01.12 Pulmonary Function Test

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Included In This Lesson

Study Tools



  1. Pulmonary function tests
    1. How well lungs are working
    2. Lung volume
    3. Inspiratory & expiratory pressure
    4. Blood gases

Nursing Points


  1. Pulmonary function tests
    1. Spirometry
      1. Amount of air lungs can hold (volume)
      2. Inspiratory and expiratory pressure
      3. Diagnose restrictive lung disease
      4. Methacholine challenge testing
        1. Irritant to create bronchospasm (asthma)
        2. Shows airway hyperactivity with spirometer
    2. Pulse oximetry
      1. Blood oxygen level
      2. O2 walk -> pulse ox while ambulating
    3. Arterial blood gas (ABG)
      1. O2 & CO2 levels
      2. Acid base
    4. Fractional exhaled nitric oxide tests
      1. Shows airway inflammation (asthma)
    5. Cardiopulmonary stress test
      1. Exercise
      2. Lungs and heart assessed during
  2. Purpose
    1. Assess lung function
    2. Determine oxygen needs & treatment
  3. Indications
    1. Shortness of breath
    2. Low O2 levels
    3. Diminished breath sounds
    4. Wheezing
    5. Confusion (ABGs)


  1. Before
    1. Explain test to patient
    2. Stress test
      1. NPO midnight
      2. No caffeine day before
    3. Nitric oxide test
      1. NPO for 1 hour
      2. Avoid for 24 hours previous
        1. Exercise
        2. Alcohol
        3. Tobacco
        4. Allergy shots

Therapeutic Management

  1. During
    1. Pulse oximeter -> place finger probe on patient
    2. Spirometer -> patient breathes into device (inhale and exhale)
    3. Nitric oxide test -> patient breathes into mountpeice of machine
    4. Methacholine challenge test -> prepare drug for patient to inhale
    5. ABGs
      1. Needle and syringe
      2. Feel for pulse in wrist
      3. Poke where pulse is felt (artery)
      4. Send to lab immediately
    6. Cardiopulmonary stress test
      1. Patient on exercise bike – about 12 minutes
      2. Pulmonary testing before, during, after

Nursing Concepts

  1. Acid-base balance -> breathing affects acid-base balance in blood
  2. Gas exchange -> lung testing
  3. Oxygenation -> lung testing

Patient Education

  1. Doctor will provide results
  2. Resume diet after


Hey guys! Welcome to the lesson on pulmonary function tests!

The pulmonary function tests are done on patients to assess their lung function and need for oxygen or other treatment like a bipap or breathing treatments. They help to assess the patient’s lung volume, or how much air they can fit in their lungs on inhale. Inspiratory and expiratory pressures are measured. Oxygen levels show how much oxygen is available in the blood for the tissues to use. Whenever any of the following tests are ordered, you will explain the test to the patient first. Let’s talk about why these tests might be ordered. 

Pulmonary function tests may be ordered if the patient is having any problems breathing like shortness of breath, low oxygen levels, wheezing, or diminished breath sounds. Confusion is also a symptom that may indicate lung testing because if the patient has a high PCO2 level, meaning too much carbon dioxide in the arterial blood supplying the body, they will be confused from the lack of oxygen reaching the brain. Let’s explore the different tests. 

The spirometry device is used to test lung volume and pressure to help diagnose restrictive lung diseases. The patient blows into this device and it measures the values. The methacholine challenge test is done by providing an irritant for the patient to breath in that causes a bronchospasm to show if the airway is hyperactive. The spirometry device is used after, and if the results are decreased then the patient might be diagnosed with asthma. or reactive airway disease. If the patient is reacting very poorly, you may need to provide a breathing treatment to help open up the lungs after. 

Pulse oximetry is a device that reads the blood oxygen level. To use this device, you place a finger probe on the patient like in this picture. There are continuous pulse ox devices and spot check devices. A doctor might order an O2 walk before a patient is discharged if they’ve been on oxygen in the hospital but don’t wear it at home. During this test, you or the respiratory therapist will bring a spot check pulse ox and keep it on the patient while walking with oxygen. The oxygen will be removed and you will monitor the patient’s pulse ox number. If it drops, the patient might need oxygen at home for activity. Chart the results for the doctor to see. 

Arterial blood gas or ABGs are ordered to view the arterial blood oxygen level, carbon dioxide level, and acid balance. ABGs are notoriously ordered on patients that have COPD, especially if they are showing confusion or lethargy. Remember, the arteries provide oxygen to the brain, so with low O2 and high CO2 in the arterial blood, the brain is not being oxygenated like it needs to be. If the ABGs are poor results, call the doctor right away as they will probably order a bipap for the patient to assist with breathing and CO2 exhalation. The acid base levels like bicarb and PH will help the doctor to see if the patient is compensating or not with their breathing. To perform this lab draw on the patient, you will feel for their pulse in the wrist and poke straight down into the wrist into the artery to draw blood. Hold pressure for a few minutes after to stop the bleeding. Keep the vial of blood collected moving around until you are able to immediately send it down to lab to prevent clotting.

The fractional exhaled nitric oxide test is used to show airway inflammation. Before this test, the patient will need to be NPO for at least an hour. They have to avoid exercise, alcohol, tobacco, and allergy shots for at least 24 hours before the test is performed. During the test, the patient exhales into a mouthpiece of a machine like this that measures the nitric oxide. Nitric oxide is made in the lungs when inflammation and tightness occurs, so high levels may indicate asthma. A positive nitric oxide test may cause the doctor to order steroid inhalers. 

The cardiopulmonary stress test is where the lung function tests are performed during exercise. The patient may be on an exercise bike for about 12 minutes and the tests are completed before, during, and after to assess the difference in functioning. 

The priority nursing concepts for the patient with pulmonary function tests are acid-base balance, gas exchange, and oxygenation. 

Alright guys, let’s review the most important points. Pulmonary function tests are used to assess the lung function in our patients by assessing volume, inspiratory and expiratory pressure, and blood gas levels to help diagnose and treatment decisions. Lung tests may be ordered if the patient is short of breath, wheezing, confused, or lethargic. The pulse oximetry device uses a finger probe to check the blood oxygen level. ABGs are drawn from the artery to view the arterial oxygen, carbon dioxide, and acid base balance levels. Spirometers are used to assess the lung volume and pressure. Methacholine challenge, nitric oxide, and cardiopulmonary stress testing may also be used to assess the patient’s lung function.   

Okay guys, that’s it on the pulmonary function tests! Now go out and be your best self today, and as always, happy nursing!