Investigation of Narrow-band NIR LED Spectral Response Towards a Non-invasive Glucose Sensor.

Spectroscopy is utilised extensively in medical sensing technology. Typically, hand-held spectroscopy equipment uses miniature narrow-band light emitting diodes (LEDs) and photodiodes to emit and detect light, respectively. Photodiodes typically absorb light across a wide spectra so measurements can be corrupted by surrounding light. LEDs in the visible spectrum have a narrower spectral response and can be used in place of a traditional photodiode. However, the absorption characteristics of near infrared (NIR) spectrum LEDs is unknown. A discrete, low-cost spectrophotometer was designed to assess spectral response for 8 narrow band NIR LEDs. The normalised and raw spectral response determined the optimum detector for 1050 nm - 1300 nm is the 1450 nm LED, and the optimum detector for 1450 nm - 1650 nm emissions is the 1650 nm LED.Clinical relevance - Understanding the spectral response of narrow-band LEDs in the NIR spectrum will aid development of NIR hand-held spectroscopy medical devices.

Respiratory pressure and split flow data collection device with rapid occlusion attachment.

Respiratory model-based methods require datasets containing enough dynamics to ensure model identifiability for development and validation. Rapid expiratory occlusion has been used to identify elastance and resistance within a single breath. Currently accepted practice for rapid expiratory occlusion involves a 100 ms occlusion of the expiratory pathway. This article presents a low-cost modular rapid shutter attachment to enable identification of passive respiratory mechanics. Shuttering faster than 100 ms creates rapid expiratory occlusion without the added dynamics of muscular response to shutter closure, by eliminating perceived expiratory blockage via high shutter speed. The shutter attachment fits onto a non-invasive venturi-based flow meter with separated inspiratory and expiratory pathways, established using one-way valves. Overall, these elements allow comprehensive collection of respiratory pressure and flow datasets with relatively very rapid expiratory occlusion.

Non-Invasive Assessment of Abdominal/Diaphragmatic and Thoracic/Intercostal Spontaneous Breathing Contributions.

(1) Background: Technically, a simple, inexpensive, and non-invasive method of ascertaining volume changes in thoracic and abdominal cavities are required to expedite the development and validation of pulmonary mechanics models. Clinically, this measure enables the real-time monitoring of muscular recruitment patterns and breathing effort. Thus, it has the potential, for example, to help differentiate between respiratory disease and dysfunctional breathing, which otherwise can present with similar symptoms such as breath rate. Current automatic methods of measuring chest expansion are invasive, intrusive, and/or difficult to conduct in conjunction with pulmonary function testing (spontaneous breathing pressure and flow measurements). (2) Methods: A tape measure and rotary encoder band system developed by the authors was used to directly measure changes in thoracic and abdominal circumferences without the calibration required for analogous strain-gauge-based or image processing solutions. (3) Results: Using scaling factors from the literature allowed for the conversion of thoracic and abdominal motion to lung volume, combining motion measurements correlated to flow-based measured tidal volume (normalised by subject weight) with R2 = 0.79 in data from 29 healthy adult subjects during panting, normal, and deep breathing at 0 cmH2O (ZEEP), 4 cmH2O, and 8 cmH2O PEEP (positive end-expiratory pressure). However, the correlation for individual subjects is substantially higher, indicating size and other physiological differences should be accounted for in scaling. The pattern of abdominal and chest expansion was captured, allowing for the analysis of muscular recruitment patterns over different breathing modes and the differentiation of active and passive modes. (4) Conclusions: The method and measuring device(s) enable the validation of patient-specific lung mechanics models and accurately elucidate diaphragmatic-driven volume changes due to intercostal/chest-wall muscular recruitment and elastic recoil.

Respiratory bi-directional pressure and flow data collection device with thoracic and abdominal circumferential monitoring.

Non-invasive pressure and flow data from Venturi-based sensors can be used with validated models to identify patient-specific lung mechanics. To validate applied respiratory models a secondary measurement is required. Rotary encoder-based tape measures were designed to capture change in circumference of a subject's thorax and diaphragm. Circumferential changes can be correlated to measured or modelled change in lung volume and associated muscular recruitment measures (patient work of breathing). Hence, these simple measurement devices can expedite respiratory research, by adding low-cost, accessible, and clinically useful measurements.

Determining the effects of insulin Detemir on endogenous secretion of insulin.

Type 2 diabetes (T2D) is a long-term metabolic disorder. A pilot trial was designed to investigate the effects of the long acting insulin Detemir on endogenous insulin secretion, to assess use in early T2D care. Provesn metabolic system models are used to identify patient-specific insulin sensitivity and endogenous insulin secretion from clinical data. Post-cardiac surgery patients with early T2D or pre-diabetes based on HbA1c were given a bolus of insulin Detemir on one day, and none on the second day in hospital. Blood glucose, insulin, C-Peptide, and all nutrition given are recorded. Early results from N=3 patients show 0.8-1.0U/hour insulin Detemir doses have no apparent suppression of endogenous insulin secretion, but does help lower glucose levels. The results show the model captures glucose-insulin dynamics in pre-diabetic post-surgical patients, and insulin Detemir may be useful to support individuals with pre-diabetes in reducing blood glucose levels. Tests with higher doses, need to be carried out to verify these results over a greater range of patients.