Delivery Systems Flashcards

Question

Advantages of Mapleson System

Answer 1

* Simple components * Lightweight * Can provide positive pressure ventilation * Low resistance * Portable * If using inhaled anesthetics, more predictable anesthetic concentration and decreased room pollution when compared to open systems

Answer 2

* Requires calculation of FGF which varies with both type of circuit and mode of ventilation (SV or CV). * Control of anesthetic depth is variable- anesthetic gases will be diluted as FGF increases (BUT control is better than with open systems). * If FGF not maintained, possibility of CO2 buildup and rebreathing is present. * Minimal rebreathing of other gases- poor conservation of heat and humidity. * FGF costly * Requires special assembly and function is complex

Answer 3

Available Lengths: 40'', 60'', 72''

Answer 4

* Components are arranged in a circle * Can be used as a semi-open, semi-closed, or closed system * Depends on the adjustment of the APL valve * Depends on Fresh gas flow rate * Prevents re-breathing of CO2 by chemical neutralization * Allows re-breathing of other exhaled gases

Answer 5

1. Fresh gas flow source 2. Inspiratory and expiratory unidirectional valves 3. Inspiratory and expiratory limbs/ corrugated tubing 4. Y-piece connector 5. Adjustable pressure-limiting valve (APL valve, over-flow valve, or Pop-off valve ) 6. Reservoir bag 7. CO2 absorber

Answer 6

1. A unidirectional valve must be located between the patient and the reservoir bag on both the inspiratory and expiratory limbs of the circuit; unidirectional valves should be close to patient to prevent backflow into the inspiratory limb if a circuit leak develops; however, unidirectional valves should not be placed in the breathing Y-piece, since that makes it difficult to confirm proper orientation and intraoperative function. 2. The FGF inflow cannot enter the circuit between the expiratory valve and the patient; should be placed between the absorber and the inspiratory valve; positioning FGF downstream from the inspiratory valve would allow FGF to bypass the patient during exhalation and be wasted; FGF introduced between the expiratory valve and the absorber would be diluted by recirculating gas (furthermore, inhaled anesthetics may be absorbed or released by soda lime granules in CO2 absorber, thus slowing induction and emergence) 3. The over-flow pop-off valve (APL) cannot be located between the patient and the inspiratory valve. It should not be placed immediately before the CO2 absorber to conserve absorption capacity of the granules and to minimize venting of FGF. 4. Resistance to exhalation is decreased by locating the breathing bag in the expiratory limb; bag compression during controlled ventilation will vent alveolar gas through a pressure relief valve (APL), conserving absorbent.

Answer 7

* Gas flowing into the valve raises the disc from its seat, then passes through the valve. * Reversing the gas flow causes the disc to contact its seat, stopping further retrograde flow. * The guide (cage) prevents lateral or vertical displacement of the disc. * The transparent dome allows observation of disc movement.

Answer 8

* AKA: Breathing bag, Respiratory bag * Made of neoprene or rubber * Neck – 22 mm female fitting to male system * Tail – end opposite neck Functions: - accumulation of gas during exhalation - assist/control ventilation - visual/tactile monitor to observe spontaneous respirations - protects against excessive pressure reservoir of gas

Answer 9

* Large bore, non rigid corrugated tubing * Rubber or clear plastic * 22 mm female fitting w/machine * Patient end – T piece 22 mm male, 15 mm female coaxial fitting Functions: - Flexible, low resistance, lightweight connection - Reservoir

Answer 10

* AKA: pressure relief, pop-off, safety-relief valve * Releases gases to scavenge or atmosphere exhaust port * User-adjustable: clockwise – closes valve & increases pressure within system * Provides control of pressure in system – pressure gauge on absorber

Answer 11

* *Spontaneous Respiration:** - valve fully open - close partially only if reservoir bag collapses * *Assisted Ventilation:** - valve partially open - bag squeezed on inspiration - careful & frequent adjustments necessary * *Mechanical Ventilation** – valve closed (if machine not equipped w/switch)

Answer 12

If the unidirectional valves are working properly, the only dead space in the circle system is between the Y piece and the patient.

Answer 13

The pathway of gas flow through the absorber during oxygen flush.

Answer 14

* Not used often- occasionally for sedation (mask placed over face to increase FiO2) * No re-breathing occurs; very high flow of fresh gas flows (10-15L/min) are used and eliminates rebreathing of gases * No conservation of wastes gases and heat * APL valve is open all the way or ventilator in use

Answer 15

* Most commonly used breathing system in U.S. practice * Allows for some re-breathing of agents and exhaled gases (minus CO2 due to CO2 absorption) * Uses low flow rates (1-3L/min) * Conserves some heat and gases * APL valve is partially closed and adjusted as needed; or ventilator is in use

Answer 16

* Used often in long surgical cases and third world countries * Inflow gas exactly matches metabolic needs/ O2 consumption of the patient using very low flows (O2 flow rate = @ 200 mL/min) * Total re-breathing of all exhaled gases after absorption of CO2 * APL valve is CLOSED or ventilator is in use

Answer 17

O2 Consumption (VO2) = 10 x kg^3/4 In a 70kg patient: 10 x 70^3/4 10 x 24.2 = 242 mL O2/min

Answer 18

* Relative stability of concentration of inspired gases * Conservation of moisture and heat * Can be used for closed-system anesthesia * Can be used with fairly low flows with no rebreathing of CO2 * Economy of anesthetics and gases * Can scavenge waste gases * Prevention of OR pollution

Answer 19

* Complex design * Has at least 10 connections * This sets the stage for potential leaks, obstruction, or disconnection * **A third of malpractice claims are related to disconnects or misconnects of the circuit** * Potential of malfunctioning valves * Increased resistance to breathing * Less portable and convenient than the Mapleson systems due to its bulkiness

Answer 20

* Leak Test * Set all gas flows to zero, occlude the Y-piece, close the APL valve, pressurize the circuit to 30 cm of water pressure using the O2 flush valve, ensure pressure holds for 10 seconds, listen for sustained pressure alarm, open APL valve and ensure pressure decreases * *This test does not assess integrity of unidirectional valves* * Flow Test * Attach breathing bag to Y- piece, turn on ventilator, and assess integrity of unidirectional valves

Delivery Systems Flashcards

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