It might seem like pulmonary function technicians do not have to be cheerleaders anymore. Krowka and others (1)found that less blast effort during the onset of the FVC maneuver often resulted in higher FEV.s; now Stoller and coworkers (2) in this issue show that coaching patients to after the first 3 seconds results in higher FVCs. Several studies find that up to one fourth of their subjects are failures'~they cannot meet the stringent ATS acceptability and reproducibility standards. The ATS spirometry standards are currently under review for a new update. Perhaps now is the time to take the F out of FVC and just ask for slow, relaxed exhalation maneuvers. This would provide relief for the hundreds of thousands of persons each year who endure a young person yelling at them to perform strenuous breathing ma neuvers-sometimes to the point of syncope. The Europeans have a better idea: measure both the FEV. and a slow vital capacity, then divide the FEV.by the VC to detect early or mild airflow limitation. After the diagnosis is made, use only the FEV. to follow those with obstruction and only the VC to follow those with restrictive disorders. (Diffusing capacity, if done with a strict quality assurance program, may also be useful initially to aid the differential diagnosis, as well as for followup in patients with interstitial lung disease or pulmonary vascular disease.) In order to obtain an accurate FEV., which can be compared with reference standards, or a reproducible FEV. for valid com parisons with prior or subsequent tests, it remains necessary for technicians to yell BLAST' to prompt a forced effort during the first second of the FVC maneuver. The subject's body language and a sharp and reproducible peak flow provide visual evidence that this occurred (in the absence of an esophageal balloon meas uring the pleural pressure). Maneuvers that do not have a forced, maximal effort during the first second will either under or over estimate the FEV. when compared with spirometry reference studies published since 1980, where submaximal efforts were ex cluded. False-positive interpretations are then common. When 30 technicians recently tested almost 6,000smokers with airways ob struction, paying strict attention to obtaining maximal FVC maneu vers, and then retested them a month later, excellent short-term FEV. reproducibility was demonstrated (3). FEV. reproducibility was not as good in the small group whose best peak flows did not match. So, how should patients be coached after the first few seconds of the FVC maneuver (if a slow VC test is not done)? Stoller and colleagues (2) suggest telling them to relax and blowing instead of the traditional flogging to keep squeezing:' This ad vice is attractive since they are less likely to bend over, Valsalva, turn their face or conjunctivae red, get lightheaded, or worse. In my experience, it is strong young men (who are eager and willing to generate high intrathoracic pressures) in the occupational set ting who are more likely to faint from this procedure, not frail elderly women patients; hence the recommendation to sit during the ma neuver or to place a strong chair without wheels behind them if they stand. Problems with the study by Stoller and coworkers will likely inhibit the ATS committee from quickly recommending the relax ation technique; the hypothesis that the technique would improve between test session FVC reproducibility was not tested. The num ber of subjects was small and not representative of the wide vari ation in those tested each year,including children and the elderly, patients with interstitial lung disease or neuromuscular disorders, relatively healthy workers, and population samples. Only one tech nician used the technique, was not blind to the study hypothesis, most patients performed the standard technique first (were not randomized), and a pneumotach based spirometer without a tem perature sensor was used. The results may not apply to those using volume spirometers where the ATS end-of-test(Ear) criteria is easier to meet since exhaled air is still cooling and contracting inside the bell towards the end of the maneuver (causing a pla teau on the spirogram even while low exhalation flows persist). A third solution to the problems of prolonged exhalations and poorly reproducible FVCs (in those with airways obstruction) has been suggested; redefine calculation of the FVC to occur after a fixed length of time (6, 7, or 10 seconds), instead of requiring a 2-second period of no measurable flow (an EOT plateau) at the end of the test (4). This would probably improve the short-term reproducibility of the FVC,especially when different instruments or technicians were used to perform each test. As usual, more studies are needed, but should be easy considering the volume of spirometry tests done each year.
Search from 250 M+ research papersSearch from 250 M+ research papers
Jun 1, 1999
L Rossi + 4
Open Access