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2. 2 Dr.Wahid Helmy pediatric consultant. Basics of Mechanical Ventilation in Neonates

3. 3 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).

4. What is it?

5. Pulmonary Mechanics

6. 6 1)Tidal Volume (Vt) ◘Air inspired or expired in one breath. ◘ (Vt) = 6-10 mL/kg/Breath. ◘ RR is usually 30-60 BPM. ◘ minute volume = (Vt- Dead space)x RR. ◘ Tidal Volume is proportional to (PIP) and to Dynamic Lung Compliance.

7. 7 2)Compliance = 0.004 L/cmH2O. ◘ Elastic - recoil properties of the lung and chest wall. ◘ Estimated from simultaneous changes in volume and pressure. ◘ Compliance (mL/cmH2O) :- = Change in volume (mL) = 0.004 L/cmH2O. Change in pressure(cmH2O)

8. 3)Resistance = 30cm H2O/L/sec ◘ Describes property of the lungs that resists airflow –Airway resistance. –Tissue resistance. ◘ Resistance = Change in pressure (cmH2O ) Change in flow (L/sec ) ◘ Resistance during inspiration < during expiration.

9. 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. Time constant = Resistance X Compliance ◘ Time constant = Resistance X Compliance

10. 4) Time constant,cont., Time constant = Resistance X Compliance ◘ Time constant = Resistance X Compliance Example ◘ Example 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.

11. Types of Mechanical Ventilators

12. Volume-cycled ventilators. Pressure ventilators. Pressure-limited, time-cycled, continuous- flow ventilators Patient–triggered ventilators (PTV).

13. Pressure-Limited, Time-Cycled, Continuous-Flow 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.

14. What is it?

15. Parameters of mechanical ventilation

16. Peak Inspiratory Pressure (PIP) The maximum pressure reached during inspiration. If PIP is too low → low VT. If PIP too high → high VT → –Barotraumas and BPD – Hyperinflation and air leak –Impedance of venous return ↑↑↑ tidal volume, is more injurious to the lung than ↑↑↑ (PIP).

17. PEEP (Optimum (PEEP) is 4-6 cmH2O). Optimum (PEEP) →prevent lung collapse and maintain stability of the alveoli. below Optimum (PEEP) lung volume is not maintained. High PEEP >8 cmH2O – Reduces gradient between PIP & PEEP→ (↓ VT). –Decreases venous return. –Increases pulmonary air leaks. –Produces CO2 retention.

18. (FiO2) Increase in FiO2 alters alveolar oxygen tension, provides a larger diffusion gradient, and improves oxygenation. Oxygen and Paw should be balanced to minimize lung damage. During weaning, Paw should be reduced before a very low FiO2 is reached. If PIP is not decreased until a low FiO2 is reached, a high incidence of air leak is observed.

19. 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. can tolerate (RR60-70 Bpm) and short (Te) without marked gas trapping. Determines minute ventilation(RR×VT),thus CO2 elimination.

20. Ti and Te InspiratoryTime (Ti) Inspiratory Time (Ti) Usually adjusted between 0.35-0.6 second Depends on the pulmonary mechanics: –Compliance. –Resistance. –Time constant.

21. I:E ratio I:E ratio should NOT be less than 1:1.2 It should NOT be reversed Ti of 1.0 second or longer → active expiration, fighting the ventilator, slower weaning, and a high incidence of pneumothorax.

22. Flow Volume of gas passed / time unit (liter/minute). Flow rates of 6-10 liter/min are usually sufficient. High flows can lead to turbulence, an increase in resistance, and gas trapping.

23. mean airway pressure It is ameasure of the average pressureto which lungs are exposed during the respiratory cycle. It isthe factor (other than FiO2) that determines oxygenation. An ↑ in PIP and PEEP→ ↑ oxygenation more than ↑ in the I:E ratio. NB., ↑ ↑ ↑ Paw →alveolar over distension with right to left shunt.

24. Pressure gradient Peak inspiratory pressure (PIP): pressure gradient berween (PIP) & (PEEP) affects alveolar ventilation. Increase in PIP will: –↑ tidal volume. –↑ CO2 wash. –↑ Paw which improve oxygenation.

25. Minute alveolar ventilation = (Tidal volume – Dead space) X Frequency. = (Tidal volume – Dead space) X Frequency. Tidal volume,is determined mainly with pressure gradient between inspiration and expirationTidal volume,is determined mainly with pressure gradient between inspiration and expiration i.e. (PIP) minus (PEEP).

26. Gas Exchange during Assisted Ventilation Carbon dioxide (CO2) Exchange It depends on Alveolar ventilation. OxygenExchangeDiffuses rapidly from the blood into the alveoli. OxygenExchange Oxygen exchange depends largely on the matching of perfusion with ventilation.

27. Modes of venilation Who is the Commande?

28. A)Non-triggeredModes. A) Non-triggered Modes. يتم تحديد معدل التنفس والضغط بواسطة الجهاز دون النظر لمعدل تنفس الطفل 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.

29. ◙ Infant’s respiratory drive and rhythm determine the rate of ventilation. 1.Assist/Control(A/C)- Synchronized Intermittent Positive Pressure Ventilation (SIPPV 2.Synchronized Intermittent Mandatory Ventilation (SIMV). 3.Pressure Support Ventilation (PSV) 4.Volume Guarantee (VG) ventilation. VolumeGuarantee(VG)ventilation ◙ Volume Guarantee (VG) ventilation ◙ Pressure-controlled ventilation It delivers a preset VT, this volume is continuously monitored by the ventilator and the pressure may increase or decrease to guarantee the target VT. Addition of VG to A/C or SIMV results in: –Less risk of volutrauma –Auto-weaning of PIP (may reduce barotraumas B)Patient-triggeredVentilation(PTV ) B) Patient-triggered Ventilation (PTV )

30. Patient–Triggered Ventilators (PTV) Modification of conventional ventilation. the patient is able to initiate ventilator breaths. There is a sensor of thoracoabdominal movement, airflow, or airway pressure to indicate the onset of the inspiratory efforts, and so triggering the ventilator setting.

31. Patient–Triggered Ventilators (PTV) (cont.) If the infant does not generate an adequate inspiratory effort during a preset period, the ventilator will deliver a nontriggered breath. Result in improved tidal volume and blood gases but may lead to hyperventilation in tachypneic infants.

32. Patient–Triggered Ventilators (PTV) (cont.) PTV is used in two modes: 1. Synchronized Intermittent Mandatory Ventilation (SIMV) –A single triggered breath is given in equal windows of time, with the other patient breaths occurring during each window not assisted. –This way the rate can be slowly reduced with all assisted breaths well-synchronized.

33. Assist / Control mode (sippv) (A/C) 2. Assist / Control mode (A/C) –All breaths are triggered, the patient controls the ventilator rate, and weaning is accomplished by reducing the PIP. –Advantage is reduction in cerebral blood flow variability. –Weaning from ventilator is facilitated in both A/C and SIMV. –These ventilators reduce the duration of assisted ventilation and facilitate weaning.

34. Indications of Mechanical Ventilation Absolute indications If any of the following is present: 1. Severe hypoxemia with PaO2 less than 50 mmHg despite FiO2 of 0.8. 2. Respiratory acidosis with pH of less than 7.20 to 7.25, or PaCO2 above 60 mmHg. 3. Severe prolonged apnea.

35. Indications of Mechanical Ventilation (cont.) Relative indications 1. Frequent intermittent apnea unresponsive to drug therapy. 2. Early treatment when use of mechanical ventilation is anticipated because of deteriorating gas exchange. 3. Relieving work of breathing in an infant with signs of respiratory difficulty. 4. Initiation of exogenous surfactant therapy in infants with RDS.

36. Blood Gases Changes by Ventilator Setting Effect PaO2PaCO2 Ventilator setting changes IncreaseDecrease Increase PIP Increase Increase PEEP IncreaseDecrease Increase rate Increase------- Increase I:E ratio Increase------- Increase FiO2 IncreaseDecrease Increase flow

37. ET Size Endotracheal tube internal diameter Infant weight(gm) 2.5mm< 1,000gm 3.0mm1,000 - 2,000 3.5mm2,000 - 3,000 3.5 - 4.00mm> 3,000

38. Initial Setting of Mechanical Ventilation Initial settings As indicated Fio2 8-10l/min Systemic flow 60 breaths / min Rate 1:2 - 1:3 Ti/Te 18 - 22cm H20 Good breath sounds PIP 3 - 5cm H20 PEEP

39. PIPPEEP Subsequent settings Increase Low PaO2, Low PaCo2 Increase Low PaO2, High PaCo2 Decrease High PaO2, High PaCo2 Decrease High PaO2, Low PaCo2

40. Monitoring The Infant during Mechanical Ventilation Obtain an initial blood gas within 15-30 minutes of starting mechanical ventilation. –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.

41. Deterioration during Mechanical Ventilation Sudden clinical deterioration Mechanical or electrical ventilator failure. Disconnected tube or leaking connection. Endotracheal tube displacement or blockage. Pneumothorax.

42. Gradual deterioration Inappropriate ventilator setting. Intraventricular hemorrhage. Baby fighting against ventilator. PDA. Anemia. Infection.

43. Paralysis and Sedation  The use of neuromuscular blockade is not routinely indicated.  It has been advocated in infants requiring mechanical ventilation with a high rate or pressure, and who become increasingly agitated when their spontaneous respiration is out of phase with the ventilator, resulting in decreased effectiveness of mechanical support.

44. Paralysis and Sedation (cont.)  Paralysis may worsen oxygenation in infants with RDS as it may result in decreased dynamic lung compliance, increased airway resistance, and the removal of the infant’s respiratory effort contribution to tidal breathing.  As a result, it is necessary to increase ventilator pressure after initiation of neuromuscular blockade.

45. Weaning FiO2 and PIP are weaned first. Decrease PIP as tolerated and as chest rise diminishes. When PIP is around 20, attention is directed to FiO2 and then to the respiratory rate alternating with each other, in response to assessment of chest excursion, blood gas results, and oxygen saturation.

46. Weaning (cont.) As frequency is decreased, Te should be prolonged. weaning to endotracheal CPAP may begin when PIP has been stable between 15-18 cmH2O, and FiO2 is less than 0.4. The infant can be weaned to oxygen hood when he/she requires less than 4 cmH2O of end expiratory pressure.

47. Weaning (cont.) Atelectasis after extubation is common in preterm infants recovering from RDS. Use of nasal CPAP may prevent atelectasis. Steroids are not routine before extubation, but if there was prolonged intubation or previous failed attempts of extubation, a short course of steroids may facilitate extubation. If strider caused by laryngeal edema develops after extubation, racemic epinephrine aerosols and steroids may be helpful.

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