ventilation perfusion inequality shunt vs dead space

Such unstable lung units may be “re-opened” (recruited) with increasing airway pressure. These derangements are due, in part, to the inflammatory milieu caused by the primary etiologic factor, but mechanical ventilation alone is capable of decreasing surfactant levels in broncho-alveolar lavage fluid obtained from patients even in the absence of lung injury. Decreased surfactant production and abnormal pressure due to the superimposed weight of the edematous lung contribute to alveolar instability and atelectasis, which have been associated with more severe lung injury and mortality. Non-aerated lung tissue may arise due to alveolar instability and collapse. The genesis of these non-ventilated lung zones is multifactorial. used multiple inert gas elimination to study 16 patients with severe ARDS and demonstrated that nearly 50% of the cardiac output was distributed to pure shunt or very low V/ Q lung zones, thus entirely explaining the observed hypoxemia. The perfusion of collapsed or consolidated lung units gives rise to intrapulmonary shunting and arterial hypoxemia, whereas the ventilation of non-perfused lung zones increases physiological dead-space, which potentially necessitates increased ventilation to avoid hypercapnia.Īrterial hypoxemia due to an intra-pulmonary shunt is a hallmark clinical problem.

In patients with ARDS, disturbances in the physiological matching of alveolar ventilation (V) and pulmonary perfusion (Q) ( V/ Q mismatch) are a hallmark derangement. It is being increasingly demonstrated that the improvement of outcomes requires a tailored, individualized approach to therapy, guided by a detailed understanding of each patient’s pathophysiology.

Acute respiratory distress syndrome (ARDS) remains an important clinical challenge with a mortality rate of 35–45%. Acute respiratory distress syndrome (ARDS) is a heterogenous condition that is characterized by the development of inflammatory pulmonary edema and life-threatening hypoxemia, and it accounts for nearly 25% of patients who require mechanical ventilation.

Ventilation perfusion inequality shunt vs dead space