Transpulmonary Pressure At the same driving force applied to the whole respiratory system (lung and chest wall), the resulting transpulmonary pressure, ΔPL, may be extremely variable. If the lung is relatively “stiff,” and the chest wall is relatively “soft” (e.g., during pulmonary fibrosis or ARDS of pulmonary origin), a greater fraction of the driving pressure is spent to distend the lung (high transpulmonary pressure). In contrast, if the lung is relatively soft, but the chest wall is relatively stiff (e.g., during an abdominal disease or severe obesity), most of the driving force is spent to move the chest wall (high pleural pressure). To express this phenomenon quantitatively, it is convenient to consider the concept of elastance. The elastance of the whole respiratory system is the driving force (ΔPaw) required to increase the lung and the chest wall 1 L above their resting position (ETOT = ΔPaw/1 L). Part of this driving force is spent to increase the lung volume of 1 L (EL = ΔPL/1L), and part is spent to increase the chest wall by the same amount (ECW = ΔPpl/1 L). Transpulmonary pressure (ΔPL) can be expressed as the driving force times the ratio between lung elastance and total elastance of the respiratory system: ΔPL = ΔPaw × EL/ETOT The transpulmonary pressure for a given driving pressure uniquely depends on the ratio of lung elastance to respiratory system elastance. In normal subjects EL/ETOT is approximately 0.5, whereas in patients with ARDS it may range from 0.2 (e.g., in obese patients or in patients with high intra-abdominal pressure) to 0.8 (e.g., in patients with a very small baby lung and a normal chest wall elastance). This variability implies that for the same driving force applied and read on the ventilator display (e.g., 30 cm H2O), the resulting transpulmonary pressure may range from 6 to 24 cm H2O (Fig. 11-1).
|Titolo:||The assessment of transpulmonary pressure in mechanically ventilated ARDS patients|
GATTINONI, LUCIANO (Primo)
|Data di pubblicazione:||9-mag-2015|
|Settore Scientifico Disciplinare:||Settore MED/41 - Anestesiologia|
|Citazione:||The assessment of transpulmonary pressure in mechanically ventilated ARDS patients / L. Gattinoni. ((Intervento presentato al 20. convegno International Intensive Care Symposium tenutosi a Istanbul nel 2015.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|