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Biomedical subjects

R D Stewart

Publications and source records attributed to R D Stewart.

At least 19 recordsLinked to original sources
PubMed1991

An evaluation of cannulae and oxygen sources for pediatric jet ventilation.

The authors evaluated the cannulae and oxygen sources available for pediatric translaryngeal ventilation. Peak flow rates were measured and maximum tidal volumes (MTV) calculated for each combination of cannula and oxygen source. Standard 22, 20, 18, and 16 gauge intravenous catheters and a 14 gauge cannula designed for pediatric jet ventilation were tested. The oxygen sources evaluated included an adult bag-valve device; a continuous flow source regulated between 6 to 15 L/min; and a high pressure jet source regulated between 5 to 50 psi. Mean calculated MTV delivered to the cannula tip (22 g to 14 g) were: 26 to 235 mL with the bag-valve source; 91 to 236 mL with the continuous flow sources; and 58 to 1034 mL with the jet sources. Assuming that in normal subjects approximately 70% of the flow from the tip of a translaryngeal cannula reaches the distal respiratory tree, the authors conclude that bag-valve and continuous flow low pressure sources are unlikely to deliver sufficient tidal volumes to sustain normal ventilation in apneic children when coupled with standard cannulae. Jet oxygen sources with standard cannulae provide a wide range of tidal volumes sufficient to sustain normal ventilation in apneic pediatric patients.

Catheterization↗
PubMed1990

Nasotracheal intubation using a flexible lighted stylet.

Nasotracheal intubation is an essential skill for clinicians involved in the care of acutely ill or injured patients. Unfortunately, it has the dangers and difficulties of any blind technique. Although usually performed in the awake patient, nasotracheal intubation has also been used in the apneic patient. Transillumination of the soft tissues of the neck with a lighted stylet has been shown to be a reliable method of orotracheal intubation. The usefulness of a longer, flexible lighted stylet as an aid to nasotracheal intubation in the apneic patient has been examined. Eighty patients, who were paralyzed, apneic, and about to undergo nasotracheal intubation for elective ear, nose, and throat or maxillofacial surgery were randomized to be nasotracheally intubated blindly or with a stylet by an emergency medicine resident or anesthesiologist. Sixty-three percent intubated in the lighted-stylet group and 41% in the blind nasotracheal intubation group were successfully intubated. There were no significant differences in the time needed to intubate or the number of attempts. There were notable differences in the success rates of individual intubators with each technique. Although not statistically significant, our results suggest a useful role for the lighted stylet in nasotracheal intubation in the apneic patient.

Adolescent↗
PubMed1990

Manual translaryngeal jet ventilation and the risk of aspiration in a canine model.

STUDY OBJECTIVES: Manual translaryngeal jet ventilation (TLJV) is a safe and effective method of maintaining normal ventilation in apneic subjects. Little data exist on the amount of airway protection afforded with this technique of airway management. We sought to evaluate the risk of aspiration during manual TLJV. SETTING: Data were collected in a laboratory animal model. DESIGN: A prospective, nonrandomized, controlled trial was performed. PARTICIPANTS: Seventeen adult apneic mongrel dogs were enrolled. INTERVENTIONS: Intratracheal Gastrograffin was instilled and radiographic changes assessed during ventilation using a 0 to 3 scale (none to severe). Thirty-six trials were performed, with equal numbers at both 30 degrees and 45 degrees head elevation. The three groups studied were animals without airway protection (control), animals with a cuffed endotracheal tube (tube), and animals with a percutaneous TLJV cannula and a 50-psi oxygen source ventilated at a rate of 20 breaths per minute (jet). MEASUREMENTS AND MAIN RESULTS: Significantly less radiographic evidence of aspiration was noted in the jet and tube groups at 30 degrees and 45 degrees compared with control animals (P = .002 each). At 45 degrees head elevation a trend toward increased aspiration scores in the jet group compared with the tube group (P = .065) was observed. CONCLUSION: In our model, manual TLJV at 20 breaths per minute and an I:E ratio of 1:2 provided protection from aspiration comparable to that observed with a cuffed endotracheal tube at 30 degrees head elevation. At 45 degrees elevation, this protection was diminished.

Animals↗
PubMed1990

Correct positioning of an endotracheal tube using a flexible lighted stylet.

Endotracheal intubation is not without complications, among the most serious of these being misplacement of the endotracheal (ET) tube. Unrecognized esophageal placement is a lethal complication, but even when placed in the trachea, ET tubes can be displaced distally and enter a mainstem bronchus. Correct positioning of an ET tube is usually defined as the placement of the tube within the trachea approximately 5 cm above the carina. Chest x-ray is the most common and a reliable method of demonstrating correct positioning, particularly in ICU patients. Using transillumination by means of a flexible stylet (lightwand), we investigated whether transillumination could position an ET tube consistently within 5 +/- 2 cm of the carina. Ten human cadavers of varied weight and body habitus were intubated under direct vision and 10 ml of a radiopaque dye was injected down the tube as a marker for the carina. A premeasured flexible lighted stylet was then inserted into the inplace tube so that the bulb was positioned at the tube's distal opening. The brightest transilluminated glow produced by the bulb was then positioned at the sternal notch. A chest x-ray was taken and the distance of the tube tip from the carina was calculated. In each case the tube tip could be placed consistently at a level 5 +/- 1 cm from the carina by observing the maximal transilluminated glow at the sternal notch. We conclude that transillumination of the neck using a flexible lighted stylet can accurately and consistently position an ET tube at an appropriate distance above the carina.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1990

Facilities and regionalization--emergency medical services systems.

Advanced life support and the modern EMS system were born out of the hope that by extending hospital emergency facilities outside the bounds of the hospital, earlier and more intensive care could be provided to those patients requiring it. EMS systems have since left the nest and only recently, following a turbulent adolescence, is prehospital care returning as a partner with the medical facilities and physicians that presided over their modern origins. The next decade will see the continuing trend toward hospitals and practitioners regaining some influence in the design and direction of prehospital care.

Emergency Medical Services↗
PubMed1989

Advances in prehospital immediate care.

Although studies documenting the influence of prehospital care on patient outcome are most urgently needed, recent techniques and innovations being examined in the field setting may improve the clinical care delivered. The basic manoeuvres for airway and breathing have been in need of emphasis for some time. Sellick's manoeuvre has been resuscitated and is being emphasized in most training programmes. Bag-mask ventilation, notoriously difficult in field settings in the hands of emergency medical personnel, has been improved with the recent improvement of mask design. Endotracheal intubation has been shown to influence patient outcome, and can be performed with surprising success by paramedics. Complication rates continue to cause concern, and a study to document the incidence of tube misplacement has just begun in the United States and Canada. Transillumination and translaryngeal jet ventilation have been refined as adjunct techniques to field intubation. Patient monitoring has improved through the more common use of pulse oximetry and a recently-introduced "CO2 Detector" that is designed to indicate via a colour change, oesophageal placement of an endotracheal tube. Automatic external defibrillators have come under some scrutiny, and early data suggest their safe use by lay persons, a minimal effect on outcome in high-risk patients, and a significant effect on outcome only when combined with other essential elements of prehospital care. The role of IV fluids in prehospital trauma care has been clarified, as well as that of the pneumatic antishock garment. Transcutaneous pacemakers have been developed and shown effective if used early, and thrombolytic therapy has been examined for the prehospital management of acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency Medical Services↗
PubMed1989

Pulse oximetry in the emergency department.

Three cases representing the emergency department use of pulse oximetry are described. A brief review of the principles of operation of pulse oximetry, as well as a discussion of recent literature and clinical uses of the technology, is presented. While not replacing arterial blood gases in the assessment of critically ill patients, a more widespread use of pulse oximetry in evaluating emergency department patients might provide significant information in the management of patients with respiratory complaints. Pulse oximetry may also play an important role in monitoring those patients requiring airway interventions such as assisted ventilation or endotracheal intubation.

Adolescent↗
PubMed1989

Emergency department telephone advice.

Emergency department personnel are frequently asked to give advice to members of the community who telephone for advice or information about a wide variety of medical problems. A study was designed to determine the consistency and accuracy of directions given to adults who call EDs seeking advice about a problem. Forty-six EDs were selected and telephoned for advice by a research assistant who presented a scenario that could have reasonably been interpreted as a patient experiencing myocardial ischemia. Nine percent of the calls were answered and managed only by ED unit secretaries. Fifty-six percent of the respondents failed to ask the caller any questions about the patient or the chief complaint. Only four ED respondents instructed the caller to call 911 and have the patient brought to the ED. The data suggest that telephone advice given by some EDs is nonstandardized and may be inadequate to the point of jeopardizing the welfare of the caller.

Adult↗
PubMed1989

Manual translaryngeal jet ventilation.

The manual translaryngeal jet technique is a safe and reliable method of emergency ventilation, providing adequate gas exchange and high levels of oxygenation for the patient who requires positive pressure breathing. It can be performed more rapidly than other invasive means of airway control and, with close attention to the proper technique, has proved safe and effective in maintaining normal blood gases for prolonged periods. Further work is required to define proper inspiratory-to-expiratory ratios better and to determine whether the technique is protective against aspiration. The equipment and technique should be familiar and readily available to every emergency clinician.

Emergencies↗
PubMed1988

Abdominal aortic aneurysm.

Between 1981 and 1986, 282 cases of abdominal aortic aneurysm were diagnosed in Waltham Forest. Rupture had occurred in 183, 15 underwent urgent operation for intact aneurysm, and 84 had elective surgery. The incidence of rupture increased from 13 to 21 per 100,000 population during the 6-year period. Operative mortality for patients with rupture was 54.7 per cent, but the mortality overall was 81.4 per cent. In 59 per cent of patients with rupture no operation was performed, and 35.0 per cent of all deaths occurred in the community. The mortality for rupture in women was significantly higher than in men, although the operative mortality was comparable. Fifty patients (27 per cent) were found to have attended hospital within 2 years of rupture and many had documented evidence of an aneurysm. One-third of all patients admitted with rupture were undiagnosed. This study complements the previous small number of community studies and suggests that the incidence of rupture is increasing nationally particularly in women, where the mortality was exceptionally high. Early elective surgery is the key to the problem and improved clinical awareness could save many patients without elaborate and expensive programmes to screen the 'at risk' population.

Age Factors↗
PubMed1988

Oxygen enrichment of bag-valve-mask units during positive-pressure ventilation: a comparison of various techniques.

Bag-mask devices are used frequently to provide patients with positive-pressure-assisted ventilation. To increase the percentage of oxygen delivered (FDO2) from the bag, supplemental oxygen must be provided by way of an oxygen inlet nipple attached to the unit. Using ten medical volunteers and a test lung with oxygen analyzer, we studied the effect of several variables on the FDO2 and determined the most effective reservoir that would provide the highest consistent FDO2 from the ventilating port of the bag. An FDO2 of 1.00 was consistently provided by the 2.5-L bag reservoir and a demand-valve set-up attached to the reservoir port of the ventilating bag. Bag refill time significantly affected the FDO2 when no reservoir or corrugated tube reservoirs were used. Corrugated tube reservoirs were found to be more sensitive to all variations in ventilatory technique and to oxygen flow rates. From our findings we recommend that corrugated tube reservoirs not be used for oxygen supplementation, as they are sensitive to variations in ventilatory technique and cannot alert clinicians to problems with oxygen flow. While both the 2.5-L bag reservoir and demand-valve provide a consistent FDO2 of 1.00, the demand valve has the advantage of audible filling of the ventilating bag as well as being compact and independent of ventilatory technique.

Equipment Design↗