Type L: - Low elastance. The nearly normal compliance indicates that the amount of gas in the lung is nearly normal - Low ventilation-to-perfusion (VA/Q) ratio. Since the gas volume is nearly normal, hypoxemia may be best explained by the loss of regulation of perfusion and by loss of hypoxic vasoconstriction. Accordingly, at this stage, the pulmonary artery pressure should be near normal. - Low lung weight. Only ground-glass densities are present on CT scan, primarily located subpleurally and along the lung fissures. Consequently, lung weight is only moderately increased. - Low lung recruitability. The amount of non-aerated tissue is very low; consequently, the recruitability is low Type H: - High elastance. The decrease in gas volume due to increased edema accounts for the increased lung elastance. - High right-to-left shunt. This is due to the fraction of cardiac output perfusing the non-aerated tissue which develops in the dependent lung regions due to the increased edema and superimposed pressure. - High lung weight. Quantitative analysis of the CT scan shows a remarkable increase in lung weight (> 1.5 kg), on the order of magnitude of severe ARDS. - High lung recruitability. The increased amount of non-aerated tissue is associated, as in severe ARDS, with increased recruitability. Dr. Giuseppe Citerio @Dr_Cit #COVID19 #Phenotypes #Variations #Diagnosis #Management #SARSCOV2 #Coronavirus
