Time-Controlled Adaptive Ventilation (TCAV): a personalized strategy for lung protection.

Acute respiratory distress syndrome (ARDS) alters the dynamics of lung inflation during mechanical ventilation. Repetitive alveolar collapse and expansion (RACE) predisposes the lung to ventilator-induced lung injury (VILI). Two broad approaches are currently used to minimize VILI: (1) low tidal volume (LVT) with low-moderate positive end-expiratory pressure (PEEP); and (2) open lung approach (OLA). The LVT approach attempts to protect already open lung tissue from overdistension, while simultaneously resting collapsed tissue by excluding it from the cycle of mechanical ventilation. By contrast, the OLA attempts to reinflate potentially recruitable lung, usually over a period of seconds to minutes using higher PEEP used to prevent progressive loss of end-expiratory lung volume (EELV) and RACE. However, even with these protective strategies, clinical studies have shown that ARDS-related mortality remains unacceptably high with a scarcity of effective interventions over the last two decades. One of the main limitations these varied interventions demonstrate to benefit is the observed clinical and pathologic heterogeneity in ARDS. We have developed an alternative ventilation strategy known as the Time Controlled Adaptive Ventilation (TCAV) method of applying the Airway Pressure Release Ventilation (APRV) mode, which takes advantage of the heterogeneous time- and pressure-dependent collapse and reopening of lung units. The TCAV method is a closed-loop system where the expiratory duration personalizes VT and EELV. Personalization of TCAV is informed and tuned with changes in respiratory system compliance (CRS) measured by the slope of the expiratory flow curve during passive exhalation. Two potentially beneficial features of TCAV are: (i) the expiratory duration is personalized to a given patient's lung physiology, which promotes alveolar stabilization by halting the progressive collapse of alveoli, thereby minimizing the time for the reopened lung to collapse again in the next expiration, and (ii) an extended inspiratory phase at a fixed inflation pressure after alveolar stabilization gradually reopens a small amount of tissue with each breath. Subsequently, densely collapsed regions are slowly ratcheted open over a period of hours, or even days. Thus, TCAV has the potential to minimize VILI, reducing ARDS-related morbidity and mortality.

Gestalt clinical severity score (GCSS) as a predictor of patient severity of illness or injury.

OBJECTIVE: To determine if clinical judgement is accurate to predict the severity of injury or illness, and can be used at patient arrival when other formal scoring systems are not yet available. DESIGN: A multicenter pilot study using a prospective observational convenience sample of patients arriving by EMS to the emergency department (ED) or Trauma Center. SETTING: Two urban, Level 1 trauma centers at academic tertiary care hospitals. PATIENTS: Medical and trauma patients age 18 and older transported by EMS (N = 216). Exclusion criteria (prior to arrival): intubation, assisted ventilation (BVM or NPPV), CPR in progress, prisoners, or previously present motor or speech deficits. MEASUREMENTS: Completion of a novel 15-point scale of Verbal, Motor, and Facial Expression within 1-2 min of arrival by a clinician outside of the treatment team. Primary endpoint was the immediate disposition from the ED or Trauma Center: Home, Brief Observation (<24 h), Admission to Floor, ICU (OR and IR as surrogates since these patients ultimately go to the ICU), or Morgue. RESULTS: Univariate analysis revealed a strong, positive monotonic correlation between GCSS and disposition (Rho = 0.693, p < .0001). Multivariable logistic regression revealed the "best" model included GCSS and age (group 18-44 years old versus all the other age groups) (p < .0001). There was a 156% increase in the odds of being discharged home (versus being admitted) for a one-unit increase in GCSS (OR = 2.56, 95% CI 1.94, 3.37). CONCLUSIONS: Physicians can make accurate predictions of severity of injury and illness using a gestalt method and the scoring system we have developed as patient disposition correlates well with GCSS score. GCSS is most accurate with the 18-44 age group.

Hydropneumothorax Due to Esophageal Rupture.

BACKGROUND: A brief review of the historical aspects of esophageal rupture is presented along with a case and current recommendations for diagnostic evaluation and treatment. CASE REPORT: A 97-year-old woman complained of acute dyspnea without prior vomiting. Chest x-ray study showed a large right pneumothorax with associated effusion. A thoracostomy tube was placed with return of > 1 L turbid fluid with polymicrobial culture and elevated pleural fluid amylase level. Chest computed tomography (CT) scan demonstrated overt leakage of oral contrast into the right pleural space. She was treated with ongoing pleural evacuation, antibiotics, antifungals, and total parenteral nutrition. The patient and family declined surgical resection as well as endoscopic stent placement. In 1724, Boerhaave described spontaneous rupture of the esophagus postmortem; Boerhaave syndrome remains the name for complete disruption of the esophageal wall in the absence of pre-existing pathology typically occurring after vomiting. It most commonly occurs in the distal left posterolateral thoracic esophagus. Contrast esophagram is considered the "gold standard" for diagnosing esophageal rupture although CT esophagography also shows good diagnostic performance. Treatment includes nil per os status, broad-spectrum antibiotics, and drainage of the pleural space. Surgical repair of the esophageal perforation should be done early if the patient is deemed a good candidate, and esophageal stenting is also an option. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Esophageal perforation should be suspected in patients with new pleural effusion, often with overt pneumothorax, that is polymicrobial with elevated amylase.

Incomplete Lemierre syndrome.

An invasive Fusobacterium infection may originate from an apparent routine pharyngitis and lead to significant distant septic complications. Even without internal jugular thrombosis, the same mechanism of disease exists, and therefore, the same morbidity, prognosis, and treatments are applicable, hence the suitable term incomplete Lemierre syndrome. We present a case of invasive Fusobacterium infection that meets all criteria for Lemierre syndrome except lacking internal jugular thrombosis. A review of the literature that forms the diagnostic criteria for this syndrome and the rationale for our creating this novel term is presented.

Brief Report: Diabetic Keto-Acidosis (DKA) Induced Hypothermia may be Neuroprotective in Cardiac Arrest.

Despite the decreased survival associated with diabetes with out-of-hospital cardiac arrest and the overall low survival to hospital discharge, we would like to present two cases of OHCA in diabetics who despite prolonged resuscitation efforts had complete neurological recovery likely due to concomitant hypothermia. There is a steady decreasing rate of ROSC with longer durations of CPR so that outcomes are best when <20 minutes compared to prolonged resuscitation efforts (>30-40 minutes). It has been previously recognized that hypothermia prior to cardiac arrest can be neurologically protective even with up to 9 hours of cardiopulmonary resuscitation. Hypothermia has been associated with DKA and although often indicates sepsis with mortality rates of 30-60%, it may indeed be protective if occurring prior to cardiac arrest. The critical factor for neuroprotection may be a slow drop to a temperature <250C prior to OHCA as is achieved in deep hypothermic circulatory arrest for operative procedures of the aortic arch and great vessels. It may be worthwhile continuing aggressive resuscitation efforts even for prolonged periods before attaining ROSC for OHCA in patients found hypothermic from metabolic illnesses as compared to only from environmental exposures (avalanche victims, cold water submersions, etc.) as has been traditionally reported in the medical literature.

Myths and Misconceptions of Airway Pressure Release Ventilation: Getting Past the Noise and on to the Signal.

In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): "Scientific orthodoxy kills truth". In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of "lung protective" ventilation. Unfortunately, inadequacies of the current conceptual model-that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the "baby lung" - is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controversial modes of mechanical ventilation that shows promise in experimental and clinical data. Over the last 3 decades APRV has evolved from a rescue strategy to a preemptive lung injury prevention approach with potential to stabilize the lung and restore alveolar homogeneity. However, several obstacles have so far impeded the evaluation of APRV's clinical efficacy in large, randomized trials. For instance, there is no universally accepted standardized method of setting APRV and thus, it is not established whether its effects on clinical outcomes are due to the ventilator mode per se or the method applied. In addition, one distinctive issue that hinders proper scientific evaluation of APRV is the ubiquitous presence of myths and misconceptions repeatedly presented in the literature. In this review we discuss some of these misleading notions and present data to advance scientific discourse around the uses and misuses of APRV in the current literature.