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Principles of mechanical ventilation 2
- 1. PRINCIPLES OF MECHANICAL VENTILATION and BLOODGAS INTERPRETATION SAMIR EL ANSARY ICU PROFESSOR AIN SHAMS CAIRO [email protected]
- 2. Global Critical Care https://www.facebook.com/groups/1451610115129555/#!/groups/145161011512 9555/ Wellcomein our new group ..... Dr.SAMIR EL ANSARY
- 3. Definitions • Tidal Volume(TV): volume of each breath. • Rate: breaths per minute. • Minute Ventilation (MV): total ventilation per minute. MV = TV x Rate. • Flow: volume of gas per time.
- 4. Definitions • Compliance: The distensibilityof a system. The higher the compliance, the easier it is to inflate the lungs. • Resistance: Impediment to airflow.
- 5. Definitions SIMV Patient breathes spontaneously betweenventilator breaths. • Allows patient-ventilator synchrony • Making for a more comfortable experience.
- 6. Definitions • PIP: maximumpressure measured by the ventilator during inspiration. • PEEP: pressure present in the airways at the end of expiration. • CPAP: amount of pressure applied to the airway during all phases of the respiratory cycle.
- 7. Definitions • PS: amountof pressure applied to the airway during spontaneous inspiration by the patient. • I-time: amount of time delegated to inspiration.
- 8. Types of Ventilation •Volume Control • Pressure Control • Pressure Support-CPAP • Pressure-Regulated Volume Control
- 9. Volume Control • Thepatient is given a specific volume of air during inspiration. • The ventilator uses a set flow for a set period of time to deliver the volume: • TV (cc) = Flow (cc/sec) x i-time (sec)
- 10. Volume Control • ThePIP observed is a product of : • lung compliance, airway resistance and flow rate. • The ventilator does not react to the PIP unless the alarm limits are violated.
- 11. Volume Control • ThePIP tends to be higher than during pressure control ventilation to deliver the same volume of air.
- 12. Volume Control • WithSIMV, the patient can breath spontaneously between vent breaths. • This mode is often combined with PS.
- 13.
- 14. Pressure Control • Patientreceives a breath at a fixed airway pressure. • The ventilator adjusts the flow to maintain the pressure. • Flow decreases throughout the inspiratory cycle.
- 15. Pressure Control • Thepressure is constant throughout inspiration. • Volume delivered depends upon the inspiratory pressure, I-time, pulmonary compliance and airway resistance.
- 16. Pressure Control • Thedelivered volume can vary from breath-to-breath depending upon the above factors. MV not assured. • Good mode to use if patient has large air leak, because the ventilator will increase the flow to compensate it.
- 17.
- 18. Changes in ARDS VolumeControl Pressure Control ARDS ARDS
- 19. CPAP-Pressure Support •No mandatorybreaths • Patient sets the rate, I-time, and respiratory effort. • CPAP performs the same function as PEEP, except that it is constant throughout the inspiratory and expiratory cycle.
- 20. CPAP-Pressure Support • PressureSupport (PS) helps to overcome airway resistance and inadequate pulmonary effort and is added on top of the CPAP during inspiration.
- 21. CPAP-Pressure Support • Theventilator increases the flowduring inspiration to reach the target pressure and make it easier for the patient to take a breath.
- 22.
- 23. Pressure-Regulated Volume Control • Inthis mode, a target minute ventilation is set. • The ventilator will adjust the flow to deliver the volume without exceeding a target inspiratory pressure. •Decelerating flow pattern.
- 24. Pressure-Regulated Volume Control • Nochange in minute ventilation if pulmonary conditions change. • Can ventilate at a lower PIP than in regular volume control.
- 25. Pressure-Regulated Volume Control •Hard touse on a spontaneously breathing patient or one with a large air leak. •Not a “weaning” mode.
- 26. Initial Ventilator Settings •Rate: •20-24for infants and preschoolers •16-20 for grade school kids •12-16 for adolescents
- 27. Initial Ventilator Settings •TV: 10-15ml/kg • PEEP: 3-5cm H2O • FiO2: 100% • I-time: 0.7 sec for higher rates, 1sec for lower rates
- 28. Initial Ventilator Settings •PIP(for pressure control) about 24cm H2O •Pressure Support 5-10cm H2O
- 29. Adjusting The Ventilator •pCO2 too high • pCO2 too low • pO2 too high pO2 too low PIP too high
- 30. pCO2 Too High •Patient’s minute ventilation is too low. • Increase rate or TV or both. • If using PC ventilation, increase PIP. • If PIP too high, increase the rate instead.
- 31. pCO2 Too High •If air-trapping is occurring, decrease the rate and the I-time and increase the TV to allow complete exhalation. • Sometimes, you have to live with the high pCO2, so use THAM or bicarbonate to increase the pH to >7.20.
- 32. pCO2 Too Low •Minute ventilation is too high. • Lower either the rate or TV. • Don’t need to lower the TV if the PIP is <20. • PIP <24 is fine unless delivered TV is still >15ml/kg.
- 33. pCO2 Too Low •TV needs to be 8ml/kg or higher to prevent progressive atelectasis • If patient is spontaneously breathing, consider lowering the pressure support if spontaneous TV >7ml/kg.
- 34. pO2 Too High •Decrease the FiO2. • When FiO2 is less than 40%, decrease the PEEP to 3-5 cm H2O. • Wean the PEEP no faster than about 1 every 8-12 hours.
- 35. pO2 Too High •While patient is on ventilator, don’t wean FiO2 to <25% to give the patient a margin of safety in case the ventilator quits.
- 36. pO2 Too Low •Increase either the FiO2 or the mean airway pressure (MAP). • Try to avoid FiO2 >70%. • Increasing the PEEP is the most efficient way of increasing the MAP in the PICU. • Can also increase the I-time to increase the MAP (PC).
- 37. pO2 Too Low •Can increase the PIP in Pressure Control to increase the MAP, but this generally doesn’t add much at rates <30 bpm.
- 38. pO2 Too Low •May need to increase the PEEP to over 10, but try to stay <15 if possible.
- 39. PIP Too High •Decrease the PIP (PC) or the TV (VC). • Increase the I-time (VC). • Change to another mode of ventilation. Generally, pressure control achieves the same TV at a lower PIP than volume control.
- 40. PIP Too High •If the high PIP is due to high airway resistance, generally the lung is protected from barotrauma unless air- trapping occurs.
- 41. Weaning Priorities • WeanPIP to <35cm H2O • Wean FiO2 to <60% • Wean I-time to <50% • Wean PEEP to <8cm H2O • Wean FiO2 to <40%
- 42. Weaning Priorities • WeanPEEP, PIP, I-time, and rate towards extubation settings. •Can consider changing to volume control ventilation when PIP <35cm H2O.
- 43.
- 44. Complications • Cardiac –Myocardial ischemia – Reducedcardiac output • Gastrointestinal –Ileus –Hemorrhage –Pneumoperiteneum
- 45.
- 46. Acute Deterioration • DIFFERENTIALDIAGNOSES Pneumothorax Right mainstem intubation Pneumonia Pulmonary edema
- 47. Acute Deterioration • DIFFERENTIALDIAGNOSES Loss of airway Airway occlusion Ventilator malfunction Mucus plugging Air leak
- 48. Physical Exam • Trachealshift –Pneumothorax • Wheezing –Bronchospasm –Mucus plugging –Pulmonary edema –Pulmonary thromboembolism
- 49. Physical Exam • Asymmetricbreath sounds –Pneumothorax –Mainstem intubation –Mucus plugging with atelectasis
- 50. Physical Exam • Decreasedbreath sounds bilaterally –Tube occlusion –Ventilator malfunction –Loss of airway
- 51. Pressure Patterns • Elevatedpeak and plateau pressures –Pneumonia –Pulmonary edema –Pneumothorax –Atelectasis –Right mainstem intubation
- 52. Pressure Patterns • Elevatedpeak pressure, normal plateau pressure: –Airflow obstruction –Mucus plugging –Partial tube occlusion
- 53. Pressure Patterns • Reducedpeak and plateau pressure : –Cuff leak –Ventilator malfunction –Large bronchopleural fistula
- 54.
- 55. Neurologic • Protect hisairway, e.g, have cough, gag, and swallow reflexes. • low Level of sedation • No apnea on the ventilator.
- 56. Neurologic • Must bestrong enough to generate a spontaneous TV of 5-7ml/kg on 5-10 cm H2O PS • or have a negative inspiratory force (NIF) of 25cm H2O or higher. • Being able to follow commands is preferred.
- 57. Cardiovascular • Patient mustbe able to increase cardiac output to meet demands of work of breathing. • Adequate cardiac output without being on significant inotropic support. • Hemodynamically stable.
- 58. Pulmonary • Patient shouldhave a patent airway. • If no air leak, consider decadron and racemic epinephrine. • Pulmonary compliance and resistance should be near normal.
- 59. Pulmonary • Patient shouldhave normal blood gas and work-of-breathing on the following settings: –FiO2 <40% –PEEP 3-5cm H2O –PS 5-8cm H2O –Spontaneous TV of 5-7ml/kg –Adequate RR
- 60. Global Critical Care https://www.facebook.com/groups/1451610115129555/#!/groups/145161011512 9555/ Wellcomein our new group ..... Dr.SAMIR EL ANSARY
- 61. GOOD LUCK SAMIR ELANSARY ICU PROFESSOR AIN SHAMS CAIRO [email protected]