ARDS (Acute Respiratory Distress Syndrome)

• Acute respiratory distress syndrome (ARDS) is an acute, life-threatening condition that develops within seven days after lung injury.
• In ARDS, fluid accumulates in the alveoli and surfactant in the lungs breaks down, leading to stiff lungs and insufficient oxygen distribution throughout the body.

ARDS Development and Lung Damage

• The condition starts with alveolar-capillary damage, resulting in fibrotic tissue development.
• Cellular damage to the pulmonary epithelium involves inflammation, apoptosis, necrosis, and increased alveolar-capillary permeability.
• These damages induce edema in the alveoli, which impairs gas exchange and causes hypoxemia.
• Lung damage patterns are inconsistent, so positive-end expiratory pressure (PEEP) may variably help damaged cells, while potentially harming healthier cells through atelectrauma and volutrauma.
• ARDS may be unresponsive to oxygen if healthier cells take up the oxygen, leaving damaged cells without use.

Physiological Effects of ARDS

• Lung injury from ARDS leads to altered gas exchange, decreased lung expansion, and increased pulmonary arterial pressure.
• Impaired gas exchange results from a V/Q mismatch due to shunting and dead space; shunting causes hypoxemia, while dead space impairs carbon dioxide elimination.
• Decreased pulmonary compliance develops because of the stiffness of a poorly aerated lung.

Causes and Risk Factors

• Common causes of ARDS include sepsis, pneumonia, and aspiration.
• Sepsis is the most common cause, with the risk highest among clients who are septic and have alcohol use disorder (70% incidence).
• Community-acquired pneumonia (CAP) is a common cause in hospitalized individuals.
• Approximately 15% of ICU clients and 23% of those mechanically ventilated meet ARDS criteria.
• 80% of all clients with ARDS need mechanical ventilation, and 25% may develop pulmonary hypertension.
• Risk factors for ARDS include being female, age over 60, trauma, drowning, drug overdose, traumatic brain injury, recent cardiac surgery, smoking, and excessive alcohol use.

Prevalence and Outcomes

• ARDS affects approximately 3 million clients worldwide and is associated with 10% of ICU admissions and 24% of clients needing mechanical ventilation.
• ARDS has a mortality rate of 27% to 45%, depending on severity, resulting in roughly 75,000 deaths annually in the U.S.
• Long-term effects include muscle wasting, weight loss, functional impairment, and cognitive loss from extended hypoxia.
• Post-treatment, clients might be discharged with a tracheostomy and/or gastric tube and report exertional dyspnea and exercise intolerance.

Manifestations and Diagnosis

• Common manifestations of ARDS include progressively worsening dyspnea within 6 to 72 hours of the inciting event.
• Physical examination reveals respiratory distress symptoms like tachycardia, tachypnea, and diffuse crackles.
• Severe cases manifest as somnolence, cyanosis, and diaphoresis.
• The hypoxic state caused by ARDS doesn't respond to oxygenation, often necessitating mechanical ventilation.
• Diagnosis relies on the Berlin criteria: onset within seven days of an event, noncardiac origin, bilateral lung infiltrates on imaging, and abnormal oxygenation measurements.
• A PaO2/FiO2 ratio of less than 300 mm Hg confirms the diagnosis, with severity (mild, moderate, severe) determined by this ratio during mechanical ventilation.
• The PaO2/FiO2 ratio is the partial pressure of arterial oxygen to a fraction of inspired oxygen, and it indicates oxygenation status.

PaO2/FiO2 Ratio

• Normal circumstances (PaO2 85-100 mm Hg; FiO2 0.21) should result in a P/F ratio greater than 400 (e.g., 95/0.21 = 452).
• Mild ARDS: P/F ratio less than 300
• Moderate ARDS: P/F ratio less than 200
• Severe ARDS: P/F ratio less than 100

Nursing Role and Interprofessional Care

• Nurses play a crucial role in managing clients with ARDS, beyond basic care and monitoring.
• Continuously assess lab results for trends indicative of sepsis or renal failure, and thoroughly assess skin condition for alterations or pressure ulcers.
• Nurses coordinate care among specialists such as intensivists, pulmonologists, nephrologists, respiratory therapists, physical therapists, dietitians, and pharmacists.
• The client receives continuing care in an ICU environment, following the evidence-based ABCDEF Critical Care Bundle.

Assessment and Data Analysis

• ARDS requires astute assessment skills, focusing on respiratory symptoms like dyspnea, tachypnea, and low oxygen saturation (that does not respond to supplemental oxygen).
• Lung sounds may reveal rales, and heart sounds may indicate tachycardia.
• Assess for hypoxemia signs like central or peripheral cyanosis and altered mental status.
• Monitor vital signs for hypotension (indicating compromised cardiac output) and elevated temperature (indicating infection).
• Obtain a history from the client or family to identify the underlying cause of the manifestations.
• Analyze collected data to recognize respiratory compromise and fluid in the lungs.
• Review lab assessments (CBC, CMP, cardiac enzymes) and diagnostic exams to identify abnormalities and the ARDS causative factor.
• For intubated clients, analyze tube placement, ventilator settings, and response to the ventilator, listen bilaterally for lung sounds, and check the capnography monitor for pCO2.
• Be alert to compounding manifestations of underlying diseases, such as heart failure/left ventricular dysfunction, and abnormal lab trends which can indicate multi-organ failure.
• Monitor for signs of delirium.

Priorities of Care

• The priority of care for clients with ARDS is to provide ventilatory assistance and supportive care.
• The main goal is to increase oxygenation, decrease shunt fraction, reduce oxygen consumption, and prevent additional lung injury.
• Lung-protective ventilation should be adhered to and monitored.
• Priorities include hemodynamic stability, suctioning, pain management, and sedation.
• Respiratory and cardiac monitoring is frequent, and suctioning is performed to clear secretions.

Treatment Strategies

• It is important to treat the underlying cause of ARDS, such as an infection or inflammatory process.
• Implement hemodynamic monitoring to intervene with fluid balance and cardiovascular needs.
• Respiratory care includes oxygen administration to correct hypoxemia and mechanical ventilation to prevent alveoli overdistention.
• Low tidal volumes can prevent barotrauma and volutrauma and have shown to reduce mortality.

Collaborative Planning and Interventions

• Collaborate with the healthcare team to improve client outcomes and gas exchange.
• Reposition the client into a prone position to modify the distribution of transpulmonary pressure.
• Plan interventions to avoid VAP, and implement the ABCDEF bundle, focusing on ventilator weaning.
• Adjustments to maintain stability should be made based on venous oximetry, oxygenation levels, and vital signs.
• Higher levels of PEEP and lower tidal volumes may be required to meet oxygenation needs.
• Suction to remove secretions assists in creating a well-perfused alveolar space.
• Administer prescribed medications to address underlying causes, relieve manifestations, and prevent complications.
• Fluid management and feeding tube administration ensure adequate nutrition.
• Implement actions to prevent VAD, such as oral hygiene, passive range of motion exercises, and DVT prophylaxis.

Client and Family Education

• Educate clients and families on potential issues during treatment.
• Keep them aware of the client’s improvement and possible complications after recovering from ARDS.

Prone Positioning

• Fluid can move within the lungs during ARDS, depending on the client's position; gravity causes fluid to pool.
• Prone positioning is considered when clients do not respond to other strategies.
• There is more lung surface area on the back side of the lungs.
• Prone positioning may allow a reduction in PEEP and FiO2.
• Some clients may not tolerate prone positioning, which may cause dysrhythmias and decreased BP.
• Prone positioning in the early phases of ARDS generally yields the best results.
• Clients can remain in the prone position for 16 hours per day.
• The process to place a client in the prone position requires 3-4 nurses while giving special attention to securing the client’s airway and monitoring other lines and tubes.

Expected Outcomes

• Maintenance of adequate gas exchange, an alert mental status, and relaxed breathing.
• Resolution of the ARDS precipitating cause and ventilator weaning.
• Absence of pain/anxiety and delirium, and engagement in increased mobility.

Interventions if Goals are Not Met

• If the client’s condition does not improve or client outcomes are not met, the nurse and interprofessional team will need to re-evaluate the goals and interventions with a new plan of care created to increase oxygen delivery.

Additional Considerations

• Clients who are mechanically ventilated will likely require administration and management of sedation and neuromuscular blockers (NMB).
• Most clients with ARDS need a high fraction of inspired oxygen (FiO2), particularly when pulmonary edema is severe in the early stages.
• Uncontrolled oxygen supplementation could result in oxygen toxicity, a high volume causing illness, and CO2 narcosis.

This quiz covers key aspects of Acute Respiratory Distress Syndrome (ARDS), including the varied results of PEEP, factors contributing to decreased lung expansion, the relationship between V/Q mismatch and ARDS, common underlying causes, the need for mechanical ventilation, and factors contributing to hypoxemia.