Incremental Dead Space Versus Capping Trial Before Tracheostomy Decannulation

Approximately 10-15% of mechanically ventilated intensive care unit (ICU) patients require prolonged mechanical ventilation, and tracheostomy is frequently used to facilitate weaning and respiratory rehabilitation in this population. Tracheostomy decannulation is a key recovery milestone, but there is no standardized method for confirming readiness. The tracheostomy capping trial, in which the tube is occluded to redirect airflow through the upper airway, is the most widely used final assessment prior to decannulation; however, because the tracheostomy tube remains in place, it substantially narrows the airway lumen and may increase airflow resistance up to 16-fold compared to true post-decannulation breathing (per Poiseuille's law). This supraphysiological load may cause capping trial failure in patients who would otherwise tolerate decannulation, particularly those with pre-existing respiratory muscle weakness related to ICU-acquired weakness, which affects up to 80% of patients requiring prolonged mechanical ventilation.

Preliminary physiological data from the investigators' group (unpublished) demonstrated that the esophageal pressure-time product (PTP), a validated marker of the work of breathing, increased by 226% during capping trials compared to baseline, then decreased after actual decannulation to levels close to baseline, suggesting the capping trial substantially overestimates the respiratory burden that patients will face after tube removal.

This study proposes an alternative physiological assessment using incremental instrumental dead space, which reproduces the anatomical dead space increase that occurs after decannulation without imposing the artificial airway resistance created by the tracheostomy tube during capping. In a randomized crossover design, each participant will undergo both the capping trial and the incremental dead space strategy in random order, followed by assessment after actual decannulation, allowing within-participant comparison of which method better predicts the true post-decannulation respiratory status.

Inclusion criteria

• Adult patients (≥18 years) admitted to the ICU.
• Presence of a tracheostomy due to prolonged mechanical ventilation (≥14 days).
• Clinically considered ready for decannulation, according to institutional criteria (e.g., stable gas exchange, minimal secretions, effective cough, and tolerance to spontaneous breathing).
• Ability to maintain spontaneous breathing without mechanical ventilation for more than 48 consecutive hours.
• Able to cooperate and follow basic commands (RASS between -1 and +1).
• Written informed consent obtained from patient.

Exclusion criteria

• Neuromuscular disease affecting respiratory muscles (e.g., myasthenia gravis, Guillain-Barre syndrome, amyotrophic lateral sclerosis).
• Hemodynamic instability.
• Severe agitation or delirium precluding cooperation (RASS < -2 or > +2).
• Structural airway abnormalities (e.g., subglottic stenosis, tracheomalacia).
• Pregnancy.
• Contraindications for esophageal balloon catheter insertion (e.g., severe coagulopathy, esophageal varices, and history of esophageal or gastric surgery).
• Refusal to participate by the attending physician.