The Design & Verification of an Automatic Occlusion Speech Valve for Voice Rehabilitation

Abstract

This work investigates the restoration of the lost functions of the upper airway in patients who have
undergone total laryngectomy surgery. The primary airway functions were defined as ventilation and
patency, heating and humidification of air, filtration of air, coughing, swallowing, speech, olfaction,
gustation and chemo sensitisation and air resistance.
Through a review of the literature, the performance of the airway functions was compared pre and
post laryngectomy. It was found that all of the aforementioned functions were negatively affected
by total laryngectomy which led to lower quality of life and increased risk of harm or disease
compared to healthy individuals of the same age groups.
There are medical devices described in the literature used for the restoration of upper airway
function. For most identified functions there was a medical device and or therapeutic solution to
restore them partially or fully. Research found no evidence that existing medical devices had the
level of filtration they provided verified. Many devices in the literature restored one function,
requiring patients to use a combination of devices, this has benefits and disbenefits, mostly relating
to in use life. This work aimed to restore as many functions as possible within a singular device.
A singular device was designed to restore the upper airway functions. The variability of the
difference in resistance of the larynx to inhalation and exhalation identified in the literature was
incorporated into the device, the phenomenon was approximately matched by employing fluid
structure interaction within the device. The design featured a novel bistable diaphragm that the
patient can close hands free when they want to redirect air through a speech device. This had the
benefit of remaining closed during pauses in speech.
Different functions of the candidate device were evaluated through a combination of tests, including
tests following established methodologies and new tests and test apparatus developed as part of
this work. Pneumatic test apparatus was built to produce outputs that matched laryngectomy
patient spirometry data found in the literature.
The first iteration of the design was tested in vitro. The design was translated into FEA, validated
with the lab results and optimised. Heat and moisture exchange and filtration were fully restored.
Cough, breathing resistance and speech were partially restored. It was concluded that a singular
device can restore most of the upper airway functions to a level closely resembling prelaryngectomy. Additionally, it was concluded that a device must be used in conjunction with other
restorative medical devices to effectively restore all lost functions to pre-laryngectomy upper airway
performance.