Views
3 years ago

The Maximum Expiratory Flow-Volume Curve with Air and a Low ...

The Maximum Expiratory Flow-Volume Curve with Air and a Low ...

The Maximum Expiratory Flow-Volume Curve with Air and a Low

The Maximum Expiratory Flow-Volume Curve with Air and a Low-Density Gas Mixture* An Analysis of Subject and Observer Variability N. Berend, M.D.; N. A. Nelson, Ph.D.; I. Rutland, M.B.; G. E. Marlin, M.B., F.C.C.P.; and Ann I. Woolcock, M.D., F.C.C.P. The subject and infra- and inter-observer variability of three measurements derived from the maximal expiratory flow-volume (MEFV) curve with air and heliumoxygen (He02) mixture was determined in ten normal subjects who produced curves in the morning and afternoon of three consecutive days and again on one day a month later. The measurements examined were the maximum flow at SO percent vital capacity (Vtso), the percentage increases in V5o when breathing the He-02 mixture (V5o), and the volume at which the curves on air and He-02 first meet or intersect (VisoV). The v5o and VisoV were shown to have a greater degree of variability than the V50 and, in the case of VisoV, this was contributed to significantly by the observer variability. The within-subject variability of the V5o and VisoV was so great that the usefulness of these tests in following changes in lung function of individual patients must be questioned. T he maximal expiratory flow-volume ( MEFV) curve was introduced as a means of evaluating airway obstruction by Hyatt et al’ in 1958. Since then, it has been used widely in the detection of early airway obstruction.24 More recently, MEFV curves with the subject breathing air and breathing an 80 percent helium- 20 percent oxygen ( He-02 ) mixture have been compared, since it is claimed that by this procedure, it is possible to localize the predominant site of airway obstruction.5’6 The two most commonly derived measurements from these curves are the LV5O ( percent increase in flow at 50 percent vital capacity [\C] after breathing He-O2 ) and the VisoV ( the lung volume at which the MEFV curves with air and He-O2 first meet or intersect). The inter- and intra-subject variability of the maximum flow ( Vmax ) at various lung volumes has been examined.79 However, the variability of the measurements derived from the comparison of curves on air and He-02 has been documented in only one study,1#{176}which showed an identical coefficient of variation ( CV ) for the V50 (Vmax at 50 percent VC ) and zV5o (6 percent ) and a much greater cv for the VisoV ( 105 percent). The significance of changes in the V5o and VisoV in the natural history of disease or with therapy #{176}From the Respiratory Unit, Repatriation General Hospital, Concord, and the Department of Medicine, University of Sydney, New South Wales, Australia. Supported by a Research Grant from the Department of Veterans’ Affairs. Australia. Reprint requests: Dr. Berend, National Jewish Hospital, 3800 East Colfax, Denver 80206 can be calculated only when the variability of these measurements is known. The purpose of this study was to analyze systematically the intra-subject and observer variability of the V5o, V5o, and VisoV to define the usefulness of these tests in caring for patients. MATERIALS AND METHODS Ten healthy, nonsmoking subjects with no previous history of lung disease ( five males, five females; mean age, 28. 1 years; range, 24 to 36 years ) were studied. Although four of the subjects were laboratory personnel, none of the subjects was selected for ability to produce consistent or “good” MEFV curves. No subject had an upper respiratory tract infection in the previous two months or during the course of the study. Informed consent was obtained. The subjects were instructed and seated in an Emerson volume-displacement plethysmograph. Flow was measured with a Fleisch No. 4 pneumotachograph ( linear response to 12 L/sec ) coupled to a Hewlett-Packard Model 267BC pressure transducer, and volume was recorded with a Krogh wedge spirometer. Flow while breathing He-O. was measured after at least three VC inspirations of He-02. This has been shown to produce near complete equilibration in normal subjects. The signal was passed through an attenuator correcting for the change in calibration of the flow signal with the heliumoxygen mixture. The signals were fed into a Sanborn 7700 recording system, and the curves displayed on a Hewlett- Packard 141A storage oscilloscope, with a gain adjusted in individual subjects to make maximum use of the size of the screen. The curves were photographed and the tests repeated until reproducible curves were obtained. The curves with the highest flow rates on air and He-02 were selected. Only curves with less than 5 percent difference in VC between air and He-Ofl were accepted. CHEST, 80: 1, JULY, 1981 MAXIMUM EXPIRATORY FLOW-VOLUME CURVE 23 Downloaded From: http://publications.chestnet.org/ on 05/16/2014

Backward Curved High Pressure Volume Fans - Twin City Fan ...
Measurement Characteristics of Peak Expiratory Flow* - CHEST ...
PEAK EXPIRATORY FLOW RATE IN FLOUR MILL WORKERS ...
Factors affecting peak expiratory flow variability and ... - Thorax
Compliance With Peak Expiratory Flow Monitoring in Home ...
Prediction of Spirometric Forced Expiratory Volume(FEV1) Data ...
The Best Peak Expiratory Flow Is Flow-Limited and Effort ...
helium/oxygen flow volume curves in normal indian males >50 year ...
end expiratory lung volume - Esctaic
Maximum static inspiratory and expiratory pressures with different ...
Orthopnea and Tidal Expiratory Flow Limitation in Patients With ...
Measuring peak expiratory flow - Nursing Times
Peak Expiratory Flow Meter Scale Changes
PEAK EXPIRATORY FLOW RATES IN CHILDREN OF WESTERN ...
PEAK EXPIRATORY FLOW RATE (PEFR)-A Simple Ventilatory ...
The effect of body position on maximal expiratory pressure and flow
A Systematic Review of Serial Peak Expiratory Flow Measurements ...
Peak Inspiratory and Expiratory Flow Meter - University of Wisconsin ...
The Effect on Expiratory Flow Rates of Smoking Three Cigarettes in ...
Measurement of Air Trapping, Intrinsic Positive End- Expiratory ...
Comparison of Serial Monitoring of Peak Expiratory Flow and FEV1 ...
Ambulatory Monitoring of Peak Expiratory Flow* - CHEST Publications
and peak expiratory flow rates among normal - Thorax - BMJ
“Peak expiratory flow rate: Effect of body positions in ... - IJBAMR
The curves "Earliest maximum eclipse" and "Latest maximum eclipse"
Effect of Different Sitting Postures on Lung Capacity, Expiratory Flow ...
KFF/KFG Low-Volume Flow Meter User Instructions - Kobold
Use of Flow-Volume Curves to Predict Oral Appliance Treatme.pdf
The maximum flow problem of uncertain network