Charcoal as an airway isoflurane reflection filter

Abstract

The isoflurane-saving and CO2-retaining effects of a charcoal filter were compared with a Siemens standard heat and moisture (HME) exchanger and an emptied specimen (dummy). Isoflurane was delivered during the inspiratory phase and consumption investigated at 10, 15 and 25 cycles min-1. The investigation was performed by ventilation with humidified air with a constant end-tidal CO2 and temperature. For a comparison, isoflurane was delivered in a conventional manner via the ventilator. The arrangement with a charcoal filter reduced the isoflurane consumption by a factor of 2.0-2.6, depending on ventilatory rate. Most of the saving was a result of the method of isoflurane delivery (factor 1.4-2.0), while adding the reflector gave a further reduction (factor 1.3-1.5). One circumstance that reduced the net efficiency of the charcoal filter was that it also reflected CO2; consequently, total minute ventilation had to be increased to maintain constant end-tidal CO2.

High volatile anaesthetic conservation with a digital in‐line vaporizer and a reflector

“…The retention of CO 2 by zeolite 8,9 and charcoal 6,11,12 reflectors has been well documented. For the ACD used in the traditional configuration at the patient Y, adding a CO 2 absorber would significantly increase the bulk near the patient's head, interfering with patient care and increasing the risk of accidental extubation and facial injury.…”

“…The data processor and device controller [3] compare the input mass of VA with the target output designated by the dial [8]. It instructs the pump [4] to transfer VA from the anaesthetic reservoir [5] to the vaporization chamber [6] and the vapour pump [7] to top up the inspired gas with the appropriate mass of VA to meet the target as concentration. Sensor [1b] is attached to the endotracheal tube and monitors inspired and end-tidal anaesthetic concentrations.…”

“…5 Reflectors retaiñ 80% of exhaled VA with open circuit ventilators. [6][7][8][9] Reflectors are typically placed between the endotracheal tube and the circuit Y-piece. To minimize the deadspace, the VA must be delivered in liquid form through a small opening directly into the circuit between the endotracheal tube and the reflector.…”

Inhalation sedation with the ‘Anaesthetic Conserving Device’ for patients in intensive care units: A literature review

“…(15) The principle of the charcoal filter was further developed, leading to the creation of a device for inhalation sedation AnaConDa TM (Anaesthetic Conserving Device; Sedana Medical, Uppsala, Sweden), which enables sedation and analgesia of patients in ICU with isoflurane and sevoflurane. (16) The Anaesthetic Conserving Device (ACD, AnaConDa TM ) is a modified heat and moisture exchanger, which is inserted between the Y-piece of the breathing circuit and the endotracheal tube (ET-tube) (figure 1) and can be used with any type of ICU ventilator (17,18) without a heated humidifier.…”

Gas exchange with a reflecting system for inhalational anaesthesia

“…48,49 Instead a carbon filter for reflecting inhalational anaesthetics was evaluated. 50 The principle has been further developed leading to the Anaesthetic Conserving Device (ACD, AnaConDa ® ), shown in Fig. 1.…”