Patient ventilator asynchrony in critically ill adults: frequency and types.

BACKGROUND: Patient ventilator asynchrony (PVA) occurs frequently, but little is known about the types and frequency of PVA. Asynchrony is associated with significant patient discomfort, distress and poor clinical outcomes (duration of mechanical ventilation, intensive care unit and hospital stay). METHODS: Pressure-time and flow-time waveform data were collected on 27 ICU patients using the Noninvasive Cardiac Output monitor for up to 90 min per subject and blinded waveform analysis was performed. RESULTS: PVA occurred during all phases of ventilated breaths and all modes of ventilation. The most common type of PVA was Ineffective Trigger. Ineffective trigger occurs when the patient's own breath effort will not trigger a ventilator breath. The overall frequency of asynchronous breaths in the sample was 23%, however 93% of the sample experienced at least one incident of PVA during their observation period. Seventy-seven percent of subjects experienced multiple types of PVA. CONCLUSIONS: PVA occurs frequently in a variety of types although the majority of PVA is ineffective trigger. The study uncovered previously unidentified waveforms that may indicate that there is a greater range of PVAs than previously reported. Newly described PVA, in particular, PVA combined in one breath, may signify substantial patient distress or poor physiological circumstance that clinicians should investigate.

Autonomic nervous system function and depth of sedation in adults receiving mechanical ventilation.

BACKGROUND: The effect of the depth of sedation on the function of the autonomic nervous system is not well known. OBJECTIVES: To describe the effect of level of sedation on heart rate variability as a marker of the function of the autonomic nervous system in patients receiving mechanical ventilation. METHODS: This pilot study was part of a larger study in which sedation level was measured continuously for up to 24 hours. The sample consisted of 14 patients receiving mechanical ventilation. The R-R interval was measured continuously via electrocardiography. Sedation level was determined by using the Patient State Index and was categorized as deep (<60) or light (=60). Continuous heart rate data of 5 to 10 minutes for each sedation level for each patient were analyzed. RESULTS: Parasympathetic activity as indicated by root mean square of successive difference of the R-R interval, the high-frequency component, and the percentage of differences of successive N-N intervals (intervals due to normal sinus depolarization) that differed more than 50 milliseconds was significantly lower for deep sedation than for light sedation. The markers indicating sympathetic activity, including the low-frequency component and the ratio of the low-frequency component to the high-frequency component, did not differ significantly between the 2 levels of sedation. Most patients were receiving benzodiazepines. CONCLUSIONS: Deep sedation may be associated with depression of parasympathetic function in patients receiving mechanical ventilation. Use of benzodiazepines most likely contributed to this finding.

Biobehavioral measures in a critical-care healing environment.

Critical-care settings have an opportunity to create healing environments (HEs). For the last decade, achieving this goal has been the task of the American Association of Critical Care Nurses. Today, several models used in these settings embrace synergistic care, healing therapies for patients, and the development of organizational models to improve the HEs for nurses themselves. Creating the HE is not impossible; however, researching the patient's experience within it is complex. This complexity requires researchers to consider biological, behavioral, and social variables on the unit. This article will describe biological and behavioral measures that may be used to examine the critically ill patient's response to an HE. Limitations of these measures are considerable. Future researchers will need to consider a multiplistic approach to the study of this construct.