Basic ventilator management

These slides represent how to manage patients on a mechanical ventilator? Easy understanding of using ventilators. indication of mechanical ventilator use. How to wean a patient from a mechanical ventilator? How to fine-tune the ventilator settings?

1. Basic Ventilator Management Charipersion : Assoc Prof Dr Md Mukhlesur Rahman By Dr Md Mashiul Alam Phase B resident

2. Mechanical Ventilation: Short History Negative pressure ventilation: The  iron lung, also known as the Drinker and Shaw tank, was developed in 1929 Large scale use in 1940 during  polio  epidemic

3. Positive pressure ventilation: by the military during World War II to supply oxygen to fighter pilots in high altitude In 1950 again during polio epidemic

4. Types of mechanical Ventilation Negative pressure ventilation Positive pressure ventilation - Noninvasive (NPPV) - Invasive (IPPV)

5. IPPV vs NIPPV NPPV is the provision of any form of ventilatory support applied without the use of an endotracheal tube. With either a nasal or oral face mask. Patients can speak, eat and less chance of pneumonia Indication: 1. Acute exacerbation of COPD if the patient is alert and no indication of ETT

6. 2. Patient with hypoxemic respiratory failure but hemodynamically stable and can protect his or her airway. 3. After extubation to avoid reintubation 4. Patient with acute pulmonary edema in the absence of MI to redistribute fluid from alveolar space to vessel. 5. Obstructive sleep apnea

7. Exclusion criteria for NPPV: Patient is not breathing spontaneously Hemodynamically instable Un co-operative patient Facial burns or other trauma Copious secretion High risk of aspiration

8. Invasive PPV Indication: Primary indication- impending or existing respiratory failure despite maximal treatment General anesthesia Cardiogenic shock to decrease work of breathing Increased ICP

9. General parameters to consider MV: Respiratory rate > 30/min or less than 8 bpm Vital capacity <1-1.5 L/min PaO 2 <60 mmHg on FIO 2 > 0.5 PaCO 2 high with repiratory acidosis (pH<7.2) Exhaustion Confusion Severe shock Severe LVF Raised ICP

10. Basic Ventilator Settings

11. FIO2: Fraction of inspired oxygen concentration Initially it should be 0.7 to 1 to ensure adequate tissue oxygenation. After an initial ABGA obtained FiO2 may be decreased to 0.5 or less while achieving PO2 more than 60 mmHg to prevent oxygen toxicity

12. VT: Tidal Volume A starting point for VT is 8 to 10 ml/Kg ideal body weight. An acceptable VT is one that results in a plateau pressure of 30 mmHg A VT of 12 ml/Kg or more is not usually needed EVT: Exhaled Tidal Volume Regardless of mode of ventilation the most accurate measure of the volume received by the patient is the exhaled tidal volume. The volume actually received by the patient must be confirmed by monitoring EVT on the display panel of the ventilator

13. RR: Respiratory Rate Near physiological as possible: 10 to 20 bpm . Typical initial rate settings are between 8 and 12 breaths/min . Slow rate may be useful in patients with obstructive pulmonary disease because as the rate is decreased more time is available for exhalation Fast rates may be useful in patients with noncomplaint lungs to prevent barotrauma with small VT RR x VT = minute ventilation (mV) When patient has adequate respiratory drive no RR set on the ventilator

14. Flow Rate: The speed with which the VT is delivered. Average: 40-60L /min High flow rate – Decreased inspiratory time Increased peak inspiratory pressure (PIP) Low flow rate – Increased inspiratory time Decreased PIP

15. Pressure modes Volume mode Spontaneous

16. I:E ( Inspiratory to expiratory ratio) The duration of inspiration in comparison with expiration. Inspiratory time of 1 sec is a good initial setting. Generally I:E ratio is set at 1:2 1:3 or 1:4 or longer may be necessary to ventilate the lungs in COPD I:E ratio is a function of flow rate, inspiratory time and RR

17. Inversed I:E ratio: 1:1 or 2:1 or 3:1 are called inverse I:E ratio Employed when conventional strategies to improve oxygenation fail But it may increase mean airway pressure ( mPaw ) and lead to hemondynamic compromise

18. PEEP (Positive End Expiratory Pressure) A constant positive pressure in the airways at the end of expiration to prevent alveolar collapse. Range 5 to 10 cmH2O 5 to 10 cmH2O in LVF, 10 to 20 cmH2O in ARDS It prevents atelectasis , improve oxygenation, redistribute lung water from alveoli to perivascular space

19. Initial ventilator settings: Guidelines Parameter Initial settings FiO2 0.7 – 1.0 Tidal Volume 8-12 ml/Kg, 4-6 ml/Kg is ARDS RR 10-20 Flow rate 40-60 L /min Inspiratory time 1 sec (.8 to 2 sec) I:E ratio 1:2 to 1:3 Sensitivity Pressure trigger : -0.5 to -1.5 below baseline. Flow trigger: 1 – 3 L/min PEEP 3 -5 cmH20

20. Correcting oxygenation and ventilator problems Problem ABG findings Adjustments Excessive oxygenation PaO2 >100 SaO2 100% Decrease FiO2 Keep I:E to 1:2 Decreased PEEP Inadequate oxygenation PaO2 <60 SaO2 <90% Increase FiO2 Increase PEEP Prolong inspiratory time to increase mPaw Respiratory acidosis PaCO2 >45 pH≤ 7.35 Increase VT with PIP ≤ 40 mmHg Increase RR Respiratory alkalosis PaCO2 <35 pH ≥ 7.45 Decrease VT Decrease RR

21. Modes of mechanical ventilation Breath types Machine cycled: Mandatory – Ventilator perform all of the work of breathing Assisted- breath is triggered by the patient and then rest are taken over by the machine

22. Patient cycled: Supported breath – Triggered by patient and cycled by patient. Ventilator helps a little. Spontaneous breath – Patient performs all the work of breathing

23. Ventilatory support Full ventilatory support (FVS): CMV or A/CMV Apnea Paralysed Severe flail chest Depressed neurological state

24. Partial Ventilatory Support (PVS): It allows the patient to respond to increase in CO2 and promotes use of respiratory muscle thereby preventing disuse atrophy SIMV, PSV, CPAP

25. Control Modes Volume Control Pressure Control Dual control

26. Flow volume curve for Spontaneous ventilation expiration Inpiration

27. Volume control ventilation A delivered breath is volume controlled when volume is constant for every breath. The pressure wave form varies because is pressure is variable. Types: CMV A/CMV SIMV

28. CMV (continuous mandatory vent.) Patient receives a preset number of breaths per minute of a preset tidal volume (VT) and patient’s effort does not trigger a mechanical breath

29. Indication: No respiratory effort Anesthesia Backup to assisted ventilation

30. V A/CMV Asisst / Control Mandatory vent. The ventilator delivers a preset number of breaths of a preset VT and patient may trigger spontaneous breath

31. Machine triggered Patient triggered

32. Indication: Normal respiratory drive but patient is too weak or unable to perform work of breathing (WOB) To allow patient to set their own rate

33. V SIMV Synchronized Intermittent Mandatory Vent. Patient receives a set number of breaths of a set VT but patient may initiate spontaneous breaths un assisted by the ventilator. Patients effort is assisted if it falls in mandatory breathing window

34. Mandatory breathing window

35. Indication: Normal respiratory drive by unable to perform all WOB Allowing patients to set their own RR and assist in maintaining a normal PaCO2 Weaning from mechanical ventilation

36. Pressure control ventilation A delivered breath is pressure controlled when pressure is constant for every breath. Here the pressure wave form has a specific pattern for every breath while volume waveform varies. Types: PC or P A/C PSV / P SIMV CPAP

37. P- A/CMV A mode of ventilation in which every breath is augmented by a preset amount of inspiratory pressure and there is no set VT. It may sense patients spontaneous breathing effort and assist with preset pressure. Indication: Providing full ventilatory support (FVS) in patients with non compliant lungs who exhibit high Paw and poor oxygenation in volume control mode.

38. Advantage over volume control mode Peak Inspiratory pressure (PIP) may be reduced in – reducing chance of barotrauma . Mean airway pressure ( mPaw ) is increased which improves oxygenation Limits excessive airway pressure as pressure is set by the clinician Lower WOB Better gas distribuation

39. P-SIMV/ PSV The patients spontaneous respiratory activity is augmented by the delivery of a preset amount of inspiratory positive pressure. It may used alone or in combination of SIMV. In P SIMV only the spontaneous breaths are pressure supported

40. P SIMV

41. Indication Weaning from mechanical ventilation. PSV is used for spontaneous breathing trial Non invasive ventilation

42. Trouble shooting patient-ventilator system Objective: To evaluate the patient’s response to the current level of ventilatory support To determine accuracy and appropriateness of the current ventilatory settings To ensure the presence and proper functioning of the necessary equipment

43. Monitoring Patients Patient should be assessed at least every 2 hours and with any setting change Medical history, current diagnosis and clinical course should be known Key components: 1. VITAL signs and hemodynamics 2. Physical examination – patient comfort, WOB, accessory muscle use, symmetry of chest wall movement. Chest wall examinaiton . Pulse. Airway leak. Swallow reflex. Abdominal distension. Nutritional status. 3. Laboratory and Xray findings 4. Behaviors and complaints

44. Monitoring the ventilator Key components: Usually every 2 hours Setting: Monitor information found on front panel Patient data: Monitor the information found on the display panel Alarms: Ensure all the alarms are activated and appropriate alarm limits are set

45. Weaning procedure When patient is on ventilator for more than 3 days weaning procedure become for complex If the condition requiring ventilation is fully corrected and the patient is alert and breathing spontaneously – extubation is planned

46. Weaning trial screen should be done daily Hemaodynamically stable ( no arrythmia , HR ≤ 120 bpm , absence of vasopressores except low dose dopamine and dobutamine FiO2 ≤ 0.5 PEEP ≤ 8 Patient is on MV less than 3 days

47. Wean Trial Protocol CPAP – one hour trial daily If no sign of intolerance proceed to extubation if sign of intolerance – full resting mode until next trial and at night 2. PSV – Max PSV level than decrease 5 cm H20 for 4 hours ---if no intolerance another 5 cm H20 decrease for another 4 hours. If intolerance defer trial for the next day with FVS in between.

48. Sign of intolerance ( any one 3-5 mins sustained) RR ≥ 35 breaths/ min SpO2 ≤ 90% or decrease by 4 % HR ≥ 140 bpm SBP ≥ 180 or ≤ 90 Excessive anxiety or agitation Diaphoresis

49. Complications of mechanical ventilation Problems related to positive pressure Ventilator induced lung injury – Barotrauma , Oxygen toxicity Reduction in cardiac output and oxygen delivery Alteration in renal function and positive fluid balance Impaired hepatic function Increased ICP V/Q mismatch

50. Problems related to the artificial airway Infection (Ventilator associated pneumonia) Gastric distress Abdominal distention Ulcers and gastritis Patient’s anxiety and stress

51. Take Home message Put any acutely distressed patients on V A/CMV at first and Sedate the patient if needed Send ABG not less 20 mins of a change Adjust the ventilator according to ABG report, SpO2 Start weaning trial when the precipitating condition resolved ( Use SIMV, PSV modes)

52. “After all there is no match for natural ventilators…..” THANK YOU