Automatic proximal airway volume segmentation using optical coherence tomography for assessment of inhalation injury.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury with a mortality rate of up to 40%. Early management of ARDS has been difficult due to the lack of sensitive imaging tools and robust analysis software. We previously designed an optical coherence tomography (OCT) system to evaluate mucosa thickness (MT) after smoke inhalation, but the analysis relied on manual segmentation. The aim of this study is to assess in vivo proximal airway volume (PAV) after inhalation injury using automated OCT segmentation and correlate the PAV to lung function for rapid indication of ARDS. METHODS: Anesthetized female Yorkshire pigs (n = 14) received smoke inhalation injury (SII) and 40% total body surface area thermal burns. Measurements of PaO2-to-FiO2 ratio (PFR), peak inspiratory pressure (PIP), dynamic compliance, airway resistance, and OCT bronchoscopy were performed at baseline, postinjury, 24 hours, 48 hours, 72 hours after injury. A tissue segmentation algorithm based on graph theory was used to reconstruct a three-dimensional (3D) model of lower respiratory tract and estimate PAV. Proximal airway volume was correlated with PFR, PIP, compliance, resistance, and MT measurement using a linear regression model. RESULTS: Proximal airway volume decreased after the SII: the group mean of proximal airway volume at baseline, postinjury, 24 hours, 48 hours, 72 hours were 20.86 cm (±1.39 cm), 17.61 cm (±0.99 cm), 14.83 cm (±1.20 cm), 14.88 cm (±1.21 cm), and 13.11 cm (±1.59 cm), respectively. The decrease in the PAV was more prominent in the animals that developed ARDS after 24 hours after the injury. PAV was significantly correlated with PIP (r = 0.48, p < 0.001), compliance (r = 0.55, p < 0.001), resistance (r = 0.35, p < 0.01), MT (r = 0.60, p < 0.001), and PFR (r = 0.34, p < 0.01). CONCLUSION: Optical coherence tomography is a useful tool to quantify changes in MT and PAV after SII and burns, which can be used as predictors of developing ARDS at an early stage. LEVEL OF EVIDENCE: Prognostic, level III.

Sociodemographic, behavioral, and environmental factors of child mortality in Eastern Region of Cameroon: results from a social autopsy study.

BACKGROUND: While most child deaths are caused by highly preventable and treatable diseases such as pneumonia, diarrhea, and malaria, several sociodemographic, cultural and health system factors work against children surviving from these diseases. METHODS: A retrospective verbal/social autopsy survey was conducted in 2012 to measure the biological causes and social determinants of under-five years old deaths from 2007 to 2010 in Doume, Nguelemendouka, and Abong-Mbang health districts in the Eastern Region of Cameroon. The present study sought to identify important sociodemographic and household characteristics of the 1-59 month old deaths, including the coverage of key preventive indicators of normal child care, and illness recognition and care-seeking for the children along the Pathway to Survival model. FINDINGS: Of the 635 deceased children with a completed interview, just 26.8% and 11.2% lived in households with an improved source of drinking water and sanitation, respectively. Almost all of the households (96.1%) used firewood for cooking, and 79.2% (n = 187) of the 236 mothers who cooked inside their home usually had their children beside them when they cooked. When 614 of the children became fatally ill, the majority (83.7%) of caregivers sought or tried to seek formal health care, but with a median delay of 2 days from illness onset to the decision to seek formal care. As a result, many (n = 111) children were taken for care only after their illness progressed from mild or moderate to severe. The main barriers to accessing the formal health system were the expenses for transportation, health care and other related costs. CONCLUSIONS: The most common social factors that contributed to the deaths of 1-59-month old children in the study setting included poor living conditions, prevailing customs that led to exposure to indoor smoke, and health-related behaviors such as delaying the decision to seek care. Increasing caregivers' ability to recognize the danger signs of childhood illnesses and to facilitate timely and appropriate health care-seeking, and improving standards of living such that parents or caregivers can overcome the economic obstacles, are measures that could make a difference in the survival of the ill children in the study area.

Case Files of the University of Massachusetts Toxicology Fellowship: Does This Smoke Inhalation Victim Require Treatment with Cyanide Antidote?

Cyanide toxicity is common after significant smoke inhalation. Two cases are presented that provide framework for the discussion of epidemiology, pathogenesis, presenting signs and symptoms, and treatment options of inhalational cyanide poisoning. An evidence-based algorithm is proposed that utilizes point-of-care testing to help physicians identify patients who benefit most from antidotal therapy.

Computed tomographic assessment of airflow obstruction in smoke inhalation injury: Relationship with the development of pneumonia and injury severity.

PURPOSE: The prediction of pulmonary deterioration in patients with smoke inhalation injury is important because this influences the strategy for patient management. We hypothesized that narrowing of the luminal bronchus due to bronchial wall thickening correlates to respiratory deterioration in smoke inhalation injury patients. METHODS: In a prospective observational study, all patients were enrolled at a single tertiary trauma and critical care center. In 40 patients, chest computed tomographic images were obtained within a few hours after smoke inhalation injury. We assessed bronchial wall thickness and luminal area % on chest computed tomographic images. Airway wall thickness to total bronchial diameter (T/D) ratio, percentage of luminal area, and clinical indices were compared between patients with smoke inhalation injury and control patients. RESULTS: The T/D ratio of patients with smoke inhalation was significantly higher than that of control patients (p<0.001), and the luminal area of these patients was significantly smaller than that of control patients (p<0.001). The number of mechanical ventilation days correlated with the initial infusion volume, T/D ratio, and luminal area %. ROC analysis showed a cut-off value of 0.26 for the T/D ratio, with a sensitivity of 79.0% and specificity of 73.7%, and a value of 23.4% for luminal area %, with a sensitivity of 68.4% and specificity of 84.2%. CONCLUSIONS: These data revealed the utility of computed tomography scanning on admission to show that the patients with smoke inhalation injury had airway wall thickening compared to control patients without smoke inhalation injury. Airflow narrowing due to airway wall thickening was related to the development of pneumonia and the number of mechanical ventilation days in patients with smoke inhalation injury. Airflow narrowing is one important factor of respiratory deterioration in smoke inhalation injury.

The utility of bronchoscopy after inhalation injury complicated by pneumonia in burn patients: results from the National Burn Repository.

There are no guidelines to determine when bronchoscopy is appropriate in patients with inhalation injury complicated by pneumonia. We reviewed the National Burn Repository from 1998 to 2007 to determine if there is any difference in outcome in burn patients with inhalation injury and pneumonia who did and did not undergo bronchoscopy. Three hundred fifty-five patients with pneumonia did not undergo bronchoscopy, 173 patients underwent one bronchoscopy, and 96 patients underwent more than one bronchoscopy. Patients with a 30 to 59% surface area burn and pneumonia who underwent bronchoscopy had a decreased duration of mechanical ventilation compared with those who did not (21 days, 95% CI: 19-23 days vs 28 days, 95% CI: 25-31 days, P=.0001). When compared with patients who did not undergo bronchoscopy, patients having a single bronchoscopy had a significantly shorter length of intensive care unit stay and hospital stay (35+/-3 vs 39+/-2, P=.04, and 45+/-3 vs 49+/-2, P=.009). The hospital charges were on average much higher in those patients who did not undergo bronchoscopy, compared with those who did ($473,654+/-44,944 vs $370,572+/-36,602, P=.12). When compared with patients who did not undergo bronchoscopy, patients who did have one or more bronchoscopies showed a reduced risk of death by 18% (OR=0.82, 95% CI: 0.53-1.27, P=.37). Patients with inhalation injury complicated by pneumonia seem to benefit from bronchoscopy. This benefit can be seen in a decreased duration of mechanical ventilation, decreased length of intensive care unit stay, and decreased overall hospital cost. In addition, there was a trend toward an improvement in mortality. The aggressive use of bronchoscopy after inhalation injury may be justified.

The assessment of regional lung mechanics with electrical impedance tomography: a pilot study during recruitment manoeuvres.

OBJECTIVE: The purpose of lung recruitment manoeuvres is to open collapsed lung regions, improve gas exchange and optimise regional lung mechanics. This study investigates the efficacy of recruitment manoeuvres for improving regional ventilation distribution as characterised using electrical impedance tomography (EIT). DESIGN, SUBJECTS, INTERVENTIONS: A ventilated ovine smoke inhalation lung injury model was used. Respiratory mechanics and regional filling capacity of the lung were measured using EIT pre- and post- recruitment and compared to a control group. MEASUREMENTS: EIT, expressed as the time course relation of the regional versus the global impedance change, measured the regional filling capacities of the lung. MAIN RESULTS: After smoke inhalation injury, the dependent lung showed a significantly larger area of collapse and a reduced filling capacity compared to the non-dependent lung. After recruitment the ventilated volume increased and the dependent lung showed improved respiratory mechanics, whereas the non-dependent lung was more likely to be hyper-inflated during tidal breathing. CONCLUSIONS: Lung recruitment manoeuvres have a significant impact on regional lung mechanics and individual measurement of ventilation distribution using EIT may assist to improve ventilatory management.

Tracer kinetic model of regional pulmonary function using positron emission tomography.

To determine the spatial distributions of pulmonary perfusion, shunt, and ventilation, we developed a compartmental model of regional (13)N-labeled molecular nitrogen ((13)NN) kinetics measured from positron emission tomography (PET) images. The model features a compartment for right heart and pulmonary vasculature and two compartments for each region of interest: 1) aerated alveolar units and 2) alveolar units with no gas content (shunting). The model was tested on PET data from normal animals (dogs and sheep) and from animals with experimentally injured lungs simulating acute respiratory distress syndrome. The analysis yielded estimates of regional perfusion, shunt fraction, and specific ventilation with excellent goodness-of-fit to the data (R(2) > 0.99). Model parameters were estimated to within 10% accuracy in the presence of exaggerated levels of experimental noise by using a Monte Carlo sensitivity analysis. Main advantages of the present model are that 1) it separates intraregional blood flow to aerated alveolar units from that shunting across nonaerated units and 2) it accounts and corrects for intraregional tracer removal by shunting blood when estimating ventilation from subsequent washout of tracer. The model was thus found to provide estimates of regional parameters of pulmonary function in sizes of lung regions that could potentially approach the intrinsic resolution for PET images of (13)NN in lung (approximately 7.0 mm for a multiring PET camera).