Objective: This study investigates the effect of regular airflow, as an isolated single factor, through Groningen and Provox2 voice prostheses on biofilm formation.
Material and methods: Groningen and Provox2 voice prostheses were placed in a modified Robbins device and inoculated with the total microflora from an explanted Groningen voice prosthesis. After 3 days, prostheses were either flushed 3 times per day with the Provox flush, treated with an airflow using an increasing order of air pressure (10, 15 and 20 cmH2O) or vigorously perfused by means of imitated coughing (air pressure 20 cmH2O). As a control, prostheses were left undisturbed to promote biofilm growth. Following flushing, blowing or coughing, each artificial throat was perfused with 200 ml of phosphate-buffered saline. This procedure was repeated three times a day for 9 days. At the end of each day, the artificial throats were filled with growth medium for 30 min and left empty during the night after draining. After 12 days the microflora on each voice prosthesis was quantified by plating on blood agar for bacteria and on de Man, Rogosa and Sharpe agar for yeasts.
Results: The use of the Provox flush reduced bacterial prevalence on Groningen and Provox2 voice prostheses to 71% and 45% of the control values, respectively, without affecting the number of yeasts. Increasing airflows and imitated coughing yielded reductions of 45-70% in bacterial and yeast prevalence on Provox2 voice prostheses. On the Groningen voice prostheses the effects of increasing airflows and imitated coughing were less pronounced: reductions in bacterial and yeast prevalence of 56-87% were observed.
Conclusion: This study shows that use of the Provox flush has a cleansing effect, especially on Provox2 voice prostheses, and furthermore suggests that daily airflow through voice prostheses as part of a daily maintenance scheme reduces biofilm formation and can be expected to prolong the life of these devices.