An Investigation into Improving the CPAP and the Electrical Stimulation for the OSA Treatment
Obstructive sleep apnea (OSA) is considered a worldwide public health problem. It is characterised by the repetitive episodes of partial (hypopnea) or complete collapse (apnea) within the upper airway during sleep of OSA patients despite their continuous breathing efforts. From a pathophysiological point of view, OSA is a multifactorial disease and the mechanism underlying OSA is not fully understood. However, it is reported that it is related to the progressive loss of lingual and pharyngeal tone in the upper airway during sleep compared to wakefulness in patients with OSA. Studies have confirmed that OSA may lead to Cardiovascular diseases, Diabetes, Morbidity and high mortality rate.
Current OSA treatment include many modalities. Some are non-invasive such as the continuous positive airway pressure (CPAP), which is considered as the primary choice to manage OSA patients. While others are invasive such as the electrical stimulation techniques. However, both treatment techniques have many drawbacks. For example, the use of CPAP may be associated with numerous side effects including upper airway congestion, and significant dryness. On the other hand, electrical stimulation is associated with inflammation due to biocompatibility issue of the electrode with human tissue.
As both of the above two modalities are widely used and expanding, this thesis is focus on quantifying the damage caused by both of them and suggest possible scenarios to overcome these damages.
To do so, this is a two-fold thesis. First to quantify humidification within upper airway (UAW) during application of CPAP. The study also aims to determine the impact of applying pressure oscillation (PO) waves superimposed on CPAP on humidification parameters of the UAW. Another important aspect of this research is to improve electrical stimulation therapy as an alternative to CPAP.
To address the first part, an ex vivo experimental setup was developed to quantify the air humidification at different CPAP operating conditions. While the in vivo tests were conducted using a proper clinical trial.
Results from ex vivo studies have confirmed that at normal breathing, the reconditioning of inhaled tidal volume may lead to a fluid depletion within the depth of airway surface liquid that equal to 2.17 µL/cm2.min. However, applying the CPAP at different pressure of (5,10 and 20 cmH2O may affect this value, significantly. Results of ex vivo studies have confirmed that a reduction percentage within tracheal Fluid depletion can be 38.4 % up to 75.8 %. The highest reduction percentages were associated with applying CPAP at 20 cmH2O, and the lowest effect was associated with applying CPAP at 5 cmH2O. Data suggest a backward relationship between CPAP and TWC values of the processed air and the Tracheal Fluid depletion By applying the Pressure oscillation at different frequencies of (5, 20 and 30) Hz, results shows a remarkable improvement within the tracheal Fluid depletion at any pressure value of CPAP. However, the highest improvement percentage of 78.8 % was achieved at applying PO at 30 Hz, in conjunction with the CPAP at 5 cmH2O. Result suggests the efficacy and reliability of applying PO as alternative to address issues associated with the CPAP.
Results obtained from clinical trial supports findings of ex vivo studies. As per data, applying full session treatment using CPAP, saliva samples collected from participants have witnessed a drastic reduction in their salivary flow rate, which was already considered as low. Reduction percentage values were ranged from 5.81 % to 70.15 %. The highest decreasing percentages within the salivary flow rates were found with participants of BMI higher than 34.4 kg/m2. The lowest percentages were found within participants with BMI of equal to or lower than 32.8 kg/m2. However, a major improvement in the salivary flow rate recorded from participants after CPAP and PO treatment sessions. Improvement percentages are in the range of 0.49 to 1.39 mL/min, representing an increasing percentage between 9.4 % up to 129 %. The highest improvement was recorded within the salivary flow rate of the participants with a BMI of 29.9 kg/m2, whereas the lowest was obtained with participants of 49.1 kg/m2. Results may confirm the efficacy of applying the PO in conjunction with the CPAP to improve dryness symptoms that mainly associate with the use of the CPAP.
To address the inflammation and poor performance caused by inflammation developed by the Electrical stimulation technique, a biocompatible electrode have been developed, Morphological studies have confirmed the capturing of cell’s feature on the surfaces of electrode. Also, the implant was electrically-conductive, and results obtained from the test confirmed that both PPy/APS/ Kolliphor P188 nanocomposites and implants are electrically-conductive. Biocompatibility of implant surfaces was tested, and results obtained from corresponding tests have confirmed its non-toxicity. Furthermore, applying electrical stimulation to the attached cells has confirmed that a signal lower than 150 mV/mm can be tolerated by the attached cell population. Collectively, result may suggest the efficacy of our innovative technique to enhance electrode biocompatibility.