Foetal amplitude-integrated electroencephalography: proof of principle of a novel foetal monitoring technique in adult volunteers.

Peripartum hypoxic neonatal brain injury cannot be accurately predicted with current foetal monitoring techniques. Neonatal brain monitoring through amplitude-integrated electroencephalography (aEEG) is utilised when brain injury is suspected. Intrapartum aEEG assessment may improve detection of foetal hypoxia, facilitating earlier intervention. Using different engineered configurations in adult volunteers (n = 18), we monitored aEEG through application of two foetal scalp electrodes (FSEs). This aided development of a novel signal splitter, our Foetal heart rate and aEEG Monitoring System (FEMS) to monitor aEEG intrapartum. We then compared FEMS with gold-standard EEG monitoring simultaneously in two adults. Average percentage of interpretable aEEG signal was 61.3%, with the FEMS obtaining 72.15%. EEG signal on the aEEG device consistently showed a similar trace to gold standard EEG. This study demonstrates feasibility of aEEG monitoring in adults with FEMS utilising FSE inputs. An intrapartum foetal study utilising FEMS is due to commence shortly. IMPACT STATEMENTWhat is already known on this subject? Cardiotography, the current gold standard in foetal monitoring, is not associated with a reduction in cerebral palsy or infant mortality rates. Neonatal amplitude-integrated electroencephalography (aEEG) is an established method of monitoring brain function to guide commencing cooling therapy in suspected hypoxic brain injury. Intrapartum animal studies have illustrated foetal EEG changes reflecting evolving hypoxia.What do the results of this study add? This study demonstrates aEEG monitoring in human adult volunteers through application of foetal scalp electrodes and use of a novel signal splitter. This Foetal heart rate and aEEG Monitoring System (FEMS) provided a good overall percentage of aEEG signal, consistently showing a similar trace to gold standard EEG.What the implications are of these findings for clinical practice and/or further research? This proof of principle study provides the first step in developing a novel intrapartum foetal monitoring technique to monitor foetal aEEG in labour. This provides an exciting prospect of transferring well established neonatal monitoring techniques to facilitate accurate brain function assessment intrapartum and early intervention to reduce hypoxic brain injury. An intrapartum foetal study of this technology is due to begin in the near future.

Analysis of a random modulation single photon counting differential absorption lidar system for space-borne atmospheric CO2 sensing.

The ability to observe the Earth's carbon cycles from space provides scientists an important tool to analyze climate change. Current proposed systems are mainly based on pulsed integrated path differential absorption lidar, in which two high energy pulses at different wavelengths interrogate the atmosphere sequentially for its transmission properties and are back-scattered by the ground. In this work an alternative approach based on random modulation single photon counting is proposed and analyzed; this system can take advantage of a less power demanding semiconductor laser in intensity modulated continuous wave operation, benefiting from a better efficiency, reliability and radiation hardness. Our approach is validated via numerical simulations considering current technological readiness, demonstrating its potential to obtain a 1.5 ppm retrieval precision for 50 km averaging with 2.5 W average power in a space-borne scenario. A major limiting factor is the ambient shot noise, if ultra-narrow band filtering technology could be applied, 0.5 ppm retrieval precision would be attainable.

An optical technique for the measurement of thoracic wall movement during high-frequency jet ventilation.

Instrumentation for use in high-frequency jet ventilation is not currently capable of providing information suitable for predicting gas exchange. Whilst techniques for the accurate measurement of tidal volume during jet ventilation are now available, the relationship between tidal volume and the efficiency of gas exchange varies with frequency and inspiratory/expiratory time (I:E) ratio. We report technical details of a new non-invasive instrument capable of accurately measuring displacement of the thoracic wall at high frequencies and without electrical connection to the patient. It is hoped that use of this instrument will allow the calculation of an efficiency index for the transduction of airway pressure changes into peripheral expansion. It is also hoped that this index may be of value in predicting the gas exchange response to changes in jet parameters.

Portable directional ultrasonic Doppler blood velocimeter for ambulatory use.

The design of a portable directional Doppler velocimeter and of purpose-built probes intended for monitoring blood flow in femorodistal bypass grafts in ambulatory patients are described. The design is based on a continuous-wave Doppler technique with quadrature demodulation. The Doppler unit was interfaced to a 'personal-stereo' recorder to store the Doppler signals. The advantages and the limitations of recording flow in ambulatory patients are discussed. Examples of blood flow data collected from femorodistal bypass grafts are given.