Evaluation of Endotracheal Tube Scraping on Airway Resistance.

BACKGROUND: Spontaneous breathing trials (SBTs) are used to assess the readiness for discontinuation of mechanical ventilation. When airway resistance (Raw) is elevated, the imposed work of breathing can lead to prolongation of mechanical ventilation. Biofilm and mucus build-up within the endotracheal tube (ETT) can increase Raw. Scraping the ETT can remove the biofilm build-up and decrease mechanical Raw. The primary aim of this study was to evaluate the impact of ETT scraping on Raw. The secondary aim was to determine whether decreasing Raw would impact subsequent SBT success. METHODS: Intubated, mechanically ventilated subjects were enrolled if they failed an SBT and had an Raw of > 10 cm H2O/L/s. SBT failure was based on institutional guidelines, and Raw was calculated by subtracting the difference between the measured peak and plateau pressures using a square flow waveform with an inspiratory flow set at 60 L/min. The endOclear device was inserted into the ETT and withdrawn per manufacturer's guidelines. Scraping was repeated until the ETT was cleared. Change in Raw was compared pre- and post-ETT scraping using a paired t test. A Mann-Whitney U test evaluated the difference in percentage change in Raw between SBT groups. RESULTS: Twenty-nine subjects completed the study. The mean pre- and post-ETT scraping Raw values were 15.17 ± 3.83 and 12.05 ± 3.19 cm H2O/L/s, respectively (P < .001). Subsequent SBT success was 48%; however, there was no difference in percentage change in Raw between subsequent passed SBT (18.61% [interquartile range 8.90-33.93%]) and failed SBT (23.88% [interquartile range 0.00-34.80%]), U = 78.5, z = -0.284, P = .78. No adverse events were noted with ETT scraping. CONCLUSIONS: This study demonstrated that ETT scraping can reduce Raw. The decrease in Raw post-ETT scraping did not affect subsequent SBT success.

The Effect of Nebulizer Position on Aerosolized Epoprostenol Delivery in an Adult Lung Model.

BACKGROUND: Aerosolized epoprostenol is an alternative for inhaled nitric oxide in the management of pulmonary arterial hypertension and possibly acute hypoxemia. Our objective was to determine differences in drug deposition based on different nebulizer positions in the ventilator circuit, using a vibrating mesh nebulizer. METHODS: An 8.0-mm inner diameter endotracheal tube (ETT) was connected to a training test lung, compliance of 30 mL/cm H2O, with a collecting filter placed at the ETT-test lung junction. A mechanical ventilator, heated wire circuit, and pass-over humidifier were utilized. A syringe pump continuously instilled a 15,000-ng/mL epoprostenol solution at 30, 50, and 70 ng/kg/min into the vibrating mesh nebulizer at all 4 positions. Tidal volumes (VT) were set at 4, 6, and 8 mL/kg for a 70-kg patient with breathing frequencies of 25, 16, and 12 breaths/min, respectively. Epoprostenol was eluted from the filters (no. = 180) and analyzed with ultraviolet-visible spectrophotometry at 205 nm to estimate drug deposition. RESULTS: Epoprostenol deposition increased significantly (P = .02) as the dosage increased from 30 ng/kg/min (median 4,520.0 ng, interquartile range [IQR] 2,285.0-6,712.2 ng) to 50 ng/kg/min (median 6,065.0 ng, IQR 3,220.0-13,002.5 ng) and 70 ng/kg/min (median 9,890.0 ng, IQR 6,270.0-16,140.0 ng). No significant difference was found between variations in ventilator settings. No difference in deposition was found between the humidifier inlet and outlet, but these positions resulted in greater deposition compared with the inspiratory limb and between the ETT and Y-piece. CONCLUSIONS: The greatest amount of mean epoprostenol deposition resulted with the nebulizer placed at the humidifier inlet or outlet in a ventilator with bias flow.

Ventilator Liberation for High-Risk-for-Failure Patients: Improving Value of the Spontaneous Breathing Trial.

Several patient populations have been identified as high risk for extubation failure despite successful completion of a spontaneous breathing trial (SBT). Extubation failure and subsequent need for emergent re-intubation have been associated with increased morbidity and mortality. In this review, we discuss ways to optimize the value and performance of the SBT in a subgroup of high-risk patients (elderly, cardiac, and/or respiratory failure) to reduce the rate of extubation failure. We recommend the use of T-piece mode, longer duration SBT, and measurement of the rapid shallow breathing index (breathing frequency/tidal volume in L) off ventilatory support to increase the predictive value of the SBT. In addition, measurement of changes in central venous oxygen saturation and serum brain natriuretic peptide, and measurements of mitral inflow and annular velocity using bedside transthoracic echocardiography with tissue Doppler imaging may help guide the clinician in determining who and when to extubate and thus minimize the rate of extubation failure. Arterial blood gas analysis performed at the end of the SBT may help determine who will benefit from prophylactic use of noninvasive ventilatory support postextubation.