I dont like the Berlin ARDS definition - The International Fluid Academy
PaO2 = 5 x FIO2 % = GOOD (Perfect lungs). PaO2 = 4 x FIO2 % = OK (Low normal lungs). PaO2 = 3 x FIO2 % = POOR (Moderate lung dysfunction). PaO2 = 2 x. Pop Quiz If we breathe The Clinical Oxygenation Puzzle. PO. 2. SaO2. SpO2. FIO2. Rocket Science? .. This PO2/SaO2 relationship is direct but not linear. The absolute levels of PaO2 and PaCO2 that initial diagnosis (e.g. ARDS if PaO2/FIO2 ratio. kPa) linear nature of the relationship between oxygen tension and hae- benchmark by which other tests are assessed.5 This is a ' content-.
Identify the factors that affect oxygen loading and unloading from hemoglobin. Describe how carbon dioxide is carried in the blood.
Easy blood gas quiz with answers, by Lawrence Martin, MD
Describe how oxygen and carbon dioxide transport are interrelated. Describe the factors that impair oxygen delivery to the tissues and how to distinguish among them. State the factors that impair carbon dioxide removal.
In lungs it is diluted by water vapor and CO2. Alveolar air equation accounts for all these factors: This ratio is normally 0. N2 is inert but occupies space and exerts pressure. The greater the surface area, diffusion constant, and pressure gradient, the more diffusion will occur. Pulmonary diffusion gradients Diffusion occurs along pressure gradients.
Time limits to diffusion: Pulmonary blood is normally exposed to alveolar gas for 0.
Factors affecting oxygen loading and unloading Besides the shape of the HbO2 curve, many factors affect O2 loading and unloading. Low pH shifts curve to right, high pH shifts to left. Decreased T shifts the curve left. Moreover this ratio also depends on the level of positive end-expiratory pressure PEEP used. Finally, as pointed out by LeTourneau et al.
Towards a new definition for ALI and ARDS Although not a bedside technique, the CT scan is often performed in patients with acute respiratory failure and is dramatically useful to characterize the lung disease process bilateral or not, patchy or posterior condensationsto quantify pleural effusion, as well as to assess lung recruitment induced by PEEP or other maneuvers.
As suggested by LeTourneau et al. Although TPTD is useful to assess hemodynamic parameters  and detect right-to-left intracardiac shunts , it is not yet standard of care. The use of TPTD requires a central venous catheter for cold bolus injections the thermal indicator and a central usually femoral thermistor-tipped arterial catheter to record thermodilution curves.
The use of femoral arterial catheters remains today an exception in the US. The reasons for that are unclear since complications are rare  and may not be more frequent than with radial catheters.
Moreover, the femoral arterial pressure is well known to give a better estimate of central pressure, particularly in septic patients . If most patients with severe ARDS are frequently instrumented with an arterial line and a central venous line, it is usually not the case at a early stage of lung inflammation. TPTD measurements also allow to calculate the pulmonary vascular permeability index PVPI which allows stratification into hydrostatic versus permeability lung edema .
Finally, as already suggested by others  it might also be wise to integrate FiO2 in the definition. A recent study suggests that adding PEEP to the definition would not help . We believe this definition has the advantage to be simple and to take into account the clinical and physiological information most clinicians have access to when treating patients with acute respiratory failure in Viral or bacterial pneumonia b.
Fraction of inspired oxygen
Gastric or smoke inhalation c. Pancreatitis or severe burns or severe sepsis or septic shock c. Bilateral consolidations on chest CT scan The need for a.
Definitions, mechanisms, relevant outcomes, and clinical trial coordination. Acute respiratory distress syndrome: Respiratory monitoring in the ICU - a consensus of Critical care London, England16 2: Crit Care Med40 3: Extravascular lung water predicts progression to acute lung injury in patients with increased risk. Factors influencing the estimation of extravascular lung water by transpulmonary thermodilution in critically ill patients. Crit Care Med33 6: Measurement of pulmonary edema in patients with acute respiratory distress syndrome.
Crit Care Med33 Accuracy of transpulmonary thermodilution versus gravimetric measurement of extravascular lung water. Crit Care Med32 7: Validation of extravascular lung water measurement by single transpulmonary thermodilution: Crit Care14 5: Small increases in extravascular lung water are accurately detected by transpulmonary thermodilution.Oxygen content - Human anatomy and physiology - Health & Medicine - Khan Academy
J Trauma59 6: A Randomized Placebo-controlled Clinical Trial. Fluid management in critically ill patients: The role of extravascular lung water, abdominal hypertension, capillary leak and fluid balance. Annals Intensive Care2 Supplem 1: Extravascular lung water in sepsis-associated acute respiratory distress syndrome: Crit Care Med36 1: Comparative diagnostic performances of auscultation, chest radiography, and lung ultrasonography in acute respiratory distress syndrome.