Vacuum Therapy in Erectile Dysfunction—Science and Clinical Evidence

J Yuan; A N Hoang; C A Romero; H Lin; Y Dai; R Wang

Disclosures

Int J Impot Res. 2010;22(4):211–219 

In This Article

VT in Penile Rehabilitation—VED

Introduction

Prostate cancer is the most common solid-organ cancer among men and one of the leading causes of death.[53] With early detection and radical prostatectomy (RP), the 15-year overall actuarial cancer-specific survival rate has reached 90%.[54,55] Unfortunately, RP is associated with several quality-of-life side effects, mainly urinary incontinence and ED.[56,57] With improvements in technique and the use of robotic-assisted procedures, incontinence rates have reduced to an acceptable level.[58–61] However, the same cannot be said for ED, as the incidence of ED after RP ranges from 10 to 100%.[62] In an attempt to improve patients' quality of life after RP, PR is now widely applied in clinical practice.[55,63–65] Currently, PR methods include the use of PDE5I, intracavernosal self-injection/intraurethral suppositories, VED or a combination of different therapy modalities.[55,63–65]

Pathophysiology

Erectile function (EF) becomes impaired immediately after RP secondary to cavernous nerve damage during surgery, resulting in neuropraxia.[66] Even with the most meticulous nerve-sparing dissection, some degree of neuropraxia is unavoidable because of the close proximity of the nerves to the prostatic gland. These nerves tend to recover slowly, and it may take as long as 3 years for them to return to a new baseline functional status.[58] Absence or decreased erection and penile size ensue before recovery of the cavernous nerve.[57,67] A reduction in arterial inflow has also been reported due to ligation of the accessory internal pudendal arteries during RP.[68,69] The combination of nerve damage with decreased arterial inflow may cause penile tissue hypoxia leading to apoptosis and collagen deposition, which ultimately results in venous leak, which in turn, has been linked to the pathophysiology of ED after RP.[70–79] As nerve recovery requires time, it is hypothesized that VED may bypass the neuropraxic period by directly dilating the cavernosal arteries, therefore, overcoming hypoxia and preventing apoptosis and fibrosis before the functional recovery of the cavernous nerve.

Laboratory and Clinical Evidence

VED, as PR modality, simulates natural erection and allows reoxygenation of the penis.[80] There has been growing evidence to support this. Blair et al.[81] documented that sub-atmospheric pressure induces an initial increase in arterial inflow in the forearm of healthy volunteers; Greenfield and Paterson[82] further showed a vasodilation effect on the arteries of the forearm in volunteers exposed to a sub-atmospheric pressure of −150 to −200 mm Hg, which is similar to the pressure used in VED.[14] Diederichs et al.[83] noticed that negative pressure induces expansion of penile tissue followed by increase in blood flow in primates; the authors believed that the increased blood flow was arterial inflow. Broderick et al.[17] showed that a transient vacuum application increases the peak flow velocity of the cavernous arteries in humans. Donatucci and Lue[84] further determined that chronic VED usage increases cavernous arterial flow in men with mild vasculogenic ED as measured using a duplex ultrasonograph. Bosshardt et al. performed blood gas analysis before VED application, immediately after the application of a constriction ring and repeated blood gas analysis 15 and 30 min later with the constriction ring in place in ED patients. This test showed that the mean O2 saturation of corporal blood immediately after VED-induced erection was 79.2%, which translates as arterial and venous contributions of flow of 58 and 42%, respectively. In addition, after 30 min of continuous application of a constriction ring, blood gas analysis showed ischemia of the penile blood.[18] This is the rationale for the use of VED as PR modality, instead of VCD. Recently, Müller et al.[85] applied hyperbaric oxygen therapy on a bilateral cavernous nerve crash rat model and showed that hyperbaric oxygen therapy improved the preservation of EF. To explore the molecular mechanism of VED, a rat-specific VED, which simulates human VED, was successfully created and applied on a bilateral cavernous nerve crash model by our group.[86] Our preliminary data indicated that daily VED therapy significantly improved the intracavernosal pressure/mean artery pressure ratio, preserved penile length and girth, decreased the level of hypoxia-inducible factor-1α, transforming growth factor-β1, collagen and apoptosis, and increased the level of eNOS and α-smooth-muscle actin.[87]

The latest PR trials are summarized in Table 3.[88] Most trials used PDE5I to preserve penile sexual health. One limitation of PDE5I is its requirement of intact nerves to produce nitric oxide for proper function. There have been theories that PDE5I may work through a separate, neuron-independent endothelial cell mechanism; however, it is still unproven.[80] The direct mechanism of VED circumvented this limitation. Given its low complication rate and relatively high compliance rate, along with being the only modality that preserves penile length, VED is an ideal choice as PR after RP[80] or other pelvic injuries.[97,98]

Munding et al.[99] documented that up to 48% men had considerable shortening of the stretched penile length (greater than 1.0 cm) at 3 months after RP. Savoie et al.[100] found that nearly 20% of men who undergo RP experience a penile length loss greater than 15%. Gontero et al.[101] followed 126 men who had undergone RP and measured penile length before surgery, at the time of catheter removal, and then at 3, 6 and 12 months. They found that the greatest amount of shrinkage occurs in the immediate postoperative period, although shortening continues at a lesser rate throughout the entire study period. They also found that a return of EF, defined as an International Index of Erectile Function (IIEF) of 15, and a nerve-sparing technique during RP, mitigated penile shaft shrinkage. Several studies looking at the efficacy of VED in preserving EF have also examined preserved penile length as a secondary endpoint.

Raina et al.[92] randomized 109 post-NSRP patients to early VED daily usage (group-1, n=70) versus no erectogenic aid (group-2, n=35). The participants were followed by the Sexual Health Inventory for Men (SHIM) score. The secondary endpoints included compliance, changes in penile circumference or length, return of natural EF and ability for vaginal intercourse. At the end of the 9-month follow-up, 80% (60/74) of those in group-1 were able to have sexual intercourse using the device, with a satisfaction rate of 55%. Nineteen patients reported return of natural erections and 17 had erections sufficiently firm for vaginal penetration. Conversely, only 37% (13/37) of the patients in group-2 regained natural erections. When evaluating for secondary endpoints, among those who used the device regularly, only 23% (14/60) reported a decrease in penile length and girth, whereas 22/35 (60%) patients in the control group complained of penile shrinkage. This result was confirmed by Dalkin et al. who administered VED therapy to 39 men after RP for 90 days after catheter removal.[102] In their study, 97% of compliant men maintained their preoperative stretched penile length; shrinkage was defined as ≥1 cm. The authors concluded that early usage of VED facilitates early return of spontaneous EF, early resumption of sexual life resulting in spousal satisfaction and preservation of penile length and size.

Other authors have investigated the timing of VED therapy to maximize its benefits. Köhler et al.[93] randomized 28 patients undergoing RP to early VED use (group-1, n=17) and delayed VED use (group-2, n=11). Group-1 was instructed to use VED daily, starting at 1 month after RP for two consecutive 5-min periods. Group-2 was instructed to use VED, as many times as desired, starting at 6 months after RP. These men were followed using IIEF scores. At a follow-up of 3 and 6 months, group-1 had a statistically higher IIEF score than group-2. Beyond 6 months, when group-2 began using VED therapy, there was no statistical difference in IIEF scores between both groups. When evaluating for penile shortening after RP, group-1 did not experience any significant penile length reduction; whereas group-2 experienced considerable shrinkage at 3 months (mean loss 1.87 cm) and 6 months of follow-up (mean loss 1.82 cm). However, when group-2 began using VED therapy, the mean penile length loss decreased to 1 cm. The authors concluded that early VED therapy after RP helps to improve early sexual function and preserve penile length.

Solid evidence that VED daily rehabilitation preserves penile length and EF has been scattered; however, a multicenter, randomized study with objective criteria and long-term follow-up is still needed.

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