Observer variation in spirometry.
The intra-observer and inter-observer variation associated with clinical spirometry was statistically analyzed. The technical errors for the MEFR and MMF measurements were large enough to question their clinical reliability, especially in borderline instances. Measurement differences between two observers, as in this study, are statistically significant. This observation has special meaning for groups engaged in epidemiologic studies. Significant inter-individual variation will diminish the quality of pooled results.
Daily spirometric variability: normal subjects and subjects with chronic bronchitis with and without airflow obstruction.
To determine the daily variability of spirometry, we performed spirometry on five consecutive days on 15 normal subjects and on 24 patients with chronic bronchitis. The patients with chronic bronchitis were divided into the following two groups: 13 with chronic airflow obstruction (forced expiratory volume in 1 s [FEV1] 80%, FEV1/forced vital capacity [FVC] ratio less than 75%) and 11 without airflow obstruction (FEV1 and FVC greater than 80%0. We attempted to control most of the factors known to affect spirometric variability. Our results indicate that the day-to-day FEV1 has to change by 17% and the FCV by 15% in patients with airflow obstruction before the change should be considered significant. In patients with nonobstructive chronic bronchitis or in normal subjects, a greater than 5% change should occur in FEV1 and FVC before considering the change to be significant.
Ventilatory function tests; voluntary ventilation capacity.
An important element in any battery of tests designed to analyze the functional status of an organ is a quantitative measure of the capacity of that organ to carry on its specific function. In testing the functional status of the pulmonary bellows, therefore, a quantitative measure of its capacity to produce an alternating flow of air in and out of the lungs is desirable. Several methods have been proposed for determining the ventilatory capacity of the lungs. Early attempts to utilize the vital capacity, which is essentially a static volume, as a test of ventilation capacity, which is a dynamic rate, met with little success (1-4). Later attempts to utilize the maximum ventilatory response to CO2 inhalation (5-8) or to severe exercise (1, 3, 7, 8) have likewise proved unsatisfactory. Both are distressing and even dangerous to persons who are ill. Furthermore, both yield ambiguous results for they confound ventilation capacity and sensitivity to CO2 in the one case and ventilation capacity and cardiovascular capacity in the other. Finally, neither the 70 L./min. maximum response to CO, nor the 120 L./min. maximum response to exhausting exercise approaches the capacity of the pulmonary bellows. The most promising method of determining ventilation capacity depends upon voluntarily ventilating the lungs at the maximum rate. This procedure was first explored by Hermannsen (7) and further developed by Cournand, Richards and Darling (9). It has had a variety of names, the most common in German being "voluntary maximum ventilation" and in English "maximum breathing capacity." The latter term, however, has also been applied to the exercise procedure. In order to reduce confusion and ambiguity the following self-evidence terminology is recommended: voluntary ventilation capacity, exercise ventilation capacity, and CO2 ventilation capacity. The purpose of the present study was to standardize the procedure for measuring the voluntary ventilation capacity, to determine its reliability, and to establish normal values.