Rationale: Adaptive servoventilation devices are marketed to overcome sleep disordered breathing with apneas and hypopneas of both central and obstructive mechanisms often experienced by patients with chronic heart failure. The clinical effi cacy of these devices is still questioned. Study Objectives: This study challenged the detection and treatment capabilities of the three commercially available adaptive servoventilation devices in response to sleep disordered breathing events reproduced on an innovative bench test. Methods:The bench test consisted of a computer-controlled piston and a Starling resistor. The three devices were subjected to a fl ow sequence composed of central and obstructive apneas and hypopneas including Cheyne-Stokes respiration derived from a patient. The responses of the devices were separately evaluated with the maximum and the clinical settings (titrated expiratory positive airway pressure), and the detected events were compared to the bench-scored values. Results: The three devices responded similarly to central events, by increasing pressure support to raise airfl ow. All central apneas were eliminated, whereas hypopneas remained. The three devices responded differently to the obstructive events with the maximum settings. These obstructive events could be normalized with clinical settings. The residual events of all the devices were scored lower than bench test values with the maximum settings, but were in agreement with the clinical settings. However, their mechanisms were misclassifi ed. Conclusion:The tested devices reacted as expected to the disordered breathing events, but not suffi ciently to normalize the breathing fl ow. The device-scored results should be used with caution to judge effi cacy, as their validity depends upon the initial settings. S C I E N T I F I C I N V E S T I G A T I O N SA uto-titrating continuous positive airway pressure ventilators (auto-CPAP) have been developed by manufacturers for the treatment of obstructive sleep apnea with the assumption that lower pressure application would be more comfortable and thus improve compliance and long-term patient outcomes. 1,2However, a recent meta-analysis of auto-CPAP devices has found a limited clinical relevance of only 0.2 h per night of additional use compared to common CPAP devices.3 Clinical studies have recently shown that this limitation may be due to a failure of auto-CPAP devices to reliably estimate the therapeutic pressure in up to 25% of patients. [4][5][6][7] It is noteworthy that bench testing of these devices has predicted these detection and response limitations under simulated obstructive events. [8][9][10][11] More recently, some manufacturers have developed new devices based on adaptive servoventilation (ASV) to treat patients with mixed events of alternating central and obstructive mechanisms as observed in heart failure 12 or so-called complex sleep apnea (CompSA). 13 These ASV devices apply a closed-loop mechanical ventilation, pressure preset, and volume or airfl ow cycled.14 The aim of thes...
This paper presents the design and implementation of IsiMove, a new dynamic posturography platform. It allows the evaluation of the static and dynamic balance of a human placed on a force plate. IsiMove is a robotic platform open kinematic with four degrees of freedom: anteroposterior tilt, mediolateral tilt, vertical rotation, and horizontal translation. It is capable of measuring the displacement of the center of pressure over time, with a resolution of 0.1 mm for each foot and support a human of about 120 kg. IsiMove can generate various types of balance perturbations based on parameters such as direction, amplitude, frequency and shape. In this paper, we will give a description of the mechanisms that constitute our platform. First, the technical specifications of the hardware and software architecture will be presented. Then, we will provide details related to extensive experimental evaluations of the platform in both static and dynamic condition as well as result of postural stability analysis with healthy subjects and stroke patients.
This paper presents a new accelerometer based method for estimating the posture of a subject standing on a dynamic perturbation platform. The induced perturbation is used to study the control mechanisms as well as the balance requirements that regulate the upright standing. These perturbations are translated into different intensity levels of speed and acceleration along longitudinal and lateral directions of motion. In our method, the human posture is modeled by a tridimensional, three-segment inverted pendulum which simultaneously takes into account both the anterior-posterior and medio-lateral strategies of hip and ankle. Four tri-axial accelerometers are used her, one accelerometer is placed on the platform, and the other three are attached to a human subject. Based on the results, the joint angle estimated compare closely to measurements from magnetic encoders placed on an articulated arm joint. The results were also comparable to those found when using a high-end optical motion capture system coupled with advanced biomechanical simulation software. This paper presents the comparisons of our accelerometer-based method with encoder and optical marker based method of the estimated joint angles under different dynamics perturbations.
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