intro to mechanical ventilation for residents
TRANSCRIPT
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Mechanical Ventilation
David Marcus, MD@EMIMDoc – EMIMDoc.org
Emergency Medicine/Internal Medicine/Medical Ethics, LIJ Medical CenterNassau University Medical Center – 1/272016
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Goals
General principlesWhat to use when
Basic settings and modificationsMonitoring
Trouble Shooting
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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
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On two things the world stands
Ventilation Oxygenation
RRVt
FiO2V/Q
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Types of mechanical ventilation
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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
• DSIOTHER…
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Modes
CPAPWhen CO2 OK, but cannot oxygenate
BiPAP For CO2 help (+/- O2 problem)
To decrease CO2, increase deltaTo increase O2, increase i/ePAP
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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
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Know This!
• Contraindications: – Cardiac arrest– MI – Apnea– Sufficiently impaired LOC– Copious secretions/emesis– Facial trauma/impaired AW
• Likely to fail in severe acidosis, ARDS
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Invasive
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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
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Contraindications
Loss of upper AW anatomyTotal upper AW obstruction
Relative contraindication:Anticipated difficult AW
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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
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Modes1. 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).
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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.
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Settings
RateFiO2
VtPEEP (Pressures)
i:e ratio
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PEEP
– Uses– Risks
• Decreased venous return• Barotrauma• Increased ICP• GI Ulceration• Fluid retention (increased ADH vs decreased ANP)
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PEEP
Benefits• Improved V/Q Matching• Decreased Shunt• Decreased atelectasis• Decreased alveolar trauma• Supported spontaneous breathing
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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)
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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
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Monitoring
• Clinical Observation• Pulse Oximetry• ABG/VBG• Capnometry (End Tidal CO2)• BMP• Peak and Plateau pressures, Auto-PEEP• Volumes/Air Leak
Alarms!Don’t Ignore Alarms!
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You’re Doing Great!
• Your intubated patient is doing well. • Sats are good, he appears comfortable.
• And then…
Alarms!Don’t Ignore Alarms!
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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)
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Don’t Worry – It’s All DOPE(s)
DOPES
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
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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)
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When to come off the vent?
• As soon as possible• Two questions:
– Can the pt protect the AW?– Can the pt oxygenate and ventilate?
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Decision toolsRSBI = 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
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Weaning Methods
• T tube trial• IMV• PSV• NPPV
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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
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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
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Summary
• 45 yr old F, morbidly obese c OSA in extreme respiratory distress?– NIPPV?– IPPV?– No mechanical ventilation?
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NIPPV may be used in all of the following, except:
1. COPD2. CHF3. CPR4. Pneumonia5. Asthma6. Myesthenia gravis
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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