Changes in intrathoracic pressure will directly alter CVP and may create a vascular waterfall between extrathoracic CVP and Pra. Commonly, during forced inspiration, especially against an inspiratory airflow resistor (e.g., constricted bronchi in asthma) or if lung parenchymal tissue is stiff (e.g., pulmonary fibrosis, acute respiratory distress syndrome), intrathoracic pressure decreases below atmospheric pressure, causing the large veins’ pressure to also become sub-atmospheric and collapse as they enter the thorax. The gene discussed is S100A6; the disease is asthma.