Evaluation of an active humidification system for inspired gas.

OBJECTIVES: The effectiveness of the active humidification systems (AHS) in patients already weaned from mechanical ventilation and with an artificial airway has not been very well described. The objective of this study was to evaluate the performance of an AHS in chronically tracheostomized and spontaneously breathing patients. METHODS: Measurements were quantified at three levels of temperature (T°) of the AHS: level I, low; level II, middle; and level III, high and at different flow levels (20 to 60 L/minute). Statistical analysis of repeated measurements was performed using analysis of variance and significance was set at a P<0.05. RESULTS: While the lowest temperature setting (level I) did not condition gas to the minimum recommended values for any of the flows that were used, the medium temperature setting (level II) only conditioned gas with flows of 20 and 30 L/minute. Finally, at the highest temperature setting (level III), every flow reached the minimum absolute humidity (AH) recommended of 30 mg/L. CONCLUSION: According to our results, to obtain appropiate relative humidity, AH and T° of gas one should have a device that maintains water T° at least at 53℃ for flows between 20 and 30 L/m, or at T° of 61℃ at any flow rate.

Evaluation of tracheal cuff pressure variation in spontaneously breathing patients.

BACKGROUND: Most of the studies referring cuff tubes' issues were conducted on intubated patients. Not much is known about the cuff pressure performance in chronically tracheostomized patients disconnected from mechanical ventilation. OBJECTIVE: To evaluate cuff pressure (CP) variation in tracheostomized, spontaneously breathing patients in a weaning rehabilitation center. MATERIALS AND METHODS: Experimental setup to test instruments in vitro, in which the gauge (TRACOE) performance at different pressure levels was evaluated in six tracheostomy tubes, and a clinical setupin which CP variation over 24 h, every 4 h, and for 6 days was measured in 35 chronically tracheostomized clinically stable, patients who had been disconnected from mechanical ventilation for at least 72 h. The following data were recorded: Tube brand, type, and size; date of the tube placed; the patient's body position; the position of the head; axillary temperature; pulse and respiration rates; blood pressure; and pulse oximetry. RESULTS: In vitro difference between the initial pressure (IP) and measured pressure (MP) was statistically significant (P < 0.05). The difference between the IP and MP was significant when selecting for various tube brands (P < 0.05). In the clinical set-up, 207 measurements were performed and the CP was >30 cm H2O in 6.28% of the recordings, 20-30 cm H2O in 42.0% of the recordings, and <20 cm H2O in 51.69% of the recordings. CONCLUSION: The systematic CP measurement in chronically tracheostomized, spontaneously breathing patients showed high variability, which was independent of tube brand, size, type, or time of placement. Consequently, measurements should be made more frequently.