Status Asthmaticus

What is Status Asthmaticus?

Asthma is a long-term disease that causes your airways, which carry air in and out of your lungs, to become inflamed. This leads to symptoms like recurrent wheezing, difficulty breathing, chest pain, and coughing. For mild to moderate asthma attacks, treatments commonly include drugs called β2-agonists and steroids. But sometimes, these treatments don’t work, resulting in a severe asthma attack called status asthmaticus.

Status asthmaticus is a serious medical emergency. It’s a severe form of asthma that can lead to low oxygen levels, high carbon dioxide levels, and even respiratory failure. Any patient with asthma can develop this condition. It can become difficult to manage if not diagnosed and treated immediately, even causing breathing to stop and potentially death.

Despite advancements in medication, status asthmaticus is still one of the leading reasons people visit the emergency department. It’s difficult to predict the outcome of this condition. To improve the patient’s chances, a blend of timely assessment, appropriate tests, and fast symptom relief is beneficial.

Now, let’s talk about the structure of the lungs.

From a developmental perspective, the breathing system starts as an outgrowth at the front part of the gut. The trachea, or windpipe, grows in the middle and creates lung buds. The right lung bud forms 3 major airways, while the left forms 2. The right primary airway is more vertical than the left, making it easier for foreign objects to get stuck. Both primary airways branch out into smaller airways, forming the lung’s other parts.

The surfaces of the larynx, trachea, and bronchi are covered with a type of tissue called pseudostratified columnar ciliated epithelium. Cartilage supports these airways, and specialized cells establish in the bronchial lining. These cells secrete hormones. Mucus glands are found below the surface in the tracheal and bronchial walls.

When we get to the smaller airways (bronchioles), we find no cartilage or mucus glands. The smallest airways, called terminal bronchioles, have a diameter less than 2 millimeters. Past the terminal bronchioles, there are small spherical structures called acini leading to the part of the lung that exchanges oxygen and carbon dioxide, the alveoli.

The alveoli are the lungs’ gas exchange sites. The barrier between the air in the lungs and the blood (blood-air barrier) is composed of several layers, including the capillary lining, a basement membrane, some tissue, the alveoli lining, and defense cells called macrophages. The lining of the alveoli is majorly made up of flat cells called Type I pneumocytes. The more scarce rounded cells, known as Type II pneumocytes, secrete a substance that reduces surface tension in the lungs, keeping them open. When Type I pneumocytes are damaged, Type II cells repair the injury. The alveolar walls contain pores which can become potential pathways for the spread of infections and fluid between the individual alveoli.

What Causes Status Asthmaticus?

Asthma is a long-term disease that causes inflammation in your airways, which can lead to breathing problems. It also makes your airways overly sensitive to certain triggers.

This disease can get worse in two different ways:

1. Slow-onset asthma: This happens when your ability to breathe out forcefully (known as peak expiratory flow rate) gradually worsens over several days. Things like not using your inhaler correctly, not sticking to your medication plan, and stress can contribute to this slow deterioration.

2. Sudden-onset asthma: This happens when your condition worsens severely within hours, usually after a sudden and significant exposure to triggers like allergens, certain foods, and chemicals called sulfites.

Surprisingly, slow-onset asthma is more dangerous and accounts for about 80% to 85% of asthma-related deaths. This reflects a lack of control over the disease over a long time. When this happens, the airways often have a lot of inflammation and are plugged with mucus. On the other hand, those who experience a sudden worsening of asthma usually have clear airways.

Risk Factors and Frequency for Status Asthmaticus

The Centers for Disease Control and Prevention (CDC) shows that the number of asthma cases in the United States has slightly decreased from 7.9% in 2017 to 7.7% in 2021. This condition is more common in adults than children (8.0% vs 6.5%).

• It is often seen more in women, African Americans, and people who develop asthma after the age of 17.
• People with a lower socioeconomic status are more prone to asthma because they usually don’t have easy access to specialist care.
• People living alone are also disproportionately affected.
• According to the CDC, 10.4% of those with asthma live below the poverty line.
• Blacks and American Indians (Alaska natives) have the highest rate of asthma at 10.9% and 12.3% respectively.

Of the adults hospitalized with asthma, an estimated 3% to 16% develop respiratory failure that requires ventilatory support, while this percentage is likely lower in children. Approximately 10% of patients with an intense asthma attack, known as status asthmaticus, who end up in intensive care may die.

Over the past ten years, the application of standardized ventilation strategies, avoiding prolonged muscle-relaxing drug use, and the use of assist-control ventilation have all helped to lower death rates. A look back at data shows that 61.2% of 280 patients treated for asthma in San Antonio, Texas, needed to be put on a ventilator. The mortality rate was around 0.35%. Another retrospective study found a ventilator usage rate of 11.5% and an overall mortality rate of about 2% in over 13,000 children treated for asthma.

Signs and Symptoms of Status Asthmaticus

People suffering from a severe asthma attack, also known as asthma exacerbation or status asthmaticus, usually complain of breathing difficulties. They may also tell you that they had to use their inhaler or breathing machine more often within the past few days. They might have a fever, a cold, be coughing, or have chest pain. It’s important to ask about any illegal drugs they may be using, other health problems they have, their current medications, and any known asthma triggers.

There are a number of factors that can put patients at a greater risk of experiencing a severe asthma attack. These include a past history of severe asthma attacks involving a tube being inserted into their windpipe, having a reduced sensitivity to breathing difficulties and high carbon dioxide in the body due over time to long term lung disease or mental health issues, repeat hospital stays despite taking oral steroids, delaying seeing a doctor after symptoms started, changes in mental status, and not getting enough sleep during the asthma episode. Additionally, if someone has heart disease, asthma treatments might also lead to heart-related side effects.

During a physical exam, patients are often found to have a high heart rate, rapid breathing, and breathing difficulties even when at rest. Listening to their lungs might reveal a whistling sound, which could indicate a restriction of the airways. But, this sound might not always be present in people with severe asthma attack. The absence of this whistling sound should not be taken as a sign of mild disease, regardless of how sick the patient appears to be.

A fast heart rate, exceeding 120 beats per minute, could point to both the severity of the disease and how well the patient responds to treatment with a medication class called β2-agonists. Successful treatment is usually associated with a drop in the heart rate from 120 to 105 beats in 24 hours. While the heart rhythm is usually fast and consistent, irregular heart rhythms might also be seen.

• Septal deviation to the left due to an enlarged right ventricle
• Increased pressure after contraction of the left ventricle
• Increased pressure in the right ventricle due to increased lung artery pressure

These factors cause the systolic blood pressure, or the pressure in the arteries when the heart beats, to drop during a deep breath in. This drop is considered serious when it is at least 10 mm Hg, but in severe asthma attacks, it could be more than 12 mm Hg. However, this drop might decrease in later stages as the patient becomes too tired and loses their breathing drive. If you are dealing with patients who are at risk of experiencing severe asthma attack or have poor heart function, you should be ready to perform life-saving procedures.

Testing for Status Asthmaticus

For patients that are having difficulty breathing, it’s important for them to be connected to devices that monitor their heart, blood pressure, and oxygen levels. While these checks are taking place, healthcare providers must check the patient’s vital signs routinely – every 15 minutes. This is because any change in how alert the patient is can be a sign they’re not getting enough oxygen.

Measuring how obstructed the patient’s airflow is can be tricky, but it can be done effectively by using tests such as peak expiratory flow rate (PEFR) and forced expiratory volume in 1 second (FEV1). If either of these is lower than half of what the patient usually achieves, this signals severe blockage in the airways. Readings of less than 120 liters per minute for PEFR and less than 1 liter for FEV1 are indicators of severe disease. If this is the case, arterial blood gas (ABG) assessment should be performed.

Different laboratory tests and imaging can be used to identify anything that may be making asthma worse. They can also assess the severity of the disease and rule out other reasons for shortness of breath. Initial blood tests often consist of a complete blood count (CBC), a basic metabolic panel (BMP), and an ABG test. The CBC typically shows an increase in white blood cells which might be because of a bacterial infection or a viral infection, which can be confirmed with a swab, sputum test, or blood culture.

A metabolic panel checks the balance of electrolytes and evaluates kidney function, which may be impacted by factors such as dehydration and poor food intake. Tests for heart function can help rule out any urgent cardiac issues. Signs of blocked airways on an electrocardiogram can include temporary changes such as prominent P waves or an altered direction of the electrical heart activity known as right-axis deviation.

A chest X-ray image can help revail any conditions like bronchiectasis, pneumonia, or pneumothorax, that can make asthma harder to manage. In some chronic asthma cases, the X-ray may show a thickened airway wall and over-inflation. A bedside ultrasound can also provide valuable information by differentiating other conditions like heart failure, lung fluid, pneumonia, and chronic obstructive lung disease from an asthma flare-up. It can also help monitor fluid status.

An ABG test can help assess the patient’s oxygen levels and how well they are breathing, but these results should always correspond with how the patient appears clinically. This test could also be used to identify cases of respiratory failure. Initial results may show alkalosis (increased pH) and reduced oxygen levels. The carbon dioxide level might seem to be within the normal range as the disease gets worse, which might be misinterpreted as progress. However, it is a sign of the respiratory muscles getting tired and might show the need for mechanical breathing support.

The table charts ABG findings in acute asthma attacks. In severe cases, the acid/base balance in the body can be significantly off, often as a result of high lactate levels.

Tests for Immunoglobulin E, skin, and allergen-specific blood tests can be valuable in identifying the trigger in patients who may have been exposed to a new allergen. Managing allergies is often important in the overall management of asthma. Avoiding known triggers is usually the best way to control allergic reactions.

Treatment Options for Status Asthmaticus

Tracking changes in a person’s Peak Expiratory Flow Rate (PEFR), or the maximum speed of expiration, can help health professionals decide whether hospitalization is necessary based on the severity of their symptoms. According to some studies, if a person’s PEFR improves significantly two hours after treatment, they might require hospitalization.

Good initial responses to treatment in severe asthma include sustained symptom improvement for at least half an hour following the last bronchodilator dose, and a PEFR greater than 70% of the predicted value. However, if PEFR improves by less than 10%, or is less than 40% of the predicted value, this suggests continued decline and increased need for intensive care. This care is also recommended in case of respiratory failure, altered mental status, arrhythmia, cardiac or respiratory arrest, or complications such as pneumothorax or pneumomediastinum.

Patients who respond well initially may benefit from longer observation, as studies show a lower relapse rate in patients treated and observed for 2 to 4 additional hours. Securing a hospital bed is determined by both clinical and psychosocial assessments. In cases with inadequate response to initial treatment or poor environmental conditions, hospitalization may also be considered.

The primary aim of medication in the case of bronchoconstriction, a narrowing of the airways, is to reduce muscle spasms and improve oxygen levels and airflow. The first line of acute asthma treatment are drugs called β2-agonists, delivered either inhaled or through a nebulizer. Other medications like corticosteroids and anticholinergics can be useful, especially for severe cases not responding to β2-agonists. In certain cases, magnesium sulfate and oxygen can also be helpful.

Hospital treatments also often involve oxygen supplementation and ventilatory support. More severe cases might require noninvasive ventilation or even intubation. There are a variety of sedatives available for this process, including ketamine and propofol. Extracorporeal membrane oxygenation (ECMO), where blood is oxygenated outside the body, may be considered in cases of persistent hypoxia and acidosis. Finally, despite some evidence to the contrary, antibiotics should be administered in the presence of infection symptoms.

What else can Status Asthmaticus be?

When diagnosing severe asthma attacks, known as status asthmaticus, doctors look out for other conditions that also cause serious breathing difficulties. These might include:

• A lung collapse or Pneumothorax, identified by uneven breathing sounds.
• An air build-up around the heart, or Pneumomediastinum, which typically shows as a crunching sound in the chest or neck, when examined.
• Obstructions in the windpipe, which usually result in a high-pitched noise during inhalation.
• A foreign body in the respiratory tract or mucus blockages causing wheezing in only one part of the lung.
• Repeated severe asthma attacks associated with an excessive collapse of the small airways, usually in adults with prolonged use of positive pressure ventilation.
• Pneumonia, which often presents with additional unusual sounds such as wheezes or crackles.
• Chronic Obstructive Pulmonary Disease, or COPD, often identified by worsening breathlessness during exercise and a history of heavy smoking.
• Acute heart failure, which may be determined by elevated heart enzymes or bedside heart scans.
• An Aspergillus allergy, or Allergic bronchopulmonary aspergillosis, recognizable by a positive Aspergillus skin test or specific imaging findings.
• Vocal cord disorders, usually observed as an inhalation squeal and wheezing.
• Inhalation injuries that can trigger an asthma flare-up, usually identified by nasal and oral inflammation.
• Neurological conditions like Myasthenia Gravis, typically showing system-wide muscle weakness during a neurological examination.

To establish a correct diagnosis, a thorough medical review and appropriate diagnostic tests are key.

What to expect with Status Asthmaticus

If treated quickly, status asthmaticus (a severe asthma condition) generally has a positive outcome, especially if the patient does not have other health issues like heart failure or COPD (a lung disease). However, according to a study by Afessa and others, people who did not survive status asthmaticus often had higher levels of acid in the blood and difficulty in removing carbon dioxide from their bodies.

Needing mechanical help to breathe has been identified as a factor that can lead to a worse outcome. Additionally, a study by Adnet and others found that using drugs to paralyze muscles during the process of inserting a tube to assist breathing can increase the risk of muscle weakness, lung infections, and extended stays in the intensive care unit.

Possible Complications When Diagnosed with Status Asthmaticus

Acute low blood pressure that happens suddenly after being sedated or put on a breathing machine needs immediate attention, especially in patients with severe asthma. A condition called tension pneumothorax, a serious and time-sensitive issue where air fills the space around the lungs, needs to be checked and managed without delay. Diagnosis can be done by bedside clinical examination, ultrasound, or chest x-ray, and it is treated right away by inserting a tube into the chest to remove the air.

Another common cause of low blood pressure in asthma patients on a breathing machine is dynamic hyperinflation. This happens when the exhalation (breathing out) time is too short, and the lungs don’t empty completely, causing trapped air and increased pressure inside the lungs. If not detected and managed promptly, it can result in increased pressure, higher risk of lung injury and increased pressure inside the chest. This could reduce the return of blood to the heart and lead to low blood pressure.

If a patient shows signs of increased pressure inside the lungs, they should be temporarily removed from the breathing machine, and their chest walls should be compressed to help empty the lungs. After placing them back on the machine, the amount of air breathed out should be increased either by reducing the amount of air or the rate of breathing. Some patients might need more sedation or to be paralyzed. Breathing machine-applied pressure should be moderate in patients with severe asthma due to the risk of lung injury and low blood pressure.

In patients with severe asthma, without increased pressure inside the head or severely weak heart function, they could try purposeful under-breathing and allowing a slight increase in carbon dioxide levels in the blood. This approach can reduce dynamic hyperinflation and mismatched air and blood flow in the lungs. The goal is to keep the blood’s pH level greater than 7.5, which is generally safe, rather than aiming for a specific carbon dioxide level.

High pressure with steady ‘plateau’ ventilator pressure should also lead to efforts to clear the airway and breathing tube of secretions. Patients with severe asthma tend to develop thick and hard to remove secretions. A larger breathing tube is preferred due to the high resistance in the airway and the need for airway clearance.

Other commonly reported issues include electrolyte abnormalities, low blood pressure and irregular heart rhythms. Severe hypotension and acidosis in the lungs in hard to treat cases have resulted in heart attack, cardiac arrest, brain damage due to low oxygen, medication toxicity, and even death.

Preventing Status Asthmaticus

The best way to manage asthma is to prevent flare-ups from happening in the first place. This can be achieved by avoiding things that trigger asthma attacks and by regularly taking prescribed medications. For those with allergies to things in their environment, it’s crucial to manage these allergens as well. Special attention should be given to individuals who are particularly at risk of having asthma attacks, like older and younger people or people who can’t easily get medications.

It’s also been found that having people who are trained, but not necessarily medical professionals, teach patients how to properly use their inhalers can improve the patients’ ability to stick to their treatment plans after they leave the hospital.