Intro to Mechanical Ventilation for Residents
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An introduction to mechanical ventilation delivered at Nassau University Medical Center on 1/27/2016
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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 to use when Basic settings and modifications Monitoring Trouble Shooting
- 3. To vent or not 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 things the world stands Ventilation Oxygenation RR Vt FiO2 V/Q
- 5. Types of mechanical ventilation
- 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. Invasive
- 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 upper AW 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.
- 18. PEEP – Uses – Risks • Decreased venous return • Barotrauma • Increased ICP • GI Ulceration • Fluid retention (increased ADH vs decreased ANP)
- 19. PEEP Benefits • Improved V/Q Matching • Decreased Shunt • Decreased atelectasis • Decreased alveolar trauma • Supported spontaneous breathing
- 20. Doctor, what settings would 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 more like 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 come off 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 • T tube 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 the patient’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 yr old F, morbidly obese c OSA in extreme respiratory distress? – NIPPV? – IPPV? – No mechanical ventilation?
- 34. NIPPV may be used in all of the following, except: 1. COPD 2. CHF 3. CPR 4. Pneumonia 5. Asthma 6. Myesthenia gravis
- 35. The most appropriate Mode/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 slideset is now available at: www.EMIMDoc.org
Notes de l'éditeur
- 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.
- 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.
- Describe practical differences between IPPV and NIPPV
- 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
- 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.
- Titrate FiO2 as low as possible c O2 sat > 90%
- Not hard and fast indications, much room for clinical decision
- 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
- 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
- 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
- NL i:e = 1:2-3 Based on discussion from the previous slide
- 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
- Mnemonic for desaturating vented patient
- Rapid shallow breathing index
- 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.
- Straightforward yes, NIPPV. Not to be intubated unless have to. Discussion of weaning difficulty.
- CPR: Patient must be breathing in order for NIPPV to work.
- 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.