Biomedical subjects

Neil R Grubb

Publications and source records attributed to Neil R Grubb.

6 recordsLinked to original sources

PubMed2006

A fully automated algorithm for the determination of respiratory rate from the photoplethysmogram.

OBJECTIVE: To determine if an automatic algorithm using wavelet analysis techniques can be used to reliably determine respiratory rate from the photoplethysmogram (PPG). METHODS: Photoplethysmograms were obtained from 12 spontaneously breathing healthy adult volunteers. Three related wavelet transforms were automatically polled to obtain a measure of respiratory rate. This was compared with a secondary timing signal obtained by asking the volunteers to actuate a small push button switch, held in their right hand, in synchronisation with their respiration. In addition, individual breaths were resolved using the wavelet-method to identify the source of any discrepancies. RESULTS: Volunteer respiratory rates varied from 6.56 to 18.89 breaths per minute. Through training of the algorithm it was possible to determine a respiratory rate for all 12 traces acquired during the study. The maximum error between the PPG derived rates and the manually determined rate was found to be 7.9%. CONCLUSION: Our technique allows the accurate measurement of respiratory rate from the photoplethysmogram, and leads the way for developing a simple non-invasive combined respiration and saturation monitor.

Adult↗

PubMed2005

Post-discharge survival following pre-hospital cardiopulmonary arrest due to cardiac aetiology: temporal trends and impact of changes in clinical management.

AIMS: To determine whether survival after discharge following pre-hospital cardiopulmonary arrest has improved. METHODS AND RESULTS: The Heartstart Register was used to identify all 1659 patients discharged alive from Scottish hospitals during 1991-01 following pre-hospital arrest due to cardiac aetiology. The cohort was split into tertiles using year of arrest. A Cox proportional hazards model was used to determine risk of death relative to 1991-93. Patients who survived cardiopulmonary arrest in 1997-01 were less likely to die from any cause (unadjusted HR 0.60, 95% CI 0.48-0.75, P<0.001) or cardiac disease (unadjusted HR 0.50, 95% CI 0.38-0.65, P<0.001). After adjustment for case-mix, there remained significant declines in all-cause (adjusted HR 0.62, 95% CI 0.50-0.78, P<0.001) and cardiac death (adjusted HR 0.52, 95% CI 0.39-0.68, P<0.001). Clinical management had improved, with increased use of thrombolysis (47-63%, chi2 trend, P<0.001), beta-blockers (28-53%, chi2 trend, P<0.001), ACE-inhibitors (48-69%, chi2 trend, P<0.001), and anti-thrombotics (79-88%, chi2 trend, P<001). Adjustment for recorded changes in management attenuated the decline in all-cause death (adjusted HR 0.77, 95% CI 0.60-0.98, P=0.03). CONCLUSION: Survival following cardiopulmonary arrest has improved after adjusting for changes in case-mix. Better clinical management has contributed to this improvement.

Aged↗

PubMed2005

Hybrid long-term temporary pacing.

Prolonged temporary pacing is associated with frequent complications. We describe a patient with aortic endocarditis and acquired tri-fascicular block in whom back-up pacing was indicated. Using a Seldinger technique via a subclavian approach, a permanent active-fixation lead was positioned in the right ventricle. The lead was tunnelled subcutaneously for 6 cm, and the proximal end was connected to a standard single chamber pulse generator. The procedure was well tolerated and over a period of four months there were no complications or infection. The PR interval subsequently reduced in duration to 200 ms and as no episodes of AV block had occurred, the lead was easily removed with retraction of the helix and gentle traction.

Aged↗

PubMed2004

An algorithm for the detection of individual breaths from the pulse oximeter waveform.

OBJECTIVES: To determine if wavelet analysis techniques can be used to reliably identify individual breaths from the photoplethysmogram (PPG). METHODS: Photoplethysmograms were obtained from 22 healthy adult volunteers timing their respiration rate in synchronisation with a metronome. A secondary timing signal was obtained by asking the volunteers to actuate a small push button switch, held in their right hand, in synchronisation with their respiration. Each PPG was analyzed using primary wavelet decomposition and two new, related, secondary decompositions to determine the accuracy of individual breath detection. RESULTS: The optimal breath capture was obtained by manually polling the three techniques, allowing detection of 466 out of the 472 breaths studied; a detection rate of 98.7% with no false positive breaths detected. CONCLUSION: Our technique allows the accurate capture of individual breaths from the photoplethysmogram, and leads the way for developing a simple non-invasive combined respiration and saturation monitor.

Algorithms↗

PubMed2004

Wavelet-based analysis of heart-rate-dependent ECG features.

BACKGROUND: Wavelet-based methods of analyzing ECG signals have been used to identify specific features in cardiac arrhythmias. Since some of these features are rate dependent, it is a requirement that they are examined across a range of physiological heart rates. The wavelet transform is a signal analysis tool that can elucidate spectral and temporal information simultaneously from complex signals, including the ECG. The aim of this study was to identify the local frequency characteristics of the ECG using a real-time wavelet scalogram and to study the rate dependence of these features. METHODS: We examined the spectral temporal behavior of the local characteristics of the electrocardiogram (ECG) of 10 patients, in whom precise control of heart rate was achieved using right atrial pacing. Temporary reprogramming was used to adjust the paced atrial rate to predetermined values so that a rate-controlled rhythm was produced that closely resembled sinus rhythm. RESULTS: Rate-dependent features are seen on time-frequency scalograms. As the rate increases, the temporal spacing of features decrease and the frequency bands shift upward on the plot. Two patients with abnormal atrioventricular conduction demonstrate features of Wenckebach conduction and fusion. CONCLUSIONS: Characterization of the rate-dependent features of the ECG in a paced atrial rhythm by wavelet transform techniques has revealed some additional information not readily seen on single lead ECG analysis. This model provides a surrogate for changes that might be expected during rate changes in physiological sinus rhythm. It is envisaged that this method will offer advantages in detecting features of clinical significance that may not be readily seen by existing methods.

Arrhythmias, Cardiac↗

PubMed2003

In-hospital cardiac arrest leads to chronic memory impairment.

OBJECTIVE: To assess the prevalence and severity of memory deficits in a group of patients who survived an in-hospital cardiac arrest (IHCA) in comparison with patients resuscitated after cardiac arrest outside hospital (OHCA) and patients with acute myocardial infarction (MI). SUBJECTS: Thirty-five IHCA survivors, 35 OHCA survivors, and 35 patients who had suffered MI uncomplicated by cardiac arrest. PROCEDURE: Participants were assessed 8.2 (4.5) months after the event for current affective state (Hospital anxiety and depression scale (HADS)), pre-morbid intelligence (National adult reading test (NART)), short-term memory (digit span test) and long-term episodic memory (Rivermead behavioural memory test-RBMT). RESULTS: IHCA patients scored lower on the RBMT than MI controls but did not score significantly differently OHCA patients. Moderate or severe memory impairment was found in 26% of the IHCA group and 38% of the OHCA group. None of the MI group was found to have this degree of impairment. This difference in prevalence of memory impairment between the two cardiac arrest groups was not statistically significant. However, both arrest groups had significantly greater memory impairment than the MI control group. CONCLUSIONS: Clinically important memory impairment was found in one in four patients surviving IHCA. The shorter arrest durations that are thought to be associated with IHCA may not be sufficient to protect patients from memory impairment associated with cerebral hypoxia.

Adolescent↗