Use of a single ventilator to support 4 patients: laboratory evaluation of a limited concept.

INTRODUCTION: A mass-casualty respiratory failure event where patients exceed available ventilators has spurred several proposed solutions. One proposal is use of a single ventilator to support 4 patients. METHODS: A ventilator was modified to allow attachment of 4 circuits. Each circuit was connected to one chamber of 2 dual-chambered, test lungs. The ventilator was set at a tidal volume (V(T)) of 2.0 L, respiratory frequency of 10 breaths/min, and PEEP of 5 cm H(2)O. Tests were repeated with pressure targeted breaths at 15 cm H(2)O. Airway pressure, volume, and flow were measured at each chamber. The test lungs were set to simulate 4 patients using combinations of resistance (R) and compliance (C). These included equivalent C and R, constant R and variable C, constant C and variable R, and variable C and variable R. RESULTS: When R and C were equivalent the V(T) distributed to each chamber of the test lung was similar during both volume (range 428-442 mL) and pressure (range 528-544 mL) breaths. Changing C while R was constant resulted in large variations in delivered V(T) (volume range 257-621 mL, pressure range 320-762 mL). Changing R while C was constant resulted in a smaller variation in V(T) (volume range 418-460 mL, pressure range 502-554 mL) compared to only C changes. When R and C were both varied, the range of delivered V(T) in both volume (336-517 mL) and pressure (417-676 mL) breaths was greater, compared to only R changes. CONCLUSIONS: Using a single ventilator to support 4 patients is an attractive concept; however, the V(T) cannot be controlled for each subject and V(T) disparity is proportional to the variability in compliance. Along with other practical limitations, these findings cannot support the use of this concept for mass-casualty respiratory failure.

Incidence and Cause of Potentially Preventable Death after Civilian Public Mass Shooting in the US.

BACKGROUND: The incidence and severity of civilian public mass shooting (CPMS) events continue to rise. Understanding the wounding pattern and incidence of potentially preventable death (PPD) after CPMS is key to updating prehospital response strategy. METHODS: A retrospective study of autopsy reports after CPMS events identified via the Federal Bureau of Investigation CPMS database from December 1999 to December 31, 2017 was performed. Sites of injury, fatal injury, and incidence of PPD were determined independently by a multidisciplinary panel composed of trauma surgery, emergency medicine, critical care paramedicine, and forensic pathology. RESULTS: Nineteen events including 213 victims were reviewed. Mean number of gunshot wounds per victim was 4.1. Sixty-four percent of gunshots were to the head and torso. The most common cause of death was brain injury (52%). Only 12% (26 victims) were transported to the hospital and the PPD rate was 15% (32 victims). The most commonly injured organs in those with PPD were the lung (59%) and spinal cord (24%). Only 6% of PPD victims had a gunshot to a vascular structure in an extremity. CONCLUSIONS: The PPD rate after CPMS is high and is due mostly to non-hemorrhaging chest wounds. Prehospital care strategy should focus on immediate point of wounding care by both laypersons and medical personnel, as well as rapid extrication of victims to definitive medical care.

Patient-ventilator asynchrony in a traumatically injured population.

BACKGROUND: Prolonged mechanical ventilation, longer hospital stay, and a lower rate of home discharge have been reported with patient-ventilator asynchrony in medical patients. Though commonly encountered, asynchrony is poorly defined within the traumatically injured population. METHODS: Mechanically ventilated trauma patients at an urban, level-1 center were enrolled. Breath waveforms were recorded over 30 min within the first 48 hours following intubation. Asynchronous breaths were defined as ineffective patient triggering, double-triggering, short-cycle breaths, and long-cycle breaths. Asynchronous subjects were defined as having asynchrony in ≥ 10% of total breaths. Demographic, injury, sedation/delirium scores, and clinical and discharge outcomes were prospectively collected. RESULTS: We enrolled 35 subjects: median age 47 y, 77.1% male, 28.6% with penetrating injuries, 16% with a history of COPD, median (IQR) Injury Severity Score 22 (17-27), and median (IQR) chest Abbreviated Injury Scale score 2 (0-6). We analyzed 15,445 breaths. Asynchrony was present in 25.7% of the subjects. No statistical differences between the asynchronous and non-asynchronous subjects were found for age, sex, injury mechanism, COPD history, delirium/sedation scores, PaO2/FIO2, PEEP, blood gas values, or sedative, narcotic, or haloperidol use. Asynchronous subjects more commonly used synchronized intermittent mandatory ventilation (SIMV) (100% vs. 38.5%, P = .002) and took fewer median spontaneous breaths/min: 4 breaths/min (IQR 3-8 breaths/min) vs. 12 breaths/min (IQR 9-14 breaths/min) (P = .007). SIMV with set breathing frequencies of ≥ 10 breaths/min was associated with increased asynchrony rates (85.7% vs. 14.3%, P = .02). We found no difference in ventilator days, ICU or hospital stay, percent discharged home, or mortality between the asynchronous and non-asynchronous subjects. CONCLUSIONS: Ventilator asynchrony is common in trauma patients. It may be associated with SIMV with a set breathing frequency of ≥ 10 breaths/min, though not with longer mechanical ventilation, longer stay, or discharge disposition. (ClinicalTrials.gov NCT01049958).