Observational study of patient-ventilator asynchrony and relationship to sedation level

J Crit Care. 2009 Mar;24(1):74-80. doi: 10.1016/j.jcrc.2008.08.011. Epub 2009 Jan 17.


Purpose: Clinicians frequently administer sedation to facilitate mechanical ventilation. The purpose of this study was to examine the relationship between sedation level and patient-ventilator asynchrony.

Materials and methods: Airway pressure and airflow were recorded for 15 minutes. Patient-ventilator asynchrony was assessed by determining the number of breaths demonstrating ineffective triggering, double triggering, short cycling, and prolonged cycling. Ineffective triggering index (ITI) was calculated by dividing the number of ineffectively triggered breaths by the total number of breaths (triggered and ineffectively triggered). Sedation level was assessed by the following 3 methods: Richmond Agitation-Sedation Scale (RASS), awake (yes or no), and delirium (Confusion Assessment Method for the intensive care unit [CAM-ICU]).

Results: Twenty medical ICU patients underwent 35 observations. Ineffective triggering was seen in 17 of 20 patients and was the most frequent asynchrony (88% of all asynchronous breaths), being observed in 9% +/- 12% of breaths. Deeper levels of sedation were associated with increasing ITI (awake, yes 2% vs no 11%; P < .05; CAM-ICU, coma [15%] vs delirium [5%] vs no delirium [2%]; P < .05; RASS, 0, 0% vs -5, 15%; P < .05). Diagnosis of chronic obstructive pulmonary disease, sedative type or dose, mechanical ventilation mode, and trigger method had no effect on ITI.

Conclusions: Asynchrony is common, and deeper sedation level is a predictor of ineffective triggering.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Analysis of Variance
  • Conscious Sedation / adverse effects*
  • Conscious Sedation / methods
  • Critical Care
  • Drug Monitoring / methods
  • Equipment Failure
  • Female
  • Humans
  • Male
  • Middle Aged
  • Monitoring, Physiologic / methods
  • Pilot Projects
  • Pulmonary Disease, Chronic Obstructive / physiopathology
  • Pulmonary Disease, Chronic Obstructive / therapy
  • Respiration, Artificial / adverse effects*
  • Respiration, Artificial / instrumentation
  • Respiration, Artificial / methods
  • Respiratory Insufficiency / metabolism
  • Respiratory Insufficiency / physiopathology
  • Respiratory Insufficiency / therapy
  • Respiratory Mechanics / physiology*
  • Risk Factors
  • Sample Size
  • Time Factors
  • Virginia
  • Wakefulness / drug effects