Robot-assisted airway support: a simulated case.

Recent advances in telemedicine and robotically assisted telesurgery may offer advanced surgical care for the geographically remote patient. Similar advances in tele-anesthesia will be necessary to optimize perioperative care for these patients. Although many preliminary investigations into tele-anesthesia are underway, none involves remote performance of anesthesia-related procedures. Here we describe simulated robotically assisted fiberoptic intubations using an airway simulation mannequin. Both oral and nasal approaches to fiberoptic intubation were successful, but presented unique opportunities and challenges inherent to the robot's design. Robotically assisted airway management is feasible using multipurpose surgical robotic systems.

Synchronization of radiograph film exposure with the inspiratory pause. Effect on the appearance of bedside chest radiographs in mechanically ventilated patients.

The appearance of portable chest radiographs (CXRs) may be affected by changes in ventilation, particularly when patients are mechanically ventilated. Synchronization of the CXR with the ventilatory cycle should limit the influence of respiratory variation on the appearance of the CXR. This study evaluates the effect of synchronizing the CXR film exposure with ventilation on the appearance of the radiograph. Twenty-five patients who remained intubated postoperatively, were mechanically ventilated, and required a CXR were enrolled in this triple-blind, randomized prospective study. Each patient received one radiograph using conventional techniques and another using the interface. The sequence of the two films was randomized, and the two films were taken on the same patient within a few minutes of each other. Hence, each patient served as his own control and the position of the patient, source-film distance, intensity (Kvp), and duration of the exposure (mAs) were identical for the two films. Five board-certified radiologists were then asked to compare paired films for clarity of lines and tubes, definition of the pulmonary vasculature, visibility of the mediastinum, definition of the diaphragm, and degree of lung inflation. Radiologists were also asked to choose which films they preferred. A majority of board certified radiologists preferred CXRs taken with the interface in 21 of 25 patients (p < 0.0001). Furthermore, four of the five criteria evaluated were improved (p < 0.05) on synchronized CXRs. Synchronization of the bedside CXR with the end of inspiration ensures that they are always obtained at maximal inflation, which improves the appearance of a majority of radiographs by at least one of five criteria.

Clinical assessment of a plastic optical fiber stylet for human tracheal intubation.

BACKGROUND: The authors compared the performance of a prototype intubation aid that incorporated plastic illumination and image guides into a stylet with fiberoptic bronchoscopy and direct laryngoscopy for tracheal intubation by novice users. METHODS: In a randomized, nonblinded design, patients were assigned to direct laryngoscopy, fiberoptic bronchoscopy, or imaging stylet intubation groups. The quality of laryngeal view and ease with which it was attained for each intubation was graded by the laryngoscopist. Time to intubation was measured in 1-min increments. A sore-throat severity grade was obtained after operation. RESULTS: There were no differences in demographic, physical examination, or surgical course characteristics among the groups. The laryngoscope produced an adequate laryngeal view more easily than did the imaging stylet or bronchoscope (P = 0.001) but caused the highest incidence of postoperative sore throat (P<0.05). Although the time to intubation for direct laryngoscopy was shorter than for imaging stylet, which was shorter than fiberoptic bronchoscopy (P<0.05), the quality of laryngeal view with the imaging stylet was inferior to both direct laryngoscopy and fiberoptic bronchoscopy techniques (P<0.05). CONCLUSIONS: Novices using the imaging stylet produce fewer cases of sore throat (compared with direct laryngoscopy) and can intubate faster than when using a bronchoscope in anesthetized adult patients. The imaging stylet may be a useful aid for tracheal intubation, especially for those unable to maintain skills with a bronchoscope.

Autoregulation in a simulator-based educational model of intracranial physiology.

OBJECTIVE: To implement a realistic autoregulation mechanism to enhance an existing educational brain model that displays in real-time the cerebral metabolic rate (CMRO2), cerebral blood flow (CBF), cerebral blood volume (CBV), intracranial pressure (ICP), and cerebral perfusion pressure (CPP). METHODS: A dynamic cerebrovascular resistance (CVR) feedback loop adjusts automatically to maintain CBF within a range of the CPP and defines autoregulation. The model obtains physiologic parameters from a full-scale patient simulator. We assumed that oxygen demand and arterial partial pressure of carbon dioxide (CO2 responsivity) are the two major factors involved in determining CBF. In addition, our brain model increases oxygen extraction up to 70% once CBF becomes insufficient to support CMRO2. The model was validated against data from the literature. RESULTS: The model's response varied less than 9% from the literature data. Similarly, based on correlation coefficients between the brain model and experimental data, a good fit was obtained for curves describing the relationship between CBF and PaCO2 at a mean arterial blood pressure of 150 mm Hg (R2 = 0.92) and 100 mm Hg (R2 = 0.70). DISCUSSION: The autoregulated brain model, with incorporated CO2 responsivity and a variable oxygen extraction, automatically produces changes in CVR, CBF, CBV, and ICP consistent with literature reports, when run concurrently with a METI full-scale patient simulator (Medical Education Technologies, Inc., Sarasota, Florida). Once the model is enhanced to include herniation, vasospasm, and drug effects, its utility will be expanded beyond demonstrating only basic neuroanesthesia concepts.

Performance of a plastic optical fiber stylet for tracheal intubation of a dog.

OBJECTIVE: We set out to establish whether a novel plastic optical fiber incorporated into an endotracheal tube (ETT) stylet could be used for intubation of a dog. A secondary objective examined the need for a direct illumination source from a laryngoscope. Lastly, the fragility of the system was tested. METHODS: An anesthetized dog was repeatedly intubated using a laryngoscope to elevate the tongue and the view of the larynx conducted through the plastic optical fiber stylet (placed within an endotracheal tube) and displayed on a television monitor. Four prototype identical stylets were tested. Repeated intubations were attempted with each stylet and graded as either successful or failed. All four stylets were tested 10 times each using a Miller 4 blade and direct illumination from the laryngoscope. Two of the four stylets were reused during an additional 10 intubation attempts using a Miller 4 blade and laryngoscope (without batteries) with only ambient light. Finally, one stylet was used for intubation after 10, 20, 30, 40 and 50 sharp 90 degree bend-and-straighten cycles using a Miller 4 blade and laryngoscope for direct illumination. RESULTS: All attempted intubations were successful. However, the image quality was dramatically better when direct illumination from a laryngoscope was used than when ambient light was used. One plastic optical fiber stylet was successfully used to intubate after having been used for 20 intubations and 50 sharp 90 degree bend-and-straighten cycles. A partial lens separation occurred between the 41st and 50th bend cycle but the image remained adequate enough to successfully intubate again. CONCLUSIONS: A novel plastic optical fiber incorporated into an ETT stylet can be used with a laryngoscope for intubation of a dog. Direct illumination from a laryngoscope provides a better television monitor image than when only ambient light is used. The system was durable, withstanding over 20 uses and 40 sharp bend-and-straighten cycles before a lens separation failure occurred.

TWITCHER: a device to stimulate thumb twitch response to ulnar nerve stimulation.

OBJECTIVE: To design and fabricate a device to simulate evoked thumb adduction in response to ulnar nerve stimulation. METHODS: We implemented a computer-controlled, motorized thumb (TWITCHER) that responds to ulnar nerve stimulation by an unmodified peripheral nerve stimulator. Clinically realistic response patterns are generated for both depolarizing and non-depolarizing muscle relaxants and three modes of stimulation (single twitch, train-of-four, tetanus). RESULTS: The device has been used in a full-scale patient simulator for the last six years. DISCUSSION: TWITCHER has been well received by participants in simulation exercises including the use of neuromuscular blocking drugs.

A computer model of intracranial dynamics integrated to a full-scale patient simulator.

The ability to visualize intracranial dynamics during simulated clinical scenarios is a valuable tool for teaching brain physiology and the consequences of different medical interventions on the brain. Studies have isolated physiologic variables and shown their effects on brain dynamics. However, no studies have shown the combined effects of these variables on intracranial dynamics. This brain model offers one approach that brings all these relationships together and shows how they affect the dynamics of the brain. The brain model obtains its physiologic inputs from a full-scale patient simulator which responds to clinical interventions. This integration allows individuals working on the patient simulator to see the effects of their actions on brain dynamics. The brain model gives a real-time display of intracranial events (cerebral metabolic rate, cerebral blood flow, cerebral blood volume, cerebral perfusion pressure, and intracranial pressure) and responds to changes in the pulmonary and cardiovascular condition of the patient simulator.

Influence of pulse oximetry and capnography on time to diagnosis of critical incidents in anesthesia: a pilot study using a full-scale patient simulator.

OBJECTIVE: Many studies (outcome, epidemiological) have tested the hypothesis that pulse oximetry and capnography affect the outcome of anesthetic care. Uncontrollable variables in clinical studies make it difficult to generate statistically conclusive data. In the present study, we eliminated the variability among patients and operative procedures by using a full-scale patient simulator. We tested the hypothesis that pulse oximetry and capnography shorten the time to diagnosis of critical incidents. METHODS: A simulator was programmed to represent a patient undergoing medullary nailing of a fractured femur under general anesthesia and suffering either malignant hyperthermia, a pneumothorax, a pulmonary embolism or an anoxic oxygen supply. One hundred thirteen anesthesiologists were randomly assigned to one of two groups of equal size, one with access to pulse oximetry and capnography data and the other without. Each anesthesiologist was further randomized to one of the four critical incidents. Each anesthetic procedure was videotaped. The time to correct diagnosis was measured and analyzed. RESULTS: Based on analysis of 91 of the subjects, time to diagnosis was significantly shorter (median of 432 s vs. >480 s) for the anoxic oxygen supply scenario (p = 0.019) with pulse oximetry and capnography than without. No statistical difference in time to diagnosis was obtained between groups for the other three critical incidents. CONCLUSIONS: Simulation may offer new approaches to the study of monitoring technology. However, the limitations of current simulators and the resources required to perform simulator-based research are impediments to wide-spread use of this tool.

Logistics of conducting a large number of individual sessions with a full-scale patient simulator at a scientific meeting.

OBJECTIVE: To design and implement the logistics of accommodating a large number of participants in individual, hands-on sessions on a full-scale patient simulator during a major scientific meeting or continuing medical education course. METHODS: We used our method during the 11th World Congress of Anaesthesiologists in Sydney, Australia to facilitate studying the impact of pulse oximetry and capnography on the time taken by anesthesiologists to correctly identify critical incidents on a full-scale patient simulator. Each study participant spent 15 minutes in 4 sections of the study area: the anesthesia and monitoring equipment briefing room, the simulator briefing room, the simulation room and the debriefing room. RESULTS: There were 113 participants during five days (15 during instructor training and 25, 23, 24 and 26 on subsequent exhibit days). We were oversubscribed daily. However, there were 9 no-shows during the 4 days of the study, which generated a participant absence rate of 9.2%. The average number of participants over the 4 days of the study was 24.5 per day compared to our capacity of 27 per day. The feedback we obtained from the participants about the simulation experience and the format of the exercise was positive and enthusiastic. CONCLUSIONS: We have developed a practical and viable method that can be adapted for use at scientific meetings and courses, which improves accessibility of individual, hands-on sessions on full-scale patient simulators to a larger audience than previously attainable. Our method is applicable for continuing medical education courses as well as research purposes in the form of prospective studies during scientific meetings and courses.

Magnetron-based inline microwave fluid warmer.

OBJECTIVE: To develop an in-line microwave fluid warming system that eliminates the difficulties of uneven heating that are characteristic of batch-mode microwave fluid warmers. METHODS: Using a commercial microwave oven, we developed a method for warming fluid as it flowed through tubing along a defined path in the oven's cavity. Algorithms utilizing either proportional or adaptive control were used to control microwave heating cycles by varying the heating pulse-width during 3-second epochs. Methods of fluid entry and exit were devised to minimize microwave leakage. Heating performance was tested using icewater at multiple flow rates from 18 mL/min to 105 mL/min. RESULTS: In all warming tests, the system achieved temperature control without exceeding the maximum temperature allowable based on American Association of Blood Banks requirements. The adaptive control maintained the set temperature, with peak-to-peak oscillations of 2 degrees C or less. Microwave leakage was below the commercially required limit for home microwave appliances. CONCLUSIONS: The combination of proportional and adaptive control is successful in controlling the permanent magnet magnetron microwave energy to heat the icewater tested. The in-line microwave warmer has the potential to become a successful medical fluid warmer. More study is needed to determine the stability of the control system under clinical conditions, and to evaluate its utility for warming blood.

[Anesthesia simulators and training devices]. / Anästhesiesimulatoren und Trainingsgeräte.

Simulators and training devices are used extensively by educators in 'high-tech' occupations, especially those requiring an understanding of complex systems and co-ordinated psychomotor skills. Because of advances in computer technology, anaesthetised patients can now be realistically simulated. This paper describes several training devices and a simulator currently being employed in the training of anaesthesia personnel at the University of Florida. This Gainesville Anesthesia Simulator (GAS) comprises a patient mannequin, anaesthesia gas machine, and a full set of normally operating monitoring instruments. The patient can spontaneously breathe, has audible heart and breath sounds, and palpable pulses. The mannequin contains a sophisticated lung model that consumes and eliminates gas according to physiological principles. Interconnected computers controlling the physical signs of the mannequin enable the presentation of a multitude of clinical signs. In addition, the anaesthesia machine, which is functionally intact, has hidden fault activators to challenge the user to correct equipment malfunctions. Concealed sensors monitor the users' actions and responses. A robust data acquisition and control system and a user-friendly scripting language for programming simulation scenarios are key features of GAS and make this system applicable for the training of both the beginning resident and the experienced practitioner. GAS enhances clinical education in anaesthesia by providing a non-threatening environment that fosters learning by doing. Exercises with the simulator are supported by sessions on a number of training devices. These present theoretical and practical interactive courses on the anaesthesia machine and on monitors. An extensive system, for example, introduces the student to the physics and clinical application of transoesophageal echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Simulation of ventilatory-induced stone movement and its effect on stone fracture during extracorporeal shock wave lithotripsy.

Because ventilation influences renal movement, we investigated the effect of stone motion on the efficiency of extracorporeal shock-wave lithotripsy (ESWL). Comparisons of the rates of fragmentation of an experimental model of renal calculi were made between simulated high-frequency jet ventilation at 100 breaths/min. with four-mm. stone movement as measured from the fluoroscope screen, conventional mechanical ventilation at 10 breaths/min. with 32-mm. stone movement as measured from the fluoroscope screen, and a static control. Fragmentation did not differ significantly between high-frequency jet ventilation and no ventilation (static control), but was significantly greater with high-frequency jet ventilation than with conventional ventilation.

Effects of expiratory flow resistance on inspiratory work of breathing.

To minimize work of breathing, airway pressure should not fluctuate during spontaneous breathing with continuous positive airway pressure (CPAP). However, flow resistance in the inspiratory limb of the breathing circuit and an inadequate continuous gas flow rate result in airway pressure fluctuation and increased work of breathing. Flow resistance of the expiratory pressure/exhalation valve also directly affects the level of airway pressure during spontaneous inhalation with CPAP (the greater the resistance of the valve, the greater the decrease in airway pressure and work of breathing). We compared this effect with three types of expiratory pressure valves: a threshold resistor with low resistance to flow, an inflatable balloon (mushroom) valve with moderate resistance to flow, and a variable-orifice flow resistor with a high resistance to flow. Work increased up to threefold with the balloon valve and more than tenfold with the flow resistor compared with the threshold resistor. To apply CPAP, expiratory pressure valves with low resistance to flow should be used to minimize fluctuations in airway pressure and, thus, in the work of spontaneous breathing.