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Intro to Mechanical Ventilation for Residents
This document provides an overview of mechanical ventilation, including its goals, general principles, types, settings, monitoring, troubleshooting, indications, contraindications and complications. It discusses non-invasive positive pressure ventilation and invasive mechanical ventilation, reviewing various modes, settings, weaning methods and specific management considerations for different patient populations. The key points are monitoring patients on mechanical ventilation for oxygenation and ventilation issues, addressing those issues following the DOPE/SEDOP mnemonic, and carefully considering indications and timing for initiation and discontinuation of mechanical support.
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Intro to Mechanical Ventilation for Residents
- 1. Mechanical Ventilation David Marcus,MD @EMIMDoc – EMIMDoc.org Emergency Medicine/Internal Medicine/Medical Ethics, LIJ Medical Center Nassau University Medical Center – 1/272016
- 2. Goals General principles What touse when Basic settings and modifications Monitoring Trouble Shooting
- 3. To vent ornot to vent? 85 y/o M c CHF, rales on physical exam, breathing comfortably, O2 sat 90% 45 yr old F, morbidly obese c OSA in extreme respiratory distress 20 y/o F c h/o asthma, multiple intubations in the past, audible wheeze, RR 22 94 y/o F, minimally responsive c HR 32, BP 60/palp, RR 10, O2 sat 95% ORA
- 4. On two thingsthe world stands Ventilation Oxygenation RR Vt FiO2 V/Q
- 5. Types of mechanicalventilation
- 6. Uses of NIPPV •COPD: Fewer intubations, mortality benefit. • CHF: Fewer intubations, mortality benefit • PNA: May use for hypoxia. No clear evidence. • Asthma: Impending respiratory failure. Unclear data. • DNI • OSA • DSI OTHER…
- 7. Modes CPAP When CO2 OK,but cannot oxygenate BiPAP For CO2 help (+/- O2 problem) To decrease CO2, increase delta To increase O2, increase i/ePAP
- 8. Running the Numbers •Initial BiPAP setting: 10/5 cmH2O • Max iPAP 20-25 cmH2O • Max ePAP 10-15 cmH2O • Start FiO2 at 1.0 and titrate • Back up rate 12-16 / min
- 9. Know This! • Contraindications: –Cardiac arrest – MI – Apnea – Sufficiently impaired LOC – Copious secretions/emesis – Facial trauma/impaired AW • Likely to fail in severe acidosis, ARDS
- 11.
- 12. Indications for Intubation •Failure to maintain AW (loss of reflexes) • Failure to maintain AW tone • Failure to ventilate • Failure to oxygenate • Clinical course expected to result in any of the above
- 13. Contraindications Loss of upperAW anatomy Total upper AW obstruction Relative contraindication: Anticipated difficult AW
- 14. Vents • Control mechanisms 1.VCV (fixed volume) 2. PCV (fixed pressure) • Variables: – Trigger (what starts a breath): flow, pressure, time – Limit: Pressure, Flow – Cycle (what ends a breath): Time, flow, Pressure, Volume
- 15. Modes 1. CMV –Machine breaths only 2. AC – fixed number of machine breaths + pt triggered breaths at fixed volume. 3. SIMV – fixed rate/volume machine breaths + pt triggered breaths limited by pt effort 4. May use pressure support (PSV) in SIMV or CPAP – provides additional support during spontaneous inspiration (to overcome resistance of system).
- 16. Other modes • APRV(airway pressure release ventilation) • PAV (proportional assist ventilation) • Prone positioning • IRV (inverse ratio ventilation) • Permissive hypercapnia (goal = decreased peak AW pressure, i.e. in asthmatics) Via lower RR, lower Vt.
- 17.
- 18. PEEP – Uses – Risks •Decreased venous return • Barotrauma • Increased ICP • GI Ulceration • Fluid retention (increased ADH vs decreased ANP)
- 19. PEEP Benefits • Improved V/QMatching • Decreased Shunt • Decreased atelectasis • Decreased alveolar trauma • Supported spontaneous breathing
- 20. Doctor, what settingswould you like? • Mode • Rate (12-14) • FiO2 (Start at 1.0 and titrate down) • PEEP (~5 cmH2O) • Vt (6-8 ml/kg) • (I:E ratio)
- 21. Patient Specific Management •56 yr old M, traumatic PTX/rib fractures • 28 yr old obese F, severe influenza, ARDS • 76 year old M, subarachnoid hemorrhage • 18 yr old F, severe asthma, now intubated • 82 yr old M, septic shock
- 22. Monitoring • Clinical Observation •Pulse Oximetry • ABG/VBG • Capnometry (End Tidal CO2) • BMP • Peak and Plateau pressures, Auto-PEEP • Volumes/Air Leak
- 24. You’re Doing Great! •Your intubated patient is doing well. • Sats are good, he appears comfortable. • And then…
- 25. Don’t Worry –It’s All DOPE(s) Why is the patient is hypoxic? • D – Dislodged Tube/Disconnect • O – Obstructed system • P - Pneumothorax • E – Equipment Failure • (S – Stacked breaths, if asthmatic)
- 26. Don’t Worry –It’s All DOPE(s) D O P E S Check connections, confirm tube placement via ETCO2 (+/- direct visualization) Check all tubing, suction deep into ETT Ultrasound or CXR to r/o pneumothorax Disconnect the vent and attach a BVM In asthmatics, disconnect the vent and listen
- 27. Though, it’s morelike SEDOP • First, disconnect the vent, • then switch to a BVM. • Confirm tube placement, • Suction, check for obstructions • Verify and reconnect tubing • Check for PTX (depending on suspicion)
- 28. When to comeoff the vent? • As soon as possible • Two questions: – Can the pt protect the AW? – Can the pt oxygenate and ventilate?
- 29. Decision tools RSBI =RR/Vt(Liters) RSBI>105 = poor prognosis for weaning (PPV 65%, NPV 95%) First --- oxygenating well on low FiO2 and low PEEP Also: • Determine cause of ventilatory dependance • Rectify correctible problems • Address: – Fluid balance – Mental status and psychological factors – Acid-base status – Electrolyte disturbance
- 30. Weaning Methods • Ttube trial • IMV • PSV • NPPV
- 31. Vent complications • PTX •Biotrauma (the injury formerly known as barotrauma): overdistention or rupture, alveolar hypoperfusion, and repetitive shear stresses across alveolar walls • Hemodynamic compromise • VAP
- 32. Summary • What’s thepatient’s problem? – CO2/O2/AW • NIPPV – Know settings, contraindications! • IPPV – Modes, General vent settings – DOPE(s) • Further reading: Vent strategies for restrictive vs obstructive lung disease
- 33. Summary • 45 yrold F, morbidly obese c OSA in extreme respiratory distress? – NIPPV? – IPPV? – No mechanical ventilation?
- 34. NIPPV may beused in all of the following, except: 1. COPD 2. CHF 3. CPR 4. Pneumonia 5. Asthma 6. Myesthenia gravis
- 35. The most appropriateMode/Vt for a sedated, ventilated patient with normal lungs: 1. CMV/6-8 ml/kg TBW 2. CMV/6-8 ml/kg IBW 3. AC/10-15 ml/kg TBW 4. AC/6-8 ml/kg IBW
- 36. THANK YOU! The slidesetis now available at: www.EMIMDoc.org
Editor's Notes
- #4 Straightforward no. But may need (what type?) if desatting or getting tired Straightforward yes, but to intubate or not? Discussion of weaning difficulty. Straightforward no. But special case of asthmatics – give mm a rest, deal with auto-PEEP, permissive hypercapnia, etc. Yes, needs intubation for AW protection. Also, possible case of ingestion, may need GI irrigation, etc.
- #5 DRAW AW’S DOWN TO ALVEOLI Ventilation – Essentially, elimination of CO2. Determined by minute ventilation – dependant upon respiratory rate and Vt. Ventilatory needs change based on physiology (i.e. infections increase CO2 production due to increased metabolic rate, acidosis, chronic retainers have higher tolerance, etc) Oxygenation – Like it sounds - ability to equilibrate the O2 in the blood with O2 in alveolar air. Dependant primarily on V/Q (affected by pressures) matching and FiO2 NOT rate or Vt 3) Dead space: Vdead/Vtidal~ 0.35 (35% deadspace) – if higher, inefficient ventilation. If Vd/Vt>0.6 may have trouble weaning.
- #6 Describe practical differences between IPPV and NIPPV
- #7 COPD: reduces work of breathing and splints airways open, improving ventilation-perfusion matching. CHF: reduces work of breathing, improves cardiac output by decreasing preload and afterload, redistributes lung water, and improves ventilation-perfusion matching thereby reducing shunt. OTHER: Neuromuscular Dz, CF, ARDS, decompensated OSA
- #8 CPAP: May be better for Acute Pulmonary Edema (CHF, etc), fear of increased risk of MI c BiPAP in CHF, but recent data sheds doubt. OSA. BiPAP: May be used always, question of risk of MI in CHF. Preferred mode for COPD.
- #9 Titrate FiO2 as low as possible c O2 sat > 90%
- #13 Not hard and fast indications, much room for clinical decision
- #15 Control: VCV - most common mode of ventilation in adults in US but does not take variable lung compliance and AW resistance into acct. – results in varying and sometimes high pressures. PCV - var. volume, lung chest compliance dependant, pressures. But, accurate pressure control to minimize risk of alveolar injury. Mode used sometimes in transport vents. Cheaper. More common in peds. Compliance = delta P/delta V Variables: Any or all of these parameters are controlled by the vent and can be modified, depending on the mode of operation
- #16 CMV (cont mechanical ventilation): for the apneic pt AC (assist control): based on pt generated negative pressure below PEEP, but Vt is determined by machine SIMV (synchronized intermittent mechanical venti): Vt of extra breaths determined by pt. Usually done c Pressure support
- #17 APRV - high CPAP mode c intermittent drop in pressure. Use for refractory hypoxemia… Prone - (recruitment for pulm edema, decrease hyperinflation. Triangular chest prob benefits more – more posterior lung to be recruited) IRV - for hypoxemic resp failure PH - Allows longer exp for clearing of auto PEEP, reduces cardiovascular complications, alveolar injury. However, increases cerebral vasodilation----ICP, shifts O2 dissociation to RIGHT so HgB unloads early and other results of acidosis
- #18 NL i:e = 1:2-3 Based on discussion from the previous slide
- #19 IMPROVES OXYGENATION Reduce atelectasis thus improving V/Q matching Shifts fluid out of alveolar space Decrease venous return, beneficial in CHF. Like taking NTG. RISKS: Decreased venous return Barotrauma
- #26 Mnemonic for desaturating vented patient
- #30 Rapid shallow breathing index
- #31 In one trial, 109 mechanically ventilated patients who could not sustain two hours of spontaneous breathing were randomly assigned to wean by T tube trials, IMV, or PSV. The duration of weaning was shorter with PSV (mean 5.7 days) than either T tube trials (mean 8.5 days) or IMV (mean 9.9 days). In a similar trial, 130 mechanically ventilated patients who had respiratory distress during a two hour trial of spontaneous breathing were randomly assigned to one of four weaning methods: T tube trials at least twice daily, T tube trials once daily, IMV, or PSV. T tube trials led to extubation approximately three times more quickly than IMV and twice as quickly as PSV. There was no difference in the rate of weaning when once daily T tube trials were compared to more frequent T tube trials, or when IMV and PSV were compared.
- #34 Straightforward yes, NIPPV. Not to be intubated unless have to. Discussion of weaning difficulty.
- #35 CPR: Patient must be breathing in order for NIPPV to work.
- #36 AC/6-8 ml/kg IBW. Lung volume proportional to height not total mass. AC good for practically all sedated patients. CMV would require paralysis of many patients, otherwise increased work of breathing, stress, etc.