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.
Intro to Mechanical Ventilation for Residents
David Marcus, MD
@EMIMDoc – EMIMDoc.org
Emergency Medicine/Internal Medicine/Medical Ethics, LIJ Medical Center
Nassau University Medical Center – 1/272016
What to use when
Basic settings and modifications
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
On two things the world stands
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
Loss of upper AW anatomy
Total upper AW obstruction
Anticipated difficult AW
• Control mechanisms
1. VCV (fixed volume)
2. PCV (fixed pressure)
– Trigger (what starts a breath): flow, pressure,
– Limit: Pressure, Flow
– Cycle (what ends a breath): Time, flow,
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).
• 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.
• Decreased venous return
• Increased ICP
• GI Ulceration
• Fluid retention (increased ADH vs decreased ANP)
Doctor, what settings would you like?
• Rate (12-14)
• FiO2 (Start at 1.0 and titrate down)
• PEEP (~5 cmH2O)
• Vt (6-8 ml/kg)
• (I:E ratio)
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
You’re Doing Great!
• Your intubated patient is doing well.
• Sats are good, he appears comfortable.
• And then…
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)
Don’t Worry – It’s All DOPE(s)
Check connections, confirm tube placement via ETCO2 (+/-
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
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)
When to come off the vent?
• As soon as possible
• Two questions:
– Can the pt protect the AW?
– Can the pt oxygenate and ventilate?
RSBI = RR/Vt(Liters)
RSBI>105 = poor prognosis for weaning (PPV 65%, NPV 95%)
First --- oxygenating well on low FiO2 and low PEEP
• Determine cause of ventilatory dependance
• Rectify correctible problems
– Fluid balance
– Mental status and psychological factors
– Acid-base status
– Electrolyte disturbance
• Biotrauma (the injury formerly known as
barotrauma): overdistention or rupture,
alveolar hypoperfusion, and repetitive
shear stresses across alveolar walls
• Hemodynamic compromise
• What’s the patient’s problem?
– Know settings, contraindications!
– Modes, General vent settings
• Further reading: Vent strategies for
restrictive vs obstructive lung disease
• 45 yr old F, morbidly obese c OSA in
extreme respiratory distress?
– No mechanical ventilation?
NIPPV may be used in all of the
6. Myesthenia gravis
The most appropriate Mode/Vt for a
sedated, ventilated patient with normal
1. CMV/6-8 ml/kg
2. CMV/6-8 ml/kg
3. AC/10-15 ml/kg
4. AC/6-8 ml/kg IBW
The slideset is now available at: