Marc Borne

Auscultation in Flight: Comparison of Conventional and Electronic Stethoscopes

OBJECTIVESnThe ability to auscultate during air medical transport is compromised by high ambient-noise levels. The aim of this study was to assess the capabilities of a traditional and an electronic stethoscope (which is expected to amplify sounds and reduce ambient noise) to assess heart and breath sounds during medical transport in a Boeing C135.nnnMETHODSnWe tested one model of a traditional stethoscope (3MTM Littmann Cardiology IIITM) and one model of an electronic stethoscope (3MTM Littmann Stethoscope Model 3000). We studied heart and lung auscultation during real medical evacuations aboard a medically configured C135. For each device, the quality of auscultation was described using a visual rating scale (ranging from 0 to 100 mm, 0 corresponding to I hear nothing, 100 to I hear perfectly). Comparisons were accomplished using a t-test for paired values.nnnRESULTSnA total of 36 comparative evaluations were performed. For cardiac auscultation, the value of the visual rating scale was 53 ± 24 and 85 ± 11 mm, respectively, for the traditional and electronic stethoscope (paired t-test: P = .0024). For lung sounds, quality of auscultation was estimated at 27 ± 17 mm for traditional stethoscope and 68 ± 13 for electronic stethoscope (paired t-test: P = .0003). The electronic stethoscope was considered to be better than the standard model for hearing heart and lung sounds.nnnCONCLUSIONnFlight practitioners involved in air medical evacuation in the C135 aircraft are better able to practice auscultation with this electronic stethoscope than with a traditional one.

Acute Respiratory Distress Syndrome: Performance of Ventilator at Simulated Altitude

BACKGROUNDnVentilation of Acute Respiratory Distress Syndrome (ARDS) is a challenge, and there is definitely a need for lack of variations between delivered and set tidal volume (Vt). We have assessed the ability of the ventilator T-birdVS02 and LTV-1000 to deliver to a lung model with ARDS a set Vt at different simulated altitudes.nnnMETHODSnWe used a decompression chamber to mimic the hypobaric environment at a range of simulated cabin altitudes of 1,500, 2,500, and 3,000 m (4,000, 6,670, and 8,000 feet, respectively). Ventilators were tested with realistic parameters. Vt was set at 400 mL and 250 mL in an ARDS lung model. Comparisons of preset to actual measured values were accomplished using a t test for each altitude.nnnRESULTSnThe T-birdVS02 showed a decrease in the volume delivered. Comparisons of actual delivered Vt and set Vt demonstrated a significant difference starting at 1,500 m for a Vt set of 400 mL and at 2,500 m for Vt set of 250 mL. At these altitudes, the variations between Vt set and delivered were more than 10%. With decreasing barometric pressure, the LTV-1000 showed mostly an increase in volume delivered. Comparisons of actual delivered Vt and set Vt demonstrated a significant difference at 2,500 m for a Vt set of 400 mL and at 3,000 m for Vt set of 250 mL. The delivered Vt remained within 10% of the set Vt.nnnCONCLUSIONnClinicians involved in aerial evacuations must keep in mind the performance and limitations of their ventilator system.

Focused assessment with sonography in trauma as a triage tool

We congratulate Xiang et al [1] for their study describing triage strategies adopted during the postearthquake period with numerous pediatric casualties. We want to highlight the role of the focused assessment with sonography in trauma (FAST). It offers a reliable tool not only for trauma treatment but also during triage that can be used successfully as a screening tool specifically in children. Focused assessment with sonography in trauma has now become an extension of the physical examination and helps detect lifethreatening injuries within the “golden hour” and allows appropriate triage of the patients [2,3]. Many surgeons now consider it as a standard part of the pediatric trauma evaluation during disaster. In 1997, an international consensus conference committee defined the acronym FAST to describe the application of ultrasound in the initial evaluation of trauma patients [3]. The development of handheld ultrasound devices facilitated the introduction of FAST into prehospital trauma management and caused significant changes in the triage of multiple injured patients. The use of ultrasound has focused on the FAST examination as a major adjunct to triage and management of illness as well as patient assessment. There are several factors that should be considered when using FAST. It should be used as an initial screening method to identify patients at risk. It does not provide a definitive diagnosis. Time should not be wasted in trying to identify organ lesions. Adequate training and experience are crucial for accurate ultrasound examination, as the quality of the evaluation is highly user dependent and must not delay patient management. Emergency bedside sonography for victims of blunt abdominal trauma was one of the first applications for ultrasound. In assessing the need for laparotomy in children, FAST scan alone has a sensitivity of 70% and specificity of 100%; but when combined with physical examination, the sensitivity rose to 100% [4]. Ultrasound examination has been useful in the diagnosis of shock for assessing cardiac function, for detecting increased intracranial pressure by measuring the optic nerve sheath diameter, for identifying abscess (or foreign body), and for safe incision and drainage. The predominance of orthopedic trauma is described in the postearthquake period. Hubner et al [5] reported a sensitivity of 91% in the diagnosis of skeletal fractures with ultrasound. Based on their exceptional experience, we would like to know the authors thoughts concerning the role of FAST in triage strategies.

Performance of ventilators at simulated altitude: study of fraction of inspired oxygen

We studied the performance of two respirators employing an advanced turbine delivery system: LTV 1000, Tbird VSO2. We assessed the ability of the ventilators to deliver to a normal lung model a set fraction of inspired oxygen (FiO2) at different simulated cabin altitudes.

Altitude Testing of Medical Equipment: Advocacy for a Standardized Process

Air Medical Journal 29:3 Dear Editors: To improve the prognosis of patients with critical conditions, the air medical evacuation system is expected to move patients faster and farther than in previous years. Modern technology allows for the establishment of a seamless en route care capability for ill patients as they move through the evacuation system. Air medical evacuation requires highly advanced medical equipment that needs to be tested in real-life scenarios. It is easier to find ground tests of various equipment for comparison, but tests made in altitude or simulated altitude are unusual. Because of barometric pressure changes during air medical evacuation, specific alterations require oriented experimentations. That kind of experimentation, in flight or in a hypobaric chamber, is difficult and costly. Unfortunately, benchmarking by crossing the results of studies on the same topic is often impossible because of the lack of standardized test procedures. The need exists for an international consensus test of medical equipment involved in air evacuation, at a minimum on the frequently used altitudes. Take ventilators as an example. Numerous evaluations of ground transport ventilators have been made, including up to 15 ventilators.1 Ventilatory support is an important topic in air transport. Mechanical ventilation is often used in the air evacuation of patients in critical condition. Decreasing barometric pressure can affect the tidal volume delivered. Physicians in charge of air evacuation should pay attention to this crucial point. Only a few studies could be found. A literature search of Medline in August 2009 using the MeSH database items “Altitude” and “Ventilator” revealed only two studies concerning performance of modern ventilators in a hypobaric environment.2,3 Flynn and Singh2 studied the Oxylog 1000, 2000, and 3000 ( Dräger Medical, Lübeck, Germany). They used lung models for normal lung condition, asthma, and acute respiratory distress syndrome. Simulated altitudes were 1,800 and 3,400 meters. Rodriquez et al3 accessed performance of the LTV-1000 (Pulmonetic Systems Inc., West Caldwell, NJ) and Eagle 754 (Impact Instrumentation Inc, West Caldwell, NJ). Based on a normal lung model conditions, a decompression chamber was used to mimic the hypobaric environment at the following altitudes: 1,500, 3,000, and 5,600 meters. These examples regarding ventilators show that a lack of standardized test procedures makes benchmarking impossible. One could assume that common points can be found about testing processes for medical equipment. Concerning the studied altitudes, the international rules can serve as a basis. The aircraft cabin altitude during an air medical evacuation is less than 2,500 m (International Civil Aviation Organization), which is practically the condition of most commercial flights: 1,500 m. In some military flights, the cabin altitude is approximately 3,000 m. These three hypobaric conditions (1,500, 2,500, and 3,000 meters) should be commonly used in the next studies of medical equipment in altitude for standardization purposes. Concomitant to the development of such experimentation is the need for an international consensus to make benchmarking possible. As a result of reliable and consistent data from standardized test procedures, researchers and physicians can stay focused on the equipment considerations and potential problems unique to air transport.