Biomedical subjects

B Lithgow

Publications and source records attributed to B Lithgow.

7 recordsLinked to original sources

PubMed2006

Non-invasive metabolic monitoring of patients under anaesthesia by continuous indirect calorimetry--an in vivo trial of a new method.

BACKGROUND: Oxygen uptake is an important form of metabolic monitoring for patients under anaesthesia. In critically ill patients oxygen uptake has been shown to provide valuable clinical information in directed therapy and acts as a useful monitor of cardiovascular dysfunction. A new method of continuous real time monitoring of metabolic gas exchange was tested in patients during anaesthesia. METHODS: Using a standard anaesthetic machine with attached semi-closed circle absorber system, oxygen uptake was measured continuously throughout surgery in 30 patients undergoing cardiopulmonary bypass surgery and compared with paired measurements made with the reverse Fick method. The method is an indirect calorimetry technique which uses fresh gas rotameters for control, regulation and measurement of the gas flows into the system, with continuous sampling of mixed exhaust gas. RESULTS: When compared with the reverse Fick method the oxygen uptake showed a mean difference (and sd) of 20.7 ml min(-1) or 12.1% (25.3 ml min(-1)) pre-bypass and 13.9 ml min(-1) or 8.1% (27.0 ml min(-1)) post-bypass. This bias is consistent with previous studies comparing oxygen uptake measured at the mouth against oxygen uptake by reverse Fick, which have shown a difference of approximately 10-15% accounted for by the consumption of oxygen by lung tissue. CONCLUSIONS: As the method allows continuous measurement of gas exchange and can be adapted to a modern anaesthetic workstation it is an attractive method for use in clinical setting.

Aged↗

PubMed2005

Modelling the vestibular head tilt response.

This paper attempts to verify the existence of potentially diagnostically significant periodic signals thought to exist in recordings of neural activity originating from the vestibular nerve, following a single tilt of the head. It then attempts to find the physiological basis of this signal, in particular focusing on the mechanical response of the vestibular system. Simple mechanical models of the semi circular canals having angular velocities applied to them were looked at. A simple single canal model was simulated using CFX software. Finally, a simple model of all three canals with elastic duct walls and a moving cupula was constructed. Pressure waves within the canals were simulated using water hammer or pressure transient theory. In particular, it was investigated whether pressure waves within the utricle following a square pulse angular velocity applied to the canal(s) may be responsible for quasi-periodic oscillatory signals. The simulations showed that there are no pressure waves resonating within the canals following a square pulse angular velocity applied to the canal(s). The results show that the oscillatory signals are most likely not mechanical in origin. It was concluded that further investigation is required.

Audiometry, Evoked Response↗

PubMed2005

Higher order statistical analysis of /x/ in male speech.

This paper presents a study of kurtosis analysis for the sound /x/ in male speech, /x/ is the sound of the 'o' at the end of words such as 'ago'. The sound analysed for this paper came from the Australian National Database of Spoken Language, more specifically the male speaker 17. The /x/ was isolated and extracted from the database by the author in a quiet booth using standard multimedia software. A 5 millisecond window was used for the analysis as it was shown previously by the author to be the most appropriate size for speech phoneme analysis. The significance of the research presented here is shown in the results where a majority of coefficients had a platykurtic (kurtosis between 0 and 3) value as opposed to the previously held leptokurtic (kurtosis > 3) belief.

Algorithms↗

PubMed2005

Biomedical engineering: impressions of developing areas in Australia.

This paper recognizes that Biomedical Engineering is a changing field affecting Biomedical Engineering curricula developers, investors and manufacturers in Australia. It reports on some of the attitudes of senior Biomedical Engineers to future developments in Biomedical Engineering in Australia.

Australia↗

PubMed2004

A vestibular diagnostic response.

The SP/AP ratio is a commonplace measure used in cochleography for detection of Meniere's disease (a pathology of the vestibular system). The measure is usually an averaged response to an acoustic stimulus. Franz described a process whereby the vestibular response rather than the cochlear response was used to elicit the SP/AP ratio. This paper examines that direct process. The direct process appears to detect a driven vestibular response, probably from the semicircular canals, at about 15Hz.

Algorithms↗

PubMed2004

Accuracy of the Foldes-Biro equation for measurement of oxygen uptake during anaesthesia: a laboratory simulation.

Laboratory benchtop testing was conducted of the Biro method for measurement of oxygen uptake from an anaesthetic breathing system by patients during low flow anaesthesia. A high precision flow and gas concentration measurement system was employed in conjunction with a physical gas exchange simulation model to test the theoretical basis of the method under controlled conditions. Simulated oxygen uptake values between 200 and 350 ml x min(-1) were modelled. The Biro-derived measurement of simulated O(2) uptake significantly underestimated the target value (mean difference -88.5 ml x min(-1), or -31.7%). The bias was directly proportional to the simulated O(2) uptake. The Biro method has a systematic bias that cannot be explained by random measurement imprecision.

Anesthesia, Inhalation↗

PubMed2000

Detection of microcalcifications using spatial filtering.

This paper studied the feasibility of applying a spatial filter, called the iris filter, in microcalcification detection. While a majority of techniques manipulate data in the transform space, this spatial filter was chosen in an attempt to reduce computation. The iris filter has the ability to differentiate between circular and line-like objects. It computes the convergence of nearby gradient vectors relative to the centre of the filter. However, as the results of this paper show, the decrease in the constraint factor, which is an inner limit of the support region of the filter, also leads to a decrease in the detection ability of the filter. Hence, this filter is not ideal for detection of microcalcifications.

Biophysical Phenomena↗