A novel technique for assessment of post-extubation airway obstruction can successfully replace the conventional cuff leak test: a pilot study

Abstract

Background: Post-extubation airway obstruction is an important complication of tracheal intubation. The cuff leak test is traditionally used to estimate the risk of this complication. However, the cuff leak test parameters are not constant and may depend on the respiratory system and ventilator settings. Furthermore, deflating the cuff also be a risk factor for patient-ventilator asynchrony and ventilator-associated pneumonia. Instead of using the cuff leak test, we measured the pressure of the leak to the upper airway through the gap between the tube and glottis with a constant low flow from the lumen above the cuff without deflating the cuff and called it "pressure above the cuff." The purpose of this study was to investigate whether pressure above the cuff can be used as an alternative to the cuff leak volume.

Methods: This prospective observational study was conducted at Kumamoto University Hospital after obtaining approval from the institutional review board. The pressure above the cuff was measured using an endotracheal tube with an evacuation lumen above the cuff and an automated cuff pressure modulation device. We pumped 0.16 L per minute of air and measured the steady-state pressure using an automated cuff pressure modulation device. Then, the cuff leak test was performed, and the cuff leak volume was recorded. The cuff leak volume was defined as the difference between the expiratory tidal volume with the cuff inflated and deflated. The relationship between the pressure above the cuff and cuff leak volume was evaluated. The patient-ventilator asynchrony during each measurement was also examined.

Results: The pressure above the cuff was measured, and the cuff leak volume was assessed 27 times. The pressure above the cuff was significantly correlated with the cuff leak volume (r = -0.76, p < 0.001). Patient-ventilator asynchrony was detected in 37% of measurements during the cuff leak test, but not during the pressure above the cuff test.

Conclusions: This study suggests that pressure above the cuff measurement may be a less complicated alternative to the conventional cuff leak test for evaluation of the risk of post-extubation airway obstruction.

Trial registration: University Hospital Medical Information Network Clinical Trials Registry (UMIN000039987; March 30, 2020). https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000044604.

Keywords: Cuff leak test; Intensive care; Patient-ventilator asynchrony; Post-extubation edema; Post-extubation stridor.

Fig. 1

Schema of the above-cuff leak test. The smaller number at the bottom of the screen of the automated cuff pressure modulation device is the set pressure, and the larger number is the value of the measured pressure. Air (⇢) is delivered from the automated cuff pressure modulation device through the evacuation line to the subglottic evacuation port. Then, the air flow leaks to the upper airway through the gap between the tube and the glottis with an intact upper airway (A). At that time, the measured pressure became smaller than the set pressure. If there was upper airway obstruction, such as laryngeal edema, the air flow did not leak into the upper airway and the set and measured pressures were equal (B)

Fig. 2

Graphical examples of patient-ventilator asynchrony. Airway pressure (top), flow (middle), and volume (bottom) waveforms over time during volume-assisted control ventilation. The respiratory rate and tidal volume were set to 15 breaths/min and 500 mL, respectively. A With the cuff deflating, the expiratory tidal volume (VTe) was lower than the inspiratory tidal volume (VTi). The expiratory volume waveforms fall and then plateau without reaching zero (arrows); B All cycles occurring at a respiratory rate of 17 breaths/min, which exceeds the set frequency, were auto-triggered due to circuit leakage

Fig. 3

Correlations between pressure above the cuff and cuff leak volume

Fig. 4

Relationship between auscultation cuff leak test and pressure above the cuff test p < 0.01