Electric Cell-Substrate Impedance Sensing (ECIS) as a Platform for Evaluating Barrier-Function Susceptibility and Damage from Pulmonary Atelectrauma

Biophysical insults that either reduce barrier function (COVID-19, smoke inhalation, aspiration, and inflammation) or increase mechanical stress (surfactant dysfunction) make the lung more susceptible to atelectrauma. We investigate the susceptibility and time-dependent disruption of barrier function associated with pulmonary atelectrauma of epithelial cells that occurs in acute respiratory distress syndrome (ARDS) and ventilator-induced lung injury (VILI). This in vitro study was performed using Electric Cell-substrate Impedance Sensing (ECIS) as a noninvasive evaluating technique for repetitive stress stimulus/response on monolayers of the human lung epithelial cell line NCI-H441. Atelectrauma was mimicked through recruitment/derecruitment (RD) of a semi-infinite air bubble to the fluid-occluded micro-channel. We show that a confluent monolayer with a high level of barrier function is nearly impervious to atelectrauma for hundreds of RD events. Nevertheless, barrier function is eventually diminished, and after a critical number of RD insults, the monolayer disintegrates exponentially. Confluent layers with lower initial barrier function are less resilient. These results indicate that the first line of defense from atelectrauma resides with intercellular binding. After disruption, the epithelial layer community protection is diminished and atelectrauma ensues. ECIS may provide a platform for identifying damaging stimuli, ventilation scenarios, or pharmaceuticals that can reduce susceptibility or enhance barrier-function recovery.

Circulating cell-free DNA as a potential marker in smoke inhalation injury

Failure in evaluation of smoke inhalation injury (SII) is related to increased morbidity and mortality. Prognostic biomarkers that reflect the injury are undoubtedly needed. Cell-free DNA (CFD) concentrations are associated to the extent of tissue damage and inflammation in various pathologies. We have developed a simple assay for CFD quantification and previously found it prognostic in various pathologies including burns, lung disease, and sepsis. The aim of this study was to evaluate admission CFD as an injury severity marker in patients with SII.In a prospective study, we measured admission CFD levels in 18 SII patients and matched control subjects. Daily CFD levels were also performed in 4 hospitalized patients. Serum CFD levels were measured by our direct rapid fluorometric assay.Admission CFD levels of SII patients were significantly higher than those of healthy controls, 879 (236-3220) ng/mL vs. 339 (150-570) ng/mL, [median (range)], P < .0001. Admission CFD levels of hospitalized patients were significantly higher than those of nonhospitalized patients, 1517 (655-3220) ng/mL vs. 675 (236-1581) ng/mL, P < .05. Admission CFD positively correlated with hospitalization time (Rho = 0.578, P < .05) and was in linear correlation with CO poisoning (carboxyhemoglobin (COHb) levels, R = 0.621, P < .0001). Additionally, along with the recovery of hospitalized patients, we observed a matched reduction of CFD levels.CFD appears to be a potentially valuable marker for severity and follow-up of SII. We believe this rapid assay can help introduce the routine use of CFD measurement into daily practice.

Prevalence of Tuberculosis Risk Factors among Bacteriologically Negative and Bacteriologically Confirmed Tuberculosis Patients from Five Regional Referral Hospitals in Uganda

Understanding risk factors for tuberculosis (TB) and their prevalence helps guide early diagnosis. We determined their prevalence among bacteriologically negative and bacteriologically confirmed TB patients in five regional referral hospitals in Uganda. This cross-sectional study considered 1,862 adult presumptive TB participants. We performed fluorescent microscopy, Xpert MTB/RIF (Xpert), Lowenstein-Jensen culture, human immunodeficiency virus, and random blood sugar testing on recruited patients. Prevalence and prevalence ratios of risk factors were compared among bacteriologically negative and confirmed cases. Odds ratios and 95% confidence interval (CI) were determined for significant risk factors in bacteriologically confirmed patients. Of the 1,862 participants, 978 (55%) were male and the median age of the participants was 36 years (interquartile range: 27-48). Up to 273 (15%) had a positive result on all three TB tests. Most prevalent risk factors (prevalence ratio [PR] > 1.0) among bacteriologically negative and positive TB patients were cigarette smoking (9.3% versus 2.1%; PR = 2.1), biosmoke (24% versus 39.7%; PR = 1.7), contact (4.2% versus 6.5%; PR = 1.6), male gender (51.4% versus 72.5%; PR = 1.4), alcohol use (17.2% versus 24.4%; PR = 1.4), diabetes (0.7% versus 0.9%; PR = 1.3), and family history of TB (12.1% versus 13.7%; PR = 1.1). The risk factors and their adjusted prevalence rate ratios (95% CI) of being bacteriologically positive were male (1.8 [1.4-2.4]), biosmoke exposure (1.5 [1.2-2.0]), and history of cigarette smoking (1.6 [1.1-2.4]). Among bacteriologically confirmed patients in Uganda, cigarette smoking, biosmoke exposure, contact, male gender, alcohol use, diabetes, and family history of TB are important risk factors for TB. Interventions for TB control in people with these risk factors would help in TB control efforts.

Points & Pearls: Emergency department management of smoke inhalation injury in adults

Smoke inhalation injury portends increased morbidity and mortality in fire-exposed patients. Upper airway thermal burns, inflammation from lower airway irritants, and systemic effects of carbon monoxide and cyanide can contribute to injury. A standardized diagnostic protocol for inhalation injury is lacking, and management remains mostly supportive. Clinicians should maintain a high index of suspicion for concomitant traumatic injuries. Diagnosis is mostly clinical, aided by bronchoscopy and other supplementary tests. Treatment includes airway and respiratory support, lung protective ventilation, 100% oxygen or hyperbaric oxygen therapy for carbon monoxide poisoning, and hydroxocobalamin for cyanide toxicity. Due to its progressive nature, many patients with smoke inhalation injury warrant close monitoring for development of airway compromise. [Points & Pearls is a digest of Emergency Medicine Practice.].

Emergency department management of smoke inhalation injury in adults

Smoke inhalation injury portends increased morbidity and mortality in fire-exposed patients. Upper airway thermal burns, inflammation from lower airway irritants, and systemic effects of carbon monoxide and cyanide can contribute to injury. A standardized diagnostic protocol for inhalation injury is lacking, and management remains mostly supportive. Clinicians should maintain a high index of suspicion for concomitant traumatic injuries. Diagnosis is mostly clinical, aided by bronchoscopy and other supplementary tests. Treatment includes airway and respiratory support, lung protective ventilation, 100% oxygen or hyperbaric oxygen therapy for carbon monoxide poisoning, and hydroxocobalamin for cyanide toxicity. Due to its progressive nature, many patients with smoke inhalation injury warrant close monitoring for development of airway compromise.

Does inhalation injury predict mortality in burns patients or require redefinition?

Inhalation injury is known to be an important factor in predicting mortality in burns patients. However, the diagnosis is complicated by the heterogeneous presentation and inability to determine the severity of inhalation injury. The purpose of this study was to identify clinical features of inhalation injury that affect mortality and the values that could predict the outcome more precisely in burns patients with inhalation injury. This retrospective observational study included 676 burns patients who were over 18 years of age and hospitalized in the Burns Intensive Care Unit between January 2012 and December 2015. We analyzed variables that are already known to be prognostic factors (age, percentage of total body surface area (%TBSA) burned, and inhalation injury) and factors associated with inhalation injury (carboxyhemoglobin and PaO₂/FiO₂ [PF] ratio) by univariate and multivariate logistic regression. Age group (odds ratio [OR] 1.069, p<0.001), %TBSA burned (OR 1.100, p<0.001), and mechanical ventilation (OR 3.774, p<0.001) were identified to be significant predictive factors. The findings for presence of inhalation injury, PF ratio, and carboxyhemoglobin were not statistically significant in multivariate logistic regression. Being in the upper inhalation group, the lower inhalation group, and having a PF ratio <100 were identified to be significant predictors only in univariate logistic regression analysis (OR 4.438, p<0.001; OR 2.379, p<0.001; and OR 2.765, p<0.001, respectively). History and physical findings are not appropriate for diagnosis of inhalation injury and do not predict mortality. Mechanical ventilation should be recognized as a risk factor for mortality in burns patients with inhalation injury.

[Modern aspects of the conservation and promotion of health of firefighters]

On the basis of complex hygienic studies there were determined conditions of the work of firefighters in liquidation of foci of fires at the incipient stage, identified the complex of toxic substances, their quantitative content in the area of the smoke of fires. The analysis of the etiological role of occupational factors in the shaping of the morbidity and the physiological and clinical manifestations, established indices of the risk for occupational and industrial-caused pathology have allowed to substantiate the relationship of a number of nosological forms associated with working conditions of firefighters. There was developed a system of preventive activities for the promotion and preservation of the health of firefighters, as well as a conceptual model for monitoring of working conditions and state of health.

[Effects of two kinds of lung recruitment maneuvers on the correlated indexes of dogs with severe smoke inhalation injury]

OBJECTIVE

To observe and compare the effects of two kinds of lung recruitment maneuvers, namely sustained inflation (SI) and incremental positive end-expiratory pressure (PEEP) (IP) on oxygenation, respiratory mechanics, and hemodynamics of dogs with severe smoke inhalation injury.

METHODS

After being treated with conventional mechanical ventilation, 12 dogs were inflicted with severe smoke inhalation injury. They were divided into group SI and group IP according to the random number table, with 6 dogs in each group. Dogs in group SI were subjected to continuous positive airway pressure ventilation, with inspiratory pressure of 25 cmH2O (1 cmH2o = 0. 098 kPa), and it was sustained for 20 s. PEEP level in group IP was gradually increased by 5 cmH2O every 5 min up to 25 cmH2O, and then it was decreased by 5 cmH2O every 5 min until reaching 2-3 cmH2O. Then the previous ventilation mode was resumed in both groups for 8 hours. Blood gas analysis (pH value, PaO2, and PaCO2), oxygenation index (OI), respiratory mechanics parameters [peak inspiratory pressure (PIP), mean airway pressure, and dynamic lung compliance], and hemodynamic parameters [heart rate, mean arterial pressure (MAP), pulmonary arterial pressure (PAP), and cardiac output (CO)] were recorded or calculated before injury, immediately after injury, and at post ventilation hour (PVH) 2, 4, 6, 8. Data were processed with analysis of variance of repeated measurement and LSD-t test.

RESULTS

(1) At PVH 6 and 8, pH values of dogs in group SI were significantly lower than those in group IP (with t values respectively 2. 431 and 2. 261, P values below 0.05); PaO2 levels in group SI [(87 ± 24), (78 ± 14) mmHg, 1 mmHg =0. 133 kPa] were lower than those in group IP [ (114 ± 18) , (111 ± 17) mmHg, with t values respectively 2. 249 and 3.671, P <0.05 or P <0.01]; OI values in group SI were significantly higher than those in group IP (with t values respectively 2.363 and 5.010, P <0.05 or P <0.01). No significant differences were observed in PaCO2 level within each group or between the two groups (with t values from 0. 119 to 1. 042, P values above 0.05). Compared with those observed immediately after injury, the pH values were significantly lowered (except for dogs in group IP at PVH 6 and 8, with t values from 2.292 to 3.222, P <0.05 or P <0.01), PaO2 levels were significantly elevated (with t values from 4. 443 to 6.315, P <0.05 or P <0.01), and OI values were significantly lowered (with t values from 2.773 to 9.789, P <0.05 orP <0.01) in both groups at all the treatment time points. (2) The PIP level at each time point showed no significant differences between two groups (with t values from 0. 399 to 1. 167, P values above 0. 05). At PVH 4 and 8, the mean airway .pressure values of dogs in group SI were significantly higher than those in group IP (with t values respectively 1.926 and 1. 190, P values below 0.05). At PVH 4, 6, and 8, the dynamic lung compliance levels of dogs in group SI [(9.5 ± 1.9), (12.8 ± 2. 1), (13. 1 ± 1.8) mL/cmH2O] were significantly lower than those in group IP [(11.6 ± 1.2), (15.4 ± 1.8), (14.9 ± 0.8) mL/cmH2O], with t values respectively 2. 289, 2. 303, 2. 238, P values below 0.05. Compared with those observed immediately after injury, PIP and the mean airway pressure values of dogs in two groups were significantly lowered at each treatment time point (with t values from 2. 271 to 7. 436, P <0. 05 or P < 0.01); the dynamic lung compliance levels were significantly elevated in both groups at PVH 6 and 8 (with t values from 2. 207 to 4. 195, P < 0.05 or P <0.01). (3) Heart rate, MAP, and PAP levels at each time point between two groups showed no significant differences (with t values from 0. 001 to 1. 170, P values above 0. 05). At PVH 4, 6, and 8, CO levels in group IP [(0. 6 + 0. 3), (0. 6 + 0. 4), (0. 5 + 0. 7) L/min] were significantly lower than those in group SI [(1.5 0.7), (1.8 + 1.1), (1.6 +0.9) L/min], with t values respectively 3. 028, 2.511, 2.363, P values below 0.05. Compared with that observed immediately after injury, CO level in group IP was significantly lowered at PVH 4, 6, or 8 (with t values respectively 2. 363, 2. 302, 2. 254, P values below 0. 05).

CONCLUSIONS

Both lung recruitment maneuvers can effectively improve oxygenation and lung compliance of dogs with severe smoke inhalation injury. IP is more effective in improving lung compliance, while SI shows less impact on the hemodynamic parameters.

HEPBURN - investigating the efficacy and safety of nebulized heparin versus placebo in burn patients with inhalation trauma: study protocol for a multi-center randomized controlled trial

BACKGROUND

Pulmonary coagulopathy is a hallmark of lung injury following inhalation trauma. Locally applied heparin attenuates lung injury in animal models of smoke inhalation. Whether local treatment with heparin benefits patients with inhalation trauma is uncertain. The present trial aims at comparing a strategy using frequent nebulizations of heparin with standard care in intubated and ventilated burn patients with bronchoscopically confirmed inhalation trauma.

METHODS

The Randomized Controlled Trial Investigating the Efficacy and Safety of Nebulized HEParin versus Placebo in BURN Patients with Inhalation Trauma (HEPBURN) is an international multi-center, double-blind, placebo-controlled, two-arm study. One hundred and sixteen intubated and ventilated burn patients with confirmed inhalation trauma are randomized to nebulizations of heparin (the nebulized heparin strategy) or nebulizations of normal saline (the control strategy) every four hours for 14 days or until extubation, whichever comes first. The primary endpoint is the number of ventilator-free days, defined as days alive and breathing without assistance during the first 28 days, if the period of unassisted breathing lasts for at least 24 consecutive hours.

DISCUSSION

As far as the authors know, HEPBURN is the first randomized, placebo-controlled trial, powered to investigate whether local treatment with heparin shortens duration of ventilation of intubated and ventilated burn patients with inhalation trauma.

TRIAL REGISTRATION

NCT01773083 (http://www.clinicaltrials.gov), registered on 16 January 2013.Recruiting. Randomisation commenced on 1 January 2014.

[Effects of different position during high frequency oscillatory ventilation on oxygenation and hemodynamics of dogs with severe smoke inhalation injury]

OBJECTIVE

To study the effects of high frequency oscillatory ventilation (HFOV) with different position on oxygenation and hemodynamics of dogs with severe smoke inhalation injury.

METHODS

After being treated with conventional mechanical ventilation, 12 dogs were inflicted with severe smoke inhalation injury and treated by HFOV for 30 min. They were divided into HFOV+prone positioning (PP) group and HFOV+supine positioning (SP) group according to the random number table, with 6 dogs in each group. They received HFOV with corresponding position for 8 hours respectively.

RESULTS

of blood gas analysis (pH, PaO₂ and PaCO₂ levels), oxygen index (OI) and hemodynamic parameters [heart rate, mean arterial pressure (MAP), and cardiac output (CO)] were recorded or calculated before injury, immediately after injury, and at post ventilation hour (PVH) 2, 4, 6, 8. Data were processed with analysis of variance of repeated measurement, and LSD- t test.

RESULTS

(1) At PVH 8, pH value of dogs in group HFOV+PP was significantly higher than that in group HFOV+SP (t = 3.0571, P < 0.05). Compared with those observed immediately after injury, except for group HFOV+SP at PVH 2 and 4 (with t values respectively 2.066 5 and 1.440 7, P values all above 0.05), the pH values in both groups at other treatment time points were decreased (with t values from 2.449 5 to 3.985 3, P < 0.05 or P < 0.01). At PVH 2, 4, 8, the PaO₂ levels in group HFOV+PP [(131 ± 26), (150 ± 40), (112 ± 30) mmHg, 1 mmHg = 0.133 kPa] were higher than those in group HFOV+SP [(81 ± 15), (96 ± 5), (83 ± 6) mmHg, with t values from 2.366 4 to 4.083 5, P < 0.05 or P < 0.01]. The PaO₂ levels in both groups from PVH 2 to PVH 8 were increased, compared with those observed immediately after injury [(55 ± 15) mmHg in group HFOV+SP and (48 ± 11) mmHg in group HFOV+PP, with t values from 2.473 6 to 7.2310, P < 0.05 or P < 0.01]. No statistically significant differences were observed in PaCO₂ level at each time point between two groups (with t values from 0.661 0 to 2.141 9, P values all above 0.05). No statistically significant differences were observed in PaCO₂ levels from PVH 2 to PVH 8 compared with those observed immediately after injury in both groups (with t values from 0.126 2 to 1.768 3, P values all above 0.05). (2) The OI values in group HFOV+SP were significantly higher than those in group HFOV+PP from PVH 2 to PVH 8 (with t values from 3.091 9 to 3.791 6, P < 0.05 or P < 0.01). The OI values in both groups from PVH 2 to PVH 8 were significantly decreased, compared with those observed immediately after injury (with t values from 2.702 0 to 5.969 3, P < 0.05 or P < 0.01). (3) At PVH 6 and PVH 8, heart rate in group HFOV+PP was significantly higher than that in group HFOV+SP (with t values respectively 4.255 9 and 4.765 9, P values both below 0.01). Compared with that observed immediately after injury, heart rate in group HFOV+PP was significantly decreased (with t values from 3.006 2 to 5.135 5, P < 0.05 or P < 0.01) except for PVH 2 (t = 1.938 2, P > 0.05). However, there was no statistical significant difference at each treatment time point in group HFOV+PP (with t values from 0.786 5 to 1.525 8, P values all above 0.05). There was no statistically significant difference in MAP between two groups at each time point (with t values from 0.045 8 to 1.783 4, P values all above 0.05). Compared with that observed immediately after injury, MAP in group HFOV+SP was significantly decreased at PVH 8 (t = 2.368 3, P < 0.05); MAP in group HFOV+PP was significantly decreased at PVH 2 (t = 3.580 1, P < 0.01). At PVH 2 and 4, the CO values in group HFOV+SP were significantly higher than those in group HFOV+PP (with t values respectively 2.310 3 and 4.526 5, P values both below 0.01). Except for group HFOV+SP at PVH 2 (t = 1.294 1, P > 0.05), CO values at other treatment time points in both groups were significantly lower than that observed immediately after injury (with t values from 2.247 0 to 4.067 8, P < 0.05 or P < 0.01).

CONCLUSIONS

HFOV+ PP can improve oxygenation with no obvious CO₂ retention or adverse effect on hemodynamic parameters of dogs with severe smoke inhalation injury. Therefore, it is recommended for clinical application.

Occupational exposures and symptoms among firefighters and police during the carmel forest fire: the Carmel cohort study

BACKGROUND

From 2 to 5 December 2010, Israel experienced the most severe forest fire In its history, resulting in the deaths of rescue workers. Little research exists on the health risks to emergency responders during forest fires, and there is no published research to date on occupational health among firefighters in Israel.

OBJECTIVES

To describe the exposures experienced by emer gency responders to smoke, fire retardants and stress; the utilization of protective equipment; and the frequency of corresponding symptoms during and following the Carmel Forest fire.

METHODS

A cohort of 204 firfighers and 68 police who took part in rescue and fire-abating activites during the Carmel Forest fire were recruited from a representative sample of participating stations throughout the country and interviewed regarding their activities during the fire and their coinciding symptoms. Unpaired two-sample t-test compared mean exposures and symptom frequency for firefighters and police. Chi-square estimates of OR and 95%CI are provided for odds of reporting symptoms, incurring injury or being hospitalied for various risk factors

RESULTS

Of the study participants, 87% reported having at least one symptom during rescue work at the Carmel Forest fire,with eye irritation (77%) and fatigue (71%) being the most comon. Occupational stress was extremely high during the fire; the average length of time working without rest was 18.4 hours among firefighters.

CONCLUSION

Firefighter and police were exposed to smoke and ocupational stress prolonged periods during the fire. Further research is needed on the residual health effects from exposure to forest fires among emergency responders, and to identify areas for improvement in health preparedness.

The novel peptide PACAP-TAT with enhanced traversing ability attenuates the severe lung injury induced by repeated smoke inhalation

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a potential therapeutic peptide with anti-inflammatory and anti-oxidative effects. In order to increase the efficiency of traversing biological barriers, a novel fusion peptide PACAP-TAT was produced by tagging PACAP at its C-terminus with 11-amino acid TAT protein transduction domain. The results of characteristic assays showed that PACAP-TAT activated PACAP specific receptor PAC1 with the same potency as PACAP and PACAP-TAT crossed blood-brain barrier (BBB), blood-air barrier (BAB) and blood-testis barrier (BTB) with the efficiency about 2.5-fold higher than that of PACAP. Both PACAP-TAT and PACAP were used treat the mice with lung injury induced by repeated smoke inhalation. It was shown that both PACAP-TAT and PACAP decreased the mortality, increased the body weight and inhibited the edema and vascular permeability in the lungs of the mice received repeated smoke inhalation, while PACAP-TAT displayed more marked effects than PACAP. PACAP-TAT decreased myeloperoxidase (MPO) activity, increased catalase (CAT) activity and down-regulated interleukin 6 (IL-6) and malondialdehyde (MDA) levels in the lungs with a significantly higher efficiency than PACAP. The histopathological analysis also showed that PACAP-TAT attenuated the cell filtration and bronchi epithelial hyperplasia more significantly than PACAP. Moreover the leukocyte count in blood and the serum superoxide dismutase (SOD) activity in the mice treated with PACAP-TAT were significantly different from that in mice treated with PACAP (p<0.05). All these data indicated that PACAP-TAT with increased traversing ability was more effective than PACAP in protecting the mice from the lung injury induced by repeated smoke inhalation.

Pulmonary microvascular hyperpermeability and expression of vascular endothelial growth factor in smoke inhalation- and pneumonia-induced acute lung injury

INTRODUCTION

Acute lung injury (ALI) and sepsis are major contributors to the morbidity and mortality of critically ill patients. The current study was designed further evaluate the mechanism of pulmonary vascular hyperpermeability in sheep with these injuries.

METHODS

Sheep were randomized to a sham-injured control group (n=6) or ALI/sepsis group (n=7). The sheep in the ALI/sepsis group received inhalation injury followed by instillation of Pseudomonas aeruginosa into the lungs. These groups were monitored for 24 h. Additional sheep (n=16) received the injury and lung tissue was harvested at different time points to measure lung wet/dry weight ratio, vascular endothelial growth factor (VEGF) mRNA and protein expression as well as 3-nitrotyrosine protein expression in lung homogenates.

RESULTS

The injury induced severe deterioration in pulmonary gas exchange, increases in lung lymph flow and protein content, and lung water content (P<0.01 each). These alterations were associated with elevated lung and plasma nitrite/nitrate concentrations, increased tracheal blood flow, and enhanced VEGF mRNA and protein expression in lung tissue as well as enhanced 3-nitrotyrosine protein expression (P<0.05 each).

CONCLUSIONS

This study describes the time course of pulmonary microvascular hyperpermeability in a clinical relevant large animal model and may improve the experimental design of future studies.

Acute respiratory effects in firefighters

BACKGROUND

Associations between acute respiratory inflammatory responses, changes in bronchial hyperresponsiveness, serum pneumoprotein levels, and exposure to fire smoke were studied.

METHODS

The study comprised 51 firefighters. Blood samples were taken within 24 hr following exposure to fire smoke, and after a week and 3 months. Sputum was induced within 5 days post-exposure and subjects underwent spirometry and methacholine provocation one week post-exposure. Exposure was registered by a questionnaire.

RESULTS

No changes were observed following smoke exposure in bronchial hyperresponsiveness and serum pneumoprotein levels. Nevertheless, in a sizable proportion of the firefighters (44%) elevated sputum neutrophil levels (≥60%) were found. Serum IL-8 concentrations were higher 24 hr post-exposure compared to pre-exposure. Elevated neutrophil levels in sputum were associated with elevated serum IL-8 (β = 0.010, P = 0.004) and TNFα (β = 0.005, P = 0.034) levels within 24 hr post-exposure and IL-8 elevation lasted up to 3 months.

CONCLUSIONS

Acute exposure to fire smoke induces acute neutrophilic airway and long-lasting systemic inflammation in healthy firefighters in the absence of bronchial hyperresponsiveness.

Malondialdehyde and superoxide dismutase correlate with FEV(1) in patients with COPD associated with wood smoke exposure and tobacco smoking

Tobacco smoking is the primary risk factor for chronic obstructive pulmonary disease (COPD). However, recent epidemiological studies have established domestic exposure to wood smoke and other biomass fuels as additional important risk factors, characteristic in developing countries. Oxidative stress is one of the mechanisms concerned with pathogenesis of COPD. However, the molecular mechanisms involved in the onset and progress of COPD associated with biomass and specifically that derived from wood smoke exposure remain unknown. We analyzed the relationship between forced expiratory volume in first second (FEV(1)) with plasma malondialdehyde (MDA) concentration and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST) in COPD patients associated with wood smoke (WSG; n = 30), tobacco smoking (TSG; n = 30), and healthy control subjects (HCG; n = 30). Differences between FEV(1) from WSG and TSG (58 +/- 22% and 51 +/- 24%, respectively) with HCG (100 +/- 6%) were observed (P < 0.01). Plasma MDA concentration was higher in both WSG and TSG (1.87 +/- 0.81 and 1.68 +/- 0.82 nmol/mL, respectively) compared with HCG (0.42 +/- 0.17 nmol/mL; P < 0.01). SOD activity showed a significant increase in both WSG and TSG (0.36 +/- 0.12 and 0.37 +/- 0.13 U/mL) compared with HCG (0.19 +/- 0.04 U/mL; P < 0.01). No differences were shown regarding GPx, GR, and GST activities between COPD and control groups. Inverse correlations were founded between MDA and SOD with FEV(1) in both COPD patients and control subjects (P < 0.001). These results indicate a role for oxidative stress in COPD associated with wood smoke similar to that observed with tobacco smoking in subjects who ceased at least 10 years previous to this study.

Sclerosis therapy of bronchial artery attenuates acute lung injury induced by burn and smoke inhalation injury in ovine model

INTRODUCTION

In burned sheep, we showed more than a 10-fold increase in bronchial blood flow following smoke inhalation. It was previously reported that sclerosis of the bronchial artery prior to smoke exposure reduces the pathophysiology of the inhalation insult. We hypothesized that sclerosis of the bronchial artery after insult attenuates smoke/burn-induced acute lung injury.

METHODS

Through an incision at the 4th intercostal space, a catheter was placed via the esophageal artery into the bronchial artery such that the bronchial blood flow remained intact. Acute lung injury was induced by a 40% total body surface area, 3rd degree cutaneous burn and smoke inhalation. Adult female sheep (n=18, 35.6±1.0 kg) were divided into three groups following the injury: (1) sclerosis group: 1h after injury, 4 mL of 70% ethanol was injected into bronchial artery via bronchial catheter, n=6; (2) control group: 1h after injury, an equal dose of saline was injected into bronchial artery via the bronchial catheter, n=6; (3) sham group: no injury and no treatment, n=6. The experiment was conducted in awake animals for 24 h.

RESULTS

Bronchial blood flow, measured by microspheres, was significantly reduced after ethanol injection in the sclerosis group. Pulmonary function, evaluated by measurement of blood gas analysis, pulmonary mechanics, and pulmonary transvascular fluid flux, was severely impaired in the control group. However, pulmonary function was significantly improved by bronchial artery sclerosis.

CONCLUSION

The results of our study clearly demonstrate a crucial role of enhanced bronchial circulation in thermal injury-related morbidity. Decreasing bronchial circulation using pharmacological agents may be an effective strategy in management of burn patients with concomitant smoke inhalation injury.

Management of acute smoke inhalation injury

Pulmonary injury from smoke inhalation is common in burn victims, significantly contributing to the morbidity and mortality of fire-related injuries. The impacts of improvement in other aspects of burn care have not been mirrored in treatment of smoke inhalation. Smoke is heterogeneous and unique to each fire; it comprises particulates, respiratory irritants and systemic toxins as well as heat, all contributing to the pathological insult. Thermal injury below the vocal cords is rare because of effective heat dissipation in the upper airway. Particulate matter is the chief contributor to the pathophysiology of smoke inhalation injury, which has been extensively described. Of paramount importance is the cascade of inflammatory mediators following interaction of irritant substances with lung parenchyma, leading to pulmonary oedema, cast formation, airway obstruction, loss of hypoxic pulmonary vasoconstriction and ventilation/perfusion mismatch. Current treatment is based on supportive care, with airway management, mechanical ventilation, humidification and aggressive airway toilet the mainstays. Nebulisation of n2-agonists, heparin and N-acetylcysteine have a role in management, as does more specific treatment of carbon monoxide or cyanide intoxication. Many promising treatments are currently under investigation. The therapeutic strategy of decontaminating the lungs early after smoke exposure to prevent inhalation injury has received little attention and may be of significant value. This could potentially utilise amphoteric, hypertonic chelating agents developed for topical and ocular chemical exposures.

Role of calcitonin gene-related peptide (CGRP) in ovine burn and smoke inhalation injury

Concomitant smoke inhalation trauma in burn patients is a serious medical problem. Previous investigations in our sheep model revealed that these injuries lead to significant airway hyperemia, enhanced pulmonary fluid extravasation, and severely impaired pulmonary function. However, the pathophysiological mechanisms are still not fully understood. The lung is innervated by sensory nerves containing peptides such as substance P and calcitonin gene-related peptide. Noxious stimuli in the airways can induce a neurogenic inflammatory response, which has previously been implicated in several airway diseases. Calcitonin gene-related peptide is known to be a potent vasodilator. We hypothesized that calcitonin gene-related peptide is also a mediator of the pulmonary reaction to toxic smoke and planned experiments to evaluate its role in this model. We tested the effects of pretreatment with a specific antagonist of the major receptor for calcitonin gene-related peptide (BIBN4096BS; 32 microg/kg, followed by continuous infusion of 6.4 microg.kg(-1).h(-1)) until the animal was killed 48 h after injury in an established ovine model of burn (40% total body surface, third degree) and smoke inhalation (48 breaths, <40 degrees C) injury. In treated animals (n = 7), the injury-related increases in tracheal blood flow and lung lymph flow were significantly attenuated compared with untreated controls (n = 5). Furthermore, the treatment significantly attenuated abnormalities in respiratory gas exchange. The data suggest that calcitonin gene-related peptide contributes to early airway hyperemia, transvascular fluid flux, and respiratory malfunction following ovine burn and smoke inhalation injury. Future studies will be needed to clarify the potential therapeutic benefit for patients with this injury.

gamma-Tocopherol nebulization by a lipid aerosolization device improves pulmonary function in sheep with burn and smoke inhalation injury

Fire accident victims who sustain both thermal injury to skin and smoke inhalation have gross evidence of systemic and pulmonary oxidant damage and acute lung injury. We hypothesized that gamma-tocopherol (gT), a reactive O(2) and N(2) scavenger, when delivered into the airway, would attenuate lung injury induced by burn and smoke inhalation. Acute lung injury was induced in chronically prepared, anesthetized sheep by 40% total burn surface area, third-degree skin burn and smoke insufflation (48 breaths of cotton smoke, <40 degrees C). The study groups were: (1) Sham (not injured, flaxseed oil (FO)-nebulized, n=6); (2) SA-neb (injured, saline-nebulized, n=6); (3) FO-neb (injured, FO-nebulized, n=6); and (4) gT+FO-neb (injured, gT and FO-nebulized, n=6). Nebulization was started 1 h postinjury, and 24 ml of FO with or without gT (51 mg/ml) was delivered into airways over 47 h using our newly developed lipid aerosolization device (droplet size: 2.5-5 microm). The burn- and smoke inhalation-induced pathological changes seen in the saline group were attenuated by FO nebulization; gT addition further improved pulmonary function. Pulmonary gT delivery along with a FO source may be a novel effective treatment strategy in management of patients with acute lung injury.

Translational systems biology: introduction of an engineering approach to the pathophysiology of the burn patient

The pathophysiology of the burn patient manifests the full spectrum of the complexity of the inflammatory response. In the acute phase, inflammation may have negative effects via capillary leak, the propagation of inhalation injury, and development of multiple organ failure. Attempts to mediate these processes remain a central subject of burn care research. Conversely, inflammation is a necessary prologue and component in the later stage processes of wound healing. Despite the volume of information concerning the cellular and molecular processes involved in inflammation, there exists a significant gap between the knowledge of mechanistic pathophysiology and the development of effective clinical therapeutic regimens. Translational systems biology (TSB) is the application of dynamic mathematical modeling and certain engineering principles to biological systems to integrate mechanism with phenomenon and, importantly, to revise clinical practice. This study will review the existing applications of TSB in the areas of inflammation and wound healing, relate them to specific areas of interest to the burn community, and present an integrated framework that links TSB with traditional burn research.

L-arginine attenuates acute lung injury after smoke inhalation and burn injury in sheep

Thermal injury results in reduced plasma levels of arginine (Arg). With reduced Arg availability, NOS produces superoxide instead of NO. We hypothesized that Arg supplementation after burn and smoke inhalation (B + S) injury would attenuate the acute insult to the lungs and, thus, protect pulmonary function. Seventeen Suffolk ewes (n = 17) were randomly divided into three groups: (1) sham injury group (n = 6), (2) B + S injury plus saline treatment (n = 6), and (3) B + S injury plus L-ARG infusion at 57 mg.kg(-1).h(-1) (n = 5). Burn and smoke inhalation injury was induced by standardized procedures, including a 40% area full thickness flame burn combined with 48 breaths of smoke from burning cottons. All animals were immediately resuscitated by Ringer solution and supported by mechanical ventilation for 48 h, during which various variables of pulmonary function were monitored. The results demonstrated that Arg treatment attenuated the decline of plasma Arg concentration after B + S injury. A higher plasma Arg concentration was associated with a less decline in Pao2/Fio2 ratio and a reduced extent of airway obstruction after B + S injury. Histopathological examinations also indicated a remarkably reduced histopathological scores associated with B + S injury. Nitrotyrosine stain in lung tissue was positive after B + S injury, but was significantly reduced in the group with Arg. Therefore, L-Arg supplementation improved gas exchange and pulmonary function in ovine after B + S injury via its, at least in part, effect on reduction of oxidative stress through the peroxynitrite pathway.

Late consequences of respiratory system burns

Burn inhalation has negative effects on pulmonary function and may result in whole airway damage. The consequences of a methane explosion are thermal injury of the respiratory tract, shock wave, and carbon monoxide intoxication. The aim of this study was to determine changes in the pulmonary function tests (PFTs) after six years of follow-up in miners who survived a methane explosion. Two groups were examined: 41 miners who fell victims to a methane explosion and had a documented thermal injury of the respiratory tract and 25 healthy miners who served as controls. Pulmonary function studies were repeated after six months and six years from the time of injury in 33 study subjects and at the same time intervals in 16 control subjects. The study included static and dynamic lung volumes and diffusing capacity for carbon monoxide (DLCO). The mean values of PFTs were within normal ranges in both groups examined six months and six years after the injury. A significant decrease in DLCO was observed in the victims (98.4% vs. 85.4%), but not in the control group, after a six years' observation. The decrease may be one of the reasons for a breathing discomfort emerging in these patients. In the control subjects we observed a significant decrease in FEV1 (96.4% vs. 83.4%)--over a six years' period. This finding is due likely to smoking and heavy pollution of the working environment.

Ceftazidime improves hemodynamics and oxygenation in ovine smoke inhalation injury and septic shock

OBJECTIVE

To investigate ceftazidime in acute lung injury (ALI) and sepsis.

DESIGN AND SETTING

Prospective, randomized, controlled animal study in an investigational ICU at a university hospital.

INTERVENTIONS

Eighteen female Merino sheep were prepared for chronic study and subjected to smoke inhalation and septic challenge according to an established protocol.

MEASUREMENTS AND RESULTS

Whereas global hemodynamics and oxygenation remained stable in sham animals (no injury, no treatment), the injury contributed to a hypotensive-hyperdynamic circulation in the control group (smoke inhalation and sepsis, no treatment), as indicated by a significant increase in cardiac index) and heart rate and a drop in mean arterial pressure. Treatment with ceftazidime (smoke inhalation and sepsis, treatment group) stabilized cardiac index and heart rate and attenuated the decrease in mean arterial pressure. The deterioration in PaO2/FiO2 ratio and pulmonary shunt fraction (Qs/Qt) was significantly delayed and blunted by ceftazidime. At 24 h after injury a significant increase in airway obstruction scores of bronchi and bronchioles in both injured groups was observed. Ceftazidime significantly reduced airway obstruction vs. control animals. Whereas plasma nitrate/nitrite levels increased similarly in the two injured groups, lung 3-nitrotyrosine content remained at the baseline level in the ceftazidime group.

CONCLUSIONS

In ovine lung injury ceftazidime improves global hemodynamics and oxygenation not only by bacterial clearance but also via reduction in toxic nitrogen species such as 3-nitrotyrosine. Therefore ceftazidime appears as a clinically relevant adjunct in the common setting of sepsis-associated lung injury.

Effect of ablated airway blood flow on systemic and pulmonary microvascular permeability after smoke inhalation in sheep

The bronchial circulation plays a significant role in the pathogenesis of smoke inhalation. We investigated the physiological manifestations in both the systemic and the pulmonary circulation after smoke inhalation injury, and determined whether ablation of the bronchial circulation had any effect on these changes. We used a chronically instrumented ovine model with lung and prefemoral lymph fistulae to determine the changes in pulmonary and systemic microvascular permeability. Fourteen animals were divided into two groups. The injection group had bronchial circulation ablation with an ethanol injection into the bronchial artery, whereas it was left intact in the sham group. The sham group showed a four-fold increase in lung lymph flow (l-Q(L)) and a two-fold increase in prefemoral lymph flow (s-Q(L)) 24 h after injury. The increase in s-Q(L) was associated with a decrease in lymph oncotic pressure. Therefore, systemic colloid clearance (s-CC), an indicator of systemic microvascular permeability to protein, was unchanged. The ablated bronchial circulation reversed the pulmonary but not the systemic manifestations after smoke inhalation. In conclusion, the pathophysiological events occurring after smoke inhalation were confined to the lung with increased bronchial blood flow delivering inflammatory mediators directly to the lung parenchyma.

[Pathophysiology of the lung inhalation injuries]

<zakljucak> U ovom radu prikazani su neki od patofizioloskih aspekata inhalacionih povreda pluca, nezavisno od toga da li su bile udruzene s opekotinama ili nisu. Mada tacan mehanizam akutne inhalacione povrede pluca nije razjasnjen u potpunosti, na osnovu mnogobrojnih istrazivanja moze se zakljuciti da ogromnu ulogu u tim procesima imaju NO, PARP i opstrukcija vazdusnih puteva.

Isolated smoke inhalation injuries: Acute respiratory dysfunction, clinical outcomes, and short-term evolution of pulmonary functions with the effects of steroids

Relatively few reports exist regarding isolated smoke inhalation injuries in human patients. In this study, we describe the acute manifestations and short-term evolution of respiratory injuries after isolated smoke inhalation in victims of fires. Ninety-six patients admitted as the result of a subway fire were examined for acute respiratory dysfunction with clinical outcomes. Some of the survivors suffering from less severe injuries were evaluated for changes in pulmonary function over time, with the effects of steroid treatment. In 13 patients (14%), immediate respiratory failure resulted from ventilatory insufficiency, which was induced principally by mechanical airway obstruction, and manifested as significantly lowered pH and higher PaCO2 levels than in the patients requiring no mechanical ventilation. Toilet bronchoscopy allowed for early liberation from mechanical ventilation. Along with the death of 4 patients (4%), vocal cord and tracheal stenosis were noted in 5 patients and 1 patient, respectively, among 17 patients for whom endotracheal intubation was required. Pulmonary functions improved significantly after 3 months, with no further changes being observed within the subsequent 3 months. Steroid therapy resulted in no additional improvements in the pulmonary functions of these patients. In patients with isolated smoke inhalation injuries, immediate ventilatory insufficiency resulting from mechanical airway obstruction should be watched for, and managed via toilet bronchoscopy. Vigilance is required to avoid airway complications after endotracheal intubation. The improvement of pulmonary functions progressed primarily within the first 3 months, whereas short-course steroid therapy exerted no influence on the eventual recovery of pulmonary functions in the less severe cases.

Transient myocardial dysfunction after smoke inhalation

Acute onset, transient (reversible) myocardial contraction abnormality has been described in patients with acute non-cardiac illness and after acute emotional stress. Such reversible myocardial contraction abnormalities may occur via mechanisms other than reduction in epicardial coronary blood flow. We report a case of acute transient cardiomyopathy after smoke exposure. The patient developed acute heart failure without evidence of carbon monoxide poisoning that resolved within 4 days. An association between brief smoke exposure without carbon monoxide poisoning and acute heart failure has not been previously described.

Effects of severe smoke inhalation injury and septic shock on global hemodynamics and microvascular blood flow in sheep

This prospective, randomized, controlled experimental study looks at the effects on global and regional microvascular blood flow (RMBF) in an ovine model of septic shock after severe smoke inhalation injury. Sixteen sheep were randomized into two groups, a control group (no injury, n = 8) and a smoke/sepsis (SS) group (n = 8), which received an insufflation of 4 sets of 12 breaths of cotton smoke (<40 degrees C) followed by instillation of live Pseudomonas aeruginosa into both lung lobes, according to an established protocol. All sheep were mechanically ventilated with 100% oxygen, and fluid resuscitated with lactated Ringer's solution for the entire duration of the 24-h experimental period to maintain hematocrit at baseline (BL) levels. Healthy control animals were not subjected to the injury and received only 4 x 12 breaths of room air and instillation of the vehicle (normal saline). Blood flow was analyzed using colored microspheres. Control animals remained hemodynamically stable and had no statistical changes from BL in visceral or cerebral blood flow during the entire experimental period. All SS animals developed a hypotensive, hyperdynamic circulation, characterized by a significant increase in heart rate and cardiac output with a simultaneous significant fall in mean arterial pressure, which, in combination, led to a fall in systemic vascular resistance index versus BL (P < 0.001, each). In visceral organs, the trachea showed a significant increase in RMBF (P < 0.001). In addition, skeletal muscle significantly increased versus BL and versus controls over time (P < 0.01). Whereas the pancreas displayed a significant drop in RMBF versus BL and controls (P < 0.05), no statistical differences occurred in the renal cortex, spleen, and ileum. All investigated cerebral structures, such as the cortex cerebri, basal ganglia, thalamus, hippocampus, pons, medulla oblongata, and cerebellum showed a significant increase in RMBF versus BL and versus control animals (P < 0.05, each). These data differ in areas of normal, increased, and decreased RMBF during septic shock after smoke inhalation injury and show differences to former studies of our group investigating RMBF in ovine models of either smoke inhalation or P. aeruginosa infusion. The results of this study reflect the complex pathophysiological variances of the combined injury and may provide a basis for future investigations for the treatment of this kind of injury.

Prehospital administration of hydroxocobalamin for smoke inhalation-associated cyanide poisoning: 8 years of experience in the Paris Fire Brigade

INTRODUCTION

This article reports the results of a retrospective study of 8 years of experience of the Paris Fire Brigade with the prehospital use of hydroxocobalamin.

METHODS

The head physician at the Paris Fire Brigade extracted and summarized data from standardized forms completed at the fire scene and, when available, hospital reports to assess survival status and clinical parameters associated with the use of hydroxocobalamin for each patient who received it for smoke inhalation-associated cyanide poisoning from 1995 to 2003.

RESULTS

Of the 101 patients administered hydroxocobalamin, 30 survived, 42 died (17 at the fire scene and 25 at the intensive-care unit), and survival status was not known in the remaining 29 patients. Among the 72 patients for whom survival status was known, survival rate was 41.7% after the administration of hydroxocobalamin. Of the 38 patients found in cardiac arrest, 21 had a return of spontaneous circulation during prehospital care. Of the 12 patients who were initially hemodynamically unstable (systolic blood pressure 0 to < or =90 mmHg), 9 recovered systolic blood pressure an average of 30.6 minutes after the start of hydroxocobalamin infusion. Among nonsedated patients in the sample as a whole (n = 52), mean (SD) Glasgow coma scale score improved from 7.9 (5.4) initially to 8.5 (5.7) after administration of hydroxocobalamin. Among nonsedated patients who were initially neurologically impaired (n = 18), Glasgow coma scale score improved in 9 patients, did not change in 8 patients, and worsened in 1 patient. Two adverse events--red or pink coloration of urine or skin (n = 5) and cutaneous rash (n = 1)--were assessed as being possibly related to hydroxocobalamin.

CONCLUSION

Hydroxocobalamin has a risk:benefit ratio rendering it suitable for prehospital use in the management of acute cyanide poisoning caused by smoke inhalation.

Fire and smoke injuries

The successful management of burns and related injuries requires a comprehensive team approach at a designated burn center. This team should consist of burn surgeons, burn nurses, respiratory therapists, physical therapists, occupational therapists, clinical nutritionists, social workers, chaplains, and other clinical consultants. This article focuses specifically on the management of thermal burns and inhalational injuries, with an emphasis on assessment, resuscitation, and critical care management. It also discusses special considerations related to burned trauma patients.

Vitamin E attenuates acute lung injury in sheep with burn and smoke inhalation injury

INTRODUCTION

A decrease in alpha-tocopherol (vitamin E) plasma levels in burn patients is typically associated with increased mortality. We hypothesized that vitamin E supplementation (alpha-tocopherol) would attenuate acute lung injury induced by burn and smoke inhalation injury.

MATERIALS AND METHODS

Under deep anesthesia, sheep (33 +/- 5 kg) were subjected to a flame burn (40% total body surface area, third degree) and inhalation injury (48 breaths of cotton smoke, < 40 degrees C). Half of the injured group received alpha-tocopherol (1000 IU vitamin E) orally, 24 h prior to injury. The sham group was neither injured nor given vitamin E. All three groups (n = 5 per group) were resuscitated with Ringer's lactate solution (4 ml/kg/%burn/24 h), and placed on a ventilator (PEEP = 5 cmH2O; tidal volume = 15 ml/kg) for 48 h.

RESULTS

Plasma alpha-tocopherol per lipids doubled in the vitamin E treated sheep. Vitamin E treatment prior to injury largely prevented the increase in pulmonary permeability index and moderated the increase in lung lymph flow (52.6 +/- 6.2 ml/min, compared with 27.3 +/- 6.0 ml/min, respectively), increased the PaO2/FiO2 ratio, ameliorated both peak and pause airway pressure increases, and decreased plasma conjugated dienes and nitrotyrosine.

CONCLUSIONS

Pretreatment with vitamin E ameliorated the acute lung injury caused by burn and smoke inhalation exposure.

Atrial natriuretic peptide release associated with smoke inhalation and physiological responses to thermal injury in sheep

Markedly elevated levels of plasma atrial natriuretic peptide (ANP), which exhibit potent diuretic and vasoactive properties, has been well documented in patients with acute lung injury. We examined the physiological effects of additional smoke inhalation on plasma ANP concentrations in an ovine burn model. Seventeen sheep were instrumented to receive fluid and have physiological measurements taken. The burn group (n=8) received 40% body surface area third degree burn and the burn+smoke group (n=9) received the same burn plus 48 breaths of cotton smoke insufflation. The animals were resuscitated according to the Parkland formula with Ringer's lactate in the following 72 h period. Hemodynamic, oxygenation, fluid balance, and plasma ANP levels were serially determined. The effects of smoke inhalation manifested as deteriorated oxygenation, and increased fluid accumulation after a sustained initial shock period of more than 12 h. Plasma ANP levels in the burn+smoke group showed a biphasic elevation, whereas the burn group showed no appreciable changes throughout the whole experimental period. The initial increase in plasma ANP concentrations occurred immediately after injury (from 96+/-10 at baseline to 136+/-17 pg/mL at 3h after injury); thereafter, it decreased towards baseline value, followed by a second increase in the post resuscitation period (183+/-43 pg/mL at 72 h after injury). Decreased urine output and accentuated pulmonary vascular resistance in the combined injury group was observed between the two ANP level peaks, indicating that ANP release modified physiological responses to the burn+smoke injury.

Experimental wood smoke exposure in humans

Experimental studies are used to evaluate effects of human exposure to diesel exhaust and concentrated ambient particles. This article describes a system for studying exposure of humans to wood smoke. Wood smoke was generated using a wood stove placed outside an exposure chamber that can hold at least 10 subjects. A partial flow of the generated wood smoke from the stove was mixed with filtered indoor air. Personal and stationary measurements were performed of PM2.5 and PM1 mass concentrations and various volatile organic compounds (VOCs): 1,3-butadiene, benzene, and aldehydes. In addition, particulate matter (PM) mass, number concentrations, and size distributions of particles (0.007-6.7 microm), as well as nitrous oxides, CO2, and CO, were measured online. Filters were analyzed for trace elements and black smoke. Polycyclic aromatic compounds, toluene, and xylenes were determined in stationary samples. Results of the first experiment showed no differences between personal and stationary measurements for particles or VOCs. Consequently, stationary measurements can be used to predict personal exposure. All PM mass (about 250 microg/m3) was in the PM1 fraction. Subjective symptoms were generally weak, while clear objective signs were found, for example, in biomarkers of inflammation. With careful control of the combustion process, relatively constant mass and number concentrations were obtained over each exposure session. By varying the combustion and dilution of the wood smoke, different exposure scenarios can be achieved and thus, knowledge about which of the properties of particles and gaseous compounds are crucial for the effects.

Lung injury from smoke inhalation

Significant morbidity and mortality from smoke inhalation occurs in victims of fire. Lung injury can be caused by chemical and thermal insults. A variety of noxious gases, irritants and asphyxiants are generated depending on the material burnt. Carbon monoxide is the predominant cause of death among fire victims. Treatment should be directed at reversing hypoxaemia as a result of asphyxia or carbon monoxide poisoning. There is no evidence that the routine use of corticosteroids or prophylactic antibiotics is beneficial. Through a better understanding of the pathophysiology of smoke-induced lung injury, the effects of exogenous surfactant, leukotriene inhibitors, antioxidants, nitric oxide synthase inhibitors and fibrinolytics suggest that these compounds may have a future therapeutic role in smoke-induced injury. Studies are needed to evaluate the safety and efficacy of these potential therapies before they are used clinically.

Combined burn and smoke inhalation injury impairs ovine hypoxic pulmonary vasoconstriction

OBJECTIVE

To examine the effects of combined burn and smoke inhalation injury on hypoxic pulmonary vasoconstriction, 3-nitrotyrosine formation, and respiratory function in adult sheep.

DESIGN

Prospective, placebo-controlled, randomized, single-blinded trial.

SETTING

University research laboratory.

SUBJECTS

Twelve chronically instrumented ewes.

INTERVENTIONS

Following a baseline measurement, sheep were randomly allocated to either healthy controls (sham) or the injury group, subjected to a 40%, third-degree body surface area burn and 48 breaths of cotton smoke according to an established protocol (n = 6 each). Hypoxic pulmonary vasoconstriction was assessed as changes in pulmonary arterial blood flow (corrected for changes in cardiac index) in response to left lung hypoxic challenges performed at baseline and at 24 and 48 hrs postinjury.

MEASUREMENTS AND MAIN RESULTS

Combined burn and smoke inhalation was associated with increased expression of inducible nitric oxide (NO) synthase, elevated NO2/NO3 (NOx) plasma levels (12 hrs, sham, 6.2 +/- 0.6; injury, 16 +/- 1.6 micromol.L; p < .01) and increased peroxynitrite formation, as indicated by augmented lung tissue 3-nitrotyrosine content (30 +/- 3 vs. 216 +/- 8 nM; p < .001). These biochemical changes occurred in parallel with pulmonary shunting, progressive decreases in Pao2/Fio2 ratio, and a loss of hypoxic pulmonary vasoconstriction (48 hrs, -90.5% vs. baseline; p < .001). Histopathology revealed pulmonary edema and airway obstruction as the morphologic correlates of the deterioration in gas exchange and the increases in airway pressures.

CONCLUSIONS

This study provides evidence for a severe impairment of hypoxic pulmonary vasoconstriction following combined burn and smoke inhalation injury. In addition to airway obstruction, the loss of hypoxic pulmonary vasoconstriction may help to explain why blood gases are within physiologic ranges for a certain time postinjury and then suddenly deteriorate.

Lung inflammation in rats following subchronic exposure to cigarette mainstream smoke

Female Sprague-Dawley rats were exposed to mainstream smoke from standard reference cigarettes and a nontobacco cellulose cigarette for 35 days. Whole smoke and smoke fractions were investigated. Lung inflammation was evaluated by differentiation of bronchoalveolar lavage cells and lymphocytes in thoracic lymph nodes. Histopathological changes in the nose and larynx were assessed. Results showed that the particulate phase of cigarette mainstream smoke is mostly responsible for inflammation in the lung (neutrophil increase up to 240-fold) and hyperplastic and metaplastic epithelial changes in the larynx, whereas irritative volatile constituents in the gas phase are mostly responsible for changes in the nose.

Effect of smoke inhalation on viscoelastic properties and ventilation distribution in sheep

Smoke inhalation injuries are the leading cause of mortality from burn injury. Airway obstruction due to mucus plugging and bronchoconstriction can cause severe ventilation inhomogeneity and worsen hypoxia. Studies describing changes of viscoelastic characteristics of the lung after smoke inhalation are missing. We present results of a new smoke inhalation device in sheep and describe pathophysiological changes after smoke exposure. Fifteen female Merino ewes were anesthetized and intubated. Baseline data using electrical impedance tomography and multiple-breath inert-gas washout were obtained by measuring ventilation distribution, functional residual capacity, lung clearance index, dynamic compliance, and stress index. Ten sheep were exposed to standardized cotton smoke insufflations and five sheep to sham smoke insufflations. Measured carboxyhemoglobin before inhalation was 3.87 +/- 0.28% and 5 min after smoke was 61.5 +/- 2.1%, range 50-69.4% (P < 0.001). Two hours after smoke functional residual capacity decreased from 1,773 +/- 226 to 1,006 +/- 129 ml and lung clearance index increased from 10.4 +/- 0.4 to 14.2 +/- 0.9. Dynamic compliance decreased from 56.6 +/- 5.5 to 32.8 +/- 3.2 ml/cmH(2)O. Stress index increased from 0.994 +/- 0.009 to 1.081 +/- 0.011 (P < 0.01) (all means +/- SE, P < 0.05). Electrical impedance tomography showed a shift of ventilation from the dependent to the independent lung after smoke exposure. No significant change was seen in the sham group. Smoke inhalation caused immediate onset in pulmonary dysfunction and significant ventilation inhomogeneity. The smoke inhalation device as presented may be useful for interventional studies.

Effect of inhaled nitric oxide on pulmonary vascular hyperpermeability in sheep following smoke inhalation

Smoke inhalation increases mortality and morbidity in burn patients. We have reported that smoke inhalation increases lung lymph flow, an index of pulmonary transvascular fluid flux and decreases reflection coefficient, an index of microvascular permeability to protein. Nitric oxide has been reported to decrease microvascular permeability to protein. We hypothesize that inhaled nitric oxide decreases pulmonary microvascular hyperpermeability following smoke inhalation. Sheep were prepared for study with a chronic lung lymph fistula, Swan-Ganz, left atrial, and femoral arterial catheters. Occluders were placed on pulmonary veins to measure reflection coefficient. All animals were insufflated with 4 x 12 breaths of cotton smoke. Sheep were randomly divided into two groups: NO (injured, treated with nitric oxide (40 ppm) inhalation, n=6) and control (injured, not treated, n=6). Nitric oxide inhalation was started 22 h after the insult. Control animals showed an increase in lung lymph flow, and lung water content. These changes were associated with marked increase in pulmonary microvascular resistance, pulmonary artery pressure, and decrease in reflection coefficient. Nitric oxide inhalation ameliorated the above-mentioned pathological changes. The results suggest that nitric oxide inhalation has potential for beneficial effect in the treatment of patients suffering from smoke inhalation.

Selective thromboxane A2 synthase inhibition by OKY-046 prevents cardiopulmonary dysfunction after ovine smoke inhalation injury

BACKGROUND

Because thromboxane A2 is implicated in the pathophysiology of acute lung injury, the aim of this study was to evaluate the effects of selective thromboxane A2 synthase inhibition on cardiopulmonary function in the experimental setting of severe smoke inhalation injury.

METHODS

Sixteen adult sheep were operatively instrumented for chronic study. The injured intervention group was treated with the selective thromboxane A2 synthase inhibitor OKY-046, whereas the injured control group received only the vehicle (n = 8 each).

RESULTS

The progressive increase in thromboxane B2 lung lymph concentrations in control animals was associated with increased transvascular fluid flux, augmented resistances in the pulmonary and systemic circulation, and a reciprocal decrease in cardiac output. In addition, end-systolic pressure-diameter relation and maximum +dp/dt were markedly depressed as compared with baseline (24 h: 14.3 +/- 0.9 vs. 8.9 +/- 0.5 mmHg/mm and 2,120 +/- 50 vs. 1,915 +/- 40 mmHg/s, respectively; each P < 0.05). Infusion of OKY-046 significantly inhibited pulmonary thromboxane B2 delivery, attenuated the early increase in pulmonary vascular resistance, and blocked the increase in systemic vascular resistance. In addition, OKY-046 blunted and delayed the decrease in cardiac output and maintained end-systolic pressure-diameter relation, +dp/dt, and lung lymph flow at baseline values.

CONCLUSIONS

These findings suggest that selective thromboxane A2 synthase inhibition may represent a goal-directed therapeutic approach to alleviate cardiovascular and pulmonary dysfunction in the setting of smoke inhalation injury.

Skin nitric oxide and its metabolites are increased in nonburned skin after thermal injuries

Local and systemic inflammation can lead to progression of burn wounds, converting second- to third-degree wounds or extending the burn to adjacent areas. Previous studies have suggested that the skin is an important site of production of nitric oxide (NO), synthesized by inducible nitric oxide synthase (iNOS) activation after injury. NO increases in burned wounds, but its formation in noninjured skin has not been investigated. We hypothesized that after severe burns, NO and cytotoxic peroxynitrite would increase in noninjured skin. We also tested the hypothesis that BBS-2, a specific inhibitor of iNOS, would impair NO formation after burn. Thirteen female sheep were randomized into burn injury and smoke inhalation (n = 5, group 1), burn and smoke treated with BBS-2 (n = 3, group 2), and sham (saline treatment, no injury) (n = 5, group 3). All the animals, including the sham-injury group, were mechanically ventilated for 48 h. Samples of nonburned skin and plasma were collected from each animal, and levels of NO and its metabolites were evaluated using a NO chemiluminescent detector. Nitrotyrosine and iNOS expression were determined in the skin by Immunoperoxidase staining, and scoring of masked slides (epidermis, hair follicles, vessels, glands, and stroma) was performed. Skin NO and metabolites significantly increased in the burn and smoke injury group, and this was inhibited by BBS-2. Nitrotyrosine expression also increased significantly in the skin of burned animals. BBS-2 prevented the increase of NOx but not the increase of nitrotyrosine expression in skin. Plasma levels of NO increased in burned animals when compared with sham, but this increase was not significant. The increase of NO and its metabolites after burn in noninjured skin is followed by a significant increase in peroxynitrite, a potent cytotoxic mediator.

In vivo effect of wood smoke on the expression of two mucin genes in rat airways

A short-term, time-dependent smoke exposure of rats in a nose-only chamber to burning wood and 24-h recovery time revealed inflammation of the airways with varying degrees of injury from loss of cilia, degeneration of epithelium, and squamous metaplasia to submucosal edema. These histological changes were reflected in variable expression of the secretory Muc5AC and low expression of membrane-associated Muc4 mucin genes. 20-min smoke exposure in extended recovery experiments showed marked disorder of tracheal epithelium for up to 72 h of recovery with a return to normal by 7 days. Gene expressions were elevated at 24 and 48 h of recovery. 30-min smoke exposure showed a more severe degeneration of the epithelium and a longer recovery time. Muc5AC expression decreased after 72 h of recovery, while there was upregulation of Muc4 gene from 48 through 96 h. Because Muc4 upregulation and histological results correlate and it has reportedly been associated with epithelium renewal, Muc4 gene may be a useful marker for the regeneration of tracheal epithelium.

Pathophysiology of acute lung injury in combined burn and smoke inhalation injury

In the U.S.A., more than 1 million burn injuries occur every year. Although the survival from burn injury has increased in recent years with the development of effective fluid resuscitation management and early surgical excision of burned tissue, the mortality of burn injury is still high. In these fire victims, progressive pulmonary failure and cardiovascular dysfunction are important determinants of morbidity and mortality. The morbidity and mortality increases when burn injury is associated with smoke inhalation. In the present review, we will describe the pathophysiological aspects of acute lung injury induced by combined burn and smoke inhalation and examine various therapeutic approaches.

The effects of inhaled nitric oxide on cardiac pathology and energy metabolism in a canine model of smoke inhalation injury

OBJECTIVE

The effects of inhaled nitric oxide (NO) on cardiac pathology and energy metabolism were studied in a canine model of smoke inhalation injury.

MATERIAL AND METHOD

Twenty-one dogs were randomly divided into three groups: four dogs constituted the normal control group (group N), eight dogs subjected to smoke inhalation followed by O(2) inhalation (FiO(2)=0.45) constituted the injury control group (group C), and nine dogs inhaling a mixture of O(2) and 45ppm nitric oxide after smoke exposure served as the treatment group (group T). Myocardial zymograms were continuously measured, and ventricular muscles were examined for histopathology in the end of the experiment.

RESULTS

Lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (alpha-HBD), creatine kinase (CK) and glutamic oxalacetic transaminase (GOT) in group T were less than those in group C(P<0.05, or P<0.01). ATP content and energy charge (EC) in group T were higher significantly than those in group C(P<0.01). Light microscopy and electron microscopy indicated that the ventricular pathologic changes in group T were milder than in control group.

CONCLUSION

Nitric oxide inhalation relieved myocardial damage and improved energy metabolism.