Endotracheal tube narrowing after closed-system suctioning: prevalence and risk factors

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.

Can ventilator settings reduce the negative effects of endotracheal suctioning? Investigations in a mechanical lung model

Background

The insertion of suction devices through endotracheal tubes (ETTs) increases airway resistance and the subsequent suctioning may reduce airway pressures and facilitate atelectasis.

The aim of this study was to investigate how airway pressures and tidal volumes change when different combinations of suction equipment and ETT sizes are used, and to what extent unfavorable effects can be ameliorated by choice of ventilator settings.

Methods

A mechanical ventilator was connected to a lung model by ETTs of 9 mm, 8 mm or 7 mm internal diameter (ID) with a pressure transducer inserted distal to the ETT. The effects of suction procedures with bronchoscope and closed catheter systems were investigated during pressure controlled ventilation (PCV) and volume controlled ventilation (VCV). In each mode, the effects of changes in inspiration:expiration (I:E) ratio, trigger sensitivity and suction pressure were examined.

Results

The variables that contributed most to negative model airway pressures and loss of tidal volume during suctioning were (in descending order); 1) Small-size ETTs (7–8 mm ID) combined with large diameter suction devices (14–16 Fr); 2) inverse I:E ratio ventilation (in VCV); 3) negative ventilator trigger sensitivity; and 4) strong suction pressure. The pressure changes observed distal to the ETTs were not identical to those detected by the ventilator.

Conclusions

Negative model airway pressure was induced by suctioning through small-size ETTs. The most extreme pressure and volume changes were ameliorated when conventional ventilator settings were used, such as PCV mode with short inspiration time and a trigger function sensitive to flow changes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-016-0196-z) contains supplementary material, which is available to authorized users.

Tracheal tube obstruction in mechanically ventilated patients assessed by high-resolution computed tomography

BACKGROUND

Tracheal intubation compromises mucus clearance and secretions accumulate inside the tracheal tube (TT). The aim of this study was to evaluate with a novel methodology TT luminal obstruction in critically ill patients.

METHODS

This was a three-phase study: (1) the authors collected 20 TTs at extubation. High-resolution computed tomography (CT) was performed to determine cross-sectional area (CSA) and mucus distribution within the TT; (2) five TTs partially filled with silicone were used to correlate high-resolution CT results and increased airflow resistance; and (3) 20 chest CT scans of intubated patients were reviewed for detection of secretions in ventilated patients' TT.

RESULTS

Postextubation TTs showed a maximum CSA reduction of (mean±SD) 24.9±3.9% (range 3.3 to 71.2%) after a median intubation of 4.5 (interquartile range 2.5 to 6.5) days. CSA progressively decreased from oral to lung end of used TTs. The luminal volume of air was different between used and new TTs for all internal diameters (P<0.01 for new vs. used TTs for all studied internal diameters). The relationship between pressure drop and increasing airflow rates was nonlinear and depended on minimum CSA available to ventilation. Weak correlation was found between TT occlusion and days of intubation (R²=0.352, P=0.006). With standard clinical chest CT scans, 6 of 20 TTs showed measurable secretions with a CSA reduction of 24.0±3.9%.

CONCLUSIONS

TT luminal narrowing is a common finding and correlates with increased airflow resistance. The authors propose high-resolution CT as a novel technique to visualize and quantify secretions collected within the TT lumen.

Respiratory therapy device modifications to prevent ventilator-associated pneumonia

PURPOSE OF REVIEW

Ventilator-associated pneumonia (VAP) is a controversial entity in the field of critical care. After years of research and significant efforts from regulatory agencies and hospitals, this complication is still frequently affecting mechanically ventilated patients, making VAP an active battleground for research. As a result, several preventive measures have recently been tested in experimental and clinical trials. Our interest is focused on those innovations related to the endotracheal tube (ETT).

RECENT FINDINGS

Four ETT-related VAP causative mechanisms are reviewed, together with different associated potential solutions. Technologies such as the subglottic secretion drainage and the Mucus Slurper have been studied to eliminate subglottic secretion pooling. Novel designs for the cuff and the management of its pressure may avoid leakage. Antimicrobial coatings can prevent endoluminal biofilm formation, whereas using an ETT cleaning device may also be beneficial. Finally, preserving the tracheal ciliary function will keep our best physiologic protection active.

SUMMARY

VAP prevention strategies are a continuously evolving field. Being able to identify the most valuable ideas needs a deep understanding of the disease pathophysiology. The role of the ETT is crucial and there is need for our standards of care to improve. This may soon be possible with newer technologies becoming increasingly available to clinicians.

Not-so-trivial pursuit: mechanical ventilation risk reduction

As many as half of critically ill patients require mechanical ventilation. In this article, a program of research focused on reduction of risk associated with mechanical ventilation is reviewed. Airway management practices can have profound effects on outcomes in these patients. How patients are suctioned, types of processes used, effects of suctioning in patients with lung injury, and open versus closed suctioning systems all have been examined to determine best practices. Pneumonia is a common complication of mechanical ventilation (ventilator-associated pneumonia), and use of higher backrest elevations reduces risk of pneumonia, although compliance with such recommendations varies. The studies reviewed here describe backrest elevation practices, factors that affect backrest elevation, and the effect of backrest elevation on ventilator-associated pneumonia. Oral care strategies also have been investigated to determine their effect on ventilator-associated pneumonia. Oral care practices are reported to hold a low care priority, vary widely across care providers, and differ in intubated versus nonintubated patients. However, in several studies, oral applications of chlorhexidine have reduced the occurrence of ventilator-associated pneumonia. Although ventilator patients require sedation, sedation is associated with significant risks. The overall goals of sedation are to provide physiological stability, to maintain ventilator synchrony, and to ensure patients' comfort-although methods to evaluate achievement of these goals are limited. Reducing risks associated with mechanical ventilation in critically ill patients is a complex and interdisciplinary process. Our understanding of the risks associated with mechanical ventilation is constantly changing, but care of these patients must be based on the best evidence.

Bronchoscopic suctioning may cause lung collapse: a lung model and clinical evaluation

OBJECTIVE

To assess lung volume changes during and after bronchoscopic suctioning during volume or pressure-controlled ventilation (VCV or PCV).

DESIGN

Bench test and patient study.

PARTICIPANTS

Ventilator-treated acute lung injury (ALI) patients.

SETTING

University research laboratory and general adult intensive care unit of a university hospital.

INTERVENTIONS

Bronchoscopic suctioning with a 12 or 16 Fr bronchoscope during VCV or PCV.

MEASUREMENTS AND RESULTS

Suction flow at vacuum levels of -20 to -80 kPa was measured with a Timeter(trade mark) instrument. In a water-filled lung model, airway pressure, functional residual capacity (FRC) and tidal volume were measured during bronchoscopic suctioning. In 13 ICU patients, a 16 Fr bronchoscope was inserted into the left or the right main bronchus during VCV or PCV and suctioning was performed. Ventilation was monitored with electric impedance tomography (EIT) and FRC with a modified N(2) washout/in technique. Airway pressure was measured via a pressure line in the endotracheal tube. Suction flow through the 16 Fr bronchoscope was 5 l/min at a vacuum level of -20 kPa and 17 l/min at -80 kPa. Derecruitment was pronounced during suctioning and FRC decreased with -479+/-472 ml, P<0.001.

CONCLUSIONS

Suction flow through the bronchoscope at the vacuum levels commonly used is well above minute ventilation in most ALI patients. The ventilator was unable to deliver enough volume in either VCV or PCV to maintain FRC and tracheal pressure decreased below atmospheric pressure.

Tracheal pressure regulated volume assist ventilation in acute respiratory failure

PURPOSE

Proportional assist ventilation (PAV) uses volume assist (VAV) and flow assist ventilation (FAV) to reduce elastic and resistive effort, respectively. Proportional assist ventilation may be difficult to apply clinically, particularly due to FAV related considerations. It was hypothesized that regulating tracheal (Ptr) rather than airway opening pressure (Pao), to overcome endotracheal tube related resistive effort, during VAV would provide an effective alternative method of ventilation. We therefore compared the effects of Pao and Ptr regulated VAV on breathing pattern and inspiratory effort.

METHODS

In seven intubated patients, flow, volume, Pao, Ptr, esophageal and transdiaphragmatic pressure were measured during VAV (0-80% respiratory system elastance) using Pao vs Ptr to regulate ventilator applied pressure. Breathing pattern and the pressure-time integral of the inspiratory muscles (integralP(mus) . dt) and diaphragm (integralP(di) . dt) were determined.

RESULTS

Compared to spontaneous breathing, the respiratory rate to tidal volume ratio, or rapid shallow breathing index (RSBI), improved progressively with increasing VAV (130 +/- 64 vs 70 +/- 35, VAV 0 vs 80%; P < 0.05) while inspiratory effort fell (integralP(mus) . dt = 39.6 +/- 7.5 vs 28.5 +/- 7.2 cm H(2)O.sec.L(-1), integralP(di) . dt, = 35.4 +/- 7.8 vs 24.2 +/- 5.9 cm H(2)O.sec.L(-1), VAV 0 vs 80%; P < 0.05) due to a decrease in elastic related effort. At any given level of support, there was further reduction in RSBI, integralP(mus) . dt, and integralP(di) . dt (which averaged 23.6 +/- 2.7, 33.7 +/- 4.4, and 38.5 +/- 5.1%, respectively; P < 0.05) for Ptr compared to Pao regulated VAV due to a decrease in resistive effort.

CONCLUSIONS

Tracheal pressure regulated VAV can be a simple and effective method of partial ventilatory support in acute respiratory failure. Further work will be needed to determine its efficacy and potential benefit relative to PAV and other modes of ventilation in routine clinical practice.

A comparison of the effectiveness of open and closed endotracheal suction

OBJECTIVE

To compare the effectiveness of open and closed endotracheal suction in recovering thin and thick secretions in normal and injured lungs during conventional and high frequency ventilation.

DESIGN AND SETTING

Randomised study in a paediatric intensive care model in the animal research laboratory of a tertiary paediatric hospital.

SUBJECTS

16 New Zealand White rabbits.

INTERVENTIONS

Anaesthetised animals were intubated with a 3.5-mm endotracheal tube. Simulated thin and thick secretions (iopamidol 2 ml, a watery radio-opaque fluid, and fluorescent mucin 1 ml) were instilled in turn 1 cm below the tube tip through a catheter placed via a tracheostomy. Open or closed suction, randomly assigned, was applied for 6s at -140 mmHg using a 6-F gauge catheter. Following lung injury with repeated saline lavage the procedure was repeated on conventional and high frequency ventilation.

MEASUREMENTS AND RESULTS

Iopamidol recovery was determined by digitally subtracting the post-contrast and post-suction radiographic images. Mucin recovery was determined by fluorescence assay of the aspirate. In the normal lung similar amounts were recovered by both suction methods. In the lavaged lung closed suction recovered less iopamidol during conventional (22 +/- 7.5%) and high frequency ventilation (11 +/- 2.4%) than open suction (36 +/- 2% and 22 +/- 8.1%, respectively). Mucin recovery was less with closed suction during conventional 32 +/- 28 microl) and high frequency ventilation (30 +/- 31 microl) than with open suction (382 +/- 235 microl and 24 +/- 153 microl).

CONCLUSIONS

In the injured lung closed suction was less effective than open suction at recovering thin and thick simulated secretions, irrespective of ventilation mode.

A 72-hour study to test the efficacy and safety of the "Mucus Slurper" in mechanically ventilated sheep

OBJECTIVE

In patients intubated with endotracheal tubes (ETTs), suctioning is routinely performed to remove mucus from within the ETT and trachea. The Mucus Slurper is a novel ETT with built-in suction ports arranged radially at its tip. We evaluated the safety and efficacy of the Mucus Slurper, compared with conventional tracheal suction, to prevent airway obstruction in sheep with the ETT and trachea oriented below horizontal.

DESIGN

Prospective randomized animal study.

SETTING

Animal research facility at the National Institutes of Health.

SUBJECTS

Twelve healthy sheep.

INTERVENTIONS

Sheep were randomized to be intubated with either the Mucus Slurper (study group) or a Hi-Lo Tracheal Tube (Mallinckrodt, St. Louis, MO) (control group) and mechanically ventilated for 72 hrs. In the study group, automatic, timed tracheal aspiration lasted 0.3 secs, was repeated every 2 mins, and was synchronized with the early expiratory phase. In the control group, tracheal suction was performed every 6 hrs or as required.

MEASUREMENTS AND MAIN RESULTS

In the control group, tracheal secretions accumulated progressively within the ETT and the trachea. In the study group, all mucus that reached the tip of the Mucus Slurper was aspirated, keeping the lumen of the ETT, and proximal trachea, free from secretions. In the study group, expiratory water trap protein concentration, a crude index to measure mucus drainage through the ETT, was consistently less than the control group (p < .001). At autopsy, no macroscopic injury to the tracheal mucosa was found in either group. In the study group, the respiratory circuit was less colonized than in the control group. There were no statistically significant differences between the two groups in bacterial colonization of the lungs/bronchi.

CONCLUSIONS

The Mucus Slurper, combined with orientation of the trachea below horizontal, prevents accumulation of secretions within the lumen of the ETT and trachea, without need for conventional tracheal suctioning.

Antibacterial-coated tracheal tubes cleaned with the Mucus Shaver : a novel method to retain long-term bactericidal activity of coated tracheal tubes

OBJECTIVE

To assess the long-term benefit from antibacterial coatings of the tracheal tube (ETT), and to keep clean the lumen of the ETT.

DESIGN

Experimental animal study.

SETTING

USA National Institutes of Health.

SUBJECTS

Twelve sheep.

INTERVENTIONS

Twelve ETTs were internally dip-coated with a silver-sulfadiazine in polyurethane. We developed a concentric inflatable silicone rubber "razor", the Mucus Shaver (MS), to shave the ETT lumen free of mucus. In a single pass, we cleaned all mucus from the internal surface of the ETT.

CONTROL GROUP

Five intubated sheep were mechanically ventilated for 72 h. The ETT was suctioned every 6 h.

STUDY GROUP

Six sheep were intubated and mechanically ventilated for 72 h. The ETT was suctioned and cleaned with the MS every 6 h. An additional sheep was intubated and mechanically ventilated for 168 h. Bacteriologic studies and scanning electron microscopy were performed to assess bacterial colonization and thickness of secretions on the internal surface of the ETT.

MEASUREMENTS AND MAIN RESULTS

In the control group, the ETT was always heavily colonized: median debris thickness was 380 microm, range 270-550 microm. In the study group, there was no colonization and no secretions in the ETT, except for three ETT that were colonized solely at the very tip.

CONCLUSIONS

Silver-based coating of ETT cleaned with the MS every 6 h significantly reduces accumulation of mucus/secretion and bacterial growth within the ETT following 72 h of mechanical ventilation.

Effect of reusing suction catheters on the occurrence of pneumonia in children

OBJECTIVE

The purpose of this study was to determine whether disposable suction catheters can be reused in the same patient for a 24-hour period without affecting the incidence of pneumonia.

DESIGN

The study design was a randomized controlled trial.

SETTING

The study was conducted in the pediatric intensive care unit of a tertiary pediatric center.

SAMPLE

Subjects included 486 children with an endotracheal tube in place.

OUTCOME MEASURES

The development of pneumonia, diagnosed with radiographic and clinical evidence, was the measure. Cost analysis was also undertaken.

METHOD

Subjects in the study group (n = 241) were suctioned using the same catheter for a 24-hour period. Those in the control group (n = 245) had a new catheter for each episode of suctioning.

RESULTS

Pneumonia developed in 14 members (5.71%) of the control group and in 12 members (4.98%) of the study group, a difference of 0.7% (95% CI, -3.3% to 4.7%). Cost analysis indicated a saving of Aust $4.14 per patient per day.

CONCLUSION

Reusing suction catheters for up to 24 hours is both safe and cost-effective.

Warning! Suctioning. A lung model evaluation of closed suctioning systems

BACKGROUND

Closed system suctioning, CSS, has been advocated to avoid alveolar collapse. However, ventilator manufacturers indicate that extreme negative pressure levels can be obtained during closed system suctioning, impeding the performance of the ventilator.

METHODS

Suctioning with a 12 or 14 Fr catheter with a vacuum level of -50 kPa was either performed with an open technology or a CSS, where the catheter is introduced through a tight-fitting connection through the endotracheal tube, EYT. The lung model was ventilated with a Servo 900C or 300 ventilator with an I:E ratio of 1:2, 1:1 and 2:1 and extrinsic positive end-expiratory pressure (PEEP) at 0 or 10 cm H20. Respiratory volumes and alveolar pressure were measured at the lung model alveolus.

RESULTS

The initial suctioning flow was >40 l/min with a 14 Fr catheter. When inserting the catheter through a no. 7 ETT, PEEP rose from 11 to 23 cm H2O during volume control ventilation with an I:E ratio 1:1. During suctioning the alveolar pressure fell to 10 cm H2O below the set PEEP level. CSS during pressure control ventilation had fewer effects. Low tidal volumes, inverse I:E ratio and secretions in the tube resulted in pressures down to -92 cm H2O.

CONCLUSION

CSS should not be used in volume control ventilation due to risk of high intrinsic PEEP levels at insertion of the catheter and extreme negative pressures during suctioning. Pressure control ventilation produces less intrinsic PEEP effect. The continuous positive airway pressure (CPAP) mode offers the least intrinsic PEEP during insertion of the catheter and least sub-atmospheric pressure during suctioning.

Direct tracheal airway pressure measurements are essential for safe and accurate dynamic monitoring of respiratory mechanics. A laboratory study

BACKGROUND

All monitoring of respiratory mechanics should depend on tracheal pressures (Trach-P) as endotracheal tube resistance (ETT-Res) will otherwise distort them. The aim of this study was to investigate factors that may vary ETT-Res, causing difficulties in ETT-Res estimation clinically, and to evaluate a method for direct Trach-P measurements to obviate these problems.

METHODS

In a model we studied: 1) The influence on ETT-Res caused by different connectors and secretions; 2) Direct Trach-P measurements with a catheter (o.d. 2 mm, i.d. 0.9 mm) with either end or side hole, filled with either air or liquid, introduced through the ETT lumen and evaluated regarding response time and position.

RESULTS

The pressure drop between trachea and Y-piece increased by 15% when respectively a swivel connector and a humidification device were connected to the ETT. When injecting 1 ml and 2 ml gel into the ETT lumen the inspiratory resistance increased 100% and 600% respectively. The response time of all catheters was < or = 12 ms. During constant flow in inspiratory and expiratory directions the pressure difference between an end hole catheter positioned from 2 cm above the ETT tip to 4 cm below and a reference pressure in the artificial trachea was less than 1.5 cmH2O.

CONCLUSIONS

ETT connections and secretions cause a variance in resistance. Tracheal pressure can be measured with high precision with an air- or liquid-filled catheter. An end hole catheter placed within 2 cm above or below the ETT tip will give sufficiently precise measurements for clinical purposes.

A computed tomographic scan assessment of endotracheal suctioning-induced bronchoconstriction in ventilated sheep

This study was directed at assessing changes in bronchial cross-sectional surface areas (BCSA) and in respiratory resistance induced by endotracheal suctioning in nine anesthetized sheep. Cardiorespiratory parameters (Swan-Ganz catheter), respiratory resistance (inspiratory occlusion technique), BCSA, and lung aeration (computed tomography) were studied at baseline, during endotracheal suctioning, and after 20 consecutive hyperinflations. Measurements performed initially at an inspired oxygen fraction (FI(O(2))) of 0.3 were repeated at an FI(O(2)) of 1.0. At an FI(O(2)) of 0.3, endotracheal suctioning resulted in atelectasis, a reduction in BCSA of 29 +/- 23% (mean +/- SD), a decrease in arterial oxygen saturation from 95 +/- 3% to 87 +/- 12% (p = 0.02), an increase in venous admixture from 19 +/- 10% to 31 +/- 19% (p = 0. 006), and an increase in lung tissue resistance (DR(rs)) (p = 0. 0003). At an FI(O(2)) of 1.0, despite an extension of atelectasis and an increase in pulmonary shunt from 19 +/- 5% to 36 +/- 2% (p < 0.0001), arterial O(2) desaturation was prevented and BCSA decreased by only 7 +/- 32%. A recruitment maneuver after endotracheal suctioning entirely reversed the suctioning-induced increase in DR(rs) and atelectasis. In three lidocaine-pretreated sheep, the endotracheal suctioning-induced reduction of BCSA was entirely prevented. These data suggest that the endotracheal suctioning-induced decrease in BCSA is related to atelectasis and bronchoconstriction. Both effects can be reversed by hyperoxygenation maneuver before suctioning in combination with recruitment maneuver after suctioning.