Seakins, "Relationship between the humidity and temperature of inspired gas
and the function of the airway mucosa," Critical Care Medicine, vol.
First, inspired gas
is delivered to the patient through a face mask.
The fraction of minute production of carbon dioxide excreted via the leak correlated with the fraction of inspired gas
excreted via the leak.
In addition, normal mucociliary function may be impaired by inadequately humidified inspired gas
. The ETT itself may cause irritation of the airways and increased secretion production, and in the presence of respiratory infection the increased amount and viscosity of pulmonary secretions further impede clearance.
Anaesthetic circuits are designed to give greater control over inspired gas
concentrations using larger reservoir volumes consisting of both large and low compliance reservoir bags and large volume inflow tubing combined with masks or mouthpieces designed to reduce leakage and entrainment.
This inflation hold allows inspired gas
to equilibrate in regions of the lung with incongruous time constants.
The Rossignol inspired gas
tube has no moving parts and doesn't interfere with barrel harmonics like a piston system can.
Bake B, Wood L, Murphy B, Macklem PT, Milic-Emili J (1974) Effect of inspiratory flow rate on regional distribution of inspired gas
. Journal of Applied Physiology 37: 8-17.
When airway leak pressures were higher than 12 cm [H.sub.2]O, the inspired gas
concentrations were essentially the same as that of room air (nitrous oxide: 0%; oxygen: 21%).
To prevent these pathologic changes, the American Association for Respiratory Care Clinical Practice Guidelines suggests that inspired gas
contain a minimum of 30 mg of [H.sub.2]O per liter at 30 C (Branson, Campbell, Chatburn, & Covington, 1992).