Discover the causes, symptoms, and treatment options for Acute Respiratory Distress Syndrome (ARDS) on Meri Sehat."

Acute Respiratory Distress Syndrome

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ZAKA CLINIC GULBERG LAHORE

Saad Ullah Siddiqui

Overview

Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury that results from fluid buildup in the alveoli in the lungs.&nbsp;&nbsp;&nbsp;&nbsp; 
The American-European Consensus Conference (AECC) describes ARDS as an acute disease characterized by bilateral lung infiltrates and severe hypoxemia (insufficient blood oxygen levels) in the absence of cardiogenic pulmonary edema. Other clinical manifestations may include breathing difficulties (dyspnea), rapid breathing (tachypnea), and excessively deep and rapid breathing (hyperventilation).

In ARDS, the alveoli and the capillaries that surround them (the site of gas exchange in the lungs) are damaged by an inflammatory process like pneumonia, sepsis, <a href="https://merisehat.pk/disease/covid-19">COVID-19</a>, etc. Approximately 10-15% of intensive care unit (ICU) admissions and 23% of mechanically ventilated patients develop ARDS<a href="#accordion">[11]</a>. The incidence of the disease varies geographically with more cases being reported in Europe and the United States<a href="#accordion">[9]</a>. Moreover, the incidence of ARDS increases with age. It ranges from 16 cases per 100,000 person-years in 15-19-year-olds to 306 cases per 100,000 person-years in 75-84-year-olds<a href="#accordion">[1]</a>.

A recent single-center study evaluated the incidence of ARDS from 2001 to 2008 and discovered that the rate reduced from 82.4 to 38.9 cases per 100,000 person-years<a href="#accordion">[1]</a>. This decrease was attributable to a decrease in hospital-acquired ARDS<a href="#accordion">[1]</a>.

The COVID-19 pandemic led to a rise in hospitalizations across the world. In the United States, it caused an increase in the prevalence of ARDS<a href="#accordion">[12]</a>. Moreover, around the world, 40% of deaths were linked to acute respiratory syndrome<a href="#accordion">[12]</a>. As per a study conducted at a public sector hospital in Karachi, Pakistan, ARDS was the most common complication among COVID-19 patients and led to high mortality rates<a href="#accordion">[13]</a>. 
&nbsp;

Based on the severity of hypoxemia, ARDS is classified into mild, moderate, and severe<a href="#accordion">[9]</a> <a href="#accordion">[11]</a>. 
&nbsp;

<ul>
	<li>Mild ARDS - Approximately 25% of ARDS cases are classified as mild. It is defined as a PaO2/FiO2 (a ratio of arterial oxygen tension to the fraction of inspired oxygen) ratio of 200-300 mmHg.</li>
	<li>Moderate ARDS - A PaO2/FiO2 ratio of 100-200 mmHg defines moderate ARDS.</li>
	<li>Severe ARDS - Approximately 75% of ARDS cases are moderate or severe. A PaO2/FiO2 ratio of less than 100 mmHg defines ARDS. 
	&nbsp;</li>
</ul>

Signs and Symptoms

ARDS usually develops within 24 to 48 hours after the initial accident or illness. It is a potentially fatal disorder characterized by pulmonary inflammation that may begin in one lung but eventually affects both, causing the destruction of the air sacs (alveoli) and surrounding blood vessels. The injured alveoli contract or fill with fluid (lung edema), limiting their capacity to oxygenate the blood and remove carbon dioxide. Patients endure progressively acute respiratory discomfort as oxygen levels in arterial blood and tissues fall. ARDS puts a lot of strain on your lungs. 
&nbsp;

The common signs and symptoms are:

<ul>
	<li>Shortness of breath</li>
	<li>Low blood pressure</li>
	<li>Unusually fast breathing</li>
	<li>Fast heartbeat</li>
	<li>Cough</li>
	<li>Fever</li>
	<li>Chest pain, especially when breathing deeply</li>
	<li>Confusion and exhaustion</li>
	<li>Blue-tinted lips or nails from lack of oxygen in your blood (cyanosis)</li>
	<li>Dizziness 
	&nbsp;</li>
</ul>

Causes

Respiratory illness or injury can damage the protective membranes between the alveoli and blood vessels. This results in blood and fluid leaking from the blood vessels into and between the air sacs. The presence of fluid disrupts the exchange of gasses; thus, decreasing the level of oxygen in the blood. 
&nbsp;

The following are the main causes of ARDS:

<ul>
	<li>Sepsis:&nbsp;A major infection in the lungs (pneumonia) or other organs with significant inflammation is the most prevalent cause of ARDS.</li>
	<li>Aspiration Pneumonia: Aspiration of stomach contents into the lungs can result in serious lung injury and ARDS.</li>
	<li>Coronavirus (COVID-19): This infection may lead to severe ARDS.</li>
	<li>Massive blood transfusion and pancreatitis.</li>
	<li>Major Trauma And Burns: Accidents and falls can cause direct harm to the lungs or other organs in the body, resulting in significant inflammation and injury to the lungs.</li>
	<li>Inhalational Injury: Breathing and exposure to high concentrations of chemical fumes or smoke.</li>
	<li>Drug Overdose: An overdose on drugs like cocaine and opioids can result in ARDS. 
	&nbsp;</li>
</ul>

Diagnosis

There is no particular test that can detect ARDS. It&#39;s more like a jigsaw puzzle that your doctor is putting together. They will rule out any illnesses with comparable symptoms.

Your doctor will inquire about your medical history, perform a physical exam, and monitor your breathing and heartbeat. They may also check for extra fluid in your body and bluish color on your lips or skin. The assessment is likely to include: 
&nbsp;

<h5>Medical History</h5>

Your doctor may question you about any medical illnesses or recent occurrences that might be considered risk factors for ARDS. Your doctor will also inquire about your symptoms, and whether you have a cardiac problem, such as heart failure, or another illness that might cause symptoms comparable to ARDS. 
&nbsp;

<h5>Physical Exam</h5>

This examination may include:

<ul>
	<li>Listening to your lungs with a stethoscope for unusual breathing sounds like crackling</li>
	<li>Examining your heart for a rapid heart rate</li>
	<li>Checking for indicators of trouble breathing, such as the use of accessory muscles for breathing</li>
	<li>Examine your skin or lips for bluish discoloration, which might indicate a low blood oxygen level.</li>
	<li>Examining your body for swelling or other symptoms of excess fluid, which might indicate heart or renal issues.</li>
	<li>Checking blood pressure</li>
	<li>Checking blood oxygen levels (pulse oximetry) 
	&nbsp;</li>
</ul>

<h5>Test And Procedures 
&nbsp;</h5>

Imaging

<ul>
	<li>Chest X-Ray: It may identify which areas of your lungs have fluid in them, the level of fluid in them, and whether your heart is enlarged. The presence of lung infiltrates can also be seen on chest X-rays.</li>
	<li>Computerized Tomography (CT) Scan: A CT scan is more sensitive than a chest X-ray in detecting pleural effusion, pulmonary interstitial emphysema, and pulmonary infiltrates. However, since a majority of ARDS patients are ICU admissions on mechanical ventilation, transferring such critical patients for CT scans is not always recommended. 
	&nbsp;</li>
</ul>

Lab Tests

Arterial blood samples can help assess oxygen levels in the blood. The doctor may also order additional tests, such as a liver function test, renal profile, and a complete blood count to detect the underlying cause of ARDS.&nbsp; 
&nbsp;

Heart Tests

The signs and symptoms of ARDS are similar to those of other heart diseases. Therefore, your doctor may suggest cardiac testing, such as:

<ul>
	<li>Echocardiogram - The test detects any problems with the heart&rsquo;s structure and function.</li>
	<li>ECG - This measures the electrical activity of the heart. 
	&nbsp;</li>
</ul>

Other Tests

The following tests can also help detect the underlying cause of ARDS:

<ul>
	<li>Sputum culture</li>
	<li>Bronchoscopy</li>
	<li>Urine tests 
	&nbsp;</li>
</ul>

As per the Berlin Definition of ARDS, all of the following criteria must be present for the diagnosis of ARDS<a href="#accordion">[9]</a>.

<ul>
	<li>Respiratory symptoms began within one week of a known disease, or the patient experienced new or worsening symptoms in the past week.</li>
	<li>Chest X-ray or CT scan reveals bilateral opacities. Lobar collapse, lung collapse, pleural effusions, or pulmonary nodules must not be a cause of the opacities.</li>
	<li>The respiratory failure is not explained by fluid overload or heart failure.</li>
	<li>&nbsp;Presence of moderate to severe oxygen impairment. 
	&nbsp;</li>
</ul>

Treatment

There is no cure for ARDS as such. Treatment is mostly supportive and focuses on increasing oxygen delivery, decreasing oxygen consumption, and preventing any further injury. 
&nbsp;

<h5>Ventilator Support</h5>

All ARDS patients require additional oxygen. Oxygen alone is generally insufficient, and too much oxygen can be harmful to the lungs. Mechanical ventilation pushes air into the lungs and widens the closed airspace, forcing fluid out of the alveoli. 
&nbsp;

<h5>Prone Positioning </h5>

When oxygen and ventilator therapies are at high levels and blood oxygen is still low, ARDS patients are sometimes turned over on their stomachs to get more oxygen into the blood. This is known as proning, and it may temporarily boost oxygen levels in the blood. It is a difficult task, and some patients are too unwell for it. 
&nbsp;

<h5>Sedation And Medication To Prevent Movement</h5>

Sedation is generally required for ARDS patients to ease shortness of breath and avoid agitation. Sometimes additional drugs, known as paralytics are required to assist the patient to acclimatize to the ventilator. These drugs have substantial adverse effects, and their risks and benefits must be assessed on a constant basis. Patients are also advised to have medications to combat the following issues, such as:

<ul>
	<li>Infections</li>
	<li>Pain and discomfort</li>
	<li>Clots in legs and lungs</li>
	<li>Gastric reflux 
	&nbsp;</li>
</ul>

<h5>Fluid Management</h5>

Doctors may give ARDS patients diuretics to induce urine production and eliminate excess fluid from the body, preventing fluid buildup in the lungs. This must be done with caution since excessive fluid evacuation might reduce blood pressure and create renal issues. 
&nbsp;

<h5>Extracorporeal&nbsp;Membrane Oxygenation (ECMO) </h5>

ECMO is a complex procedure that separates blood from your body and pumps it across a membrane that adds oxygen, eliminates carbon dioxide and returns the blood to your body. This is a high-risk treatment with several possible side effects. It is not appropriate for every ARDS patient. 
&nbsp;

<h5>Pulmonary&nbsp;Rehabilitation </h5>

Exercise training, physiotherapy, lifestyle classes, and support teams can help strengthen the respiratory muscle and increase lung capacity. Thus, helping patients recover from ARDS. 
&nbsp;

<h5>Recovery From ARDS</h5>

ARDS patients may require ventilation for long periods of time, on average 7 to 14 days. In some cases, a tracheostomy may be advised to aid the patient in breathing. This tube can easily be removed once the patient is free of the need for a ventilator. 
&nbsp;

In rare situations, an ARDS diagnosis might cause or be connected to other health problems that must be treated. Complications may include:

<ul>
	<li>Multiple organ failure</li>
	<li>Pulmonary hypertension (increase in blood pressure)</li>
	<li>Blood clots that develop during therapy&nbsp;</li>
	<li>Atelectasis (collapse of the lung&rsquo;s small air pockets)</li>
	<li>Post-traumatic stress disorder (PTSD)</li>
	<li>Depression and anxiety</li>
	<li>Muscle weakness 
	&nbsp;</li>
</ul>

Note: Not everyone develops complications. However, certain populations are more vulnerable. For example, males diagnosed with ARDS may be more likely than women to develop complications from the illness. 
&nbsp;

The majority of individuals who get ARDS are already in the hospital for another reason, and many are critically ill. The following increases one&#39;s risk of ARDS:

<ul>
	<li>Sepsis</li>
	<li>People with a history of persistent drinking are more likely to develop ARDS. They&#39;re also more susceptible to dying of ARDS&nbsp; &nbsp;</li>
	<li>Older age (specifically above 65)</li>
	<li>Presence of chronic lung disease 
	&nbsp;</li>
</ul>

There are currently no measures to prevent ARDS. You may, however, be able to reduce your risk of ARDS by doing the following: 
&nbsp;

<ul>
	<li>Seek immediate medical attention if you have suffered a trauma, infection, or disease</li>
	<li>Quit smoking</li>
	<li>Quit consumption of alcohol. Chronic alcohol usage may raise your risk of death and impair lung function.</li>
	<li>Get your flu vaccine every year, and your pneumonia vaccine every five years. This reduces your chances of getting a lung infection. 
	&nbsp;</li>
</ul>

Key Points

<ul>
	<li>Acute respiratory distress syndrome (ARDS) is a potentially fatal lung infection caused by sepsis, pneumonia, the coronavirus (COVID-19), and other serious conditions.</li>
	<li>ARDS often develops within hours to days following the triggering event and can progress rapidly. Patients with ARDS may need to be admitted to an intensive care unit (ICU) and placed on a ventilator to assist them to breathe.</li>
	<li>Respiratory illness or injury can damage the protective membranes between the alveoli and blood vessels. This results in blood and fluid leaking from the blood vessels into and between the air sacs. The presence of fluid disrupts the exchange of gases; thus, decreasing the level of oxygen in the blood.</li>
	<li>Clinical manifestations may include breathing difficulties (dyspnea), rapid breathing (tachypnea), excessively deep and rapid breathing (hyperventilation), and hypoxemia.</li>
	<li>ARDS is classified into three levels: mild, moderate, and severe.</li>
	<li>Diagnosis is based on clinical manifestations, imaging scans, and laboratory studies.&nbsp;</li>
	<li>The purpose of supportive treatment is to get enough oxygen into your bloodstream and transport it to your body in order to avoid harm and treat the injury that caused ARDS to occur.</li>
	<li>ARDS patients may require ventilation for long periods of time, on average 7 to 14 days. 
	&nbsp;</li>
</ul>

[1] Eloise M Harman MD. Acute respiratory distress syndrome (ARDS). Background, Pathophysiology, Etiology.

[2] Ards. Mayo Clinic.

[3] Acute respiratory distress syndrome (ARDS): Definition, symptoms, and treatment. WebMD.

[4] Allen S. Ards: Causes, symptoms, risks, diagnosis, and treatment. Healthline.

[5] Acute respiratory distress syndrome (ARDS): Symptoms, treatment. Cleveland Clinic.

[6] Patel BK. Acute respiratory distress syndrome (ARDS) - lung and airway disorders. MSD Manual Consumer Version.

[7] Association AL. Diagnosing and treating Ards. American Lung Association.

[8] Acute respiratory distress syndrome. NORD (National Organization for Rare Disorders).

[9] UpToDate.

[10] What is acute respiratory distress syndrome? National Heart Lung and Blood Institute.

[11] Diamond M, Peniston HL, Sanghavi D, et al. Acute Respiratory Distress Syndrome. [Updated 2022 Oct 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-

[13]  Baqi S, Naz A, Sayeed MA, et al. Clinical characteristics and outcome of patients with severe COVID-19 pneumonia at a Public Sector Hospital in Karachi, Pakistan. Cureus. 2021. doi:10.7759/cureus.13107

[12] Tolossa T, Merdassa Atomssa E, Fetensa G, et al. Acute respiratory distress syndrome among patients with severe COVID-19 admitted to treatment center of Wollega University Referral Hospital, Western Ethiopia. PLOS ONE. 2022;17(6). doi:10.1371/journal.pone.0267835.