Discussing routine inpatient spirometry testing

When we think about pulmonary function testing, we usually think about testing in the ambulatory or post-acute care setting. Even relatively simple spirometry tests are typically done in a patient office or clinic, because clinicians are looking for a diagnosis or ongoing evaluation during the ‘chronic stable state’ of someone’s respiratory condition.

But is that enough?

Are inpatient respiratory departments missing out on a chance to not only demonstrate more value, but have an additional impact on long-term patient care? Let’s take a look.

Historical applications for spiromety testing #

Historically, there has been a limited (but no less important) role for spirometry in the inpatient world. Perhaps the most obvious application is during the pre-operative period, especially when a patient is deemed to be at an elevated risk for postoperative pulmonary complications (PPCs).

A decade ago, this might be the first clinical experience with spirometry: finding those patients who were admitted for a thoracic or abdominal procedure but who had somehow missed getting pulmonary clearance beforehand. This wasn’t necessarily the optimal setting for such testing, but it was certainly better than nothing.

A 2018 study found that in relatively high-risk populations (those over 60 years old, those less than 60 but with an active chronic respiratory condition, or active smokers), the FVC percent predicted value inversely correlated with the risk of PPCs during gastric or colorectal procedures¹.

Logically, this makes sense; if your patient has impaired lung capacity prior to operating, it’s not likely to be sufficient during the recovery phase, and could potentially lead to atelectasis.

However, the use of spirometry for risk assessment is not without controversy, particularly when it comes to extrathoracic surgery. The most current risk assessment guidelines from the American College of Physicians state that PFTs “may be appropriate in patients with a previous diagnosis of chronic obstructive pulmonary disease or asthma”, essentially putting them on the same level as a chest X-ray for people without obvious risk factors².

Although that guideline is over a decade old, it was reinforced in 2012 by a meta-analysis from the United Kingdom that could not find any significant evidence to support the broad use of spirometry (or several other common tests) as a pre-op screening tool³.

The situation is different for people with clear risk factors, such as a previous diagnosis or exercise intolerance without an obvious cause. In these cases, there seems to be a more obvious role for breathing tests, including helping to determine whether the “dyspnea of unknown etiology” can be chalked up to pulmonary disease, or cardiovascular disease.

Still, the jury is still out on even these roles, leading some to opine that the additional data provided by spirometry doesn’t add much to a decent physical examination; certainly not enough to move the needle in risk assessment⁴.

Additionally, one would anticipate that most of these cases can now be detected in the ambulatory care setting, once again apparently limiting the utility of bedside spirometry.

Recommendations for spirometry testing for inpatients #

While preoperative spirometry has been fading, a new rationale is coming into view.

As mentioned in the introduction, most spirometry is done during a stable phase in someone’s disease process. The Global Initiative for Chronic Lung Disease (GOLD), for example, recommends PFTs be done in the 12-16 week range after an inpatient admission⁵.

This recommendation, like all of GOLD’s work, comes out of various meta-analyses and related studies and represents the best possible perfect‑world recommendation for the initial diagnosis of chronic obstruction. Of course, neither we nor our patients live in a perfect world, and we cannot allow the perfect to become the enemy of the good. That means in the real world, there are some issues with GOLD’s recommendation.

First and foremost, there are still too many practices that don’t have access to spirometry equipment or the skilled personnel needed to obtain high-quality spirometry data.

At least a quarter of primary care practices report not having access to equipment, and only one-third of people with COPD report having had a spirometry test after reporting symptoms⁶. According to the National Board of Respiratory Care (NBRC), fewer than 20,000 certified or registered pulmonary function technologist credentials have been awarded ever⁷. Compare that with the roughly 325,000 primary care providers in the United States⁸, and the supply shortage becomes vividly clear.

These issues drive traffic to pulmonology office and dedicated PFT laboratories, which are obviously fewer in number. There are estimated to be around 12,000 pulmonary practices in the United States, but even those tend to be clustered near urban spaces, and only one-third of people with COPD in rural counties have one within 10 miles of their home. A solid 5% had to go 50 miles or more to reach their pulmonologist⁹.

There are presumed to be a little over 5,000 PFT labs throughout the United States with potentially better accessibility, as they’re generally closely affiliated with or located at hospitals¹⁰.

Still, transportation and logistical issues are rampant in the chronic respiratory population (a leading reason pulmonary rehabilitation is still under-utilized), presenting additional access barriers even when geography isn’t an issue¹¹.

The ongoing COVID-19 pandemic also presents logistical issues.

Many PFT labs have either shut down or advertise markedly restricted availability due to the uncertain risk presented by the virus. While there are certainly avenues available to reopen and return to routine respiratory testing safely, it also appears that some areas will be impacted more severely and suspend testing even more.

This has critical implications for diagnosis and management of a wide variety of cardiopulmonary conditions, and represents some of the hidden cost of the respiratory care. At the same time, we still see people needing inpatient services for non-COVID-19 conditions. So instead of making them come to the testing, why not take the testing to them?

It seems like a potentially radical idea, flying in the face of tradition and current guidance. There is a solid rationale for it, though, thanks to several studies that have come out over the past few years. Perhaps most importantly, in 2018 a team from Wake Forest School of Medicine found that spirometry performed during an inpatient admission for COPD exacerbation had an 83% positive predictive value for chronic obstruction (verified during a chronic stable state)¹².

There was only a 1% error margin between inpatient and outpatient spirometry in this study, highlighting the acceptability of testing performed at a hospital (where most PFT labs and staffers are found). The group was not able to predict the severity of the obstruction, but given the de-prioritization of airflow obstruction after diagnosis, this seems a minor quibble at best. The benefits of detecting COPD in previously undiagnosed people seem to far outweigh any lack in this factor.

The Wake Forest results reinforced earlier findings that came from a multicenter study published by a team from the University of Chicago back in 2012. That project found that reproducible spirograms of sufficient quality could be obtained in at least 75% of hospitalized patients (with symptoms of acute exacerbation of either COPD or asthma)¹³. Where this study stands apart from its successor is that this group was able to exclude airflow obstruction in roughly one-fifth of those people previously diagnosed with an airway disorder.

This highlights an often-overlooked issue in the COPD world; overdiagnosis may be almost as prevalent as underdiagnosis. This seems particularly true in people with obesity, where shortness of breath can come from a variety of causes outside the lungs, a finding noted by the Chicago team.

As a practical matter, inpatient spirometry has also become easier on the clinical staff tasked with conducting it. Modern spirometers require much less maintenance than older models.

With advances in technology, spirometers are able to provide calibration-free spiometry testing, reducing workloads and time commitments. This makes diagnostic bedside spirometry feasible even during critical staffing times (such as the ongoing pandemic), allowing for both better allocation of clinical staff and improved outcomes.

Considering that even advanced pulmonary function tests like diffusion capacity (DLCO) and lung volume measurement can now be performed with portable pulmonary testing devices, a wider variety of patients may now have access to testing, and a larger number of respiratory departments may have a new strategy to increase revenue and demonstrate the value of respiratory therapists and pulmonary function technologists.

The future of respiratory testing #

All in all, the era of bedside spirometry is far from over.

Despite its roots (and continued potential value) in backup pre-operative testing, the utility of spirometry continues to grow in our unusual and uncertain times. Adding spirometry inside the hospital provides people dealing with shortness of breath access to definitive testing while preventing unnecessary exposures to the novel coronavirus, the flu, or other pathogens.

It brings diagnostic experts together with the equipment needed to enhance clinical decision making that can not only improve an inpatient stay but change the course of someone’s entire disease management plan. It provides respiratory departments with additional value-based opportunities at a time when many organizations continue to struggle with the financial impacts of the pandemic. And most importantly, it provides the ability to improve quality of life and outcomes for a wide array of people with cardiac and pulmonary conditions, not to mention those who have been inaccurately diagnosed.

It’s another example of how some of the most complex issues can have a simple solution for those who are willing to think outside the (body) box!

Written by

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  Michael Hess

  BS, RRT, RPFT