Bench Test Evaluation of Adaptive Servoventilation Devices for Sleep Apnea Treatment

Abstract

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...

Patterns of adaptive servo-ventilation settings in a real-life multicenter study: pay attention to volume!

“…In pratice, for ventilation-naive patients, clinicians have the choice between manufacturer default ASV-settings and patient-individualized ASV-settings. There are also no contemporary long-term clinical trials comparing these two modalities, but results from a bench test study are in favor of manually implementing individualized ASV-settings [ 2 ]. For previously CPAP-treated patients, starting the ASV-setting titration at or near the CPAP level was proposed (the EPAP pressure level was adjusted up to a maximum of 10 cmH 2 O and the manufacturer default inspiratory pressure range was allowed to vary between 5 and 10 cmH 2 O above the EPAP) [ 32 ].…”

“…In the latter mode, the EPAP is automatically adjusted by specific manufacturer algorithms meant to correct obstructive disordered breathing [ 3 , 35 ]. To date, in terms of correcting obstructive events, the superiority of the auto-EPAP mode over the fixed-EPAP mode for ASV-device has not been demonstrated [ 2 , 21 , 36 , 37 ]. In this context, it is important to underline that the auto-EPAP-usage by the experts was significantly different between the five clusters, with pairwise comparisons demonstrating a higher auto-EPAP use in the “no cardiopathy”-cluster-3 in comparison with “presence of cardiopathy”- clusters 1 and 2.…”

“…In this context, a specific warning against the use of high expiratory positive airway pressure (EPAP) in reduced LVEF patients exists [ 20 ]. Simultaneously, the auto-EPAP modes developed by ASV-manufacturers are available in daily practice, but lack an evidence base for superiority on fixed-EPAP in clinical and bench studies [ 2 , 21 ], and consensual recommendations are clearly absent. The potential for cardiac output worsening due to specific pressure levels is not always counterbalanced by the neurovegetative response [ 19 , 20 , 22 ] and at-risk patients are likely those with a low pulmonary capillary wedge pressure [ 18 ] and a right ventricular dysfunction [ 19 ].…”

Pressure-Relief Features of Fixed and Autotitrating Continuous Positive Airway Pressure May Impair Their Efficacy: Evaluation with a Respiratory Bench Model

“…Each residual event was scored by considering both the amplitude reduction and the corresponding duration, i.e., ΔV' ≤ 10% of baseline: apnea; 10% < ΔV' ≤ 70%: hypopnea, with a duration ≥ 10 sec. [25][26][27] In addition, the AHI, AI, and pressure data on the device report were also noted for comparison. Results were averaged on two tests for fixed CPAP and on three tests for APAP.…”

Positive pressure therapy induced harm – non-linear, adaptive and maladaptive responses

“…When the ventilator enables stable respiration, cycling between the minimum Page 3 of 8 and maximum pressure support zone is minimal. Bench testing of ASV algorithms show devicespecific response characteristics but stable breathing does not readily occur across a range of simulated central apnea patterns 8. Long range home ASV data assessment (unpublished) shows some degree of persistent pressure cycling in the majority of patients, while the simultaneous device-calculated AHI can be zero or less than one, suggesting overestimation of efficacy and underestimating maladaptive outcomes.ASV's are powerful devices, and if there is patient-ventilatory asynchrony, can induce hypocapnia, excessive cycling of pressures, arousals, distorted flow patterns, and physical discomfort.…”