Use of Endotracheal Tube Cuff Pressure to Assess Inspiratory Effort During Pressure Support Ventilation

Use of Endotracheal Tube Cuff Pressure to Assess Inspiratory Effort During Pressure Support Ventilation: a Prospective Physiological Study

During pressure support ventilation (PSV), monitoring of Esophageal Pressure (Pes) has long been considered the gold standard for assessing intrathoracic pressure and the state of respiratory mechanics.The aim of this study was to investigate the correlation between Cuff Pressure (Pcuff) and Esophageal Pressure in patients undergoing tracheal intubation or tracheotomy, and to assess whether Pcuff can be used as a surrogate for Pes for reflecting changes in intrathoracic pressure.The correlation and its consistency between the two under different ventilation conditions were analysed by synchronously monitoring the ΔPcuff and ΔPes to further validate the potential application value of cuff pressure in clinical practice.The results of the study will provide a more convenient and non-invasive method of monitoring intrathoracic pressure in mechanically ventilated patients, thus optimising ventilation strategies, reducing complications, and promoting the innovation and development of monitoring technology in the field of critical care medicine.

Monitoring of Esophageal pressure (Pes) has long been regarded as the gold standard for assessing intrathoracic pressure and respiratory mechanics. The measurement of Esophageal pressure provides indirect information about pleural pressure, which is critical for understanding respiratory mechanics, optimizing mechanical ventilation strategies, and evaluating respiratory muscle load.

However, despite its clinical significance, Esophageal pressure monitoring involves a relatively complex and invasive procedure. Measurement typically requires the insertion of an esophageal catheter via the nasopharyngeal or oropharyngeal route, which may cause patient discomfort and prove challenging in certain cases (e.g., esophageal pathologies or anatomical abnormalities). Consequently, while esophageal pressure remains the current gold standard for evaluating intrathoracic pressure, its clinical application faces limitations.

In contrast, Cuff pressure (Pcuff) monitoring in intubated or tracheostomized patients is simpler and routinely performed. Cuff pressure measurement primarily ensures tracheal tube sealing to prevent gas leakage and aspiration, while also reducing the risk of ventilator-associated pneumonia (VAP). Our preliminary exploratory studies have revealed correlations between Cuff pressure fluctuations and Esophageal pressure, particularly in patients undergoing pressure support ventilation. This finding suggests the potential utility of Cuff pressure as a surrogate marker for intrathoracic pressure. Esophageal pressure inherently reflects pleural pressure through Esophageal pressure changes, while the artificial airway cuff-positioned above the carina within the trachea-detects subtle pressure variations induced by adjacent muscle activity during forceful breathing. These measurements may indirectly indicate inspiratory effort. Variations in cuff positioning might influence results, and our exploratory attempts demonstrated strong waveform correlations between Cuff pressure and Esophageal pressure.

Inclusion Criteria:

1. Mechanically ventilated patients who can tolerate pressure support ventilation (PSV) mode;
2. Respiratory stability: Ability to breathe spontaneously and effectively clear secretions via coughing; oxygen saturation (SpO₂) >90% or a partial pressure of oxygen (PaO₂)/FiO₂ ratio ≥150 mmHg when the ventilator's oxygen concentration is set to 40%;
3. Hemodynamic stability: Heart rate (HR) ≤120 bpm, systolic blood pressure (SBP) 90-150 mmHg, with no vasoactive agents or norepinephrine dosage ≤0.1-0.2 μg/kg·min (or equivalent doses of other vasoactive agents);
4. Metabolic stability, with an esophageal pressure monitoring catheter already placed prior to the trial;
5. Written informed consent obtained from the patient or their legal guardian.

Exclusion Criteria:

1. Age <18 years;
2. Pregnancy;
3. Hemodynamic instability: Mean arterial pressure (MAP) <60 mmHg, heart rate (HR) >120 bpm or <60 bpm;
4. Respiratory instability: Respiratory rate (RR) >35 bpm or oxygen saturation (SpO₂) <90%;
5. Neuromuscular disorders or phrenic nerve injury;
6. Recent trauma or surgery involving the trachea, esophagus, neck, or thorax, contraindications to esophageal catheter insertion, or inability to monitor esophageal pressure;
7. High bleeding risk: Severe coagulopathy/bleeding disorders, esophageal/gastric varices, etc.