The fresh gas flow decoupling valve and the potential for leaks in the anaesthetic circle breathing system

AbstractTo identify the better volatile anaesthetic delivery system in an intensive care setting, we compared the circle breathing system and two models of reflection systems (AnaConDa™ with a dead space of 100 ml (ACD-100) or 50 ml (ACD-50)). These systems were analysed for the parameters like wash-in, consumption, and wash-out of isoflurane and sevoflurane utilising a test lung model. The test lung was connected to a respirator (circle breathing system: Aisys CS™; ACD-100/50: Puriton Bennett 840). Set parameters were volume-controlled mode, tidal volume-500 ml, respiratory rate-10/min, inspiration time-2 sec, PEEP-5 mbar, and oxygen-21%. Wash-in, consumption, and wash-out were investigated at fresh gas flows of 0.5, 1.0, 2.5, and 5.0 l/min. Anaesthetic target concentrations were 0.5, 1.0, 1.5, 2.0, and 2.5%. Wash-in was slower in ACD-100/-50 compared to the circle breathing system, except for fresh gas flows of 0.5 and 1.0 l/min. The consumption of isoflurane and sevoflurane in ACD-100 and ACD-50 corresponded to the fresh gas flow of 0.5-1.0 l/min in the circle breathing system. Consumption with ACD-50 was higher in comparison to ACD-100, especially at gas concentrations > 1.5%. Wash-out was quicker in ACD-100/-50 than in the circle breathing system at a fresh gas flow of 0.5 l/min, however, it was longer at all the other flow rates. Wash-out was comparable in ACD-100 and ACD-50. Wash-in and wash-out were generally quicker with the circle breathing system than in ACD-100/-50. However, consumption at 0.5 minimum alveolar concentration was comparable at flows of 0.5 and 1.0 l/min.

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Comparison in Spontaneous Ventilation of the Maxima with the Humphrey ADE Breathing System and between Four Methods for Detecting Rebreathing

Anaesthesia and Intensive Care ◽

10.1177/0310057x9502300305 ◽

1995 ◽

Vol 23 (3) ◽

pp. 296-301 ◽

Cited By ~ 5

Author(s):

D. M. Miller ◽

A. Palm

Keyword(s):

Carbon Dioxide ◽

Flow Rate ◽

Qualitative Method ◽

Gas Flow ◽

Breathing System ◽

Practical Application ◽

Efferent Limb ◽

Clinical Methods ◽

Significant Difference ◽

Reservoir Systems

An enclosed efferent, afferent reservoir breathing system (Maxima, Life Air Pty Ltd), being valveless, was compared to a simple afferent reservoir system (Humphrey ADE, A mode), having a valve, by assessing fresh gas flow (V̇F) requirements, with respect to ventilation (V̇E), that prevents rebreathing in volunteers, awake and breathing spontaneously. The results are recorded in terms of the quotient V̇F/V̇E associated with the onset of rebreathing. At the same time four clinical methods for assessing rebreathing were evaluated from the perspective of suitability for practical application during anaesthesia. No significant difference was found in the VF requirements between the ADE and Maxima breathing systems with respective values obtained for the quotient VF/VE of 0.80 and 0.77. Our findings showed that the method of sampling carbon dioxide (CO2) at the outflow of the efferent limb of the patient connector (eliminated CO2 method) in both afferent reservoir systems provided the highest flow rate and most reliable indication for detecting potential or actual rebreathing, when attempting to minimize VF. It provides no additional deadspace or resistance to gas flow, and has the advantage of being the only qualitative method that is reliable for the purpose of detecting the onset of rebreathing.

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Carbon dioxide narcosis due to human error in a dog

Veterinary Record Case Reports ◽

10.1136/vetreccr-2019-001053 ◽

2020 ◽

Vol 8 (2) ◽

pp. e001053

Author(s):

Victoria Phillips ◽

Alessandra Mathis

Keyword(s):

Carbon Dioxide ◽

Human Error ◽

Visual Inspection ◽

Carbon Dioxide Tension ◽

Breathing System ◽

Normal Limits ◽

Inhalational Anaesthesia ◽

Prolonged Recovery ◽

End Tidal ◽

Circle Breathing System

Incorrect assembly of a parallel Lack (Mapleson A) breathing system resulted in carbon dioxide narcosis in a dog due to rebreathing of expiratory gases. A seven-year-old, male neutered Rottweiler, weighing 49 kg, failed to recover after discontinuation of inhalational anaesthesia following a forequarter amputation for osteosarcoma. During recovery, the endotracheal tube had been connected to a parallel Lack anaesthetic breathing system delivering 100 per cent oxygen at 5 l/minute. Although a prolonged recovery, 30 minutes, all vital parameters were considered within normal limits until a severe increase in respiratory effort was noted. Capnography revealed rebreathing with an end-tidal carbon dioxide tension of >150 mm Hg (>19.9 kPa). The dog was transferred to a circle breathing system, and with normalisation of the capnogram, recovery proceeded without further complications. Visual inspection of the parallel Lack breathing system revealed misassembly which had resulted in rebreathing of expiratory gases, extreme hypercapnia causing prolonged recovery due to narcosis.

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