ARDS Symptoms: How to Spot and Treat the Ailment

• Acute respiratory distress syndrome is the most severe form of lung injury, and it’s important to know the ARDS symptoms. 
• ARDS usually results from a sudden, catastrophic event that causes a lung injury. 
• The treatment of ARDS lies in treating the underlying cause and supporting the respiratory function.  

Acute respiratory distress syndrome or ARDS, is the most severe form of lung injury. It is defined as noncardiogenic pulmonary edema, in which the lung capillary pressure remains low to average.   

In ARDS, pulmonary edema ensues, compromising the functionality of the lungs. However, this edema is not due to heart failure.   

Several hypotheses have been offered regarding the mechanism of ARDS. Pulmonary edema in ARDS is high-permeability pulmonary edema (HPPE), in contrast to cardiogenic edema due to increased pressure in the lung capillaries. The edema is usually accompanied by multiple organ failures.   

In ARDS, the damaged alveolar-capillary membrane becomes leaky, allowing fluid and protein to leak, resulting in edema.   

Causes of ARDS

ARDS usually results from a sudden, catastrophic event that causes a lung injury. The mechanism of injury can be direct or indirect. Direct lung injury occurs because of conditions like gastric acid aspiration, chemical inhalation, near drowning, or oxygen toxicity. 

With indirect injuries, mediators released in overwhelming stress to the body cause damage to the lung tissue, such as during sepsis; multiple traumas; thermal injury; hypoperfusion or hemorrhagic shock; disseminated intravascular coagulation; drug overdose; and massive blood transfusions. Sepsis from an abdominal source is the most common risk factor for ARDS.  

Other causes of ARDS include pancreatitis, acute liver failure, trauma, head injury, malaria, fat embolism, burns, obstetric events like eclampsia or amniotic fluid embolism, and drugs or toxins like aspirin, heroin, and paraquat.  

What Happens in Acute Respiratory Distress Syndrome?

Researchers have emphasized various mediators that play a role in ARDS-related lung damage, such as neutrophils, tumor necrosis factor (TNF), bacterial toxins, and oxygen-free radicals.   

Upon progression of ARDS, the lungs show markedly decreased volume, and lung compliance also falls. Type II pneumocytes that produce surfactant are damaged. The resulting surfactant deficiency is thought to play a role in the alveolar collapse, which causes decreased lung volume and compliance in ARDS.  

Furthermore, fibroblasts migrate into the alveolar space and convert the alveolar fluid (rich in protein and debris) into fibrous tissue. The ensuing fibrosis results in capillary shunting and refractory hypoxemia. As ARDS progresses further, respiratory failure and cardiopulmonary arrest can develop.  

Clinical Assessment of a Patient with ARDS

History: As mentioned earlier, ARDS usually occurs as a response to overwhelming stress on the body, which may involve the lungs directly or indirectly. Your patient might have a history of such an event that led to ARDS. In patients with ARDS, there is a history of shortness of breath and increased effort needed to breathe.  

Physical Examination: Patients with ARDS appear in respiratory distress and tachypneic. There is a marked increase in breathing work, and nasal flaring and the use of accessory muscles may be noticed. The respiratory rate might be more than 30 to 40 breaths per minute, and the patient might have profound diaphoresis. In advanced stages of ARDS, the patient could have cyanosis around the lips and nail beds or appear pale with a dusky complexion.  

Hypoxemia due to ARDS leads to restlessness, agitation, and confusion.  

Other examinations and their findings are given in the table below: 

Diagnosis Of ARDS: ARDS is usually diagnosed through exclusion. The American-European Consensus Conference (AECC) has defined the diagnostic criteria for ARDS as a patient presenting with the following four features:  

1. Acute Onset
2. Bilateral infiltrates on Chest X-ray
3. Absence of clinical congestive heart failure or pulmonary capillary wedge pressure (PCWP) <19mmHg  
4. Refractory hypoxemia with PaO2: FiO2 <200  

Additional investigations may help reinforce the diagnosis of ARDS, as mentioned in the table below.

Management of ARDS

The treatment of ARDS involves treating the underlying cause and supporting respiratory function. The patient should be admitted to the ICU and given supportive treatment.   

Respiratory Support: In the early stages of ARDS, a continuous positive airway pressure (CPAP) with 40% to 60% oxygen may suffice to provide adequate oxygenation to the patient. However, most patients need endotracheal intubation with mechanical ventilation for respiratory support. The indication for mechanical ventilation is PaO2: less than 8.3kPa despite 60% Oxygen and PaCO2: >6kPa.  

Various positive-pressure modes are used on the mechanical ventilator to manage ARDS. One usual mode includes pressure-controlled ventilation with an inverse inspiratory-expiratory ratio. This mode prolongs the inspiratory time by setting this ratio to 1:1. The standard respiratory inspiratory-expiratory ratio ranges from 1:2 to 1:3. In standard respiration in ventilators, the expiration takes twice or thrice the time of inspiration. Doctors aim to stabilize the alveoli and to reestablish the functional residual capacity (FRC) to normal levels by prolonging the expiratory time in patients with ARDS. 

Using pressure-controlled modes also helps keep pressures within acceptable range and prevent the damaging effects of excessive airway pressures in patients with ARDS. This technique has shown positive outcomes. A patient with ARDS is susceptible to pneumothorax if the ventilator is set on volume-controlled mode due to high pressures building up within the lung, along with poor compliance. Therefore, a pressure-controlled mode is preferred in patients with ARDS.   

Some physicians aim to keep FiO2 below 50% to prevent oxygen toxicity.  

Circulatory Support: An invasive method for hemodynamic monitoring, such as an arterial line or Swan–Ganz catheter, can be used. A Swan–Ganz catheter can help establish the diagnosis and monitor the pulmonary capillary wedge pressure (PCWP).  

A conservative fluid management approach improves outcomes. Cardiac output should be maintained by inotropic support like dobutamine. Improve oxygen delivery by administering a vasodilator like nitric oxide. Sometimes, a blood transfusion may be warranted. In patients with renal failure, hemodialysis may be needed to achieve a negative fluid balance.   

Infection Management: If the patient is considered septic, identify organisms and treat them accordingly. If no organisms are cultured, but the patient shows clinical signs of sepsis, a broad-spectrum antibiotic should be started. Avoid using nephrotoxic drugs.   

Nutrition: Maintain good nutritional intake of the patient. It is best to give enteral feeding. A nasogastric tube can be used to feed patients.   

Outcome of ARDS: The mortality rate of ARDS is high, ranging from 35% to 45%. The outcomes vary with the age of the patient and the underlying cause. For example, patients who have ARDS due to pneumonia have a significantly higher mortality rate than those who have ARDS due to trauma. Several organs involved also define the prognosis. Three or more organs involved for more than one week is invariably fatal.   

Nursing Care: As a nurse, you should keep the following aspects in mind while caring for your patient with ARDS:  

1. Endotracheal suctioning should be done after intervals to aid oxygenation. It is recommended to hyper oxygenate and hyperventilate the patient before starting suctioning to prevent the adverse effects of suctioning, like hypotension or cardiac dysrhythmias.
2. Change the patient’s position every hour to encourage oxygen to all areas of the lung. If the oxygenation is poor, a rocking bed may be considered to change the patient’s position continuously. A prone position also helps in better oxygenation.
3. Help the patient mobilize as soon as possible. Get them out of bed even if they are intubated.
4. Use soft restraints in patients that can extubate.
5. A skeletal muscle relaxant like cisatracurium or vecuronium may be used in patients with difficulty ventilating or preventing self-extubation in agitated patients. These drugs paralyze the patient, so the patient should also be sedated to avoid the overwhelming anxiety of muscle paralysis.
6. In sedated patients, use artificial tear drops periodically to moisten the eye as the blink reflex is lost. Provide passive range-of-motion exercises every 8 hours to prevent contractures. Turn the patient at least every 2 hours for comfort, adequate gas exchange, and pressure sores.
7. Provide complete hygiene to the patient, including mouth care.
8. Space all activities to limit oxygen consumption.
9. Provide your patient with a quiet and uninterrupted environment to rest.
10. Your patients and their attendants may be tense and anxious. Reassure them while making them aware of the reality of the ground. Do not give false hopes to console them. Address the questions of the people involved and help the patient communicate with their relatives by different methods, such as using a whiteboard. 

The Bottom Line

ARDS is the most severe form of lung injury with a significant mortality rate. Your patient with ARDS may most likely require endotracheal intubation with mechanical ventilation. Your role as a nurse is essential in taking care of your patients and providing them with emotional support through this overwhelming journey. 

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