Respiratory monitoring by inductive plethysmography in unrestrained subjects using position sensor-adjusted calibration.
BACKGROUND
Portable respiratory inductive plethysmography (RIP) is promising for noninvasive monitoring of breathing patterns in unrestrained subjects. However, its use has been hampered by requiring recalibration after changes in body position.


OBJECTIVE
To facilitate RIP application in unrestrained subjects, we developed a technique for adjustment of RIP calibration using position sensor feedback.


METHODS
Five healthy subjects and 12 patients with lung disease were monitored by portable RIP with sensors incorporated within a body garment. Unrestrained individuals were studied during 40-60 min while supine, sitting and upright/walking. Position was changed repeatedly every 5-10 min. Initial qualitative diagnostic calibration followed by volume scaling in absolute units during 20 breaths in different positions by flow meter provided position-specific volume-motion coefficients for RIP. These were applied during subsequent monitoring in corresponding positions according to feedback from 4 accelerometers placed at the chest and thigh. Accuracy of RIP was evaluated by face mask pneumotachography.


RESULTS
Position sensor feedback allowed accurate adjustment of RIP calibration during repeated position changes in subjects and patients as reflected in a minor mean difference (bias) in breath-by-breath tidal volumes estimated by RIP and flow meter of 0.02 liters (not significant) and limits of agreement (+/-2 SD) of +/-19% (2,917 comparisons). An average of 10 breaths improved precision of RIP (limits of agreement +/-14%).


CONCLUSIONS
RIP calibration incorporating position sensor feedback greatly enhances the application of RIP as a valuable, unobtrusive tool to investigate respiratory physiology and ventilatory limitation in unrestrained healthy subjects and patients with lung disease during everyday activities including position changes.
Pulmonary Division, Department of Internal Medicine, University Hospital Zurich, CH-8091 Zurich, Switzerland.
Gregor
G
Brüllmann
Karsten
K
Fritsch
Robert
R
Thurnheer
Konrad E
KE
Bloch
D000328:Adult; D000368:Aged; D002138:Calibration; D016022:Case-Control Studies; D006801:Humans; D008875:Middle Aged; D010993:Plethysmography, Whole Body / Q000295:instrumentation / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D013990:Tidal Volume; D055815:Young Adult