What is Inhalation Injury?
In simple terms, inhalation injury describes lung damage caused by breathing in harmful substances like smoke, gases, vapors, or fumes. This is often seen in people who have been in a fire and have inhaled smoke. Smoke inhalation is one of the most common types of inhalation injuries, and this discussion will primarily focus on that. However, we won’t be discussing burns from heat outside the body or harms from swallowing dangerous substances.
What Causes Inhalation Injury?
Smoke inhalation injuries happen when a person’s breathing system comes into direct contact with heat from a fire and harmful chemicals created from materials breaking down in the fire. What’s in the smoke can change with every fire, depending on what’s burning, how much oxygen the fire has, and the fire’s characteristics.
Fires with a lot of oxygen and high temperatures often don’t create a lot of smoke. But fires with less oxygen and lower temperatures can produce more harmful chemicals like carbon monoxide. Smoke can also contain other toxic things like ammonia, carbon dioxide, hydrogen cyanide, certain types of aldehydes, sulfur dioxides, and nitrogen dioxide.
These elements form a mix of gases, small solids that float in the air, and liquid vapors that combine with the regular air to create smoke. Breathing in these parts of the smoke can damage both the upper part (nose and throat) and lower part (lungs and bronchial tubes) of the breathing system.
Risk Factors and Frequency for Inhalation Injury
In 2015, FEMA recorded 380,940 house fires in the US, which resulted in 2,565 deaths and 11,475 injuries related to the fires. Interestingly, the number of deaths from fires has not decreased since 2006, even showing a small increase of 2%, even though fire-related injuries actually decreased by 9% during the same period. The most common cause of death from these fires is respiratory failure, and about one-third of all people who suffer burn injuries also have injuries from smoke inhalation.
Signs and Symptoms of Inhalation Injury
When examining patients for potential inhalation injuries, healthcare providers should be wary of various factors. These include the type of exposure such as smoke, flames, or chemicals, time and location of exposure, and any instances of loss of consciousness. Medical personnel should also consider any obstacles to quick evacuation like mobility issues or disorientation, particularly for the elderly and children. It’s also important to remember that children can be more exposed to such risks since they breathe at a faster rate than adults.
The history of the patient’s exposure should be thoroughly documented. Even if a patient doesn’t show visible burn injuries, they may have inhaled smoke, which can cause internal injury. Symptoms may include a burning sensation in the nose or throat, a cough with increased mucus production, difficulty breathing with a high-pitched, noisy breathing and wheezing. Difficulty swallowing after smoke exposure could also indicate potential inhalation injury. Additionally, these patients may experience systemic symptoms such as headaches, confusion, hallucinations, and even loss of consciousness.
During a physical examination, healthcare providers should look for signs that might point to inhalation injuries. These signs include burns on the face, loss of facial or nasal hair, and the presence of soot in the patient’s mouth or mucus. Additionally, struggling to breathe, fast breathing, bluish skin, high-pitched breathing noise, and abnormal lung sounds should be considered. If the patient presents with symptoms suggesting an imminent upper airway obstruction, urgent measures such as intubation should be contemplated.
Patients should be informed about the possibility of delayed symptom onset after exposure. These delayed symptoms can affect the lower respiratory airways due to exposure to chemical toxins that may not initially affect the upper airways. For example, exposure to nitric oxide – a common product when certain materials like fabric or cellulose are burnt – can result in delayed symptoms up to 72 hours after exposure.
Testing for Inhalation Injury
If you’ve been exposed to smoke, your doctor might want to do a series of tests to check if you have a smoke inhalation injury. Such injuries are often not easy to detect in their initial stages. Some tests that might be used include:
Chest Imaging: These are pictures taken of your chest. Regular chest X-rays could be taken over time to check for any damage due to smoke inhalation. Often, these are negative early on in the process. Another type of test, a computed tomography (CT) scan, could be used to give a more detailed image of the chest area.
Blood Tests: These tests give information about the overall health of your body. A complete blood count (CBC) checks for the number of different types of cells in your blood. A complete metabolic panel (CMP) checks your blood sugar, electrolyte and fluid balance, kidney function, and liver function. A lactate test is used to check for a build-up of lactic acid in your body, which could indicate tissue damage.
Pulse Oximetry: This is a test that uses a small device placed on your finger to check the amount of oxygen in your blood. It might be falsely high if you were exposed to carbon monoxide.
Arterial Blood Gas: This is a blood test that measures the levels of certain gases (like oxygen and carbon dioxide) present in the blood from an artery. It can help determine how well your lungs are working.
Carboxyhemoglobin Level: This test measures the amount of carbon monoxide present in your blood. High levels can indicate over-exposure to smoke.
Cyanide Level: This test checks for cyanide poisoning, though it may not always be readily available and therefore, has limited use in an emergency setting.
Pulmonary Function Testing: The flow-volume loop test is a non-invasive test that can assess how well air is moving in and out of your lungs. It can provide important information on any lung damage due to smoke inhalation.
Bronchoscopy and Direct Laryngoscopy: These tests involve the use of a thin tube with a light and camera to closely examine your windpipe (trachea) and air passages to your lungs (bronchi), and your voice box (larynx), respectively. They help check for any signs of injury due to smoke inhalation.
Treatment Options for Inhalation Injury
If a patient is exposed to harmful substances, such as smoke in a house fire, it’s crucial to remove the person from the exposure area as soon as possible. The most important initial steps are to ensure the airway stays unblocked, preventing suffocation and inhaling more harmful substances. In severe cases, doctors may insert a tube into the patient’s windpipe, a procedure known as intubation, to ensure they can continue breathing.
Smoke inhalation can cause swelling, bleeding, and damage to the lining of the airway, which can block the passage of air. Therefore, patients are usually given intensive care to help manage lung secretions. A medication called N-acetylcysteine, also known as a mucolytic, can be used to break down these secretions. However, as it may cause the airways to tighten or narrow, a medication to widen the airways, known as a bronchodilator, might be used beforehand.
Doctors may also administer bronchodilators to manage airway blockages caused by narrowing of the airways. Such medications can include beta-2-adrenergic agonists like albuterol and salbutamol, as well as muscarinic receptor antagonists like tiotropium. Steroids, however, haven’t been proven beneficial for smoke inhalation injuries.
While some might think antibiotics would be a good preventative measure due to the increased risk of pneumonia with smoke inhalation injuries, early use of these drugs isn’t recommended. Antibiotics should only be started when there’s a confirmed diagnosis of pneumonia.
Nebulized heparin, a drug in mist form that’s inhaled through a device known as a nebulizer, has shown promising results in treating smoke inhalation injury. The drug works by reducing the inflammatory response and formation of fibrin, a protein involved in blood clotting, which can help relieve airway blockages.
The treatment for smoke inhalation damage is often determined by the harmful substances inhaled, duration and concentration of exposure, and the substances’ water solubility. For instance, if there’s suspicion of carbon monoxide poisoning, alongside smoke inhalation, high oxygen therapy can be beneficial. Hyperbaric oxygen treatment, which involves breathing in pure oxygen in a pressurized room, can speed up the elimination of carbon monoxide from the blood, but is often not widely available. Cyanide poisoning is another potential concern in cases of smoke inhalation. If it’s strongly suspected, an antidote called hydroxocobalamin may be administered, though tests to confirm cyanide poisoning aren’t always readily available.
What else can Inhalation Injury be?
Several conditions can affect breathing and lung function, which might potentially include:
- Acute respiratory distress syndrome (ARDS), a severe lung condition causing shortness of breath
- Asthma, a chronic condition that inflames and narrows the airways
- Aspiration pneumonitis or pneumonia, which can occur when something other than air enters your lungs
- Chronic obstructive lung disease (COPD), a long-term lung disease that blocks airflow
- Congestive heart failure, a condition where the heart doesn’t pump blood as well as it should, leading to fluid build-up in the lungs
- Interstitial lung diseases, a group of disorders that cause scarring of lung tissue
- Pulmonary embolism, a sudden blockage in one of the lung arteries
- Pneumonia caused by viral or bacterial infections
- Pneumothorax, also known as a collapsed lung
What to expect with Inhalation Injury
People who have been affected by smoke inhalation are more likely to suffer frm serious problems. In many cases, fatal burns occur due the failure of the respiratory system, either from the damage caused directly by the inhalation or from complications like pneumonia. Severe inhalation injuries can lead to long-term issues such as bronchiectasis (damage causing widening and scarring of the large airways), bronchiolitis obliterans (a serious lung condition that affects the small airways), and the need for artificial breathing aid.
Despite these potential complications, it’s important to note that many individuals recover without lasting effects from a single smoke inhalation incident.
Possible Complications When Diagnosed with Inhalation Injury
Most people who inhale smoke will have injuries that are mild to moderate. The seriousness of the injury usually depends on how long a person was exposed to the smoke. The more intense and prolonged the exposure, the more severe the injury tends to be. For those with mild or moderate injuries, symptoms usually clear up by themselves within three days and complications are rare.
However, in cases of severe smoke inhalation, complications can start to appear within four to five days. The most common complication is pneumonia. Patients may also experience severe respiratory distress, fluid builds up in the lungs, and may require assistance from a machine to help them breathe. Those with existing respiratory conditions like COPD and asthma have higher chances of complications.
Long-term complications are less likely, but they can happen. These may include narrowed air passages, damage to the lung’s airways, and obstruction of the small airways in the lungs due to inflammation. People exposed to carbon monoxide may experience long-term neurological changes. Severe brain damage is possible with carbon monoxide poisoning, but it’s not common.
More often, patients report ongoing or delayed neurological symptoms following carbon monoxide poisoning, including persistent depressed mood, trouble focusing, and short-term memory issues. These symptoms are more common in those who lost consciousness and can develop one to three weeks after the incident. Researchers are currently studying the effectiveness of hyperbaric oxygen therapy, a treatment where patients breathe pure oxygen in a pressurized chamber, as a potential treatment for these neurological symptoms.
Common symptoms:
- Depressed mood
- Trouble concentrating
- Issues with short-term memory
Preventing Inhalation Injury
Preventing smoke inhalation is best accomplished through fire prevention methods. The most effective way to prevent injuries from smoke inhalation and fires in general is to use well-maintained fire and smoke alarms. In the United States, smoke detectors are widespread and 96% of all homes reportedly use them. However, it’s concerning to note that over 5 million homes still lack these critical safety features. Furthermore, in 38% of all home fire-related deaths, smoke alarms were not installed, and in 21% of these fatal incidents, the alarms did not go off. This usually occurred because the alarms were purposely disconnected or they didn’t have batteries installed.