FeNO, Timed Walk Testing & Exercise Oxygen Titration

Objectives - Review indications and results for FeNO testing; perform a timed walk test; and perform oxygen titration with exercise.

---

Exhaled Nitric Oxide

Definition

Exhaled gas contains trace amounts of nitric oxide (NO).

As airway inflammation worsens, the fractional exhaled nitric oxide (FeNO) in breath increases. This makes FeNO a marker of airway inflammation.

FeNO is measured in parts per billion, or ppb.

Indications

FeNO may be used to:

• Diagnose airway inflammation
• Establish a baseline while stable for known asthmatics
• Determine likely response to corticosteroid treatment
• Guide changes in corticosteroid dose
• Monitor patients
• Monitor adherence to anti-inflammatory medications, including corticosteroids

Relative Contraindications and Pre-Test Factors

When possible, patients should refrain from eating and drinking for 1 hour before exhaled NO measurement.

Several factors can alter FeNO:

There are no currently known hazards.

Equipment

Equipment includes:

• Exhaled nitric oxide device
• Mouthpiece and filter
• Nose clip

Procedure

Always perform FeNO measurement before spirometry or other PFTs.

ATS has no standards for acceptability or reproducibility of FeNO measurement in the provided source. Follow the manufacturer's recommendation for the procedure.

---

FeNO Values

Adults

Children

---

Timed Walk Test

Definition

The timed walk test determines the physical capability of patients with pulmonary disease.

It measures the distance a patient can walk on a flat, hard surface in 6 minutes and reflects an individual's ability to perform daily physical activities.

Indications

The timed walk test can provide a single measurement of functional status for:

• COPD
• Cystic fibrosis
• CHF
• Pulmonary vascular disease
• Elderly patients

Equipment

Equipment includes:

• Minimum of 30 meters or 100 feet of clear hallway
• Marked turnaround point, such as a cone or tape
• Course marked every 10 feet
• Stopwatch
• Rate of perceived exertion scale, using the Modified Borg scale
• Portable oxygen with nasal cannula
• Handheld pulse oximeter, optional

Pre-Procedure

Before the timed walk:

• Patient should wear clothing and shoes comfortable for walking
• Patient may use walking aids, such as a cane or walker
• Patient should take medications as prescribed, including oxygen
• Patient may eat a light meal before early morning or early afternoon tests
• Patient should not exercise vigorously within 2 hours of the test
• Have the patient sit in a chair for 10 minutes before walking
• Obtain baseline BP, SpO2, and HR
• Have the patient stand and rate perceived exertion using the Borg scale

---

Timed Walk Procedure

The objective is to walk as far as possible for 6 minutes.

During the test:

• Patient follows the predetermined course and walks at their own pace
• Patient may slow down or take breaks as needed, but time continues to run
• If the patient stops to rest, document the duration and ask for RPE
• Be encouraging and give time hacks
• When time expires, tell the patient to stop
• Calculate the distance by walking to the patient
• Ask the patient to report RPE using the Borg scale

If the patient is on supplemental O2:

• Patient must carry their own gas source
• Patient should be on ordered flow settings
• Technicians should not walk with the patient
• Even walking behind the patient can affect pace

When testing very deconditioned patients, have a chair available along the course or follow with a wheelchair.

---

Timed Walk Values & Interpretation

There are currently no valid reference sets, so there are no "normal" values for interpreting a single 6-minute walk measurement.

Small studies have shown:

• Healthy men average around 1800 feet
• Healthy women average around 1500 feet

Most 6-minute walk tests are performed before and after an intervention. The difference is reported as an absolute value, such as:

The patient walked 300 feet further post pulmonary rehab.

Interpretation points:

• A change distance of more than 150 feet is clinically significant in most disease states.
• Distances less than 1000 feet are associated with increased mortality in COPD, CHF, and pulmonary arterial hypertension.

---

Oxygen Titration with Exercise

Definition

Oxygen titration with exercise is performed to determine the degree of oxygen desaturation and/or hypoxemia that occurs on exertion.

Indications

Oxygen titration with exercise may be used to:

• Assess and quantify the adequacy of arterial oxyhemoglobin saturation during exercise in patients suspected of desaturation
• Evaluate dyspnea on exertion
• Evaluate decreased DLCO
• Evaluate decreased PaO2 at rest
• Evaluate known pulmonary disease
• Titrate supplemental O2 to treat hypoxemia or desaturation during activity
• Perform pre-operative assessment for lung resection or transplant
• Assess degree of impairment for disability evaluation, such as pneumoconiosis or asbestosis

Contraindications

Relative Contraindications

• Invalid pulse oximetry, such as COHb or decreased perfusion
• Severe pulmonary hypertension
• Resting diastolic BP greater than 110 torr
• Resting systolic BP greater than 200 torr
• SaO2 or SpO2 less than 85% on room air
• Inability to cooperate or follow directions

Absolute Contraindications

• Acute ischemia or serious cardiac dysrhythmias
• Unstable angina
• Recent MI within 4 weeks
• Uncontrolled hypertension
• Uncontrolled or untreated asthma
• Pulmonary edema

---

Oxygen Titration Hazards

Hazards include:

• Severe desaturation, indicated by SaO2 less than or equal to 80% or SpO2 less than or equal to 83%
• A 10% fall from baseline values
• Angina
• Hypotensive responses
• Decrease of more than 20 torr in systolic pressure after the normal exercise rise
• Decrease in systolic blood pressure below the pre-exercise level
• Lightheadedness
• Patient request to terminate the test

Exercise may need to be discontinued for abnormal responses, including:

• Rise in systolic blood pressure to greater than 250 torr
• Rise in diastolic pressure to greater than 120 torr
• Rise in systolic pressure of less than 20 torr from resting level
• Mental confusion or headache
• Cyanosis
• Nausea or vomiting
• Muscle cramping

Equipment

Equipment may include:

• Treadmill, cycle ergometer, or arm crank ergometer
• Other exercise methods, such as stair climbing, step test, or timed walking
• Pulse oximeter with ear, forehead, or finger probe
• Portable oxygen with nasal cannula
• ABG sampling equipment
• EKG monitor
• Code cart
• Borg scale

---

Oxygen Titration Procedure

Begin by obtaining baseline:

• Blood pressure
• Oxygen saturation
• Heart rate
• RPE

Place the pulse oximeter on continuous monitoring and use a paper strip to record HR and SpO2 throughout the test.

Room Air Testing

When testing a patient on room air:

• If SpO2 drops below 85%, stop the patient.
• Have the patient recover before continuing.
• The doctor may want the test repeated with the patient on oxygen to determine the O2 level needed.

Oxygen Testing

When testing a patient on oxygen:

• If SpO2 drops below 88%, increase oxygen by 1-2 L at a time.
• Do not cause the patient to slow down.
• Maintain O2 saturation greater than or equal to 89%.

During the test:

• Use encouragement such as "you're doing well" and "good job."
• Tell the patient when 2, 4, and 6 minutes have elapsed.

Accurate evaluation of desaturation on exertion requires analysis of arterial blood samples drawn with the subject at rest and at peak exercise.

SpO2 of 93% should be used as a target.

Continuous arterial saturation measurement by pulse oximetry can provide qualitative information and an approximation of oxyhemoglobin saturation. A 4% decrease in SpO2 is considered significant.

---

Review

High-yield points:

• FeNO increases as airway inflammation worsens and is measured in ppb.
• FeNO should be performed before spirometry or other PFTs.
• Adult FeNO greater than 50 ppb suggests eosinophilic inflammation is likely, and corticosteroid responsiveness is likely in symptomatic patients.
• The timed walk test measures distance walked in 6 minutes on a flat, hard surface.
• During a timed walk, the patient may stop to rest, but time continues.
• Oxygen titration with exercise determines desaturation or hypoxemia that occurs on exertion.
• On room air, stop the patient if SpO2 drops below 85%.
• On oxygen, increase O2 by 1-2 L if SpO2 drops below 88%, with a goal of at least 89%.