Mechanical ventilation basics
- 1. MECHANICAL VENTILATION Dean Tanner (MD)- EM PGY3 Carolina Med Center Erasto Sylvanus (MD)- EM PGY2 MUHAS
- 2. Why are you intubating? • Difficulty Oxygenating • Difficulty Ventilating • Airway Protection • Tired – Metabolic demand
- 3. MODES Continuous Mechanical (mandatory) ventilation (CMV) Intermitent Mandatory Ventilation (IMV) Continuous Spontaneous Ventilation (CSV) Assist control (AC) -Volume control (VC) -Pressure control (PC) -Duo-mode: Pressure regulated volume control (PRVC) -Determine VT and RR -Best for paralyzed, deeply sedated. -Ventilator gives a breath every time the pt initiates a breath Synchronized Intermittent mandatory ventilation(SIMV) -Volume (V-SIMV) -Pressure (P-SIMV) -Set VT and RR -Best for Pt who requires airway protection I. a) Pressure support (PS) -Set pressure support level - No set RR -Best for Spontaneous breathing pts requiring minimal support. b) Volume support ventilation (VSV)- some machines II. CPAP - Set PEEP II. Bi-level positive airway pressure (BL-PAP) - Set IPAP and EPAP RISKS:Breath stacking and metabolic alkalosis (awake or agitated pts) Risk: not good for respiratory muscle weakness or LV dysfunction
- 4. 3 T’s of Mechanical Ventilation • Trigger: What triggers the ventilator to deliver a breath? – Patient, ventilator, or both – CMV (AC) mode: Volume or pressure control options. RR set by you, but will also deliver a full breath when patient initiates a breath. Can lead to breath stacking – SIMV mode: Volume or pressure control options. RR set by you, but if patient initiates a breath, vent won’t assist unless it is near next breath – Pressure support: assists with a breath initiated by patient
- 5. 3 T’s of Mechanical Ventilation • Target – (Tidal) Volume: typically 6-8 cc/kg – Inspiratory Pressure (use if unable to keep plateau pressure < 30 mmHG)
- 6. 3 T’s of Mechanical Ventilation • Termination – Volume Control: You tell the vent what volume of breath to deliver – Pressure Control: You tell the vent to deliver the breath over a certain amount of time
- 7. Tidal volume • Tidal volume = protection • Tidal volume DOES NOT equal ventilation • 6-8 mL/kg ideal body weight • Decrease if peak pressures > 30 mmHg PBW= MEN: 50+ 0.91 (Height in cm – 152.4) WOMEN: 45 + 0.91 (Height- 152.4)
- 9. Respiratory Rate • RR = Ventilation • Start at 16-18 • Adjust based on CO2 (ABG at 30 minutes)
- 10. FIO2/PEEP • Start at 100% FIO2 • ABG/VBG • Decrease FIO2 to 40%, then titrate FIO2 and PEEP together using PEEP table
- 12. Obstruction patients (asthma, COPD) • Goal is to give the patient time to expire • Tidal volume = 8 ml/kg ideal body weight • FIO2 = 100% 40%, titrate to Spo2 >90% • PEEP = 5 or 0 • Resp rate = lung protection – Start at 10 and adjust if necessary based on flow waveform and plateau pressure – Goal = I:E 1:4 or 1:5 to avoid barotrauma – Permissive hypercapnea. pCO2 60-90 OK if pH >7.1 – Air trapping
- 13. • Rate will affect CO2 • FiO2 and PEEP will affect Oxygenation (O2) • PEEP opens up more alveoli. But can increase intrathoracic pressure as well that increases the pressure in the right atrium and cause low BP
- 15. Compliance • When air is going in…airways determine the pressure seen in the pressure gauge. • Once the lungs are inflated and once there is no more movement in the airways, the thing that determines the pressure in the air circuit is no longer the resistance in the airways but the actual compliance of the lungs. • In PTX or P. edema (prevent lung from expanding), the machine will still give the same volume but you will see a higher pressure, as a result of decreased compliance
- 16. • Peak pressure is what is generated when air flows = Airways (of pt and tubes) Peak Pressure = lung stiffness + chest wall compliance + resistance • Plateau pressure is when the air stops = Lung compliance Affected by chest wall and lung parenchyma Peak pressure- Plateau pressure =<5mmHg (Normal) PEAK AND PLATEAU PRESSURE
- 18. High peak pressure Problem in airways • Bronchospasm • Secretions • Mucus plug • Occlusion of tip of ETT / Kinked ETT • Patient biting tube If Peak Pressure is > 30, lungs are at risk of hypo- oxygenation and hypoventilation. Find the cause: Consider suction or change the tube or bronchodilators
- 19. Low peak pressure Think of Air leak • Bronchopleural fistula • ETT cuff leak • ETT dislodged/ migrated • Disconnection of vent tubing • Vent dysfunction
- 20. High Plateau pressure Reduced lung compliance • Pneumothorax • Pulmonary edema • ARDS/Pneumonia • Atelectasis/ pleural effusions • Extrathoracic causes If Plateau Pressure is > 30, lungs are at risk of barotrauma Decrease Tidal volume until plateau pressure < 30 . Look for the cause, manage.
- 22. Source Not clear: Is it the vent or patient? • Remove the patient from the ventilator • Bag them • If they get better, it is probably a ventilator problem. • If they stay bad, it is probably a patient problem
- 23. General Troubleshooting D.O.P.E.S (Diagnose) • Displaced ET tube / ET tube cuff not inflated or has a leak • Obstruction of ET tube • Pneumothorax • Equipment malfunction (disconnection of the ventilator, incorrect vent settings, etc.) • Stacking (breath stacking / Auto- PEEP
- 24. General Troubleshooting D.O.T.T.S (Fix the problem) • Disconnect – Disconnect patient from the ventilator • Oxygen – Oxygenate patient with a BVM and feel for resistance as you bag • Tube position / function – Did the ET tube migrate? Is it kinked or is there a mucus plug? • Tweak the vent – Are the settings correct for this patient? • Sonogram (ultrasound) – Sonogram to look for pneumothorax, mainstem intubation, etc.
- 26. CASES CASE 1 • A patient has a polypharmacy overdose and is hypoventilating. How should you set the ventilator?
- 27. CASE 2 • The patient has angioedema. The intubation is for airway protection. They will be breathing on their own but need something in between their airway and their lungs to prevent closing of the airway. • How will you choose settings?
- 28. CASE 3 • A common reason for intubation is septic pneumonia. The patient has metabolic and airway protection problems. What is your setting?
- 29. CASE 4 55 yrs Male with COPD exacerbation and was intubated yesterday after he failed a trial of non-invasive ventilation. Earlier in the evening, the peak pressure was 45 cm H2O while the plateau pressure was 25 cm H2O. Alarm goes off and you find the peak pressure has risen to 60 cm H20 and the plateau pressure is now 40 cmH20. His heart rate has increased from 90 beats/minute to 110 beats/minute while his blood pressure has fallen from 110/85 to 90/70. The physical exam is noteworthy for diminished breath sounds on the left side of the chest. • What do plateau pressures represent on the ventilator? • • What do peak pressures represent on the ventilator? • • Where do you think the problem lies with this particular patient? • • What management steps should you institute at this point?
- 30. REFERENCE • Rosen’s 8th edition • Emcrit.com • Foamem.com • Lifeinthefastlane.com • Emrap.com
Editor's Notes
- #3: Altered, at risk of aspiration or osbtruction, upper airway obstruction; pulm edema, ARDS, pneumonia. Metabolic demand, pt getting tired Asthma/COPD
- #5: If P plateau > 30, decrease Tv and if that doesn’t work can switch to pressure control. Metabolic problem e.g. DKA, easy to titrate and follow with volume control.
- #8: PBW= MEN: 50+ 0.91 (Height in cm – 152.4) WOMEN: 45 + 0.91 (Height- 152.4)
- #9: Smaller amount of lung available for gas exchange. If you give normal amount as normal lung, the alveoli that are free will be expanded too much. Why we need low Tv
- #12: Goal is alveolar recruitment
- #16: In AC mode (VCV)for example, you set the volume and the pressure is variable depending on compliance Plateau pressure is Pressure required to hold the lungs and chest wall open when there is no air flow during inspiratory cycle.
- #17: Peak pressure is the summation of pressure generated from: 1) tidal volume and compliance; 2) resistance and peak inspiratory flow; and 3) PEEP Plateau pressure is Pressure required to hold the lungs and chest wall open when there is no air flow during inspiratory cycle
- #18: Peak pressure is the summation of pressure generated from: 1) tidal volume and compliance; 2) resistance and peak inspiratory flow; and 3) PEEP Plateau pressure is Pressure required to hold the lungs and chest wall open when there is no air flow during inspiratory cycle
- #21: Extrathoracic causes (body habitus, ascites, abdominal compartment syndrome, chest wall eschar, positioning (trendelenberg)
- #27: The patient needs intubation for airway protection. Consider AC volume control or SIMV as the patient is expected to wake up and has no apparent lung injury. Vt 6-8 cc/kg, RR 16-18, 100% -> 40%, PEEP 5
- #28: AC/PRVC -> Pressure support Vt 6-8 cc/kg, RR 16-18, 100% -> 40%, PEEP 5
- #30: AC, well sedated to give rest 6-8 cc/kg PEEP 7-10