Specialized Pulmonary Function Studies

Hypoxic and Hypercapnic Drive Response 
Pharyngometry
Rhinometry
Exhaled Nitric Oxide

Hypoxic and Hypercapnic Drive Response

These test measure the patient’s response to not getting enough oxygen (hypoxic) or of getting too much carbon dioxide(CO2)(hypercapnic). Minute ventilation and occlusion pressures are used to measure response in hypoxic and hypercapnic response. Hypoxic response is a measure of the change in breathing patterns associated with decreases in inspired O2 concentration while end-tidal CO2 is stabilized. Hypercapnic response is a measure of the change in breathing patterns associated with increases in inspired CO2 concentration when oxygenation is adequate.

Performing the test

1. You will sit while on a mouthpiece with noseclips on and breathe until the end of the test approximately 8 to 12 minutes
2. You will wear a pulse oximeter on your finger to monitor your oxygen saturation level
3. You may listen to music or watch a video during the test
4. A technologist will instruct you on how to perform the test and will monitor you throughout the test

Patient breathing on the mouthpiece for a hypoxic drive response test.

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Pharyngometry

Acoustic pharyngometry is used for the assessment of the area of the oral and pharyngeal spaces down to the larynx. Use of sound echoes to measure the geometry of the oral and pharyngeal cavities. May be used for the non-invasive assessment of the upper airways, evaluation of patients with obstructive sleep apnea, and changes induced due to provocation.

Performing the test

1. You will sit in a chair and hold a wand with a mouthpiece on it.
2. You will place the mouthpiece in your mouth and do various breathing on the mouthpiece as instructed by the technologist.
3. Breathing through the mouth normally for 10 to 12 seconds
4. Breathing through the nose for 10 to 12 seconds.
5. Closing your glottis and exhaling.
6. Closing your glottis and inhaling.
7. A technologist will instruct you on how to perform the test and coach and encourage you to do your best.

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Rhinometry

Acoustic rhinometry is a procedure that uses sound echoes to measure the geometry of the nasal cavity. These measurements define patency to airflow, the effectiveness of mucosal therapies and the evaluation of mucosal responses to airborne irritants.

Performing the test

1. You will sit across from a pulmonary technologist as they hold the rhinometer, a tube up to your nostril.
2. You will breathe normally while the technologist makes sure there is a good seal around your nostril.
3. They will ask you to pause breathing on the count of three.
4. After 3 or 4 seconds you will be told to breathe normally again.
5. At least 4 reproducible efforts will be done for each nostril.
6. You may be given a nasal spray or exposed to an irritant and asked to repeat the test.

Patient’s nasal cavity being measured with the rhinometer.

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Exhaled Nitric Oxide

This test measures the amount of nitric oxide in your respiratory system. An excessive amount of nitric oxide in the respiratory system may indicate airway inflammation. This is a noninvasive easy method of measuring airway inflammation. A technologist will instruct you on how to perform the test and coach and encourage you to do your best.

Performing the test

1. You will be asked to blow out all of your air until you are empty.
2. You will then place the mouthpiece in your mouth and take a maximum breath in until your lungs are completely filled.
3. You will then blow out at a constant rate (less forcefully than spirometry) for approximately 10 seconds.
4. Visual aides assist you in blowing out at the correct rate.
5. The test is repeated until there are three reproducible measurements.

Learn more about the best way to prepare for an exhaled nitric oxide test .

Young patient preparing to do exhaled nitric oxide test.

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