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Transthoracic Impedance: III. Methodological Studies in Newborn Infants
Author(s) -
VICTORIN LARS,
DAILY WILLIAM,
OLSSON TORSTEN
Publication year - 1970
Publication title -
acta pædiatrica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 115
eISSN - 1651-2227
pISSN - 0803-5253
DOI - 10.1111/j.1651-2227.1970.tb14673.x
Subject(s) - medicine , supine position , electrical impedance , lung volumes , parenchyma , lung , mechanics , acoustics , nuclear medicine , anesthesia , physics , pathology , quantum mechanics
Summary Studies have been performed on the use of the transthoracic impedance measuring tech‐nique on newborn infants. The method permits the examination of the ratio air/blood in the lungs and the analysis of these changes by combination with measurements of variations in the air volume. To make this possible, certain testing conditions must be fulfilled. With the technique used for this investigation, studies should not be started until the electrodes have been applied for fully five minutes and, further‐more, the infant to be examined should be in a quiet state. Through the changes of the hydrostatic pressure conditions in different parts of the lungs t was found that the ratio airlblood in the lung parenchyma is gravity dependent and that the transthoracic impedance technique permits this phenomenon to be studied semi‐quantitatively. The electric fields of the transthoracic leads mainly cover lung parenchyma and therefore are the most suitable for these examinations. With the subject in a supine position, sagittal leads, from the hydrostatic point of view, allow impedance representing the mean of the lung to be recorded, and this lead is con‐sequently used to study the variations with respiration. For longitudinal studies of basic impedance a lead from side to side is employed as this facilitates a stable positioning of the electrodes. The relation between differences in air volume end the magnitude of impedance during respira‐tion has been investigated. Within wide ranges the tidal volume there is a linear relation between these two variables when assessed a t the moments of zero flow a t end‐inspiration and end‐expiration. An analysis of the dynamic course during a breath, however, reveals a discrepancy between change in impedance and air volume, interpreted as caused by simultaneous variation in the blood volume the lungs.