FEV1 Performance Among Patients With Acute Asthma Research

Current practice guidelines for the treatment of an acute asthma exacerbation, such as in the emergency department (ED) setting, recommend that objective measures of pulmonary function such as peak expiratory flow (PEF) and FEV1 be used. Mechanical peak flow meters are most commonly used in the ED setting since they are inexpensive and easy to use. However, FEV1 as a measure of asthma severity has advantages compared to PEF. These include greater accuracy, less effort dependence, better repeatability, and for some spirometers the availability of real-time graphics and quality assurance checks to confirm reliability of the re-sults.

Performance of spirometry in the ED presents challenges not faced in office practice or a pulmonary function laboratory. ED patients are often acutely short of breath, fatigued, uncomfortable, and anxious. Coughing during forced exhalation maneuvers is more common in acutely ill patients. In addition, the ED environment itself can be chaotic, and the patient may have never performed spirometry before.

Pulmonary Function Laboratory

Recommended standard procedures and goals for performance of diagnostic-quality and research-quality spirometry have been published, and studies have shown that these goals can be met by approximately 90% of patients tested in a pulmonary function laboratory, as well as approximately 90% of children and adults in research studies.’ However, the ability to perform spirometry in asthmatics during an acute exacerbation has not been reported. A multicenter clinical trial evaluating the efficacy of a leukotriene-modifying agent to treat acute asthma in adults used subsequent change in FEV1 as an important outcome measure, providing the data for this analysis. The goal of this study was to describe the performance of spirometry for purposes of obtaining an FEV1 among acutely ill asthmatics in an ED setting.

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Inclusion and exclusion criteria for the trial have been described. Briefly, patients were 12 to 65 years old and presented with an acute episode of asthma, with FEV1 <70% of predicted at ED entry and after a single aerosol treatment with albuterol (find more information). Spirometry was performed on ED arrival (baseline, time 0) and after 30, 60, 120, and 240 min. Albuterol treatments were administered after each spirometry test. For patients not hospitalized, follow-up spirometry was scheduled at day 10 and day 28 after ED discharge. Patients who relapsed prior to the scheduled visit were not required to maintain the follow-up appointment. For this analysis, we included all patients who had one or more spirometry tests done during the study.

All centers used the same model spirometer (KoKo Spirometer; Pulmonary Data Services; Lewisville, CO) for the ED visit and outpatient follow-up. Percentage of predicted FEV1 was calculated according to Crapo et al, with predicted values for African-American patients calculated as 88% of the predicted value for whites. Hispanics, Asians, and others used the predicted value for whites. Spirometer calibration was checked using a 3-L syringe each day of testing.

Training

Investigators were first trained as a group during a half-day session. Most of the investigators performing spirometry were ED study personnel (registered nurse, physician assistant, or research assistant) who had no prior training in spirometry. The investigators were taught to use the equipment, transmit the data electronically, understand study-specific criteria, and perform spirometry under a number of difficult practice scenarios (eg, uncooperative patient, coughing, tongue-obstructing mouthpiece, poor efforts). This was followed by a second, half-day review session conducted at each individual site. After completion of the training sessions, investigators were required to independently obtain and transmit three sets of spirometry tests on nonstudy individuals for central review of quality.

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Spirometry Technique

Spirometry Technique

All patients were asked to sit straight, either in a chair or on a stretcher with their legs over the side. They were instructed to inhale completely and then exhale with maximal force, for at least 2 s. A tight seal was ensured around the mouthpiece. To reduce discomfort, nose clips were not used. Patients were told to “take as deep a breath as possible” and “blast as fast and hard as you can” and “keep blowing until I ask you to stop.” Coaching was active and vigorous, instructions repeated as necessary, and patients given immediate feedback regarding their technique.

Quality Goals

American Thoracic Society https://www.thoracic.org/ (ATS) recommendations for within- and between-maneuver acceptability criteria were modified for the acutely ill population. Maneuver acceptability was defined for this study as a back-extrapolated volume (BEV) < 5% of the FVC or 0.15 L, whichever is greater, or a time to peak flow (PEFT) < 120 ms. To further ensure a strong start to the effort, investigators were encouraged to obtain a PEFT < 85 ms (although a PEFT 6 s). However, many staff coached the patients to exhale for > 6 s. Performance of three or more acceptable efforts was requested, but two acceptable efforts were considered adequate. FEV1 values were considered adequately reproducible if the two best acceptable efforts matched within 10%, instead of the 1987 ATS recommendation of 5% or 0.10 L or the 1994 ATS recommendation of 0.20 L. FVC reproducibility was not considered because we did not attempt to obtain the FVC.

At the end of each maneuver, the computer displayed whether the most recent maneuver and test session met study acceptability and reproducibility goals, and corrective measures were suggested on the screen as needed. Graphs of the inspiratory and expiratory efforts were displayed in real time, and the flow-volume loop and volume-time spirogram were displayed immediately after each maneuver. All raw maneuver data were stored in the computer and sent for independent central review. Feedback was given through a structured document when compliance to criteria was good, and telephone follow-up (and in one instance a site visit) was made when criteria were not generally met.

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Statistical Methods

Factors associated with test session acceptability and reproducibility were determined using univariate and then multivariate analyses. For univariate analyses, t tests were used for continuous variables and x2 analyses for discrete variables. A p value < 0.05 was considered statistically significant. For the multivariate analyses, logistic regression was used, entering variables with a p < 0.10 in univariate analyses (SAS version 8.2; SAS Institute; Cary, NC). The nonparametric sign test was used to compare paired observations. Finally, we reanalyzed our data by comparing to the 1994 ATS and 2005 ATS/European Respiratory Society (ERS) criteria for reproducibility (0.20 L and 0.15 L, respectively) and start of test acceptability criteria (which utilized only the BEV criteria and not the time to PEF). The study was reviewed by the Human Subjects Review Committee of the North Shore-Long Island Jewish Medical Center.