FEV1 Performance Among Patients With Acute Asthma Observations

Grapple with previous articles relating to this topic:

In contrast to most outpatient settings, the patients studied were acutely ill and severely obstructed and not expecting to perform spirometry during their ED visit. This study shows that with a strong emphasis on several quality measures, spirometry for the purpose of obtaining an FEV1 can be performed in acutely ill ED asthmatics. Most patients (almost three quarters) were able to perform study-specific acceptable and reproducible tests on ED arrival. As FEV1 improved with treatments, and presumably patient experience and comfort with the spirometer increased, so did the skills at performing spirometry. There was little difference between the quality of maneuvers performed after 1 to 2 h of ED treatment and those performed during the follow-up outpatient period.

Among the factors independently associated with spirometry quality were the initial severity of airway obstruction and the site itself. A lower FEV1 was associated with less reproducible efforts at the first time point but only when obstruction was very severe (< 25% predicted). Even among this subgroup, nearly two thirds met the study-specific acceptability/reproducibility criteria. By the third time point, overall quality had improved such that the relationship between the severity of obstruction and the ability to achieve study goals had disappeared.

Our data indicate that factors particular to individual sites are more important than many factors particular to the patient, such as the patient’s perception of dyspnea, age, BMI, gender, and race. Of note, investigator prior experience in performing spirometry was not associated with ability to meet study goals. Prior to training for this study, most investigators had never performed spirometry in a healthy individual much less an acutely ill asthmatic. These observations support the concept that inexperienced investigators can be quickly trained to meet minimal performance standards, even when spirometry is performed under challenging conditions, such as an acutely ill asthmatic in an ED. We anticipate that performing spirometry on severely obstructed asthmatics in other settings (outpatient or hospitalized) could obtain similar or better performance, particularly if continual quality assurance is maintained.

Optimal performance of FEV1 maneuvers was of high importance in designing the clinical trial. It is possible the relative success in meeting performance standards was due to the high priority we placed on spirometry from the start and in training and quality control, which included spirometers that provided immediate feedback on technique and acceptability, and central monitoring of efforts. For this reason our results may not be applicable to trials with less rigorous spirometry protocols. It is also possible that less rigorous spirometry programs could achieve similar results; this needs to be studied.

To our knowledge, this is the first study to detail the performance of spirometry in an acute care setting. Many clinical trials report FEV1 as the primary end point or the main clinical measure of illness severity, utilizing spirometry to determine the efficacy of an intervention. For managing acute episodes of asthma in the ED, consensus guidelines base treatment and hospitalization decisions on objective assessment of pulmonary function. With the availability of smaller, less sophisticated, and inexpensive spirometers, more and more clinicians will have access to these devices and professional societies may encourage practitioners to measure FEVj instead of peak flow. Identifying potential clinical benefits of using FEV1 over PEF in an acute care setting would need further study, as would the ability of ED practitioners to be taught to measure FEVj with the simpler and more practical devices, and to maintain the skills needed to assess FEV1 over time.

ATS guidelines for performance of spirometry were not developed specifically for measuring FEVj in severely obstructed, acutely ill asthmatics, and therefore criteria for acceptability and reproducibility were modified for the study population. Even though we did not require investigators to adhere to ATS guidelines, as it turns out a number of criteria were often met. When we retrospectively applied more stringent criteria for start of study (BEV < 5% of FVC or 0.15 L, whichever is greater) and reproducibility (two largest FEV1 values within 0.2 L[ATS 1994] or 0.15 L [ATS 2005]), performance results moderately dropped compared to study-specific criteria. Since investigators were trained to meet the study and not the ATS performance criteria, it is possible that performance results would more often have met ATS guidelines had we used ATS criteria as the study standard.

It is unknown whether or not our performance criteria allow measurement of the most “optimal” FEV1. We required at least two acceptable maneuvers (similar to National Lung Health Education Program recommendations) rather than three or more (as recommended by the ATS/ERS guidelines). This was done out of concern for patient comfort and to minimize treatment delays in this acutely ill population. As it turns out, many patients were able to exceed our minimal recommendations and perform multiple exhalations during the ED portion of the study. It is possible that higher FEVj values might have been obtained in some cases if additional maneuvers were performed, or that efforts were made to match the best FEV1 within 0.20 L or 0.15 L. It should be noted that early in the ED visit, patients were severely obstructed with the FEVj typically < 1.5 L; when there is severe obstruction, defining reproducibility at 10% may be more conservative than using differences of 0.20 L or 0.15 L, Although this study indicates that set performance guidelines can be achieved in an ED setting, we cannot determine whether adhering to the ATS/ERS guidelines or a modified performance criteria provide the most optimal clinical data, and this is an overall limitation of our study.

Regarding start of exhalation tests, the true FVC was not usually obtained because we did not require a prolonged exhalation. Therefore, the BEV, when expressed as a percentage of the FVC, is overestimated, causing some apparent failures to meet ATS performance criteria. In addition, we applied more stringent goals than required by ATS criteria for rapid “blast out” exhalation effort during the first fraction of a second of each maneuver. Investigators were encouraged to achieve a PEFT of < 85 ms (a very rapid start), while a PEFT of < 120 ms met our study acceptability criteria (the same as a 1994 ATS optional index). Previous investigators have shown that very vigorous initial exhalation efforts (eg, very short PEFTs) in healthy adults were sometimes associated with small mean reductions in FEVX (negative effort dependence due to gas compression).