Administering ambient pressure oxygenation to the non‐ventilated lung during thoracoscopic surgery

The Theoretical Basis for Using Apnoeic Oxygenation via the Non-ventilated Lung during One-lung Ventilation to Delay the Onset of Arterial Hypoxaemia

“…Such recordings show not only end-tidal PCO 2 (P ET CO 2 ) from the ventilated lung, but also an indication of the P v -CO 2 in the equilibrated non-ventilated lung. These add visual support to the theory of an increased arterial to endtidal PCO 2 difference (P a CO 2 -P ET CO 2 ) during 'onelung apnoeic oxygenation' 55 , above the higher than normal level that is seen in some patients during onelung ventilation 57 .…”

“…Further insight into relevant physiology can be gained by recording PO 2 and PCO 2 , not only in the ventilating inspiratory and expiratory gas fl ow, but also in the tidal gas movement 56 that occurs between the non-ventilated lung and the oxygen reservoir bag with each cycle of ventilation to the ventilated lung 55 . This tidal gas movement results in the gas in the reservoir bag progressively equilibrating with the gas in the non-ventilated lung, with the CO 2 concentration in the reservoir eventually equilibrating with the mixed venous PCO 2 (P v -CO 2 ) 55 . Such recordings show not only end-tidal PCO 2 (P ET CO 2 ) from the ventilated lung, but also an indication of the P v -CO 2 in the equilibrated non-ventilated lung.…”

Speed of collapse of the non‐ventilated lung during one‐lung anaesthesia: the effects of the use of nitrous oxide in sheep

“…This could be achieved by connecting to the non‐ventilated lung a reservoir bag that contains a mixture of 50% nitrous oxide in oxygen or, alternatively, a reservoir bag containing oxygen alone. With a reservoir bag containing 100% oxygen, the tidal movement of gas out of and back into the non‐ventilated lung that occurs before the thoracic cavity is opened [13] will result in a progressive increase in the partial pressure of nitrous oxide in the reservoir [14]. Thus, at the time the thoracic cavity is opened and the lung collapses away from the chest wall, the partial pressure of nitrous oxide in the non‐ventilated lung will be higher than would otherwise be the case.…”

“…It is therefore suggested that combining positive pressure ventilation with 50% nitrous oxide in oxygen and an oxygen reservoir connected to the non‐ventilated lung [4, 14] is a logical progression in the management of those cases where nitrous oxide is not contraindicated. It is possible that these two management practices may also reduce the likelihood of clinically important arterial desaturation developing in the course of thoracoscopic surgery.…”

A new clinical sign during one‐lung anaesthesia: fact or fiction?

“…Another of the several suggested benefits [1, 4–6], is the ability to identify gas leaking past the endobronchial cuff of the double‐lumen tube. If the leak is large, the reservoir bag will be seen to progressively fill with each inspiratory phase of single‐lung ventilation, but smaller leaks may not be so immediately obvious.…”