Spring/Summer 2019 Diagnostics Bulletin

Spring/Summer 2019 Diagnostics Section Bulletin

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

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

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

In this issue:

AARC Congress Diagnostic Highlights

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

AARC Congress 2018 was held in Las Vegas, NV, this past December; if the town itself didn’t dazzle enough, the fantastic diagnostic presenters sure did!

GLI symposium

First up was Sanja Stanojevic, PhD. Her name should sound very familiar, as she is one of the authors of the Global Lung Function Initiative (GLI) reference equations. Dr. Stanojevic gave three informative presentations in the four-part GLI symposium.

Her first presentation focused on the need for reference equations, challenges in interpreting pulmonary function tests, and the advantages of using the GLI reference equations. Her second presentation dove into the interpretation of spirometry results using GLI and the need to move away from fixed cutoff points (i.e., 80% of predicted value) during interpretation in favor of z-scores, which are less likely to cause a normal value to be misinterpreted as abnormal. Dr. Stanojevic’s final presentation was on the implementation of DLCO equations and the implications for their practical use.

Gregg Ruppel, RRT, RPFT, FAARC, rounded out the GLI symposium with a progress report on the work being done by the GLI network on lung volumes. Currently, the group is collecting data, and we can all look forward to seeing those reference sets in the future.

I wish I could’ve included every word from this symposium here — and, had I been able to write it all down, I probably would have — because it was a great overview of the benefits the GLI reference equations offer.

Visit these websites for some great resources about GLI:

Spirometry in primary care

Following the GLI symposium, there were two presentations on spirometry in the primary care setting by Curt Merriman, RRT, CPFT, and Amanda Clark, RRT.

Spirometry in the primary care setting has a history of poor quality when not performed by qualified individuals. Curt discussed the history of spirometry in the primary care setting and how test quality can improve with training programs that include initial and ongoing education, oversight for offices providing spirometry, and remedial training, if necessary.

Amanda approached spirometry in primary care from a different angle, discussing techniques to better explain spirometry and spirometry interpretation to primary care providers in order to help reduce the misdiagnosis of patients receiving spirometry in their offices.

New standards

The second diagnostic symposium offered at Congress covered the three diagnostic standards released in 2017. Matt O’Brien, RRT, RPFT, tackled the ERS Technical Standard for Bronchial Challenge Testing. He did a fantastic job breaking this document down into a start-to-finish workflow. Highlights included the move to tidal breathing and different inhalation times, as well as the change to reporting PD20.

Jeff Haynes, RRT, RPFT, FAARC, addressed the ATS/ERS Standard for Single-Breath Carbon Monoxide Uptake in the Lung. Jeff discussed the importance of calibration and quality control checks, including biologic control measurements, DLCO syringe checks, syringe leak tests, and linearity checks to ensure equipment is operating properly. Jeff also emphasized the importance of coaching the patient to reach TLC during testing and utilizing the grading system so exams of poor quality are not reported.

Up last (but certainly not least) in the diagnostic standards symposium was Carl Mottram, BA, RRT, RPFT, FAARC, who covered the ATS Standard for Pulmonary Function Reporting. This session was very informative, as it covered not only the ATS document and the changes that impact PFT labs but also showed that there are some differences in reporting standards and grading or scoring between this document and other organizations. Emphasis again was put on moving away from fixed cutoff in favor of z-scores and LLN.

More great topics

The last series of diagnostic sessions covered a variety of topics. Jeff Haynes was back to discuss the physiologic and technical aspects of pulmonary function testing in the obese patient, which he has elaborated on for us in an article in this edition of the Bulletin. A few things to remember in this patient population are that vital capacity and total lung capacity are mostly unaffected, but there is loss of ERV. This patient population may also have a higher DLCO due to an increased cardiac output.

Following Jeff was Matt O’Brien discussing the “Dollars and Sense of PFT Testing.” Matt’s presentation really drove home the need to evaluate current PFT lab practices and services offered, looking for opportunities to improve workflow without sacrificing quality.

Dr. Michael Morris gave a fantastic presentation titled “Clinical Application of Impulse Oscillometry.” He shared some interesting case reviews, showing how impulse oscillometry can be used to supplement spirometry testing and assist in the diagnosis of asthma and other respiratory disorders.

Katrina Hynes, MHA, RRT, RPFT, presented on the “Clinical Application and Interpretation of FENO.” She also shared some interesting case studies, showing how FENO testing can be used to assess airway inflammation and guide medication management in patients with allergic or eosinophilic asthma. For those wanting more detailed information on this topic, Katrina referenced the ATS clinical practice guideline published in 2013.

Carl Mottram was the final diagnostic presenter of the Congress, providing a “gap analysis” of current clinical practice guidelines and technical standards. Carl gave a really thought-provoking presentation comparing and contrasting how the written language of a document and clinical practice can result in significant gaps and how patient care is impacted by those gaps.

Common themes

There were two very common themes running through the diagnostic presentations at last year’s Congress. First was the need to be aware of and, if possible, begin implementing the various published standards of 2017, as well as the GLI reference sets. With all the new standards there is much work to be done, but with the possibility of lab accreditation on the horizon we would all benefit from starting that work now.

The second was the move from fixed cutoff points when looking at patient test results. This will be a challenge for a variety of reasons, and changing providers’ ways of thinking and equipment limitations will be two of the big ones. This isn’t a new topic but it’s certainly one worth being brought up again.

Diagnostic Section Recognition

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

An overview of the AARC Congress would not be complete if I didn’t take time to recognize the Diagnostic Section members who contribute so much to our profession. If not for the work done by those who laid the path for us, or those who took the time to write books, submit articles, offer support, and mentor others, we would not be where we are today. Each of those mentioned below have made contributions to our profession in their own individual ways and, by doing so, have helped those in the PFT lab better understand the technical aspects of the tests they perform and improve the quality of services they provide.

Every year, a member of the Diagnostics Section is chosen for the AARC Specialty Practitioner of the Year award. Recipients of this award demonstrate professional service, leadership, and contributions to or service in their specialty area of practice, furthering the science of respiratory care.

Jeff Haynes

When I consider these criteria, I can think of no one more deserving than Jeff Haynes, RRT, RPFT, FAARC, our 2018 Diagnostic Section Specialty Practitioner of the Year. Jeff is a champion for quality in the pulmonary function lab and a tireless supporter of technicians across the country through his contributions to the Diagnostic Section discussion list on AARConnect and his presentations at conferences both at the state and national level.

Gregg Ruppel

Gregg Ruppel, RRT, RPFT, FAARC, is no stranger to anyone in the Diagnostics Section. The author of nine editions of Ruppel’s Manual of Pulmonary Function Testing, presenter, educator, and mentor, Gregg has served on the National Board for Respiratory Care (NBRC) in many capacities and is a true legend of respiratory care. This year Gregg was the recipient of the NBRC’s highest award, the Sister Mary Yvonne Jenn, CRNA, RRT Lifetime Achievement Award, a well-deserved honor for a leader in our profession.

Richard Johnston

Recognized this year during presentations and at the Diagnostics Section meeting was Richard Johnston, CPFT, author of the blog PFT Forum Blog. Richard has worked in the field of pulmonary diagnostics for more than 40 years, and as a lab manager for more than 30. Those familiar with Richard’s blog know the lighthearted, witty way he turns errors in the lab into learning opportunities for us all. In December 2018, Richard posted his final blog, sharing that he had been diagnosed with cancer and given a poor prognosis. In his final post, he challenged us to keep learning and keep questioning, as he has for so many years.

Pulmonary Function Testing of the Obese Patient

Jeffrey Haynes, RRT, RPFT, FAARC

Obesity is a worsening public health problem affecting nearly every industrialized country. The CDC’s last survey indicated that 40% of adults and 18% of youth in the U.S. are overweight or obese. Obesity is associated with respiratory symptoms and exercise intolerance. The physiology of obesity-related lung disease is both complex, and in some cases, counterintuitive. Pulmonary function technologists need to appreciate the physiology to understand what is happening in front of them when they are testing obese patients.

Resisting implicit bias

According to the Stanford Encyclopedia of Philosophy, implicit bias is the “relatively unconscious and relatively automatic features of prejudiced judgment and social behavior.” Implicit bias can have a detrimental impact on the care of obese patients. For example, a physician may explicitly believe that obesity can result in true respiratory disease. However, when an obese patient is seen in the office because of dyspnea, implicit bias may reflexively make the physician conclude that “the patient is dyspneic only because he’s overweight.”

A few years ago, I performed an exercise challenge test on a 308-pound, 49-year-old male. He complained of dyspnea on exertion and when tying his shoes. Implicit bias might make one conclude that he’s only dyspneic because of his obesity. However, the patient’s exercise challenge was positive (see figure 1). The patient had real asthma, which would not have been diagnosed and treated if the physician would have allowed implicit bias to affect his clinical decision-making.


Do we really need to measure the patient’s weight?

Weight is not typically used in reference equations for routine pulmonary function tests. In addition, obese patients may express embarrassment about having their weight measured. For these reasons, some may deem weight measurement unnecessary. However, an accurate weight needs to be reported to aid in test interpretation (i.e., can the reduction in respiratory function be explained by obesity?). In addition, weight is used to calculate lung volumes via nitrogen washout (N2 in tissues) and plethysmography. Weight should always be measured; self-reported weight is not reliable.


Obesity is associated with multiple respiratory symptoms, including both dyspnea and chronic cough. In one study, obesity was a greater risk factor for respiratory symptoms than mild COPD.1

In addition, there is a distinct phenotype of obese patients who experience more intense dyspnea, which is not explained by the oxygen cost of breathing. One theory for intense dyspnea in some obese patients is impaired signal gating to the sensory cortex of the brain. Signal gating is akin to a call screener. In this case unimportant or redundant signals to the sensory cortex that might unnecessarily produce dyspnea are not blocked.

Gas exchange

Gas exchange is clearly affected by weight gain. Gabrielsen et al. showed that PO2 declines and PCO2 rises with BMI.2 This relationship was true for multiple measures of obesity, including waist circumference, waist to hip ratio, and neck circumference. Littleton et al. showed a similar relationship between BMI and PO2.3 The reduction in PO2 closely correlated with a loss of expiratory reserve volume (ERV) and was independent of PCO2.

Lung volumes

Obesity has a demonstrable effect on lung volumes, although not all volumes and capacities are affected equally. Jones et al. showed that vital capacity, total lung capacity, and residual volume (RV) fall in a linear fashion as BMI increases.4 However, the decline in these indices usually remains above the lower limit of normal (LLN). So unless serial measurements are being assessed, these indices may simply be interpreted as normal.

The most pronounced effect of obesity on lung volumes is reflected in expiratory reserve volume (ERV) and functional residual volume (FRC), which fall exponentially and below the LLN. Declines in ERV and FRC occur early in patients who are gaining weight, when the BMI is still <30 kg/m2. The reduction in ERV can be seen during spirometry testing as the tidal volume loop shifts rightward toward the RV (see figure 2.).


The non-specific pattern

In obese patients, forced vital capacity (FVC) and the forced expiratory volume in the first second (FEV1) may decline together, creating a restrictive pattern on spirometry: FVC and FEV1 <LLN; FEV1/FVC >LLN. The non-specific pattern (NSP) is present if the decline in FVC and FEV1 is accompanied by a TLC >LLN. An example of an obese patient with the NSP is shown in figure 3. Hyatt et al. showed that 50% of patients with the NSP had a BMI >30 kg/m2.5 The NSP may hide underlying obstruction; in these patients the FEV1/SVC may reveal obstruction in the presence of an FEV1/FVC >LLN.


Diffusing capacity (DLCO)

The conventional wisdom regarding obesity and DLCO is that obesity increases DLCO; indeed, the 2005 ATS/ERS technical standard on interpretive strategies lists obesity as a source of elevated DLCO. It is notable that this is supported by a single citation. There is in fact conflicting data regarding DLCO and obesity.

For example, Enache et al. studied pulmonary function in normal and obese subjects and found that DLCO declined with BMI, and this decline was associated with reduced VA and increased the KCO.6 The increase in KCO suggests that the decrease in the DLCO was due to a reduced alveolar volume-to-surface area ratio.

Six-minute walk test

Obesity clearly reduces exercise performance, and this is reflected in a reduced 6-minute walk distance (6 MWD). Larsson et al. found that the mean 6 MWD was 162 meters shorter in obese patients when compared to lean controls.7

Reference equations for the 6 MWT can also be affected by obesity. We performed a 6 MWT on a 79-year-old obese female. The patient completed the 6MWT, but had to take three short breaks due to dyspnea. The test was performed while the patient breathed room air and she desaturated to 79%. The 6 MWD was 228 meters, above the LLN, and 82% of the predicted value. The 6 MWD percent of predicted was calculated according to the reference equation published by Enright and Sherrill for females: (2.11 x heightcm) – (2.29 x weightkg) – (5.78 x age) +667 m).8

This calculation was made using the patient’s measured weight of 122.5 kg; however, Enright and Sherrill excluded subjects with a BMI >35 kg/m2, and the median BMI amongst the female participants in the study was 25.5 kg/m2. When the percent of predicted and LLN were recalculated using the patient’s ideal body weight, 57.1 kg, the walked distance was below the LLN and only 53% of predicted. When a reference equation that doesn’t include weight was used, the 6MWD was 42% of predicted. When applying a reference equation derived from obese subjects, the 6MWD was 51% of predicted. The reference equation by Enright and Sherrill to calculate the predicted 6MWD in obese patients may produce values that are not reflective of the clinical picture.

Obesity and asthma

Asthma is common among obese patients. Clinicians may view an asthma diagnosis in the obese patient as questionable, assuming that the respiratory symptoms are due to obesity, not true asthma. However, asthma in the obese patient is a real concern.

There are three potential causes for asthma in obesity: systemic inflammation, oxidative stress, and mechanical forces on airway smooth muscle. Of the three, mechanical forces on airway smooth muscle appears to be the most important. Reduced lung volume reduces airway diameter and resistance. Lung inflation relaxes airway smooth muscle, and diminished inflation may keep airway smooth muscle in a semi-latched state, resulting in airway hyper-responsiveness. Asthma in obese patients is associated with neutrophilic inflammation, low exhaled nitric oxide, and reduced responsiveness to inhaled corticosteroids.

What happens when patients lose weight?

Weight loss has a tremendous impact on obesity-related respiratory symptoms and perturbed lung function. Weight loss increases inspiratory capacity, expiratory reserve, and residual volumes. In addition, gas exchange, dyspnea, 6 MWD, asthma control, and airway responsiveness all improve with weight loss. Indeed, the most effective treatment for adult-onset, obesity-related asthma is weight loss.


Obesity commonly produces respiratory symptoms, and there is a distinct phenotype of obese patients with more intense dyspnea. The primary effect of obesity on lung mechanics is the loss of ERV. In obese patients, FEV1/SVC may have more sensitivity for airway obstruction than FEV1/FVC. Obesity-related asthma is a real condition that is primarily due to mechanical effects on small airways. Weight loss improves symptoms and the functional impact of obesity.


  1. Zutler M, et al. Obesity, but not undiagnosed airflow obstruction, is linked to respiratory symptoms and decreased functional capacity in adults without established COPD. Prim Care Respir J 2012;21(2):194-201.
  2. Gabrielsen AM, et al. The relationship between anthropometric measures, blood gases, and lung function in morbidly obese white subjects. Obes Surg 2011;21:485-491.
  3. Littleton SW. The effects of obesity on lung volumes and oxygenation. Resir Med 2017;124:15:20.
  4. Jones, et al. The effects of body mass index on lung volumes. Chest 2006;130:827-833.
  5. Hyatt, et al. Conditions associated with an abnormal nonspecific pattern of pulmonary function tests. Chest 2009;135:419-424.
  6. Enache, et al. Impact of altered alveolar volume on DLCO. Respiration 2011;81:217-222.
  7. Larsson UE, et al. The six-minute walk test in outpatients with obesity: reproducibility and known group validity. Physiother Res Int 2008;13:84-93.
  8. Enright PL, Sherrill DL. Reference equations for the six-minute walk in healthy adults. Am J Respir Crit Care Med 1998;158(5 Pt 1):1384-1387.

NBRC Credential Renewal

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

There have been rumblings of changes coming to the National Board for Respiratory Care (NBRC) Continuing Competency Program (CCP), and this was mentioned briefly at the AARC Congress. While all the details of these changes are not yet clear, I was able to find some information on these changes on the NBRC website.

Changes to the CCP were made in response to changes in accreditation standards. The CCP has also been renamed the Credential Maintenance Program (CMP) to more accurately represent the purpose of the program. The changes to the CMP will apply to those who earned their credential July 1, 2002, or after.

The CMP will have three options available to maintain your credentials. The first two options most are familiar with: earn another NBRC credential, or pass the same credentialing examination again. Soon, there will be a third option to take quarterly assessments and/or document up to 30 continuing education credits. Costs appear to remain the same at $125 for the five year credential period, collected annually in $25 increments.

For those who opt for the assessments, they will be available for PFT credentials after October 2019. Assessments will be taken on the NBRC website and will consist of multiple choice questions, with a five-minute time limit for each question. Assessments are intended to be in an open-book format, giving the test taker time to reference materials, but it is noted that other people should not help. The number of questions varies for each assessment group:


As the implementation date draws closer, I am sure we will hear more about the changes to the CMP program, and I hope to provide an update in the Fall/Winter Bulletin. For more information, please visit the FAQ Section of the NBRC website.

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

Section discussion list: Go to the Diagnostics Section on AARConnect to network with your fellow section members.

Next Bulletin deadline: Fall/Winter Issue. Please contact Jennie Weltz-Horpedahl if you would like to contribute an article. Jennie and D’Aun are here to help guide you through the process if you’re a new contributor!