Principles of Mechanical Ventilation | Ventilator Settings & Troubleshooting

2. اصول تهویه مکانیکی تهیه کننده: میترا حکمت افشار دانشجوی ترم دوم کارشناسی ارشد مراقبت های ویژه پرستاری اردیبهشت 1389 Email: m.hekmatafshar@yahoo.com استاد راهنما: جناب آقای رحمانی

3. Principles of Mechanical Ventilation

4. Aimes • Ventilator settings • Modes of ventilation • Monitoring of the patient • Trouble shooting

5. Origins of mechanical ventilation • Negative-pressure ventilators (“iron lungs”) • Non-invasive ventilation first used in Boston Children’s Hospital in 1928 • Used extensively during polio outbreaks in 1940s – 1950s • Positive-pressure ventilators • Invasive ventilation first used at Massachusetts General Hospital in 1955 • Now the modern standard of mechanical ventilation

6. Ventilator settings

7. Ventilator settings • Ventilator mode • Respiratory rate • Tidal volume or pressure settings • Inspiratory flow • I:E ratio • PEEP • FiO2 • Inspiratory trigger

8. Respiratory rate • What is the pt actual rate demand?

9. Set as: % of respiratory cycle RR:10 I:E =1/2 Total respiratory time=60/10 TCT=6 Sec I:E ratio Expiratory time not set Remaining time after inspiration before next breath Inspiratory time

10. Tidal Volume or Pressure setting • Maximum volume/pressure to achieve good ventilation and oxygenation without producing alveolar overdistention • Max cc/kg? = 10 cc/kg • Some clinical exceptions

11. Inspiratory flow • Varies with the Vt, I:E and RR • Normally about 35-45 l/min

12. I:E Ratio • 1:2 • Prolonged at 1:3, 1:4, … • Inverse ratio

13. FIO2 • The usual goal is to use the minimum Fio2 required to have a PaO2 > 60mmhg or a sat >90% • Start at 100% • Oxygen toxicity normally with Fio2 >40%

14. InspiratoryTriger • 2 modes: • Airway pressure • Flow triggering

15. Positive End-expiratory Pressure (PEEP) • What is PEEP? • What is the goal of PEEP? • Improve oxygenation • Diminish the work of breathing ظ

16. PEEP • Barotrauma • Diminishcardiac output • Regionalhypoperfusion • NaClretention • Augmentation of I.C.P.? • Paradoxal hypoxemia

17. PEEP • Contraindication: • No absolute CI • Barotrauma • Airway trauma • Hemodynamic instability • I.C.P.? • Bronchospasm?

18. PEEP What PEEP do youwant? Usually, 5-10 cmH2O

19. Rise time (Ramp) determines speed of rise of flow (volume control mode) or pressure (pressure control and pressure regulated volume control modes) very short rise times may be more uncomfortable for the patient long rise times may result in a lower tidal volume being delivered (pressure control mode) or higher pressure being required (volume control and pressure regulated volume control modes)

20. Rise time

21. Theory • Ventilation vs. Oxygenation • Pressure Cycling vs. Volume Cycling

22. Principles (1): Ventilation The goal of ventilation is to facilitate CO2 release and maintain normal PaCO2 • Minute ventilation (MV) • Total amount of gas exhaled/min. • VE = (RR) x (TV) • VE comprised of 2 factors V/Q Matching. Zone 1 demonstrates dead-space ventilation (ventilation without perfusion). Zone 2 demonstrates normal perfusion. Zone 3 demonstrates shunting (perfusion without ventilation).

23. Principles (2): Oxygenation The primary goal of oxygenation is to maximize O2 delivery to blood (PaO2) • Alveolar-arterial O2 gradient (PAO2 – PaO2) • Oxygenation in context of ICU • V/Q mismatching • Patient position (supine) • Airway pressure, pulmonary parenchymal disease, small-airway disease • Adjustments: FiO2 and PEEP V/Q Matching. Zone 1 demonstrates dead-space ventilation (ventilation without perfusion). Zone 2 demonstrates normal perfusion. Zone 3 demonstrates shunting (perfusion without ventilation).

24. Pressure ventilation vs. volume ventilation Pressure-cycled modes deliver a fixed pressure at variable volume (neonates) Volume-cycled modes deliver a fixed volume at variable pressure (adults)

25. Pressure ventilation vs. volume ventilation • Pressure-cycled modes • Pressure Support Ventilation (PSV) • Pressure Control Ventilation (PCV) • CPAP • BiPAP • Volume-cycled modes • Control • Assist • Assist/Control • Intermittent Mandatory Ventilation (IMV) • Synchronous Intermittent Mandatory Ventilation (SIMV) Volume-cycled modes have the inherent risk of volutrauma.

26. Pressure Support Ventilation (PSV) (Assist spontaneous breathing) ASB Patient determines RR, VE, inspiratory time – a purely spontaneous mode • Parameters • Triggered by pt’s own breath • Limited by pressure • Affects inspiration only • Uses • Complement volume-cycled modes (i.e., SIMV) • PSV alone • Used alone for recovering intubated pts who are not quite ready for extubation • Augments inflation volumes during spontaneous breaths • BiPAP (CPAP plus PS) PSV is most often used together with other volume-cycled modes. PSV provides sufficient pressure to overcome the resistance of the ventilator tubing, and acts during inspiration only.

27. Pressure Control Ventilation (PCV) Ventilator determines inspiratory time – no patient participation • Parameters • Triggered by time • Limited by pressure • Affects inspiration only • Disadvantages • Requires frequent adjustments to maintain adequate VE • Pt with noncompliant lungs may require alterations in inspiratory times to achieve adequate TV

28. CPAP and BiPAP CPAP is essentially constant PEEP; BiPAP is CPAP plus PS • Parameters • CPAP – PEEP set at 5-10 cm H2O • BiPAP – CPAP with Pressure Support (5-20 cm H2O) • Shown to reduce need for intubation and mortality in COPD pts • Indications • When medical therapy fails (tachypnea, hypoxemia, respiratory acidosis) • Use in conjunction with bronchodilators, steroids, oral/parenteral steroids, antibiotics to prevent/delay intubation • Weaning protocols • Obstructive Sleep Apnea

29. Assist/Control Mode Ventilator delivers a fixed volume • Control Mode • Pt receives a set number of breaths and cannot breathe between ventilator breaths • Similar to Pressure Control • Assist Mode • Pt initiates all breaths, but ventilator cycles in at initiation to give a preset tidal volume • Pt controls rate but always receives a full machine breath • Assist/Control Mode • Assist mode unless pt’s respiratory rate falls below preset value • Ventilator then switches to control mode • Rapidly breathing pts can overventilate and induce severe respiratory alkalosis and hyperinflation (auto-PEEP)

30. IMV and SIMV • IMV • Pt receives a set number of ventilator breaths • Different from Control: pt can initiate own (spontaneous) breaths • Different from Assist: spontaneous breaths are not supported by machine with fixed TV • Ventilator always delivers breath, even if pt exhaling • SIMV • Most commonly used mode • Spontaneous breaths and mandatory breaths • If pt has respiratory drive, the mandatory breaths are synchronized with the pt’s inspiratory effort

32. FIGURE 7-10Synchronized intermittent mandatory ventilation (SIMV) with pressure support (PS) ventilation. In SIMV and PS, mandatorybreaths of a preset tidal volume are administered in the fashion of SIMV. In this figure the square waveformisapplied to the mandatorybreaths. Onlyspontaneousbreaths are pressure supported ,and not the mandatorybreaths.

33. Vent settings to improve <oxygenation> • PEEP • Increases FRC • Prevents progressive atelectasis and intrapulmonary shunting • Prevents repetitive opening/closing (injury) • Recruits collapsed alveoli and improves V/Q matching • Resolves intrapulmonary shunting • Improves compliance • Enables maintenance of adequate PaO2 at a safe FiO2 level • Disadvantages • Increases intrathoracic pressure. • May lead to ARDS. • Rupture: PTX, pulmonary edema. Oxygen delivery (DO2), not PaO2, should be used to assess optimal PEEP.

34. Vent settings to improve <ventilation> RR and TV are adjusted to maintain VE and PaCO2 • Respiratory rate • Max RR at 35 breaths/min • Efficiency of ventilation decreases with increasing RR • Decreased time for alveolar emptying • TV • Goal of 10 ml/kg • Risk of volutrauma • I:E ratio • Increasing inspiration time will increase TV, but may lead to auto-PEEP • PIP • Elevated PIP suggests need for switch from volume-cycled to pressure-cycled mode • Maintained at <45cm H2O to minimize barotrauma • Plateau pressures • Pressure measured at the end of inspiratory phase • Maintained at <30-35cm H2O to minimize barotrauma

35. CMV

36. A /CV

37. SIMV

38. PSV(pressure support ventilation) Spontaneousinspiratory efforts trigger the ventilator to provide a variable flow of gas in order to attain a presetairway pressure. Can beused in adjunctwith SIMV.

39. Monitoring of the patient

40. Airway pressure Pressure Pressure Time Time

41. Trouble Shooting • which pressure is going up • Ppeak is up • Look at your Pplat

42. Trouble Shooting • If your Pplat is high, you are faced with a COMPLIANCE problem • If your Pplat is N, you are faced with a RESISTIVE problem

43. Trouble Shooting

44. Trouble Shooting Remove pt fromventilator Initiatemanual ventilation Perform P/E and assess monitoring indices Check patency of airway

47. Conclusion • Ventilator settings • Monitoring of the patient • Trouble shooting

49. reference • Critical care nursing patricia gonce morton 2009. • Aaccn essential of critical care nursing marian chaly 2006. • The icu book marino 2007. • Critical care nursing jaya 2007. • کاربردهای فیزیولوزیکی و کلینیکی تنفس مکانیکی:دکتر شمس زاده امیری 1375. • تنفس مکانیکی در بخشهای مراقبت ویژه –دکتر مسعود صابری .1379 • مراقبت های پرستاری در بخش icu,ccu, دیالیز معصومه ذاکری 1381 • مراقبت پرستاری در ای سی یو ملاحت نیکروان-حسین شیری 1377 . • مراقبت پرستاری ویژه ICU,CCU,دیالیز-شیوا بستام پور-احمد اسدی نوقابی 1384

50. Chronic Obstructive Pulmonary Disease and Weaning of Difficult-to-wean Patients from Mechanical Ventilation: Randomized Prospective Study .Croat Med J 2007;48:51-58