Putting Medical Boots on the Ground: Lessons from the War in Ukraine and Applications for Future Conflict with Near-Peer Adversaries

In the past 20 years of the Global War on Terror, the US has seen substantial improvements in its system of medical delivery in combat. However, throughout that conflict, enemy forces did not have parity with the weaponry, capability, or personnel of the US and allied forces. War against countries like China and Russia, who are considered near-peer adversaries in terms of capabilities, will challenge battlefield medical care in many different ways. This article reviews the experience of a medical team, Global Surgical and Medical Support Group, that has been providing assistance, training, medical support, and surgical support to Ukraine since the Russian invasion began in February 2022. The team has extensive experience in medicine, surgery, austere environments, conflict zones, and building partner nation capacities. This article compares and contrasts the healthcare systems of this war against the systems used during the Global War on Terror. The lessons learned here could help the US anticipate challenges and successfully plan for the provision of medical care in a future conflict against an adversary with capabilities close to its own.

Joint Trauma System Clinical Practice Guideline (JTS CPG): Prehospital Blood Transfusion. 30 October 2020

This Clinical Practice Guideline (CPG) provides a brief summary of the scientific literature for prehospital blood use, with an emphasis on the en route care environment. Updates include the importance of calcium administration to counteract the deleterious effects of hypocalcemia, minimal to no use of crystalloid, and stresses the importance of involved and educated en route care medical directors alongside at a competent prehospital and en route care providers (see Table 1). With the paradigm shift to use FDA-approved cold stored low titer group O whole blood (CS-LTOWB) along with the operational need for continued use of walking blood banks (WBB) and point of injury (POI) transfusion, there must be focused, deliberate training incorporating the different whole blood options. Appropriate supervision of autologous blood transfusion training is important for execution of this task in support of deployed combat operations as well as other operations in which traumatic injuries will occur. Command emphasis on the importance of this effort as well as appropriate logistical support are essential elements of a prehospital blood program as part of a prehospital/en route combat casualty care system.

Effect of Out-of-Hospital Tranexamic Acid vs Placebo on 6-Month Functional Neurologic Outcomes in Patients With Moderate or Severe Traumatic Brain Injury

IMPORTANCE

Traumatic brain injury (TBI) is the leading cause of death and disability due to trauma. Early administration of tranexamic acid may benefit patients with TBI.

OBJECTIVE

To determine whether tranexamic acid treatment initiated in the out-of-hospital setting within 2 hours of injury improves neurologic outcome in patients with moderate or severe TBI.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, double-blinded, randomized clinical trial at 20 trauma centers and 39 emergency medical services agencies in the US and Canada from May 2015 to November 2017. Eligible participants (N = 1280) included out-of-hospital patients with TBI aged 15 years or older with Glasgow Coma Scale score of 12 or less and systolic blood pressure of 90 mm Hg or higher.

INTERVENTIONS

Three interventions were evaluated, with treatment initiated within 2 hours of TBI: out-of-hospital tranexamic acid (1 g) bolus and in-hospital tranexamic acid (1 g) 8-hour infusion (bolus maintenance group; n = 312), out-of-hospital tranexamic acid (2 g) bolus and in-hospital placebo 8-hour infusion (bolus only group; n = 345), and out-of-hospital placebo bolus and in-hospital placebo 8-hour infusion (placebo group; n = 309).

MAIN OUTCOMES AND MEASURES

The primary outcome was favorable neurologic function at 6 months (Glasgow Outcome Scale-Extended score >4 [moderate disability or good recovery]) in the combined tranexamic acid group vs the placebo group. Asymmetric significance thresholds were set at 0.1 for benefit and 0.025 for harm. There were 18 secondary end points, of which 5 are reported in this article: 28-day mortality, 6-month Disability Rating Scale score (range, 0 [no disability] to 30 [death]), progression of intracranial hemorrhage, incidence of seizures, and incidence of thromboembolic events.

RESULTS

Among 1063 participants, a study drug was not administered to 96 randomized participants and 1 participant was excluded, resulting in 966 participants in the analysis population (mean age, 42 years; 255 [74%] male participants; mean Glasgow Coma Scale score, 8). Of these participants, 819 (84.8%) were available for primary outcome analysis at 6-month follow-up. The primary outcome occurred in 65% of patients in the tranexamic acid groups vs 62% in the placebo group (difference, 3.5%; [90% 1-sided confidence limit for benefit, -0.9%]; P = .16; [97.5% 1-sided confidence limit for harm, 10.2%]; P = .84). There was no statistically significant difference in 28-day mortality between the tranexamic acid groups vs the placebo group (14% vs 17%; difference, -2.9% [95% CI, -7.9% to 2.1%]; P = .26), 6-month Disability Rating Scale score (6.8 vs 7.6; difference, -0.9 [95% CI, -2.5 to 0.7]; P = .29), or progression of intracranial hemorrhage (16% vs 20%; difference, -5.4% [95% CI, -12.8% to 2.1%]; P = .16).

CONCLUSIONS AND RELEVANCE

Among patients with moderate to severe TBI, out-of-hospital tranexamic acid administration within 2 hours of injury compared with placebo did not significantly improve 6-month neurologic outcome as measured by the Glasgow Outcome Scale-Extended.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01990768.

Advanced Resuscitative Care in Tactical Combat Casualty Care: TCCC Guidelines Change 18-01:14 October 2018

TCCC has previously recommended interventions that can effectively prevent 4 of the top 5 causes of prehospital preventable death in combat casualties-extremity hemorrhage, junctional hemorrhage, airway obstruction, and tension pneumothorax- and deaths from these causes have been markedly reduced in US combat casualties. Noncompressible torso hemorrhage (NCTH) is the last remaining major cause of preventable death on the battlefield and often causes death within 30 minutes of wounding. Increased use of whole blood, including the capability for massive transfusion, if indicated, has the potential to increase survival in casualties with either thoracic and/or abdominopelvic hemorrhage. Additionally, Zone 1 Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) can provide temporary control of bleeding in the abdomen and pelvis and improve hemodynamics in casualties who may be approaching traumatic cardiac arrest as a result of hemorrhagic shock. Together, these two interventions are designated Advanced Resuscitative Care (ARC) and may enable casualties with severe NCTH to survive long enough to reach the care of a surgeon. Although Special Operations units are now using whole blood far-forward, this capability is not routinely present in other US combat units at this point in time. REBOA is not envisioned as care that could be accomplished by a unit medic working out of his or her aid bag. This intervention should be undertaken only by designated teams of advanced combat medical personnel with special training and equipment.

Pulsed Dose Oxygen Delivery During Mechanical Ventilation: Impact on Oxygenation

INTRODUCTION

Adequate oxygenation is one of the primary goals of mechanical ventilation. Maintenance of adequate oxygenation and prevention of hypoxemia are the primary goals for the battlefield casualty, but military operations have unique concerns. In military operations, oxygen is a limited resource. A portable oxygen concentrator has the advantage of operating solely from electrical power and theoretically is a never-exhausting supply of oxygen. Our previous bench work demonstrated that the pulsed dose setting of the concentrator can be used in concert with the ventilator to maximize oxygen delivery. We evaluated this ventilator/concentrator system with closed loop control of oxygen output in a porcine model.

MATERIALS AND METHODS

The Zoll 731 portable ventilator and Sequal Saros portable oxygen concentrator were used for this study. The ventilator and concentrator were connected via a USB cable to allow communication. The ventilator was modified to allow closed loop control of oxygen based on the oxygen saturation (SpO2) via the integral pulse oximetry sensor. The ventilator communicates with the concentrator to increase or decrease oxygen bolus size to maintain a target SpO2 of 94%. Three separate experiments were conducted in this study. Experiments 1 and 2 used oxygen bolus sizes 16-96 mL in 16-mL increments and experiment 3 used 1 mL increments. The oxygen bolus was delivered from the concentrator and injected into the ventilator circuit at the patient connector. Six pigs were used for each experiment. Experiment 1, done without lung injury, was completed to determine the optimum timing during the respiratory cycle for injecting the oxygen bolus. Lung injury for experiments 2 and 3 was induced in the animals by warmed saline lavage via the endotracheal tube until PaO2/FIO2 decreased to <100. The pigs were then placed on the ventilator/concentrator system and allowed to adjust the oxygen autonomously to determine if the target SpO2 could be maintained. PEEP was manually adjusted. Arterial blood gases were drawn to verify the PaO2 and the SpO2/SaO2 correlation.

RESULTS

Experiment 1 showed that the O2 bolus injected into the ventilator circuit 300 ms before breath delivery produced the highest PaO2. Mean PaO2/FIO2 was 500 ± 33 for experiments 2 and 3 before lung lavage and 72 ± 11 after lung lavage (p < 0.001), representing severe acute respiratory distress syndrome. Thirty minutes after placing the animals on the ventilator/concentrator system, the bolus size range was 64-96 mL and 16-96 mL after 2 hours (p < 0.05). The SpO2 range was 81-95% after 30 minutes and 94-98% after 2 hours (p < 0.05). PEEP range was 5-14 cm H2O. The SpO2 to SaO2 difference was ≤4% throughout the evaluation.

CONCLUSIONS

The ventilator/concentrator system was able to manage oxygenation of severely injured lungs in a porcine model by injecting oxygen boluses at the front end of the ventilator breath, and appropriate use of PEEP to maximize oxygen delivery at the alveolar level. This proof of concept ventilator system may prove to be of use in situations where high-pressure oxygen is unavailable but electricity is accessible.

Management of Suspected Tension Pneumothorax in Tactical Combat Casualty Care: TCCC Guidelines Change 17-02

This change to the Tactical Combat Casualty Care (TCCC) Guidelines that updates the recommendations for management of suspected tension pneumothorax for combat casualties in the prehospital setting does the following things: (1) Continues the aggressive approach to suspecting and treating tension pneumothorax based on mechanism of injury and respiratory distress that TCCC has advocated for in the past, as opposed to waiting until shock develops as a result of the tension pneumothorax before treating. The new wording does, however, emphasize that shock and cardiac arrest may ensue if the tension pneumothorax is not treated promptly. (2) Adds additional emphasis to the importance of the current TCCC recommendation to perform needle decompression (NDC) on both sides of the chest on a combat casualty with torso trauma who suffers a traumatic cardiac arrest before reaching a medical treatment facility. (3) Adds a 10-gauge, 3.25-in needle/ catheter unit as an alternative to the previously recommended 14-gauge, 3.25-in needle/catheter unit as recommended devices for needle decompression. (4) Designates the location at which NDC should be performed as either the lateral site (fifth intercostal space [ICS] at the anterior axillary line [AAL]) or the anterior site (second ICS at the midclavicular line [MCL]). For the reasons enumerated in the body of the change report, participants on the 14 December 2017 TCCC Working Group teleconference favored including both potential sites for NDC without specifying a preferred site. (5) Adds two key elements to the description of the NDC procedure: insert the needle/ catheter unit at a perpendicular angle to the chest wall all the way to the hub, then hold the needle/catheter unit in place for 5 to 10 seconds before removing the needle in order to allow for full decompression of the pleural space to occur. (6) Defines what constitutes a successful NDC, using specific metrics such as: an observed hiss of air escaping from the chest during the NDC procedure; a decrease in respiratory distress; an increase in hemoglobin oxygen saturation; and/or an improvement in signs of shock that may be present. (7) Recommends that only two needle decompressions be attempted before continuing on to the "Circulation" portion of the TCCC Guidelines. After two NDCs have been performed, the combat medical provider should proceed to the fourth element in the "MARCH" algorithm and evaluate/treat the casualty for shock as outlined in the Circulation section of the TCCC Guidelines. Eastridge's landmark 2012 report documented that noncompressible hemorrhage caused many more combat fatalities than tension pneumothorax.1 Since the manifestations of hemorrhagic shock and shock from tension pneumothorax may be similar, the TCCC Guidelines now recommend proceeding to treatment for hemorrhagic shock (when present) after two NDCs have been performed. (8) Adds a paragraph to the end of the Circulation section of the TCCC Guidelines that calls for consideration of untreated tension pneumothorax as a potential cause for shock that has not responded to fluid resuscitation. This is an important aspect of treating shock in combat casualties that was not presently addressed in the TCCC Guidelines. (9) Adds finger thoracostomy (simple thoracostomy) and chest tubes as additional treatment options to treat suspected tension pneumothorax when further treatment is deemed necessary after two unsuccessful NDC attempts-if the combat medical provider has the skills, experience, and authorizations to perform these advanced interventions and the casualty is in shock. These two more invasive procedures are recommended only when the casualty is in refractory shock, not as the initial treatment.

Bullet retrieval from the right hepatic vein using a controlled endovascular and transhepatic approach

Venous bullet embolism is a rare complication of trauma. We describe a patient who sustained a gunshot wound. Computed tomography revealed antegrade embolization of the bullet to the right hepatic vein (RHV). The risk of not retrieving the bullet embolus and subsequent embolization to the pulmonary circulation includes pulmonary artery thrombosis, bleeding, or abscess formation. The bullet was retrieved through right internal jugular vein access; assisted by percutaneous transhepatic repositioning and endovascular balloon-immobilization of the bullet. The balloon served to "isolate" the bullet within the RHV to avoid the risk of endovascular migration to the pulmonary circulation. Transhepatic access allowed repositioning of the bullet within the RHV leading to successful snare retrieval. This technique demonstrates advantages of percutaneous and endovascular accesses, that repositioned and immobilized the bullet in the RHV to accomplish controlled endovascular retrieval.

Sooner is better: use of a real-time automated bedside dashboard improves sepsis care

BACKGROUND

Minimizing the interval between diagnosis of sepsis and administration of antibiotics improves patient outcomes. We hypothesized that a commercially available bedside clinical surveillance visualization system (BSV) would hasten antibiotic administration and decrease length of stay (LOS) in surgical intensive care unit (SICU) patients.

METHODS

A BSV, integrated with the electronic medical record and displayed at bedside, was implemented in our SICU in July 2016. A visual sepsis screen score (SSS) was added in July 2017. All patients admitted to SICU beds with bedside displays equipped with a BSV were analyzed to determine mean SSS, maximum SSS, time from positive SSS to antibiotic administration, SICU LOS, and mortality.

RESULTS

During the study period, 232 patients were admitted to beds equipped with the clinical surveillance visualization system. Thirty patients demonstrated positive SSS followed by confirmed sepsis (23 Pre-SSS versus 7 Post-SSS). Mean and maximum SSS were similar. Time from positive SSS to antibiotic administration was decreased in patients with a visual SSS (55.3 ± 15.5 h versus 16.2 ± 9.2 h; P < 0.05). ICU and hospital LOS was also decreased (P < 0.01).

CONCLUSIONS

Implementation of a visual SSS into a BSV led to a decreased time interval between the positive SSS and administration of antibiotics and was associated with shorter SICU and hospital LOS. Integration of a visual decision support system may help providers adhere to Surviving Sepsis Guidelines.

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

IMPORTANCE

Advances in the care of the injured patient are perhaps the only benefit of military conflict. One of the unique aspects of the military medical care system that emerged during Operation Iraqi Freedom and Operation Enduring Freedom has been the opportunity to apply existing civilian trauma system standards to the provision of combat casualty care across an evolving theater of operations.

OBJECTIVES

To identify differences in mortality for soldiers undergoing early and rapid evacuation from the combat theater and to evaluate the capabilities of the Critical Care Air Transport Team (CCATT) and Joint Theater Trauma Registry databases to provide adequate data to support future initiatives for improvement of performance.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective review of CCATT records and the Joint Theater Trauma Registry from September 11, 2001, to December 31, 2010, for the in-theater military medicine health system, including centers in Iraq, Afghanistan, and Germany. Of 2899 CCATT transport records, those for 975 individuals had all the required data elements.

EXPOSURE

Rapid evacuation by the CCATT.

MAIN OUTCOMES AND MEASURES

Survival as a function of time from injury to arrival at the role IV facility at Landstuhl Regional Medical Center.

RESULTS

The patient cohort demonstrated a mean Injury Severity Score of 23.7 and an overall 30-day mortality of 2.1%. Mortality en route was less than 0.02%. Statistically significant differences between survivors and decedents with respect to the Injury Severity Score (mean [SD], 23.4 [12.4] vs 37.7 [16.5]; P < .001), cumulative volume of blood transfused among the patients in each group who received a transfusion (P < .001), worst base deficit (mean [SD], -3.4 [5.0] vs -7.8 [6.9]; P = .02), and worst international normalized ratio (median [interquartile range], 1.2 [1.0-1.4] vs 1.4 [1.1-2.2]; P = .03) were observed. We found no statistically significant difference between survivors and decedents with respect to time from injury to arrival at definitive care.

CONCLUSIONS AND RELEVANCE

Rapid movement of critically injured casualties within hours of wounding appears to be effective, with a minimal mortality incurred during movement and overall 30-day mortality. We found no association between the duration of time from wounding to arrival at Landstuhl Regional Medical Center with respect to mortality.

Three-decade metabolic outcome of neonatal gastrectomy and early Roux-en-Y

Little information is available about long-term outcomes of major gastric surgery when performed very early in life and adverse consequences in growing children might be expected. In this case, gastrectomy with Roux-en-Y esophagojejunostomy was performed in early childhood. Despite stomach loss, growth velocity paralleled the third percentile for age during development. Maintained on a daily multivitamin and monthly B12 injections, no overt nutritional deficiencies were detected in adulthood. However, dual energy X-ray absorptiometry scan at age 31 revealed that the patient had abnormally low bone mineral density. This case study demonstrates that even after gastrectomy and reconstruction early in life, linear growth can be achieved. However, bone density can be adversely affected, even in the face of normal serum calcium and vitamin D levels.

Comparison of airway control methods and ventilation success with an automatic resuscitator

Mechanical ventilation in an austere environment is difficult owing to logistics, training, and environmental conditions. We evaluated the ability of professional caregivers to provide ventilatory support to a simulated patient using the Simplified Automated Ventilator (SAVe) with a mask hand attended ventilation, mask with single strap unattended ventilation, and supraglottic airway (King LT) ventilation. All three methods were performed using a SAVe with a set tidal volume of 600ml and respiratory rate of 10 breaths per minute. The simulator consisted of a head and upper torso with anatomically correct upper airway structures, trachea, esophagus, and lung which, also measured the delivered tidal volume, respiratory rate, inspiratory flow, and airway pressures. Volunteers used each airway control method to provide ventilation for 10 minutes in random order. Success of each technique was judged as a mean delivered tidal volume of > 500ml. The major finding of this study was that medical professionals using SAVe resuscitator and the manufacturer supplied face mask with single head strap failed to ventilate the airway model in every case.

KEYWORDS

SAVe, Ventilation, Airway management, Prehospital, Mask Ventilation.

The effect of a change in the surgeon response time mandate on outcomes within Ohio level III trauma centers: it is all about commitment

BACKGROUND

The American College of Surgeons Committee on Trauma guidelines for trauma center verification stipulate that the responsible surgeon be present within 15 minutes of the arrival of a critically injured patient. Recently, these guidelines were liberalized, extending the response time to 30 minutes in level III trauma centers. This study evaluated the potential impact of this guideline change on the delivery of care at Ohio's level III trauma centers. We hypothesized that there would be no measurable difference in the emergency department (ED) length of stay (LOS), ED disposition, and facility mortality after enactment of this mandate, which extended the surgeon response time from 15 minutes to 30 minutes at level III trauma centers.

METHODS

Data were collected from the trauma registries of 13 level III trauma centers in Ohio beginning 2 years before and ending 2 years after June 30, 2004, the day the response time was extended to 30 minutes. Statistical analyses were completed comparing the two groups in terms of demographic and clinical characteristics, surgeon response time, ED disposition, ED LOS, and facility mortality.

RESULTS

A total of 1,076 patients were treated during the 4-year period. The type of trauma, age, and Injury Severity Score were similar between the two groups. The mean (+/-SD) surgeon response times before and after the rule change were 14.8 minutes (+/-19.4 minutes) and 15.5 minutes (+/-22.3 minutes), respectively. The two groups also had similar ED LOS (mean = 2.9, median = 2.5 for both groups), rates of transfer to higher level centers (34.4% vs. 32.8%; p = 0.58), and facility mortality rates (10.0% vs. 11.2%; p = 0.55).

CONCLUSION

The extension of the surgeon response time from 15 minutes to 30 minutes did not adversely affect the outcomes of trauma patients at Ohio's level III trauma centers. Furthermore, the surgeon response time was similar before and after the rule change.

Pharmacokinetics and lung delivery of PDDS-aerosolized amikacin (NKTR-061) in intubated and mechanically ventilated patients with nosocomial pneumonia

Introduction

Aminoglycosides aerosolization might achieve better diffusion into the alveolar compartment than intravenous use. The objective of this multicenter study was to evaluate aerosol-delivered amikacin penetration into the alveolar epithelial lining fluid (ELF) using a new vibrating mesh nebulizer (Pulmonary Drug Delivery System (PDDS), Nektar Therapeutics), which delivers high doses to the lungs.

Methods

Nebulized amikacin (400 mg bid) was delivered to the lungs of 28 mechanically ventilated patients with Gram-negative VAP for 7-14 days, adjunctive to intravenous therapy. On treatment day 3, 30 minutes after completing aerosol delivery, all the patients underwent bronchoalveolar lavage in the infection-involved area and the ELF amikacin concentration was determined. The same day, urine and serum amikacin concentrations were determined at different time points.

Results

Median (range) ELF amikacin and maximum serum amikacin concentrations were 976.1 (135.7-16127.6) and 0.9 (0.62-1.73) μg/mL, respectively. The median total amount of amikacin excreted in urine during the first and second 12-hour collection on day 3 were 19 (12.21-28) and 21.2 (14.1-29.98) μg, respectively. During the study period, daily through amikacin measurements were below the level of nephrotoxicity. Sixty-four unexpected adverse events were reported, among which 2 were deemed possibly due to nebulized amikacin: one episode of worsening renal failure, and one episode of bronchospasm.

Conclusions

PDDS delivery of aerosolized amikacin achieved very high aminoglycoside concentrations in ELF from radiography-controlled infection-involved zones, while maintaining safe serum amikacin concentrations. The ELF concentrations always exceeded the amikacin minimum inhibitory concentrations for Gram-negative microorganisms usually responsible for these pneumonias. The clinical impact of amikacin delivery with this system remains to be determined.

Trial Registration

ClinicalTrials.gov Identifier: NCT01021436.

Closed loop control of oxgenation and ventilation

Closed loop control of oxygenation and ventilation during mechanical ventilatory support is essential for remote medical care in an austere environment. Closed loop control allows for expert systems to provide the current standard of care in the absence of on-site expertise. Ventilation may be controlled by simple systems incorporating patient height or by advanced systems incorporating measurements of end-tidal carbon dioxide (ETCO2) and pulmonary impedance. Oxygenation may be controlled by adjustments of inspired oxygen concentrations (FIO2) and positive end-expiratory pressure (PEEP) using pulse oximetry (SpO2) as the input. Control of oxygenation can prevent hypoxemia and has the potential to reduce oxygen requirements. A double closed loop system of oxygenation control including control of FIO2 via SpO2 and control of oxygen generation by a portable oxygen generator (POG) based on FIO2 and minute ventilation (VE) promises safety and efficiency. Remote control of ventilation and oxygenation is possible using existing technology.

Effect of recombinant surfactant protein C-based surfactant on the acute respiratory distress syndrome

BACKGROUND

Preclinical studies suggest that exogenous surfactant may be of value in the treatment of the acute respiratory distress syndrome (ARDS), and two phase 2 clinical trials have shown a trend toward benefit. We conducted two phase 3 studies of a protein-containing surfactant in adults with ARDS.

METHODS

In two multicenter, randomized, double-blind trials involving 448 patients with ARDS from various causes, we compared standard therapy alone with standard therapy plus up to four intratracheal doses of a recombinant surfactant protein C-based surfactant given within a period of 24 hours.

RESULTS

The overall survival rate was 66 percent 28 days after treatment, and the median number of ventilator-free days was 0 (68 percent range, 0 to 26); there was no significant difference between the groups in terms of mortality or the need for mechanical ventilation. Patients receiving surfactant had a significantly greater improvement in blood oxygenation during the initial 24 hours of treatment than patients receiving standard therapy, according to both univariate and multivariate analyses.

CONCLUSIONS

The use of exogenous surfactant in a heterogeneous population of patients with ARDS did not improve survival. Patients who received surfactant had a greater improvement in gas exchange during the 24-hour treatment period than patients who received standard therapy alone, suggesting the potential benefit of a longer treatment course.

High-frequency oscillatory ventilation for adult respiratory distress syndrome--a pilot study

OBJECTIVE

To evaluate the safety and effectiveness of high-frequency oscillatory ventilation using a protocol designed to recruit and maintain optimal lung volume in patients with severe adult respiratory distress syndrome (ARDS).

SETTING

Surgical and medical intensive care units in a tertiary care, military teaching hospital.

DESIGN

A prospective, clinical study.

PATIENTS

Seventeen patients, 17 yrs to 83 yrs of age, with severe ARDS (Lung Injury Score of 3.81 +/- 0.23) failing inverse ratio mechanical conventional ventilation (PaO2/FiO2 ratio of 68.6 +/- 21.6, peak inspiratory pressure of 54.3 +/- 12.7 cm H2O, positive end-expiratory pressure of 18.2 +/- 6.9 cm H2O).

INTERVENTIONS

High-frequency oscillatory ventilation was instituted after varying periods of conventional ventilation (5.12 +/- 4.3 days). We employed lung volume recruitment strategy that consisted of incremental increases in mean airway pressure to achieve a PaO2 of > or = 60 torr (> or = 8.0 kPa), with an FiO2 of < or = 0.6.

MEASUREMENTS AND MAIN RESULTS

High-frequency oscillator ventilator settings (FiO2, mean airway pressure, pressure amplitude of oscillation [delta P] frequency) and hemodynamic parameters (cardiac output, oxygen delivery [DO2]), mean systemic and pulmonary arterial pressures, and the oxygenation index (oxygenation index = [FiO2 x mean airway pressure x 100]/PaO2) were monitored during the transition to high-frequency oscillatory ventilation and throughout the course of the high-frequency protocol. Thirteen patients demonstrated improved gas exchange and an overall improvement in PaO2/FiO2 ratio (p < .02). Reductions in the oxygenation index (p < .01) and FiO2 (p < .02) at 12, 24, and 48 hrs after starting high-frequency oscillatory ventilation were observed. No significant compromise in cardiac output or DO2 was observed, despite a significant increase in mean airway pressure (31.2 +/- 10.3 to 34.0 +/- 6.7 cm H2O, p < .05) on high-frequency oscillatory ventilation. The overall survival rate at 30 days was 47%. A greater number of pretreatment days on conventional ventilation (p < .009) and an entry oxygenation index of > 47 (sensitivity 100%, specificity 100%) were associated with mortality.

CONCLUSIONS

High-frequency oscillatory ventilation is both safe and effective in adult patients with severe ARDS failing conventional ventilation. A lung volume recruitment strategy during high-frequency oscillatory ventilation produced improved gas exchange without a compromise in DO2. These results are encouraging and support the need for a prospective, randomized trial of algorithm-controlled conventional ventilation vs. high-frequency oscillatory ventilation for adults with severe ARDS.