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Title: The effect of body mass and sex on the accuracy of respiratory magnetometers for measurement of end-expiratory lung volumes
Austin Authors: Avraam, Joanne ;Bourke, Rosie;Trinder, John A;Nicholas, Christian L;Brazzale, Danny J ;O'Donoghue, Fergal J ;Rochford, Peter D ;Jordan, Amy S 
Affiliation: Department of Respiratory and Sleep Medicine, Austin Health, Heidelberg, Victoria, Australia
Institute for Breathing and Sleep, Austin Health, Heidelberg, Victoria, Australia
Melbourne School of Psychological Sciences, University of Melbourne, Melbourne, Australia
Faculty of Medicine, University of Melbourne, Parkville, Victoria, Australia
Issue Date: 1-Nov-2016
Date: 2016-10-07
Publication information: Journal of Applied Physiology 2016; 121(5): 1169-1177
Abstract: Respiratory magnetometers are increasingly being used in sleep studies to measure changes in end-expiratory lung volume (EELV), including in obese obstructive sleep apnea patients. Despite this, the accuracy of magnetometers has not been confirmed in obese patients nor compared between sexes. Thus we compared spirometer-measured and magnetometer-estimated lung volume and tidal volume changes during voluntary end-expiratory lung volume changes of 1.5, 1, and 0.5 l above and 0.5 l below functional respiratory capacity in supine normal-weight [body mass index (BMI) < 25 kg/m] and healthy obese (BMI > 30 kg/m) men and women. Two different magnetometer calibration techniques proposed by Banzett et al. [Banzett RB, Mahan ST, Garner DM, Brughera A, Loring SH. J Appl Physiol (1985) 79: 2169-2176, 1995] and Sackner et al. [Sackner MA, Watson H, Belsito AS, Feinerman D, Suarez M, Gonzalez G, Bizousky F, Krieger B. J Appl Physiol (1985) 66: 410-420, 1989] were assessed. Across all groups and target volumes, magnetometers overestimated spirometer-measured EELV by ~65 ml (<0.001) with no difference between techniques (0.07). The Banzett method overestimated the spirometer EELV change in normal-weight women for all target volumes except +0.5 l, whereas no differences between mass or sex groups were observed for the Sackner technique. The variability of breath-to-breath measures of EELV was significantly higher for obese compared with nonobese subjects and was higher for the Sackner than Banzett technique. On the other hand, for tidal volume, both calibration techniques underestimated spirometer measurements (<0.001), with the underestimation being more marked for the Banzett than Sackner technique (0.03), in obese than normal weight (<0.001) and in men than in women (0.003). These results indicate that both body mass and sex affect the accuracy of respiratory magnetometers in measuring EELV and tidal volume.
DOI: 10.1152/japplphysiol.00571.2016
Journal: Journal of Applied Physiology
PubMed URL:
Type: Journal Article
Subjects: End-expiratory lung volume
Respiratory magnetometers
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