Spontaneous Ventilation With the Bain Anaesthetic System

Conway, C.M.; Seeley, H. F.; Barnes, P.K.

doi:10.1097/00132586-197812000-00024

Cited by 11 publications

(15 citation statements)

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“…The predicted fresh gas flow required to abolish completely rebreathing in the Mapleson D system when there is no expiratory pause and exponentially decreasing flow waveforms is very high. This agrees with some experimental evidence in awake volunteers [7]. Any spontaneously breathing patient may of course develop respiratory depression.…”

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confidence: 92%

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Rebreathing in the Mapleson A, C and D breathing systems with sinusoidal and exponential flow waveforms

Cook

1997

Anaesthesia

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SummaryThe degree of rebreathing in Mapleson A, C and D breathing systems for sinusoidal and exponential flow waveforms is analysed mathematically. The effects of altering the I:E ratio and of introducing an expiratory pause are investigated. The results for sinusoidal waveforms closely resemble those for a square wave. Exponential flow waveforms produce results similar to triangular flow waveforms. The Mapleson A system is always the most efficient. The Mapleson C system is efficient when the I:E ratio is 1:1, becoming less efficient with longer expiration and very inefficient with an expiratory pause. The Mapleson D system becomes efficient when the expiratory pause is long. A previous paper presented a mathematical analysis of rebreathing in the Mapleson A, C and D breathing systems [1]. Only linear flow waveforms were analysed, but the method was shown to predict correctly the behaviour of the breathing systems for a range of respiratory patterns [2]. In this paper, the equations developed earlier are solved for spontaneous ventilation with sinusoidal and exponential flow waveforms. Examples of such waveforms are shown in Fig. 1. For the purposes of this analysis, perfect plug flow (i.e. no longitudinal mixing) is assumed. Describing rebreathingThe efficiency of a breathing system depends on the volume of alveolar gas that is voided. The degree of rebreathing in such systems is conveniently quantified as the ratio of total deadspace to tidal volume (V Dtot /V T ), as described by Jaeger & Schultetus [3]. It varies among breathing systems because gas supplied during part of the respiratory cycle is wasted [1]. This may be analysed by dividing the respiratory cycle into phases, summarised here and defined in the glossary. The respiratory cycle is the inspiratory time (T I ) plus the expiratory time (T E ). Inspiration can be subdivided into the time for which gas flows (T If ) and any inspiratory pause (T Ip ) so T I ¼T If þ T Ip . Similarly, expiration comprises the time for which gas flows (T Ef ) plus the expiratory pause (T Ep ) soThe first part (V y ) of the inspired tidal volume is destined to enter the alveoli and the following part (V z ) will come to lie in the deadspace. T If is thus further divided into T Iy , the time to inspire the alveolar portion and T Iz , the time taken to inspire the deadspace portion of the tidal volume.The terminal part of expiratory flow is of key importance. In the Mapleson C system, it is denoted V nC and represents alveolar gas voided from the system. In the Mapleson D system it is called V nD and represents alveolar gas that will be re-inspired. The time required to expire V nC or V nD is T nC or T nD , respectively.If the inspiratory flow is initially low there is a period at the beginning of inspiration when the expiratory valve remains open and gas is being voided from the system. The volume of fresh gas voided in this way in the Mapleson A system is termed V Iw and in the Mapleson C system is

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confidence: 92%

“…They are also characteristic of lung models based on a rotating shaft linked to a piston [6]. Waveforms approximating to the exponentially declining waveform are also seen both in awake volunteers [7] and in anaesthetised patients [5,8]. This paper extends the previous work to these waveforms.…”

Section: Discussionmentioning

confidence: 55%

Rebreathing in the Mapleson A, C and D breathing systems with sinusoidal and exponential flow waveforms

Cook

1997

Anaesthesia

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“…Opinions are particularly divergent regarding anaesthesia with spontaneous breathing. Although Mapleson's original theoretical considerations ( 1) have been largely confirmed by others (2)(3)(4)(5), both experimental and clinical investigations often give conflicting results. I n a previous study we analysed the respiratory flow pattern during halothane anaesthesia with spontaneous breathing (6) and found that it was quite different from that normally produced by a n awake, relaxed volunteer (7).…”

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confidence: 99%

Influence of the respiratory flow pattern on rebreathing in Mapleson A and D circuits

Jönsson

Zetterström

1987

Acta Anaesthesiol Scand

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In a lung model the rebreathing effects of different respiratory flow patterns (RFP) were studied in the coaxial Mapleson A (Lack) and D (Bain, Coax-II) systems during spontaneous breathing. In the Mapleson A system RFP was not found to have any impact. In the D systems FACO2 was higher with an RFP typical of halothane-anaesthetized patients than with an RFP with an exponentially decreasing expiratory flow and an end-expiratory flow pause (FTEP). The difference in FACO2 was 26% with a VF corresponding to 100 ml X min-1 X kg-1 body weight. The RFP in a non-anaesthetized volunteer was intermediate between these two patterns. Rebreathing decreased in the D systems with prolongation of FTEP and when a decelerating expiratory flow was used.

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“…However, recent evidence by Conway suggests that the high fresh gas flow requirements necessary to prevent rebreathing are greater for the Bain circuit (3 • ~E) than for the T-piece. 5 The Magill circuit (FGF = VE) and T-piece with a high fresh gas flow (2.5 • VE) function essentially as non-rebreathing circuits. Normocarbia is achieved at normal levels of minute ventilation.…”

Section: Comparison To Reference Circuitsmentioning

confidence: 99%

Carbon dioxide elimination during spontaneous ventilation with a modified mapleson D system: Studies in a lung model

Rose

Byrick

Froese

1978

Canad. Anaesth. Soc. J.

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Spontaneous Ventilation With the Bain Anaesthetic System

Cited by 11 publications

References 0 publications

Rebreathing in the Mapleson A, C and D breathing systems with sinusoidal and exponential flow waveforms

Rebreathing in the Mapleson A, C and D breathing systems with sinusoidal and exponential flow waveforms

Influence of the respiratory flow pattern on rebreathing in Mapleson A and D circuits

Carbon dioxide elimination during spontaneous ventilation with a modified mapleson D system: Studies in a lung model

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