PubMed Health⌕ Search

Biomedical subjects

D H Conway

Publications and source records attributed to D H Conway.

15 recordsLinked to original sources
PubMed2005

The effect of electromagnetic interference from mobile communication on the performance of intensive care ventilators.

UNLABELLED: Electromagnetic interference produced by wireless communication can affect medical devices and hospital policies exist to address this risk. During the transfer of ventilated patients, these policies may be compromised by essential communication between base and receiving hospitals. Local wireless networks (e.g. Bluetooth) may reduce the 'spaghetti syndrome' of wires and cables seen on intensive care units, but also generate electromagnetic interference. The aim of this study was to investigate these effects on displayed and actual ventilator performance. METHODS: Five ventilators were tested: Drager Oxylog 2000, BREAS LTV-1000, Respironics BiPAP VISION, Puritan Bennett 7200 and 840. Electromagnetic interference was generated by three devices: Simoco 8020 radio handset, Nokia 7210 and Nokia 6230 mobile phone, Nokia 6230 communicating via Bluetooth with a Palm Tungsten T Personal Digital Assistant. We followed the American National Standard Recommended Practice for On-Site, Ad Hoc Testing (ANSI C63) for electromagnetic interference. We used a ventilator tester, to simulate healthy adult lungs and measure ventilator performance. The communication device under test was moved in towards each ventilator from a distance of 1 m in six axes. Alarms or error codes on the ventilator were recorded, as was ventilator performance. RESULTS: All ventilators tested, except for the Respironics VISION, showed a display error when subjected to electromagnetic interference from the Nokia phones and Simoco radio. Ventilator performance was only affected by the radio which caused the Puritan Bennett 840 to stop functioning completely. The transfer ventilators' performance were not affected by radio or mobile phone, although the mobile phone did trigger a low-power alarm. Effects on intensive care ventilators included display reset, with the ventilator restoring normal display function within 2 s, and low-power/low-pressure alarms. Bluetooth transmission had no effect on the function of all the ventilators tested. CONCLUSION: In a clinical setting, high-power-output devices such as a two-way radio may cause significant interference in ventilator function. Medium-power-output devices such as mobile phones may cause minor alarm triggers. Low-power-output devices such as Bluetooth appear to cause no interference with ventilator function.

Cell Phone↗
PubMed2004

The effects of tracheostomy cuff deflation during continuous positive airway pressure.

Continuous flow positive pressure devices bridge the gap between mechanical and unsupported ventilation in patients recovering from critical illness. At this point, patients are often fully awake, yet the inflated tracheostomy cuff prevents them from speaking or swallowing. The aim of this study was to investigate the effects of cuff deflation. After ethics committee approval and informed consent, we recorded airway pressures with catheters placed 3 cm beyond the distal tracheostomy tip, respiratory rate, heart rate and peripheral oxygen saturation with continuous positive airway pressures set at 5, 7.5 and 10 cmH(2)O with the cuff inflated and deflated. Sixteen patients completed the study. There were small falls in end expiratory pressure on cuff deflation. The median (interquartile range) pressure drop with set airway pressure of 5 cmH(2)O was 0.25 (0-1.4) mmHg, which increased to 1 (0-3) mmHg at 7.5 cmH(2)O and 1.5 (0-4) mmHg at 10 cmH(2)O. These changes were not clinically significant and cardiopulmonary parameters remained stable. All patients were able to vocalise following cuff deflation. Twelve patients passed a blue dye swallow screen within a day of tolerating cuff deflation. These results suggest that pressures fall slightly following cuff deflation but this is associated with respiratory stability and may allow patients to talk and swallow.

Aged↗
PubMed2002

Target-controlled propofol requirements at induction of anaesthesia: effect of remifentanil and midazolam.

BACKGROUND AND OBJECTIVE: Target-controlled infusions of anaesthetic agents have become increasingly available. They can involve the use of propofol in combination with an opioid or a benzodiazepine. The effect site concentration of propofol infusions has been advocated as a method of estimating drug distribution. We investigated the influence of co-induction with remifentanil and midazolam on effect site propofol requirements at induction of anaesthesia using target-controlled infusions. METHODS: Sixty-six consenting adult patients were randomly allocated to three treatment groups. Each group received induction of anaesthesia with a different total intravenous technique. One group was induced with target-controlled propofol alone; another received target-controlled propofol and target-controlled remifentanil (3 ng mL-1); and the last received midazolam (0.03 mg kg-1), target-controlled remifentanil (3 ng mL-1) and target-controlled propofol. Computer simulation was used to calculate effect site concentrations. We recorded propofol dose and effect site concentration at loss of verbal response. RESULTS: The effect site concentration (Ce50) of propofol alone was 2.19 micrograms mL-1. This was reduced to 1.55 micrograms mL-1 during co-induction with remifentanil and further reduced to 0.64 microgram mL-1 with midazolam premedication (P < 0.001; ANOVA). CONCLUSIONS: We conclude that co-induction with remifentanil alone or with midazolam can be used to reduce propofol doses at induction of anaesthesia using target-controlled infusions. We believe that using effect site concentration may prove a useful tool in routine clinical practice.

Adult↗
PubMed2002

Randomised controlled trial investigating the influence of intravenous fluid titration using oesophageal Doppler monitoring during bowel surgery.

Oesophageal Doppler monitoring allows non-invasive estimation of stroke volume and cardiac output. We studied the impact of Doppler guided fluid optimisation on haemodynamic parameters, peri-operative morbidity and hospital stay in patients undergoing major bowel surgery. Fifty-seven patients were randomly assigned to Doppler (D) or control (C) groups. All patients received intra-operative fluid therapy at the discretion of the non-investigating anaesthetist. In addition, Group D were given fluid challenges (3 ml x kg(-1)) guided by oesophageal Doppler. Group D received significantly more intra-operative colloid than Group C (mean 28 (SD 16) vs. 19.4 (SD 14.7) ml x kg(-1), p = 0.02). Cardiac output increased significantly for Group D whilst that of controls remained unchanged. The mean difference between the groups in final cardiac output was 0.87 l x min(-1) (95% confidence interval 0.31-1.43 l x min(-1), p = 0.003). Five control patients required postoperative critical care admission. Fluid titration using oesophageal Doppler during bowel surgery can improve haemodynamic parameters and may reduce critical care admissions postoperatively.

Aged↗
PubMed2000

Truncus arteriosus and other lethal internal anomalies in Goltz syndrome.

An infant girl of 36 weeks gestational age was found to have cardiovascular and other lethal internal anomalies in addition to characteristic external abnormalities of focal dermal hypoplasia (Goltz syndrome). The internal anomalies included truncus arteriosus type II with truncal origin of hypoplastic pulmonary arteries, cardiac ventricular septal defect, severe hypoplasia of lungs and pulmonary veins, massive diaphragmatic hernia, and absence of the right kidney. Such a combination of severe anomalies has not been reported previously in Goltz syndrome.

Abnormalities, Multiple↗
PubMed1978

Hippocampal place units in the freely moving rat: why they fire where they fire.

Place units in the dorsal hippocampus of the freely-moving rat signal the animal's position in an environment (place field). In the present experiments, thirty four place units were recorded in two different environments: one, a small platform where the rat had received neither training nor reward; the other, an elevated T-maze inside a set of black curtains where the rat had been trained on a place discrimination. The places within the curtained enclosure were specified by four cues (a light, a card, a fan, and a buzzer) in addition to the food. Other cues were eliminated by rotating the maze and the four controlled cues relative to the external world from trial-to-trial. Some units had place fields in both environments while others only had a place field in one. No relationship could be seen between the place fields of units with fields in both environments. All twelve units tested extensively in the controlled enclosure had place fields related to the controlled cues. Probe experiments in which only some of the controlled cues were available showed that some of these units were being excited by one or two cues while others were influenced in a more complex way. The fields of these latter units were maintained by any two of the 4 cues and were due to inhibitory influences which suppressed the unit firing over the rest of the maze.

Acoustic Stimulation↗