November 2008

Notes from the Section

• If you’re planning to attend the AARC Congress in Anaheim, this Dec. 13–16, be sure to come by the section meeting, scheduled for Monday, 4:45–5:30 p.m.
• Learn more about the AARC Congress and what it has to offer adult acute care RTs in the Advance Program.
• And for an inside look into other aspects of the meeting—including some great videos of last year’s event and a link to things to see and do in Orange County that was constructed especially for the AARC—go here.

Mid-level Ventilators Don’t Measure Up When it Comes to Triggering
Are mid-level ICU ventilators comparable in triggering performance to a standard ICU ventilator? Investigators from the respiratory care laboratory at Massachusetts General Hospital in Boston believe the answer is no. Their study compared results for ten mid-level ventilators and a standard ICU ventilator using a computerized mechanical lung model programmed for two levels of lung model effort, three combinations of respiratory mechanics (normal, COPD, and ARDS), and two modes of ventilation (volume and pressure assist/control). Results showed a wide difference in performance among the ventilators:

• Mean inspiratory trigger time was <100 ms for only half of the tested ventilators.
• The mean inspiratory delay time was longer than that for the ICU ventilator for all tested ventilators except one.
• The pressure drop during triggering was comparable with that of the ICU ventilator for only two ventilators.
• Expiratory settling time had the greatest variability among ventilators.

“Some of these ventilators had a much poorer triggering response with high inspiratory effort than the ICU ventilator,” conclude the authors, who published their findings in the September issue of Intensive Care Medicine. “These ventilators do not perform as well as ICU ventilators in patients with high ventilatory demand.” READ ABSTRACT

Best Practice Protocol for Spontaneous Breathing Trial Falls Short
Researchers led by a group from Washington University in St. Louis, MO, find peer networks can be effective in promoting and implementing evidence-based best practices. However, the practice they implemented — a consensus definition of the spontaneous breathing trial—fell somewhat short of expectations. The study was carried out in six medical, two surgical, and two combined medical/surgical adult ICUs in eight academic medical centers and involved 705 patients who had 3,486 safety screens for conducting a spontaneous breathing trial. Among the group, 2,072 (59%) failed the safety screen, 379 (11%) failed a two minute tolerance screen, and 1,122 (34%) underwent a full, 30-120 minute spontaneous breathing trial. However, just 55% of passing spontaneous breathing trials actually resulted in liberation from mechanical ventilation before another spontaneous breathing trial was performed. “Implementation of a best practice (spontaneous breathing trial) may be necessary for, but by itself insufficient to achieve, consistent and timely liberation from ventilator support,” note the researchers. The study appeared in the October issue of Critical Care Medicine. READ ABSTACT

VAP: Diagnosis and Therapy Remain Problematic
Ventilator-associated pneumonia (VAP) has been suggested as a “never event” in hospitals. Harvard Medical School investigators publishing in the September issue of Best Practice & Research-Clinical Anaesthesiology point out problems with that scenario, noting diagnosis of the condition continues to be problematic at best. While clinical signs and symptoms are generally used to identify patients with a lung infection, the Boston researchers point out these signs and symptoms can be produced by many conditions besides VAP. They go on to note that studies show bacterial-induced pathologic processes occur prior to the onset of symptoms, and using bacterial cultures alone requires providers to wait days for results, during which time they have no choice but to order days of empiric antibiotic therapy. In addition, exploratory molecular studies utilizing clone libraries and molecular arrays for microbial identification question the ability of culture-based techniques to identify all the microbes involved in VAP. These studies find oral flora are present in the lungs of VAP patients as well, which suggests that the aspiration of oral secretions and/or biofilms on endotracheal tubes supplies the bacteria for VAP. “Much more investigation is needed to determine the optimal timing of antibiotic treatment and which diagnostic molecular methods can be utilized in the ICU,” write the authors. READ ABSTRACT

APRV, BIPAP Suffer from Definitional Ambiguity
Confusion appears to reign when it comes to the criteria that distinguish airway pressure release ventilation (APRV) and biphasic positive airway pressure (BIPAP), report researchers from the University of Toronto in Ontario, Canada. They reached that conclusion after conducting a systematic review of the literature on the two modes of ventilation. Fifty studies and 18 discussion articles were identified; 39 focused on APRV and 11 on BIPAP. The researchers found:

• Compared to BIPAP, APRV was described more frequently as an extreme inverse inspiratory:expiratory ratio and rarely used as a noninverse ratio.
• One BIPAP and eight APRV studies used a mild inverse ratio, while there was an increased use of a 1:1 ratio with BIPAP.
• In adult studies, the mean reported set inspiratory pressure was 6 cm H2O greater with APRV when compared to reports of BIPAP.
• For both modes, the mean reported positive end expiratory pressure was 5.5 cm H2O.
• Thematic review identified an inconsistency of mode descriptions.The researchers believe commercial ventilator branding is contributing to the confusion, and suggest generic naming of modes and consistent definitional parameters could help clarify the issue and assist with clinical implementation. The study appeared in the October issue of Intensive Care Medicine. READ ABSTRACT