesthetic risk evaluation and/or surgical risk.
8. Differential diagnosis of dyspnea and exercise intolerance.

Each of these components can be evaluated objectively and quantifiably through pulmonary function studies.

How to Classify Pulmonary Function Studies

Pulmonary function tests assess the degree and type of respiratory system dysfunction. They can be classified as follows:

1. Tests exploring respiratory function.
2. Tests that measure gas exchange.
3. Evidence to assess the respiratory system to various stimuli or situations.

Spirometry is a widely used lung function measurement, using a spirometer to measure inhaled or exhaled air.

Other lung function studies include the determination of static lung volumes, diffusing capacity for carbon monoxide, and arterial blood gases.

It is important to note that respiratory symptoms usually develop only under certain situations such as stress and sleep.

Regulation of Breathing

The breathing regulator is located in the medulla, where it regulates inhalation and exhalation.

The pneumotaxic center controls the process of exhalation.

The pleura are the regulators that are pressure receptors inside the lungs.

The pleura is divided into:

• External or parietal pleura
• Middle pleura where the pleural fluid has a negative pressure.
• Interstitial or visceral pleura.

The role of the pleura is to protect against rubbing against the ribs and from impacts.