Basics & principles of mechanical ventilation

1. Basics & principles of mechanical ventilation g.k.kumar

2. Basics & principles of ventilation -What is ventilator -How ventilators work -How to use ?

3. Ventilator: • The Machine delivers O2 & removes Co2 with out harming the patient. • The Ventilator should have capacity of delivering a consistent tidal volume under all adverse conditions of lung disease.

4. Mechanical Ventilation: • The process / method by applying (intermittent) positive airway pressure & supplementation of Inspired O2 to achieve desirable oxygenation.

5. GOALSof Mechanical Ventilation: • Good ventilation (known by pa Co2) • Oxygenation (by pa O2). • Alveolar recruitment by peep • Lowest O2 supplement. • Synchrony between patient & Ventilation. & Safe  No Negative hemodynamic effect No Barotraumas No auto PEEP

6. Classification of Mechanical ventilation: • Positive / Negative pressure ventilation. • Partial / full ventilation. • Invasive / Non invasive ventilation.

7. Components of ventilator • Power source-electrical/pneumatic/both • Control systems-circuits, control panel • Display systems

8. V Central unit oxy blender Exp.limb Pt Insp. limb V T P Fio2 Hum&neb compressor

9. PHASES & VARIABLES • INITIATION OF INSPIRATION-TRIGGER • INSPIRATION-LIMIT • MAINTENANCE OF INSPIRATION-CONTROL • CHANGING TO EXPIRATION-CYCLE

10. Triggering variable: • Triggering is a method of starting the inspiration • Types: Pressure Triggering Flow Triggering - No lag time Time Triggering -Less effort

11. Control Variable: • Setting that maintained thro ‘out inspiration • Type : Volume control. Pressure control.

12. PCV VCV • Vt. Variable set • PIP SET & lesser variable & more • Plateau pressure Set Variable • Inspiratory flow decelerating type fixed flow type sinusoidal/square • Inspiratory time set set • Respiratory rate Set Set • Barotrauma Less More Leak compensation +for minor leak nil Patients acceptance good -

13. Limit Variable: • Setting that can't be exceeded during inspiration • Type : Pressure limit- [psv] volume limit Flow limit

14. Cycle variable: • Method of termination of inspiration, I.e. changing over from inspiration to expiration. • Types: Volume cycle Pressure cycle Time cycle flow cycle.

15. Compliance-resistance-volume Ccw Cl compliance PAi Vt PA range Raw C=▲V /▲P R=[PIP-Pp] / F PAe

17. Normal resistance Un intubated patient ; 0.6 - 2.4 cm H20 / L / Sec, . at 0.5L /sec Intubated patient; 6cm H20 / L / Sec

18. Ventilatory controls-inter relation MV Ti T I:E Te Vt f

19. Ventilator Modes Combination of breath type and phase variable. Conventional modes Recent modes Newer modes CMV MMV VAPS, PAug A/C MV APRV VS, PRVC IMV & SIMV BIPAP AUTOFLOW CPAP & PEEP IRV AUTOMODE VCV DLV PAV,PPS PSV HFJV ASV

20. Controlled mechanical ventilation: -CMV • All breaths are delivered by ventilator. • No Patient participation. • Set Vt. Delivered at set RR • Requires sedation & neuromuscular blockade. • Time initiated Volume limited Volume cycling

21. CMV • Indications • Patient with no efforts / complete respiratory failure. • When negative inspiratory effort contra indicated. • eg.flail chest. • During anesthesia. • Disadvantages Patient participation not allowed. • Heavy sedation relaxant – need • Long term CMV  Respiratory muscle weakness. • Varying PIP according to lung compliance & patient efforts.

22. Assist / Control Mechanical ventilation: • Patient can trigger ventilation at a rate more than set RR • All breaths are delivered at set volume , set time & set pressure • Triggering  pressure / flow (spontaneous) Time (Mandatory) Limiting  Volume Cycling  Volume • Patient can vary RR only but not vt.

23. Assist / Control Mechanical Ventilation • Indications: • Patient with normal drive but with respiratory weakness  Recovering patient. • To preserve patient efforts • Weaning. • Disadvantages • Rapid triggering  Hyperventilation Hypotension • Flow rare should be adjusted according to the need. • If RR < RR  CMV mode.

24. IMV / SIMV • The patient receives the Mandatory set Vt at set RR. • The set Mandatory breaths are synchronized with patient efforts. • Between the mandatory breaths the patient can breath spontaneously • Spontaneous breath vt depends on  Patients respiratory effort  PS • Triggering - Pressure Limiting - Volume Cycling - Time

25. IMV / SIMV Advantages: • The mandatory breaths are synchronized with patient’s Spontaneous efforts. • Hyperventilation is less • More active participation of patient Disadvantages: More WOB

26. A/CMV SIMV • Patient decides only RR < -- > patient effort decides RR &vt. • Less WOB as only < -- >more WOB as Initiation by patient patient has to . operate demand . flow system • Possibility of hyper ventilation < -- > No

27. CPAP: • A mode is which positive pressure is applied tho’ out the respiratory cycle using during spontaneous ventilation. (Pr applied in mechanical ventilation :PEEP) • No Ventilatory assistance • Positive Pressure causes: • Prevention of alveolar collapse & alveolar recruitment Î FRC & Atelecasis FlO2 requirement

28. CPAP PEEP Pr applied and base line Pr. Applied with Pr elevated when ventilatory some ventilatory Assistance is nil. Assistance present.

29. PEEP • Applied when Fio2 requirement is 50% - 60%. • Best Peep: PEEP titrated to achieve optimal respiratory system compliance. • Optimal Peep :Titration of PEEP until Qs /Qt is < 15 %

30. Volume Control Ventilation: • Vt. Delivery is constant according to pressure regardless of changes in airway resistance or respiratory system compliance. • VCV is given when constant MV is needed (eg, : patient with Î ICT)

31. Pressure control ventilation: • The pressure applied to the airways is constant regardless of airway resistance and compliance. • Constant pressure is delivered throughout inspiration at set RR • Time initiated pressure limiting time cycling. • Vt may vary according to patient lung conditions. • PCV avoids over distention in patient with ALI, because PIP can be set. • Settings • Preset pressure is equal to half of present PIP. • PEEP half of present PEEP (if > 8cm H2 O) • I: E is 1:2

32. PCV VCV • Vt. Variable set • PIP SET & lesser variable & more • Plateau pressure Set Variable • Inspiratory flow decelerating type fixed flow type sinusoidal/square • Inspiratory time set set • Respiratory rate Set Set • Barotrauma Less More Leak compensation +for minor leak nil Patients acceptance good -

33. Pressure – Support Ventilation (Psv) • Patients spontaneous activity is assisted by delivery of a preset amount of inspiratory positive pressure. • Patient triggers  set pressure is maintained throughout inspiration. • Pressure initiated. • Pressure limiting . • Flow Cycling • As flow reaches 25% of peak inspiratory flow /5 litres / min

34. Pressure – Support Ventilation (Psv) • Low PSV – to overcome the patients WOB associated with ETT and circuits. • PSV max – to achieve Vt of 10 -12 ml / Kg - may require upto 40 -50 cm H2O Can be used alone as full ventilatory support or with SIMV. • Can be used as non invasive ventilatory support up to 20cm H2O2 for – transient Ventilatory support ( Narcotic overdose, asthma, acute exacerbation of COPD).

35. Mandatory Minute Ventilation (MMV): • Preset MV is selected. • The Ventilator calculates the patients spontaneous MV. • It patients spontaneous MV < set MV, ventilator assists to achieve set MV • Ventilatory assisstance may be - Volume controlled SIMV breaths Î RR /Vt - Î PSV

36. Mandatory Minute Ventilation (MMV): • ADVANTAGES: • MV guaranteed • Useful as weaning mode • DISADVANTAGES: • RR may cause dead space ventilation even with acceptable MV. • Respiratory muscle fatigue may develop (so high RR alarm should be activated.

37. Mandatory Minute Ventilation (MMV): • INDICATIONS: • During weaning period • To aspiratory flow and WOB • To overcome ETT/circuit resistance

38. BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION(BIPAP) • A pressure controlled ventilation • Allows unrestricted spontaneous breathing at any point of ventilatory cycle • Time cycled changes of pressure application. • Independent positive airway pressure to inspiration & expiration • Inspiratory set pressure is called IAP/T high& Expiratory set pressure is called EAP/T low • Usual IAP is 8 cm H2O & EAP is 3 cm H2O • Trigger:flow, Limit:pressure; Cycle:time

39. BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION(BIPAP) • IAP causes better ventilation Paco2 • EAP causes better oxygenation Pao2 • Types • --CPAP+PS • --Two alternating CPAP level • --APRV

40. BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION(BIPAP) • ADVANTAGES: • Non invasive ventilation • Useful in—end stage COPD • ---restricted chest wall diseases • ---neuromuscular diseases • ---nocturnal hypo ventilation • A weaning mode.

41. AIRWAY PRESSURE RELEASE VENTILATION(APRV) • A CPAP circuit with release valve at expiratory limb –driven by time device • APRV is a CPAP system causing . alveolar ventilation by briefly interrupting CPAP.

42. APRV……., • Release valve opens for 1-2sec. • Pr drops to lower level-low CPAP(0to-2cmH2O) • Lung volume less than FRC in expiration • alveolar ventilation & CO2 elimination • Reapplication of CPAP by closing valve- Higher CPAP(10to 12 cm H2O) • FRC & oxygenation.

43. APRV……., • ADVANTAGES: • Lesser PIP ,so less hemo dynamic changes. • To alveolar ventilation in ALI of mild to moderate. • A weaning mode.

44. INVERSE RATIO VENTILATION(IRV) • I:E >1 • PC-IRV / VC-IRV • Ti with set pr opening of stiff alveoli units improved oxygenation • Te not allowing alveoli to collapse • development of intrinsic PEEP • reduction of shunting

45. IRV……, • Improve oxygenation by • Reducing intra pulmonary shunting • Improvement of V/Q matching • Decreased dead space ventilation • Increased MAP & intrinsic PEEP • Useful when high FiO2 & high PEEP to be avoided

46. NEWER MODES • Dual modes: VAPS, Paug, - VS, PRVC, Autoflow, VPC • Switching modes: Automode • Proportional modes: PAV,PPS. • Adaptive modes: ASV

47. DUAL MODES • Combination of 2modes of ventilation(PCV&VCV) to deliver guaranteed Vt/MV • Volume guaranteed pr targeted ventilation • Mode changes occur with in a breath-VAPS,Paug over several breaths-VS,PRVC,Auto flow,VPC

48. DUAL MODES- CHANGES WITH IN BREATH • VAPS:volume assured pr support-T bird,bird8400st • Paug :pr augmented ventilation-bear 1000 • Vt guaranteed variable pr limited modes • During inspiration,the ventilator monitors Vt • if desired Vt delivered before flow drops---PSV • if desired Vt not delivered before flow drops— • flow continued at set pr support level till adequate • Vt delivered.

49. DUAL MODES- CHANGES WITH IN BREATH • Trigger – patient patient • Limit -- pressure variable pr • Cycle -- flow volume • PSV Paug • VAPS

50. DUAL MODES- CHANGES OVER SEVERAL BREATHS • PRVC:Pr regulated VC-siemen300 • VS:volume support:servo 300 • Auto flow;DragerE4 • VS-volume assured PSV • PRVC-volume assured PCV • Vt measured over several breaths&adequate MV achieved by changing PS/PC mode for remaining breaths.