VENTILATOR BASICS.pdf
- 1. Dr Siddhartha Sharma Dr Siddhartha Sharma Associate Professor, Department of Anaesthesia, SMS Medical College, Jaipur 1
- 2. Mechanical Ventilation is ventilation of the lungs by artificial means usually by a ventilator. ventilator. A ventilator delivers gas to the lungs with either negative or positive pressure. 2
- 3. Negative pressure ventilation Iron lung Chest cuirase Chest cuirase Positive pressure ventilation Invasive Non invasive 3
- 4. 1. Relieve respiratory distress 2. Decrease work of breathing 3. Improve pulmonary gas exchange 3. Improve pulmonary gas exchange 4. Reverse respiratory muscle fatigue 5. Permit lung healing 4
- 5. Pressure Volume Flow Time 5
- 6. Control -the mechanical breath goal, ie, a set pressure or a set volume Trigger -Variable which starts inspiration Trigger Limit - the maximum permitted value during inspiration. Cycle - Variable which ends inspiration 6
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- 8. Breath types • Mandatory breath Ventilator does the work Ventilator controls start and end of inspiration • Assist control breath patient triggers the breath Venti. Delivers the breath as per control variable 8 Venti. Delivers the breath as per control variable • Spontaneously Supported breath Pt. triggers the breath Ventilator delivers pressure support • Spontaneous Patient takes on work Patient controls start and stop
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- 10. Scalars are waveform representation of pressure,flow,or volume on y axis vrs time on x axis.10
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- 12. Indications for ventilator support present Non-invasive v/s Invasive ventilation Pressure v/s Volume ventilation Extent (Partial v/s Full) & mode of ventilation Extent (Partial v/s Full) & mode of ventilation Key Ventilatory settings Appropriate Alarms and Back-up values Weaning 12
- 13. Patient not breathing Patient breathing, …….but not enough Patient breathing enough, …….but hypoxemic / hypercapneic Patient breathing with normal gas Patient breathing with normal gas exchange, ….but working hard Airway protection 13
- 14. Clinical deterioration Hypoxia : pO2<60mm Hg Hypercarbia : pCO2 > 50mm Hg Hypercarbia : pCO2 > 50mm Hg Tachypnea : RR >35 Tidal volume <3-5 ml/kg Max. inspiratory pressure <-20 cm H2O 14
- 15. Non Non- - invasive invasive ventilation ventilation ventilation ventilation CPAP / CPAP /BiPAP BiPAP 15
- 16. Patient continuously receives a set air pressure, during both inspiration and expiration. Patient has full control over Patient has full control over respiratory rate, inspiratory time , and depth of inspiration. 16
- 17. This provides a set inspiratory pressure and a different set of expiratory pressure Initial setting: EPAP:5cm H2O IPAP: 8cm H2O O2 @ 2-5 L/min Final IPAP pressures of 15 to 22 cm H2O are common 17
- 18. Patient has full control over the respiratory rate, inspiratory time and depth of inspiration IPAP & EPAP can be increased by IPAP & EPAP can be increased by increments of 2 BiPAP = CPAP + Pressure support during inspiration 18
- 19. 1.Cardiogenic pulmonary edema , exacerbation of COPD , Post-op respiratory failure. 2.Neuromuscular disease with respiratory muscle weakness, OSA. muscle weakness, OSA. 3.Terminally ill patients & Immuno compromised patients. 4 Weaning mode. 19
- 20. Advantages: 1 Complications of intubation –avoided 2 Allows speech ,feeding Disadvantages: 1.Patient should be alert with normal 1.Patient should be alert with normal respiratory drive and intact upper airway 2 Cannot protect airway and does not provide full 100% ventillatory support 4 Claustrofobia & uncomfortable for patients 20
- 21. Improvement in: 1. Respiratory rate and heart rate 2. Dyspnea 2. Dyspnea 3. Oxygen requirement 4. Hypercarbia 21
- 22. Provides all the energy for Alveolar Ventilation Every breath is fully supported by the ventilator In classic control modes, patients are unable to breathe except at the controlled set rate In newer control modes, machines may act in In newer control modes, machines may act in assist-control, with a minimum set rate and all triggered breaths above that rate are also fully supported. Ensures that patient is not required to do any Work .Of.Breathing 22
- 23. When to Consider: Spontaneously breathing patient. Comfortably provide a portion of their required minute volume required minute volume Useful for weaning patients from MV support When not to consider: Should be avoided in case of patients with ventilatory muscle fatigue 23
- 24. PRESSURE VOLUME Tidal Volume Variable Constant Peak Ins Pressure Constant Variable Dys-synchrony Less More likely Barotrauma Less More likely Flow Pattern Decreasing Preset 24
- 25. Balance CO2 removal v/s lung protection If CO2 clearance more important than lung protection, use VOLUME If lung protection is more important than CO If lung protection is more important than CO2 removal use PRESSURE If patient triggered ventilation, synchrony may be enhanced with PRESSURE 25
- 26. The ventilator delivers a preset TV at a specific R/R and inspiratory flow rate. It is irrespective of patients’ respiratory efforts. In between the ventilator delivered breaths the inspiratory valve is closed so patient doesn’t take additional breaths. PIP developed depends on lung compliance and respiratory passage resistance. 26
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- 28. Ventilator gives pressure limited, time cycled breaths thus preset inspiratory pressure is maintained. Decelerating flow pattern. Decelerating flow pattern. Peak airway/alveolar pressure is controlled but TV, minute volume & alveolar volume depends on lung compliance, airway resistance, R/R & I:E ratio. 28
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- 30. Ventilator assists patient’s initiated breath, but if not triggered, it will deliver preset TV at a preset respiratory rate (control). Mandatory mechanical breaths may be either Mandatory mechanical breaths may be either patient triggered (assist) or time triggered (control) If R/R > preset rate, ventilator will assist, otherwise it will control the ventilation. 30
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- 32. Ventilator delivers either assisted breaths at the beginning of a spontaneous breath or time triggered mandatory breaths. Synchronization window- time interval just prior to time triggering. prior to time triggering. Breath stacking is avoided as mandatory breaths are synchronized with spontaneous breaths. In between mandatory breaths patient is allowed to take spontaneous breath at any TV. 32
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- 34. Patient is spontaneously breathing The vent augments the patient’s respiratory effort with a “pressure support” Tidal Volume is determined by patient’s effort and respiratory system compliance Can set a FiO2 PEEP and PS above PEEP Can set a FiO2 PEEP and PS above PEEP ◦ Can not set respiratory rate except back-up apnea rate. 34
- 35. FiO2 Tidal Volume /Pressure Respiratory Rate PEEP PEEP Flow Rate I:E Ratio Trigger 35
- 36. Start with FiO2 =1.0 and titrate to SpO2 >=94% ABG after 20-30min Goal –PaO2 between 60 –100 mmHg If FiO2 requirement is>0.5 , increase PEEP FiO2 =1.0, before & after suction, during bronchoscopy, & any other risky procedure 36
- 37. The tidal volume is the amount of air delivered with each breath. Initial tidal volumes should be 8-10ml/kg, depending on patient’s body habitus. If patient is in ARDS consider tidal volumes between 4 – 6 If patient is in ARDS consider tidal volumes between 4 – 6 ml/kg with increase in PEEP In Pressure-Targeted modes you’ll set the Pressure High (PH) according to the delivered tidal volume 37
- 38. Males: IBW = 50 kg + 2.3 kg for each inch over 5 feet. Females: IBW = 45.5 kg + 2.3 kg Females: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet. 38
- 39. An optimal method for setting the respiratory rate has not been established. 12 - 15/Min – Adult 20+_ 3 - Child 20+_ 3 - Child 30- 40 - New born On some machines you set the Inspiratory Time (Ti) and Expiratory Time (Te) 39
- 40. Increase RR – Hypoxia Hypercapnoea / Resp. Acidosis Sepsis, ARDS, metabolic acidosis Sepsis, ARDS, metabolic acidosis Decrease RR- Hypocapnoea Resp. Alkalosis Asthma / COPD 40
- 41. • Minute Ventilation (L/min) = RR (b/min) x Tidal Volume (liters) • If you decrease one or both the MV will • If you decrease one or both the MV will decrease resulting inHypercapnia • Tolerated in status asthmaticus and ARDS/ALI – Called “permissive hypercapnea” 41
- 42. A typical initial PEEP applied is 5 cmH2O. Adjust up by increments of 2 for marked hypoxia However, up to 20 cm H2O used in ARDS However, up to 20 cm H2O used in ARDS PEEP increases intra thoracic pressure and can thus decrease venous return and thus Blood Pressure 42
- 43. Improves oxygenation Recruits Lung in ARDS Prevents collapse of alveoli Diminishes the work of breathing 43
- 44. Peak flow rates of 60 L per minute Higher rates are frequently necessary in Asthma or those with air hunger An insufficient peak flow rate is characterized by dysnoea, spuriously low characterized by dysnoea, spuriously low peak inspiratory pressures, and scalloping of the inspiratory pressure tracing Pressure-Targeted modes allow patient to dictate the flow rate that they want 44
- 45. During spontaneous breathing, the normal I:E ratio is 1:2. If exhalation time is too short “breath stacking” occurs resulting in an increase in end-expiratory pressure also called auto-PEEP. Asthma/COPD 1:3, 1:4, … Severe hypoxia ARDS 1:1, 2:1, 45
- 46. Most frequently used to obtain an estimate of Plateau pressure and static compliance Patient should not be actively breathing When used with each breath, improves distribution of air, V/Q ratio. 46
- 47. Pressure triggering -1to -2cm H2O Ventilator-delivered breath is initiated if the demand valve senses a negative airway pressure deflection greater than the trigger sensitivity. Flow triggering Flow triggering 1 to 3 L/ min (preferred) Continuous flow of gas through the ventilator circuit is monitored. A ventilator delivered breath is initiated when the return flow is less than the delivered flow 47
- 48. •different medications for sedation. • Opiates (morphine, fentanyl) Benzodiazepines (Midazolam) Opiates (morphine, fentanyl) Benzodiazepines (Midazolam) • Propofol • Less is sometime more 48
- 49. • Paralysis without sedation = Torture Atracurium,Vecuronium can be used Atracurium,Vecuronium can be used • All one needs in this situation is chemical weakening… 49
- 50. • Low pressure, • High pressure limit and alarm • Volume alarm(low TV, high and low minute ventilation) • High respiratory rate alarm • Apnea alarm and apnea values • High/low temperature alarm • I:E ratio limit and alarm 50
- 51. Complications of positive pressure ventilation Increase in positive airway pressure High intrathorasic pressure this pressure transmitted to airway,alveoli,as well as mediastinum and great vessels Compression of great vessels Decreased venous return Decreased strock volume and cardiac output Decreased oxygen delivery Hypotension Decreased renal blood flow decreased GFR decreased urine output 29 51
- 52. Weaning The process of withdrawing mechanical ventilatory support and transferring the work of breathing from the ventilator to patient. 52
- 53. Improvement of the cause of respiratory failure Absence of major system dysfunction Appropriate level of oxygenation Appropriate level of oxygenation Adequate ventilatory status Intact airway protective mechanism (needed for extubation) 53
- 54. Rapid Shallow Breathing Index • Failure of weaning may be related to the development of a spontaneous breathing pattern that is rapid (high frequency) and shallow (low tidal volume). • The rapid shallow breathing index (RSBI) or f/VT • The rapid shallow breathing index (RSBI) or f/VT index has been used to evaluate the effectively of the spontaneous breathing pattern. • Favourable RSBI is < 105 54
- 55. No one or method of weaning has been definitely found to be superior; Spontaneous Breathing Trial Pressure Support Ventilation Other Modes of Partial Ventilatory Support Other Modes of Partial Ventilatory Support SIMV Volume support (VS) and volume-assured pressure support (VAPS) Mandatory minute ventilation (MMV) Airway pressure-release ventilation (APRV) 55
- 56. PROCEDU RE Steps PSV 1. PSV may be used in conjunction with spontaneous breathing or SIMV mode; 2. Start PSV at a level of 5 to 15 cm H2O (up to 40 cm H2O) to augment spontaneous VT until a desired VT (10 to 15 mL/kg) or spontaneous frequency (<25/min) is reached; 3. Decrease pressure support (PS) level by 3 to 6 cm H2O intervals until a level of close to 5 cm H2O is reached; until a level of close to 5 cm H2O is reached; 4. If patient tolerates step (3), consider extubation when blood gases and vital signs are satisfactory. 56
- 57. What after weaning • Oxygen therapy • Close monitoring: ABGs evaluation, Pulse oximetry • Bronchodilator therapy • Bronchodilator therapy • Chest physiotherapy • Adequate nutrition, hydration, and humidification • Incentive spirometry 57
- 59. • The ETT must be repositioned and re-secured at least once a shift to prevent tissue breakdown • Mouth care needs to be performed routinely • Cuff pressure needs to be assessed once a shift • Sometimes a higher pressure is needed to seal (ETT is Management of the tube • Sometimes a higher pressure is needed to seal (ETT is too small, anatomical differences) • Check for proper inflation, determine the location of the leak, assess the integrity of the pilot line • Suctioning 59
- 60. • Every ventilator check must include assessing the circuit integrity • PIP and Vt measurements are lower than previous measurements Evaluating for Leaks measurements • Start at the patient connection and work back to the ventilator • May need to disconnect the patient and provide manual ventilation while testing the circuit 60
- 61. Check plateau pressures by allowing an inspiratory pause (this gives you the pressure in the lung itself without the addition of resistance) If peak pressures are high and plateau If peak pressures are high and plateau pressures are low then you have an obstruction If both peak pressures and plateau pressures are high then you have a lung compliance issue 61
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- 63. High peak pressure differential: High Peak Pressures Low Plateau Pressures High Peak Pressures High Plateau Pressures Low Plateau Pressures High Plateau Pressures Mucus Plug ARDS Bronchospasm Pulmonary Edema ET tube blockage Pneumothorax Biting ET tube migration to a single bronchus Effusion 63
- 64. Increase in patient agitation and dis- synchrony on the ventilator: ◦ Could be secondary to overall discomfort Increase sedation ◦ Could be secondary to feelings of air hunger ◦ Could be secondary to feelings of air hunger Options include increasing tidal volume, increasing flow rate, adjusting I:E ratio, increasing sedation 64
- 65. • Early use of NPPV • Prepare and expect hypotension during intubation – IVF bolus • Mechanical Ventilation Strategy – Permissive Hypercapnia • Mechanical Ventilation Strategy – Permissive Hypercapnia • Ventilator maneuvers that prolong I:E – Low tidal volumes, low respiratory rates, square wave forms, high flow rates. 65
- 66. • Tidal Volumes: 6-7 ml/kg (IBW) • Respiratory Rate: 8-10 bpm • Flow Rate: 80-100 L/min • Square Wave forms • SEDATION: propofol,fentanyl • Square Wave forms • SEDATION: propofol,fentanyl • Last resort: chemical weakening • Expect high peak pressures 66
- 67. Lung Protective Strategy Low-Tidal Volumes Start at 6 mL/kg IBW Goal of 4-6 mL/kg IBW Low Plateau Pressures – Less than 30 Low Plateau Pressures – Less than 30 High PEEP Permissive hypercapnia 67
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