Thromboxane receptor blockade with BM 13,177 following toxic airway damage by smoke inhalation in sheep

Thromboxane may play an important role in the pathogenesis of smoked mediated injury. We studied this possibility in 13 chronically instrumented sheep, which had the left lung exposed to smoke. BM 13,177, a thromboxane receptor antagonist, was given intravenously to six animals prior to smoke inhalation and during the experimental period. Seven animals received the vehicle. All animals were studied for 24 h under ventilatory support, then killed prior to harvesting lung tissue. Airway peak and plateau pressures in the vehicle-treated animals were elevated by 27% and 25% from baseline at 24 h post smoke inhalation. Concomitantly, the left pulmonary vascular resistance index rose continuously throughout the study period (baseline = 822 +/- 58; 24 h = 1819 +/- 84 dyn.s.cm-5.m2).BM 13,177 treatment completely prevented the rise in airway pressure, while the left pulmonary vascular resistance index was significantly attenuated (baseline = 726 +/- 79; 24 h = 1470 +/- 158 dyn.s.cm-5.m2) resulting in a significantly higher percentage of cardiac output being delivered to the smoked lung, compared to vehicle-treated animals. Thromboxane receptor blockade did not prevent smoke induced pulmonary edema formation. There was likewise no effect of BM 13,177 on the systemic hemodynamic changes seen following smoke inhalation. There was a decrease in cardiac index and an increase in systemic vascular resistance index in both groups. We conclude that smoke induced changes in airway and pulmonary vascular resistances may be mediated by thromboxanes. However, thromboxanes appear to play no role in the development of pulmonary edema and elevation of systemic vascular resistance following smoke inhalation injury.

Inhalation injury

Inhalation injury remains a primary determinant of patient survival, with 60% to 70% of burn center fatalities attributed to the pulmonary complications of inhalation injury. Substantial airway damage and pulmonary complications can result from the inhalation of toxic fumes and gases found in smoke. Partial to complete airway obstruction, pulmonary edema, pneumonia, and progressive pulmonary failure may occur. Early diagnosis of inhalation injury and vigorous pulmonary care and support are vitally important to patient survival. Bronchoscopy and xenon 133 ventilation-perfusion scans are two of the newer diagnostic tools used to identify burn patients with inhalation injury. Treatment measures for patients with inhalation injury and recommendations for nursing practice are discussed.

Pathophysiology of ovine smoke inhalation injury treated with extracorporeal membrane oxygenation

An ovine model was used to study the pathophysiology of smoke inhalation injury treated with extracorporeal membrane oxygenation (ECMO). Smoke inhalation is characterized by leukocyte-oxygen free-radical mediated acute lung injury. Treatment with ECMO was by extracorporeal venoarterial or venovenous perfusion using a venous drainage reservoir, roller pump, heat exchanger, and membrane lung oxygenator capable of oxygen delivery to and carbon dioxide removal from a patient. Blood-foreign surface interactions are known to occur during ECMO. We examined the effects of ECMO on circulating leukocytes, oxygen free-radical activity, thromboxane release, and gas exchange after smoke inhalation injury. Animals treated with smoke and ECMO had significantly increased circulating thromboxane B2 levels and oxygen free-radical activity compared with sham-treated animals and animals treated with smoke and mechanical ventilation (MV). Likewise, there was a significant increase in lung wet-to-dry weight ratios in animals treated with smoke and ECMO compared with those treated with smoke and MV. These data may account for the initial deterioration in native lung function after the initiation of ECMO and imply that ECMO may potentiate the pathophysiology of smoke inhalation injury.

Heparin improves oxygenation and minimizes barotrauma after severe smoke inhalation in an ovine model

Inhalation injury is one of the main causes of mortality in burn victims. The tracheobronchial epithelium sloughs and combines with a protein rich exudate to form casts of the airways that can lead to obstruction. We studied the effects of a continuous infusion of heparin on the acute pulmonary injury that occurs after smoke inhalation injury in sheep. Twelve ewes with vascular catheters received a standardized smoke inhalation injury and mechanical ventilation according to protocol for 72 hours. The heparin group (n = 6) received a 400 unit per kilogram bolus of heparin followed by a continuous infusion to maintain the activated clotting time between 250 to 300 seconds. The control group (n = 6) received a saline solution vehicle. Hemodynamics, blood gases and plasma samples for conjugated dienes were taken every six hours. At necropsy, pulmonary tissue was collected for histologic findings, polymorphonuclear neutrophil leukosequestration, wet-to-dry weight ratios and conjugated dienes. PaO2 to FIO2 ratios were improved in the heparin group compared with the control group at 12 to 72 hours after injury, and peak airway pressures were higher in the control group compared with the heparin group. Positive end expiratory pressure requirements were higher in the control group compared with the heparin group. There were significantly fewer airway tracheobronchial casts as determined by our tracheobronchial casts scoring system (2.4 +/- 0.4 versus 0.67 +/- 0.21) and confirmed by histologic examination. Pulmonary blood-free wet-to-dry weight ratios were higher in the control group compared with the heparin group (6.4 +/- 0.5 versus 5.2 +/- 0.1; p < 0.05). There were no differences in pulmonary tissue or plasma conjugated dienes; likewise, pulmonary leukosequestration was unaffected by heparin. Heparin decreases tracheobronchial cast formation, improves oxygenation, minimizes barotrauma and reduces pulmonary edema in an ovine model of severe smoke inhalation injury. Heparin does not reduce oxygen free radical activity after smoke inhalation injury.

A rabbit model of inhalation injury

In the course of developing a model of inhalation injury, the relationship between the severity of pulmonary injury and specific techniques and doses of smoke exposure was examined in pairs of rabbits simultaneously exposed to smoke. In group I (5 pairs), one animal in each pair was exposed to smoke with a breath hold (BH) at the end of each exposure; the second animal received an exposure producing the same level of carboxyhemoglobin without BH. In group II (6 pairs), both animals were exposed to 25 units of smoke simultaneously, with BH. In group III (3 pairs), one animal received a 20-unit exposure and the other a 25-unit exposure, both with BH. In group IV, 9 animals received 25-unit exposures with BH and were observed for 4 days. Groups V and VI served as controls. Smoke exposure with BH regularly produced severe injury in terms of decreased PaO2 and histopathologic changes, while exposure without BH did not, despite high levels of carboxyhemoglobin after smoke inhalation. The mean differences in percent residual PaO2 (PaO2 at 48 hours x 100/pre-injury PaO2) and in extravascular lung water (EVLW) at 48 hours within pairs of animals receiving 25 units with BH were 12.3% +/- 5.33%, and 0.271 +/- 0.157 mL/g, respectively. Histologic findings such as necrotic tracheobronchitis with pseudomembrane were consistently present. No differences were observed between animals receiving exposure of 20 and 25 units. During the 4 days of observation, three animals in group IV died. PaO2 was lowest on the second day and rose thereafter in all surviving animals except in one that had massive pneumonia.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial translocation after thermal injury

OBJECTIVES

To review the mechanisms responsible for bacterial translocation after thermal injury. Areas investigated were the rate of bacterial translocation, blood flow to the gastrointestinal tract, potential of reversibility of mesenteric vasoconstriction, specific vasomediators responsible for postburn mesenteric vasoconstriction, potential reversal of gut mucosal atrophy with decreased translocation, and evidence of gut mucosal damage after thermal injury.

DESIGN

Using three different animal models consisting of rats, sheep, and minipigs, the objectives were defined. Using the sheep model, the relationship of decreased mesenteric blood flow after thermal injury was defined along with rates of translocation, and the potential reversibility of the postburn mesenteric vasoconstriction and its effect on translocation. The effect of smoke inhalation and the combination of thermal injury and inhalation injury on rates of translocation are explained. Using minipigs, the role that thromboxane A2 plays on the postburn mesenteric vasoconstriction was defined by blocking thromboxane A2 synthesis with OKY046, a specific thromboxane synthetase inhibitor. Evidence of gut mucosal injury was determined using ornithine decarboxylase as an indicator of gut mucosal damage and subsequent repair in the minipig model. The rat model was used to demonstrate gut mucosal atrophy after thermal injury and the potential for reversal of atrophy with the use of bombesin, a specific gut mucosal growth stimulator.

RESULTS

After thermal injury, there were significant decreases in mesenteric blood flow. There was also an increase in bacterial translocation. Selective infusion of nitroprusside into the cephalic mesenteric artery prevented the post-burn mesenteric vasoconstriction and attenuated bacterial translocation. Smoke inhalation and smoke inhalation with thermal injury resulted in mesenteric vasoconstriction and increased rates of bacterial translocation. OKY046 infusion prevented the postburn increase in mesenteric vascular resistance. There were increased concentrations of ornithine decarboxylase within the colonic mucosa, indicating a previous injury and the presence of ongoing repair. Likewise, there was gut mucosal atrophy after thermal injury with bacterial translocation. Treating with bombesin attenuates the postburn mucosal atrophy and prevents bacterial translocation.

CONCLUSIONS

Thermal injury is associated with mesenteric vasoconstriction. This postburn mesenteric vasoconstriction results in damage to gut mucosa and allows for increases in bacterial translocation. The postburn mesenteric ischemia can be ameliorated with nitroprusside infusion, thus preventing translocation. Thromboxane A2 appears to be a major mediator of the postburn decrease in mesenteric blood flow. Likewise, prevention of postburn gut mucosal atrophy with bombesin attenuates bacterial translocation.

Pulmonary arterial hypertension and cor pulmonale associated with chronic domestic woodsmoke inhalation

We describe the clinical, radiologic, functional, and pulmonary hemodynamic characteristics of a group of 30 nonsmoking patients with a lung disease that may be related to intense, long-standing indoor wood-smoke exposure. The endoscopic and some of the pathologic findings are also presented. Intense and prolonged wood-smoke inhalation may produce a chronic pulmonary disease that is similar in many aspects to other forms of inorganic dust-exposure interstitial lung disease. It affects mostly country women in their 60s, and severe dyspnea and cough are the outstanding complaints. The chest roentgenograms show a diffuse, bilateral, reticulonodular pattern, combined with normalized or hyperinflated lungs, as well as indirect signs of pulmonary arterial hypertension (PAH). On the pulmonary function test the patients show a mixed restrictive-obstructive pattern with severe hypoxemia and variable degrees of hypercapnia. Endoscopic findings are those of acute and chronic bronchitis and intense anthracotic staining of the airways appears to be quite characteristic. Fibrous and inflammatory focal thickening of the alveolar septa as well as diffuse parenchymal anthracotic deposits are the most prominent pathologic findings, although inflammatory changes of the bronchial epithelium are also present. The patients had severe PAH in which, as in other chronic lung diseases, chronic alveolar hypoxia may play the main pathogenetic role. However, PAH in wood-smoke inhalation-associated lung disease (WSIALD) appears to be more severe than in other forms of interstitial lung disease and tobacco-related COPD. The patients we studied are a selected group and they may represent one end of the spectrum of the WSIALD.

Burn edema is accentuated by a moderate smoke inhalation injury in sheep

We determined the lung and systemic response of a moderate smoke inhalation injury combined with a 15% total body surface third-degree burn compared with a burn alone and inhalation alone. Adult sheep were prepared with chronic lung and bilateral prefemoral soft tissue lymph fistula. The burn was confined to one side. Physiologic parameters, lymph flow (QL), and lymph/plasma protein ratio were monitored. Oxidant changes were measured as lipid peroxidation by circulating and lymph-conjugated dienes and lung tissue malondialdehyde. Animals were resuscitated with lactated Ringer's solution during the 24-hour study period to restore and maintain vascular filling pressures and cardiac index. We found net 24-hour fluid balance for burn-inhalation injuries to be 4.1 +/- 1.2 L compared with burn alone of 2.9 +/- 0.9 L and inhalation alone of 2.4 +/- 0.5 L, a significant difference. Protein-rich burn tissue QL increased by fivefold to sixfold with burn alone compared with more than tenfold with burn-inhalation injury. A twofold increase in both lung and nonburn soft tissue QL was also seen in the combined injury not seen with burn alone. Arterial blood gases decreased only at 12 hours. Plasma conjugated dienes were increased in all groups, whereas burn lymph values were increased only in combined insult. In addition, lung malondialdehyde content at 24 hours was 155 +/- 11 nmol/gm with burn-inhalation injury compared with 62 +/- 8 nmol/L for burn alone, 55 +/- 9 nmol/L in inhalation alone, and 45 +/- 4 nmol/L for controls. However, no alveolar flooding was noted in any group. We conclude that a modest smoke inhalation (carboxyhemoglobin of 25%) added to a 15% total body surface burn markedly increases the degree of burn edema, as well as nonburn soft tissue and lung QL, compared with burn alone, indicating increased plasma to interstitial fluid transport in these tissues as well. Increased burn tissue lipid peroxidation products corresponded with the increased burn fluid losses. The increased lung lipid peroxidation also indicates further lung oxidant activity as well.

Morphologic changes in basal cells during repair of tracheal epithelium

Basal cells are differentiated with respect to junctional adhesion mechanisms and play a role in attachment of columnar epithelium to the basal lamina. Although much is known about nonciliated and ciliated cell differentiation during the repair process after injury, little is known about the basal cell. We studied the morphology of basal cells and quantitated junctional adhesion structures during repair of tracheal epithelium exposed to toxic cotton smoke. Ten adult ewes were given a smoke injury to a portion of the upper cervical trachea and were killed at 4, 6, 8, 10, and 18 days after injury for morphometric studies. At 4 days, there was a stratified reparative epithelium over the basal lamina, which was two to four cells in depth. The basal cells were identified by their hemidesmosome (HD) attachment to the basal lamina. Basal cells were about 69% larger than controls and flattened rather than columnar. The amount of HD attachment was 192% greater than controls. In contrast, volume density of cytokeratin filaments had decreased about 47%. Basal cells had returned to normal numbers and size and a columnar shape by day 18. The amount of desmosome (D) and HD attachment and volume density of cytokeratins had also reached control levels by day 18. These data indicate that morphology of basal cells changes during the initial stages of reparative regeneration but returns to normal by 18 days. Morphologic changes appear to reflect changes in size of the cell associated with cell division rather than differentiation of recently divided basal cells.

Mechanical alteration of blood flow in smoked and unsmoked lung areas after inhalation injury

The degree of pulmonary perfusion may have an important role in the pathogenesis of inhalation injury. We studied this in sheep that had only one lung exposed to smoke. The right lung and upper airway of 12 chronically instrumented sheep were insufflated with cotton smoke. In six animals, the left pulmonary artery was occluded between 4 and 10 h after smoke insufflation. All animals were studied for 24 h and then killed, and lung tissue was harvested. The smoked as well as the air-insufflated lung of all animals showed an increase in wet-to-dry weight ratio and tissue conjugated dienes (products of lipid peroxidation). Neither the intermittent blood flow increase to the smoked lung nor the simultaneous blood flow reduction with a concomitant polymorphonuclear neutrophil entrapment in the air-insufflated lung significantly affected the histopathological outcome of the respective lung. We conclude that tissue damage after inhalation injury cannot be diminished by increasing the flow to smoked areas. Ischemia-reperfusion injury does not have a major role in the lung damage seen with inhalation injury.

Oxygen consumption early postburn becomes oxygen delivery dependent with the addition of smoke inhalation injury

We determined the relationship between oxygen delivery, DO2, and oxygen consumption, VO2, in sheep after a moderate smoke inhalation injury and 15% TBSA third-degree burn compared with burn alone and controls. Comparison was made beginning three hours after injury when carboxyhemoglobin levels were back to baseline values. We decreased DO2 between three and eight hours by 25% by either removing blood (controls) or decreasing the resuscitation fluid infusion rate. Lung oxidant, measured as tissue malondialdehyde (MDA) levels, and histologic changes were also assessed. Animals were killed at 24 hours. We found that in controls and animals with a burn alone, a 25% decrease in DO2 was compensated for by an increase in O2 extraction, maintaining VO2 constant. Correlation of DO2 to VO2 was r2 = 0.3, indicating independence of VO2 from DO2. With the combined injury, VO2 decreased in proportion to DO2, since O2 extraction did not increase. The correlation of DO2 to VO2 was r2 = 0.9, indicating delivery-dependent consumption, a pathologic process most likely caused by increased inflammatory mediators from the combined injury. Lung lipid peroxidation was markedly increased in the combined injury, 148 +/- 18 nmol MDA/gram of tissue compared with burn alone, 64 +/- 5 nmol/g, or controls, 45 +/- 4 nmol/g. However, no decrease in arterial O2 tension or increase in lung water was noted, i.e., the sheep did not have ARDS, which is known to impair O2 extraction. We conclude that a pathologic O2 delivery-dependent consumption develops with the combination of burn and inhalation injury, increasing the potential for tissue hypoxemia. This change corresponds with increased lung tissue oxidant change.

The effect of dopamine on pulmonary hemodynamics and tissue damage after inhalation injury in an ovine model

Hypoxic pulmonary vasoconstriction and reduced blood flow occur as a result of smoke inhalation. The aim of this study was to investigate how the amelioration of blood flow reduction by the vasodilator dopamine affects histopathologic outcome. We exposed the left lungs of chronically instrumented sheep (n = 12) to smoke, awakened them, and studied them for 24 hours. Six hours after inhalation injury, the sheep received randomized infusions of dopamine (9 micrograms/kg/min) or equal volumes of 0.9% saline solution. Pulmonary resistance in the left lungs of animals in the group that received saline solution rose continuously throughout the study period (624 +/- 48 dyne.sec.cm-5/m2 to 1747 +/- 140 dyne.sec.cm-5/m2, baseline to 24 hours after injury). Dopamine treatment caused a significantly lower vascular resistance in the injured lung than did saline solution between 8 and 24 hours after injury. The histologic evaluation of the injured lungs showed epithelial necrosis and cast formation in both groups in addition to an increased wet/dry ratio. No difference in lung injury between the groups could be distinguished. We conclude that the amelioration of blood flow reduction by treatment with dopamine in the lungs that were exposed to smoke did not affect pulmonary damage after inhalation injury.

Smoke aldehyde component influences pulmonary edema

The pulmonary edema of smoke inhalation is caused by the toxins of smoke and not the heat. We investigated the potential of smoke consisting of carbon in combination with either acrolein or formaldehyde (both common components of smoke) to cause pulmonary edema in anesthetized sheep. Seven animals received acrolein smoke, seven animals received a low-dose formaldehyde smoke, and five animals received a high-dose formaldehyde smoke. Pulmonary arterial pressure, pulmonary capillary wedge pressure, and cardiac output were not affected by smoke in any group. Peak airway pressure increased after acrolein (14 +/- 1 to 21 +/- 2 mmHg; P less than 0.05) and after low- and high-dose formaldehyde (14 +/- 1 to 21 +/- 1 and 20 +/- 1 mmHg, respectively; both P less than 0.05). The partial pressure of O2 in arterial blood fell sharply after acrolein [219 +/- 29 to 86 +/- 9 (SE) Torr; P less than 0.05] but not after formaldehyde. Only acrolein resulted in a rise in lung lymph flow (6.5 +/- 2.2 to 17.9 +/- 2.6 ml/h; P less than 0.05). Lung lymph-to-plasma protein ratio was unchanged for all three groups, but clearance of lymph protein was increased after acrolein. After acrolein, the blood-free extravascular lung water-to-lung dry weight ratio was elevated (P less than 0.05) compared with both low- and high-dose formaldehyde groups (4.8 +/- 0.4 to 3.3 +/- 0.2 and 3.6 +/- 0.2, respectively). Lymph clearance (ng/h) of thromboxane B2, leukotriene B4, and the sulfidopeptide leukotrienes was elevated after acrolein but not formaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS)

Smoke inhalation: diagnosis and treatment

Smoke inhalation, defined as airway or pulmonary parenchymal injury resulting from the inhalation of toxic combustion products, presents with a wide range of severity in patients with and without skin burns. In patients with severe injuries, the diagnosis is obvious on the basis of the history and clinical presentation; in patients with less severe injuries or those in whom the clinical consequences are delayed, diagnostic precision is difficult because diagnostic clues provide only indirect information. There is no specific treatment so diagnosis is not critical for patient management. Patients at risk include 20% to 30% of flame burn victims who should receive vigorous supportive care. The mortality rate of smoke inhalation victims without a burn is < 10%. With a burn the mortality rate is 30% to 50%, suggesting that thermal injury or its treatment is responsible for further lung damage. Endotracheal intubation provides definitive treatment for obstructed or soon-to-be obstructed patients. However the diagnosis of smoke inhalation per se is not an indication for airway intubation and respiratory support; 12% of patients without a burn require intubation versus 62% of those with a burn. A translaryngeal tube can be converted to a tracheotomy safely in burn victims; tracheotomies are easier to manage if burns of the neck are excised and grafted prior to placement. Mechanical ventilation with positive end expiratory pressure (PEEP) is the treatment for the pulmonary injury. The early lesions of smoke inhalation often progress in the context of sepsis and other complications of the burn illness to a clinical state consistent with adult respiratory distress syndrome.

Oxidants and the pathophysiology of burn and smoke inhalation injury

A skin burn is a common traumatic injury that results in both local tissue damage and a systemic mediator-induced response. There is evidence of both local and systemic oxidant changes manifested by lipid peroxidation in animal burn models and also in burned man. Both increased xanthine oxidase and neutrophil activation appear to be the oxidant sources. Animal studies have also demonstrated decreased burn edema, and also decreased distant organ dysfunction with the use of antioxidants, suggesting a cause-and-effect relationship, which needs to be tested in man. Smoke inhalation injury, a chemical injury to the airways caused by incomplete products of combustion, is frequently seen in conjunction with a body burn. Lipid peroxidation, both in lung and in distant organs, is also seen with this injury. The combined body burn and smoke inhalation injury lead to a marked increase in mortality rate and also an increase in the degree of generalized oxidant release and lipid peroxidation. Although data in man are limited, the available information, along with that from animal research on burns and smoke inhalation, indicates oxidants may well play a key role, and antioxidants may be of clinical therapeutic use.

Thermal degradation events as health hazards: particle vs gas phase effects, mechanistic studies with particles

Exposure to thermal degradation products arising from fire or smoke could be a major concern for manned space missions. Severe acute lung damage has been reported in people after accidental exposure to fumes from plastic materials, and animal studies revealed the extremely high toxicity of freshly generated fumes whereas a decrease in toxicity of aged fumes has been found. This and the fact that toxicity of the freshly generated fumes can be prevented with filters raises the question whether the toxicity may be due to the particulate rather than the gas phase components of the thermodegradation products. Indeed, results from recent studies implicate ultrafine particles (particle diameter in the nm range) as potential severe pulmonary toxicants. We have conducted a number of in vivo (inhalation and instillation studies in rats) and in vitro studies to test the hypothesis that ultrafine particles possess an increased potential to injure the lung compared to larger-sized particles. We used as surrogate particles ultrafine TiO2 particles (12 and 20 nm diameter). Results in exposed rats showed that the ultrafine TiO2 particles not only induce a greater acute inflammatory reaction in the lung than larger-sized TiO2 particles, but can also lead to persistent chronic effects, as indicated by an adverse effect on alveolar macrophage mediated clearance function of particles. Release of mediators from alveolar macrophages during phagocytosis of the ultrafine particles and an increased access of the ultrafine particles to the pulmonary interstitium are likely factors contributing to their pulmonary toxicity. In vitro studies with lung cells (alveolar macrophages) showed, in addition, that ultrafine TiO2 particles have a greater potential to induce cytokines than larger-sized particles. We conclude from our present studies that ultrafine particles have a significant potential to injure the lung and that their occurrence in thermal degradation events can play a major role in the highly acute toxicity of fumes. Future studies will include adsorption of typical gas phase components (HCl, HF) on surrogate particles to differentiate between gas and particle phase effects and to perform mechanistic studies aimed at introducing therapeutic/preventive measures. These studies will be complemented by a comparison with actual thermal degradation products.

Long term effects of smoke inhalation in survivors of the King's Cross underground station fire

BACKGROUND

In most accidents causing smoke inhalation only a few victims actually inhale the smoke. The fire at King's Cross provided an opportunity to assess the long term effects of smoke inhalation in a larger number of patients.

METHODS

Fourteen survivors from the King's Cross underground station fire were assessed for respiratory disability six months after the disaster and 10 were reassessed at two years. All had inhaled substantial quantities of smoke and 10 had skin burns of differing severity.

RESULTS

Six months after the fire nine survivors admitted to one or more symptoms, which included hoarseness (two cases), cough (five cases), and breathlessness (six cases); and a survivor with asthma noted a worsening of his symptoms. The remaining five denied new symptoms. Peak expiratory flow, spirometric indices, and transfer factor for carbon monoxide were within the predicted normal ranges. The mean residual volume, however, was greater than the predicted value and the mean maximum expiratory flow at 25% of vital capacity (V25) less than predicted, with no significant differences between smokers (n = 7) and non-smokers (n = 7). At least one of these ventilatory defects, suggesting small airways obstruction, was present in 11 survivors at six months and they had persisted in the seven patients who were reassessed at two years.

CONCLUSION

Smoke inhalation may be associated with injury to the small airways.

Derived pulmonary capillary pressure changes after smoke inhalation in sheep

BACKGROUND AND METHODS

We determined derived pulmonary capillary pressure and the longitudinal distribution of pulmonary vascular resistance in chronically instrumented sheep with inhalation injury by using analysis of pressure decay curves after pulmonary artery occlusion.

RESULTS

There was an increase in derived pulmonary capillary pressure and an increase in the lung lymph flow after smoke inhalation. The pulmonary vascular, arterial, and venous resistances increased significantly in the inhalation group. Pulmonary venous resistance increased proportionately more than pulmonary arterial resistance in the inhalation group. The plasma osmotic pressure-derived pulmonary capillary pressure gradient decreased to a greater extent in the inhalation group than in the control group.

CONCLUSIONS

The present experiments suggest that the estimates of derived pulmonary capillary pressure can predict filtration pressure better than pulmonary artery occlusion pressure. The derived pulmonary capillary pressure can be measured easily in man with a pulmonary arterial catheter.

Alveolar macrophage chemotaxis in fire victims with smoke inhalation and burns injury

In vitro migration of alveolar macrophages was studied in 24 fire victims and 19 controls; all subjects were cigarette smokers. Unstimulated (P = 0.01) and stimulated migration towards casein-(P = 0.01) and zymosan-activated serum (P = 0.002) of macrophages from smoke inhalation patients (SI) (n = 19) was increased when compared to control subjects (CS). Migration of alveolar macrophages from patients with burns without smoke inhalation (burns only, BO) was not increased. Patients with smoke inhalation and no burns (smoke only, SO) (n = 9) had increased migration when compared to controls but this was not statistically significant. Patients with smoke inhalation and burns (SB) (n = 10) had increased unstimulated migration (P = 0.01) and increased migration towards casein (P less than 0.005), ZAS (P less than 0.002) and F-met-leu-phe (P less than 0.05) when compared to controls (CS). Lavage fluid from the fire victims displayed chemotactic activity towards normal human neutrophils and its analysis for the components of the complement cascade proved positive (Clq, Clr, Factor B and C3). These data suggest that activation of alveolar macrophages may contribute to the development of pathophysiological changes in patients with smoke inhalation (SI) and particularly those with smoke inhalation and burns (SB).

Analysis of pulmonary microvascular permeability after smoke inhalation

We estimated the reflection (sigma) and filtration coefficients (Kf) in a chronic sheep lung lymphatic preparation after smoke inhalation. Group I (n = 7) sheep were insufflated with cotton smoke and group II animals (n = 5) with room air. After inhalation injury, the lung lymph flow increased nearly four times the baseline value by 24 h after injury. There was a concomitant reduction of sigma (0.81 +/- 0.02 to 0.64 +/- 0.02) and elevation of Kf (0.020 +/- 0.002 to 0.042 +/- 0.009 ml.min-1.mmHg-1); pulmonary capillary pressure was also elevated (13 +/- 1 to 17 +/- 1 mmHg). By 48 h postinjury, sigma and Kf returned toward baseline but pulmonary capillary pressure was still elevated. We determined that 34% of the increase in capillary filtration was attributable to increased capillary pressure and 66% to increased permeability 24 h after inhalation, but 48 h after injury, 75% of the increase in capillary filtration was attributable to increased capillary pressure and 25% to increased permeability. We conclude that the lung edema formation following smoke inhalation is the result of marked increases in both capillary pressure and permeability.

Methylprednisolone does not protect the lung from inhalation injury

Most clinical studies suggest that corticosteroids are contraindicated in the treatment of acute smoke inhalation. However, they are still used in critical situations with the hope that they might reverse the acute pathophysiological responses to smoke inhalation and thus reduce the severity of the illness or make survival possible. These experiments were done to study the effect of methylprednisolone on the response to smoke inhalation in anaesthetized mongrel dogs. Three experimental protocols were followed: (I) haemodynamics, gas exchange, lung compliance, and lung water were evaluated; (II) pulmonary vascular permeability was assessed by cannulating the afferent tracheobronchial lymphatic and calculating the osmotic reflection coefficient (sigma d) at high lung lymph flows; (III) pulmonary surfactant function was studied using a Wilhelmy balance. Methylprednisolone alone did not alter any measured values compared with those seen in control animals. Treatment with methylprednisolone (30 mg/kg) prior to smoke exposure did not attenuate any of the adverse responses typically seen after smoke inhalation. These data indicate that methylprednisolone does not protect the lung from the acute physiological consequences of inhalation injury.

Lung edema formation following inhalation injury: role of the bronchial blood flow

We investigated the contribution of the bronchial blood flow to the lung lymph flow (QL) and lung edema formation after inhalation injury in sheep (n = 18). The animals were equally divided into three groups and chronically prepared by implantation of cardiopulmonary catheters and a flow probe on the common bronchial artery. Groups 1 and 2 sheep were insufflated with 48 breaths of cotton smoke while group 3 received only room air. Just before injury, the bronchial artery of group 2 animals was occluded. The occlusion was maintained for the duration of the 24-h study period. At the end of the investigation, samples of lung were taken for determination of blood-free wet weight-to-dry weight ratio (W/D). Inhalation injury induced a sevenfold increase in QL in group 1 (7 +/- 1 to 50 +/- 9 ml/h; P less than 0.05) but only a threefold increase in group 2 (10 +/- 2 to 28 +/- 7 ml/h; P less than 0.05). The mean W/D value of group 1 animals was 23% higher than that of group 2 (5.1 +/- 0.4 vs. 3.9 +/- 0.2; P less than 0.05). Our data suggest that the bronchial circulation contributes to edema formation in the lung that is often seen after the acute lung injury with smoke inhalation.

Tracheal venous blood and lymph collection: a model to study airway injury in sheep

Airway injury is a frequent result of the inhalation or aspiration of toxic material. Although upper airway damage can be identified endoscopically, pathophysiological changes are difficult to evaluate. This paper describes an animal model in which changes in tracheal blood and lymph flow rates, wet-to-dry weight ratios, and lymph-to-plasma protein ratios can be evaluated after injury. In this model, 12 cm of the cervical trachea were isolated using a double-cuffed endotracheal tube and injured with cotton smoke at near room temperature. Injury to the trachea was evaluated in twenty-five anesthetized sheep 4 (n = 3), 8 (n = 3), 24 (n = 3), 48 (n = 3), 96 (n = 3), and 192 (n = 2) h after smoke exposure and compared with sham control animals (n = 8). A significant increase in tracheal venous blood flow from 1.3 +/- 0.4 (SD) ml.min-1.cm-1 for the noninjured trachea to 2.8 +/- 1.2 was noted 24 h after injury (P less than 0.01). Lymph flow significantly increased from 1.3 +/- 0.4 microliters.min-1.cm-1 for the noninjured trachea to 9.8 +/- 3.3 24 h after injury while wet-to-dry weight ratios were elevated from 3.0 +/- 0.2 for noninjured trachea to 4.6 +/- 0.9 from 4 to 24 h after injury (P less than 0.01) and decreased to 3.7 +/- 0.5 by 96 h. Cast material consisting of airway exudate, cellular debris, and intact ciliated epithelial cells was both expectorated and found in the trachea when the animals were killed.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased airways reactivity after smoke inhalation

13 fire victims who required treatment after smoke inhalation underwent lung function assessment within 3 days of injury and 3 months later. Initial airways hyperreactivity improved over this period, but FEV1 and airways specific conductance did not change significantly. There was a strong correlation between exposure carboxyhaemoglobin concentration (an indicator of smoke exposure) and initial airways specific conductance (r + 0.79; p = 0.006). Airways obstruction after smoke inhalation in house fires may be more common and more persistent than is generally recognised. Early lung function tests would allow the incidence of pulmonary complications after smoke inhalation and the potential benefits of early use of inhaled antiinflammatory drugs to be assessed.

Pulmonary circulation and burns and trauma

The lung is a critical organ in victims of thermal injury or multiple trauma since the blood that drains injured organs circulates through the pulmonary circulation before passing through any other organ. The lung therefore will receive the first volley of cytotoxins released postinjury. In addition to being a target of injury, the lung may also contribute to the injury of systemic organs. This injury may be the result of a reduced delivery of oxygenated blood or the direct release of cytotoxins into the systemic circulation. The injury to the lung may be to the pulmonary microvasculature or the airway. The bronchial circulation responds to injury by a marked elevation in its blood flow and microvascular permeability. These latter effects may be important in mediating the changes which occur in the lung parenchyma.

[Effect of carbon monoxide on hemodynamics and oxygen metabolism in inhalation lung injury]

Chemical pneumonitis and carbon monoxide (CO) poisoning may be the etiologic factors in inhalation injury. Since the CO poisoning related with smoke inhalation has a much high mortality we tested the hypothesis that superimposed CO poisoning deteriorates hemodynamics and oxygen metabolism in acid inhalation injury. Ten anesthetized dogs were ventilated in room air to maintain normal PaCO2. Lung injury was produced with 2 ml/kg 0.1 N HCL intratracheally. Five dogs (ACID) were then ventilated with room air, while the others were exposed to 1% CO in air for 10 minutes to produce CO poisoning simultaneously with acid instillation (CO-ACID). Hemodynamic changes, oxygen metabolism and carboxyhemoglobin (COHb) were monitored for 4 hours. Thirty minutes following the challenge PaO2 in ACID and CO-ACID groups fell to 65 +/- 10 and 43 +/- 4 (p less than 0.05), respectively. Acid caused significantly decreased cardiac output and increased pulmonary vascular resistance. CO did not accentuate hemodynamic changes following acid inhalation. However, a significant increase of COHb in CO-ACID group resulted in deterioration of oxygen transportation. Though oxygen extraction increased markedly in both groups the oxygen consumption decreased significantly in CO-ACID group. A constantly depressed mixed venous oxygen tension in CO-ACID group suggests the deterioration of tissue oxygen metabolism.

Inhalation injuries

Inhalation injuries comprise three distinct clinical entities that may be classified according to the time of onset of symptoms, etiologic agents, and the anatomic location of injury. These entities are carbon monoxide toxicity, upper airway obstruction, and smoke inhalation or chemical injury. Each has a distinct pathophysiology, clinical manifestations, treatment, and prognosis. The emergency management of inhalation injury is frequently based on the health professional's degree of suspicion despite the availability of sophisticated diagnostic tests. Early aggressive treatment, including maintaining a patent airway, administering humidified oxygen and bronchodilators, and providing pulmonary toilet, is necessary to ensure the best possible outcome. Understanding the pathophysiology, clinical manifestations, diagnosis, medical management, and nursing implications of inhalation injuries can improve patient survival.

Intrapulmonary distribution of bronchial blood flow after moderate smoke inhalation

The systemic blood flow to the airways of the left lung was determined by the radioactive microsphere technique before and 17 h after smoke inhalation in six conscious sheep (smoke group) and six sheep insufflated with air alone (sham group). Smoke inhalation caused a sixfold increase in systemic blood flow to the lower trachea (baseline 10.6 +/- 1.7 vs. injury 60.9 +/- 16.1 ml.min-1.100 g-1) and an 11- to 14-fold increase to the intrapulmonary central airways (baseline range 9.5 +/- 1.9 to 13.5 +/- 3.7 ml.min-1.100 g-1 vs. injury 104.6 +/- 32.2 to 187.3 +/- 83.6 ml.min-1.100 g-1). There was a trend for this hyperemic response to be greater as airway diameter decreased from the trachea to 2-mm-diam central airways. In airways smaller than 2 mm, the hyperemic response appeared to diminish. The total systemic blood flow to whole lung is predominantly to small peripheral airways and showed no significant increase from its baseline level of 17.5 +/- 3.7 ml.min-1.100 g-1 in the lung homogenate. Occlusion of the bronchoesophageal artery decreased central airway blood flow 60-80% and peripheral airway blood flow 40-60% in both the sham and the smoke groups.

Bronchial blood flow reduction with positive end-expiratory pressure after acute lung injury in sheep

Smoke inhalation increases bronchial blood flow (Qbr) and produces edema of the airway system. This study investigates whether the increased Qbr seen 24 h after inhalation injury can be affected by mechanical ventilation with PEEP (5, 10, 15 cm H2O). Sheep (n = 8) previously prepared with cardiopulmonary catheters and ultrasonic transit time flow probes mounted around their bronchial arteries were insufflated with four sets of 12 breaths each of cotton smoke. Different levels of PEEP were added to the mechanical ventilation 24 h after injury; each PEEP level was applied for 45 min. There were significant increases in Qbr and lung lymph flow (QL) associated with a marked decrease in bronchial vascular resistance (BVR) 24 h after injury. However, no change was observed in mean arterial pressure (MAP) or cardiac index (CI). There was a substantial reduction in PaO2/FIO2 (P/F), which indicated a deterioration in arterial oxygenation. The application of varying levels of PEEP decreased Qbr (p less than .05) while BVR increased (p less than .05), but QL and P/F did not. CI and MAP were recorded. After removal of PEEP, none of the cardiopulmonary variables were significantly different from their postsmoke control values. These findings suggest that mechanical ventilation with PEEP markedly decreases the smoke-induced hyperemia edema frequently seen after inhalation injury without any significant alterations in MAP or CI.

Administration of a synthetic antiprotease reduces smoke-induced lung injury

Our previous studies suggest that a neutrophil-mediated inflammatory injury causes a major fraction of the pulmonary edema that occurs after smoke inhalation. Because activated neutrophils extrude cytotoxic proteases, the current study was conducted to evaluate the role of proteases in the pulmonary microvascular injury. Twelve sheep, instrumented for collection of lung lymph, were insufflated with cotton smoke. The sheep were treated 30 min after smoke inhalation with either gabexate mesilate (an inhibitor of serine proteases) or vehicle. Smoke inhalation resulted in an increased protease activity in the lung interstitium, as evidenced by decreases in both antiprotease activity and immunoreactive alpha 2-macroglobulin. Intravenous infusion of gabexate mesilate prevented the decrease in antiprotease activity. The protease inhibitor significantly attenuated the smoke-induced increase in transvascular fluid and protein flux, with untreated animals exhibiting 460% increases in flux compared with 180% in the inhibitor treated sheep. The protease inhibitor also eliminated the functional degradation in gas exchange that was observed in the untreated sheep. These studies strongly suggest that an increase in pulmonary proteolytic enzyme activity is responsible for a significant fraction of the degradation in microvascular integrity and gas exchange that is associated with smoke inhalation injury.

Experimental inhalation injury with concomitant surface burn: dextran resuscitation improves lung water and oxygenation

The role of extravascular lung water (EVLW) in the pathogenesis of inhalation injury (INH) when associated with concomitant major burn (B) remains controversial. Previous experimental models have investigated isolated INH without surface burn. This study measured the effects of isolated and combined INH on EVLW and pO2 in a porcine experimental model. The beneficial effects of early resuscitation with dextran-40 (DEX) were assessed, using a control group receiving standard Parkland formula (LR). In the first part of the study (INH vs. INH + B), a group of animals with a standardized INH was compared to a group also receiving a standardized 40% BSA third-degree surface burn (n = 8, each group). With serial measurements for 5 hours, EVLW was only modestly increased unless INH was accompanied by surface burn: 20.3 +/- 4.2 vs. 32.0 +/- 4.1 ml/kg at 5 hours (p less than 0.01). Similarly, pO2 fell much more dramatically in the INH + B group, 61 +/- 5 vs. 37 +/- 5 torr (p less than 0.05). The second part of the study compared standard Parkland crystalloid resuscitation with dextran-40 resuscitation in animals receiving a combined INH + B injury (LR vs. DEX, n = 8, each group). DEX resuscitation resulted in substantially lower accumulation of EVLW out to 5 hours, 34.1 +/- 5.0 vs. 13.1 +/- 3.0 ml/kg (p less than 0.01), and significantly better pO2, 35 +/- 5 vs. 64 +/- 4 torr (p less than 0.01).

CONCLUSIONS

Inhalation injury did not dramatically increase EVLW in this animal model unless accompanied by concomitant major surface burn. The deterioration in EVLW and pO2 seen in the combined injury was significantly improved with DEX resuscitation when compared to standard crystalloid resuscitation. Further study is indicated and clinical trials may be warranted.

Distribution of extravascular lung water after acute smoke inhalation

Anesthetized dogs with thoracotomy were injected with Evans blue dye and were exposed acutely (5 min) to wood smoke inhalation. Thin slices from freeze-dried samples were photographed and assessed for periarterial and perivenous cuff area and for blue coloration with a score of 0 to 5. Bloodless extravascular lung water (EVLW) was also measured. The smoke-exposed animals were compared with controls and with animals exposed to alloxan or to high-pressure-induced pulmonary edema. EVLW at 2 h after smoke (6.46 +/- 0.80) was above control value (4.30 +/- 0.63) but not different from the alloxan (6.13 +/- 0.70) or high-pressure (6.88 +/- 1.30) groups. Despite the similarity in EVLW in the edematous lungs, there were marked differences in the intensity of blue color and size of cuffing around arteries and veins: the smoke, alloxan, and high-pressure groups had blue color scores of 1.0 +/- 0.1, 2.9 +/- 0.3, and 0.3 +/- 0.1, respectively. These scores indicated a large increase in microvascular permeability to proteins in the alloxan group, a moderate increase in the smoke group, and minimal change in the high-pressure group. The perivascular cuff area was largest in the alloxan group and moderate in the smoke and high-pressure groups. The cuff area was higher for arteries than for veins in all groups except the 0.5-h smoke group. We conclude that smoke inhalation causes a moderate increase in permeability and EVLW compared with alloxan. The extravascular lung water accumulates preferentially around the arteries, but the size of the perivascular cuff is not similar for all causes of pulmonary edema.

A comparison of effects of thermal injury and smoke inhalation on bacterial translocation

Thermal injury as well as smoke inhalation injury results in serious morbidity and high mortality. In a chronic ovine model, we studied the development of bacterial translocation to the mesenteric lymph node, liver, spleen, kidney, and lung following: 1) sham injury (N = 6), 2) cutaneous thermal injury (N = 5), 3) cotton smoke inhalation injury (N = 4), 4) combined thermal injury and smoke inhalation injury (N = 7). Cardiac output, mean arterial pressure, and plasma protein concentration were maintained within 10% of preinjury values. Urine output was maintained above 1 ml/kg/hour with fluid and plasma resuscitation. A wide-beam ultrasonic flow probe was chronically implanted to allow serial measurement of cephalic mesenteric arterial blood flow throughout the 48-hour experimental period. Sheep were sacrificed 48 hours following injury for quantitative organ culture of mesenteric lymph node, liver, spleen, kidney, and lung. Measurements of mesenteric blood flow demonstrated a decrease to 48 +/- 8%, 80 +/- 5%, and 64 +/- 9% of preinjury levels in sheep receiving thermal injury, smoke inhalation injury, and combination injury, respectively. The sham animals maintained mesenteric blood flow at 102 +/- 7% of control levels. Thermal injury, as well as combination thermal and smoke inhalation injury, resulted in higher levels of translocation than smoke inhalation injury alone.

Selective permeability changes in the lungs and airways of sheep after toxic smoke inhalation

The effect of toxic smoke inhalation on selective microvascular sieving of macro-molecules and lymph protein flux was assessed in adult sheep to determine whether the time course of microvascular dysfunction differs between the lung and trachea. Protein flux across the lung increased sixfold 48 h after inhalation of the products of incomplete cotton combustion, whereas tracheal protein flux increased fivefold 8 h after exposure and returned to near base line 48 h after exposure. The lung and trachea selectively retained some sieving to three different protein macromolecules with molecular radii of 36, 54, and 123 A. In the lungs the sieving selectivity for these macromolecules was least 48 h after injury, and in the trachea molecular selectivity was least 8 h after injury. These data suggest that the time course of microvascular injury differs for the trachea and the lung; microvascular changes are detected earlier in the trachea than in the lung. The inhalation injury described thus permits the characterization of the time course of airway and lung microvascular changes.

Role of sulfidopeptide leukotrienes in synthetic smoke inhalation injury in sheep

Acute lung injury with smoke inhalation results in significant morbidity and mortality. Previously we have shown that synthetic smoke composed of carbon and acrolein, a common component of smoke, causes delayed-onset noncardiogenic pulmonary edema. To study the possible role of the vasoactive and edemagenic sulfidopeptide leukotrienes (SPLT) in smoke inhalation injury, we measured pulmonary hemodynamics, lung lymph flow, and SPLT and leukotriene (LT) B4 in lung lymph before and after 10 min of synthetic acrolein smoke exposure. After smoke exposure there was a significant rise in pulmonary vascular resistance caused by a rise in pulmonary arterial pressure, a fall in cardiac output, and no change in pulmonary capillary wedge pressure. This was accompanied by an increase in total systemic vascular resistance (P less than 0.05), lung lymph flow (P less than 0.05), and extravascular lung water-to-lung dry weight ratio (P less than 0.05). Both SPLT and LTB4 clearance rose significantly (P less than 0.05), but there was a 10-fold increase in SPLT over LTB4 clearance. In sheep pretreated with FPL55712, a SPLT antagonist, the early rise in pulmonary vascular resistance was attenuated, and the rise in systemic vascular resistance was blocked. This was associated with an attenuated and delayed fall in cardiac output. FPL55712 had no effect on lung lymph flow or extravascular lung water-to-dry weight ratio. SPLT, and especially LTD4, may have a role in increased pulmonary and systemic vascular resistance after smoke inhalation injury but does not appear to affect vascular permeability.

The pathophysiology of carbon monoxide poisoning and acute respiratory failure in a sheep model with smoke inhalation injury

A smoke inhalation model was created in 22 adult male sheep with pine smoke inhalation through an endotracheal tube for 6 min. Arterial blood gases, HbCO, HbO2 and pulmonary compliance (Cdyn) were monitored, and the morphology of the tracheobronchial tree and pulmonary parenchyma were studied by light and electron microscopy. Severe carbon monoxide poisoning with fatal levels of HbCO (greater than 50 percent) was found at the end of smoke inhalation. Acute respiratory distress, progressive hypoxemia, decreased pulmonary compliance and increased P(A-a)O2 and Qs/QT occurred after injury. Tracheobronchial blockade by pseudomembrane cast, pulmonary edema, atelectasis and necrosis of pulmonary epithelia were demonstrated pathologically. The mechanisms of CO poisoning and ARF are discussed.

Pulmonary capillary dynamics and fluid distribution after burn and inhalation injury

A non-linear macroscopic mathematical model is described for the simulation of the different mechanisms that regulate the pulmonary capillary dynamics in patients with thermal injury. The techniques used in the construction of the model are those of 'system's dynamics'. This model has been incorporated into a patient simulator, which makes it possible to analyse the fluid and protein exchanges in a burn patient. The regulating mechanisms involved are: the pulmonary circulation, the fluid and protein transfer between the plasma and the interstitial space at the pulmonary capillary level, and the pulmonary lymphatic system. As a result of the sensitivity analyses of the model we propose that, for the simulation of the effects of an inhalation injury at the pulmonary capillary level, the parameters to be altered will be the pulmonary capillary permeability coefficient for proteins and the pulmonary capillary surface damaged by the injury. To verify the validity and utility of the model, the clinical progress of a series of burn patients with lung injuries has been compared with the results obtained using simulation.

Smoke inhalation injury and the effect of carbon monoxide in the sheep model

The role of carbon monoxide (CO) in causing the physiologic and anatomic changes characteristic of smoke inhalation injury was evaluated in 34 sheep. The smoke-exposed group received a dose of smoke known to produce mild inhalation injury. The CO group received a pure gas mixture that contained concentrations of oxygen, carbon dioxide, and CO similar to those in the smoke. Cardiopulmonary function was measured immediately after exposure, and 24 and 72 hours after exposure. The CO group showed a transient increase in cardiac output, but the smoke group showed no such response. The CO group maintained normal PaO2 levels during the 72-hour study period; the smoke group gradually developed hypoxemia. The lungs of the CO exposed animals had no discernible histologic changes; lungs of the smoke group showed progressive inflammatory changes. These results indicate that CO per se is not the primary etiologic agent of smoke inhalation injury.

Impact of carbon monoxide on cardiopulmonary dysfunction after smoke inhalation injury

With the inhalation of smoke, there are both cardiopulmonary changes and elevated levels of carbon monoxide (CO). We hypothesize that these changes in cardiopulmonary function are the result of a histotoxic hypoxia associated with CO poisoning. This hypothesis was tested in chronically instrumented sheep (n = 19). Piezoelectric crystals were attached to the left ventricle for the measurement of its external minor and major diameters in addition to wall thickness. A pressure transducer was placed in the left ventricle via the apex. The caudal-mediastinal lymph node was also cannulated. After a five-day recovery period, six sheep (smoke group) were insufflated with four series of 16 breaths (700 ml/breath) of cotton smoke, and five sheep (control group) were insufflated with air using a modified bee smoker (smoke group: COHb, 90 +/- 6%; control group: COHb, 6 +/- 1%). Eight sheep (CO group) were ventilated with 2% CO in air to reach a COHb of 90% (COHb, 92 +/- 1%). In the smoke group, lung lymph flow reached 42 +/- 10 ml/hr at 24 hours after smoke insufflation (baseline, 6 +/- 1 ml/hr). The maximum elastance of the left ventricle (end-systolic pressure-volume ratio), a sensitive index of myocardial contractility, was significantly decreased from a baseline of 6.5 +/- 0.9 to 3.3 +/- 0.7 mm Hg/ml. In the control and CO group, neither lung lymph flow nor maximum elastance varied from the baseline value. We conclude that the cardiopulmonary dysfunction after smoke inhalation does not occur after a similar exposure to CO. Initial CO poisoning alone is not a causative factor of cardiopulmonary dysfunction after smoke inhalation.

Effects of allopurinol on smoke inhalation in the ovine model

We hypothesized that the pulmonary damage induced by smoke inhalation is the result of ischemic reperfusion injury. We determined the effect of allopurinol (xanthine oxidase inhibitor) on the pulmonary microvascular fluid flux in an ovine model after inhalation of cotton smoke (n = 13) and compared these data with those from untreated similarly smoke-injured (n = 7), as well as sham- (air, n = 9) smoked, animals and sheep given an equivalent dose of CO (n = 7). Smoke injury resulted in an increased lung lymph flow, lymph-to-plasma protein ratio, lung content of polymorphonuclear cells, and extravascular lung water (gravametric), in addition to histological evidence of tissue (pulmonary) edema and destruction. No significant difference was found in these variables between the sheep that were injured with smoke whether or not they were pretreated with allopurinol. The sham-smoked and CO-insufflated animals showed no significant changes in cardiopulmonary function or morphology. We conclude that there are few data to support a role of ischemic reperfusion injury in the pulmonary damage seen after smoke inhalation.

Managing smoke inhalation injuries

Inhalation injuries most often occur with cutaneous burns, and the likelihood of an inhalation injury increases incrementally with age of the patient and size of the burn. Damage to the pulmonary parenchymal tissue manifests as increased capillary permeability leading to excessive lung fluid formation and increasing hypoxia. An inhalation injury may be diagnosed using observation of indirect criteria in conjunction with fiberoptic bronchoscopy, xenon 133 radiospirometry, and/or measurement of extravascular lung water. Initially, carbon monoxide poisoning threatens the patient's oxygenation capacity. High-flow oxygen therapy reduces the half-life of carbon monoxide to an acceptable period. The patient proceeds through three stages: pulmonary insufficiency, pulmonary edema, and bronchopneumonia. Treatment is directed toward supporting oxygenation using endotracheal intubation with mechanical ventilation, humidification of inspired air, early mobilization, chest physiotherapy, antibiotics for documented infection, and adequate systemic hydration.

Effect of acute smoke inhalation on angiotensin converting enzyme, plasminogen activator, and angiotensin-II in the dog

Smoke inhalation injuries in humans are associated with many uncontrolled variables which impact on the lung and make the cause of the pulmonary response difficult to assess. In this report, an established model of smoke inhalation injury in the dog was used to study the early responses of tissue and serum angiotensin-converting enzyme (ACE), tissue plasminogen activator (PLA), and plasma angiotensin II. Animals were exposed to smoke from burning sawdust and kerosene for five minutes. The hemodynamic and pulmonary mechanical responses were typical with a rise in pulmonary artery pressure, pulmonary vascular resistance, and venous admixture (shunt fraction) while dynamic compliance fell. Within five minutes of smoke exposure, lung ACE declined without any change in serum ACE. Lung PLA dropped one hour after injury. Plasma angiotensin II increased within 30 minutes without evidence for systemic hypertension. These early enzymatic changes substantiate the presence of pulmonary endothelial damage known to occur in this form of chemical injury. These changes may condition the lung's physiologic response to the injury and to additional stresses which are multiple when smoke inhalation occurs in conjunction with a cutaneous burn.

Bronchial artery ligation modifies pulmonary edema after exposure to smoke with acrolein

Pulmonary edema can follow smoke inhalation and is believed to be due to the multiple chemical toxins in smoke, not the heat. We have developed a synthetic smoke composed of aerosolized charcoal particles to which one toxin at a time can be added to determine whether it produces pulmonary edema. Acrolein, a common component of smoke, when added to the synthetic smoke, produced a delayed-onset pulmonary edema in dogs in which the extravascular lung water (EVLW) as detected by a double-indicator technique began to rise after 42 +/- 2 (SE) min from 148 +/- 16 to 376 +/- 60 ml at 165 min after smoke exposure. The resulting pulmonary edema was widespread macroscopically but appeared focal microscopically with fibrin deposits in alveoli adjacent to small bronchi and bronchioles. Bronchial vessels were markedly dilated and congested. Monastral blue B when injected intravenously leaked into the walls of the bronchial vessels down to the region of the small bronchioles (less than or equal to 0.5 mm ID) of acrolein-smoke-exposed dogs but not into the pulmonary vessels. Furthermore, ligation of the bronchial arteries delayed the onset of pulmonary edema (87 +/- 3 min, P less than 0.05) and lessened the magnitude (232 +/- 30 ml, P less than 0.05) at 166 +/- 3 min after acrolein-smoke exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Smoke inhalation injury: evaluation of radiographic manifestations and pulmonary dysfunction

Inhalation injury is a frequent complication in burned patients. Upper airway injury is reliably diagnosed endoscopically, but early diagnosis of pulmonary parenchymal injury is less reliable. Radiographic diagnosis in such cases is inconsistent. This study correlated degree of chest X-ray (CXR) change with pulmonary function in 29 adult patients during the first 5 days after inhalation injury. Daily CXRs were graded: 0 (normal), 1+ (peribronchial cuffing or perivascular edema), 2+ (edema involving one third of the lung field), 3+ (edema involving two thirds of the lung field), and 4+ (edema involving the entire lung field). Extravascular lung water volume (EVLW) was measured in vivo with the thermal/green dye double indicator technique. Twenty-five of the 29 patients were intubated on admission. Of these patients with serious inhalation injury, 84% showed some abnormality on CXR within 48 hours after injury. When abnormalities were present on CXR, pulmonary dysfunction (increases EVLW, increases Qs/Qt, decreases compliance) was clinically important. These data suggest that this grading scale may have utility in reports of CXR findings in inhalation injury.

Smoke inhalation

Appropriate intervention in patients with smoke inhalation requires an understanding of the dynamic aspects of this complex respiratory emergency. This article reviews the etiology, pathophysiology, and treatment of the smoke inhalation injury.