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Dr.Wahid Helmy pediatric consultant. Basics of Mechanical Ventilation in Neonates. Ventilator care requires a team effort. Everyone involved has to get along and trust one another !. Prevention of alveolar collapse.

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dr wahid helmy pediatric consultant

Dr.Wahid Helmypediatric consultant.

Basics of Mechanical Ventilation in Neonates

slide2
Ventilator care requires a team effort.

Everyone involved has to get along

and trust one another!

slide3
Prevention of alveolar collapse

◘ Functional residual capacty (FRC).

◘ Surfactant .

◘Elatic-recoil ( compliance).

◘ Intrapleural pressure(-4mmHg) during inspiration and (+4mmHg) during inspiration .

◘ If surfactant is absent , Intrapleural pressure negativity may be increased up to (-20mmHg).

slide6
1)Tidal Volume (Vt)

◘ (Vt) = 6-10 mL/kg/Breath.

◘RR is usually 30-60 BPM.

2) minute volume

= (Vt- Dead space)x RR.

↑ (PIP)→↑Tidal Volume →↑minute volume .

slide7
3) Compliance = 0.004 L/cmH2O.

= Change in volume (mL) = 0.004 L/cmH2O.

Change in pressure(cmH2O)

4)Resistance = 30cm H2O/L/sec

Change in pressure (cmH2O)= 30cm H2O/L/sec

Change in flow (L/sec)

NB., Resistance X Compliance = 1Time constant

1Time constant =0.004 L/cmH2O. X 30cm H2O/L/sec =12

slide8
4)one Time constant = Resistance X Compliance

◘ one time constant → 63% equilibration of pressure inside & outside the alveoli.

◘ we need 3 time constant →97% equilibration of pressure inside & outside the alveoli.

  • If resistance =30cm H2O/L/sec
  • compliance = 0.004 L/cmH2O.
  • One time constant =30 X 0.004 = 0.12 seconds.
  • We need 3time constant to inflate and deflate the lung (3 X 0.12 seconds = 0.36 seconds=Ti ).
  • as aresult Te= 2 or 3 X 0.36seconds.
  • So I/E ratio = 1:2 or 1:3 .
slide10
Types of Mechanical Ventilators
  • Volumev- cycled ventilators.لمجرد المعرفة
  • Pressure ventilators . لمجرد المعرفة
  • Pressure-limited, time-cycled, continuous-flow ventilators .هام جدا
  • Patient–triggered ventilators (PTV).هام جدا
slide12
Pressure-limited, time-cycled,

continuous-flow ventilators Ventilators

  • You select (PIP)→ (pressure-limited).
  • You select inspiratory time → (time-cycled).
  • (Continuous flow) →Fresh heated humidified gas is delivered to the patient throughout the respiratory cycle.
slide14
(PIP) minus(PEEP)
  • (PIP) → The maximum pressure reached during inspiration. If PIP is too low → low VT. If PIP too high → high VT → Hyperinflation and air leak → Impedance مقاومةof venous return.
  • (Optimum (PEEP) is 4-6 cmH2O).
  • High PEEP >8 cmH2O .,→

–Reduces gradient between PIP & PEEP→ (↓ VT) .

–Decreases venous return .

–Increases pulmonary air leaks .

–Produces CO2 retention .

slide15
(FiO2)
  • why Increase in FiO2 improves oxygenation ? ↑ oxygen tension inside the alveoli→ ↑ r diffusion gradient → good oxygenation.
  • Why Oxygen and Paw balance is essentiaL ? to minimize lung damage.
  • Why Paw should be ↓ before a very low FiO2 is reached During weaning. to avoid a high incidence of air leak is observed.
slide16
RR, secrets
  • ↑ RR → ↑ (CO2 wash).
  • RR(60 BPM) allows for PIP reduction in PIP → ↓ incidence of pneumothorax with about 50% .
  • Most neonates have short time constants so they can tolerate (RR60-70 Bpm) and short (Te) without marked gas trapping .
  • RR Determinesيحدد minute ventilation(RR×VT),thus CO2 elimination.
slide17
Minute alveolar ventilation

Minute alveolar ventilation

= (Tidal volume – Dead space) X Frequency.

  • Tidal volume,is determined mainly with pressure gradient between inspiration and expiration i.e. (PIP) minus (PEEP).
slide18
Ti and Te

●(Ti)is .3 - . 5 seconds for LBW

and .5 - .6 seconds for larger infants

●Depends on the pulmonary mechanics:

– Compliance .

– Resistance .

–Time constant.

I:E ratio

● It should NOT be reversed

● I:E ratio should NOT be less than 1:1.2

slide19
mean airway pressure
  • MAP + FiO2 → determines oxygenation.why?
  • An ↑ in PIP and PEEP→ ↑ MAP → ↑ oxygenation more than ↑ in the I:E ratio.
  • NB., ↑↑↑ Paw →alveolar over distension with right to left shunt.

Flow

Flow rates of 6-10 liter/min are usually sufficient.

slide20
Modes of venilation

Who is theCommander?

slide21
A)Non-triggeredModes.

1.Controlled Mandatory Ventilation (CMV) or IPPV:

– IPPV (intermittent positive pressure ventilation ).

–Ventilator rate is set > infant's spontaneous.

– RR (usually 50-80 breaths/min).

2.Intermittent Mandatory Ventilation (IMV):

–Ventilator rate is set < infant's spontaneous breaths.

– RR (<30 breaths/min).

– spontaneous breaths above the set rate are not assisted.

slide22
B) Patient–Triggered Ventilators (PTV)
  • Modification of conventional ventilation ( IMV or IPPV) by adding synchorinization (S).
  • ASensor detect the Inspiratory efforts of the baby by so triggering ( the ventilator setting.
  • the patient is able to initiate (trigger) ventilator breaths.
slide23
PTV is used in two modes
  • Assist Control Mode (A/C) or sippv
    • All breath initiated by patient is triggered= Assist.
    • Back up rate = ippv = ControL MV.
    • If apnea occur at any time baby will be ventilated.
  • Synchronized Intermttent Mandatory Ventilation (SIMV):
    • Preset rate that is triggered,
    • other patient breath is not assisted.
slide24
Indications of Mechanical Ventilation
  • hypoxemia→ with PaO2 less than 50 mmHg despite FiO2 of 0.8.
  • Respiratory acidosis → pH of less than 7.20 to 7.25, or PaCO2 above 60 mmHg.
  • Severe prolonged apnea.
  • Frequent intermittent apnea unresponsive to drug therapy.
  • Relieving work of breathing in an infant with signs of respiratory difficulty.
slide29
Monitoring The Infant during Mechanical Ventilation
  • (ABG)) .,
    • Obtain a blood gas within 15-30 minutes of any change in ventilator settings.
    • Obtain a blood gas every 6 hours unless a sudden change in the infant's condition occurs.
    • Continuous monitoring of the O2 saturation level as well as the HR and RR is necessary.
slide30
Paralysis and Sedation
  • It is not routinely indicated.
  • It may be used in irritable infants with their spontaneous respiration is out of phase with the ventilator( as in modes with preset rates as in ippv and imv) .
  • in infants with RDS→ ↓dynamic lung compliance →↑ airway resistance, the removal of the infant’s respiratory effort contribution to tidal breathing.
  • after initiation of neuromuscular blockadeit is necessary to increase ventilator pressure
slide31
Weaning
  • Parameters gradually decreased (PIP 2 cm H2O, FiO2 5%, Rate 5 BPM).
  • 1. Reduce FiO2 to 80% before changing PIP, I:E or PEEP.
  • 2. Reduce PIP as clinically indicated.
  • 3. Reduce FiO2 to less than 60%
  • 4. Reduce inspiratory time.
  • 5. Reduce PIP to 10-14 cm H2O (Larger babies may be extubated with PIP 14-18)
  • 6. Reduce rate to 20 -40 /BPM then Te should be prolonged.
slide32
Weaning (cont.)
  • 7.preterm infants → Use of nasal CPAP → to avoid atelectasis.
  • 8.prolonged intubation or previous failure of extubation → a short course of steroids may facilitate extubation.
  • 9.If stridor caused by laryngeal edema develops after extubation, →nebulization with adrenaline.
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