Fall/Winter 2018 Diagnostics Bulletin

Fall/Winter 2018 Diagnostics Section Bulletin

Jennifer Weltz Horpedahl, BSRT, RRT, RRT-NPS, RPFT, AE-C

Kadlec Regional Medical Center
Benton City, WA
Email: jennifer.weltz-horpedahl@kadlec.org

D’Aun Flesher, BSRT, RRT-NPS, AE-C
Presbyterian Healthcare Services
Albuquerque, MN
Email: dflesher@phs.org

In this issue:

How Much Should You Rely on Pulse Oximetry?

Jeffrey Haynes, RRT, RPFT, FAARC

Increasingly, venous blood gases (VBG) are being chosen over arterial blood gases (ABG). The rationale is that the venous pH and carbon dioxide pressure (PCO2) are clinically comparable to arterial, and the venous sample is less painful for the patient. However, numerous studies have shown that the average pain from an arterial puncture is 3/10 on a visual analog scale.1-3 If a bag of ice is applied for three minutes prior to puncture, the average pain is reduced to 1.5/10 on a visual analog scale.3

When VBGs are ordered, the assessment of oxygenation becomes reliant on pulse oximetry. While there are known sources of erroneous SpO2 signals (e.g. motion artifact, optical shunting, poor perfusion), SpO2 can be inaccurate even under ideal conditions. The following is an example of ABG-SpO2 discordance encountered in a PFT laboratory.

Case overview

An 86-year-old female with COPD presented for an outpatient PFT with room air ABG. The ABG sample was drawn without difficulty:

pH 7.43
PaCO2 34
PaO2 54
O2Hb 87%

Pulse oximetry was performed in preparation for O2 titration. The probe completely covered the fingertip and there was a good SpO2 signal and perfusion index. The probe was turned 90 degrees to avoid the influence of nail polish as described by Chan et al.4 The resting RA SpO2 was ~95%. There was no reason to suspect leukocyte larceny.5

A second RA ABG was drawn to confirm that the first sample was purely arterial:

pH 7.41
PaCO2 34
PaO2 55
O2Hb 88%

This sample was also analyzed with a second ABG analyzer:

pH 7.41
PaCO2 35
PaO2 56
SaO2 89%

The RA SpO2 at the time of puncture was still ~95%.

The patient was started on home oxygen therapy based on the data obtained from ABG analysis. If pulse oximetry was relied upon to assess oxygenation, this patient would have been sent home hypoxemic at rest. Because of the patient’s COPD and low diffusing capacity, deeper oxygen desaturations during sleep and exercise would be expected.

Pulse oximetry is an important tool for trending oxygenation, but performs inferiorly to ABG analysis when the presence or absence of hypoxemia must be determined. In this case pulse oximetry reported a false negative result without any identifiable source of error. Spurious pulse oximetry is more common than most clinicians may think. Figure 1 shows a comparison of SpO2 and PaO2 in 2599 patients.6

image of graph for article
Figure 1. Pulse oximetry versus PaO2 in 2599 patients breathing room air. From Reference 6.


  1. Giner J, Casan P, Belda J, Gaonzález M, Miralda RM, Sanchis J. Pain during arterial puncture. Chest 1996;110(6);1443-1445.
  2. France JE, Beech FJ, Jakeman N, Benger JR. Anaesthesia for arterial puncture in the emergency department: a randomized trial of subcutaneous lidocaine, ethyl chloride or nothing. Eur J Emerg Med 2008;15(4):218-220.
  3. Haynes JM. Randomized controlled trial of cryoanalgesia (ice bag) to reduce pain associated with arterial puncture. Respir Care 2015;60(1):1-5.
  4. Chan MM, Chan MM, Chan ED. What is the effect of fingernail polish on pulse oximetry? Chest 2003;123(6):2163-2164.
  5. Haynes JM. A case of disparity between pulse oximetry measurements and blood gas analysis values. Respir Care 2004;49(9):1059-1060.
  6. Pichurko BM. Exercising your patient: which test(s) and when? Respir Care 2012;57(1):100-110.


Syncope and Near-syncope Secondary to Forced Spirometry

Kevin McCarthy, RPFT

While forced spirometry is generally considered to be a safe test, anyone that administers the test knows that syncope can occur during a forced spirometry testing session. The person administering the test is responsible for terminating the forced exhalation if there is any indication that the patient is not tolerating the procedure.

Awareness of how the patient is tolerating the procedure requires that the operator be periodically looking at the patient for signs of syncope or near-syncope. Patients should be instructed before starting to keep their body upright, chin slightly elevated, and eyes open and focused on the junction of the wall and the ceiling.

Operators should be positioned so that they can quickly shift their gaze from the patient’s face to the testing screen and back again throughout the entire effort, with most of their attention on the patient’s face. Periodic attention should be given to the volume-time tracing on the display screen of the pulmonary function system to check for the presence of an expiratory plateau sustained for two seconds, as this is an immediate cause to terminate the expiratory effort.

It is quite common for patients with moderate or severe airway obstruction to fail to demonstrate an expiratory plateau. In that circumstance, the recommendation is to terminate the expiration at 15 seconds.

Symptoms to look for

The forced exhalation of spirometry has the same hemodynamic effect of a Valsalva maneuver. The forceful contraction of expiratory muscles rapidly raises the pleural pressure to a peak of 80 mmHg (100 cmH2O). Pleural pressure is sustained at 50-70 mmHg (70-95 cm H2O) for the majority of the effort.

Such a high intrathoracic pressure impedes venous return, and cardiac output falls as a consequence. Occasionally, near-syncope will occur; eyelids flutter or the eyes roll upward, displaying only the whites of the lower eyeball. When the maneuver is stopped at that point, patients often don’t immediately respond and appear to be struggling for a few seconds to determine where they are and what is happening.

Less frequent are patients who experience frank syncope; eyes closing as they slump downward or forward in the chair, unresponsive. Some patients may arrive for testing dehydrated and hypotensive from fasting for other diagnostic procedures. Diuretics, beta-blockers, and anti-hypertensive drugs may also cause hypotension that would predispose the patient to fainting during the forced exhalation.

Recovery is usually quick

Fortunately, most patients experiencing near-syncope during a forced exhalation recover rapidly. The maneuver should be terminated and the patient should be told to inhale deeply. The patient’s response to this helps with the assessment of syncope.

Hemodynamics should begin to return to normal within a few seconds. Patients who do not respond should be safely removed from the chair and placed face up on the floor. Assess whether the patient is breathing and, if so, elevate the legs about 12 inches to restore blood flow to the brain. Loosen belts, ties, and restrictive clothing and begin taking vital signs (blood pressure, heart rate, and SpO2).

If the patient has not responded at this point, immediately call for a medical emergency response team. Remember that while this appears to be syncope, it may be a stroke. The good news is, calling for help is usually not necessary, as most patients experiencing syncope from spirometry testing recover quickly. Indeed, most patients respond almost immediately, and moving the patient from the chair to the floor is a rare event.

However, while recovery from near-syncope events is typically rapid, each situation is unique to the patient and should never be taken lightly. Such reactions to testing are clearly undesirable and can be taken as evidence that the subject has been pushed too far. The laboratory medical director or designee should determine whether testing should be continued. The patient will be evaluated and the medical record reviewed to determine the safety of continued testing.

Our experiences

A case report by Boerrigter et al. of a patient with severe airway obstruction doing a forced exhalation while attached to a variety of hemodynamic monitors showed systolic blood pressure beginning to fall just a couple of seconds into the forced exhalation.1 The patient maintained a forceful exhalation for just over seven seconds, at which time the systolic blood pressure fell from 150/80 mmHg to approximately 80/50 mmHg when the expiratory effort was terminated. The blood pressure rose to pre-effort levels within a few seconds of terminating the effort. Boerrigter portrayed the event as a “hemodynamic roller coaster.”

Once the FEV1 has been measured, the continuation of the FVC maneuver is mainly to obtain the best quality FVC. In most patients, regardless of the presence or absence of airway disease, flow falls to 0.1-0.2 LPS by four seconds into the forced exhalation.3 At this point, flow is relatively effort independent, being more dependent on the diameters of the peripheral airways and less dependent on driving force.

We reasoned that if a patient could reduce the “push” from a maximum level to a more moderate level, flow would continue with lessened negative consequences of impeded venous return and reduced cardiac output. We compared the effect of reducing the expiratory effort at four seconds into the forced exhalation to the standard method of pushing as hard as possible for the entire effort. In the pre-test instructions we told the subjects to push as hard as they possibly could until they heard me say, “Relax and push gently, do not stop, do not inhale; gently squeeze your abdominal muscles.”

We showed that in patients with moderate to severe obstructive airway disease this technique resulted in significantly longer expiratory times and “FVCs.”3 It should be noted that this was not considered to be “true forced spirometry” by the ATS Spirometry Task Force of 20052 and is not being recommended here. I bring it up because it does provide insight into how to make spirometry safer. After we adopted this in our laboratories, the incidence of spirometry-associated syncope fell to zero and stayed there for 20 years.

Coaching counts

Therapists can modify the patient’s expiratory effort with their coaching in an effort to keep the procedure safe. Generally, coaching the patient to “gently squeeze your belly muscles” will result in a gentle sustained push required to allow continued accumulation of volume. Remembering that the ATS says that exhalation time >15 seconds rarely provides information that will change clinical decisions2, it is reasonable to consider a forced expiratory time (FET) of 15s as both a goal and an endpoint in patients who fail to demonstrate an expiratory plateau. Including a countdown of the time remaining to that endpoint in the coaching (e.g., “you’re doing great…. eight more seconds…. gently squeeze the belly…. five more seconds…” etc.) is a way to provide encouragement that results in the sustained push needed to continue accumulation of volume without the patient bearing down with maximum effort.

My personal observation is that experienced techs, without adopting a standardized modification of effort, often coach in a manner that results in less than maximal push as the effort draws to a close. My belief is that some patients do this without the therapist being aware of it. You can spot them; they don’t turn purple during their forced exhalation.


  1. Boerrigter BG, Bogaard HJ, Vonk-Noordegraaf A. Spirometry in chronic obstructive pulmonary disease; a hemodynamic roller coaster? Am J Respir Crit Care Med 2012; 186(4):e6-e7, Aug 15, 2012.
  2. Miller MR, Hankinson J, Brusasco V, Burgos F, Casaburi R, Coates A, Crapo R, Enright P, van der Grinten CPM, Gustafsson P, Jensen R, Johnson DC, MacIntyre N, McKay R, Navajas D, Pedersen OF, Pellegrino R, Viegi G, Wanger J. ATS/ERS Task Force: standardisation of spirometry. Eur Respir J 2005;26:319-338.
  3. Stoller JK, Basheda S, Laskowski D, Goormastic M, McCarthy K. Trial of standard versus modified spirometry to achieve end-of-test spirometry criteria. Am Rev Respir Dis 1993;148(2):275-280.

The Role I Play in Stem Cell Research

Jessica Thomson, RRT

Like most unique opportunities that have happened in my life, it was by chance that I started working with stem cells. In February of 2017, a Post-It note appeared in the RT department at the hospital I was working at that stated a physician was looking for someone to do PFTs for him. I called the number and talked to the office manager, and within a week I was hired.

All I really knew about the position was that I would be doing PFTs pre- and post-stem cell treatment on COPD patients. At this time, I didn’t know anything about stem cells or their use in medicine, but it sounded interesting, so I jumped on board.

Getting started

When I started working with Daniel Vanos, MD, at Stem Cell Solutions NW, the treatment protocol for COPD patients was minimal. Patients would fill out a St. George’s questionnaire about their symptoms, complete a pre-treatment PFT and 6-minute walk test, and then talk to the case manager and decide if they wanted to purchase the stem cell treatments for their COPD. If they decided to purchase the treatments, they would receive their first treatment that day via nebulizer and IV.

At the time patients were getting four unit doses of stem cells (each unit dose is .25cc) — one unit in the nebulizer and three in the IV. Two to three months later, the patient would return for a second treatment of two unit doses, one in the nebulizer and one in the IV. The patient would return after another 2-3 months for a post-treatment PFT, 6-minute walk test, and second questionnaire.

This was a good start for gathering objective and subjective data on stem cells being used as a viable treatment for COPD, but I thought it could be expanded. As the year went by, Dr. Vanos and I collaborated on ways to extend the information collected and take that information and use it for research.

His objective is to prove to himself and to his colleagues that stem cells can be a viable option for treating COPD. My objective is to collect these data, organize them so they can be scrutinized, and then present the numbers to Dr. Vanos. We haven’t always been satisfied with what the numbers were, but that has led us to revamp the treatment protocol several times.

First real changes

It has now been a year and a half since I started here, and our treatment protocol has blossomed into something we can be proud of. Due to the data collected by the pre- and post-PFTs, we have been able to create a trending report based off doses used compared to the patient’s post PFT results. We concluded that our initial doses were insufficient to create any statistical changes in the PFT numbers, but we did see some changes in the 6-minute walk test and the St. George’s survey. We began increasing the doses given until we started seeing significant changes in the PFT results.

Our first real changes came from the DLCO. We saw the measurement go from an 8-9% increase to 15% and above! We still didn’t see any real move in the spirometry numbers, but we were excited nonetheless. Dr. Vanos decided to increase the doses even more, until we reached our current dose. Since this a business, I don’t want to reveal too much about our dosing protocol, but I will say that we are significantly higher than the original six units.

Approximately three weeks ago, a patient came back for her post-treatment testing. She was the first one to receive our new dosing amount. Her post-treatment PFT showed significant changes in all areas. Her FEV1/FVC increased by 19%, FEV1 increased by 30%, DLCO increased by 20%, and her hyperinflation decreased. She was able to walk longer and faster on her 6-minute walk test, and although she still had COPD based on her numbers, she moved from the severe category to moderate.

The results were so amazing that I double checked everything that I did. I made sure my PFT machine was working properly (again) and that I did everything by the book. When I showed Dr.Vanos the results, I was so excited. I had to try hard to remain professional when I really wanted to jump up and down while waving the results in his face. Obviously, this is just one person’s results, so more research needs to be completed at this dosing level, but we are cautiously optimistic that we have found the correct dosing level of stem cells for treating COPD.

Other changes

Some other changes that we made to the protocol had to do with adding additional surveys and more information filled out on the 6-minute walk test. I added the mMRC and CAT survey to the St. George’s questionnaire. The reason I did that was because I wanted to make sure that our patients were diagnosed correctly and that they were on the correct medications based off the GOLD standards. Treating COPD with stem cells is difficult, since a lot of outside factors can influence the results. The least that I could do was make sure they were getting the correct medications. Although it’s not necessarily part of my job, I also add as much patient education as I can while patients are doing their testing.

I added a shortness of breath scale to the 6-minute walk test as well. The patient rates his shortness of breath at rest and with exercise from 0 to 10, 0 being no shortness of breath and 10 being the worst he ever felt. It gives me a good indication how the patient will do on the 6-minute walk test, and I would like to eventually study the correlation between the subjective rating of shortness of breath and meters walked.

I’d like to wrap this up by saying how excited I am to be a part of this research and possible new treatment option. Our treatment protocol is ever-evolving, and I expect there to be more changes as we go along. I am grateful to Dr.Vanos for treating me like a valued colleague and sharing this research with me. I hope to publish some results soon and make a lasting contribution to our field.

Pulmonary Function Testing in Pediatrics: Tricks and Tips for Testing the Younger Population

Elizabeth Koch, MRC, RRT, RPFT, and Julie Feldstein MRC, RRT, RRT-NPS, RPFT, AE-C

Testing children can be challenging and fun at the same time. We all know that pulmonary function tests (PFTs) are effort dependent, so getting a child to follow directions is essential.

Make it kid-friendly

Let’s start with PFT criteria. The American Thoracic Society (ATS) and European Respiratory Society (ERS) have published testing criteria regarding PFTs in adults and children. For children, criteria for spirometry is primarily focused on different exhalation times for different age groups. As far as lung volumes and diffusion capacity are concerned, there are no differences for testing. Granted, as you are dealing with smaller patients, volumes will be smaller and sample size for diffusion may not meet ideal volume.

Most PFT systems are designed for all age ranges. Filtered mouthpieces and nose clips are the same. There are slightly smaller, oval mouthpieces that can be added to the filter to accommodate small children, or the filter can be purchased that way.

When testing children, the environment should be welcoming, open, and kid-friendly. Make the room less intimidating by adding vinyl clings or interesting pictures to the walls. For younger children, decrease stimulation by getting rid of extra equipment and any clutter. Lower the lights if you have the ability. Sit down so that you are “equal” or on the same level as the child. Nothing is more intimidating to a child than having an adult stand over them.

When talking with children, use simple, short instructions, focusing on one step at a time. Demonstrate technique, practice off the mouthpiece, and praise! Nobody is ever told that they failed in our lab. Always be positive, praise, and tell them you are proud of them.

Even just saying the word “proud” can make a child smile and feel special.

Tricky tests

Some PFTs are more challenging in kids than others.

Lung volumes, depending on the method, will change the approach. If using a plethysmograph, when describing the shutter closing for a couple of seconds, use a gloved hand on the back of the filter to have the child feel what it will be like. Describe the “panting” as small, tiny “puffs” in and out. With pediatrics, you might need to perform more trials to obtain measurements within 5%. You may need to split the maneuver and obtain slow vital capacity (SVC) separately and/or may need to obtain FRC using the resting mode in place of panting.

Having a picture or decal on the opposing wall may help keep the child focused and relaxed.

When obtaining lung volumes by gas dilution or nitrogen washout, utilizing a flexible, “snorkel” style mouthpiece may help keep a tight seal. Again, having something for them to concentrate or focus on may help with “normal” breathing.

Diffusion is another tricky test to obtain with a child, but is highly possible. Calibrating the gases can be noisy, so let the child and family know this beforehand so they are not startled. Always let the child know that even though there are a lot of directions, they do not have to memorize them and they will be coached throughout the test.

Drawing the breathing maneuver on a piece of paper might help some children and seems to help with children who don’t speak the same language as you do. Using arm and hand motions can also be helpful, giving them a visual cue to assist in performing the test. Showing them where they must take a deep breath or “pull up to” can help with their goal.

When it comes to diffusion capacity, you need to make sure that you have a solid and consistent vital capacity, preferably above one liter. Here’s where that volume comes into play for sample size: when your sample is small, the PFT systems will flag it as an error as it does not meet the computer algorithm for dead-space removal and sample size. Having a rapid response analyzer can help in selecting sample portion when volume is small. We cannot say it enough: practice the steps off the system when giving instructions, break each step down, have them practice holding their breath as you count, and then put it all together — but don’t forget to praise, praise, and praise!

Impulse oscillometry (IOS) is marketed for the younger population. It is still a difficult test to obtain in pediatrics. They still need to follow directions, keep their mouth sealed around the mouthpiece, and wear nose clips. You can always have a parent or co-worker hold the patient’s cheeks during testing. The child can sit on the parent’s lap (this makes it easier for the parent to hold the child’s cheeks and brace him onto the device). Having a distraction, like watching a video, can help ease kids into “normal” breathing.

You need a solid, consistent vital capacity to obtain lung volumes and diffusion. In our lab, if you can obtain a consistent vital capacity, you can attempt lung volumes and diffusion. There are no age limits, but in our experience, around eight years of age is when you have a greater than 80% chance of obtaining most testing (spirometry, lung volumes, and diffusion) with acceptable and repeatable results of good quality. We have obtained lung volumes and diffusion capacity in younger patients, but not consistently enough to state a high percentage of success across the younger ages.

A building process

Some children follow directions well and are very competitive. Some children require “kid gloves” to get all the testing that was ordered. Our purpose as pulmonary function technologists is to get good quality data meeting ATS/ERS criteria. Our goal is to get the “best” test so the child and family can get proper treatment and care.

In summary, performing pulmonary function tests on pediatric patients can be fun. But you have to make it fun: smile, laugh, act silly, tell jokes, and put the child at ease. Use simple, short step-by-step instructions, demonstrate, practice, and always praise their effort. Be positive. Whatever you do, however you do it, know that you may not be able to obtain the perfect or acceptable test the first time or during the first visit, but know that with each subsequent visit, you can build on that experience, which will eventually produce good, clinical tests!

Section Connection

Recruit a new member: Know an AARC member who could benefit from section membership? Ask them to call AARC Customer Service at (972) 243-2272 to add section membership to their overall membership package

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Next Bulletin deadline: Spring-Summer Issue. Please contact Jennie Weltz-Horpedahl if you would like to contribute an article.