DURU, F., ET AL.: Influence of Posture, Breathing Pattern, and Type of Exercise on Minute Ventilation Es timation by a Pacemaker Transthoracic Impedance Sensor. Previous studies have shown a high correla tion between transthoracic impedance minute ventilation (IMV) determined by a pacemaker sensor and actual minute ventilation (VÉ) measured by standard methods. We hypothesized that several factors (e.g., posture, breathing pattern, and exercise type) could potentially affect the calibration between IMV and V¿. In patients with Medtronic Kappa 400 pacemakers, V¿ (L/min) was monitored using a standard cardiopulmonary metabolic gas analysis system with simultaneous recording of IMV (ohms/min) using DR-180 extended telemetry monitors. Effects of posture and of breathing pattern at rest (19 patients; age 60 ± 13 years) were evaluated by monitoring each patient under three conditions: (a) slow breathing, supine, (b) slow breathing, sitting, and (c) shallow breathing, supine. Calibration at rest was defined as the ratio of IMV to V¿. Effect of type of exercise on calibration compared treadmill versus graded bicycle ergometer exercise (18 patients; age 62 ± 14 years). Calibration during exercise was defined as: (a) "Begin" (the IMV to VÉ ratio at VÉ =10 L/min, the typical VÉ value at beginning of exercise), and (b) slope of the IMV/VÈ regression line. Calibration of IMV/VÉ was significantly smaller for sitting versus supine position (0.7130.177, P < 0.001) and for shallow versus slow breathing (0.7210.373, P< 0.001), and larger for tread mill versus bicycle exercise (Begin: 1.240.43, P = 0.018; Slope: 1.260.42, P = 0.013). In conclusion, pos ture, breathing pattern, and type of exercise affect the IMV estimation of the actual VÉ, possibly by alter ing the static or dynamic geometry (thus, the impedance) of the intrathoracic viscera. (PACE 2000; 23[Pt.II]:1767-1771 pacemaker, rate response, sensors, impedance, minute ventilation

Wavelet-based morphology scores in ICDs may change with various body positions. These variations are relatively minor using the nominal configuration (RV coil-can), as well as by using RV coil-SVC coil and tip-ring. However, morphology scores can vary considerably when SVC coil-can is used; therefore, this configuration should be avoided while using the wavelet algorithm.

Previous studies showed that transthoracic impedance minute ventilation (IMV), as measured by a pacemaker sensor, is closely correlated to actual minute ventilation (VE) determined by standard methods. The aim of this study was to analyze the changes in the calibration between IMV and VE at rest and during exercise over time. Fifteen patients (age 60 +/- 13 years) with Medtronic Kappa 400 pacemakers completed a baseline visit followed by two visits separated by 1 month and 1 week, respectively. In each patient, VE (L/min) was monitored at rest in the supine and sitting positions and during graded bicycle ergometer exercise using a standard cardiopulmonary metabolic gas analysis system with simultaneous recording of IMV (omega/min) using DR-180 extended telemetry monitors. Calibration at rest was defined as the ratio of IMV to VE, calculated from 1-minute average values in the supine and sitting positions. Calibration during bicycle exercise was defined as intercept (IMV value at VE = 10 L/min-typical VE value at beginning of exercise), and slope of the IMV/VE regression line. The calibration of IMV showed individual variability over time. The magnitude (absolute value) of observed fractional changes in calibration at 1 month was 0.23 +/- 0.20 (rest-supine), 0.20 +/- 0.15 (rest-sitting), 0.18 +/- 0.19 (exercise-intercept), 0.28 +/- 0.35 (exercise-slope), and 0.18 +/- 0.15, 0.15 +/- 0.09, 0.28 +/- 0.39, and 0.27 +/- 0.15, respectively, at 1 week. The magnitude of change at 1 month was not statistically different from the magnitude of change at 1 week. In conclusion, the calibration of IMV, as measured by a pacemaker sensor, versus actual VE may demonstrate variability. However, this study also suggests that the observed changes are not cumulative over time. These results have implications for patient monitoring applications using these sensors and for development of future pacemaker rate response algorithms.

MRI findings, as well as X-ray findings, do not correlate with the subjective and objective functional outcomes after surgical treatment of transscaphoid perilunate fracture dislocations. It can be assumed that SL ligament lesions seen in MRI play a major role over the long term course.

No abstract