Thomas B. Zanders

Comparison of airway pressure release ventilation to conventional mechanical ventilation in the early management of smoke inhalation injury in swine.

Objective:The role of airway pressure release ventilation in the management of early smoke inhalation injury has not been studied. We compared the effects of airway pressure release ventilation and conventional mechanical ventilation on oxygenation in a porcine model of acute respiratory distress syndrome induced by wood smoke inhalation. Design:Prospective animal study. Setting:Government laboratory animal intensive care unit. Patients:Thirty-three Yorkshire pigs. Interventions:Smoke inhalation injury. Measurements and Main Results:Anesthetized female Yorkshire pigs (n = 33) inhaled room-temperature pine-bark smoke. Before injury, the pigs were randomized to receive conventional mechanical ventilation (n = 15) or airway pressure release ventilation (n = 12) for 48 hrs after smoke inhalation. As acute respiratory distress syndrome developed (PaO2/Fio2 ratio <200), plateau pressures were limited to <35 cm H2O. Six uninjured pigs received conventional mechanical ventilation for 48 hrs and served as time controls. Changes in PaO2/Fio2 ratio, tidal volume, respiratory rate, mean airway pressure, plateau pressure, and hemodynamic variables were recorded. Survival was assessed using Kaplan-Meier analysis. PaO2/Fio2 ratio was lower in airway pressure release ventilation vs. conventional mechanical ventilation pigs at 12, 18, and 24 hrs (p < .05) but not at 48 hrs. Tidal volumes were lower in conventional mechanical ventilation animals between 30 and 48 hrs post injury (p < .05). Respiratory rates were lower in airway pressure release ventilation at 24, 42, and 48 hrs (p < .05). Mean airway pressures were higher in airway pressure release ventilation animals between 6 and 48 hrs (p < .05). There was no difference in plateau pressures, hemodynamic variables, or survival between conventional mechanical ventilation and airway pressure release ventilation pigs. Conclusions:In this model of acute respiratory distress syndrome caused by severe smoke inhalation in swine, airway pressure release ventilation-treated animals developed acute respiratory distress syndrome faster than conventional mechanical ventilation-treated animals, showing a lower PaO2/Fio2 ratio at 12, 18, and 24 hrs after injury. At other time points, PaO2/Fio2 ratio was not different between conventional mechanical ventilation and airway pressure release ventilation.

Inflammatory mediators in smoke inhalation injury.

Smoke inhalation occurs in 10% to 30% of patients admitted to burn centers, and increases mortality by a maximum of 20% over that predicted by age and extent of cutaneous burn alone. Pneumonia in these patients then further increases mortality by a maximum of 40%. While one estimate suggested that 75% of deaths following burn injury may be accounted for by inhalation injury, more recent cohort studies have suggested there is a decreasing mortality attributable to inhalation injury. As part of understanding and improving outcomes from burn injuries, the pathophysiology and inflammatory processes involved in smoke inhalation injury has been extensively investigated in animal models. This review will emphasize the inflammatory pathways involved in inhalation injury, and targeted methods used to treat this injury in both experimental and human models.

A 49-Year-Old Man With Concurrent Diagnoses of Lung Cancer, Sarcoidosis, and Multiple Regions of Adenopathy on Positron Emission Tomography

(CHEST 2009; 135:546–549) A 49-year-old, white man with a 100–pack-year smoking history presented with progressive scapular paresthesias and pain radiating down his right arm for 6 weeks. His medical history was significant for low-grade transitional cell bladder cancer status post transurethral bladder resection. He had multiple chemical exposures as a military aviator. He presented to another institution, where a CT chest scan demonstrated a 4.5 2.5-cm right apical lobulated and necrotic mass, bilateral hilar and subcarinal adenopathy, and tree-in-bud interstitial markings (Fig 1). He underwent fiberoptic bronchoscopy (FOB) with transbronchial biopsy (TBBx) of the right upper lobe (RUL) and transbronchial needle aspiration (TBNA) of a subcarinal lymph node. The TBBx demonstrated noncaseating granulomas, and subcarinal biopsy specimens showed lymphoid tissue without malignancy. He then presented to our institution for evaluation of increasing back and right arm pain. Physical examination was normal except for point tenderness over the suprascapular region of the right upper back with no palpable adenopathy.

Diagnosis and management of chronic lung disease in deployed military personnel

Military personnel are a unique group of individuals referred to the pulmonary physician for evaluation. Despite accession standards that limit entrance into the military for individuals with various pre-existing lung diseases, the most common disorders found in the general population such as asthma and chronic obstructive pulmonary disease remain frequently diagnosed. Military personnel generally tend to be a more physically fit population who are required to exercise on a regular basis and as such may have earlier presentations of disease than their civilian counterparts. Exertional dyspnea is a common complaint; establishing a diagnosis may be challenging given the subtle nature of symptoms and lack of specificity with pulmonary function testing. The conflicts over the past 10 years in Iraq and Afghanistan have also given rise to new challenges for deployed military. Various respiratory hazards in the deployed environment include suspended geologic dusts, burn pits, vehicle exhaust emissions, industrial air pollution, and isolated exposure incidents and may give rise to both acute respiratory symptoms and chronic lung disease. In the evaluation of deployed military personnel, establishing the presence of actual pulmonary disease and the relationship of existing disease to deployment is an ongoing issue to both military and civilian physicians. This paper reviews the current evidence for chronic lung disease in the deployed military population and addresses any differences in diagnosis and management.

Comparison of virtual bronchoscopy to fiber-optic bronchoscopy for assessment of inhalation injury severity ☆

PURPOSE Compare virtual bronchoscopy (VB) to fiberoptic bronchoscopy (FOB) for scoring smoke inhalation injury (SII). METHODS Swine underwent computerized tomography (CT) with VB and FOB before (0) and 24 and 48 h after SII. VB and FOB images were scored by 5 providers off line. RESULTS FOB and VB scores increased over time (p<0.001) with FOB scoring higher than VB at 0 (0.30±0.79 vs. 0.03±0.17), 24 h (4.21±1.68 vs. 2.47±1.50), and 48h (4.55±1.83 vs. 1.94±1.29). FOB and VB showed association with PaO2-to-FiO2 ratios (PFR) with areas under receiver operating characteristic curves (ROC): for PFR≤300, VB 0.830, FOB 0.863; for PFR≤200, VB 0.794, FOB 0.825; for PFR≤100, VB 0.747, FOB 0.777 (all p<0.001). FOB showed 80.3% specificity, 77% sensitivity, 88.8% negative-predictive value (NPV), and 62.3% positive-predictive value (PPV) for PFR≤300 and VB showed 67.2% specificity, 85.5% sensitivity, 91.3% NPV, and 53.4% PPV. CONCLUSIONS VB provided similar injury severity scores to FOB, correlated with PFR, and reliably detected airway narrowing. VB performed during admission CT may be a useful screening tool specifically to demonstrate airway narrowing induced by SII.

Monitoring, Sedation, and Anesthesia for Flexible Fiberoptic Bronchoscopy

Since the advent of flexible fiberoptic bronchoscopy (FFB) in the 1970’s, the use of sedation and topical anesthesia has allowed the practice of bronchoscopy, specifically FFB, to evolve from the operating room to the outpatient setting. Early techniques of general anesthesia and regional blockade of nerves innervating the airway have been largely replaced by improved techniques of patient monitoring, intravenous conscious sedation, and application of topical anesthetics in the airway. Today the bronchoscopist, in addition to basic FFB techniques such as bronchoalveolar lavage and transbronchial biopsy, can also perform complicated procedures such as removal of foreign bodies, ablation of airway tumors, and endobronchial stenting, all in the outpatient bronchoscopy suite. A continued emphasis has been placed on improvements in patient safety due to the complexities of the procedure itself, but also the role of conscious sedation and topical anesthetics to ensure maximal performance by the bronchoscopist to achieve the desired goal of successful biopsy or other interventions while the patient remains comfortable throughout the entire procedure. A full understanding of the patient’s medical history, underlying risk factors such as cardiovascular and pulmonary disease, and medication use is required to plan the requirements for the FFB.