something in the ventilator circuit that adds dead space quizlet ch 8

Children are especially vulnerable because small increases in apparatus dead space can significantly increase dead space to tidal volume ratio (Vd/Vt). Apparatus dead space increases dead space volume, causing either increased PaCO2 or the need to increase minute ventilation to maintain normocapnia. Since spontaneous breaths are without positive pressure, there is no need to calculate a corrected tidal volume.Physiologic dead space is defined as the volume of the lung where gas exchange does not occur.

Compressed volume can only be lost on mechanical breaths. Then take set VT - compressed volume = corrected tidal volume. To find the actual amount of volume delivered to the patient in those machines that do not automatically compensate, the formula for corrected tidal volume is: Tubing compliance x PIP - PEEP = compressed volume. Thus the higher the delivery pressure, the more volume is compressed in the circuit. For those ventilators that do not automatically correct for compressible volume, the RCP must keep in mind that the one variable that affects compressible volume the most is the peak inspiratory pressure. The amount of compressible volume lost to the circuit is then added to the delivered tidal volume so that the patient actually receives the volume set on the ventilator. This is known as the compressible volume. Most newer ventilators will measure circuit compliance and calculate the amount of volume lost to the circuit with each breath.

Most circuits have a tubing compliance of about 1.5 to 2.5 ml/cmH20. The amount of volume lost to the tubing is as a result of how much gas is compressed in the circuit during positive pressure ventilation.

Something in the ventilator circuit that adds dead space quizlet ch 8