An Evaluation of Rebreathing With the Bain System During Anaesthesia With Spontaneous Ventilation

Meakin, G.; Coates, Allan L.

doi:10.1093/bja/55.6.487

Cited by 28 publications

(9 citation statements)

References 18 publications

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“…The dill'crence from the low coirccntration of a decelerating flow, as in our VOI, curve, then becomes more pronounced. 'I'his influence of the flow at the end of active expiration was confirmed in experiment C. T h t x results are consistent with the discussion h y Meakin & Coates (18).…”

Section: R : I S C U Ss I O Nsupporting

confidence: 86%

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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Section: R : I S C U Ss I O Nsupporting

confidence: 86%

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

Jönsson

Zetterström

1987

Acta Anaesthesiol Scand

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“…Not surprisingly, such analyses unite in finding the Mapleson D system inefficient and are supported by a wealth of data from physical lung models, also employing respiratory patterns without significant expiratory pauses [12][13][14]. In studies in which there has been a n expiratory pause, its effect is indeed to reduce rebreathing in this system [ 15, 161. The value VnD used in this paper is identical to the 'area c' calculated by Meakin and Coates [7]. Their analysis demonstrated that this would be reduced if the expiratory flow decreased throughout expiration but they did not consider the expiratory pause.…”

Section: Discussionmentioning

confidence: 69%

Respiratory pattern and rebreathing in the Mapleson A, C and D breathing systems with spontaneous ventilation

Cook

1996

Anaesthesia

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“…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%

“…A weakness in this work was that the equations were solved only for linear flow waveforms, whereas the flow waveforms found in real patients (and those produced by many lung models) are nonlinear. Sinusoidal flow waveforms are commonly seen, especially when the respiratory rate is high [4,5]. They are also characteristic of lung models based on a rotating shaft linked to a piston [6].…”

Section: Discussionmentioning

confidence: 99%

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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An Evaluation of Rebreathing With the Bain System During Anaesthesia With Spontaneous Ventilation

Cited by 28 publications

References 18 publications

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

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

Respiratory pattern and rebreathing in the Mapleson A, C and D breathing systems with spontaneous ventilation

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

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