184 | Chapter 7 Discussion With this study we found that prophylactic replacement of VPs (PVPR) in laryngectomized patients is not feasible. PVPR would optimally reduce unexpected VP leakages and consequent aspiration and improve the quality of life of patients. To prevent at least 70% of all leakages in regular VP users, on average an additional number of six VPs per patient per year are needed, which is not desirable, given the costs and additional hospital visits. Device lifetime differed significantly between primary TL (PG1) and salvage TL (PG2) but the number of additional VPs in PVPR was similar. The device lifetime of regular VPs in patients only using regular VPs (VPG1) is significantly longer than in patients alternating between regular and problem-solving VPs (VPG2), which is explained by the indication for problem-solving VPs (a short device lifetime with regular VPs)3. The high inter-and intrapatient variability in device lifetime (figure 2) makes it impossible to apply the concept of PVPR in daily practice. The device lifetimes are widely spread, and there is no clear trend visible, which is supported by the high standard deviation in device lifetime (median 64.5 days), which is around the median device lifetime, causing the high Coefficient of Variation (CV= SD/mean, median 0.8). The individual adaptive simulations showed that only 25%-36% of the leakages can be prevented. The Monte-Carlo simulations showed that PVPR would only be valuable if the CV is < 0.5, again stating that PVPR is not possible in real life. As mentioned, prophylactic replacement has been successful for pacemakers-users. The main reason why pacemakers are suitable for prophylactic replacement is the low variability in the device lifetime of batteries. The device life of VPs are depending on much more aspects causing unpredictable (early) VP leakage and a high variability in device lifetime. With problem-solving VPs, device life did become longer, but because of the high costs, they are not worldwide available for patients and when available mostly used in patients with short device lifetime 19,20. Variability in device life is a problem found in all types and brands of VPs and different countries16, making the results of this study generalizable for all patients using a VP, worldwide. The ultimate goal in PVPR would be to replace VPs at a set moment (just) before leakage, predicted by previous device lifetime and known patient or treatment variables. With such a policy, one could reduce the number of unexpected VP replacements and potentially prevent aspirations. This would likely provide patients more security, peace of mind and possibly increase QoL. Planned replacements are also more convenient
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