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C Heneghan

Publications and source records attributed to C Heneghan.

At least 19 recordsLinked to original sources
PubMed2006

Self-monitoring of oral anticoagulation: a systematic review and meta-analysis.

BACKGROUND: Near-patient testing has made self-monitoring of anticoagulation with warfarin feasible, and several trials have suggested that such monitoring might be equal to or better than standard monitoring. We did a systematic review and meta-analysis of all randomised controlled trials that assessed the effects of self-monitoring or self-management (self-testing and self-dosage) of anticoagulation compared with standard monitoring. METHODS: We searched the Cochrane Register of Controlled Trials, MEDLINE, EMBASE to April 2005, and contacted manufacturers and authors of relevant studies. Outcomes analysed were: major haemorrhage, thromboembolic events, death, tests in range, minor haemorrhage, frequency of testing, and feasibility of self-monitoring. FINDINGS: We identified 14 randomised trials of self-monitoring: pooled estimates showed significant reductions in thromboembolic events (odds ratio 0.45, 95% CI 0.30-0.68), all-cause mortality (0.61, 0.38-0.98), and major haemorrhage (0.65, 0.42-0.99). Trials of combined self-monitoring and self-adjusted therapy showed significant reductions in thromboembolic events (0.27, 0.12-0.59) and death (0.37, 0.16-0.85), but not major haemorrhage (0.93, 0.42-2.05). No difference was noted in minor haemorrhage. 11 trials reported improvements in the mean proportion of international normalisation ratios in range. INTERPRETATION: Self-management improves the quality of oral anticoagulation. Patients capable of self-monitoring and self-adjusting therapy have fewer thromboembolic events and lower mortality than those who self-monitor alone. However, self-monitoring is not feasible for all patients, and requires identification and education of suitable candidates.

Adult↗
PubMed2003

Rectification and non-linear pre-processing of EMG signals for cortico-muscular analysis.

Rectification of the electromyographic (EMG) signal is a commonly used pre-processing procedure that allows detection of significant coherence between EMG and measured cortical signals. However, despite its accepted and wide-spread use, no detailed analysis has been presented to offer insight into the precise function of rectification. We begin this paper with arguments based on single motor unit action potential (AP) trains to demonstrate that rectification effectively enhances the firing rate information of the signal. Enhancement is achieved by shifting the peak of the AP spectrum toward the lower firing rate frequencies, whilst maintaining the firing rate spectra. A similar result is obtained using the analytic envelope of the signal extracted using the Hilbert transform. This argument is extended to simulated EMG signals generated using a published EMG model. Detection of firing rate frequencies is obtained using phase randomised surrogate data, where the original EMG power spectrum exceeds the averaged rectified surrogate spectra at integer multiples of firing rate frequencies. Model simulations demonstrate that this technique accurately determines grouped firing rate frequencies. Extraction of grouped firing rate frequencies prior to coherency analyses may further aid interpretation of significant cortico-muscular coherence findings.

Action Potentials↗
PubMed2002

Modulating effect of respiration on atrioventricular conduction time assessed using PR interval variation.

Respiratory sinus arrhythmia (RSA) is the variation of heart rate (or RR interval) in phase with respiration and has been extensively studied. However, the effect of respiration on atrioventricular conduction delay (and hence PR interval length) has not yet received much attention. This work reports on measurements of respiration and associated RR and PR variability, in 11 subjects, assessed through surface electrocardiogram measurements, for both paced and spontaneous respiration in the supine position. A wavelet-based approach was used to extract RR and PR intervals. The accuracy of RR and PR interval measurement was consistent with previously published work. Respiratory atrioventricular conduction delay variability (RCV) was assessed using three techniques: spectral, peak-to-trough and cosinor methods. All measures showed statistically significant variations in PR interval due to respiration during paced respiration at 6 min(-1). Of the three measures, cosinor analysis was most reliable in highlighting RCV. Using this measure, statistically significant RCV was seen in ten out of the 11 subjects during paced respiration. The magnitude of the variability was estimated as +/- 5.9% of the mean PR interval. In spontaneous respiration, statistically significant RCV was seen in approximately half of the subjects, with an estimated variability of +/- 1.5%. As a control, statistically significant values for RSA were also obtained from the same data, which agreed with previously published measurements. It was concluded that respiration does indeed modulate atrioventricular conduction delay, deep breathing in the supine position accentuates this effect, and cosinor analysis provides a reliable means for quantifying this effect.

Adult↗
PubMed2000

Establishing the relation between detrended fluctuation analysis and power spectral density analysis for stochastic processes

Stochastic fractal signals can be characterized by the Hurst coefficient H, which is related to the exponents of various power-law statistics characteristic of these processes. Two techniques widely used to estimate H are spectral analysis and detrended fluctuation analysis (DFA). This paper examines the analytical link between these two measures and shows that they are related through an integral transform. Numerical simulations confirm this relationship for ideal synthesized fractal signals. Their performance as estimators of H is compared based on a mean square error criterion and found to be similar. DFA measures are derived for physiological signals of heartbeat R-R intervals through the integral transform of a spectral density estimate. These agree with directly calculated DFA estimates, indicating that the relationship holds for signals with nonideal fractal properties. It is concluded that DFA and spectral measures provide equivalent characterizations of stochastic signals with long-term correlation.

Journal Article↗
PubMed1999

Teleconsultation in otolaryngology: live versus store and forward consultations.

OBJECTIVE: To evaluate the relative strengths and weaknesses of interactive and delayed teleconsultations in otolaryngology. SETTING: Ambulatory clinic at an urban tertiary care facility. SUBJECTS: Forty-five adult patients with known or suspected upper aerodigestive tract pathology. INTERVENTION: Patients were interviewed by an otolaryngology chief resident (CR) using a standardized protocol; the results were presented to a board-certified otolaryngologist present locally (LBCO) and a remote physician viewing the encounter by video-conferencing elsewhere in the hospital (RBCO). The CR performed a complete otolaryngologic examination, including fiberoptic nasopharyngolaryngoscopy. The CR and LBCO viewed the examination on a video monitor; the RBCO viewed the same image on the video-conferencing monitor. Each physician independently recorded findings and rendered a diagnosis. A third board-certified otolaryngologist, who reviewed the stored data file (text and stored images) in a delayed fashion (DBCO), documented his findings and made a diagnosis. RESULTS: The CR and LBCO agreed on diagnosis in 92% (36 of 39) of cases. The LBCO and RBCO arrived at the same diagnosis in 29 of 34 (85%) cases. The DBCO agreed with the LBCO for 18 of 28 (64%) diagnoses. Agreement on management recommendations between the LBCO/DBCO pair were also lower than for the LBCO/RBCO pair. CONCLUSIONS: Both interactive and delayed techniques can be used to provide relatively accurate clinical consultations in otolaryngology. Telemedicine can be applied for subspecialty consultations, screening programs, remote emergency triage, second opinions, and resident education.

Adult↗
PubMed1998

Telemedicine applications in otolaryngology.

A prospective study of the use of realtime and store-and-forward teleconsulting was carried out in patients who presented to the New York Eye and Ear Infirmary for otolaryngology care. Forty-five patients were seen in the study. There were no significant differences between local and remote otolaryngologists when interpreting the examinations, indicating that transmission did not affect the ability of a qualified physician to make an accurate diagnosis. In the store-and-forward examinations only 62% of the electronic records provided sufficient information for a confident diagnosis. Records were judged inadequate primarily due to poor selection, or an insufficient number of stored images. The study demonstrates that both interactive and store-and-forward techniques can be used to provide accurate clinical consultations in nasopharyngolaryngoscopic examinations. However, since store-and-forward consultations include less information and do not provide immediate feedback, as well defined clinical protocol for assembling the electronic consultation is needed.

Humans↗
PubMed1997

Fractal character of the neural spike train in the visual system of the cat.

We used a variety of statistical measures to identify the point process that describes the maintained discharge of retinal ganglion cells (RGC's) and neurons in the lateral geniculate nucleus (LGN) of the cat. These measures are based on both interevent intervals and event counts and include the interevent-interval histogram, rescaled range analysis, the event-number histogram, the Fano factor, Allan factor, and the periodogram. In addition, we applied these measures to surrogate versions of the data, generated by random shuffling of the order of interevent intervals. The continuing statistics reveal 1/f-type fluctuations in the data (long-duration power-law correlation), which are not present in the shuffled data. Estimates of the fractal exponents measured for RGC- and their target LGN-spike trains are similar in value, indicating that the fractal behavior either is transmitted form one cell to the other or has a common origin. The gamma-r renewal process model, often used in the analysis of visual-neuron interevent intervals, describes certain short-term features of the RGC and LGN data reasonably well but fails to account for the long-duration correlation. We present a new model for visual-system nerve-spike firings: a gamma-r renewal process whose mean is modulated by fractal binomial noise. This fractal, doubly stochastic point process characterizes the statistical behavior of both RGC and LGN data sets remarkably well.

Animals↗
PubMed1995

Shearing motion in the hearing organ measured by confocal laser heterodyne interferometry.

To investigate the presence of the postulated shearing motion in the micromechanics of the inner ear during sound stimulations we measured the vibratory response of the tectorial membrane and the reticular lamina in the third cochlear turn in an isolated temporal bone preparation using confocal laser heterodyne interferometry. The mechanical response of the tectorial membrane had the same frequency of maxima as the underlying reticular lamina, but was not as sharply tuned. When the two-dimensional motion was calculated from measurements made from several viewing angles it was found that the vibration of the reticular lamina had significant components both normal and tangential to its surface. The tectorial membrane motion, however, was primarily in a direction approximately perpendicular to the surface of the reticular lamina. The results indicate that shearing motion is produced predominantly by the radial motion of the reticular lamina.

Acoustic Stimulation↗
PubMed1993

Clinical and medicolegal aspects of conscious awareness during anesthesia.

In summary, regarding the legal aspects of awareness during anesthesia, the questions for the court to answer are: Was the patient aware? If probably yes, did the anesthesia technique cause or materially contribute to the awareness? Alternatively, if res ipsa loquitur applies, can the anesthesiologist show that the technique was not negligent, if necessary by showing that it would have been acceptable to at least a responsible minority of practitioners? It will be clear from the foregoing that good recordkeeping cannot be overemphasized. Apart from the fact that a precise and clear record tends to convince the court that they are dealing with a careful practitioner, the most important factor is that the more you have recorded about the anesthesia course, the more you will be able to tell the court about it. Finally, if you are unfortunate enough to lose and the patient is awarded damages, how much will the patient get? In the United Kingdom recently, $20,000 was awarded to patients for awareness in orthopedic and obstetric cases--perhaps a modest amount by U.S. standards. If the patient develops posttraumatic stress disorder, a much larger award is likely, especially if the patient is unable to work as a result of it; loss of earnings always increases an award, and it could easily reach $750,000 for a big earner. Insurance or other indemnity should cover this, of course, but it pays to remember one's likely exposure to risk in the event of failing to pay one's premium.

Anesthesia, General↗
PubMed1992

"The educated hand".

Explore the source record for details and available documents.

Anesthesia, Closed-Circuit↗