Paediatric breathing systems

paed

1. Paediatric breathing systems Paediatric breathing systems
•Dr. S. Parthasarathy
MD., DA., DNB, MD (Acu), Dip.
Diab.DCA, Dip. Software statistics
PhD (physio)
•Mahatma Gandhi medical college and
research institute , puducherry – India
[email protected]

2. •Just after the
tea session ----

3. •We are moving on to the
T
session

4. Dr Philip AyreDr Philip Ayre

5. Lets go back !! Lets go back !!
•It was because Dr. Phillip Ayre lost a child due to
high pressure gas flow, he came out with tubing
for children to breathe safely in 1937 termed
Ayre’s T piece.
• anaesthetic breathing systems for paediatric use
have undergone innumerable modifications to
suit different patients and situations.

6. Circuit or system !! Circuit or system !!
•Such systems were also called circuits,
but as the gas flow is not circuitous in
many of them, the word breathing system
is preferred. Most of the systems can also
be used with ventilators.
•What is a breathing system?

7. Definition Definition
•A breathing system is defined as an
assembly of components which connects
the patient’s airway to the anaesthetic
machine creating an artificial atmosphere,
from and into which the patient breathes.

8. ComponentsComponents
•A fresh gas entry port /
delivery tube
•A reservoir for gas, in the
form of a bag
•A port to connect it to the
patient's airway;
•An expiratory port / valve
•Corrugated tubes for
connecting these
components.

9. ComponentsComponents
•A carbon dioxide
absorber if total
rebreathing is to be
allowed
•Flow directing valves
may or may not be
used

10. SOME DEFINITIONSSOME DEFINITIONS..
•Breathing tubing made of either rubber or
plastic are usually corrugated to enable
bending without kinking
•corrugation may increase compliance -
important in ventilating noncompliant
lungs.
•more gas rests in the tubing -- excess
dead space * IMPORTANT IN PAEDIATRICS.
•tubing with smooth inner are also in the
offing

11. •Reservoir bags (RB
- either a tube or a bag.
•monitoring respiration
•ventilating the patient
•reservoir of gas to meet patient’s inspiratory flow
requirements.
•Otherwise HIGH fresh gas flows (FGF) needed.
•We should keep in mind that anaesthesia machines
give continuous supply of gas and all our patients
are intermittent inhalers.

12. •Expiratory port valve (APL valve)
•--user adjustable valve that releases
gases to atmosphere or the scavenging
system. It is usually made of metal with a
seat and disc against a spring.
•paediatric APL valve: less resistance,
•safer and effective scavenging-possible.

14. DEFINITIONSDEFINITIONS
•The afferent limb is that part of the
breathing system which delivers the fresh
gas from the machine to the patient.
•reservoir is placed in this limb as in
Mapleson A, B, C and Lack’s systems,
afferent reservoir systems (ARS).

15. Definitions Definitions
•The efferent limb -part of the breathing
system which carries expired gas from the
patient and vents it to the atmosphere
through the expiratory valve/port.
•reservoir placed in this limb as in
Mapleson D, E, F and Bain systems,
efferent reservoir systems (ERS).

16. Apparatus dead spaceApparatus dead space
•It is the volume of the breathing system from the patient-
end to the point up to which, to and fro movement of
expired gas takes place.
•A. afferent reservoir system, the apparatus dead space
extends up to the expiratory valve positioned near the
patient.
•B. efferent reservoir system, the dead space extends up
to the point of FG entry
•C. In systems where inspiratory and expiratory limbs are
separate, it extends up to the point of bifurcation

18. SHORT BREAK.SHORT BREAK.
•AS A GUEST SPEAKER IN GANDHI
JAYANTHI CELEBRATION IN
SCHOOL.
•I WAS ELABORATING ABOUT THE
PRINCIPLES OF NONVIOLENCE,
DANDI MARCH,QUIT INDIA
MOVEMENT KHADI DRESS ETC….

20. AFTER I FINISHEDAFTER I FINISHED
•ONE FELLOW STOOD UP TO ASK
A DOUBT.
•‘ SIR, YOU HAVE SPOKEN NICELY
ON GANDHI IN THIS GANDHI
JAYANTHI FUNCTION ---- WHO IS
JAYANTHI ? PLEASE TELL US
SOMETHING SIR’

21. Certain characteristics which Certain characteristics which
differ in paediatric patientsdiffer in paediatric patients
•Minimal resistance : resistance is
increased according to the fourth power
of radius and hence a wide bore tube
with diameter of not less than 1 cm is
ideal.
•less dead space
Eg.- 3 kg infant –
Tidal volume : 21 ml (7ml/kg)

22. Concerns in paediatricsConcerns in paediatrics
•Lightness and ease of use.
•Ribs are horizontal and breathing is
diaphragmatic. The infant diaphragm has
mainly type 1 fibres and easily fatigued.
•Increased CO
2
production (8ml/kg in
infants Vs 4 ml/kg in adults.)
•Any increase in minute ventilation is due
to increase in rate than tidal volume.

23. T piece T piece

24. •The T piece system -- light metal tube, 1 cm in
diameter, and 5 cm in length with a side arm.
FGF enters the system through the side
•expired gas goes to the atmosphere.
•system is short
•diameter is more than trachea with no valves
the resistance is minimal.
•The dead space is very less as it is only up to
the point of entry of FGF.
•Air dilution - prevented by a FGF equivalent to
peak inspiratory flow rate (PIFR).
•These factors suit its use in paediatrics.

25. TT AND MODIFICATIONS. AND MODIFICATIONS.

27. LACK AND BAINSLACK AND BAINS

29. •So almost every thing is around
T

32. •The pattern of controlled ventilation
(control is with us),
•Low resp. rate
•High tidal volume
•Less inspiration time.
•Long exp. Pause.
•------ then we need less FGF

33. Curve -- normocarbiaCurve -- normocarbia

34. Jackson rees FGF req. Jackson rees FGF req.
•Body weight (kg) & Fresh gas flow (L/min)
•5 kg : 1.4 - 1.8 5 kg : 0.6
•10 kg : 2.4 - 3.2 10 kg :1.1
•20 kg : 4.1 - 5.4 20 kg : 1.9
•40 kg : 7.2 - 9.6 40 kg : 3.3
↑ ↑
SPONT CONTROLLED
Ventilator – 15 breaths/min
TV 10 ml/kg approx --ok

35. D, E and FD, E and F
•In simple terms, controlled ventilation is
possible with 70 ml/kg and spontaneous
ventilation may need upto 250 ml/kg to
maintain normocarbia.
• It should be emphasized that these values
are guidelines only; if there is evidence of
rebreathing (e.g. an increase in the end tidal
CO2 concentration or unexpected
hyperventilation), the flow rate should be
increased.
•Functional analysis of D, E and F are similar.

36. CIRCLE SYSTEMSCIRCLE SYSTEMS

38. APPREHENSIONS IN PAEDIATRIC USEAPPREHENSIONS IN PAEDIATRIC USE
•Connectors, unidirectional valves and canisters
cause
•↑ dead space
•↑ resistance
•Is low flow possible?
introduction of low resistance valves, improved
soda lime canisters and low dead space
connectors--done
low flow possible - studies prove
Heat and fluid conservation
efficient scavenging
Inhalational agent use decrease

39. Unidirectional valvesUnidirectional valves
•Resistance inversely
proportional fourth
power of radius.
•Pressure needed to lift
the valve
P = W ÷ D
2
small light discs-- ok

40. Divided airway adapter revell circulatorDivided airway adapter revell circulator

41. Miscellaneous systemsMiscellaneous systems
•Humphrey ADE
•MERA F
are also used in paediatrics.
SO ! WHAT IS THE CARRY HOME
MESSAGE?

42. Summary Summary
•A number of systems are in vogue.
•Dead space, resistance, ↑ CO2
production, light weighted systems –
points to think about.
•Controlled ventilation is most often
used
•Jackson rees,
•Mapleson D and Bains
•Circle

43. •Jackson rees:Spont. –ok but FGF 200-
250 ml/kg Contrl. Good 70- 80 ml/kg
•Mapleson D and Bains : same as JR
•Circle: Paed. Special circle?
•Adult system with paediatric tubing ok
•Low flow anaesthesia,less agent and
FGF costs,scavenging,humidity and
heat conservation –thoughts swing in
favour of circles in the coming era

44. After all, its us we decide After all, its us we decide
•We should know the
system.
•We should know that
ETT offers maximal
resistance
•We should be well
versed ,experienced
•A proper pre op check
of the system is a
must

45. •When you inhale you inspire
•But when you don’t ---

47. Questions for PGs Questions for PGs
•1. What will happen if Mapleson A is
connected to a ventilator?
•2. What will happen if bain’s circuit is
connected to a ventilator?
•3.What is the amount of gas let out thro spill
valve each time? RR 15/min- tidal volume
500 FGF 4.5 l/min.
1= Mapleson a system becomes dead space
2. It becomes mapleson E
3. Think and answer

48. Thank youThank you