Pulmonary Function Lab

The Pulmonary Function Lab at TMH offers a wide range of pulmonary function testing (lung function) and exercise tests to assist physicians in diagnosing and managing patients with breathing problems and/or lung disease. Pulmonary function tests help measure the different aspects of lung function and can help determine the cause of shortness of breath and may help confirm lung diseases such as asthma, bronchitis or emphysema. The tests are also used to measure how a lung disease in progressing or how serious the lung disease has become. Pulmonary function tests can also be used to assess how a patient is responding to different treatments. Technologists performed more than 5,700 tests in 2011. The total number of outpatients in 2011 was 1,000, and total number of inpatients was 270.

Simple Spirometry

Spirometry is the first and most commonly done lung function test. It measures how much and how quickly you can move air out of your lungs. For this test, you breathe into a mouthpiece attached to a recording device (spirometer). The information collected by the spirometer may be printed out on a chart called a spirogram.

The more common lung function values measured with spirometry are:

  • Forced vital capacity (FVC). This measures the amount of air you can exhale with force after you inhale as deeply as possible.
  • Forced expiratory volume (FEV). This measures the amount of air you can exhale with force in one breath. The amount of air you exhale may be measured at 1 second (FEV1), 2 seconds (FEV2), or 3 seconds (FEV3). FEV1 divided by FVC can also be determined.
  • Forced expiratory flow 25% to 75%. This measures the air flow halfway through an exhale.
  • Peak expiratory flow (PEF). This measures how quickly you can exhale. It is usually measured at the same time as your forced vital capacity (FVC).
  • Maximum voluntary ventilation (MVV). This measures the greatest amount of air you can breathe in and out during one minute.
  • Slow vital capacity (SVC). This measures the amount of air you can slowly exhale after you inhale as deeply as possible.
  • Total lung capacity (TLC). This measures the amount of air in your lungs after you inhale as deeply as possible.
  • Functional residual capacity (FRC). This measures the amount of air in your lungs at the end of a normal exhaled breath.
  • Residual volume (RV). This measures the amount of air in your lungs after you have exhaled completely. It can be done by breathing in helium or nitrogen gas and seeing how much is exhaled.
  • Expiratory reserve volume (ERV). This measures the difference between the amount of air in your lungs after a normal exhale (FRC) and the amount after you exhale with force (RV).

Complex Spirometry

Before and after bronchodilator studies. Premix Albuterol 0.083% is given via nebulizer or as specified by doctor.

Lung Diffusion Capacity (Dlco)

This test measures how well oxygen passes from your lungs to your bloodstream. During this test, you breathe in a type of gas through a tube. You hold your breath for a brief moment and then blow out the gas.

Lung Volumes

Lung volumes provide useful information that confirms the presence of restrictive lung disease suggested by a low vital capacity on a spirometry test.

Lung volume measurement can be performed in two ways:

  • The most accurate way is for a person to sit in a body plethysmography, a sealed, transparent box that resembles a telephone booth, while breathing in and out against into a mouthpiece. Changes in pressure inside the box allow determination of the lung volume.
  • Lung volume can also be measured when a person breathes nitrogen gas through a tube for a specified period of time. The concentration of the gas in a chamber attached to the tube is measured, allowing estimation of the lung volume.

Arterial Blood Gases

An arterial blood gas (ABG) test measures the acidity and the levels of oxygen and carbon dioxide in the blood from an artery. This test is used to check how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.

Blood for an ABG test is taken from an artery. Most other blood tests are done on a sample of blood taken from a vein, after the blood has already passed through the body's tissues where the oxygen is used up and carbon dioxide is produced.

Pulse Oximetry - SpO2

Pulse oximetry and arterial blood gas tests show how much oxygen is in your blood. During pulse oximetry, a small sensor is attached to your finger or ear. The sensor uses light to estimate how much oxygen is in your blood. This test is painless and no needles are used.

Maximal Inspiratory Pressure/Maximal Expiratory Pressure (MIP/MEP) 

This is a test of total respiratory muscle strength.  In one part of the test, you are asked to attempt to inhale as forcefully as possible against a blocked tube.  In the other part of the test, you are asked to attempt to exhale as forcefully as possible against a blocked tube.  In both cases, the pressure you generate while attempting to inhale or exhale is recorded.  This pressure is correlated with the overall strength of the breathing muscles and may be helpful in assessing possible respiratory muscle weakness.

Exercise Challenge Testing 

Our lab performs several types of exercise testing consisting of baseline spirometry, a period of vigorous exercise, and repeat spirometry at defined intervals.

Airway Resistance (Raw/Gaw) 

Airway resistance can be directly measured during Body Plethysmography, which determines the pressure required to produce a given flow. For this test, you sit in a “booth” and breathe through a mouthpiece while pressure and airflow measurements are collected.

Preparation for Pulmonary Function Tests

Prior to your pulmonary function test, do not eat a heavy meal and, if you are a smoker, do not smoke for four to six hours prior to the test. Specific instructions will be given if bronchodilators or inhaler medications should be withheld. Sometimes, medications will be inhaled prior to the tests.

For more information about pulmonary function tests at TMH, call 850-431-5757.