LINCOLN HOSPITAL
PICU
Basic Principles & Guidelines for Starting Mechanical Ventilation
in Pediatrics Patients
I.
Indications: Mechanical ventilation is indicated:
A.
To provide respiratory support in patients who cannot maintain normal
ventilation and/or oxygenation on their own.
B.
For elective hyperventilation (ie. acute cerebral edema / impending herniation..)
C.
To decrease metabolic demands in patients with severe hemodynamic
compromise (shock)
II
Types of respirators: Select the respirator according to patient’s age and weight
Most commonly use respirators in pediatrics.
A.
Bear cub newborn respirator. Mainly used in the NICU but it can be used for any
infant less than 6 months of age or less than 6 kg.
The “new model” BP 750 with the following up-grated features:
 options for assist control mode and SIMV instead of IMV
 can monitor exhale tidal volumes
 it has graphic capabilities.
B.
PB7200 and the new model PB 840 - “adult respirator”: can be used for children
>1 years old and / or > 10 kg
E.
BiPAP Unit.
III.
Basic Physiologic Concepts: to be considered before writing respiratory settings:
A.
Compliance of the lungs and chest: it translates as the degree of stiffness.
If the compliance is low (stiff lung ie. severe pneumonia, pulmonary
edema), you are going to need higher pressures (PIP) to deliver a tidal
volume (TV).
Compliance is expressed as = Change of Volume
Change of Pressure
B.
Resistance: the degree of “difficulty”, (expressed as pressure gradient) of the air
flowing through the airway. The narrower the airway, the higher the resistance.
If the resistance is high, not only you are going to reach/need higher pressures to
deliver the TV, but you are also going to need longer expiratory time to avoid air
trapping. Consider using lower respiratory rates and higher flows, limiting the
PIP to 40 cm H2) to prevent barotrauma. Another option is “control
hypoventilation” (you do not have to “normalize” the pCO2 at the expense of
barotrauma), as long as proper oxygenation is being achieved.
C.
Time Constance (TC) is expressed as the product of compliance x resistance.
A concept that helps us to adjust the rate of ventilation.
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You need at least 3 x TC to distribute the TV to the majority of the
respiratory units. To ventilate lungs with mildly decreased compliance but
higher resistance (increased TC), i.e. severe airway obstruction, you will
need more inspiration and expiration time to be able to fill and empty the
lungs properly to prevent airtrapping, therefore you will prefer to start with
a low respiratory rate. On the other hand, if the lung has severe decreased
compliance (stiff) and only mildly increased resistance (decreased time
constance), i.e. severe pneumonia. ARDS; you will need less expiratory
time. Therefore you can ventilate this patient with higher rates without
airtrapping.
D.
Cycling: Refers to how the respirator is programmed to end the inspiratory
phase and switch to passive expiration.
1.
Time cycle: The respirator will end inspiratory phase at the end of
the set I: time. Time cycle respirators: Bear Cub (NB respirator),
2.
Volume cycle: Respirator will end inspiratory phase at the end of
the set tidal volume. The PIP will change according to lung
compliance/resistance (as above).
A pressure limit can be set to time cycle as well as volume cycle; when this
point is reach; a pop-off valve will open to exhale the rest of the Tidal Volume
not yet delivered.
IV
Modes of Ventilation: refers to the different ways the respirator can be set to deliver the
desired TV/ventilation. Among the numerous modes currently in use, the most common
modes are:
A.
CMV (Continuous Mandatory /Assist Control Ventilation): in this mode every
patient breath will be assisted to “guarantee” the deliver of the set TV; if the popoff peak pressure valve is not limited. If the patient is not breathing the
machine takes control with the set up rate or the back-up (apnea) rate. This is a
common mode to start mechanical ventilation in adults. It does carry a higher risk
of barotrauma when dealing with stiff lungs. Pediatric patients who are not deeply
sedated may not tolerate this mode of ventilation.
B.
IMV/SIMV: Intermittent mandatory ventilation, synchronize IMV.
You will see machine and patients breath interposes. The patients own rate and
TV plus the machine rate and set TV. All the new model ventilators have SIMV
only where the machine synchronizes the deliver of the machine breaths with the
patient’s breath. If the patient does not breathe the machine takes over. You can
start all pediatric patients in this mode.
C.
Pressure Support (PS): Machine is programmed to assist each patient’s
respiratory effort with a positive pressure to augment the TV (TV is not
set, this will change according to lung compliance and patient effort).
Patient controls the rate. If patient does not breathe the machine will not deliver a
breath if no back-up ventilation is set.
D.
SIMV with PS which is a combination of modes B & C.
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E.
F.
V.
CPAP: Continues positive airway pressure. Here patients control their
own respiratory rate and TV. CPAP will support or raise the FRC (function
residual capacity), and improve air exchange (oxygenation)
BIPAP is a combination support of CPAP expressed as EPAP (expiratory
positive airway pressure and pressure support (PS) expressed as IPAP (inspiratory
positive airway pressure). In the spontaneous mode, patients control their own
rate. TV is augmented by IPAP and FRC is maintained/augmented by EPAP. It’s
recommended that IPAP should always be set higher than EPAP. The Bi-pap
machine can be used to deliver non-invasive ventilation when in the S/T/ mode.
Starting Respiratory Settings:
1.
2.
3.
4.
5.
6.
Select the type of respirator as above (section II).
Bear Cub, PB7200, Servo, VIP Bird or CPAP /BiPAP Unit
 Evaluate patient’s respiratory physiological condition at the time of intubation
and set up your goals of respiratory support therapy. Always consider risk and
benefits of therapy.
Select mode: SIMV, PS, SIMV with PS, CPAP, BiPAP, CMV (A/C).
Select rate: According to patient’s age and respiratory physiological
abnormality.
<1 year: 25-30 bpm
1-5 years: 20-25 bpm
5-10 years: 15-20 bpm
>10 years: 12-14 bpm
Tidal Volume (TV): 8-10 ml/kg, when using volume cycle ventilation
(PB7200, SERVO, VIP volume mode)
* If using time cycle ventilation (Bear Cub, VIP time cycle mode), you
can not set TV, this can be read (exhale TV) in the displayed monitors and
it will be affected by the I:time, flow and PIP limit.
PIP: When using time cycle pressure control.
 For small infants < 2 mo and no significant lung disease (~normal
compliance), can start with PIP of 15
 For older infants with lower respiratory pathology ( compliance) start
with PIP 20-25 cmH2O.
 If using volume control ventilator (PB 7200 , Servo, VIP) you do not set
the PIP but you read it in the display monitor. This indicates the lung
compliance. You set up a PIP limit about 10 cm HO2 over the reached PIP
(try not to exceed 40 cmH02). The ventilator will alarm when the set up PIP
limit is reached)
Inspiratory time (I:time): 0.5-1.0 second. to be set when using in the bear cub or
VIP in the time cycle mode
 Start at 0.5 sec and adjust according to patient’s needs. Patients with severe
hypoxic respiratory failure and poor lung compliance ie. severe pneumonia
may need longer I time to improve oxygenation
 When using SERVO set up I:time at 25%. The machine will adjust I:time
according to respiratory rate (patient and machine breaths) to keep a certain
I: E rate show. (Pause Time is set at 0%)
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
7.
8.
8.
10.
If using volume cycle respirator (PB7200), you do not set the I:time directly,
but you read it in the displayed monitors as a variable of flow rate (low flow longer I:time; high flow - shorter I:time).
 I: E rate show is a derivative of respiratory rate and I:time.
Flow rates need to be set when using respirators in the volume cycle and time
cycle mode. (Bear Cub, PB 7200, VIP).
The SERVO ventilator adjusts its flow rate automatically; (no need to set).
 A “ball park” guideline to start/calculate is 6 x MVV
MVV (Minute Volume Ventilation) = TV x RR
Infants: < 6 mo
10 – 12 L/min
> 6 mo < 1yo
12 – 14 L/ min
Children 1 – 2 yo
15 – 20 L/min
2 – 5 yo
20 – 25 L/min
5 – 10 yo
25 – 30 L/min
10 – 15 yo
30 – 35 L/min
> 15 yo
35 – 40 L/min
Fi02 50-100% as patient needs to maintain saturation > 95%.
Fi02 can be adjusted with pulse oximeter, if this is reliable
(Patient is well perfused), no need to wait for ABG’S and find a
Pa02 of 300 mmHg!!!)
PEEP: 2-4 cmH20 according to 02 requirements. Patients with hypoxic respiratory
failure secondary to parenchyma disease ie: Pneumonia, Pulmonary Edema will
require higher PEEP to improve oxygenation.
If low O2 requirement, (<40%) use a PEEP (4 to 6), if higher oxygen
requirement (>50%) consider higher PEEP (> 8 to 10).
Sensitivity. Usually is set up at - 2
Checklist to review when writing orders for respiratory settings: Remember that machines
DO only what we ask (program) them to do. Stay with your patient at the bedside all the time
when he/she is being connected to the respirator and check for:
 Chest expansion (Does it expand too much? Consider lowering the PIP, or the VT) - Does not
expand enough; is there a leak?; consider a higher TV to compensate for the leak, or a higher
PIP if the lung compliance is low (stiff lung)
 Air entry symmetry; it asymmetric, may need to adjust ET tube placement.
 I:E rate show (try to breathe yourself with patient’s mechanic rate. Does it “feel” confortable?
Is the inspiratory phase is too short? (consider decreasing the flow or increasing the I:time,
and/ or decreasing the rate).
 Connect patient to ET CO2 and Pulse Oximeter monitor and adjust Fi02 according to 02
saturations as above.
 If you feel comfortable with the respiratory pattern/assistance, sedate patient with
Lorazepam and /or Fentanyl; if this has not already been done. (Avoid paralyzing agents)
 Send blood gases, arterial or capillary.
 Place an arterial line if anticipating “long term” assistance or unstable patient who will need
frequent respiratory adjustments.
(Capillary blood gases can be sufficient in “short cases”. VENOUS BLOOD GASES ARE
NOT ACCEPTABLE TO ASSESS RESPIRATORY STATUS.
Prepared by Dora Alvarez, MD
Revised 3-04
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