does dead space in lung mean that percentage of lung is not in use

pointed out that increasing positive end-expiratory pressure (PEEP) in ARDS augments blood oxygenation and decreases shunt. However, if data generated breath-by-breath by capnographs are not integrated and analyzed together with data coming from other physiologic monitors and lung image analysis, their clinical meaning could be incomplete and even misleading. Modern volumetric capnographs incorporate this physiologic approach, enabling intensivists to measure VD/VTphys at the bedside. Currently, dead space is measured at the bedside by volumetric capnography, which reports expired CO 2 elimination as a function of expired VT, and VD/VTphys is calculated using the Enghoff’s modification of Bohr’s original equation: VD/VTphys = (PaCO 2 – PECO 2)/PaCO 2, where PaCO 2 is the arterial partial pressure of CO 2 obtained by arterial blood sampling and PECO 2 is an estimate of mixed expired partial pressure of CO 2 obtained from the mid-portion of phase III of the volumetric capnogram. The physiologic ventilatory dead space fraction (VD/VTphys) is usually defined as the fraction of tidal volume (VT) that does not participate in gas exchange. Dead space comprises two separate components: airway dead space (the volume of areas that do not contribute to gas exchange) and alveolar dead space (the volume of well-ventilated alveoli that receive minimal blood flow). Positive pressure ventilation (i.e.Dead space refers to lung areas that are ventilated but not perfused.Neck extension and jaw protrusion (can increase it twofold).General anesthesia – multifactorial, including loss of skeletal muscle tone and bronchoconstrictor tone.The ratio of physiologic dead space to tidal volume is usually about 1/3. Alveolar dead space is the volume of gas within unperfused alveoli (and thus not participating in gas exchange either) it is usually negligible in the healthy, awake patient. Anatomic dead space is the volume of gas within the conducting zone (as opposed to the transitional and respiratory zones) and includes the trachea, bronchus, bronchioles, and terminal bronchioles it is approximately 2 mL/kg in the upright position. Physiologic or total dead space is the sum of anatomic dead space and alveolar dead space. Dead space is the volume of a breath that does not participate in gas exchange.

Does dead space in lung mean that percentage of lung is not in use