ABSTRACT
A small device for the oscillatory measurement of both respiratory resistance and residual volume (SIRE-GNOST FD5), introduced in the late 70ies, found wide-spread use. It is working with a constant frequency of 10 Hz and uses a simple signal conditioning to combine the two components of the "complex" respiratory impedance into a single parameter "Ros", thus allowing to plot e.g. Resistance-Volume-Curves.
Subject(s)
Airway Resistance , Lung Diseases, Obstructive/diagnosis , Lung Volume Measurements/instrumentation , Microcomputers , Oscillometry/instrumentation , Residual Volume/instrumentation , Signal Processing, Computer-Assisted/instrumentation , Humans , Pulmonary Ventilation , Reference ValuesABSTRACT
A new isotope method for the determination of the residual volume of the lungs by means of stable, non-radioactive nitrogen isotope 15N is described. Normal air is breathed in a closed system. One part of the air nitrogen is replaced by 15N labelled molecular nitrogen. 15N2 physiologically acts like normal nitrogen so that the so-called secondary effects by using He or H2 are eliminated. By combination of a spirograph and an emission spectrometric 15N analyser the residual volume can be determined and mixing curves can be obtained. The determination of the residual volume in 10 healthy persons gives a range of normal values from 19 to 31% of the total capacity. In three persons with emphysema values from 45 to 50% of the total capacity are found. The analysis of mixing curves leads to additional informations concerning the intrapulmonary gas mixing conditions in the lungs. The relative error of the residual volume determination is about 8%.
Subject(s)
Asthma/diagnostic imaging , Lung Volume Measurements , Pulmonary Emphysema/diagnostic imaging , Residual Volume , Adult , Aged , Humans , Lung Volume Measurements/instrumentation , Middle Aged , Nitrogen Radioisotopes , Radionuclide Imaging , Residual Volume/instrumentation , Total Lung CapacitySubject(s)
Lung Volume Measurements , Lung/physiology , Residual Volume , Adolescent , Adult , Age Factors , Aged , Child , Female , Humans , Lung/diagnostic imaging , Lung Volume Measurements/instrumentation , Lung Volume Measurements/methods , Male , Middle Aged , Plethysmography, Whole Body , Radiography , Reference Values , Residual Volume/instrumentation , Residual Volume/methods , Sex Factors , SpirometryABSTRACT
The helium dilution technique for the measurement of functional residual capacity (FRC) is reviewed with special reference to anaesthesia. A modification is described which permits measurements to be made during intermittent positive pressure ventilation. This modification causes minimal interference with the circuit as it is used for spontaneous respiration. The measuring circuit may be alternated with an open circuit without disturbance of the pattern of breathing (spontaneous or artificial). Potential errors in the measurement of FRC during anaesthesia are considered and assessment of linearity, reproducibility and accuracy is described.
