Weaning, Discontinuation & Module Exam

Objectives — Change the patient-ventilator circuit following AARC guidelines; transport mechanically ventilated patients safely; initiate procedures for discontinuing mechanical ventilation including SBT and extubation criteria.

---

Ventilator-Associated Pneumonia (VAP)

Definition

Pneumonia occurring more than 48–72 hours after intubation and mechanical ventilation.

VAP Prevention Protocols

---

Circuit Change — AARC Guidelines

Recommendation #1

Do not change ventilator circuits routinely for infection control. Evidence shows no patient harm and considerable cost savings with extended circuit change intervals. Maximum safe duration is unknown — change when visibly soiled or mechanically malfunctioning.

Recommendation #2

Avoid excessive condensate accumulation. Take care not to drain condensate toward the patient's airway, and avoid contaminating caregivers during disconnection.

Recommendation #3

Passive humidification (HME) versus active humidification — while some evidence favors HME for VAP rates, other issues (resistance, dead space, airway occlusion risk) preclude a blanket recommendation for HMEs.

Recommendation #4

HMEs do not need to be changed daily. They can be used safely for at least 48 hours; some devices up to 1 week with certain patient populations.

Recommendation #5

Closed suction catheters do not need to be changed daily for infection control. Maximum safe duration is unknown.

Recommendation #6

Clinicians should be aware of VAP risk factors: nebulizer therapy, manual ventilation, and patient transport.

Circuit Change Procedure

Equipment needed: BVM, new circuit, large-bore corrugated tubing, proximal flow transducer, inspiratory and expiratory filters, humidifier or HME, sterile distilled water, closed suction catheter, aerosol treatment devices, water traps.

Steps:

1. Set up and confirm proper function of manual resuscitator
2. Bypass ventilator circuit from humidifier
3. Remove and replace sterile humidifier
4. Fill humidifier with sterile distilled water
5. Deactivate / silence ventilator alarms; reassure patient
6. Remove old circuit and replace with new circuit during exhalation
7. Check system for leaks
8. Confirm all parameters of ventilation
9. Assess patient — physical assessment, vital signs, airway
10. Reset and verify all alarm functions/settings
11. Reassure patient
12. Dispose of old circuit
13. Document circuit change

---

Definitions

It is occasionally important to distinguish: a patient may need to be liberated from the ventilator but still need a protected airway (e.g., upper airway edema, secretion management).

---

Weaning Timelines

---

Weaning Factors

Success depends on four factors:

1. Ventilatory workload vs. capacity — Is the disease load decreasing? Are the muscles recovering?
2. Oxygenation status — Is gas exchange adequate at reduced support?
3. Cardiovascular function — Is the patient hemodynamically stable?
4. Psychological factors — Fear, anxiety, depression, ICU psychosis

ICU Psychosis: Acute brain failure from dehydration, hypoxia, heart failure, infection, or drugs. Manifests as anxiety, paranoia, disorientation, and agitation.

---

Evaluating a Patient for Weaning

Before initiating weaning, confirm:

• Evidence of improvement or reversal of the underlying cause of respiratory failure
• Oxygenation status is adequate
• Patient is hemodynamically stable
• Patient can breathe spontaneously

Preparing the Patient

• Minimize disease-imposed ventilatory load (treat bronchospasm, secretions, infections)
• Ensure patient is rested
• Address psychological and communication needs (ICU psychosis, sedation, communication tools)
• Lift sedatives and narcotics before assessment

---

Weaning / Discontinuation Parameters

Caution: Over-reliance on weaning parameters may result in unnecessarily prolonged ventilator dependency. Use parameters as a guide, not as a checklist that must all be met.

Oxygenation Parameters

Ventilation Parameters

Ventilatory Mechanics

Respiratory Muscle Strength

Ventilatory Drive / Demand

P0.1: Inspiratory pressure measured 100 milliseconds after airway occlusion. Effort-independent and predicts weaning difficulty better than effort-dependent parameters. P0.1 > 6 cmH₂O suggests difficult weaning.

---

RSBI — Rapid Shallow Breathing Index

Also called Tobin's Index.

RSBI = RR / Vt (in liters)

How to measure:

• Place patient on spontaneous mode (CPAP)
• Set PEEP = 0 cmH₂O and PS = 0 cmH₂O
• Collect data after one minute
• Calculate: RSBI = RR ÷ Vt (convert Vt to liters)

Interpretation:

Examples (all with 6 L/min minute volume):

Note: A normal minute volume does not guarantee weaning success — RSBI captures the rapid shallow breathing pattern that minute volume alone misses.

---

Weaning Methods

1. SIMV Weaning

• Gradually reduce mandatory rate until 4–6 breaths/min
• Assess tolerance with ABG, vital signs, patient appearance
• If tolerated → perform SBT and consider extubation
• Slowest and least aggressive method

2. Pressure Support Ventilation (PSV) Weaning

Advantages over T-piece SBT:

• Apnea backup is maintained
• Full alarms active
• Monitored ventilator data available
• Circuit never broken

3. Spontaneous Breathing Trial (SBT)

One of several methods to assess a patient's ability to breathe with minimal or no ventilator support.

• Performed multiple times per day, interspersed with periods of full support
• Can last minutes to hours, extended gradually based on response
• Faster than SIMV for discontinuing ventilatory support
• Successful SBT should prompt consideration for extubation

---

Types of SBT

T-Piece Trial (Oldest Method)

Patient is removed from the ventilator and placed on humidified supplemental oxygen via large volume nebulizer with a T-piece adaptor or trach collar.

Disadvantages:

• Requires extra equipment
• Breaks the circuit
• No apnea backup or alarms

CPAP SBT (Preferred Method)

Patient remains on the ventilator in CPAP mode:

• CPAP = 0 cmH₂O
• PS = 0 cmH₂O
• Flow triggering

Advantages:

• No extra equipment
• Circuit is not broken
• Full apnea backup and alarms
• Easy airway suctioning access

---

Criteria for FAILING an SBT

Stop the SBT if any of the following occur:

---

Causes of SBT Failure

After SBT Failure

1. Promptly reestablish ventilatory support
2. Identify and correct the reason for failure
3. Allow the patient to rest on full support for several hours before the next SBT
4. Ventilator weaning protocols (RT-driven) improve outcomes when systematically applied

---

Terminal Weaning

Discontinuing mechanical ventilation in the context of a catastrophic illness with no expectation of survival.

• Decision made by the family with MD consultation
• Patient comfort is the priority
• Pharmacologic support: morphine or fentanyl (pain), midazolam or lorazepam (anxiety)
• Terminal weaning should be performed in a humane, compassionate manner

---

Brain Death

Causes

• Prolonged cardiac arrest
• Massive stroke
• Brain infection or tumor

Clinical Evaluation (Neurologist / Critical Care MD)

Absence of all brainstem reflexes must be confirmed:

EEG may also be used to confirm absence of electrical brain activity.

Apnea Test

Performed if brainstem reflexes are absent. Confirms the absence of brainstem-driven respiratory effort.

Pre-test requirements:

• Compensated ABG:
  • PaCO₂ 35–40 mmHg
  • PaO₂ 200 mmHg

Procedure:

1. Disconnect patient from the ventilator
2. Deliver 100% O₂ via a catheter placed at the carina at 4–6 L/min (apneic oxygenation)
3. Watch for spontaneous chest rise for 8–10 minutes

Interpreting Results:

After the test, return patient to full ventilation and document findings.