If I were to ventilate a 7 kg baby, who has a 50 ml tidal volume, with a 50 ml breath using this circuit, no fresh gas containing oxygen will reach the baby’s lungs.
The smaller the tidal volume, the larger the impact of equipment dead space. The colored external portion of the LMA, the elbow connector, filter and the end of the breathing circuit are all equipment dead space. A poor mask seal, failure to squeeze the bag effectively, or allowing the patient to breath shallowly could all lead to hypoventilation in this scenario.Įxample of equipment dead space. This particular combination, including the LMA outside the mouth, the end of the breathing circuit, the bacterial/humidification filter, and the elbow adapter added an additional 50 ml of dead space. The colored portion shows equipment dead space. The photo shows the end of an anesthesia breathing circuit I recently used. Usually equipment dead space is small compared to the total tidal volume, but not always. Your manually administered breath must include enough volume to cover this equipment dead space to avoid hypoventilation. for more on physiologic dead space see:Įquipment dead space includes the mask, the part of the endotracheal tube or laryngeal mask airway (LMA) outside the patient’s mouth, even the elbow on the endotracheal tube connecting it to the ventilation bag. Decreased cardiac output or decreased lung perfusion increases pulmonary dead space by diminishing pulmonary capillary blood flow. Physiologic dead space changes from minute to minute. In Physiologic dead space, lack of capillary flow at the time of measurement prevents gas exchange.
A third of the normal tidal volume is anatomic dead space, with a volume of about 2ml/kg in an adult and up to 3ml/kg in a baby. The lungs cannot absorb oxygen or eliminate carbon dioxide in anatomic dead space. These fixed parts of the respiratory tract are ventilated but not perfused. Anatomic Dead SpaceĪnatomic dead space does not have alveoli, such as the trachea, bronchi, and bronchioles. The 3 different types of dead space consist of anatomic, physiologic, and last, but not least, equipment. Ignoring equipment dead space can lead to significant hypoventilation. We often forget equipment dead space, the dead space belongs to any airway equipment used to assist ventilation.
We often worry about anatomic and physiologic dead space. Dead space is the portion of the respiratory system where tidal volume doesn’t participate in gas exchange.
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