Big Breaths In at the Bedside: Bedside Spirometry

Diagnosis

To diagnose COPD, a person must perform spirometry, according to the Global Initiative for Chronic Lung Disease (GOLD). This is where a new problem lies.  When looking at data from the VA, 826 patients discharged from the hospital were diagnosed with COPD, yet only 56% had ever shown evidence of obstruction on spirometry. A different review of data reported by Loh et al. showed that of patients who developed symptoms of COPD, only 1/3 were tested with spirometry. This is confirmed by other data reported by the NHLBI showing that COPD was only confirmed in 30% of these patients with spirometry testing. 

According to GOLD, spirometry should be performed 12-16 weeks after discharge. This allows the patient to be back to baseline, preventing skewed numbers and allowing for a proper test. But the baseline can vary from day to day for these patients, and their best efforts might not be different from where they were when they were in the hospital. This leads us to ask why not perform the testing while the patient is in the hospital?

The easiest and quickest way to perform spirometry in the hospital would be with a bedside spirometer. This has often been used for pre-operative testing while also looking at neurological conditions. While it was felt not to be as accurate, it does allow for greater ease of accessing patients who are felt to be suffering from an acute exacerbation of COPD (AECOPD). As more data becomes available, it becomes clear that this may be a good option.

In a study out of Wake Forest, patients were tested during their hospital admission when it was felt that they were no longer in distress (on average two days post-admission) and tested four weeks after discharge. Patients were required to exhale for at least six seconds for an acceptable maneuver and needed to reproduce that maneuver a second time to be included. They tested 144 patients for obstruction, using an FEV1/VC < 70% as the marker for obstruction. Of the patients, 94.4% were found to have an obstruction on outpatient testing. 82.6% of the patients showed an obstruction on both outpatient and inpatient testing. Fifteen patients displayed a restriction on inpatient testing, with 7 of those now displaying an obstruction on outpatient testing.   

Another study out of New Zealand found similar results. They tested 49 patients at discharge and one month later. They found that 41 patients had COPD at discharge based on spirometry and 39 at one month post-discharge. They concluded that testing done at discharge was as accurate as testing performed one month after discharge. 

As the need for spirometry in diagnosing COPD is vital, and patients lack testing once being discharged from the hospital, we must find a way to correct this. Bedside spirometry offers this opportunity and has been shown in limited studies to be nearly as effective at obtaining adequate results. And while a patient recovering from an AECOPD may not give the greatest results, the results that are provided can further lead to whether more testing should be pursued as well as guide clinicians to proper treatments while in the hospital. And with more studies evaluating the results of bedside spirometry to outpatient spirometry, a greater push for bedside spirometry would be the best action for the patient.