Phantom study evaluating detection of simulated upper airway occlusion using piezoelectric ultrasound transducers

In Situ Investigation of Upper Airway Occlusion in Sleep Disordered Breathing Using Ultrasonic Transducer Arrays

This work presents a novel application of ultrasound for the real-time, non-invasive investigation of occlusion of the upper airway during events of obstructive sleep apnea/hypopnea syndrome. It is hypothesized that ultrasonic pulses applied to the neck during apneic events produce spectral and temporal features that can detect apnea occurrence. Theoretical models of ultrasound propagation and an in vitro test were conducted to test this hypothesis in both transmission and reflection modes. Complete specifications and technical details of the system design and fabrication, which is mounted on each subject's neck, are presented, including the methodology. Nine patients (seven male and two female, mean age of 42 years, with a range of 25 to 56 years, and body mass index 37.6 ± 6.6 kg/m²) were recruited for a full night study, which included simultaneous nocturnal polysomnography for the validation of the results. Nine temporal features and four spectral features were extracted from the envelope of the received pulse waveform. These were used to compute 26 metrics to quantify the changes in the ultrasonic waveforms between normal breathing and apneic events. The statistical analysis of the collected ultrasonic data showed that at least two or more of the proposed features could detect apneic events in all subjects. The findings establish the feasibility of the proposed method as a cost-effective and non-invasive OSAHS screening tool.

Quantifying Long QT Syndrome in Obese Sleep Apnea Patients Undergoing Roux-en-Y Gastric Bypass Surgery

Obstructive Sleep Apnea/Hypopnea Syndrome (OSAHS) is sleep-disordered breathing distinguished by repetitive cessation or reduction of airflow due to the collapse or narrowing of the upper airway during sleep with continued respiratory effort. A high level of incidence of OSAHS is correlated with obesity. Both severely obese patients and OSAHS patients manifest Long QT Syndrome (LQTS). It is reported that most obese patients undergoing weight reduction surgery positively reverse symptoms of LQST. Also, severely obese OSAHS undergoing the same surgery report alleviation of OSAHS symptoms. In this study, we presented preliminary results of the changes in QT and QTc intervals for obese OSAHS patients undergoing Roux-en-Y Gastric Bypass (RYGB) surgery and had their weight reduced, and were treated from OSAHS post-RYGB surgery. We developed an algorithm to detect the different waveforms in the ECG signal and calculated QT and QTc intervals. Results comparing the changes in the QT and QTc pre- and post-RYGB surgery for four apneic subjects (Aged 37.0 ± 8.9 years, Pre-RYGB BMI 51.7 ± 10.1 kg/m², Post-RYGB BMI 35.6 ± 7.9 kg/m²) were contrasted with a control group of 3 non-apneic subjects (Aged 32.7 ± 7.0 years, Pre-RYGB BMI 50.8 ± 11.8 kg/m², Post-RYGB BMI 31.6 ± 2.9 kg/m²) who underwent the same surgery. The results suggest that although the RYGB surgery is successful in weight loss and OSAHS symptoms reduction, apneic patients may continue to have non-reversible LQTS despite long-term weight reduction.