4.6 Weaning, Emergencies, and Special Procedures

Weaning Readiness

Weaning begins once the reason for ventilation is reversing. TMC items look for stable oxygenation (typically PaO2/FiO2 acceptable, FiO2 at or below about 0.40-0.50, PEEP at or below 5-8 cmH2O), stable hemodynamics off escalating vasopressors, a manageable secretion load, an adequate cough, acceptable mental status, and enough respiratory muscle strength. Readiness is never one number: a patient with fine oxygenation can still fail from agitation, fever, shock, acidemia, a weak cough, or copious secretions, so combine objective data with bedside tolerance.

Readiness and Trial Table

Spontaneous Breathing Trials

A spontaneous breathing trial (SBT) uses low pressure support, CPAP, or a T-piece for about 30-120 minutes. The rapid shallow breathing index (RSBI) = respiratory rate / tidal volume in liters; for example a rate of 30 with a 300 mL (0.3 L) tidal volume gives 100, which is borderline favorable (below the classic 105 threshold). During the trial watch respiratory rate, tidal volume, SpO2, heart rate, blood pressure, accessory-muscle use, diaphoresis, anxiety, and mental status. A patient who turns tachypneic, diaphoretic, hypoxemic, or unstable should be returned to support and evaluated for the cause; do not force a harder trial.

From SBT Pass to Safe Extubation

Passing an SBT is not the same as being safe to extubate. The patient must protect the airway, clear secretions, and maintain upper-airway patency.

• Airway-protection red flags: absent gag or cough, frequent thick secretions, severe weakness, or declining mental status.
• Cuff-leak test: absence of an audible leak when the cuff is deflated suggests laryngeal edema and post-extubation stridor risk.
• Post-extubation stridor is managed with close monitoring and ordered therapies such as racemic epinephrine and corticosteroids; noninvasive ventilation may help selected high-risk patients but must never delay reintubation when airway protection is failing.

Emergency Deterioration

When a ventilated patient suddenly worsens, do not start with small routine setting changes. Assess airway, breathing, circulation, and the circuit. If the patient is unstable and the airway or ventilator is suspect, disconnect and manually ventilate with 100% oxygen by bag while the cause is found. Use DOPE: Displacement, Obstruction, Pneumothorax, Equipment failure. A low-pressure alarm usually means disconnection or leak; a high-pressure alarm means obstruction, biting, secretions, bronchospasm, falling compliance, or a kink.

A tension pneumothorax pattern — sudden hypoxemia, hypotension, unilateral absent breath sounds, tracheal shift, and high pressure — demands immediate manual ventilation, a call for help, and decompression.

Special Procedures and Transport

Transport requires enough oxygen for the trip plus reserve, a charged ventilator battery, working alarms, a manual resuscitation bag, airway and suction supplies, and continuous monitoring. Define a stop point before any procedure: worsening hypoxemia, hypotension, arrhythmia, loss of airway, or inability to ventilate should interrupt bronchoscopy, transport, or a trial until the patient is stabilized. Routine optimization always waits when oxygenation, ventilation, circulation, or equipment integrity is threatened.

Weaning Modification After a Failed Trial

When an SBT fails, the exam never rewards an automatic harder trial or immediate extubation. Instead, restore comfortable support, rest the patient, and name the physiologic reason for failure. A failure from rapid shallow breathing with a low tidal volume points to fatigue or excess load — investigate bronchospasm, secretions, pain, anxiety, fluid overload, or cardiac dysfunction, since weaning-induced cardiac ischemia and pulmonary edema are well-described causes. A failure from desaturation points back to FiO2, PEEP, atelectasis, fluid status, or secretion burden.

A failure from a rising PaCO2 points to inadequate strength or drive against the load. Repeated immediate trials without recovery only deepen fatigue and make the next assessment less reliable, so the safest answer corrects reversible causes first and trials again the next day.

Chest Tube and Drainage Troubleshooting

Chest-tube scenarios test pattern recognition in the water-seal system. Continuous bubbling in the water-seal chamber signals an air leak; trace it from the patient toward the system by briefly clamping at successive points (per policy) to localize whether the leak is at the insertion site, a loose connection, or within the lung itself.

Tidaling — the water level rising and falling with respiration — is normal and reflects intrapleural pressure swings; its absence means either the lung has fully re-expanded or the tube is obstructed, kinked, or clamped, so the exam expects you to check tube patency and confirm re-expansion with a film. Never clamp a chest tube with an ongoing air leak in a ventilated or spontaneously breathing patient, because trapped air can build a tension pneumothorax. If the drainage system tips over or the collection chamber cracks, keep the tube below chest level and re-establish a water seal promptly.

Transport and Code Readiness Checklist

For any ventilated transport, verify enough oxygen for the trip plus a reserve (calculate cylinder duration from tank pressure and flow), a charged battery, functioning alarms, a manual resuscitation bag attached to oxygen, suction, airway exchange supplies, and continuous pulse oximetry and cardiac monitoring. In a code, the respiratory therapist secures the airway and ventilation, supports high-quality compressions, and prepares for defibrillation when the rhythm is ventricular fibrillation or pulseless ventricular tachycardia.

Throughout, the recurring exam principle holds: stabilize the immediate airway, breathing, and circulation threat before any routine setting optimization.