Breathing Systems typical circle circuit);CO2 removal by absorber or FGFAlternative Conway Without CO2 absorbers Mapleson type, Resuscitation BagsWIth CO2 absorbers Circles, Waters (to and fro) 3.
MAPLESON CIRCUITS 1. MAPLESON A (Magill) CIRCUIT FGF enters at the end remote from the patient, and there is a Heidbrink one way pop off valve at the mask end. Originally C type systems were common; Magill designed the A circuit to get the bag away from the patient during faciomaxillary surgery. Magill in spont respiration (the diagram is incorrect in two places)The patient inspires whatever is in the tube, using the bag as a volume reservoir. On expiration, the bag refills from a combination of expired gas going back up the corrugated tube and incoming fresh gas. When the bag is full, exhaled alveolar gas is vented from the exhale valve, and then during any expiratory pause, FGF pushes the remaining alveolar gas out. Theoretically FGF = 0.7 x Valv should prevent significant rebreathing because deadspace gas (fresh) is not wasted, but FGF = VA more reliably prevents burberry outlet factory online rebreathing. Tube volume must exceed (Vt Vd) or alveolar gas could contaminate the bag. Inadequate FGF causes rebreathing. Difficult to detect from the CO2 waveform alone all that happens is that the rapid fall on inspiration is delayed. More commonly burberry clearance online the valve is partially closed enough to permit adequate tidal volumes despite parallel loss of gas out the valve. FGF must be increased to compensate for gas lost during inspiration typically 2.5x minute ventilation. c) the Lack system A co axial Magill, with the expiratory valve brought coaxially back to the Fresh Gas outlet. Not popular due to inefficiency during controlled ventilation. 2. MAPLESON B C SYSTEMS Inefficient. burberry design Once the bag is full during expiration, fresh gas is vented. Not suited for spontaneous breathing rebreathing is inevitable (with CO2 entering the tubing or bag) unless FGF exceeds peak inspiratory flow rates (3xMV). The C circuit is compact and was used for short transports before self inflating bags became available. Acceptable CO2 levels could be achieved with a FGF of 2 x MV and mild hyperventilation. If the cylinder became empty ventilation was impossible. 3. MAPLESON D, E and F SYSTEMS FGF enters at patient end. D system has a relief valve proximal to the bag. Bain circuit is a co axial D introduced in 1972 (Bain and Spoerel). E and F are functionally identical. Spontaneous breathing: inefficient. Inspiration is from Fresh Gas Flow and/or tube contents. If FGF > PIFR, all inspired gas will be fresh. If there is an expiratory where to find burberry on sale pause, fresh gas pushes exhaled alveolar gas down the tube during the zero flow period, and FGF requirements are reduced somewhat. If no exp. pause, needs FGF > 2.5xMV. With exp. pause may be OK as low as 100ml/kg. Most patients can readily manage a small inspired CO2 load. CO2 during capnometry inspiration indicates a need for higher flows.
Controlled ventilation: more efficient. Significant mixing occurs and CO2 is 'washed out' by FGF. Provided that VA is adequate or slightly increased, CO2 washout depends on FGF, with normal CO2's at an FGF of 70ml/kg.
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