Week 5- Delivery Systems

Question 1

What are complications of rebreathing CO2?

Answer 1

• Respiratory Acidosis
• Hypoxia
• Dysrhythmias
• Decreased myocardial contractility
• Decreased BP
• Decreased SVR
• HTN & Pulmonary HTN

Question 2

What are some considerations for achieving low resistance on the breathing machine?

Answer 2

Short tubing, large diameter tubing, avoid sharp bends, caution w/ valves, minimize connections

Question 3

What is laminar flow?

Answer 3

Smooth and orderly flow which allows particles to move parallel to the walls of the tubing

Question 4

How is apparatus dead space minimized?

Answer 4

minimized by separating the inspiratory and expiratory streams as close to the patient as possible

Question 5

What are the 4 classifications of delivery systems?

Answer 5

• Open
• Semi-Open
• Semi-Closed
• Closed

Question 6

What are the 2 types of Open Systems?

Answer 6

1. Insufflation/Blow by

2. Open drop

Question 7

Name the different types of Insufflation of Oxygen

Answer 7

“Blow-by,” Tent, Bronchoscopy port, Nasal Cannula, “steal” induction

Question 8

What are some advantages of insufflation of Oxygen?

Answer 8

Advantages: Simplicity
Avoids direct patient contact
No rebreathing of CO2
No reservoir bag or valves

Question 9

What are some disadvantages of insufflation of Oxygen?

Answer 9

Disadvantages:
No ability to assist or control ventilation
May have CO2/ O2 accumulation under drapes
No control of anesthetic depth /FiO2
Environmental pollution

Question 10

How does the historical open drop method work?

Answer 10

True “open circuit” consisted of a bit of cloth saturated with either ether or chloroform or halothane and held over the patient’s face; which was placed in a metal cage device

Question 11

Why isn’t the open drop method common in practice today?

Answer 11

Disadvantages:
Poor control of inspired concentration of anesthetics
Accumulation of CO2 under mask
Predisposes to hypoxia risk
Spontaneous ventilation only/ cannot control ventilation
OR Pollution/ Health care provider risk

Question 12

What are the 5 components of the Semi-Open system?

Answer 12

• Facemask or ETT
• Pop-off valve/APL valve (a spring loaded valve to expel excess gas)
• Reservoir tubing
• Fresh gas inlet
• Reservoir bag (Adult bag holds 3L, Peds 2L, Neonates 1L)

Question 13

What are 3 types of Semi-Open Systems?

Answer 13

• Mapleson (A-F)
• Bain
• Circle

Question 14

Where is the pop-off valve/APL valve located in the Group 1 and 2 (Mapleson A,B,C) systems?
Is the valve open or closed?

Answer 14

• POP-OFF is located near the facemask or ETT

- Valve is OPEN and this system is more efficient for spontaneous ventilation

Question 15

Where is the pop-off valve/APL valve located in the Group 3 (Mapleson D,E,F) systems?
Is the valve open or closed?

Answer 15

• FRESH GAS FLOW(FGF) is located near the facemask or ETT

- Valve is CLOSED and this system is more efficient for controlled ventilation

Question 16

Is there a clear separation of inspired and expired gases in the Mapleson system?

Answer 16

No, both inspiration and expiration take place through the same tube which can lead to deadspace and rebreathing (i.e. inspired flow exceeds FGF)

Question 17

CO2 Rebreathing will depend on:

Answer 17

Fresh gas inflow rate
Minute ventilation (tidal volume & RR) of patient
Type of ventilation (spontaneous or controlled)

Question 18

What is the goal of the Mapleson system as it pertains to end expiration?

Answer 18

During exhalation, FGF will push expired alveolar gas toward the APL valve so the next inspiration will contain primarily FGF

Question 19

What is the most efficient Mapleson during controlled ventilation?

Answer 19

Mapleson D

Can also be used for spont. ventilation but a higher FGF rate is required

Question 20

Describe Mapleson E (T-Piece)

Answer 20

No reservoir bag
No pop-off bag
Requires high rates of FGF

Question 21

Describe Mapleson F

Answer 21

• Adjustable pop-off at the end of reservoir bag
• Used during transport of ventilated patients (commonly in Peds)
• Not much deadspace or resistance

Question 22

Describe the Bain Circuit tubing

Answer 22

-FGF tubing within the large bore corrugated tubing
allows exhaled gas to warm the inspired gas

• preserves heat and humidity
• for controlled OR spontaneous ventilation

Question 23

What is the primary disadvantage of Bain Circuit tubing and what test do you use to assess for this problem?

Answer 23

Potential for inner tube leaks, kinking or disconnection

-Pethick Test assesses the integrity of the inner tubing

Question 24

What are the characteristics of an Open System?

Answer 24

NO gas reservoir bag
NO valves
NO rebreathing of exhaled gas