Mechanical Ventilation in the Neonate

RC 290

CPAP

Indications:• Refractory Hypoxemia

– PaO2 < 50 on an FIO2 of 60% or >– Many hospitals use 50% as the upper limit before changing

to CPAP

• Transitional therapy between simple O2 therapy and mechanical ventilation– Usually in the early stages of a disease or when recovery

starts

• Any disease that causes increased elastic resistance and alveolar instability

CPAP: EFFECTS

• Increased FRC , ie, back towards normal• Decreased shunt• Adequate PaO2 at minimal FIO2• W.O.B. ?

– By increasing FRC, CPAP should decrease the W.O.B.– However, it requires active exhalation which increases

W.O.B.

• To go on CPAP an infant needs to be breathing spontaneously and to have normal (or slightly lowered) PaCO2

CPAP: Administration Techniques

• Mostly flow resistors– To change CPAP level,

change either flow rate or the amount of resistance

• May be administered via mask, nasal cannula, hood, or ET tube– An orogastric tube may be

needed if using a mask, cannula, or hood

CPAP: Hazards

• Hemodynamic compromise

• Pulmonary Baro/Volutrauma

• Gastric insufflation

CPAP: Management Technique• Start at current FIO2 or slightly >• Start at 4-5 cmH2O• Titrate level in 1-2 cmH2O increments until PaO2 is

acceptable – Watch pulse oximeter or TCM as well– Maximal level is usually 10-12 cmH2O

Weaning:• Get FIO2 to 50% or <• Decrease CPAP in 1-2 cmH2O increments

– Monitor for stability in vital signs, ABGs, and pulse oximeter

• If on ET tube, extubate when CPAP is 2 cmH2O

Mechanical Ventilation:Indications

• Any acute or chronic cardiopulmonary insufficiency– May be due to problem with lung, cardiovascular

system, CNS, or various metabolic disorders

Clinical signs:• ARF: pH = 7.25 or < with a PaCO2 of 55 mmhg

or >• Repeated A-B spells • FIO2 requirement of 50% or >

– Some hospitals may use 60% or >

Mechanical Ventilation: Hazards

• Problems associated with increased mean ITP– Hemodynamic compromise, pulmonary

baro/volutrauma

• Mechanical failure– Usually human failure!

• BPD, ie, Bronchopulmonary Dysplasia

Mechanical Ventilation: Modes

• All modes are available to the neonate

• Time cycled IMV (with pressure limiting)– Newer neonatal vents may

allow volume cycled IMV

• Newer neonatal ventilators can do A/C volume cycle or pressure control

Time Cycled IMV:Initial Settings

• FIO2: Current FIO2 or slightly >

• PEEP: minimum of 2 cmH2O (because of ET tube)– Usual range is 2 – 7 cmH20

but may go higher

• Rate: 10-30 (depends on PaCO2 prior to CMV)

• Inspiratory time (IT): .15 to 1.5 seconds– Usually .5 to .6 seconds for

starters– Maintain adequate Vt and I:E

ratio

• Peak Pressure (PIP): 10 to 20 cmH2O– Assess breath sounds and chest

expansion

• Flowrate (Peak Flow): 4-10 LPM– Depends on ventilator and size

of infant

Target Values: MAP

Mean Airway Pressure• Average pressure exerted on the airways from the start of one

inspiration until the next• Is affected by IT, PIP, Rate, and PEEP• Baro/Volutrauma seen with values above 12 cmH2O• It is the most powerful influence on oxygenation!

Target Values: ABGs

• pH: 7.25 – 7.45

• PaCO2: 35-55 mmhg– Increased chances of intracranial bleed if above

55 mmhg

• PaO2: 50 – 70 mmhg– Capillary is 35 – 50 mmhg

Adjusting Ventilator Parameters

• To change PaCO2 ONLY, change rate– To increase PaCO2 only, decrease rate– To decrease PaCO2 only, increase rate

• To Change PaO2 ONLY, change FIO2, PEEP, or IT– FIO2 is changed in 1- 5 % increments– PEEP is changed in 1 – 2 cmH2O increments

• To change both PaCO2 and PaO2 at the same time, but in opposite directions, change PIP– Increase PIP, PaO2 increases, PaCO2 decreases– Decrease PIP, PaO2 decreases, PaCO2 increases

Increased I time and Inverse IE Ratios

• Used when increasing FIO2 and PEEP is NOT raising PaO2

• Used for increased elastic resistance with short time constant– RDS, atelectasis, bilateral pneumonia

• Rate should be no greater than 30 and PIP should be no greater than 30 cmH2O

Weaning

• Decrease FIO2 and PEEP (as already described for CPAP)

• When rate is down to 10-12, try CPAP• Decrease PIP to 10-20 cmH2O• When stable on CPAP of 2 cmH2O and FIO2 of

40% or less, extubate• Start weaning with the parameter that is most

extreme• Monitor for stability of vital signs, TCM values, and

pulse oximeter values at all times

Ventilator care requires a team effort. Everyone involved has toget along and trust one another!