Mechanical Medical Device for Generating Vibration and Stimulation of the Neuron Pathways

S S symmetry

Article Mechanical Medical Device for Generating Vibration and Stimulation of the Neuron Pathways

Antonín Svoboda 1,*, Milan Chalupa 1 and Tat’ána Šrámková 2,3

1 Faculty of Mechanical Engineering, University of Jan Evangelista Purkynˇein Ústí nad Labem, Pasteurova 1, 400 96 Ústí nad Labem, Czech Republic; [email protected] 2 Department of Urology, First Faculty of Medicine, Charles University in Prague and General University Hospital, Prague 2, 121 08 Prague, Czech Republic; [email protected] 3 Department of Traumatology, Faculty of Medicine, Masaryk University, Ponávka 139/6, 662 50 Brno, Czech Republic * Correspondence: [email protected]

Abstract: This article describes a medical device uses precisely generated vibrations to obtain genetic material (sperm) in injured men, tetraplegics, and paraplegics. A signiﬁcant advantage is the absence of general anesthesia of the patient. The DC motor of a medical device works with a safe voltage powered by rechargeable or AA cells. The principle of generation of vibration is a crank mechanism. Rotation of the ﬂywheel is converted to rectilinear reciprocating motion. The amplitude is set in the range between 1–4 mm and the frequency is controlled by the RPM of the DC motor. If the stimulation will be followed preciously with the methodology, the process will be completed within 12 min from the beginning of stimulation. The success rate of the device is in the range between 65–85% depending on the patient’s condition and the extent of the spinal cord lesion. The measurement of sinusoidal oscillations was performed by using a stand in which the device was mounted. The amplitude was measured with an accelerometer and then mathematically converted by software Matlab and MS-Excel to the magnitude of the deviation in mm. Measurements have shown that the proposed design meets the requirements for amplitude and frequency.

Citation: Svoboda, A.; Chalupa, M.; Keywords: paralysis; reﬂex ejaculation; vibrostimulation; crank mechanism; accumulator; electrical Šrámková, T. Mechanical Medical motors; electrical motor regulator Device for Generating Vibration and Stimulation of the Neuron Pathways. Symmetry 2021, 13, 62. https:// doi.org/10.3390/sym13010062 1. Introduction

Received: 3 December 2020 According to multiple professional medical journals, human reproduction has en- Accepted: 28 December 2020 countered some problems, especially in terms of the decrease of sperm quality. This issue Published: 31 December 2020 has been observed since the 19702010039s. Busy and stressful lifestyles as well as sep- aration from traditional life and nature have been associated with this decline. In the Publisher’s Note: MDPI stays neu- last century, 60 million was considered the average amount of mobile sperm for males. tral with regard to jurisdictional clai- Currently, the standard values of spermiogram are based on the 2010 norm according ms in published maps and institutio- to WHO (World Health Organization)—volume—1.5 mL and more; pH: 7.2 and more; nal afﬁliations. concentration: At least 15 million per 1 mL of the semen—total at least 39 million; mobility— minimally 40% of mobile sperm and 32% of progressively moving sperm; and morphology: Minimally 4% of the normal build. The transport of the semen into the Centre of Assisted Reproduction (CAR) must be done within an hour [1]. Copyright: © 2020 by the authors. Li- In the Czech Republic, on average 150–200 people fall victim to a spinal cord injury censee MDPI, Basel, Switzerland. every year and a third of these are women. The most common mechanisms of injury are This article is an open access article a car accident and falling from height [2]. From the severity perspective, it is the priority distributed under the terms and con- group of patients who require long-term medical care and rehabilitation, the complex ditions of the Creative Commons At- tribution (CC BY) license (https:// approach of various professionals and specialists such as a traumatologist, neurologist, creativecommons.org/licenses/by/ urologist, intern, rehabilitation physician, sexologist, and psychologist. Patients with a 4.0/).

Symmetry 2021, 13, 62. https://doi.org/10.3390/sym13010062 https://www.mdpi.com/journal/symmetry Symmetry 2021, 13, 62 2 of 11

spinal cord injury are treated by spinal units, which are part of traumacentres. At the moment there are four spinal units in the Czech Republic located in Prague, Liberec, Ostrava, and Brno. The first step in treatment is a surgical decompression of the spinal cord. On the first postsurgery day, the process of complex rehabilitation and resocialisation begins. The rehabilitation of the paralysed patients continues in the rehabilitation centres and their goal is full adaptation to a wheelchair, acceptance of permanent disability, and return to family, work, and social life. In regard to the care of disabled patients, the financial costs are high, especially in the first year following injury. The lifelong expenses of a man who has become disabled at the age of 25 can go beyond 20 million Czech crowns [1,3,4]. Sexual dysfunction, sexual life, and reproduction are affected by spinal injury. The disabled patients suffer from erectile dysfunction (ED) and the condition is also connected with the change of erogenous zones, non-ejaculation with the absence of orgasm, or the change of quality of orgasm, spermatogenesis disorder, endocrine dysfunction, lowered libido, and decrease or loss of sexual satisfaction. Sexual desire is decreased by the injury and that leads to a lower frequency of sexual intercourses ranging from one per week to one per month. Erogenous zones change, and while the penis loses its dominant role as opposed to in a healthy male individual, areas with preserved sensitivity such as nipples, ear lobes, nape, and mouth become more prominent. The nature of an orgasm changes as it is not accompanied by ejaculation. A number of males describe it as a pressure in their head. Some paraplegics are able to evoke orgasm-like feelings preceding the injury, which is called a ‘psychogenic orgasm’ and the orgasm experienced simultaneously with the partner is called a ‘para-orgasm’ [2–5]. Nowadays, two of the most common and successful methods of retrieving sperm from disabled males are rectal electrostimulation and vibrostimulation. Prior to vibrostimulation or electrostimulation, the patient is thoroughly informed after which they sign the consent of acknowledgment [4]. Vibrostimulation, penile vibrostimulation (PVS) is recommended in the first line of retrieval of sperm from men with postinjury non-ejaculation. Using a penile vibrator is successful with men with a lesion segment T8 of the spinal cord. Technical parameters of the device are as follows: Reachable frequency 100 Hz and amplitude 2.5 mm. Vibrostimulation is performed while sitting down in a wheelchair. The vibrostimulator is placed on the glans or frenulum of the penis. Stimulation takes between a 2–3 min to 1–2 min intermission but the maximum number of repetitions is three. Ejaculation tends to be accompanied by spasms of the abdominal and lower limb muscles. Contraindica- tions of PVS could be skin inflammatory changes on the penis, uncorrected hypertension, heart disorders, and a high risk of onset of autonomous dysreflexia. For some time after the injury (less than 18 months), patients tend to have problems to achieve ejaculation using PVS, which is considered noninvasive compared to electro-ejaculation. PVS is a preferred method by the patients as couples can use it for home insemination.

2. Experimental Section An electrodynamic vibrator would probably be the most suitable solution [6]. However, the market does not offer a suitable type and size of the vibrator, which could be used in this case. If we were focusing on the development and production of the electrodynamic solution in its miniature version, it would be pointless without serial manufacturing. Another way to stimulate nerve endings via vibration is using a piezoelectric vibrator. This solution may first appear as optimal and final. On the other hand, because of its construction this kind of generator is not capable of reaching the required deviations (amplitude) in the 1–4 mm range. The crank mechanism construction then appears to be the optimal choice. While using the crank mechanism, it is possible to reach great accuracy with the set amplitude, which corresponds with the specified conditions in the 1–4 mm range. The amplitude is controlled by the eccentricity of the connecting rod pin from the rotating axis of the flywheels and frequency as well as by the spin speed of the electromotor [7]. To maintain the specified conditions, the design of the device was presented in five variants, while every variant had a different eccentricity, Symmetry 2021, 13, 62 3 of 11 Symmetry 2021, 13, x FOR PEER REVIEW 3 of 11 Symmetry 2021, 13, x FOR PEER REVIEW 3 of 11 Symmetry 2021, 13, x FOR PEER REVIEW 3 of 11 which corresponded to the 1–5 mm amplitude. All parts of the device were checked by themechanism numeric calculation.Figure 1. was The checked crank mechanismby calculation Figure on testing1. was the checked stresses, by calculationbearing, and on mechanism Figure 1. was checked by calculation on testing the stresses, bearing, and bruisingmechanism of Figure the connecting 1. was checked rod and by calculationpins. The onmaximum testing the applied stresses, force bearing, on the and stimulating testingbruising the of stresses, the connecting bearing, rod and and bruising pins. The of maximum the connecting applied rod force and on pins. the stimulating The maximum platebruising is 10of theN (Figure connecting 2) and rod andbecause pins. ofTh thise maximum negligible applied force, force detailed on the calculationsstimulating were not appliedplate is force10 N (Figure on the stimulating2) and because plate of this is 10 negligible N (Figure force,2) and detailed because calculations of this negligible were not force, detailedcarriedplate is 10 out calculations N (FigureFigure 2)3. and were[8]. because not carried of this negligible out Figure force,3.[ detailed8]. calculations were not carriedcarried out out Figure Figure 3. 3.[8]. [8].

Figure 1. Crank mechanism of the vibration generator. Figure 1. Crank mechanism of the vibration generator. FigureFigure 1. Crank mechanismmechanism of of the the vibration vibration generator. generator.

Figure 2. Analysis of the applied forces.

FigureFigur 2. Analysise 2. Analysis of the appliedof the applied forces. forces. Figure 2. Analysis of the applied forces.

Figure 3. Bearing calculations of the connecting rod and cutting and bruising test of the pin.

FigureFigure 3. 3.Bearing Bearing calculationscalculations of the connecting rod rod and and cutting cutting and and bruising bruising test test of of the the pin. pin. Symmetry 2021, 13, 62 4 of 11

Calculation of critical force in Figure2:

2 π2·E·J π2·2.1·105· π·0.004 = min = 64 = =. Fkr 2 2 132, 648.68 132, 650 N (1) lred 0.0125

F < Fkr → 10N < 132, 650 N (2)

where: Fkr—critical force at the stress rupture (N), E—tensile modulus (MPa), lred—reduced 3 length of the rod (m), and Jmin—quadratic module of the cross-section—(smallest) (m ) The calculation matched the requirements: The operational value is 13,265 times lower than the critical pressure. The test of the pin cutting on two levels is:

F τ = ≤ τ (3) s 2·S sD

Re = 0.8·Rm (4)

τsD = 0.6·0.8·Re = 0.6·0.8·40 = 19.2 MPa (5) S = π·r2 = π·0.0022 = 1.26·10−5 m2 (6) F 10 . τs = = = 0.3968 = 0.4 MPa (7) 2·S 2·1.26·10−5

τs < τsD → 0.4 MPa < 19.2 MPa (8) The calculation matched the requirements. The operational value is 48 times lower than the critical pressure. The bruising test of the pin with the fork is:

F p = ≤ p (9) 2·d·a DOV 10 p = = 1.88 MPa (10) 2·0.004·1.5

p < pD → 1.88 MPa < 35 MPa (11) The calculation matched the requirements. The operational value is 19 times lower than the critical pressure. The bruising test of the pin of the connecting rod is:

F p = ≤ p (12) d·a DOV 10 p = = 3.75·10−6 MPa (13) 0.004·0.0015 −6 p < pD → 3.75·10 MPa < 35 MPa (14) The calculation matched the requirements. The operational value is 131,250,000 times lower than the critical pressure. The dimensions calculation of the medical device was derived from the dimensions of the electromotor and the wall thickness of the device. . D = Dem + 2·tt = 27.6 + 2·5 = 37.6 = 40 mm (15)

where is: Dem—diameter of the electromotor (mm), and tt—wall thickness of the device (mm) Symmetry 2021, 13, 62 5 of 11

The body of the device must be able to function even with mechanical stresses caused by vibrations. A PLA plastic type was used as the designed material for the prototype of the device. PLA is a biologically degradable plastic as a result of its natural origin from corn, sugar cane, or potatoes. In regard to longevity of the device, materials such as PET or PETG would be more suitable material solutions for the prototype since they are able to withstand greater mechanical stresses. However, since the focus is to verify the functionality of the device, it is not necessary to concentrate on the slight mechanical differences of the materials of the prototype.

3. Results The body of the medical device was designed in a way that it would withstand the vibrations generated by the device and fall from common heights to 1.5 m above the ground [9]. The biodegradable plastic PLA was used to create the prototype with regard to the environment. The strength of this plastic is that it is able to withstand the testing needs of the prototype. The calculation presents the bulkiness of the crank mechanism with safety and technological reserves with the sum of the length of the electromotor, electronics, and accumulators.

L = Lkm + Lem + Le + La + 2·tt = 65 + 55 + 95 + 2·5 = 225 mm (16)

where: Lkm—length of the crank mechanism including technological and safety reserves (mm), Lem—length of the electromotor (mm), Le—length of the electronics (mm), La—length of the accumulators (mm), and tt—wall thickness of the device (mm) Regarding the current consumption of the electromotor (current draw), an accumulator with hard discharging characteristics was designed. A LiFe (lithium–iron–phosphate) accumulator type was chosen because of its reliability and lifespan. It does not have any deficiencies compared to its predecessors and offers a bigger capacity with smaller dimensions. The main task of controlling electronics is to secure the flawless operation of the device both without any load and under load while being applied to the patient. The next task is to inform the staff of the charging state of the accumulator, its overload, forced cessation of the device, or overheating of the motor [7]. The electronics of the device were designed so that the crank mechanism with the connected electromotor was able to maintain the set parameters under stress within the frequency range of 60–120 Hz (i.e., 4800–7200 RPM). The frequency is adjustable within 5 Hz steps [10]. The last function of the controlling electronics is inductive charging. The device was designed to be resistant to gushing water, in other words, IP coverage-protected from gushing water. Water is rushed through a 6.3 mm jet at all angles with a flow of 12.5 L per min and with a pressure of 30 kN/m2 for at least three minutes from a three-metre distance [11]. The controlling electronics contain an inductive part for accumulator charging, which means the device was designed for con- tactless inductive charging. The charging is signalled by a green LED diode, which flashes during charging and as soon as the charging process is finished, it shines green. For the experimental measuring, a simpler and, most importantly, cheaper model of the controlling electronics was developed. This model retroactively checks the speed of the electromotor. The frequency or speed is set by using a calibrated potentiometer and there is a scale on the body of the device for setting an accurate frequency. After being switched on, the electromotor maintains a constant set speed with or without a load on the device [7]. The controlling electronics of the medical device have the following properties: Dimensions of 55 × 27 mm; power supply of 5–12 V; and nominal voltage of the motor of 7.2 V. The regulated current is applied by using a power transistor with a cooler (max. 8 A, short-term 20 A) as shown in Figures4 and5. Symmetry 2021, 13, x FOR PEER REVIEW 6 of 11 SymmetrySymmetry 20212021, 13, 13, x, 62FOR PEER REVIEW 6 of6 of 11 11

Figure 4. Controlling electronics of the medical device FertEx CM—design of the printed connec- FigureFigure 4. 4. ControllingControlling electronics of of the the medical medical device device FertEx FertEx CM—design CM—design of theof the printed printed connection. connection. tion.

FigureFigureFigure 5. 5. 5.Controlling ControllingControlling electronics electronics electronics of of the the medical medicalmedical devicedevice FertEx FertExFertEx CM—stocking CM—stockingCM—stocking with with components. components.

AfterAfterAfter considering considering considering the the aspects aspects of of the the availableavailablavailable electromotorselectromotors in in this thisthis category, category,category, an anan elec- elec-elec- tronicallytronicallytronically switched switched switched (brushless) (brushless) (brushless) electromotorelectromotor electromotor waswas was designed. designed. The The reason reason forfor for thisthis this choicechoice choice was was itsitswas affordability, affordability, its affordability, lifespan,lifespan, lifespan, andand andsparklessparkles sparkles operation,operation, operation, which which could could otherwiseotherwise otherwise causecause cause thethe the dis-dis- ruptionruptiondisruption of of some some of some electronic electronic electronic medicalmedical medical devices.devices. devices. ThThe The price price of the of theelectronically electronically switchedswitched switched elec-elec- tromotortromotorelectromotor is is from from is fromfive five to ﬁveto 10 10 to times times 10 times higherhigher higher ththanan than of a of standard a standard commutator commutator electromotor,electromotor, electromotor, butbut thethebut price price the is price is balanced balanced is balanced out out byby out itsits by reliabilityreliability its reliability andand longerlonger and longer lifespan. lifespan. From the Fromthe availableavailable the available motors,motors, thethemotors, SPEED SPEED the 500 500 SPEED or or SPEED SPEED 500 or 400 SPEED400 seriesseries 400 ofof series electrelectr ofomotorsomotors electromotors can be can considered. be considered. TheThe comparisoncomparison The com- ofofparison the the measured measured of the measured values values of of valuesthe the current current of the drawdraw current ofof drawthe mentioned of the mentioned models modelsisis presentedpresented is presented in in Tables Tables in Tables1–3 . Based on the measurements listed below, it is apparent that the SPEED 1–3.1–3. Based Based on on thethe measurementsmeasurements listedlisted below,below, itit is apparent thatthat thethe SPEEDSPEED 400400 seriesseries 400 series electromotor was picked as optimal. Its parameters, namely, its output and electromotorelectromotor was was picked picked as as optimal. optimal. ItsIts paraparameters,meters, namely, its output andand currentcurrent draw,draw, current draw, fully satisfy the requirements demanded by the device. fullyfully satisfy satisfy the the requirements requirements demandeddemanded byby thethe device.device.

TableTable 1. 1. Results Results of of the the measurement measurement ofof thethe currentcurrent draw of the electromotor—measured withoutwithout loadload on on the the device: device: Messcontrol Messcontrol M–3800 M–3800 (S/N:(S/N: 225767)225767),, poweredpowered by a laboratorylaboratory stabilisedstabilised sourcesource (S/N:(S/N: 2584) 2584). .

TestTest Speed Speed RPM RPM Voltage Voltage (V) (V) Current Current (A)(A) El.El. MotorMotor Type 400 Current (A)(A) El.El. MotorMotor TypeType 500 500 48004800 3.353.35 1.151.15 2.052.05 52005200 3.493.49 1.561.56 2.332.33 55005500 3.713.71 1.841.84 2.692.69 56005600 3.823.82 1.921.92 2.952.95 Symmetry 2021, 13, 62 7 of 11

Table 1. Results of the measurement of the current draw of the electromotor—measured without load on the device: Messcontrol M–3800 (S/N: 225767), powered by a laboratory stabilised source (S/N: 2584).

Current (A) El. Current (A) El. Test Speed RPM Voltage (V) Motor Type 400 Motor Type 500 4800 3.35 1.15 2.05 5200 3.49 1.56 2.33 5500 3.71 1.84 2.69 5600 3.82 1.92 2.95 5900 4.09 2.05 3.12 6100 4.32 2.21 3.45 6400 4.48 2.33 3.91 6900 4.69 3.49 4.38 7200 4.9 3.55 4.94

Table 2. Comparison of advantages and disadvantages of a medical device FertEx CM.

Advantages of Device Disadvantages of Device Own battery operation Charging of device Vibration in the hands Safe voltage of a doctor Limited battery life Long operation time (can be replaced) Mobility of the device Self-service of the patient The same device is not on the market at the moment Water proof Resistant to common disinfections in hospitals and autoclaves

Table 3. Comparison of advantages and disadvantages of FertEx CM and similar devices available on the market.

Similar Devices Device FertEx CM Available on the Market Up to three times the battery life Low battery life Fast charging 3 h Standard charging 16 h Low price available to all patients Higher price Long life of motor Used motors have a short service life The possibility of charging in the car when moving the doctor Unable to charge in the car to the patient One or two Only one vibration mechanism vibration mechanisms One vibration mechanism and long-life motor One or two engines with a shorter service life Resistant to common disinfections in hospitals Unknown and autoclaves Possibility of disinfection in the autoclave It must not be exposed to high temperatures

The crank mechanism method was veriﬁed in the laboratory with regard to patient safety and the emergence of own frequency or resonate. With experimental measurements, the maximum values of amplitude at frequency were found. DC engine was powered by a stabilized source and were measured engine RPM, the electric current (A), and frequency (Hz). After complete measuring, data were recalculated and placed through conversion by software Matlab for a veriﬁcation of amplitude in (mm). Using the same software, the data was published on graphs as shown in Figures6–8. SymmetrySymmetry 20212021, 13, 13, x, FOR 62 PEER REVIEW 8 of8 of 11 11 Symmetry 2021, 13, x FOR PEER REVIEW 8 of 11

Figure 6. Acceleration in the x direction-measurements at 4800 RPM was to achieve the maximum Figure 6. Acceleration in the x direction-measurements at 4800 RPM was to achieve the maximum Figureacceleration 6. Acceleration value of in0.3549 the x m/s direction-measuremen2 in frequency 1040 Hzts at and 4800 4800 RPM RPM was of to the achieve DC engine. the maximum This meas- acceleration value of 0.3549 m/s2 2 in frequency 1040 Hz and 4800 RPM of the DC engine. This mea- accelerationurement shows value that of 0.3549 neither m/s resona in frequencynce nor natural 1040 Hz frequency and 4800 occurs. RPM of the DC engine. This meas- urementsurement shows shows that thatneither neither resona resonancence nor nornatural natural frequency frequency occurs. occurs.

Figure 7. Acceleration in the x direction—measurements at 5160 RPM was to achieve the maxi- FiguremumFigure 7.of Acceleration acceleration 7. Acceleration valuein the in ofxthe direction—measurem 9.1390 x direction—measurements m/s2 in frequencyents 172 at 5160 Hzat in RPM 51605160 was RPMRPM to wasofachieve the to DC achieve the engine. maxi- the This max- mum of acceleration value of 9.1390 m/s2 in frequency 172 Hz in 5160 RPM of the DC engine. This measurementimum of acceleration shows that value neither of 9.1390resonance m/s nor2 in natural frequency frequency 172 Hz occurs. in 5160 RPM of the DC engine. measurement shows that neither resonance nor natural frequency occurs. This measurement shows that neither resonance nor natural frequency occurs. SymmetrySymmetry 20212021, 13, 13, x, FOR 62 PEER REVIEW 9 of9 of 11 11

FigureFigure 8. 8.AccelerationAcceleration in in the the x xdirection—measurem direction—measurementsents at at 3060 3060 RPM RPM was was to to achieve achieve the the maxi- maximum mum of acceleration value of 0.3892 m/s2 in frequency 52 Hz in 3060 RPM of DC engine. This of acceleration value of 0.3892 m/s2 in frequency 52 Hz in 3060 RPM of DC engine. This measurement measurement shows that neither resonance nor natural frequency occurs. shows that neither resonance nor natural frequency occurs.

4.4. Disc Discussionussion TheThe most most important important feature feature of of the the designed designed device FertEx CMCM forfor PVSPVS isis the the option option to tosafely safely retrieve retrieve sperm sperm from from paralysed paralysed males males and and the the option option to to have have their their own own biological biological off- offspring.spring. This This obtaining obtaining is is also also possible possible to doto do at home at home after after a doctor a doctor evaluation. evaluation. The retrievedThe re- trievedsperm sperm is then is required then required to be transported to be transported by CAR. by CAR. Another Another possibility possibility is to impregnate is to impreg- the natepartner the partner immediately immediately after by after using by ausing ‘Baby a made‘Baby home’made home’ method method (artificial (artificial insemination), insemination),when the when partner the partner inserts theinserts semen theinto semen her into vagina. her vagina. BasedBased on on experience, experience, the the spermiological spermiological pa parametersrameters and and especial especiallyly sperm sperm mobility mobility areare better better when when obtaining obtaining PVS. PVS. PVS PVS is is recommended recommended in in the the first first line line for for sperm sperm retrieval retrieval forfor males males with with postinjury postinjury non- non-ejaculation.ejaculation. Use Use of of the the penile penile vibrator vibrator is is successful successful with with menmen with with a alesion lesion above above a aT8 T8 segment segment of of the the spinal spinal cord. cord. Rectal Rectal electrostimulation electrostimulation and and electroejaculationelectroejaculation (EEJ) (EEJ) are are other other techniques techniques for for sperm sperm obtained obtained from from a aparalysed paralysed patient. patient. TheThe principle principle of ofelectroe electroejaculationjaculation is to is induce to induce reflective reflective ejaculation ejaculation while while using using an alter- an al- natingternating current current of voltage of voltage up to up 15 to V 15with V withparaplegics paraplegics and up and to up 5 V to with 5 V withtetraplegics; tetraplegics; the currentthe current ranges ranges between between 100–600 100–600 mA mA[3]. [PV3].S PVS appears appears as asa safer a safer and and less less demanding demanding methodmethod for for the the patient. patient. TheThe current current market market offers offers other other variants variants of of the PVS device: FertiCare andand FertiCareFertiCare 2, 2,or or Viberect-Viberect- Penile Penile vibrator/stimulator. vibrator/stimulator. TheThe competitivecompetitive devices,devices, however,however, dodo notnot allowallow a a preciseprecise amplitude setting and electronic electronic main maintenancetenance of of the the set set frequency. frequency. The The designed designed devicedevice FertEx FertEx CM CM also also provides provides an interface an interface for recording for recording one’s one’sheart heartrate and rate blood and pres- blood surepressure for a potential for a potential cessation cessation of the procedure of the procedure before beforeany succeeding any succeeding complications complications could becould observed. be observed. Another Anotheradvantage advantage of the FertEx of the CM FertEx PVS CMdevice PVS is devicethe continuous is the continuous storing ofstoring information of information of the selected of the mode selected of stimulation. mode of stimulation. The data obtained The data this obtained way can thisbe later way analysedcan be later or imported analysed into or importedthe patient’s into database the patient’s for further database use. forDevices further of this use. nature Devices are of notthis currently nature areavailable not currently on the ma availablerket. In ona similar the market. device In operating a similar on device a similar operating principle, on a productionsimilar principle, was discontinued production and was replaced discontinued by a less and effective replaced device by a less that effective stimulates device nerve that endingsstimulates on both nerve sides. endings Thanks on to both this sides. step, the Thanks demand to this on the step, Czech the demandmarket has on increased the Czech market has increased significantly and doctors are practically waiting for the development significantly and doctors are practically waiting for the development of the FertEx CM of the FertEx CM device to be completed. device to be completed. Symmetry 2021, 13, 62 10 of 11

When designing the solution, the safety of the patient was the highest priority and both the prevention of the mechanical and electric malfunction of the device were taken into account. The basic technical requirements were: Reaching the maximum load of 10 N, securing the amplitude with a 1–4 mm range and oscillation frequency between 60–120 Hz, and maintaining the selection of a safe electric power source, which is a source with a direct current of 5–12 V voltage [12]. Other technical requirements were the possibility of wireless inductive charging and securing compliance with the electric norm stated by the ordinance about electric devices. The final requirement was to secure the watertight integrity corresponding with the integrity of the device in 5 metres depth and controlling functions of the device regarding the priority of securing the safety of the patient [13]. The construction of the device complies with the set requirements for the construction of medical devices according to the EU norm. The mechanical parts of the device were checked by numerical calculations for stress, cutting, pressure, thrust, and bruising. Considering the very insignificant applied forces, it was verified by a second calculation check and the device complied with the mentioned kinds of load. Charging was provided by a secure direct electric source, the accumulator, which can be charged repeatedly. The type of accumulator has a long lifespan and does not have a memory effect. The electronics which are in charge of the automatic device control were designed regarding the safety of the patient. The body of the medical device met the requirements for the mechanical load by vibrations generated by the device and the lifespan of the prototype [6]. The protection against foreign elements and water was solved so that it is possible to wash the device under running water without danger of water contamination, which could subsequently damage the electronic parts. The device is protected from overload, in other words against misapplication and a violent cessation of the electronic nondestructive protection, which in case of malfunction would safely disconnect the power supply without endangering the patient.

5. Conclusions Penile vibrostimulation is a safe and efficient method for sperm retrieval from males with a spinal cord injury. The designed device for PVS offers a higher range of amplitudes and frequency vibrations in all five variants of the constructional solutions. In regard to the serial manufacturing of the device, feedback from the patient is assumed while being stimulated, and the electronics are therefore designed with an option to connect blood pressure and heart rate monitoring. In case of recording nonstandard values, it is then possible to prevent the development of autonomous dysreflexia or other complications while using the device. After that, there is always an emergency cessation of the device and an alarm alert. The course of the stimulation is automatically recorded into the memory of the device for further data analysis or the patient’s database information for doctors. Data transfer is done by a Bluetooth standard or by a USB cable. It is safe to state that low production costs and a more affordable device are achieved by the designed vibration mechanism [4,6,7,14]. Technical parameters of the FertEX CM device are as follows in Figure9—reachable frequency 60–120 Hz and amplitude 1–5 mm; charging from a safe source from built-in accumulator; recording of the course during stimulation into the memory of the device; emergency cessation and alarm alert functions; Bluetooth or USB data transfer; and watertight integrity to the depth of 5 m. Symmetry 2021, 13, 62 11 of 11 Symmetry 2021, 13, x FOR PEER REVIEW 11 of 11

FigureFigure 9. 9.Final Final form form of of the the body body of of the the device device called called FertEx FertEx CM. CM.

Author Contributions: Investigation, A.S.; Supervision, M.C. and T.Š. T.Š.: All medical contribu- Authortions based Contributions: on her research,Investigation, professional A.S.; practice Supervision, and experience M.C. and T.Š. of a T.Š.: doctor All medicalat the Faculty contributions Hospital basedin Brno on in her the research, Czech Republic. professional M.C.: practice Technical and expe experiencerience mentioned of a doctor in at the the introduction Faculty Hospital of the inar- Brnoticle inbased the Czech on his Republic. professional M.C.: practice Technical of the experience University mentioned of Defense in thein Brno introduction in the Czech of the Republic article basedand the on Army his professional of the Czech practice Republic. of the All University authors have of Defense read and in agreed Brno in to the the Czech published Republic version and of thethe Army manuscript. of the Czech Republic. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Funding: This research received no external funding. Institutional Review Board Statement: The study was conducted according to the guidelines of the Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki. Declaration of Helsinki. InformedInformed Consent Consent Statement: Statement: Informed consent was was obtained obtained from from all all subjects subjects involved involved in in the the study. study. ConﬂictsConflicts of of Interest: Interest:The The authors authors declare declare no no conﬂict conflict of of interest. interest.

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