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Educational Resources  PICU resident handbook with relevant PICU topics is available at u.html Hard copy.

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Presentation on theme: "Educational Resources  PICU resident handbook with relevant PICU topics is available at u.html Hard copy."— Presentation transcript:

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2 Educational Resources  PICU resident handbook with relevant PICU topics is available at u.html Hard copy is available in the resident call room.

3 PICU chapters at  Monitors in ICU  Vascular Access  Codes  ICP management  Status Epilepticus  Sedation  Pediatric Airway  Airway Management  Mechanical Ventilation  ARDS  Status Asthmaticus  Inotropes  Shock  Sepsis  Meningococcus

4 PICU chapters at  Cardiomyopathy  Liver Failure  Acute Renal Falilure  Fluids, Electrolytes, Nutrition  Oncology  Transfusions  DKA  Submersion Injuries  Brain Death  End of life issues

5 PICU Tables at peds.stanford.edu  Sedation  Inotropes  Shock

6 MECHANICAL VENTILATION SARASWATI KACHE, M.D. Clinical Assistant Professor

7 Spontaneous respiration vs. Mechanical ventilation  Natural Breathing  Negative inspiratory force  Air pulled into lungs  Mechanical Ventilation  Positive inspiratory pressure  Air pushed into lungs

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9 Initiate Mechanical Ventilation  Hypoxia  Hypercarbia  Airway protection  (Decrease demand in cases of poor cardiac output)

10 Ventilators: a Schematic

11 IMPORTANT TERMS  TIME  I - Time: amount of time spent in inspiration  E - Time: amount of time spent in expiration  Volume  Amount of tidal volume that a patient receives  Pressure  Measure of impedance to gas flow rate  Flow  Measure of rate at which gas is delivered

12 A Few More Terms  PEEP = positive end expiratory pressure  Pressure maintained in the airways at the end of exhalation  Keeps Alveoli from collapsing  PIP = peak inspiratory pressure  Point of maximal airway pressure  Delta P = the difference between PIP – PEEP  MAP = mean airway pressure

13 ICU Ventilator: Evita 4

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15 Types of Ventilation ….

16 Compliance = Volume Pressure

17 Volume Ventilation  Preset  Volume  PEEP  Rate  I-time  FiO2  Ventilator Determines  Pressure required  Advantages  Guaranteed minute ventilation  More comfortable for patient  Draw-backs  Large ETT leak  Not optimal for poorly compliant lungs

18 Pressure Ventilation  Preset  PIP  PEEP  Rate  I-time  FiO2  Vent determines  Tidal volume given  Advantages  Provides more support at lower PIP for poorly compliant lungs  Draw back  Minute ventilation not guaranteed

19 Volume vs. Pressure

20 Amount of support to give…

21 MODES OF VENTILATION  Controlled Mechanical Ventilation (CMV)  Assist Control (AC)  Continuous Positive Airway Pressure (CPAP)  Intermittent Mandatory Ventilation (IMV)  Synchronized Intermittent Mandatory Ventilation (SIMV)  Pressure Support  Volume Support  Pressure Regulated Volume Control (PRVC)

22 Assist Control  Volume or Pressure control mode  Parameters to set:  Volume or pressure  Rate  I – time  FiO2

23 Assist Control  Machine breaths:  Delivers the set volume or pressure  Patient’s spontaneous breath:  Ventilator delivers full set volume or pressure & I-time  Mode of ventilation provides the most support

24 SIMV Synchronized intermittent mandatory ventilation  Volume or Pressure mode  Parameters set:  Volume or pressure  Respiratory rate  I – time  FiO2  Pressure support

25 SIMV Synchronized intermittent mandatory ventilation  Machine breaths: d  Delivers the set volume or pressure  Patient’s spontaneous breath:  Set pressure support delivered  Mode of ventilation provides moderate amount of support  Works well as weaning mode

26 Pressure Support  Parameters set:  Pressure support,  FiO2  Machine breaths: none *****  Patient’s spontaneous breaths: set pressure support delivered  Purposes:  Final step prior to extubation  Re-train muscle strength

27 Continuous Positive Airway Pressure (CPAP)  Positive airway pressure maintained throughout respiratory cycle: during inspiratory and expiratory phases  Can be administered via ETT or nasal prongs

28 Managing the Patient…

29 Pulmonary Compliance  Compliance = Volume Pressure  Monitor patient’s clinical changes  i.e. as compliance improves  Volume mode: required pressure decreases  Pressure mode: generated volume increases

30 Hypoxia  Hypoventilation: decreased alveolar ventilation, i.e. CNS depression  Diffusion impairment: abnormality at pulmonary capillary bed  Shunt: blood flow without gas exchange  Intra-pulmonary  Intra-cardiac  Ventilation-perfusion mismatch: Both dead space and shunt abnormalities

31 Treating Hypoxia  Increase FiO 2 : >60% toxic to lung parenchyma  Increase mean airway pressure  PEEP : not too much, not too little  PIP  I-time

32 Hypercarbia  Decreased minute ventilation  Respiratory rate  Tidal volume  Treatment:  Increase respiratory rate: assure I-time not too short as rate increased  Increase tidal volume  Allow permissive hypercarbia

33 Pulmonary Disease: Obstructive Airway obstruction causing increase resistance to airflow: e.g. asthma  Optimize expiratory time by minimizing minute ventilation  Bag slowly after intubation  Don’t increase ventilator rate for increased CO 2

34 Pulmonary Disease: Restrictive Compromised lung volume:  Intrinsic lung disease  External compression of lung  Recruit alveolia, optimize V/Q matching  Lung protective strategies  High PEEP  Pressure limiting PIP: cmH2O  Low tidal volume: 4-8 ml/kg  FiO2 <60%  Permissive hypercarbia  Permissive hypoxia

35 High Frequency Oscillatory Ventilation

36 HIFI - Theory  Resonant frequency phenomena:  Lungs have a natural resonant frequency  Outside force used to overcome airway resistance  Use of high velocity inspiratory gas flow: reduction of effective dead space  Increased bulk flow: secondary to active expiration

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39 HIFI - Gas Transport  Conventional bulk flow  Coaxial flow: different flow directions in central and peripheral air columns  Taylor dispersion: gas molecules disperse beyond the bulk flow front

40 HIFI - Gas Transport  Molecular diffusion: gas mixing within alveoli  Pendelluft phenomenon: inter- alveolar gas mixing due to impedance differences

41 HIFI - Advantages  Advantages:  Decreased barotrauma / volutrauma: reduced swings in pressure and volume  Improve V/Q matching: secondary to different flow delivery characteristics  Disadvantages:  Greater potential of air trapping  Hemodynamic compromise  Physical airway damage: necrotizing tracheobronchitis  Difficult to suction  Often require paralysis

42 HIFI – Clinical Application  Adjustable Parameters  Mean Airway Pressure: usually set 2-4 higher than MAP on conventional ventilator  Amplitude: monitor chest rise  Hertz: number of cycles per second  FiO2  I-time: usually set at 33%

43 HIFI - Applications Oxygenation  Mean airway pressure  FiO2 Ventilation  Amplitude  Hertz  I-Time

44 Scenario #1 The following blood gas is presented to you for a 4yr patient that is now 3hours post-op from an OLT / 24 / 250 / 20 / -4 The ventilator settings are SIMV PC/PS PEEP – 4, Delta P-28, FiO2 – 50%, RR – 12.

45 Scenario #2 A 8yr female with ALL s/p chemo presents to the PICU with fever and neutropenia 1day prior. She is found with positive blood cultures this AM and got intubated secondary to respiratory failure. It is now 4am and the morning labs show the following ABG: 7.23 / 60 / 58 / 22 / -2 The ventilator settings are SIMV TV - 10cc/Kg, PEEP – 5, PIP – 38, PS – 14, FiO2 – 70%, RR – 20, I-time – 0.7 You go to examine the patient and she is agitated, hypertensive, and with a respiratory rate of 40.

46 Scenario #3 There is a 6 month old patient that presents with RSV bronchiolitis that progresses to severe disease and the patient is now on a HIFI ventilator. The patient’s ABG is as follows: 7.24 / 58 / 75 / 21 / -3 The ventilator settings are as follows: HIFI with MAP – 20, Amp – 28, Hz – 8, FiO2 – 40%. As you are looking at the chest X-ray, the nurse mentions the patient looks more edematous this evening compared to last night.

47 References   Editors: Rogers MC & Nichols DG. Textbook of Pediatric Intensive Care. Baltimore, Willimams & Wilkins,  Cairo JM & Pilbeam SP. Mosby’s Respiratory Care Equipment. St. Louis, Mosby,  Evita 4 Intensive Care ventilator, Operating instructions,  West JB. Pulmonary Pathophysiology. Baltimore, Willims & Wilkins, 1992.

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