Smoke Inhalation
Chapter 43: Smoke Inhalation and Thermal Injuries
Overview of Fire Incidents
Fire remains a significant source of injury, death, and economic loss.
Residential Fires: Most frequent setting for burn-related injuries.
Fire-Related Deaths: Third leading cause of accidental deaths.
Causes of Death: Respiratory tract injury and systemic poisoning from smoke inhalation contribute to 50-90% of deaths in burn victims.
Smoke Inhalation Injury: Occurs in 10-35% of patients treated in burn centers.
Thermal Injury
Definition: Injury caused by the inhalation of hot gases.
Affected Areas: Primarily affects upper airway, which includes:
Nasal cavity
Oral cavity
Nasopharynx
Oropharynx
Laryngopharynx
Distal Airways: Typically spared from serious injury due to:
Upper airways' ability to cool hot gases
Reflex laryngospasm
Glottic closure
Exception: Direct thermal injuries may occur below the larynx in cases of steam inhalation.
Anatomic Alterations of the Lungs due to Thermal Injury
Common alterations include:
Blistering
Mucosal edema
Vascular congestion
Epithelial sloughing
Thick secretions
Acute upper airway obstruction
Smoke Inhalation Injury
Pathologic Changes: Caused by:
Irritating and toxic gases
Suspended soot particles
Vapors from incomplete combustion
Toxic Substances: Many constituents of smoke are highly caustic and poisonous, affecting the tracheobronchial tree.
Stages of Injury Progression: Classified into early, intermediate, and late stages.
Early Stage (0 to 24 Hours after Inhalation)
Symptoms may not be immediately apparent despite obvious burns.
Changes occur rapidly within the first 24 hours, including:
Increased inflammation of the tracheobronchial tree leading to bronchospasm.
Overproduction of bronchial secretions, causing airway obstruction.
Toxic effects slowing mucosal ciliary transport, contributing to mucus retention.
ARDS: May develop, often described as “leaky alveoli,” stemming from noncardiogenic high-permeability pulmonary edema.
Potential Causes of Noncardiogenic Pulmonary Edema: Overhydration from excessive fluid resuscitation.
Intermediate Stage (2 to 5 Days after Inhalation)
Pathological Changes: Upper airway thermal injuries improve while changes in lung tissue peak.
Increased mucous production, decreasing mucosal ciliary transport activity leads to:
Necrosis and sloughing of tracheobronchial mucosa (commonly around days 3-4).
Resulting mucous plugging and atelectasis.
Bacterial complications such as bronchitis and pneumonia (common organisms include gram-positive Staphylococcus aureus and gram-negative species like Klebsiella, Enterobacter, Escherichia coli, and Pseudomonas).
Potential Development: ARDS may occur at any point.
Aggravating Factors for Patients with Chest Burns:
Pain-induced shallow breathing
Narcotic use inhibiting cough
Immobility
Increased airway resistance and decreased lung compliance.
Late Stage (5 or More Days after Inhalation)
Primary Concerns: Infection from burn wounds leading to sepsis and multiorgan failure, the leading cause of death in severely burned patients.
Infections: Pneumonia remains a significant issue.
Pulmonary Embolism: Possible development within two weeks due to DVT from hypercoagulable states and immobility.
Long-term effects can include:
Restrictive lung disorders from alveolar fibrosis and chronic atelectasis.
Obstructive lung disorders due to chronic bronchial secretion influx, stenosis, polyps, bronchiectasis, and bronchiolitis.
Etiology of Smoke Inhalation
Incident Statistics (2022):
1.5 million fires responded to by fire departments.
3,790 civilian fire deaths and 13,250 injuries recorded, costing an estimated $18 billion in property damage.
Average response rate: one fire department responds every 21 seconds.
Fire Occurrence:
Over a third (35%) of fires occur in structures.
Home fires cause approximately 72% of civilian fire deaths and 75% of injuries despite being 25% of total fires.
Vehicle fires: 13% of fires, 16% of deaths, and 5% of injuries.
Prognostic Factors affecting fire victims include:
Extent and duration of smoke exposure
Chemical composition of smoke
Size and depth of burns
Inhaled gas temperature
Age (prognosis worsens for the very young or old)
Preexisting health conditions.
Mortality Rates: Doubled when smoke inhalation injury accompanies full-thickness burns.
Composition and Characteristics of Smoke
Smoke arises from either:
Pyrolysis: Involves smoldering in low-oxygen conditions.
Combustion: Visible flame burning in an oxygen-rich environment.
Smoke Composition: A complex mix of particulates, toxic gases, and vapors; varies based on combusted materials and oxygen availability.
Body Surface Area (BSA) Statistics
Rule of Nines for estimating BSA burns:
Entire head and neck: 9% (Adult), 18% (Infant)
Each arm: 9% (Both Ages)
Anterior trunk: 18% (Both Ages)
Posterior trunk: 18% (Both Ages)
Genitalia: 1% (Both Ages)
Each leg: 18% (Adult), 13.5% (Infant)
Severity and Depth of Burns
First Degree (Superficial Burn):
Affects only the outer epidermal layer.
Symptoms: Redness, tenderness, pain.
Healing time: 6 to 10 days; results in normal skin.
Second Degree (Partial Thickness Burn):
Extends through the epidermis into the dermis, allowing for regeneration of epidermis.
Symptoms: Blisters, pain.
Healing time: 7 to 21 days; healing may result in normal or varied textured skin.
Third Degree (Full Thickness Burn):
Destroys epidermis and dermis, affecting underlying tissue; may appear charred or coagulated.
Healing may take longer than 21 days or may require skin grafting if extensive.
Healing results in hypertrophic scars or keloids.
Cardiopulmonary Clinical Manifestations from Smoke Inhalation and Thermal Injuries
Manifestations Supported by Pathophysiological Changes:
Atelectasis
Alveolar consolidation
Increased thickness of the alveolar-capillary membrane
Bronchospasm
Excessive bronchial secretions
Clinical Examination Data
Vital Signs: Increased respiratory rate (tachypnea), heart rate, and blood pressure.
Assessment for Acute Upper Airway Obstruction (indicators include):
Pharyngeal edema and swelling
Inspiratory stridor
Hoarseness
Altered voice
Pain while swallowing.
Signs of Cyanosis: Possible cough and sputum production.
Chest Assessment Findings:
Usually normal breath sounds in early stages.
Possible wheezing, crackles, or rhonchi present.
Laboratory Tests and Procedures
Arterial Blood Gases: Indicators during severe smoke inhalation and burns with metabolic acidosis include:
COHb levels
pH, PaCO2, HCO3, and PaO2.
Carbon Monoxide Poisoning
Blood Carboxyhemoglobin (COHb) levels and clinical manifestations:
0-10%: Usually no symptoms
10-20%: Mild headache, cutaneous blood vessel dilation
20-30%: Cherry red skin, not always certain
30-50%: Severe headache, nausea, impaired judgment
50-60%: Syncope and increased heart and respiratory rates
60-70%: Coma, cardiovascular and respiratory distress
70-80%: Cardiopulmonary failure and potential death.
Radiologic Findings
Chest Radiograph Variability:
Generally normal in the early stages of injury.
Indications of pulmonary edema or ARDS in the intermediate stages.
Late stages may show patchy or segmental infiltrates.
General Management of Smoke Inhalation and Thermal Injuries
Initial Assessment Goals:
Evaluate airway and respiratory status.
Cardiovascular evaluation.
Assess percentage and depth of body burns.
Immediate Actions:
Start IV line for medications and fluids.
Remove clothing easily and soak any stuck clothing before removal.
Cover burn wounds to prevent shock, fluid loss, heat loss, and pain.
Implement infection control: isolation, room pressurization, air filtration, and wound coverings.
Fluid Resuscitation
Ringer’s Lactate Solution:
Administered according to the Parkland Formula: of body weight for each percent of BSA burned over 24 hours.
Ensure the patient's hemodynamics remain stable, targeting average urine output of 30-50 mL/hr and CVP between 2-6 mm Hg.
Airway Management
Endotracheal Intubation: Essential for patients showing signs of impending upper airway obstruction after inhaling hot gases.
Bronchoscopy: Often employed to clear mucous plugs and eschar from the airway.
Hyperbaric Oxygen Therapy: Can aid in rapid carbon monoxide elimination and enhance skin graft viability.
Special Treatments
Cyanide Poisoning: Amyl nitrite inhalation and intravenous sodium thiosulfate are recommended treatments.
Antibiotics: Used prophylactically to tackle burn and pulmonary infections.
Expectorants and Analgesics: Encourage expectoration and manage pain associated with surface burns.
Anticoagulants: Such as heparin may be prescribed for patients with significant fire-related injuries, particularly to prevent deep venous thrombosis.
Respiratory Care Treatment Protocols
Protocols Include:
Oxygen Therapy Protocol
Bronchopulmonary Hygiene Therapy Protocol
Lung Expansion Therapy Protocol
Aerosolized Medication Protocol
Mechanical Ventilation Protocol