Liberation from the ventilator (2024)

CONTENTS

• Spontaneous Breathing Trial (SBT)
  • If the patient fails the SBT
    • Causes of failed SBT
    • Investigation
  • If the patient passes the SBT
• A trial of extubation
• Post-extubation support
• Timing of tracheostomy
• Some additional concepts
  • Unplanned extubation
  • Nocturnal extubation
  • Bad ideas in ventilator weaning
  • p0.1
• Podcast
• Pitfalls

rapid reference: pre-extubation checklist

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#1/6) sedation optimized

• Ideal target: following commands, mildly distressed by ETT when sedation held.
• Dexmedetomidine is an excellent agent to facilitate extubation, so it may be helpful to transition to this agent (e.g., cross-taper from propofol onto dexmedetomidine).
  • When in doubt, consider transitioning to dexmedetomidine plus pain-dose ketamine infusions (KetaDex™).
• Excess sedation may be problematic. Note that if patients are very comfortable with the endotracheal tube in place, they may be at risk for becoming overly somnolent following extubation (when they are exposed to less stimulation).
  • Reduce or stop any long-acting gtts (e.g., fentanyl) several hours before extubation.

#2/6) volume status optimized

• Extubation will generally increase preload and blood pressure.
• Review input/output trends and examine the patient for fluid overload.
• Consider diuresis before extubation.

#3/6) acid-base status optimized

• Metabolic acidosis may increase the work of breathing, because it requires the patient to generate a compensatory respiratory alkalosis. Thus, any metabolic acidosis should be treated prior to extubation(e.g., treatment of NAGMA with IV bicarbonate).
• Patients with chronic hypercapnia and chronic compensatory respiratory alkalosis should ideally be restored to their baseline bicarbonate level prior to extubation.

#4/6) review chest radiology: any treatable disease processes?

• Pleural effusion: consider drainage vs. diuresis. It may take re-expanded lung tissue some hours to regain full function. Thus, the ideal timing of effusion drainage is well before extubation.
• Atelectasis: lung recruitment.

#5/6) review insulin regimen & glycemic control

• Extubation often involves discontinuation of enteral nutrition.
• For patients on substantial doses of insulin, consider taking steps to avoid hypoglycemia:
  • Reduce or hold insulin.
  • Frequent fingerstick glucose measurement.

#6/6) last minute items

• Suction stomach: Before extubation, set the gastric tube to suction (if it's a sump tube).
• Check for cuff leak (if indicated – see figure below):

spontaneous breathing trial (SBT)

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A spontaneous breathing trial should generally be performed daily among patients who are sufficiently stable. Rough (and largely arbitrary) criteria are listed below, but these need to be individualized. For example, patients with morbid obesity may require high PEEP levels to prevent atelectasis (e.g., 8-10 cm), so it may be appropriate to wean such patients with a high PEEP if the patient is otherwise ready for extubation. Alternatively, a patient with ARDS and normal weight might not be ready for extubation if they are strongly dependent on 10 cm PEEP.

criteria for when a patient is ready for a SBT

• Respiratory:
  • FiO2 ≤50% with a PEEP ≤10 cm, although higher PEEP values may be acceptable in morbid obesity (more on this below 📖).(33797429)
  • PaCO2 or etCO2 is normal (or close to baseline, for patients with chronic hypercapnia).
• Cardiovascular:
  • No ongoing myocardial ischemia.
  • Heart rate <140 b/m.
  • Not on high-level vasopressors (e.g., <15 mcg/min norepinephrine).
• Neurologic:
  • Patient is arousable (and ideally following commands, but this isn't an absolute requirement – particularly in patients with neurologic injury).
• Renal:
  • No uncontrolled acid/base abnormalities.
    • For most patients, this is means having a serum bicarbonate level close to normal.
    • For patients who previously had a chronic compensatory metabolic alkalosis (e.g., due to COPD or obesity hypoventilation), the bicarbonate should ideally be close to the patient's baseline bicarbonate level.

optimizing sedation prior to a spontaneous breathing trial

• This is both essential and tricky:
  • The patient should ideally be sedated deeply enough to be comfortable and not anxious.
  • The patient should ideally be sedated lightly enough to have a relatively normal respiratory drive. As a surrogate for this, the patient should be easily arousable.
• In challenging situations, dexmedetomidine is an excellent sedative to use during the extubation process. Dexmedetomidine doesn't suppress the respiratory drive, so it may be continued throughout the SBT, extubation, and even after the patient is extubated.

designing a spontaneous breathing trial

• Settings: There are numerous options which seem to perform similarly:
  • The typical settings for a spontaneous breathing trial are pressure support ventilation, with 5 cm pressure support and 5 cm PEEP (“5/5”). The goal of these settings is to cancel out the resistance of the endotracheal tube, simulating breathing without a ventilator.
  • An alternative approach is continuous positive airway pressure (CPAP, with a pressure ~5 cm) plus automatic tube compensation (ATC). Automatic Tube Compensation is a commercial setting designed to compensate for the resistance of the endotracheal tube. This may be superior to choosing an arbitrary level of pressure support (e.g., 5 cm pressure support) – particularly for patients with atypical endotracheal tube size (e.g., #6 or #9 endotracheal tube).
• Duration: If the patient can tolerate this for 30 minutes, they are likely ready for extubation.

to “pass” a spontaneous breathing trial, the patient should achieve the following:

• Adequate oxygenation:
  • For example, saturation >88% without requiring more than ~50% FiO2.
  • High FiO2 requirement can be supported by weaning to high-flow nasal cannula, so extubation may be considered at moderately high FiO2 requirements (especially in patients with chronic hypoxemia).
• Adequate ventilation: Occasionally patients with a weak respiratory drive may look OK, despite having occult hypoventilation. This is mostly an issue among patients with chronic hypercapnia. Occult hypoventilation can be detected as follows:
  • A drop in minute ventilation during the breathing trial is highly suggestive.
  • A drop in tidal volume, which may cause a greater fraction of each breath to represent anatomic dead space (such that the breaths are ineffective).
  • The end-tidal CO2 increases by >10 mm during the breathing trial.(8796386)
  • (Note that routinely checking a blood gas is unnecessary, if attention is paid to these other aspects.)
• No signs of severe fatigue, which may include the following:
  • Agitation, diaphoresis, use of accessory muscles.
  • High rapid-shallow breathing index: (Respiratory Rate)/(Tidal volume in liters) > 105.
    • Rapid breathing with large tidal volumes suggests anxiety, rather than ventilatory failure. This is often compatible with an ability to extubate.
    • A rapid-shallow breathing index >105 is not an absolute contraindication to extubation. Rapid-shallow breathing index >105 has ~44% specificity for predicting extubation failure – so it's a red flag – yet some patients can still be extubated despite a high rapid-shallow breathing index.(35815895) For example, some patients with chronic respiratory dysfunction may have chronic tachypnea (e.g., patients with interstitial lung disease). In such patients, extubation may be attempted despite a rapid-shallow breathing index >105, as long as the underlying cause of respiratory failure has been reversed and other indicators are favorable.
• No obvious complication resulting from the SBT (e.g., arrhythmia, marked bradycardia, hypotension, severe hypertension, depressed mental status, agitation).(35815895)

what if the patient develops apnea during the SBT?

• If a patient fails a SBT due to “apnea,” don't just give up – these patients can often be extubated.
  • Ventilator apnea alarms are very sensitive, automatically causing the ventilator to flip into an emergency mode that provides full ventilator support. This is a good patient-safety feature, but it can sometimes interfere with a SBT.
• Common causes of apnea during a SBT include the following:
  • (a) The patient was being hyperventilated prior to the trial (in this case, it may take a few minutes of apnea before the patient becomes hypercapnic, causing the respiratory drive to initiate breaths). This may be easily managed as follows:
    • i) place the patient on a standard ventilator mode.
    • ii) decrease the set rate on the ventilator, in order to stimulate the patient to start taking spontaneous breaths.
    • iii) repeat the SBT.
  • (b) The patient has a Cheyne-Stokes breathing pattern (some patients have a chronic breathing pattern with periodic episodes of apnea; this isn't a contraindication to extubation).
  • (c) The patient is over-sedated.
• General approach to a patient who fails due to apnea:
  • (a) If the patient looks over-sedated, hold all sedation and repeat the SBT in a few hours when they are more awake.
  • (b) If the patient looks awake, repeat the SBT while carefully observing the breathing pattern and end tidal CO2.

if the patient fails the SBT

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See Also

Protocol: T-piece versus pressure-support ventilation for spontaneous breathing trials before extubation in patients at high risk of reintubation: protocol for a multicentre, randomised controlled trial (TIP-EX)To T-piece or PSV? That is the question. – CriticalCareNowComparison of T-piece and pressure support ventilation as spontaneous breathing trials in critically ill patients: a systematic review and meta-analysisEffect of Pressure Support vs T-Piece Ventilation on Successful Extubation of Mechanical Ventilation

when to repeat a SBT?

• After failure, the patient should be placed back on a full level of ventilator support.
• The SBT may be repeated later in the day if there is something which can be easily manipulated which will improve the likelihood of success (e.g., holding sedation to allow the patient to wake up further).
• If there is no readily reversible cause of failure, it is usually best to repeat a SBT the following morning.

causes of failing a SBT

Volume overload / cardiogenic pulmonary edema

• Clues may include:
  • Input/output records show net positive fluid balance.
  • Peripheral edema.
  • History of heart failure.
  • POCUS shows structural evidence of heart failure (e.g., reduced ejection fraction, atrial dilation).
  • POCUS shows systemic congestion and pulmonary edema (which may emerge or worsen during a spontaneous breathing trial).
  • Hypertension occurring during a spontaneous breathing trial may be suggestive (although there are many alternative explanations for this, such as anxiety or hypercapnia).
  • Passive leg raise: Failure of passive leg raise to augment the cardiac output implies that the patient is volume overloaded and may benefit from diuresis.(30627804)
• Treatment may commonly include:
  • Diuresis (or dialysis), if volume overloaded.
  • Afterload reduction, if hypertensive (e.g., ACE inhibitors or a combination of oral hydralazine plus isosorbide dinitrate). Note, however, that if hypertension is solely due to volume overload, then the ideal treatment is simply volume removal.
  • Continuation of positive pressure (e.g., spontaneous breathing trial with incorporation of PEEP, extubation to CPAP or BiPAP).

Angina occurring during SBT:

• Diagnosed via: EKG during SBT, chest pain during SBT (if able to communicate), history of coronary artery disease.
• Treatment: Beta-blockade, target a hemoglobin level >8 mg/dL, potentially revascularization.

Anxiety:

• Diagnosed via:
  • Patient appearance during SBT.
  • Tachypnea with high tidal volumes and low etCO2 (hyperventilation).
• Treatment:
  • May repeat SBT while infusing dexmedetomidine, or may simply trial extubation (depending on clinical judgement).

Chronic tachypnea

• Some patients have chronic tachypnea due to chronic respiratory dysfunction (e.g., interstitial lung disease). They may never have a favorable rapid/shallow breathing index. However, they may still be extubated, once their acute illness resolves.
• Diagnosed via: Review of history, thoracic radiology, baseline vital signs.
• Treatment: May be reasonable to extubate patient despite some tachypnea during SBT, if they are otherwise optimized for extubation.

Bronchospasm (COPD/asthma):

• Diagnosed via: Lung auscultation, etCO2 waveform, ventilator waveform.
• Treatment: Steroid, bronchodilators, narrow spectrum antibiotics in COPD (more on COPD).

Pleural effusion:

• Diagnosed via: Chest x-ray, thoracic ultrasonography.
• Treatment: Thoracentesis or pigtail drain (if moderate-large and interfering with extubation).

Ventilator associated pneumonia:

• Diagnosed via: Chest x-ray, sputum gram stain/cx (see chapter on VAP).
• Treatment: Antibiotics.

Metabolic acidosis:

• Diagnosed via: Review of electrolytes.
• Treatment: Depends on etiology.

Elimination of chronic, compensatory metabolic alkalosis (e.g., patient with COPD and chronic compensatory metabolic alkalosis whose bicarbonate level is now “normal” – but not normal for the patient).

• Diagnosed via: Review of electrolytes and blood gas values, comparison to baseline values when not ill.
• Treatment: Try to restore the patient's baseline bicarbonate level (may require IV bicarbonate administration and/or diuresis).

Electrolyte abnormalities (especially hypophosphatemia; also hypomagnesemia and hypokalemia)

• Diagnosed via: Measurement of electrolyte levels.
• Treatment: Repletion or management depending on abnormalities.

Pulmonary embolism:

• Diagnosed via: Persistent or worsening respiratory failure without a good explanation, CT angiography.
• Treatment: Heparin or rarely alteplase.

Atelectasis and/or mucus plugging:

• Diagnosed via: Chest X-ray, thoracic ultrasonography, and/or CT scan.
• Treatment:
  • Primary treatment is usually to increase the mean airway pressure (e.g., increased PEEP, or APRV).
  • Other treatments may include: chest physiotherapy, rarely bronchoscopy for suctioning of mucus plugs.

Small ETT size causing excess airway resistance:

• Diagnosed via: Comparison of ETT to patient's height.
• Treatment: Exchange for larger ETT, use of automatic tube compensation mode (ATC) for the spontaneous breathing trial in order to more accurately cancel out the resistance of the ETT, or simply trial extubation (depending on clinical judgement).

Occult endotracheal tube occlusion due to inspissated secretions:

• Diagnosed via: Bronchoscopy, ventilator mechanics may show increased resistance to airflow. Uncommon, may be difficult to diagnose.
• Treatment: Exchange for new ETT, or simply trial extubation (if patient is otherwise ready for extubation).

Ventilator dyssynchrony or inadequate ventilator support, causing respiratory exhaustion:

• Diagnosed via: Persistent dyssynchrony, or inadequate levels of driving pressure (e.g., during adaptive-support modes such as AutoFlow or Pressure Regulated Volume Control).
• Treatment: Adjust ventilator to provide adequate levels of support and eliminate dyssynchrony.

investigation of a failed SBT

• 💡Patients will often have several factors which are holding them back. All treatable factors should be addressed.
• The first step is identifying problems is understanding exactly how the patient failed (e.g., due to tachypnea, agitation, apnea, or hypercapnia?). When in doubt, it may be helpful to repeat the spontaneous breathing trial to examine exactly what happens (e.g., are there EKG changes? does an ultrasound during the SBT show new appearance of pulmonary edema?).(32166566)

investigations to consider:

• Electrolytes including Ca/Mg/Phos.
• Review of fluid balance & examination for volume overload.
• Chest imaging (CXR, POCUS).
• Review of pH status, including a comparison to baseline bicarbonate levels (if available).
• CT angiography may be reasonable, if nothing else is revealing.

if the patient passes the SBT

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a spontaneous breathing trial isn't everything

• If the patient passes a SBT, this suggests that they are strong enough to sustain the work of breathing. However, two other factors must also be considered:
  • (#1) What is the risk of post-extubation laryngeal edema?
  • (#2) Will the patient be able to maintain their airway?

laryngeal edema risk & cuff leak test

• Lack of a cuff leak increases the risk of post-extubation stridor, but this test is far from perfect.
• An approach towards testing for cuff leak and management is shown below, based on consensus guidelines.(27762595) This algorithm represents a compromise between the “cowboy” approach (ignoring cuff leak and immediately extubating) vs. the ultra-conservative approach (delaying extubation for 24-48 hours while treating with steroid). 🌊

ability to maintain a patent airway

• A spontaneous breathing trial doesn't evaluate the patient's ability to maintain a patent airway, so this must be considered prior to extubation. This is a subjective judgement, which hinges on the following four factors:
  • (1) How good is the patient's mental status?
  • (2) Is the patient producing lots of secretions? (e.g., requires suctioning more frequently than every 2 hours)
  • (3) Does the patient have a history of hypercapnia?
  • (4) Does the patient have a strong cough? (assessed subjectively while suctioning the patient)
• If 1-2 of the above factors is unfavorable, that's probably OK. However, if 3-4 factors are unfavorable then the risk of reintubation is substantial.
• If these factors are likely to improve over time, then it may be wise to delay extubation (e.g., a patient recovering from acute stroke who is gradually waking up with improving secretions). However, if these factors aren't likely to improve over time, then it may be worth trialing extubation (e.g., a patient with chronically poor mental status who has been optimized as much as possible).

suction stomach prior to extubation

• For patients with a Salem sump tube in place (e.g., orogastric or nasogastric tubes), feeding can be continued until a decision has been made to extubate the patient. This avoids the necessity to stop and restart feeding every morning. Once the decision to extubate has been made, the tube can be placed to suction to empty the stomach.
• For patients with a nasal small-bore, post-pyloric feeding tube in place, feeding may be stopped prior to extubation. It is often desirable to leave such tubes in place during the extubation process.

the concept of a “trial of extubation”

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a spontaneous breathing trial doesn't always yield an obvious result

• A breathing trial is generally conceptualized as being pass-fail, but in reality there are some patients who perform marginally during the SBT without either definitely passing or failing.
• For example, consider the rapid-shallow breathing index during a spontaneous breathing trial. If the rapid-shallow breathing index is very low, that suggests readiness to extubate. If the rapid-shallow breathing index is very high, that implies inability to extubate. But if the rapid-shallow breathing index is ~100, this is largely uninformative (in general, continuous parameters are often noninformative at values around their cutoff points – discussed further here).

a reasonable reintubation rate is ~15%

• It is impossible to predict exactly which patients will require reintubation.
• Either premature or delayed extubation may be harmful:
  • Premature extubation may lead to reintubation and associated risks.
  • Delayed extubation subjects patient to increased risks of ventilator associated pneumonia, delirium, and deconditioning.
• It is generally believed that a reasonable reintubation rate is ~15%. This is consistent with modern data from clinical studies of extubation.
  • If your reintubation rate is <<15%, this suggests that you're extubating patients too late.
  • If your reintubation rate is >>15%, this suggests that you're extubating patients prematurely.
• Therefore, whenever we extubate a patient, we are in fact merely trialing extubation.
  • If a patient requires reintubation, this isn't a failure. This is an inevitable event in the context of an uncertain universe.
  • In many cases, we will be unable to know whether the patient can tolerate extubation without trialing it.

when a trial of extubation may be considered

• (#1) If a patient passes the spontaneous breathing trial and is otherwise ready for extubation, then a trial of extubation is clearly indicated.
• (#2) If the patient is consistently performing marginally on their spontaneous breathing trial (without definitively passing or failing), then a trial of extubation may be considered. In this situation, extubation should be delayed until other potential causes of respiratory failure have been investigated. Once the patient is fully investigated and optimized, a trial of extubation may be warranted, even if the patient can't pass the spontaneous breathing trial with flying colors.
  • One example of this is that a patient who is persistently borderline may warrant a trial of extubation prior to placement of a tracheostomy.

post-extubation support

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extubation to high-flow nasal cannula (HFNC)

• RCTs have demonstrated that extubation to HFNC reduces reintubation and ICU length of stay. The general concept is that HFNC reduces the work of breathing, thereby preventing patients from fatiguing after extubation.
• Post-extubation HFNC may benefit even patients who are low-risk for reintubation (this is counterintuitive, but it has been shown in a multicenter RCT).(26975498) Thus, almost all patients should arguably be extubated to HFNC (with the exception of patients intubated for a very short period of time to facilitate a procedure).
• In order to be effective:
  • (a) HFNC needs to be continued for a substantial amount of time (studies have used 24-48 hours). One exception to this is that patients who are on chronic nocturnal BiPAP may be maintained with a combination of BiPAP at night and HFNC during the day.
  • (b) The flow rate should be increased as high as can be tolerated by the patient (ideally 50-60 liters/minute).

extubation to BiPAP

• There is literature supporting extubation to BiPAP, especially among patients with heart failure or COPD. HFNC and BiPAP have equivalent efficacy.(27706464) In reality, it is often difficult to keep patients wearing the BiPAP mask following extubation, so HFNC may be a more feasible strategy.
• The best candidates for extubation to BiPAP may include:
  • Patients with morbid obesity and difficulty maintaining lung recruitment (e.g., body mass index >35).(33797429)
  • Tenuous COPD patients.
  • Patients who are cooperative, not anxious, and likely comply with the BiPAP mask.
• It's often helpful to continue BiPAP for about 24 hours (with short breaks), after which the patient may be transitioned to high-flow nasal cannula during the day and BiPAP at night. One study suggested that a combination of HFNC during the day plus nocturnal BiPAP might be the most powerful strategy to prevent reintubation, especially among patients with hypercapnic respiratory failure.(31577036)

timing of tracheostomy

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See Also

Weaning from mechanical ventilation using pressure support or a T-tube for a spontaneous breathing trial

• For patients who are persistently unable to be extubated, tracheostomy should be considered (typically within a time frame of 1-2 weeks post intubation).
• Studies comparing early versus late tracheostomy have not found any universal answer to this question. Therefore, the timing of tracheostomy may be best individualized based on the patient's expected trajectory:
  • If the patient has a disease process that is chronic or associated with a prolonged recovery time (e.g., obesity hypoventilation syndrome or stroke), then earlier tracheostomy may make sense.
  • If the disease process may improve over a subacute time frame (e.g., pneumonia), then delaying tracheostomy may make sense.

unplanned extubation

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unplanned extubation falls into two categories:

• (#1) Endotracheal tube is pulled out inadvertently (e.g., while turning or transporting the patient). This will generally require reintubation.
• (#2) Patient intentionally removes their own endotracheal tube (self-extubation).

self-extubation

• Patients who self-extubate are awake and strong enough to overcome restraints in order to remove the endotracheal tube. These factors suggest that they may be ready to breathe independently. Indeed, about half of patients who self-extubate will not require reintubation.
• A general approach to the patient who has self-extubated (assuming the patient isn't in immediate need of reintubation):
  • Stop all sedative infusions.
  • Place the patient on BiPAP.
  • Observe.
  • Reintubate if clinically indicated (while recognizing that most patients may not actually require reintubation).

nocturnal extubation

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• It has been debated whether patients should be extubated at night, or whether extubation should be deferred to the following morning.
• Attempts to study this phenomenon are futile, because it is a context-sensitive intervention. The safety and advisability of nocturnal extubation will vary widely, depending on patient-specific factors as well as context-sensitive factors (e.g., availability of personnel capable of intubating the patient at night).
• Decisions regarding the optimal time to extubate any specific patient must be individualized.
• More discussion of nocturnal extubation here.

understanding and navigating the obesity quagmire

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understanding the obesity quagmire

• Generally, if someone is intubated unnecessarily then they should be easy to extubate. However, this may not be the case for patients with morbid obesity.
• Morbid obesity (especially severe truncal obesity) causes restriction to diaphragm expansion, which is much more severe when patients are lying supine. For this reason, patients with severe obesity may often have difficulty lying flat even at baseline (and in some cases patients may never lie down flat, but rather may sleep in a chair).
• If a patient with severe obesity is intubated and placed in a supine position, this may lead to severe pulmonary restriction and an inability to be extubated using standard protocols – even if there is no acute pulmonary disease process! The patient's physiology is essentially incompatible with conventional mechanical ventilation (i.e., lying semi-supine with a PEEP of 5-8 cm).

patients with morbid obesity generally require higher levels of PEEP

• Patients with severe morbid obesity will often need substantial amounts of PEEP when lying supine, to counteract the effect of abdominal restriction (e.g., 25 cm +/- 5 cm in one study!).(33797429)
• Transesophageal balloon measurement of esophageal pressures may be used to avoid inadequate use of PEEP. However, these are difficult to place and not widely available.
• Measurement of intraabdominal compartment pressure (e.g., using a Foley catheter) could represent one approach to gain a rough concept of how much PEEP might be required. If the PEEP is substantially lower than the intraabdominal compartment pressure, this may promote derecruitment and increased work of breathing.
• Unfortunately, the optimal PEEP for patients with elevated abdominal pressures remains unknown.(31025221) Increasing the PEEP may increase the intraabdominal pressure, which could threaten to worsen intraabdominal compartment syndrome (e.g., with worsening renal and hemodynamic function). Monitoring the effect of PEEP on intraabdominal pressure could theoretically help avoid this.(32166639)

continuation of elevated levels of PEEP throughout the weaning process

• Patients with severe morbid obesity may be weaned and extubated despite the use of high PEEP levels, provided that they are otherwise ready for extubation. It's important to recognize this, because such patients may never be able to achieve a low enough PEEP to qualify for traditional weaning protocols (which demand a PEEP of 5-8 cm, prior to weaning).
• Following extubation:
  • (1) The patient may be immediately placed on CPAP to maintain recruitment and replace the high PEEP level (or BiPAP with a high expiratory airway pressure, which similarly establishes a high mean airway pressure). Positive airway pressure may be gradually weaned off over time, although CPAP or BiPAP may often continue to be beneficial at night.
  • (2) The patient should be nursed in a seated position, or a reverse Trendelenburg position (to reduce pressure on the diaphragm from the abdomen).
• Patients with severe obesity who develop derecruitment may respond well to airway pressure release ventilation (APRV), as a strategy for both lung recruitment and maintenance of open lungs.

bad ideas in ventilator weaning

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gradual weaning of the amount of ventilator support

• Historically, a common strategy for ventilator weaning was to gradually reduce the amount of support provided by the ventilator. This is currently not preferred for most patients, because it risks exposing patients to inadequate levels of ventilator support for prolonged periods of time (which may cause severe diaphragmatic fatigue that persists for 1-2 days).
• The best strategy for weaning most patients off ventilation is rather to provide a full level of support, which is interrupted by spontaneous breathing trials. Patients who aren't ready for extubation following a spontaneous breathing trial should be returned to a full level of ventilator support. This avoids diaphragmatic fatigue.
• The concept of gradually weaning ventilator support may occasionally be useful for patients who are undergoing very gradual ventilator weaning status post tracheostomy (but not for weaning most patients).

resumption of ventilator support following a successful spontaneous breathing trial

• A T-piece trial involves the elimination of all support, such that the patient is effectively breathing through the endotracheal tube like a straw. This is suboptimal for the following reasons:
  • (1) The trial is too strenuous, potentially causing diaphragmatic fatigue (especially if prolonged beyond 30 minutes).
  • (2) A T-piece trial doesn't allow for monitoring of tidal volume or end tidal CO2.
• Some evidence reveals that after a T-piece trial, reconnection to the ventilator to rest the patient prior to extubation may improve extubation success.(28936675) This data illuminates the underlying truth that the T-piece trial is excessively strenuous. The best approach is arguably to avoid T-piece trials altogether (rather than to attempt to compensate for an overly difficult test by resting the patient prior to extubation).
  • The goal of a spontaneous breathing trial is to mimic the work of breathing without an endotracheal tube. If a period of rest is needed after the spontaneous breathing trial, this proves that the spontaneous breathing trial itself is excessively difficult.

p0.1

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• p0.1 is a measurement of airway occlusion pressure 100 ms (0.1 seconds) after the onset of inspiration. It can be checked easily and reliably using modern ventilators (although some sources suggest taking an average of three measurements to eliminate breath-to-breath variability).
• p0.1 is a measurement of respiratory effort (aka, work of breathing):
  • p0.1 <1 cm suggests low respiratory effort.
  • p0.1 >4 cm suggests excessively high respiratory effort. (38436722) This may be associated with dyspnea, diaphragmatic fatigue, and difficult weaning from ventilation. (38484187)
• One meta-analysis found that a p0.1 below ~3.5-4.5 had a sensitivity of 86% and specificity of 58% for predicting successful weaning. (33012587)

questions & discussion

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To keep this page small and fast, questions & discussion about this post can be found on another page here.

• Performing a spontaneous breathing trial when the patient is deeply sedated.
• Assuming that an apnea event during the spontaneous breathing trial or lack of cuff leak indicates that the patient cannot be extubated.
• Leaving patients on a spontaneous breathing trial indefinitely, due to inability to make a decision.
• If a patient fails a spontaneous breathing trial, failure to investigate why.

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