All of the following features can seen in ARDS except:
Answer is D (Hypercapnia): Respiratory failure and is characterized by normal or low PaCO2 (Hypocapnia) and not hypercapnia. Pulmonary Shunting: Significant shunt occurs in ARDS where pulmonary aerial blood shunts past flooded and collapsed Alveoli into pulmonary veins. Shunting of the poorly oxygenated venous blood into aerial circulation significantly contributes to aerial hypoxemia. Reduced compliance: Reduced lung compliance and stiff lung are characteristic features of ARDS Hypoxemia: Aerial hypoxemia is a characteristic feature of ARDS and may be caused by reduced lung compliance and pulmonary shunting. Features of ARDS Clinical /Physiological Clinical history of insult known to cause ARDS Clinical exclusion of chronic lung disease and Left ventricular failure Diffuse alveolar damage. Reduced surfactant (Injury to type II pneumocytes) Increased permeability of alveolar capillary membrane. Accumulation of proteinaceous pulmonary edema (non cardiogenic pulmonary edema Q) Pulmonary edema + Hyaline membrane (fibrin + coagulated cell debris) Reduced compliance (stiff lung) Diminished tidal volume HypoxemiaQ (Worsened gas exchange d/t pulmonary shunting) Hypocapnia Q(CO2 washout) Diagnostic Criteria (ARDS) PaO2/FiO, 5200 mm Hg Onset Acute Chest Radiograph Bilateral Alveolar or Interstitial infiltrates Absence of Left Atrial Hypeension * PCWP18 mmHg * No clinical evidence of increased left atrial pressure
Pulmonary Shunting
Reduced compliance
Hypoxemia
Hypercapnia