Clinical Meaning
Ventilator waveform analysis is the systematic interpretation of pressure time, flow time, and volume time scalar graphics displayed on the mechanical ventilator to assess respi...
Ventilator waveform analysis is the systematic interpretation of pressure-time, flow-time, and volume-time scalar graphics displayed on the mechanical ventilator to assess respiratory mechanics and optimize ventilation. The pressure-time waveform shows peak inspiratory pressure (PIP) reflecting total airway resistance plus lung/chest wall compliance, and plateau pressure (Pplat) reflecting alveolar distending pressure (static compliance). The difference between PIP and Pplat represents resistive pressure from airway resistance. The flow-time waveform displays inspiratory and expiratory flow patterns; in normal conditions, expiratory flow returns to zero baseline before the next breath. Auto-PEEP (intrinsic PEEP) is detected when expiratory flow does NOT return to zero before the next inspiration, indicating air trapping -- confirmed by performing an end-expiratory hold maneuver. The volume-time waveform shows tidal volume delivery and return; incomplete return to baseline indicates air leak or air trapping. Static compliance (Cst) = tidal volume / (Pplat - total PEEP), with normal being 60-100 mL/cmH2O; decreased compliance indicates stiff lungs (ARDS, pulmonary fibrosis, atelectasis, pneumothorax). Airway resistance (Raw) = (PIP - Pplat) / flow, with normal being 5-10 cmH2O/L/s; increased resistance indicates bronchospasm, mucus plugging, or...
