Tactical Emergency Medicine: Emerging Technologies for the Tactical Medical Provider

Stephen Brock Blankenship

Mark E. Gebhart

Jason R. Pickett

OBJECTIVES

After reading this section, the reader will be able to:

Be familiar with recent technological advances that impact medicine in the tactical environment at the provider level.
Understand the role that these technologies may play in their particular system.
Understand the limitations of many of these technologies.
Balance the benefits of new technologies with the cost, probably impact, and drawbacks of technologies for use in tactical medicine.
Be aware of emerging advances that may play a future role in tactical emergency care.

Tactical emergency care is often viewed as an extension of basic trauma skills in the field of care in potentially hostile environments. Those who view tactical medicine this way may feel that bandages and intravenous fluid are the limits of needed medical skills and attention. Recent advances in technology clearly have helped decrease morbidity and mortality in today’s operational environment. To be of great use, new technologies must meet the demands of the tactical environment and the care providers of varying skill levels who may be called on to use them. As a general rule, tools for tactical use must meet some of the requirements summarized in Table 35.1.

ADVANCES IN PATIENT ASSESSMENT

Amplified Stethoscopes

Though the stethoscope has been a tool of the medical provider since the 1800s, the biggest advance in this technology has come only recently, with the addition of electronic noise amplification. Some models have the ability to dampen ambient noise, to allow the listener to better hear desired lung sounds and heart sounds. The technology here operates on skills already possessed by medical providers at virtually every level. The key advantages posed by these scopes are the ability to improve transmission of important sounds while excluding others in the potentially noisy and hectic tactical environment. This becomes especially important considering that the medic may have been exposed to live gunfire and so may have a decreased ability to hear. Features such as the ability to record and play back sounds are probably of little utility to the tactical provider.

Ultrasound

Ultrasound is quickly becoming a standard of patient assessment in the emergency departments of the nation’s hospitals. With the advent of battery-powered portable ultrasound units, this technology is now available to the field provider. Though its uses vary and are continually expanding, ultrasound for the tactical provider will likely be of greatest benefit for two principal functions: assessment of intraperitoneal blood and guidance for placement of central venous catheters. It has been used with some success in military deployments to Iraq (1) as well as onboard the International Space Station (2).

Assessment of intraperitoneal/pericardial blood. The Focused Assessment by Sonogram for Trauma, or FAST,
exam has become a standard at many trauma centers nationwide. By using ultrasound to examine four areas, or “windows,” the provider can assess the presence of significant intraperitoneal or pericardial blood requiring surgery in about 30 seconds, with a sensitivity of 77% to 81% and a specificity of 98% to 99% (3,4). A nonphysician provider, unfamiliar with the procedure, was able to perform the procedure with real-time online help from remote physicians in about 5 minutes (2).

TABLE 35.1. Requirements for Technology in the Tactical Setting.

Ruggedness. The adage, “If you take care of your gear, it will take care of you,” is nowhere more appropriate than in the tactical setting. The tactical environment is notoriously hard on equipment. Proper care of any equipment is important, but this care cannot be a limitation to the operational effectiveness of the user.

Portability. Tactical care providers must often carry their medical equipment on their person, sometimes over great distances. Any equipment used for this purpose must be both lightweight and compact, or the user is likely to leave the equipment behind.

Ease of use. Tactical emergency care providers vary greatly in level of medical training. Technologies appropriate for the physician provider may not prove appropriate for the basic EMT or field medic. Any technology employed in the field must be applicable to the individual provider’s level of training.

Speed of deployment. Tactical field care is performed expediently, often for reasons of personal safety or mission effectiveness. Any technology used for care in the field cannot be burdensome as far as the amount of time necessary to set it up and employ it.

Reliability. Any technology used in the field environment must be reliable, even under less-than-ideal conditions. If a device cannot be relied on to function at all times, it might as well be left behind.

Multipurpose use. The more purposes a device serves, the better suited it is to tactical care. Using devices that can perform multiple functions may enable the provider to lighten the load and leave behind other equipment that serves the same function.

Confirmation of endotracheal tube placement. Emerging evidence suggests that ultrasound of the lung may assist in assessment of intubated patients as an adjunct to confirm proper tube placement (5).
Placement of central and peripheral venous catheters. Studies have shown that ultrasound-guided procedures are more likely to be successful and less likely to result in arterial cannulation or pneumothorax (6,7).
Early recognition of shock. Ultrasound measurement of the inferior vena cava (IVC) may enable the tactical medical provider (TMP) to recognize and treat hypovolemic shock before acute changes in vital signs, mental status, or physical exam (8). The IVC correlates with volume status, shrinking in size as the preload decreases. This information may be useful to the TMP, who must care for casualties over a longer period of time than the typical emergency medical services (EMS) provider.
Detection and assessment of fracture. Ultrasound can detect periosteal fluid collections, interruption or bulging of the cortex, or avulsion of bone. In the field environment, where x-rays are unavailable or require evacuation to a medical facility, ultrasound may provide the TMP with useful clinical information regarding the need for evacuation of a casualty. Fracture reduction may be urgently required in the field to reduce neurovascular compromise and prevent further injury to a fractured arm or leg. Ultrasound may guide the TMP in assessing the success of fracture reduction and visualization of bone alignment.
Detection of pneumothorax. Patients with even a small pneumothorax may develop a tension pneumothorax and rapidly deteriorate once they are under positive-pressure ventilation. Detection of pneumothorax may be difficult in high-noise environments, such as CASEVAC transports, battlefields, or chaotic civilian scenes. Ultrasound can be used to rapidly diagnose clinically significant pneumothorax at the bedside with 98% to 100% sensitivity, exceeding that of supine chest x-ray (9,10).
Detection of foreign bodies. Ultrasound may be used to detect foreign bodies in soft tissue that may have been introduced by shrapnel from explosive devices or fragmentation of bullets. Foreign bodies may be found in abscesses, removal of which will be necessary for the abscess to heal. Of particular interest are foreign bodies in the eye, which require immediate surgical intervention. Fragments or particles may be driven into the eye at a high velocity, going unnoticed by the victim. Likewise the puncture site may not be readily apparent on examination (11).

Vital Signs Monitoring

Trends in vital signs can be the TMP’s first indication of trouble in patients who have suffered illness or internal injury. Automated monitoring of vital signs enables providers to care for multiple patients simultaneously, as they may be alerted to changes in patient condition without the need to be constantly at the bedside. Portable vital signs monitors have been in use in the hospital and air transport realms for decades. In the air transport setting, where auscultating lung sounds or blood pressures is severely limited by engine noise, these monitors are a necessity. Units typically used in this setting have utilized traditional methods of monitoring including electrocardiogram (ECG) leads, a noninvasive blood pressure cuff, and an oxygen saturation plethysmograph connected to the patient with wires. It is no surprise, therefore, that recent technology advances have sought to untangle us from the patient using wireless
technology widely available in many cellular phone and home computer systems.

Vital signs monitoring systems currently available combine the ability to monitor multiple parameters in one compact device. Domestic air medical services have used various models for years with great success. Some models may have operating times of ≥8 hours on a single battery charge. More recent innovations bring connectivity to the field, which has been heretofore unavailable. The Welch-Allyn Propaq (12) series of monitors has been a staple of critical care transport for some time. Newer models have color screens for improved visual interpretation of vital signs, better visibility of warning alarms, and easier differentiation of waveforms.

Blood Pressure Measurement

Blood pressure in most settings is still measured by a noninvasive cuff that is periodically inflated to measure the systolic and diastolic pressures at intervals determined by the care provider. In critical care settings, it is often measured by a pressure transducer connected to a catheter placed in an artery. Recent advances in this area include a cuff that fits around the patient’s wrist to monitor blood pressure noninvasively. The device measures impedance changes in the pulse wave and, therefore, can estimate the blood pressure continuously with each pulse. This potentially offers the advantage of ongoing monitoring without the need for arterial line placement and the potential risk of line infection and vessel damage.

Going Wireless

Vital signs monitoring systems available now or under development are making good use of wireless technology. Newer models are now wireless-capable, with the ability to transmit information from multiple monitors to a computer running an Ethernet local area network (LAN). This means that several of these monitors can be deployed quickly with a computer with wireless Ethernet, creating a central monitoring station where monitor alarms can be detected by care providers. Welch Allyn manufactures a field deployment kit that contains a laptop PC and multiple vitals monitoring stations in a rugged case for fast setup of emergency care environments in the field.

Such systems, which broadcast locally, can place the patient’s vitals on a handheld personal digital assistant (PDA) carried by the TMP, allowing the provider to care for multiple patients and be aware of alarms without being at the patient’s immediate bedside. Systems that are enabled on a wireless network may transmit vitals to a location far removed from the battlefield, allowing a medical provider (such as a physician) the ability to give real-time instructions via radio or other communication modality to the provider in the field.

What the Future Holds

The prototypical tactical wireless vitals monitoring system is LifeGuard, under development by NASA’s Ames Astrobionics Team and Stanford University. The Crew Physiological Observation Device, or CPOD, is a battery-powered unit that utilizes Bluetooth technology to transmit ECG, pulse, respirations, and body position to a nearby computer. This computer can be linked remotely to a receiving station where data can be reviewed in real time by medical providers in virtually any location.

Units under development now include pills that patients can swallow, which provide real-time telemetry of pulse rate and oxygen content. Signals are read by a PDA device at the patient’s side, which may then communicate with the TMP’s computer station or PDA. While these have been tested in the laboratory, time will tell if they are reliable for field use in battlefield casualties.

None of the above devices are currently commercially available for tactical use, but they hold promise as future devices to enhance the TMP’s ability to monitor patients, whether from 10 ft away or 10 miles up.

Smart Textiles

Of great interest to military commanders are clothing items with integrated vital signs monitoring. These devices (SmartShirts) have transducers woven into them for monitoring pulse and respiratory rate. An advantage of these systems is that they can be donned by tactical operators in preparation for a mission and commanders will therefore know exactly when an operator goes down and the operator’s relative condition, to speed planning of evacuation. When the systems are operated remotely, commanders can use data from the sensors to steer a medic toward a wounded operator before the medic is even aware that an operator has gone down. In the acute-care environment, these shirts may free the patient from many of the wires required to monitor ECG, pulse, and respirations.

Pulse Oximetry

Pulse oximetry has been a staple of critical care for years, and has been used in prehospital care since the advent of portable battery-powered units. Pulse oximeters use a special light inside a probe that clips or tapes onto a finger, earlobe, nose, or toe to give real-time monitoring of pulse rate and oxygen saturation. The recent availability of a unit no more than an inch or two in any dimension makes this a viable option to be carried in the TMP’s pack (13). There are also units available that combine pulse oximetry with end-tidal carbon dioxide (EtCO₂) detection (discussed on next page) or detection of carbon monoxide (CO).

End-Tidal Carbon Dioxide Monitoring

End-tidal capnography or capnometry is the measurement of carbon dioxide exhaled by a patient. It has been a standard of monitoring patient condition in the operating room since the late 1980s, and has recently spread to pre-hospital use as a means to confirm and monitor endotracheal tube placement. EtCO₂ monitoring has been found to have a significant impact on preventing misplaced endotracheal tubes in the prehospital setting (14, 15 and 16). It may also be used during insertion of gastric tubes to detect inadvertent cannulation of the trachea (17).

End-tidal capnometry utilizes a clear plastic device that is placed between the endotracheal tube and the bag-valve-mask. A chemically treated paper membrane is displayed in the window of the device, which turns from purple to yellow in the presence of CO₂. When the endotracheal tube is properly placed in the trachea, this membrane will change color back and forth from purple to yellow with each ventilation.

Continuous EtCO₂ monitoring, or capnography, has become available with newer models of monitor/defibrillators as well as pulse oximeters. Unlike the chemical membrane CO₂ detectors, continuous monitors utilize an electronic sensor that is placed between the endotracheal tube and the bag-valve-mask. The patient may be continually monitored by means of a visual waveform on the screen that shows the level of CO₂ exhaled. The level is less important than the waveform, which should rise and fall with each ventilation.

Recently EtCO₂ has evolved as a means of rapid triage of disaster patients exposed to smoke or inhaled chemical agents such as cyanide. A device similar to a nasal oxygen cannula is now available to measure EtCO₂ in nonintubated patients. Within a few breaths, the capnometry waveform can give a reliable indicator of the patient’s ventilatory status as well as the possibility of cellular poisoning by asphyxiants. EtCO₂ level has not been found to reliably correlate with arterial pCO₂ (18). It has been found to provide earlier warning to medical providers that a patient may be hypoventilating than pulse oximetry or respiratory rate (19,20).

Point-of-Care, or Bedside, Blood Testing

Bedside analysis, or point-of-care (POC) testing, utilizes portable electronic devices or chemical reagent strips for identification of enzymes, electrolytes, or substrates in blood or urine without the need to send the sample to a laboratory. Portable units now used at many hospitals have the ability to measure blood gasses, hematocrit, and electrolytes from one sample at the bedside within minutes. These rechargeable units are roughly the size of an eggplant and have the ability to print a small strip with lab results. To examine the utility of POC testing, it is important to know what tests are available and how they may fit into the scope of care of the TMP.

Glucose

Traditionally, blood glucose has been one of the most common field tests performed by this method. Electronic glucometers have become more accurate, faster, and easier to use than ever before, and their use is a skill mastered by the diabetic patient with little training. Chemical reagent strips are also available for use, and though less accurate, they give the provider a rough idea of the patient’s blood glucose level. Hypoglycemia is a potentially serious and very treatable consequence of many diseases, from malnutrition to β-blocker overdose to sepsis.

Arterial Blood Gas

Arterial blood gas is sometimes used to guide care of patients with suspected respiratory distress or altered mental status. Measurements of pH, pO₂, pCO₂, a-A gradient, and base deficit are helpful for adjustment of ventilator parameters on ventilated patients. It is rarely, if ever, helpful in determining if a patient needs to be intubated or requires supplemental oxygen.

Hematocrit

The hematocrit is a measure of the percentage of blood that is comprised by red blood cells. In the absence of cyanide or CO poisoning, it gives a rough idea of the blood’s oxygen-carrying capacity. After hemorrhage, fluid shifts into the vascular space from the tissue, diluting the remaining red blood cells and lowering the hematocrit. This value may guide the clinician in the decision to transfuse blood.

Electrolytes

Ions such as sodium, potassium, and chloride are tightly regulated in body systems, providing gradients that drive the machinery of many processes. Imbalances in these electrolytes, if severe, may be fatal. Dehydration may lead to derangement of sodium and chloride. Operators who rehydrate with plain water, without additional salt intake, may become hyponatremic, causing further symptoms and limiting operational effectiveness. Most worrisome among these electrolyte disturbances is hyperkalemia, which can rapidly be fatal without treatment. Burns and crush injury are potential causes of hyperkalemia that may be encountered in the tactical environment.

Cardiac Markers

Recent availability of POC testing of cardiac markers has opened wider debate about its utility in the field for triage of chest pain patients and for potential reduction of emergency department waiting times for patients who
are undergoing a series of enzymes to rule out myocardial ischemia. For the typical civilian TMP, POC testing requires substantial cost, maintenance, and education, with little benefit. It is unlikely that blood test abnormalities will change care provided in the field or patient outcome. The possible exception to this is glucose testing, which can be effectively accomplished with chemical reagent strips or glucometers for very little cost, space, or weight.

Electrocardiogram

Portable ECG monitors that utilize a PDA as a platform for monitoring have recently become available for field use. These units have a small module that attaches to the PDA to interface with downloaded software. The ECG leads connect to this module for diagnosis and monitoring. Both 3-lead and 12-lead models are available for monitoring and diagnosis, respectively.

Infrascanner

An emerging technology uses an active infrared scanner for the detection of intracranial hemorrhage. Intracranial hemorrhage is a potentially devastating consequence of closed head injury, which, if untreated, may rapidly lead to death. Early detection may lead to earlier evacuation to a facility with neurosurgical expertise available. These units, currently under development, are portable and battery powered. The wireless probe for performance of the test interfaces with a PDA.

OPTICS FOR REMOTE ASSESSMENT

TMPs may be unable to directly access patients who may be injured or ill. Hostile fire or the potential aggravation of a hostage scenario may lead to increased numbers of patients and jeopardize a favorable outcome of the incident. The ability to assess patients before they can be treated may enable the provider to better anticipate resources required for treatment, extrication, or transport. Distance assessment may enable the provider to give appropriate medical advice to laypersons inside the barricade who may be able to access and treat the patient.

Only gold members can continue reading. Log In or Register to continue