Albert Anne Geertsema

AIRFLOW RESISTANCE OF AIRFLOW-REGULATING DEVICES DESCRIBED BY INDEPENDENT COEFFICIENTS

Rehabilitation after laryngectomy includes more and more the use of airflow-regulating devices such as shunt valves (SVs), tracheostoma valves (TSVs), and heat and moisture exchange (HME) filters. In determining the quality of those devices, airflow resistance is a very important factor. It is currently defined as pressure drop divided by airflow. However, for most applications, this definition does not result in a pressure- and airflow-independent parameter. Therefore, a new set of parameters is defined and applied to pressure-airflow curves of airflow-regulating devices. Pressure drop over TSVs and HME filters appears to have a squared relationship with flow. In SVs, it has a linear relationship. The new set of parameters describes the pressure-airflow relationship properly for all considered devices. In conclusion, theoretical predictions of flow mechanics appear to be valid for SVs, TSVs, and HME filters. Only 2 coefficients are necessary to describe the pressure-flow characteristics of these airflow-regulating devices, independent of pressure drop over and flow through the device.

Biocompatibility of a novel tissue connector for fixation of tracheostoma valves and shunt valves

Rehabilitation after laryngectomy often includes the use of a shunt valve and a tracheostoma valve to restore voice. To improve the fixation method of these valves, a new tissue connector has been developed, basically consisting of a ring that will be integrated into surrounding tracheal soft tissue. The valves can be placed in the ring. To test the principle of the tissue connector, a prototype consisting of a subcutaneous polypropylene mesh and a percutaneous titanium stylus was implanted into the backskin of 10 rats by a two-stage surgical procedure. We reasoned that if a firm connection can be realized with the skin, a firm connection with the trachea will also be possible. The subcutaneous part was implanted first, followed by the percutaneous part after 6 weeks. The complete tissue connector with surrounding tissue was removed 8 weeks later and examined histologically. The principle of the new tissue connector proved to be effective: hardly any epithelial downgrowth appeared, and adhesion of soft tissue was demonstrated. No infection or severe inflammation reaction was detected. The tissue connector seems appropriate for its intended use.

Airflow Resistance of Heat and Moisture Exchange Filters with and without a Tracheostoma Valve

Rehabilitation of laryngectomees has been furthered by the introduction of heat and moisture exchange (HME) filters, placed over a tracheostoma or on a tracheostoma valve (TSV). The airflow resistance of HME filters is an important factor with regard to the comfort of the patient. The goal of this study was to determine the airflow resistance (defined as the pressure drop over the device divided by the squared airflow through the device) of 4 commercially available HME filters with and without a TSV. The pressure drop over and the airflow through the devices were measured in vitro. Distinct differences among the devices were found. The mean airflow resistance of the HME filters ranged from 135 to 346 Pa • s2/L2, that of TSVs was between 66 and 297 Pa • s2/L2, and that of the combination was between 263 and 454 Pa • s2/L2. The Stom-Vent 2 HME filter and the Adeva Window TSV with an Adeva filter had the lowest airflow resistance of the devices measured in this study.

In vitro measurements of aerodynamic characteristics of an improved tracheostoma valve for laryngectomees

Abstract Tracheostoma valves are often required in the rehabilitation process of speech after total laryngectomy. Patients are thus able to speak without using their hands to close the tracheostoma. The improved Groningen tracheostoma valve consists of a “cough” valve with an integrated (“speech”) valve, which closes for phonation. The cough valve opens as the result of pressure produced by the lungs during a cough. The speech valve closes by the airflow produced by the lungs, thus directing air from the lungs into the esophagus at a deliberately chosen moment. An experimental setup with a computer-based acquisition program was developed to measure the pressure at which the cough valve opened and the flow at which the speech valve closed. In addition, the airflow resistance coefficient of the tracheostoma valve was defined and measured with an open speech valve. Both dry air from a cylinder and humid expired air were used. Results showed a pressure range of 1–7 kPa to open the cough valve and a flow range of 1.2–2.7 l/s to close the speech valve. These values were readily attained during speech, while the flow range occurred above values reached in quiet breathing. The device appeared to function well in physiological ranges and was optimally adjustable to an individual setting. No significant differences were measured between air from a cylinder and humid expired air. Findings showed that methods used to obtain results could be employed as a reference method for comparing aerodynamic characteristics of tracheostoma valves.

In vivo measurements of an improved tracheostoma valve based on inhalation

An improved, inhalation-based tracheostoma valve (TSV) was designed to facilitate finger-free tracheoesophageal speech. In contrast to existing models, the TSV closes by means of strong inhalation (instead of exhalation) to reach the “speaking position.” Air is inhaled through a small 1-way valve that allows unlimited phonation time. The device can be deliberately changed to the “breathing position” by a fast expiration. Experimental setups were used to measure in vitro and in vivo the performance of the inhalation TSV. In patients, the inhalation TSV was compared with existing TSVs on the following parameters: air volume used to close the TSVs, speaking time of the TSVs, and total air volume during exhalation through the TSVs. The inhalation TSV functions well in physiological ranges, is optimally adjustable, and is an improvement over existing devices. It makes continuous speech possible and saves as much as 22% of the total exhalation volume for speaking, in contrast to existing TSVs.

A novel tracheal tissue connector for fixation of laryngeal prostheses

A tissue connector (TC), basically consisting of a ring that will be integrated into the trachea, is under development to study the fixation of laryngeal prostheses. Two experiments have been performed to test the TC in goats. In experiment 1, a polypropylene mesh was implanted around the trachea. The meshes were explanted after 6 and 12 weeks. In experiment 2, the actual TC consisted of two titanium rings (inner ring and outer ring) executed as quarter rings, fixed on each other, and a polypropylene mesh like a sandwich in between. The titanium inner ring was implanted between two tracheal rings thus penetrating the trachea with the mesh around the trachea and the fixed titanium outer ring on the outside of the trachea. The TCs were removed after 12 weeks. Experiment 1 showed that the mesh was entirely infiltrated by host tissue. Inflammatory cells and high vascularisation were observed in 3 of 4 implants. However, in experiment 2, the mesh was completely incorporated by mature connective tissue without inflammation reaction. At some areas, deposition of cartilage tissue was observed. In conclusion, the TC was firmly embedded in the trachea thus being appropriate for its intended use.

Numerical simulation of the influence of a left ventricular assist device on the cardiovascular system

The PUCA (pulsatile catheter) pump is a left ventricular assist device (LVAD) capable of unloading the left ventricle (LV) and improving coronary flow by providing a counterpulsation effect. It consists of an extracorporeal located membrane pump, coupled to a transarterial catheter that enters the body via a superficial artery and ends in the LV. Blood is aspirated from the LV and pumped in the ascending aorta through the same catheter guided by a valve system. Timing and frequency of the PUCA pump influence its efficacy. To study the influence of several pump parameters a numerical model of the device and the circulatory system has been developed. Results of animal experiments were used to validate the model. Optimization studies resulted in a pump configuration with a stroke volume of 50 cc and pump:heart frequency mode of 1:2 that starts ejection at the beginning of diastole.