ICU · Respiratory / monitoring
Ventilator Waveforms — Scalars, Pressure-Volume & Flow-Volume Loops
Also known as Ventilator waveforms · Pressure-volume loop · P-V loop · Flow-volume loop · Pressure-time scalar · Flow-time scalar · Plateau pressure · Peak inspiratory pressure · Driving pressure · Patient-ventilator asynchrony
Ventilator waveforms are the bedside physics of mechanical ventilation. The scalars (pressure, volume, and flow against time) and the loops (pressure-volume and flow-volume) show airway resistance, compliance, overdistension, and patient-ventilator interaction. The key manoeuvre is the inspiratory hold, which separates the peak pressure into its resistive and elastic components: a high peak with a normal plateau is an airway-resistance problem (bronchospasm, kink, secretions), while a high peak with a high plateau is a compliance problem (ARDS, oedema, pneumothorax). The driving pressure (plateau minus PEEP) and the static compliance (Vt divided by plateau minus PEEP) quantify the stress on the lung.
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Overview & definition
Ventilator waveforms are the bedside physics of mechanical ventilation — three scalars (pressure, volume, and flow against time) and two loops (pressure-volume and flow-volume) that lay bare resistance, compliance, overdistension, and synchrony. The one manoeuvre that unlocks all of it is the inspiratory hold, which splits the peak pressure into a resistive piece and an elastic piece.[1]
References12ShowHide
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