Pulmonary Laboratory

The pulmonary laboratory technicians at Seton Medical Center perform pulmonary tests to detect and measure abnormalities in respiratory function, and quantify the severity of various lung diseases.

Such tests include:

Measurements of lung volumes

Ventilatory function

Diffusing capacity

Gas exchange

Lung compliance

Airway resistance

Distribution of gasses in the lung

Ventilatory studies (spirometry) are the most common tests, typically following these steps:

1. Requires water spirometer, electronic spirometer, or wedge spirometer that plots volume against time (timed vital capacity).

2. Patient is asked to take as deep a breath as possible and then to exhale into the spirometer as completely and as forcefully as possible.

3. Results are compared with norms for patient’s age, height and gender.

4. A reduction in several parameters usually indicates an obstructive flow due to bronchial obstruction or loss of lung elastic recoil.

5. A reduction in the vital capacity alone may indicate a restrictive form of lung disease (disease due to increased lung stiffness).

Lung volumes are determined by asking the patient to inhale a known concentration of inert gas, such as helium or 100% oxygen, and measuring the concentration of inert gas or nitrogen in exhaled air (dilution method) or by plethysmography.

1. Yields thoracic volume (total lung capacity), plus any unventilated blebs or bullae.

2. An increased residual volume is found in air-trapping due to obstructive lung disease.

3. A reduction in several parameters usually indicates a restrictive form of lung disease or chest wall abnormality.

Diffusing capacity measures lung surface for the transfer of gas in the lung. This is done by having the patient inhale gas containing known low concentration of carbon monoxide and measuring carbon monoxide concentration in exhaled air. The difference between inhaled and exhaled concentration is related directly to the uptake of carbon monoxide across the alveolar-capillary membrane and is reduced in parenchymal lung disease, possibly in severe anemia and in some forms of heart disease.

At Seton Medical Center, where Experience Counts^sm, we look forward to providing these services to you and your family with both care and compassion.