Montreal electronic artificial urinary sphincters: Our futuristic alternatives to the AMS800™

Abstract

Introduction: We aimed to present three novel remotely controlled hydromechanical artificial urinary sphincters (AUSs) and report their in-vitro and ex-vivo results.

Methods: We successively developed three distinct hydromechanical AUSs on the basis of the existing AMS800^™ device by incorporating an electronic pump. No changes were made to the cuff and balloon. The AUS#1 was designed as an electromagnetically controlled device. The AUS#2 and AUS#3 were conceived as Bluetooth 2.1 remotely controlled and Bluetooth 4.0 remotely-controlled, adaptive devices, respectively. In-vitro experiments profiled occlusive cuff pressure (OCP) during a complete device cycle, with different predetermined OCP. Ex-vivo experiments were performed on a fresh pig bladder with 4 cm cuff placed around the urethra. Leak point pressure with different predetermined OCP values was successively measured during cystometry via a catheter at the bladder dome.

Results: Our in-vitro and ex-vivo experiments demonstrated that these three novel AUSs provided stable and predetermined OCP - within the physiological range - and completely deflated the cuff, when required, in a limited time compatible with physiological voiding cycles.

Conclusions: Our three novel, remotely controlled AUSs showed promising results that should be confirmed by in-vivo experiments focusing on efficacy and safety.

Fig. 1

Simplified schemas. (A) AMS800™; (B) AUS#1: Replacing the manual pump; (C) AUS#1: Connected in parallel with the manual pump; (D) AUS#2: Replacing the manual pump; (E) AUS#2: Connected in parallel with the manual pump; (F) AUS#3: Replacing the manual pump.

Fig. 2

System operation: (A) AUS#1; (B) AUS#2; (C) AUS#3.

Fig. 3

In-vitro assessment of the AUS#1 occlusive cuff pressure (OCP) profile: (A) during a complete device cycle; and (B) during the cuff deflation. Notes: [1] “Closed” state: Initially, the pressure within the system is balanced. The cuff is full with fluid and at pressure-regulating balloon’s (PRB) pressure. [2] Cuff deflation: To turn on the pumping system, the magnet is placed close to the control unit. Then the OCP starts to drop. During the two seconds of pumping, the effect of a displacement pumping mechanism is visible (B). [3] “Open” state: The OCP is below the atmospheric pressure. [4] Cuff inflation and return to “closed” state: Under the PRB’s pressure, the fluid gradually flows back from the balloon to the cuff through the hydraulic resistor. After 2–3 minutes, the pressure between the balloon and the cuff is completely balanced, closing the urethra consequently.

Fig. 4

In-vitro assessment of the AUS#3 occlusive cuff pressure (OCP) profile. (A) OCP evolution recorded during a complete cycle; (B) Recorded OCP when the AUS#3 device is “closed.” Notes: [1] Stand-by mode: The control unit, including the pressure sensor, is powered down. No pressures are recorded. Only the transceiver is kept in a stand-by mode, waiting for connection. [2] Bluetooth connection: As soon as a connection is established (around two seconds after request), the control unit is powered up and the sensor starts measuring the OCP. [3] Cuff deflation (to “open” state): As a consequence of the cuff opening request, the valve is opened generating a passive fluid transfer from the cuff to the balloon, responsible for a fast OCP decrease. The null pressure within the cuff is kept as long as programmed (here, 10 seconds). [4] Cuff inflation (to “closed” state): As soon as the cuff closing is requested, the OCP regulation process starts and the pumping system quickly rises the OCP. The pressure is kept at the requested set point value for a programmed period (here, six seconds), after which the valve is finally closed. During this six-second period, the pressure sensor detects impulses engendered by the centrifugal pump. [5] Valve closing and return to stand-by mode: By blocking fluid transfer, the closed valve passively keeps the cuff constantly pressurized and allowed the “control” unit, including the pressure sensor, to power down for energy-saving. At the end, the transceiver comes back to stand-by mode, waiting for another connection.

Fig. 5

Ex-vivo assessment of the AUS#1 occlusive cuff pressure (OCP) using the leak point pressure (LPP). Notes: [1] Intravesical pressure is increased up to 50 cmH2O thanks to saline solution infusion. [2] Saline solution infusion is stopped and intravesical pressure is manually raised to reach the LPP. [3] Manual pressures are stopped and saline solution is infused again. [4] Magnet is placed close to the reed switch to deflate the cuff.

Fig. 6

Ex-vivo assessment of the AUS#3 occlusive cuff pressure (OCP) using the leak point pressure (LPP).