Routine Testing


Spirometry is the measurement of maximal airflow after a deep breath to fill up the lungs. It provides information on the size of the breathing tubes and whether there are any blockages to airflow. This testing requires cooperation that is usually achievable in children 6 years and older.

Spirometry Patient Procedure  (PDF)


Plethysmography is the measurement of lung volume. This information is important for patients suspected of having underdeveloped (hypoplastic) or overinflated lungs, as well as patients with abnormal chest walls. The patient is seated in a large Plexiglas box about the size of a telephone booth. The patient breaths into a mouthpiece and is asked to continue making efforts to breath as a small balloon inflates blocking airflow for 2–3 seconds. This testing requires cooperation that is usually achievable in children 6 years and older.

Diffusing Capacity

The diffusing capacity of the lung is an evaluation of the gas exchange capability which can be abnormal if there is decreased lung tissue surface area, decreased blood vessels in the lung or anemia. The patient takes a single breath of a gas mixture containing a very small amount of carbon monoxide, and holds his or her breath for 10 seconds. The amount of carbon monoxide that disappears during this breath hold is measured. Notify the technician if the patient is anemic or a smoker.

Respiratory Muscle Pressures

A number of different respiratory muscles are required to move gas into and out of the lung. These include the diaphragm and muscles between the ribs, as well as abdominal muscles. There are a number of reasons these muscles can become weak including malnutrition and chronic steroid use. The patient is asked to inhale or exhale strongly against a blocked tube.

Oximetry & Capnography

Oximetry is the measurement of oxygen saturation of the blood. It is a painless, non-invasive test that utilizes a red light shone through a fingertip.  Capnography is the measurement of carbon dioxide in a patient’s breath. It is also a painless test that uses a small cannula in the nose or a tracheostomy tube. This testing requires no cooperation and typically lasts less than a minute.

Exhaled Nitric Oxide

Nitric oxide can be produced by certain lung cells when inflammation is present. Children are asked to breathe quietly into a mouthpiece in an even manner. The nitric oxide concentration is then measured. This testing requires some cooperation to achieve a constant, slow exhalation. This is usually achievable in children 6 years and older.

Exhaled Nitric Oxide Patient Procedure (PDF)