Sound analysis in an in vitro endotracheal tube model

Ex Vivo Evaluation of Secretion-Clearing Device in Reducing Airway Resistance within Endotracheal Tubes

Background

Secretions accumulate in endotracheal tubes' (ETT) lumens upon their placement in patients. The secretions impact airway resistance and pressure. Secretions potentiate prolonged mechanical ventilation and ventilator-associated pneumonia. Our primary objective in this study was to evaluate an ETT-clearing device (ETT-CD) in its ability to remove secretions from ex vivo ETT lumens.

Methods

Forty ETTs, obtained from intensive care patients at extubation, were individually placed into a ventilator field performance testing simulator at 37°C. The pressure drop through the ETTs was measured at a flow rate of 60 L/min before and after cleaning with the ETT-CD and compared with unused, similarly sized controls tubes. The ETT-CD was inserted into an ETT until the tip reached Murphy's eye (hole in the side) of the ETT. The wiper, set back from the tip, was expanded by ETT-CD handle activation. As the ETT-CD was removed, the distal wiper extracted secretions from the ETT lumen.

Results

Forty ETTs were tested with nonparametric Wilcoxon signed-rank tests. Before being cleared with the ETT-CD, the median pressure drop in the extubated 7.5 mm ETTs was 17.8 cm H₂O; after ETT-CD use, it was 12.3. The cleared ETTs were significantly improved over the ETTs before being cleared (p < 0.001); however, there remained a significant difference between the cleared ETTs and the control tubes (p=0.005), indicating the clearing was not to the level of an unused ETT. Similar results were determined for the 8.0 mm ETTs.

Conclusions

For the 7.5 mm and the 8.0 mm EETs, the ETT-CD improved effective patency of the ETTs over the uncleared ETTs, independent of occlusion location, tube size, or length of tube. However, there remained a significant difference between the cleared tubes and controls.

Sound level analysis in endotracheal tube obstruction in spontaneous breathing and mechanical ventilation-an animal model study

Endotracheal tube (ETT) obstruction, either complete or partial, is a serious life threatening complication in intubated patients. Therefore, implementing a practical method to diagnose this condition is vital. Alteration in respiratory sound signals caused by ETT occlusion can be used for early detection of obstruction. This study is aimed to assess changes in respiratory sound signals after creation of different types of tubal obstruction in an animal model experiment. Artificial internal obstructions were created in three different sizes and three different locations by stitching pieces of smaller tubes in ETTs with internal diameter of 8 mm. A microphone was used to record respiratory sounds during both spontaneous breathing and mechanical ventilation in seven anesthetized dogs. The sound intensity levels produced by different grades and degrees of obstructions were measured and compared with those in non-obstructed tubes. During spontaneous breathing, significant decrease in sound intensity level was detected even with the lowest grades of obstruction (p = 0.003, 0.001, and 0.002, proximal, middle and distal obstructions, respectively). However, in mechanical ventilation, significant decrease in sound intensity was observed only in distal tubal obstruction (p = 0.037). The difference among levels of sound intensity produced by different obstruction locations of occlusion was not statistically significant (p ≥ 0.090). Data analysis revealed that sound intensity level decreased significantly when the degree of obstruction increased. In addition, this change in sound level was not related to the location of obstruction. The decrease in sound intensity changes can be used to detect ETT obstruction. However, further studies are needed for clinical application.

Effect of nebulized eucalyptus on contamination of microbial plaque of endotracheal tube in ventilated patients

Background:

Formation of biofilm and bacterial colonization within the endotracheal tube (ETT) are significant sources of airway contamination and play a role in the development of ventilator-associated pneumonia (VAP). This study was conducted to examine the effect of nebulized eucalyptus (NE) on bacterial colonization of ETT biofilm.

Materials and Methods:

We performed a randomized clinical trial in three intensive care units (ICUs) of an educational hospital. Seventy intubated patients were selected and randomly divided into intervention (n = 35) and control (n = 35) groups. The intervention group received 4 ml (5%) of eucalyptus in 6 ml normal saline every 8 h. The placebo group received only 10 ml of normal saline in the same way. On extubation, the interior of the tube was immediately sampled using a sterile swab for standard microbiological analysis. Chi-square and Fisher's exact tests were used for statistical analysis in SPSS. P values less than 0.05 were considered statistically significant.

Results:

In both samples, Klebsiella pneumoniae and Acinetobacter baumannii were the most frequently isolated bacteria. In the control group, heavy colonization was greater than in the intervention group (P = 0.002). The frequency of isolation of K. pneumoniae in the intervention group was lower than in the control group (P < 0.001). However, there was no difference between the two groups in other isolated bacteria.

Conclusions:

NE can reduce microbial contamination of the endotracheal tube biofilm in ventilated patients. Moreover, K. pneumoniae was the most sensitive to NE.