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Farajidavar A, O'Grady G, Rao SMN, Cheng LK, Abell T, Chiao JC. A miniature bidirectional telemetry system for in vivo gastric slow wave recordings. Physiol Meas 2012; 33:N29-37. [PMID: 22635054 DOI: 10.1088/0967-3334/33/6/n29] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Stomach contractions are initiated and coordinated by an underlying electrical activity (slow waves), and electrical dysrhythmias accompany motility diseases. Electrical recordings taken directly from the stomach provide the most valuable data, but face technical constraints. Serosal or mucosal electrodes have cables that traverse the abdominal wall, or a natural orifice, causing discomfort and possible infection, and restricting mobility. These problems motivated the development of a wireless system. The bidirectional telemetric system constitutes a front-end transponder, a back-end receiver and a graphical userinter face. The front-end module conditions the analogue signals, then digitizes and loads the data into a radio for transmission. Data receipt at the backend is acknowledged via a transceiver function. The system was validated in a bench-top study, then validated in vivo using serosal electrodes connected simultaneously to a commercial wired system. The front-end module was 35 × 35 × 27 mm3 and weighed 20 g. Bench-top tests demonstrated reliable communication within a distance range of 30 m, power consumption of 13.5 mW, and 124 h operation when utilizing a 560 mAh, 3 V battery. In vivo,slow wave frequencies were recorded identically with the wireless and wired reference systems (2.4 cycles min−1), automated activation time detection was modestly better for the wireless system (5% versus 14% FP rate), and signal amplitudes were modestly higher via the wireless system (462 versus 3 86μV; p<0.001). This telemetric system for slow wave acquisition is reliable,power efficient, readily portable and potentially implantable. The device will enable chronic monitoring and evaluation of slow wave patterns in animals and patients.0967-3334/
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Affiliation(s)
- Aydin Farajidavar
- Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA
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103
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O'Grady G, Du P, Paskaranandavadivel N, Angeli TR, Lammers WJEP, Asirvatham SJ, Windsor JA, Farrugia G, Pullan AJ, Cheng LK. Rapid high-amplitude circumferential slow wave propagation during normal gastric pacemaking and dysrhythmias. Neurogastroenterol Motil 2012; 24:e299-312. [PMID: 22709238 PMCID: PMC3383091 DOI: 10.1111/j.1365-2982.2012.01932.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Gastric slow waves propagate aborally as rings of excitation. Circumferential propagation does not normally occur, except at the pacemaker region. We hypothesized that (i) the unexplained high-velocity, high-amplitude activity associated with the pacemaker region is a consequence of circumferential propagation; (ii) rapid, high-amplitude circumferential propagation emerges during gastric dysrhythmias; (iii) the driving network conductance might switch between interstitial cells of Cajal myenteric plexus (ICC-MP) and circular interstitial cells of Cajal intramuscular (ICC-IM) during circumferential propagation; and (iv) extracellular amplitudes and velocities are correlated. METHODS An experimental-theoretical study was performed. High-resolution gastric mapping was performed in pigs during normal activation, pacing, and dysrhythmia. Activation profiles, velocities, and amplitudes were quantified. ICC pathways were theoretically evaluated in a bidomain model. Extracellular potentials were modeled as a function of membrane potentials. KEY RESULTS High-velocity, high-amplitude activation was only recorded in the pacemaker region when circumferential conduction occurred. Circumferential propagation accompanied dysrhythmia in 8/8 experiments was faster than longitudinal propagation (8.9 vs 6.9 mm s(-1) ; P = 0.004) and of higher amplitude (739 vs 528 μV; P = 0.007). Simulations predicted that ICC-MP could be the driving network during longitudinal propagation, whereas during ectopic pacemaking, ICC-IM could outpace and activate ICC-MP in the circumferential axis. Experimental and modeling data demonstrated a linear relationship between velocities and amplitudes (P < 0.001). CONCLUSIONS & INFERENCES The high-velocity and high-amplitude profile of the normal pacemaker region is due to localized circumferential propagation. Rapid circumferential propagation also emerges during a range of gastric dysrhythmias, elevating extracellular amplitudes and organizing transverse wavefronts. One possible explanation for these findings is bidirectional coupling between ICC-MP and circular ICC-IM networks.
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Affiliation(s)
- Gregory O'Grady
- Department of Surgery, The University of Auckland, New Zealand,Auckland Bioengineering Institute, The University of Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, New Zealand
| | | | - Timothy R. Angeli
- Auckland Bioengineering Institute, The University of Auckland, New Zealand
| | - Wim JEP Lammers
- Auckland Bioengineering Institute, The University of Auckland, New Zealand,Dept of Physiology, United Arab Emirates University, Al Ain, UAE
| | | | - John A. Windsor
- Department of Surgery, The University of Auckland, New Zealand
| | | | - Andrew J. Pullan
- Auckland Bioengineering Institute, The University of Auckland, New Zealand,Department of Engineering Science, The University of Auckland, New Zealand,Department of Surgery, Vanderbilt University, TN, USA
| | - Leo K. Cheng
- Auckland Bioengineering Institute, The University of Auckland, New Zealand,Department of Surgery, Vanderbilt University, TN, USA
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Paskaranandavadivel N, Cheng LK, Du P, O'Grady G, Pullan AJ. Improved signal processing techniques for the analysis of high resolution serosal slow wave activity in the stomach. Annu Int Conf IEEE Eng Med Biol Soc 2012; 2011:1737-40. [PMID: 22254662 DOI: 10.1109/iembs.2011.6090497] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
High resolution electrical mapping of slow waves on the stomach serosa has improved our understanding of gastric electrical activity in normal and diseased states. In order to assess the signals acquired from high resolution mapping, a robust framework is required. Our framework is semi-automated and allows for rapid processing, analysis and interpretation of slow waves via qualitative and quantitative measures including isochronal activation time mapping, and velocity and amplitude mapping. Noise removal techniques were validated for raw recorded signals, where three filters were evaluated for baseline drift removal and three filters for removal of high frequency interference. For baseline drift removal, the Gaussian moving median filter was most effective, while for eliminating high frequency interference the Savitzky Golay filter was the most effective. Methods for assessing slow wave velocity and amplitude were investigated. To estimate slow wave velocity, a finite difference approach with interpolation and smoothing was used. To evaluate the slow wave amplitude and width, a peak and trough method based on Savitzky Golay derivative filters was used. Together, these methods constitute a significantly improved framework for analyzing gastric high resolution mapping data.
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105
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Yassi R, O'Grady G, Paskaranandavadivel N, Du P, Angeli TR, Pullan AJ, Cheng LK, Erickson JC. The gastrointestinal electrical mapping suite (GEMS): software for analyzing and visualizing high-resolution (multi-electrode) recordings in spatiotemporal detail. BMC Gastroenterol 2012; 12:60. [PMID: 22672254 PMCID: PMC3464652 DOI: 10.1186/1471-230x-12-60] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 06/06/2012] [Indexed: 11/25/2022] Open
Abstract
Background Gastrointestinal contractions are controlled by an underlying bioelectrical activity. High-resolution spatiotemporal electrical mapping has become an important advance for investigating gastrointestinal electrical behaviors in health and motility disorders. However, research progress has been constrained by the low efficiency of the data analysis tasks. This work introduces a new efficient software package: GEMS (Gastrointestinal Electrical Mapping Suite), for analyzing and visualizing high-resolution multi-electrode gastrointestinal mapping data in spatiotemporal detail. Results GEMS incorporates a number of new and previously validated automated analytical and visualization methods into a coherent framework coupled to an intuitive and user-friendly graphical user interface. GEMS is implemented using MATLAB®, which combines sophisticated mathematical operations and GUI compatibility. Recorded slow wave data can be filtered via a range of inbuilt techniques, efficiently analyzed via automated event-detection and cycle clustering algorithms, and high quality isochronal activation maps, velocity field maps, amplitude maps, frequency (time interval) maps and data animations can be rapidly generated. Normal and dysrhythmic activities can be analyzed, including initiation and conduction abnormalities. The software is distributed free to academics via a community user website and forum (http://sites.google.com/site/gimappingsuite). Conclusions This software allows for the rapid analysis and generation of critical results from gastrointestinal high-resolution electrical mapping data, including quantitative analysis and graphical outputs for qualitative analysis. The software is designed to be used by non-experts in data and signal processing, and is intended to be used by clinical researchers as well as physiologists and bioengineers. The use and distribution of this software package will greatly accelerate efforts to improve the understanding of the causes and clinical consequences of gastrointestinal electrical disorders, through high-resolution electrical mapping.
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Affiliation(s)
- Rita Yassi
- Auckland Bioengineering Institute, Department of Surgery, The University of Auckland, Auckland, New Zealand
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106
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Jamal A, O'Grady G, Harnett E, Dalton D, Andresen D. Republished: Improving hand hygiene in a paediatric hospital: a multimodal quality improvement approach. Postgrad Med J 2012; 88:353-8. [DOI: 10.1136/pgmj-2011-000056rep] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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107
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O'Grady G, Harper S, Loveday B, Adams B, Civil ID, Peters M. Appropriate working hours for surgical training according to Australasian trainees. ANZ J Surg 2012; 82:225-9. [DOI: 10.1111/j.1445-2197.2011.05992.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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108
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Jamal A, O'Grady G, Harnett E, Dalton D, Andresen D. Improving hand hygiene in a paediatric hospital: a multimodal quality improvement approach. BMJ Qual Saf 2012; 21:171-6. [DOI: 10.1136/bmjqs-2011-000056] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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109
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Paskaranandavadivel N, O'Grady G, Du P, Pullan AJ, Cheng LK. An improved method for the estimation and visualization of velocity fields from gastric high-resolution electrical mapping. IEEE Trans Biomed Eng 2011; 59:882-9. [PMID: 22207635 DOI: 10.1109/tbme.2011.2181845] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
High-resolution (HR) electrical mapping is an important clinical research tool for understanding normal and abnormal gastric electrophysiology. Analyzing velocities of gastric electrical activity in a reliable and accurate manner can provide additional valuable information for quantitatively and qualitatively comparing features across and within subjects, particularly during gastric dysrhythmias. In this study, we compared three methods of estimating velocities from HR recordings to determine which method was the most reliable for use with gastric HR electrical mapping. The three methods were 1) simple finite difference (FD) 2) smoothed finite difference (FDSM), and 3) a polynomial-based method. With synthetic data, the accuracy of the simple FD method resulted in velocity errors almost twice that of the FDSM and the polynomial-based method, in the presence of activation time error up to 0.5 s. With three synthetic cases under various noise types and levels, the FDSM resulted in average speed error of 3.2% and an average angle error of 2.0° and the polynomial-based method had an average speed error of 3.3% and an average angle error of 1.7°. With experimental gastric slow wave recordings performed in pigs, the three methods estimated similar velocities (6.3-7.3 mm/s), but the FDSM method had a lower standard deviation in its velocity estimate than the simple FD and the polynomial-based method, leading it to be the method of choice for velocity estimation in gastric slow wave propagation. An improved method for visualizing velocity fields is also presented.
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110
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Lees-Green R, Du P, O'Grady G, Beyder A, Farrugia G, Pullan AJ. Biophysically based modeling of the interstitial cells of cajal: current status and future perspectives. Front Physiol 2011; 2:29. [PMID: 21772822 PMCID: PMC3131535 DOI: 10.3389/fphys.2011.00029] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 06/13/2011] [Indexed: 12/29/2022] Open
Abstract
Gastrointestinal motility research is progressing rapidly, leading to significant advances in the last 15 years in understanding the cellular mechanisms underlying motility, following the discovery of the central role played by the interstitial cells of Cajal (ICC). As experimental knowledge of ICC physiology has expanded, biophysically based modeling has become a valuable tool for integrating experimental data, for testing hypotheses on ICC pacemaker mechanisms, and for applications in in silico studies including in multiscale models. This review is focused on the cellular electrophysiology of ICC. Recent evidence from both experimental and modeling domains have called aspects of the existing pacemaker theories into question. Therefore, current experimental knowledge of ICC pacemaker mechanisms is examined in depth, and current theories of ICC pacemaking are evaluated and further developed. Existing biophysically based ICC models and their physiological foundations are then critiqued in light of the recent advances in experimental knowledge, and opportunities to improve these models are identified. The review concludes by examining several potential clinical applications of biophysically based ICC modeling from the subcellular through to the organ level, including ion channelopathies and ICC network degradation.
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Affiliation(s)
- Rachel Lees-Green
- Auckland Bioengineering Institute, The University of Auckland Auckland, New Zealand
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111
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Davidson JB, O'Grady G, Arkwright JW, Zarate N, Scott SM, Pullan AJ, Dinning PJ. Anatomical registration and three-dimensional visualization of low and high-resolution pan-colonic manometry recordings. Neurogastroenterol Motil 2011; 23:387-90, e171. [PMID: 21199536 PMCID: PMC3080460 DOI: 10.1111/j.1365-2982.2010.01651.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND Colonic propagating sequences (PS) are important for the movement of colonic content and defecation, and aberrant PS patterning has been associated with slow transit constipation. However, because these motor patterns are typically recorded over long periods (24 h +), the visualization of PS spatiotemporal patterning is difficult. Here, we develop a novel method for displaying pan-colonic motility patterns. METHODS A 3D mesh representing the geometry of the human colon was created as follows: (i) Human colon images from the Visible Human Dataset were digitized to create a 3D data cloud, and (ii) A surface mesh was fitted to the cloud using a least-squares minimization technique. Colonic manometry catheters were placed in the ascending colon of healthy controls and patients with slow transit constipation (STC), with the aid of a colonoscope. The colonic manometry data were interpolated and mapped to the model according to the following anatomical landmarks: cecum, hepatic flexure, splenic flexure, sigmoid-descending junction, and anus. KEY RESULTS These 3D images clearly and intuitively communicate characteristics of normal and abnormal colonic motility. Specifically we have shown the reduced amplitude of the antegrade propagating pressure waves (PPW) throughout the colon and reduced frequency of PPWs at the mid-colon in patients with STC. CONCLUSIONS AND INFERENCES A novel method for the 3D visualization of PS is presented, providing an intuitive method for representing a large volume of physiological data. These techniques can be used to display frequency, amplitude or velocity data, and will help to convey regions of abnormally in patient populations.
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Affiliation(s)
- J B Davidson
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
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112
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O'Grady G, Paskaranandavadivel N, Angeli TR, Du P, Windsor JA, Cheng LK, Pullan AJ. A comparison of gold versus silver electrode contacts for high-resolution gastric electrical mapping using flexible printed circuit board arrays. Physiol Meas 2011; 32:N13-22. [PMID: 21252419 PMCID: PMC4127313 DOI: 10.1088/0967-3334/32/3/n02] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Stomach contractions are initiated and coordinated by electrical events termed slow waves, and slow wave abnormalities contribute to gastric motility disorders. Recently, flexible printed circuit board (PCB) multi-electrode arrays were introduced, facilitating high-resolution mapping of slow wave activity in humans. However PCBs with gold contacts have shown a moderately inferior signal quality to previous custom-built silver-wire platforms, potentially limiting analyses. This study determined if using silver instead of gold contacts improved flexible PCB performance. In a salt-bath test, modestly higher stimulus amplitudes were recorded from silver PCBs (mean 312, s.d. 89 µV) than those from gold (mean 281, s.d. 85 µV) (p < 0.001); however, the signal-to-noise ratio (SNR) was similar (p = 0.26). In eight in vivo experimental studies, involving gastric serosal recordings from five pigs, no silver versus gold differences were found in terms of slow wave amplitudes (mean 677 versus 682 µV; p = 0.91), SNR (mean 8.8 versus 8.8 dB; p = 0.94) or baseline drift (NRMS; mean 12.0 versus 12.1; p = 0.97). Under the prescribed conditions, flexible PCBs with silver or gold contacts provide comparable results in vivo, and contact material difference does not explain the performance difference between current-generation slow wave mapping platforms. Alternative explanations for this difference and the implications for electrode design are discussed.
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Affiliation(s)
- G O'Grady
- Department of Surgery, University of Auckland, New Zealand. Auckland Bioengineering Institute, University of Auckland, New Zealand.
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113
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Du P, O'Grady G, Cheng LK, Pullan AJ. A multiscale model of the electrophysiological basis of the human electrogastrogram. Biophys J 2011; 99:2784-92. [PMID: 21044575 DOI: 10.1016/j.bpj.2010.08.067] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 08/16/2010] [Accepted: 08/27/2010] [Indexed: 11/25/2022] Open
Abstract
The motility of the stomach is coordinated by an electrical activity termed "slow waves", and slow-wave dysrhythmias contribute to motility disorders. One major method for clinically evaluating gastric dysrhythmias has been electrogastrography (EGG); however, the clinical utility of EGG is limited partly due to the uncertainty regarding its electrophysiological basis. In this study, a multiscale model of gastric slow waves was generated from a biophysically based continuum description of cellular electrical events, coupled with a subject-specific human stomach model and high-resolution electrical mapping data. The model was then applied using a forward-modeling approach, within an anatomical torso model, to define how slow wave activity summates to generate the EGG potentials. The simulated EGG potentials were shown to be spatially varying in amplitude (0.27-0.33 mV) and duration (9.2-15.3 s), and the sources of this variance were quantified with respect to the activation timings of the underlying slow wave activity. This model constitutes an improved theory of the electrophysiological basis of the EGG, and offers a framework for optimizing the placement of EGG electrodes, and for interpreting the EGG changes occurring in disease states.
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Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, The University of Auckland, New Zealand.
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114
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Abstract
The functions of the gastrointestinal (GI) tract include digestion, absorption, excretion, and protection. In this review, we focus on the electrical activity of the stomach and small intestine, which underlies the motility of these organs, and where the most detailed systems descriptions and computational models have been based to date. Much of this discussion is also applicable to the rest of the GI tract. This review covers four major spatial scales: cell, tissue, organ, and torso, and discusses the methods of investigation and the challenges associated with each. We begin by describing the origin of the electrical activity in the interstitial cells of Cajal, and its spread to smooth muscle cells. The spread of electrical activity through the stomach and small intestine is then described, followed by the resultant electrical and magnetic activity that may be recorded on the body surface. A number of common and highly symptomatic GI conditions involve abnormal electrical and/or motor activity, which are often termed functional disorders. In the last section of this review we address approaches being used to characterize and diagnose abnormalities in the electrical activity and how these might be applied in the clinical setting. The understanding of electrophysiology and motility of the GI system remains a challenging field, and the review discusses how biophysically based mathematical models can help to bridge gaps in our current knowledge, through integration of otherwise separate concepts.
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Affiliation(s)
- Leo K Cheng
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1142, New Zealand
| | - Gregory O'Grady
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1142, New Zealand.,Department of Surgery, The University of Auckland, Auckland 1142, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1142, New Zealand.,Department of Surgery, The University of Auckland, Auckland 1142, New Zealand
| | - John U Egbuji
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1142, New Zealand.,Department of Surgery, The University of Auckland, Auckland 1142, New Zealand
| | - John A Windsor
- Department of Surgery, The University of Auckland, Auckland 1142, New Zealand
| | - Andrew J Pullan
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1142, New Zealand.,Department of Engineering Science, The University of Auckland, Auckland 1142, New Zealand.,Department of Surgery, Vanderbilt University, Nashville, TN 37235-5225
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Angeli TR, O'Grady G, Erickson JC, Du P, Paskaranandavadivel N, Bissett IP, Cheng LK, Pullan AJ. Mapping small intestine bioelectrical activity using high-resolution printed-circuit-board electrodes. Annu Int Conf IEEE Eng Med Biol Soc 2011; 2011:4951-4954. [PMID: 22255449 PMCID: PMC4076342 DOI: 10.1109/iembs.2011.6091227] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this study, novel methods were developed for the in-vivo high-resolution recording and analysis of small intestine bioelectrical activity, using flexible printed-circuit-board (PCB) electrode arrays. Up to 256 simultaneous recordings were made at multiple locations along the porcine small intestine. Data analysis was automated through the application and tuning of the Falling-Edge Variable-Threshold algorithm, achieving 92% sensitivity and a 94% positive-predictive value. Slow wave propagation patterns were visualized through the automated generation of animations and isochronal maps. The methods developed and validated in this study are applicable for use in humans, where future studies will serve to improve the clinical understanding of small intestine motility in health and disease.
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116
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O'Grady G, Loveday B, Harper S, Adams B, Civil ID, Peters M. Working hours and roster structures of surgical trainees in Australia and New Zealand. ANZ J Surg 2010; 80:890-5. [DOI: 10.1111/j.1445-2197.2010.05528.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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117
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O'Grady G, Du P, Cheng LK, Egbuji JU, Lammers WJEP, Windsor JA, Pullan AJ. Origin and propagation of human gastric slow-wave activity defined by high-resolution mapping. Am J Physiol Gastrointest Liver Physiol 2010; 299:G585-92. [PMID: 20595620 PMCID: PMC2950696 DOI: 10.1152/ajpgi.00125.2010] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Slow waves coordinate gastric motility, and abnormal slow-wave activity is thought to contribute to motility disorders. The current understanding of normal human gastric slow-wave activity is based on extrapolation from data derived from sparse electrode recordings and is therefore potentially incomplete. This study employed high-resolution (HR) mapping to reevaluate human gastric slow-wave activity. HR mapping was performed in 12 patients with normal stomachs undergoing upper abdominal surgery, using flexible printed circuit board (PCB) arrays (interelectrode distance 7.6 mm). Up to six PCBs (192 electrodes; 93 cm(2)) were used simultaneously. Slow-wave activity was characterized by spatiotemporal mapping, and regional frequencies, amplitudes, and velocities were defined and compared. Slow-wave activity in the pacemaker region (mid to upper corpus, greater curvature) was of greater amplitude (mean 0.57 mV) and higher velocity (8.0 mm/s) than the corpus (0.25 mV, 3.0 mm/s) (P < 0.001) and displayed isotropic propagation. A marked transition to higher amplitude and velocity activity occurred in the antrum (0.52 mV, 5.9 mm/s) (P < 0.001). Multiple (3-4) wavefronts were found to propagate simultaneously in the organoaxial direction. Frequencies were consistent between regions (2.83 +/- 0.35 cycles per min). HR mapping has provided a more complete understanding of normal human gastric slow-wave activity. The pacemaker region is associated with high-amplitude, high-velocity activity, and multiple wavefronts propagate simultaneously. These data provide a baseline for future HR mapping studies in disease states and will inform noninvasive diagnostic strategies.
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Affiliation(s)
| | - Peng Du
- 2Auckland Bioengineering Institute, and
| | | | - John U. Egbuji
- 1Department of Surgery, ,2Auckland Bioengineering Institute, and
| | - Wim J. E. P. Lammers
- 2Auckland Bioengineering Institute, and ,3Department of Physiology, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | | | - Andrew J. Pullan
- 2Auckland Bioengineering Institute, and ,4Department of Engineering Science, The University of Auckland, Auckland, New Zealand; ,5Department of Surgery, Vanderbilt University, Nashville, Tennessee
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Adams BM, O'Grady G, Pole JR. The New Zealand Advanced Choice of Employment (ACE) Scheme: analysis after 7 years of District Health Board cooperation in a competitive employment context. N Z Med J 2010; 123:34-42. [PMID: 20651865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
AIM The Advanced Choice of Employment Scheme (ACE) coordinates the appointment of postgraduate year 1 doctors in New Zealand (NZ). ACE is a voluntary collaborative operation by all 21 of NZ's District Health Boards (DHBs). This audit evaluates the performance of ACE over its first 7 years of operation. METHODS The proportion of applicants successfully matched and the correlation between their preferred and matched DHBs was evaluated. Qualitative performance was assessed through survey of NZ trainee interns (TIs). RESULTS Nearly all (99-100%) NZ TIs using ACE have been successfully matched each year. Most (96-99%) of the successful applicants have been matched to one of their top-four preferred DHBs, and a mean of 81% to their most-preferred choice. Qualitative satisfaction with ACE was high (90% good). Applicant concerns included the usability of the online application portal and uncertainty about the fairness of the ACE algorithm. CONCLUSION The ACE scheme has been highly successful for allocating PGY1 positions over 7 years and achieves generally high applicant satisfaction. DHBs have successfully cooperated despite their competing interest in recruiting top applicants. This study supports the contention that increased collaboration between DHBs may improve efficiency within the NZ health sector.
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Affiliation(s)
- Brandon M Adams
- Department of Plastic Surgery, Middlemore Hospital, Auckland, New Zealand.
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O'Grady G, Du P, Lammers WJEP, Egbuji JU, Mithraratne P, Chen JDZ, Cheng LK, Windsor JA, Pullan AJ. High-resolution entrainment mapping of gastric pacing: a new analytical tool. Am J Physiol Gastrointest Liver Physiol 2010; 298:G314-21. [PMID: 19926815 PMCID: PMC2822498 DOI: 10.1152/ajpgi.00389.2009] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gastric pacing has been investigated as a potential treatment for gastroparesis. New pacing protocols are required to improve symptom and motility outcomes; however, research progress has been constrained by a limited understanding of the effects of electrical stimulation on slow-wave activity. This study introduces high-resolution (HR) "entrainment mapping" for the analysis of gastric pacing and presents four demonstrations. Gastric pacing was initiated in a porcine model (typical amplitude 4 mA, pulse width 400 ms, period 17 s). Entrainment mapping was performed using flexible multielectrode arrays (</=192 electrodes; 92 cm(2)) and was analyzed using novel software methods. In the first demonstration, entrainment onset was quantified over successive waves in spatiotemporal detail. In the second demonstration, slow-wave velocity was accurately determined with HR field analysis, and paced propagation was found to be anisotropic (longitudinal 2.6 +/- 1.7 vs. circumferential 4.5 +/- 0.6 mm/s; P < 0.001). In the third demonstration, a dysrhythmic episode that occurred during pacing was mapped in HR, revealing an ectopic slow-wave focus and uncoupled propagations. In the fourth demonstration, differences were observed between paced and native slow-wave amplitudes (0.24 +/- 0.08 vs. 0.38 +/- 0.14 mV; P < 0.001), velocities (6.2 +/- 2.8 vs. 11.5 +/- 4.7 mm/s; P < 0.001), and activated areas (20.6 +/- 1.9 vs. 32.8 +/- 2.6 cm(2); P < 0.001). Entrainment mapping enables an accurate quantification of the effects of gastric pacing on slow-wave activity, offering an improved method to assess whether pacing protocols are likely to achieve physiologically and clinically useful outcomes.
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Affiliation(s)
- Gregory O'Grady
- Department of Surgery, and Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
| | | | - Wim J. E. P. Lammers
- 5Engineering Science, and ,2Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand;
| | | | | | - Jiande D. Z. Chen
- 3Department of Physiology, United Arab Emirates University, Al Ain, United Arab Emirates;
| | | | | | - Andrew J. Pullan
- 5Engineering Science, and ,4Division of Gastroenterology, University of Texas Medical Branch, Galveston, Texas; ,6Department of Surgery, Vanderbilt University, Nashville, Tennessee
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Erickson JC, O'Grady G, Du P, Obioha C, Qiao W, Richards WO, Bradshaw LA, Pullan AJ, Cheng LK. Falling-edge, variable threshold (FEVT) method for the automated detection of gastric slow wave events in high-resolution serosal electrode recordings. Ann Biomed Eng 2009; 38:1511-29. [PMID: 20024624 DOI: 10.1007/s10439-009-9870-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Accepted: 12/07/2009] [Indexed: 10/20/2022]
Abstract
High resolution (HR) multi-electrode mapping is increasingly being used to evaluate gastrointestinal slow wave behaviors. To create the HR activation time (AT) maps from gastric serosal electrode recordings that quantify slow wave propagation, it is first necessary to identify the AT of each individual slow wave event. Identifying these ATs has been a time consuming task, because there has previously been no reliable automated detection method. We have developed an automated AT detection method termed falling-edge, variable threshold (FEVT) detection. It computes a detection signal transform to accentuate the high 'energy' content of the falling edges in the serosal recording, and uses a running median estimator of the noise to set the time-varying detection threshold. The FEVT method was optimized, validated, and compared to other potential algorithms using in vivo HR recordings from a porcine model. FEVT properly detects ATs in a wide range of waveforms, making its performance substantially superior to the other methods, especially for low signal-to-noise ratio (SNR) recordings. The algorithm offered a substantial time savings (>100 times) over manual-marking whilst achieving a highly satisfactory sensitivity (0.92) and positive-prediction value (0.89).
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Du P, Li S, O'Grady G, Cheng LK, Pullan AJ, Chen JDZ. Effects of electrical stimulation on isolated rodent gastric smooth muscle cells evaluated via a joint computational simulation and experimental approach. Am J Physiol Gastrointest Liver Physiol 2009; 297:G672-80. [PMID: 19661149 PMCID: PMC2763803 DOI: 10.1152/ajpgi.00149.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gastric electrical stimulation (GES) involves the delivery of electrical impulses to the stomach for therapeutic purposes. New GES protocols are needed that are optimized for improved motility outcomes and energy efficiency. In this study, a biophysically based smooth muscle cell (SMC) model was modified on the basis of experimental data and employed in conjunction with experimental studies to define the effects of a large range of GES protocols on individual SMCs. For the validation studies, rat gastric SMCs were isolated and subjected to patch-clamp analysis during stimulation. Experimental results were in satisfactory agreement with simulation results. The results define the effects of a wide range of GES parameters (pulse width, amplitude, and pulse-train frequency) on isolated SMCs. The minimum pulse width required to invoke a supramechanical threshold response from SMCs (defined at -30 mV) was 65 ms (at 250-pA amplitude). The minimum amplitude required to invoke this threshold was 75 pA (at 1,000-ms pulse width). The amplitude of the invoked response beyond this threshold was proportional to the stimulation amplitude. A high-frequency train of stimuli (40 Hz; 10 ms, 150 pA) could invoke and maintain the SMC plateau phase while requiring 60% less power and accruing approximately 30% less intracellular Ca(2+) concentration during the plateau phase than a comparable single-pulse protocol could in a demonstrated example. Validated computational simulations are an effective strategy for efficiently identifying effective minimum-energy GES protocols, and pulse-train protocols may also help to reduce the power consumption of future GES devices.
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Affiliation(s)
- P. Du
- 1Auckland Bioengineering Institute,
| | - S. Li
- 2Veterans Research and Education Foundation, Oklahoma Veterans Affairs Medical Center, Oklahoma City, Oklahoma;
| | - G. O'Grady
- 1Auckland Bioengineering Institute, ,3Department of Surgery, and
| | | | - A. J. Pullan
- 1Auckland Bioengineering Institute, ,4Department of Engineering Science, The University of Auckland, Auckland, New Zealand; ,5Department of Surgery, Vanderbilt University, Nashville, Tennessee; and
| | - J. D. Z. Chen
- 2Veterans Research and Education Foundation, Oklahoma Veterans Affairs Medical Center, Oklahoma City, Oklahoma; ,6Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas
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Samson P, O'Grady G, Keating J. An international comparison study of stage of colorectal cancer at diagnosis: how does New Zealand compare? N Z Med J 2009; 122:74-83. [PMID: 19465950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
AIM The high incidence rates of colorectal cancer (CRC) in New Zealand (NZ) are well publicised. Minimal information is available comparing national extent of this disease at time of diagnosis with other countries, especially countries now performing screening for CRC. Just how late do our cancers present? What is the difference compared with other countries now performing screening? METHOD Data were retrieved and analysed from the World Health Organization and Cancer Registries in New Zealand and five other countries from 2001-2004. Extent of disease was classified as localised, regional, distant and unknown. RESULTS NZ has the lowest percentage of surgically curable localised disease (28%) when compared with Australia (New South Wales) (34%), United Kingdom (42%), American (SEER-9) (40%) and Hong Kong (35%) data. 20% of disease at diagnosis in NZ is metastatic. CONCLUSION By international standards, NZ has a marked and previously undefined low rate of early stage diagnosis of CRC. Extent of disease is more advanced in New Zealand patients than in other countries with recently commenced screening programmes (e.g. Australia and the UK). In 2001, NZ also had the highest age-specific incidence of colorectal cancer in the 50-70 years age group, when compared with Australia, USA, UK and Japan. Colorectal cancer will continue to be a significant health issue for the NZ population, with predicted increasing total numbers of people affected, and increasing costs of chemotherapy for advanced cancer. The concerning international comparisons shown in this article further emphasize the need for more immediate strategies to improve rates of early stage colorectal cancers at time of diagnosis.
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Affiliation(s)
- Paul Samson
- Department of General Surgery, Wellington Hospital, Capital & Coast District Health Board, Wellington.
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Du P, O'Grady G, Egbuji JU, Lammers WJ, Budgett D, Nielsen P, Windsor JA, Pullan AJ, Cheng LK. High-resolution mapping of in vivo gastrointestinal slow wave activity using flexible printed circuit board electrodes: methodology and validation. Ann Biomed Eng 2009; 37:839-46. [PMID: 19224368 DOI: 10.1007/s10439-009-9654-9] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 02/06/2009] [Indexed: 01/27/2023]
Abstract
High-resolution, multi-electrode mapping is providing valuable new insights into the origin, propagation, and abnormalities of gastrointestinal (GI) slow wave activity. Construction of high-resolution mapping arrays has previously been a costly and time-consuming endeavor, and existing arrays are not well suited for human research as they cannot be reliably and repeatedly sterilized. The design and fabrication of a new flexible printed circuit board (PCB) multi-electrode array that is suitable for GI mapping is presented, together with its in vivo validation in a porcine model. A modified methodology for characterizing slow waves and forming spatiotemporal activation maps showing slow waves propagation is also demonstrated. The validation study found that flexible PCB electrode arrays are able to reliably record gastric slow wave activity with signal quality near that achieved by traditional epoxy resin-embedded silver electrode arrays. Flexible PCB electrode arrays provide a clinically viable alternative to previously published devices for the high-resolution mapping of GI slow wave activity. PCBs may be mass-produced at low cost, and are easily sterilized and potentially disposable, making them ideally suited to intra-operative human use.
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Affiliation(s)
- Peng Du
- Bioengineering Institute, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
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Pole R, O'Grady G, Adams B. Analysis of the Advanced Choice of Employment (ACE) scheme for facilitation of first-year house officer appointments in New Zealand. N Z Med J 2004; 117:U1120. [PMID: 15505667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
AIM To determine the success of the Advanced Choice of Employment (ACE) scheme, a computerised matching system introduced to facilitate the recruitment of first-year house officers in New Zealand. METHODS ACE data was examined for demographics and employment outcomes in 2003 and 2004. Qualitative satisfaction was assessed via email survey of trainee intern applicants in 2003. RESULTS All first-year house officer positions were filled within one round of matching. New Zealand trainee intern graduates were more successful than other applicant groups. The majority of successful applicants were employed by their most preferred hospital and 96% in one of their top four choices in both years. Tertiary centres were preferred over secondary centres. Survey demonstrated generally high satisfaction. CONCLUSIONS The ACE scheme proved highly efficient and successfully accounted for applicant preferences. In addition, the emergence of centralised application data may improve workforce planning and increase retention of graduates.
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Abstract
Curriculum pressures and a decline in hospital autopsy rates have reduced the opportunity for medical students to learn from autopsy findings
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Affiliation(s)
- Gregory O'Grady
- New Zealand Medical Students' Association, 55a Rugby Street, Mount Cook, Wellington, New Zealand.
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O'Grady G, Pettit T, Ng J, Frith R. Experiences with recreational drugs amongst first-year students at Auckland University. N Z Med J 2003; 116:U426. [PMID: 12740616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
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Abstract
In a recent Lancet Case report, a patient presented with subacute combined degeneration of the spinal cord after recreational use of nitrous oxide (N2O). There is very little information about use of this substance as a recreational drug. In a questionnaire-based study, we surveyed 1782 students in their first year at the University of Auckland, New Zealand. 1360 (76%) questionnaires were completed and consistent. 780 (57%) students were aware of recreational use of N2O, 158 (12%) used the substance recreationally, and 39 (3%) inhaled it at least monthly. Users were most likely to be white and to be men. Our results show a high frequency of recreational N2O use in first-year students at Auckland University. Although this study does not accurately reflect use of this substance in the wider community, the high prevalence suggests that presentations of subacute myelopathy in an otherwise fit young person should prompt an enquiry about use of N2O.
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Affiliation(s)
- Jennifer Ng
- Department of Neurology, Auckland Hospital, 1001, Auckland, New Zealand
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O'Grady G, Fitzjohn J. Debt on graduation, expected place of practice, and career aspirations of Auckland Medical School students. N Z Med J 2001; 114:468-70. [PMID: 11760241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
AIMS To determine the debt level that current Auckland medical students expect to graduate with, and evaluate this debt in the context of their career aspirations and intended place of practice. METHODS Simple check-box and fill-in-the-blank surveys were distributed to Auckland University medical students in Years 1 through to 5 during their second week of scheduled lectures in March 2000. Students were asked to provide demographic details, then complete sections on debt and career aspirations. RESULTS 70% of Auckland medical students participated. Average expected debt was between $60000 to $70000. Predicted size of graduation debt was significantly related with plans to practice medicine overseas, and this trend was especially strong among females. In addition, Maori and Polynesian students bear a disproportionate level of the student debt burden compared to Pakeha and Asian groups. 77% of students indicated a preference for working in private or hospital specialty work. CONCLUSIONS Student debt will have major effects on the composition of the New Zealand medical workforce over coming years. More attention must be paid to the national picture of medical student indebtedness if adequate workforce planning is to be possible.
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Affiliation(s)
- G O'Grady
- Faculty of Medicine and Health Sciences, University of Aukland.
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Abstract
Inferior turbinectomy, often combined with septal surgery, is frequently performed in the surgical treatment of nasal obstruction. A patient with post-operative greater palatine anaesthesia occurring after this procedure prompted a study of the anatomy of the greater palatine nerve in the region of the inferior turbinate. Sixty-four lateral nasal walls were examined in cadavers. A dehiscence rate of 22% was noted, and in an additional 55% there was only a minimal bony covering to the nerve. Dehiscences occurred exclusively in the inferior meatus, anterior to the posterior bony end of the inferior turbinate. The narrow antero-posterior extent of the dehiscence, the hard dense lateral nasal wall bone and the lateral position of the nerve in the canal help to protect the nerve from surgical trauma during turbinate surgery.
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Affiliation(s)
- J F Sharp
- Department of Otolaryngology, Queen Elizabeth Hospital, Birmingham, UK
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