Symptoms and Physical Findings in Acute Respiratory Distress Syndrome (ARDS)
The accurate description of symptoms and physical findings in ARDS is the absence of intravascular overload, as ARDS is characterized by non-cardiogenic pulmonary edema with bilateral infiltrates that cannot be fully explained by cardiac failure or fluid overload. 1, 2
Key Clinical Manifestations of ARDS
Respiratory Symptoms and Signs
- Patients with ARDS present with rapidly progressive dyspnea and tachypnea (not bradypnea) due to the inflammatory response and decreased lung compliance 2
- Bilateral crackles are typically present on auscultation due to alveolar flooding with plasma proteins and inflammatory exudate 1, 2
- Hypoxemia is the predominant symptom, which is profound and often refractory to supplemental oxygen 3
Cardiovascular Manifestations
- Tachycardia (not bradycardia) is commonly observed as a compensatory mechanism for hypoxemia and as part of the systemic inflammatory response 2
- Hypotension is more common than hypertension, particularly in cases associated with sepsis, which is one of the most common causes of ARDS 1, 2
- Shock may be present, especially when ARDS is associated with sepsis or other systemic inflammatory conditions 2
Fluid Status Assessment
- By definition, ARDS involves non-cardiogenic pulmonary edema with absence of intravascular overload 1, 2
- The Berlin criteria specifically state that respiratory failure cannot be fully explained by cardiac failure or fluid overload 4
- Distinguishing ARDS from cardiogenic pulmonary edema is crucial, as the latter typically shows signs of fluid overload that are absent in ARDS 2
Pathophysiological Basis
- ARDS involves alveolar epithelial inflammation, increased pulmonary capillary leakage, and loss of normal endothelial reactivity 1
- The inflammatory response includes neutrophil activation, cytokine release, and oxidant stress leading to damage of the vascular endothelium and alveolar epithelium 1, 2
- This damage results in pulmonary edema despite normal or low intravascular pressures, distinguishing it from cardiogenic pulmonary edema 2, 3
Diagnostic Considerations
- Diagnosis requires onset within one week of a known insult or new/worsening respiratory symptoms 2
- Bilateral pulmonary opacities must be present on chest imaging 1, 2
- PaO₂/FiO₂ ratio ≤ 300 mmHg with minimum PEEP of 5 cmH₂O is required 1
- Respiratory failure cannot be explained by cardiac failure or fluid overload 1, 2
Clinical Implications
- Recognition of the absence of intravascular overload is crucial for proper management, as fluid management strategies differ between ARDS and cardiogenic pulmonary edema 1
- A conservative fluid management strategy should be implemented once shock is resolved to avoid worsening pulmonary edema 1
- Monitoring right ventricular function is important as ARDS can be complicated by right ventricular dysfunction due to increased pulmonary vascular resistance 1
Based on the evidence presented, the correct answer is D: Absence of intravascular overload, as this is a defining characteristic of ARDS that distinguishes it from cardiogenic pulmonary edema.