I&M I: Lecture 2 - Breathing Systems Flashcards

Question

What are the components of Mapleson breathing systems?

Answer 1

* Facemask (patient end) * Reservoir bag (user end) * Corrugated tube * FGF inlet * Expiratory valve or APL SV: exhalation creates pressure and valve opens PPV: controlled leak determined by dial position during inspiration Controls airway pressures

Answer 2

Ideal for SV patients APL valve near patient Examples: Lack, Magill

Answer 3

Obsolete (except emergency and transport situations) No corrugated tubing after FGF inlet FGF inlet and APL valve in close proximity Example: AMBU

Answer 4

Most common, efficient for both controlled and spontaneous ventilation Example: Bain Circuit Cons: SV inefficient (high FGF, ~3xMV) O2 disconnect can go unnoticed Inner tube can kink Pros: Maintains heat and humidification (countercurrent exchange) Efficient CV (low FGF needed, ~1xMV) Partial rebreathing Scavenging function APL valve

Answer 5

Tubing is the gas reservoir, no bag Poor scavenging Requires high FGF (~3xMV) Humidity easily lost Example: Ayre’s T-Piece

Answer 6

Example: Jackson-Rees Tubing + bag = reservoir Bag has open tail Bag allows for ventilation monitoring and supportive measures Cons: Poor scavenging Requires high FGF (~3xMV) Humidity loss Pros: Can support respiration with reservoir Easy to build Cheap Low resistance No valves Ideal for pediatrics

Answer 7

1. Fresh gas flow (FGF) inlet near reservoir bag = Mapleson A 2. FGF inlet and APL valve near face mask = Mapleson B 3. APL valve near reservoir bag = Mapleson D 4. No APL valve or reservoir bag = Mapleson E 5. Open ended reservoir bag but no APL valve = Mapleson F 6. Efficiency in Spontaneous ventilation: * A>DFE>CB (Mnemonic: All Dogs Can Bite) 7. Efficiency in Controlled ventilation: * DFE>BC>A (Mnemonic: Dog Bites Can Ache) 8. Mapleson D is effective for both the controlled and spontaneous ventilation. 9. Mapleson C is used for resuscitation with manual ventilation because they are small and light weight (no corrugated tubing). 10. Jackson-Rees (Mapleson F) circuit is used for both the SV and CV in pediatric patients.

Answer 8

Most common we see Can be semi-open, semi-closed, or closed Dependent on FGF Pros Gas concentrations stable Conserves heat and humidity Scavenging system Low flows and closed system possible Low resistance (<3 cmH2O) nonrebreather circuit Cons Valve malfunction Increased dead space Complex

Answer 9

Semi-closed (Most common) Moderate FGF Partial rebreathing of gases Closed Low FGF Complete rebreathing of gases

Answer 10

Most common used for us Has reservoir bag Chemical CO2 absorption Moderate FGF needs Partial rebreathing 3 unidirectional valves APL Inspiratory Expiratory

Answer 11

Has reservoir bag Chemical CO2 absorption Low FGF requirement (<1MV) Total rebreathing 3 unidirectional valves APL Inspiratory Expiratory To create this in our anesthesia machines: ✻ use FGF low (~150ml/min): match pt metabolic requirements ✻ close APL entirely during SV (total rebreathing, so no scavenging necessary)

Answer 12

FGF inlet Between absorber and Insp valve Reduces O2 waste Unidirectional check valves prevent backflow I & E limbs APL valve Upstream from absorber (decreases loss of FG) Reservoir Bag Expiratory limb CO2 Absorber Between I&E limbs Y Piece Patient end

Answer 13

Crucial for efficient Circle System use, reduces FGF needs and allows for rebreathing Soda Lime: sodium hydroxide Amsorb Plus: calcium chloride Baralyme (obsolete due to fire risk): barium hydroxide

Answer 14

Contains strong bases: KOH & NaOH Cheap Low flows Sevo becomes unstable Compound A Lethal in rats Safe at 1L/min flows no longer than 2 MAC-hrs Safe at >2L/min indefinitely

Answer 15

All Volatile Anesthetics produce CO with soda lime Des ≥ Enflurane > Iso >> Halo = Sevo Causes of Increased CO Production Dessicated absorbant increases CO production Increased temp Increased VA concentration Low Flows Carboxyhemoglobinemia risk Need to keep flows up!

Answer 16

Ethyl Violet, changes from white to purple as pH decreases Photo deactivation occurs with exposure to fluorescent lights Can produce CO

Answer 17

Capnography Increased inspired CO2 (FiCO2) Should change if ≥5mmHg Color Change Unreliable (Monday mornings often need a change, even if white) Time Long cases, around 6-8 hours continuous use (manufacturer dependent on actual hours), will need canister exchange Monitor FiCO2

Answer 18

Unused canister, or appearance of the canister after photodeactivation After limited use: absorption of CO2 has occurred primarily at the inlet After extensive use: the canister appears nearly completely purple as granules on the side are exhausted. Exhausted soda lime: few granules still capable of absorbing CO2 Channeling effect: air passes preferentially through a channel & quickly exhausts the absorbent (even though most of the canister remains white)

Answer 19

Canister size Must accommodate full Vt of patient Flow rates Low flows ⇧ rebreathing, ⇧ absorption, ⇩ lifetime of canister Channeling Preferential channels created due to friction differences Channels exhaust quickly, decreasing lifetime of canister Wall effect Loosely packed granules allow exhaled gases to bypass granules ⇩ CO2 absorption ⇧ lifetime of canister Granule size and shape Irregular, rough, surface maximizes surface:volume Optimal size ~ 2.5mm

Answer 20

CaOH2 + CaCl2 More expensive than Soda Lime Low flows can offset this cost by using less VA No harmful byproducts No strong bases No risk of Compound A or CO Can use low flows Does not experience photodeactivation after long periods of dessication < absorption than Soda Lime ½ Soda Lime absorption ability

Answer 21

Collect and eliminate exhaled gases NIOSH recommendations Volatile agents: 8 hr time-weighted average of <2ppm (0.5ppm if also using nitrous) Nitrous: if sole agent, must be <25ppm

Answer 22

Interface Protects circuit from excess pressures (positive or negative) Positive-pressure relief valve Mandatory Vents excess gas when occlusions occur distal to the closed interface Negative-pressure relief valve Suction set to high

Answer 23

Passive Disposal System No vacuum, so no negative pressure valves necessary One pressure relief valve necessary to prevent positive pressure buildup

Answer 24

Active Disposal System Vacuum Must contain negative pressure relief valve Faulty valves can transfer pressure changes to patient Vacuum too low creates back pressure Positive pressure valve releases Vacuum too high creates negative pressure Neg pressure valve pops up Must contain reservoir Breaths are periodic, suction is constant. Bag allows time for extraction of gases

Answer 25

* Passive: No vacuum, requires one pressure relief valve * Active: Uses vacuum, must contain negative pressure relief valve

Answer 26

Flat bag/excess negative pressure Remove gas collection tubing from APL valve or turn off scavenger interface Distended bag Valve is incompetent Increase vacuum rate or switch to Ambu if pressures too great FGF in and out of circuit must be equal Barotrauma possible Adjust vacuum rate of bag flat or distended

Answer 27

Reservoir bag in breathing system is replaced by bellows or piston APL valve must be “deactivated” during mechanical ventilation Bag/Vent Switch functionally removes APL valve during mechanical ventilation

Answer 28

Pops up when negative pressure is present ## Footnote Indicates that the system is under negative pressure, which is necessary for proper ventilation.

Answer 29

Single Circuit System Piston Mechanical compression of respiratory gases generates pressure Double Circuit System Bellows Drive gas generates pressure, compressing respiratory gases

Answer 30

Ascending Bellows Standing bellows Collapses with disconnect Adds 3 cmH2O PEEP Descending Bellows Hanging bellows Functions even with disconnect Fills by gravity Can be weighted Requires an additional disconnect alarm Capnography

Answer 31

Driving gas enters space between bellows and housing Pressure on bellows causes compression Compression of the bellows pushes breathing gas into the breathing system

Answer 32

Bellows expands when breathing system gases flow into it Driving gas vents through the exhaust valve to atmosphere Excess gases escape to scavenging system through the spill valve when the bellows is fully expanded

Answer 33

Flat bag or excess negative pressure ## Footnote This can indicate problems with gas collection tubing or the scavenger interface.

Answer 34

Increase vacuum rate or switch to Ambu if pressures too great ## Footnote This indicates that the valve may be incompetent.

Answer 35

Bellows or piston ## Footnote This change is crucial for the mechanical ventilation process.

Answer 36

Must be deactivated ## Footnote This allows for proper ventilation without interference.

Answer 37

* Alarms * Bellows * Controls * Driving Gas Supply * Exhaust Valve * Injector * Safety-relief Valve * Spill Valve * Ventilator Hose Connection ## Footnote Each component plays a vital role in the functioning of the ventilator.

Answer 38

* Single Circuit System * Double Circuit System ## Footnote Different systems affect how pressure is generated and how gases are delivered.

Answer 39

Collapses with disconnect and adds 3 cmH2O PEEP ## Footnote This design is important for maintaining pressure even with disconnections.

Answer 40

Functions even with disconnect and fills by gravity ## Footnote This allows for continuous operation even if disconnected.

Answer 41

Driving gas enters space between bellows and housing, compressing the bellows ## Footnote This action pushes breathing gas into the breathing system.

Answer 42

Bellows expands and excess gases escape to scavenging system ## Footnote This process is essential for clearing gases from the system.

Answer 43

45-50 psi ## Footnote This pressure is necessary for effective gas delivery.

Answer 44

Bellows housed in clear, rigid container Delivers Vt Powered by O2 or air 45-50psi Leaks lead to barotrauma Driving gas can be delivered directly to pt (through hole in bellows) Leaks detected by FiO2 change Gas consumption equals MV/Ve If pt creates negative pressure with inspiration, air enters via the free breathing valve (outside air enters)

Answer 45

Inspiration Spill valve pneumatically closes PPV Expiration Bellows re-expands Full expansion leads to spill valve opens leads to pressurized gas vents to scavenger ## Footnote This prevents excess pressure buildup in the system.

Answer 46

* Single Circuit: Mechanical compression generates pressure * Double Circuit: Drive gas compresses respiratory gases ## Footnote Each type has its own advantages and applications.

Answer 47

Mechanical compression of respiratory gases generates pressure Pros Vt delivery more precise Beneficial for small pts or those with poor lung compliance Conserves medical O2 consumption Wall O2 only for pt consumption, not used to compress equipment (bellows) No intrinsic PEEP Cons Leak in piston diaphragm hypoventilation Room air can entrain as piston returns to filled position

Answer 48

Inspiratory Trigger Transition from expiration to inspiration Set time limit, set pressure, or predetermined Vt (depends on vent mode) Inspiratory Plateau Phase Cycling Phase Transition from inspiration to expiration Expiratory Phase Set time limit, set pressure, or predetermined Vt ## Footnote Understanding these phases is crucial for effective ventilation management.

Answer 49

Peak Inspiratory Pressure (PIP) Highest circuit pressure generated An indication of dynamic compliance Includes airway resistance Plateau Pressure Pressure measured during inspiratory pause (no flow) An indication of static compliance The elastic recoil of respiratory system

Answer 50

Highest circuit pressure generated, indicating dynamic compliance ## Footnote PIP includes factors like airway resistance.

Answer 51

Pressure measured during inspiratory pause, indicating static compliance ## Footnote Reflects the elastic recoil of the respiratory system.

Answer 52

PIP ≥ Pplat ⇧ in PIP and Pplat ➔ ⇧ in Vt or ⇩ pulm compliance Stiff respiratory system Pulm edema, insufficient NMB ⇧ PIP without ∆Pplat ➔ ⇧ airway resistance Increased resistance Bronchospasm, ETT kink ## Footnote Understanding this relationship helps identify respiratory system conditions.

Answer 53

Tidal Volume (Vt) Respiratory Rate (RR) = ventilation rate = breaths/minute Minute Ventilation (VE or MV) VE = Vt ⦁ RR I:E ratio Ratio of inspiration time to expiration time Inspiratory flow rate Rate at which gas flows to the patient expressed as volume per unit time Positive End-Expiratory Pressure (PEEP) Airway pressure above ambient at the end of exhalation

Answer 54

Volume of gas delivered to the patient with each breath ## Footnote Critical for assessing ventilation adequacy.

Answer 55

Ratio of inspiration time to expiration time Inspiration : Expiration Inspiration time vs. expiration time 1:2 default on most machines Problem: Rate is set to 12 breaths/min and I:E ratio of 1:2. What is the inspiratory time? What is the expiratory time? Answer: 60/12 = 5 seconds for one breath, 5/3 = 1.66 = I, 1.66*2 = 3.32 ## Footnote Default is typically set to 1:2 on most machines.

Answer 56

Increases FRC by alveolar recruitment and prevents/reduces atelectasis PEEP valve Integrated into ventilator Add-on device ## Footnote Essential for maintaining lung function.

Answer 57

Calculate the FiO2 delivered if running case at 1 L/min Air and 1 L/min O2? FiO2 = (Oxygen flow rate x 1.00) + (Air flow rate x 0.21) / Total flow rate FiO2 = (1 x 1) +(1 x .21)/2 FiO2 = 1 x .21/2 = 0.605 = 60.5% IF JUST HAVE O2 FLOW RATE... FiO2 = 20% + (4 x O2 Liter Flow)

Answer 58

Pressure Control Ventilation Modes Continuous Mandatory Ventilation (PCV, PC-CMV) Synchronized Intermittent Mandatory Ventilation (PC-SIMV, SIMV-PC) Pressure Control, Volume Guarantee (PC-VG, SIMV-PC-VG) Pressure Support Ventilation (PSVPro, CPAP/PSV, PC-PSV) Biphasic positive airway pressure (PC-BIPAP, PSVPro with PEEP) Airway Pressure Release Ventilation (PC-APRV) Volume Control Ventilation Modes Volume Control Ventilation (VCV, VC-CMV) Synchronized Intermittent Mandatory Ventilation (SIMV)

Answer 59

A pressure control ventilation mode that provides mandatory breaths ## Footnote Useful in maintaining adequate ventilation in patients.

Answer 60

Time cycled, volume controlled with constant volume regardless of compliance ## Footnote Helps in providing consistent tidal volumes.

Answer 61

Time cycled, volume controlled Constant volume regardless of compliance, resistance Pressure varies Preset pressure limit can affect volume Operator sets parameters TV, RR, I:E, PEEP Delivered tidal volumes Set Vt differs from delivered Vt at times Loss to circuit compliance Gain from fresh gas coupling

Answer 62

Flow is constant Vt is controlled Independent of ∆ lung mechanics Set RR Time cycled, machine triggered PIP varies Aim for lowest value possible, ≤ 35 cmH2O PEEP available

Answer 63

Vt 5-7 ml/kg IBW RR 6-12 Titrate to EtCO2 PEEP 4-6 cmH2O Increase if difficulty oxygenating or using small Vt ## Footnote These settings may need to be adjusted based on patient condition.

Answer 64

Spontaneous breaths can be pressure-supported using PEEP and pressure support ventilation ## Footnote Allows patient to have control over their breathing efforts.

Answer 65

Volume-controlled breaths are synchronized to patient’s SV effort to maintain minimum VE and RR If pt apneic for set time or falls below minimum RR/VE, machine triggers a breath of a set Vt

Answer 66

Time cycled, pressure controlled Pressure is constant Vt varies with compliance/resistance Controls PIP, PEEP, RR In case of leaks, pressures are maintained Vt (and VE) vary with changes in pt airway resistance and compliance Flow generated varies Flow is high early in inspiration Flow is lower after initial Pinsp to maintain the set pressure throughout the inspiratory time (Ti)

Answer 67

PCV Vt and Ti are determined by rise time and the set pressure User sets pressure above measured PEEP and inspiratory rise time Vt varies VCV Ventilator is time cycled User sets Vt, RR, I:E, PEEP, Inspiratory pause Pressure varies

Answer 68

PCV, but if patient is making breathing efforts, machine delivers breaths in sync with patient attempts

Answer 69

Volume guarantee mode can be combined with pressure-controlled modes VG confirms that every breath reaches set tidal volume using the minimum necessary pressure If resistance or compliance changes, pressure adapts gradually to restore set Vt (takes several breaths)

Answer 70

Notify user of events and must meet preset thresholds to trigger Retrospective ## Footnote Ensures the safety and effectiveness of ventilation.

Answer 71

Machine supports every detected inspiratory effort (based on set PIP) Patient effort determines the number and duration of supported breaths Vt determined by PIP-PEEP, lung mechanics, pt efforts If resistance or compliance change, Vt and VE will change If apnea detected (set apnea period), vent switches to backup mode Mandatory breaths controlled by set RR and PIP

Answer 72

Vt: 6-8 ml/Kg of IBW PEEP to minimize atelectasis Increase inspiratory time (I:E) to decrease inspiratory pressures Increase expiratory time (I:E) for obstructive lung disease Aim for lowest FiO2 with adequate oxygenation (SpO2 > 97%) Aim for lowest PIP with adequate ventilation Low PIP decreases risk of barotrauma Maintain normal PaCO2 (35-45) GA: aim for ETCO2 30-35

Answer 73

Low PIP, High PIP High PEEP Sustained high airway pressure Negative pressure

Answer 74

Low Vt, High Vt Low VE, High VE “Cannot drive bellows” “Possible disconnect”

Answer 75

Chemical monitoring ETCO2 changes Mechanical monitoring Failure to reach normal inspiratory peak pressure Failure to sense return of Vt on spirometer Visual monitoring Failure of bellows to fill during expiration Failure of manual bag filling during mechanical ventilation (fresh gas decoupling machines only) Fabius GS, Apollo Auditory Absent breath sounds, ventilator cycle sounds absent, etc.

Answer 76

In addition to relying on alarms, continuously monitor parameters Airway pressures, Etgases May notice trends before alarms are triggered Prospective

Answer 77

Ventilator-FGF coupling Do not use O2 flush during spontaneous inspiration Old machines: Vt affected by FGF New machines decouple FGF and ventilator (divert, store, and compensate for FGF) Rapid changes can still have an effect on Vt Excessive positive pressure Pulmonary barotrauma Hemodynamic changes/compromise Vt discrepencies Causes: lung compliance, circuit resistance, gas compression, ventilator-FGF coupling, leaks Piston vs Bellows

Answer 78

Alarm Failure Disabled Settings altered Barotrauma/Volutrauma Excessive airway pressure Settings altered, FGF coupling, Bellows leak Fire/Explosion Hypoventilation Altered settings Vent off Obstruction PEEP Vent dysfunction Hyperventilation Hyperoxia Hypoxia Incorrect gas mix or hypoventilation Hypercapnia Hypocapnia Hyperventilation Inhalation of foreign substances absorbent Inadvertent exposure to VA MH Negative pressure ## Footnote Awareness of these hazards is crucial for patient safety.