Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location.
anatomical dead space. In pulmonary physiology, the area in the trachea, bronchi, and air passages containing air that does not reach the alveoli during inspiration and is not involved in gas exchange. This is termed dead space because the air does not reach the alveoli and is not involved in gas exchange. Normal anatomical dead space is 2.2 ml/kg or 1 ml/lb.
2 the amount of lung in contact with ventilating gases but not in contact with pulmonary blood flow. Alveolar dead space is characterized by alveoli that are ventilated by the pulmonary circulation but are not perfused. The condition may exist when pulmonary circulation is obstructed, as by a thromboembolus.natomic dead space is an area in the trachea, bronchi, and air passages containing air that does not reach the alveoli during respiration.