U.S. Military Advanced Critical Care Air Transport

2015 - 2 April – Clinical Controversies
David Zonies, MD, MPH, FACS, FCCM; Jeremy C. Pamplin, MD, FACP, FCCM; Col. Raymond Fang, MD
Three experts discuss the U.S. Military’s advanced transportation system for the critically injured.


Historically, patient movement from a combat zone back to the United States took weeks to months.  During the Vietnam conflict, the average evacuation took 45 days. Little changed over the ensuing years. In the first Gulf War, the established aeromedical system was designed to move high-acuity patients needing critical care support; yet, military doctrine dictated prolonged care in deployed field hospitals. Changing paradigms of critical care and the growing concept of “damage control” resuscitation produced a gap in the transfer of ICU-level casualties—those who were “stabilized” but required significant logistical support and who could not be transported using existing aeromedical systems. What was required was a new program designed to move such patients, a program that included enhanced clinical training, new flight-approved medical equipment and the logistics necessary to provide seamless care across the globe. The U.S. Air Force’s Critical Care Air Transport Team (CCATT) program was initiated in 1994. This addition to the aeromedical evacuation capability enabled the long-range transport of mechanically ventilated patients and revolutionized the military’s medical planning and operations.
 
The long-range transport of patients in a mobile intensive care unit (ICU) has evolved over the past two decades. Patients are now stabilized in forward areas utilizing small resource requirements and then transported with high-level, en-route care to regional military medical treatment facilities both overseas and in the United States. Since 2001, the military has evacuated more than 8,000 patients by CCATT. Most were traumatically injured (40% to 65%), and approximately 50% were mechanically ventilated. As a result of this enhanced capability, rapid aeromedical transportation of patients from point of injury to definitive care in the United States now takes two to four days.(1) 

Based on an earlier model of care established by the U.S. Army’s Burn Flight Team, a three-member CCATT consists of a physician with critical care experience, a critical care nurse and a respiratory therapist.  Candidates are vetted by a panel of mission-experienced peers before they begin training to deliver care in the aeromedical environment. Candidates must pass a final “check-ride” involving simulated missions and high-fidelity patient simulators, challenging their knowledge, skills and temperament. By doctrine, each validated team can care for three high-acuity, ventilated patients; members assist one another as the workload dictates for missions that may be more than 24 hours in duration.

Aeromedical evacuation missions are flown on “aircraft of opportunity” with no intrinsic medical capability.  The C-130 Hercules is commonly flown for tactical missions (short-range, within a theater of operations) and the C-17 Globemaster III for strategic missions (long-range, between theaters of operation). Military aircraft cabins are generally pressurized to an altitude of 8,000 feet above sea level, which may exacerbate hypoxemia and add complexity to the critical care provided. If necessary, pressurization to lower cabin altitudes is possible, but this consumes additional fuel, decreases flight range and lengthens mission time (especially if refueling becomes necessary). During flight, available clinical expertise, medical equipment and supplies (including medications) are limited to those brought aboard by the CCATT itself. The development and maturation of the CCATT was the key catalyst in rapid movement of critically injured service members and has provided a survival advantage.

Registry data from the wars in Afghanistan and Iraq demonstrated that more than 10% of combat casualties developed a severe pulmonary injury. One in six of these patients failed conventional therapy and, more importantly, needed to be evacuated with moderate-to-severe acute respiratory distress syndrome (ARDS). Such patients were managed with lung-protective mechanical ventilation strategies based on ARDSNet guidelines. In most military environments, continued support of these patients necessitated CCATT evacuation for their extended care. Military flight-approved ventilators were developed to provide time-cycled, pressure-limited mechanical ventilation. Such ventilators contain an internal gas compressor and blender that compensates for changes in ambient barometric pressure to maintain consistent tidal volumes during flight.

For patients in whom conventional ventilation strategies fail, rescue therapies may be required.  A specialized Acute Lung Rescue Team (ALRT) was developed in 2005 to address advanced pulmonary failure in this population.(2)  This new team extended the CCATT mission to involve subspecialty critical care intensivists, critical care nurses and respiratory therapists with broad, ongoing experience with critical care patient management. Therapeutic modalities suitable for flight included prone positioning, high-frequency percussive ventilation, inhaled prostacyclin, and intravenous buffer therapy. Over the same time period, advances in technology (smaller equipment with increased reliability) expanded the available critical care devices that were approved for use in flight, enabling a wider range of cardiopulmonary support strategies to be utilized. First, from 2005 to 2010, a pumpless extracorporeal lung support system that utilized an arteriovenous shunt was used in flight as a final support option for severe respiratory failure.(3)  In 2010, the team expanded its capability to include a miniaturized centrifugal pump extracorporeal membrane oxygenation (ECMO) system. This was first used in a soldier who sustained a traumatic pneumonectomy requiring full pulmonary support to survive.(4) To date, more than a dozen casualties from allied countries have been transported by this team using these advanced technologies. This pairing of expertise and technology has allowed the rapid evacuation of patients previously deemed too sick to fly to higher levels of care and has prevented the delay of critical therapies otherwise unavailable in combat. In late 2010, “down range” advances included continuous renal replacement therapy at the air hub hospital of northern Afghanistan.
 
These endeavors are labor intensive, expensive and potentially place teams in harm’s way. Strict criteria were established to utilize these resources appropriately. Prior to official ALRT activation, a remote consultation with the care team at the patient’s bedside occurred. During this consultation, ALRT staff would recommend additional therapeutic maneuvers that might improve a patient enough to become eligible for typical CCATT transport.  If this proved unsuccessful, activation of the ALRT would result in the team’s departure on the next available aircraft of opportunity. Once on-site, the ALRT assumed responsibility for the patient, reviewing the evolution of the clinical course and applying whatever advanced management techniques were deemed necessary to optimize the patient for transport. If ECMO was indicated, the team would cannulate the patient. Once stable enough for flight, the patient would be transported to a receiving hospital in Europe with the ALRT continuing to provide high-level critical care. Over the past decade, a special relationship developed between the U.S. military intensivists and the intensive care group of the University Hospital Regensburg in Germany, a major European extracorporeal life support center. Multidisciplinary care was provided through a co-management strategy for critically ill patients requiring extracorporeal support. More recently, the military has established a U.S.-based program in San Antonio, Texas, USA.

En-route critical care has significantly contributed to combat casualty survival with good functional outcome. The maturation of the military health system will continue to codify this experience and may offer several examples to improve civilian practice as well. Key lessons learned are: 1) transportation of critically ill and injured patients across large distances and with multiple handoffs of care is possible and can be made safe through process improvement and close monitoring; 2) handoff communication and effective documentation that travels with the patient maintains situational awareness across care teams and through hospital systems, as has been demonstrated with the burn resuscitation guidelines(5); and 3) the success of this system is dependent on the integration of training, experience, technology, checklists, communication, and most importantly, a dedicated process to monitor and improve the processes over time. 

Throughout the most recent conflicts, the U.S. military has been able to develop a system that delivers the same level of critical care in any environment—a system that delivers such care continuously during casualty evacuation with the ultimate goal of providing multiple organ support therapy to combat casualties whenever necessary.(6) As combat operations have thankfully ended, it becomes increasingly important for the efficacious components of this system to be translated into a civilian context. This is necessary to maintain competency and proficiency. The process then becomes cyclical: the system should be further refined within the civilian context, so that the military can implement the refined and improved system in future operations.

References:

1. Ingalls N, Zonies D, Bailey JA, et al. A review of the first 10 years of critical care aeromedical transport during Operation Iraqi Freedom and Operation Enduring Freedom: the importance of evacuation timing. JAMA Surg. 2014;149:807–813.
2. Dorlac GR, Fang R, Pruitt VM, et al. Air transport of patients with severe lung injury: development and utilization of the Acute Lung Rescue Team. J Trauma. 2009;66:S164–S171.
3. Bein T, Zonies D, Philipp A, et al. Transportable extracorporeal lung support for rescue of severe respiratory failure in combat casualties. J Trauma Acute Care Surg. 2012;73:1450–1456.
4. Allan PF, Osborn EC, Bloom BB, Wanek S, Cannon JW. The introduction of extracorporeal membrane oxygenation to aeromedical evacuation. Mil Med. 2011;176:932–937.
5. Renz EM, Cancio LC, Barillo DJ, et al. Long range transport of war-related burn casualties. J  Trauma. 2008; 64:S136–S144;  discussion S144–S145.
6. Neff LP, Cannon JW, Stewart IJ, et al. Extracorporeal organ support following trauma: the dawn of a new era in combat casualty critical care. J Trauma Acute Care Surg. 2013;75:S120–S128; discussion S128–S29.