Using ventilator graphics to identify patient-ventilator asynchrony

Jon O. Nilsestuen, Kenneth D. Hargett

    Research output: Contribution to journalArticle

    Abstract

    Patient-ventilator interaction can be described as the relationship between 2 respiratory pumps: (1) the patient's pulmonary system, which is controlled by the neuromuscular system and influenced by the mechanical characteristics of the lungs and thorax, and (2) the ventilator, which is controlled by the ventilator settings and the function of the flow valve. When the 2 pumps function in synchrony, every phase of the breath is perfectly matched. Anything that upsets the harmony between the 2 pumps results in asynchrony and causes patient discomfort and unnecessarily increases work of breathing. This article discusses asynchrony relative to the 4 phases of a breath and illustrates how asynchrony can be identified with the 3 standard ventilator waveforms: pressure, flow, and volume. The 4 phases of a breath are: (1) The trigger mechanism (ie, initiation of the inspiration), which is influenced by the trigger-sensitivity setting, patient effort, and valve responsiveness. (2) The inspiratory-flow phase. During both volume-controlled and pressure-controlled ventilation the patient's flow demand should be carefully evaluated, using the pressure and flow waveforms. (3) Breath termination (ie, the end of the inspiration). Ideally, the ventilator terminates inspiratory flow in synchrony with the patient's neural timing, but frequently the ventilator terminates inspiration either early or late, relative to the patient's neural timing. During volume-controlled ventilation we can adjust variables that affect inspiratory time (eg, peak flow, tidal volume). During pressure-controlled or pressure-support ventilation we can adjust variables that affect when the inspiration terminates (eg, inspiratory time, expiratory sensitivity). (4) Expiratory phase. Patients with obstructive lung disease are particularly prone to developing intrinsic positive end-expiratory pressure (auto-PEEP) and therefore have difficulty triggering the ventilator. Bedside evaluation for the presence of auto-PEEP should be routinely performed and corrective adjustments made when appropriate.

    Original languageEnglish (US)
    Pages (from-to)202-232
    Number of pages31
    JournalRespiratory Care
    Volume50
    Issue number2
    StatePublished - Feb 2005

    Fingerprint

    Mechanical Ventilators
    Intrinsic Positive-Pressure Respiration
    Pressure
    Ventilation
    Work of Breathing
    Obstructive Lung Diseases
    Lung
    Positive-Pressure Respiration
    Tidal Volume
    Thorax

    Keywords

    • Asynchrony
    • Patient-ventilator interface
    • Ventilator graphics
    • Waveforms

    ASJC Scopus subject areas

    • Pulmonary and Respiratory Medicine

    Cite this

    Nilsestuen, J. O., & Hargett, K. D. (2005). Using ventilator graphics to identify patient-ventilator asynchrony. Respiratory Care, 50(2), 202-232.

    Using ventilator graphics to identify patient-ventilator asynchrony. / Nilsestuen, Jon O.; Hargett, Kenneth D.

    In: Respiratory Care, Vol. 50, No. 2, 02.2005, p. 202-232.

    Research output: Contribution to journalArticle

    Nilsestuen, JO & Hargett, KD 2005, 'Using ventilator graphics to identify patient-ventilator asynchrony', Respiratory Care, vol. 50, no. 2, pp. 202-232.
    Nilsestuen, Jon O. ; Hargett, Kenneth D. / Using ventilator graphics to identify patient-ventilator asynchrony. In: Respiratory Care. 2005 ; Vol. 50, No. 2. pp. 202-232.
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