Klaske van Sluis

Objective and subjective voice outcomes: a systematic review 37 functioning which fits within the widely applied International Classification of Functioning (ICF) [58]. TES has favorable outcomes on the acoustic variables F0, MPT and in- tensity compared to ES. Both speech methods are generated within the same sound source, the PE-segment. The most likely explanation for the more favor- able acoustic voice outcomes in TES is that this type of speech is pulmonary driven. It is feasible that with the pulmonary airflow, the tidal volume (roughly 5-600 ml) of TES, a more stable and better controlled airflow is created. The higher pressure could lead to controlled hypertonicity or a movement of the PE-segment to a more cranial position. This can be an explanation for the higher F0 values which are found in TES. For ES only a minimal volume of air is available, about 60-80 ml, which is roughly 2% of the lung capacity, and controlling the pressure is not really possible [1]. This limited airflow and vol- ume lead to a shorter phonation time for ES and, presumably, to a lower F0 and lower intensity. No limitation in publication date was applied. Several studies published in the 80’s and 90’s were included. During the 80’s ES was known as the gold standard for speech rehabilitation, and TES was just introduced. It is likely that ES was educated fairly well in this decade. Esophageal speakers may have achieved more satisfactory outcomes in the earlier publication period than present. We assume that the result of the speech rehabilitation efforts plays a role in self-reported outcomes. Especially ES patients often require a prolonged and intensive rehabilitation period and success is not guaranteed. Therefore, ES speakers could be more satisfied and proud of their accomplishments than TES speakers, who acquire their speech more rapidly. For the studies included in this systematic review, it is very likely that re- cruitment bias exists. In most studies, recruiting and selection of participants is not described. For the acoustic and perceptual outcomes, it can be assumed that only speakers with a fairly good level of speech were included. Some au- thors report this bias by mentioning that they only included excellent speakers [27, 33, 34, 48, 52]. One study reported that all patients in the group of ELS failed to achieve intelligible ES and five failed in TES [51]. Also, studies reported that they had to exclude participants because of lack of speech performance or had to exclude audio files from acoustic analysis due to lack of periodicity [32, 37]. Obviously, there are more aspects influencing the acoustic, perceptual and PROs of speech rehabilitation after TL. In Table 2.6 several of these aspects related to the speech rehabilitation methods are listed. Valuable information that can explain functional outcomes after TL is missing in the reported studies. Most studies do not mention treatment details or time since TL. Furthermore, information about offered speech rehabilitation methods and aggregate practice time with the speech language pathologist is lacking. Knowledge of caretakers, and differences in health care and insurance systems play a role in the speech re- habilitation options that can be offered. Also, patients’ personal factors should