• Alpesh R Patel, Susan Taylor, and Andrew D Bersten.
• Intensive and Critical Care Unit, Flinders Medical Centre, Adelaide, SA, Australia. alpesh.patel@health.sa.gov.au
• Crit Care Resusc. 2012 Jun 1;14(2):130-4.

ObjectiveTo compare respiratory mechanics estimated by the (pulse) technique in spontaneously breathing patients during proportional assist ventilation (PAV) with load-adjustable gain factor (PAV+) mode with those measured using the flow-interruption technique during controlled ventilation.Design, Participants And SettingObservational study of 21 haemodynamically stable post-cardiac surgery patients with routine weaning from mechanical ventilation (Puritan-Bennett 840 ventilator) in the intensive care unit of a tertiary hospital.Main Outcome MeasuresBland-Altman and linear correlation of respiratory system compliance and inspiratory resistance estimated during PAV+ (C(pulse) and R(pulse)) with that measured during controlled mechanical ventilation (C(int) and Rint).ResultsC(pulse) overestimated C(int) (67.4 [SD, 27.7] v 51.6 [SD, 9.7] mL/cmH(2)O; P = 0.02), although the correlation between C(int) and C(pulse) was strong. Using the Bland-Altman method, the bias and limits of agreement were outside a clinically useful range. R(pulse) underestimated Rint (9.3 [SD, 3.0] v 11.5 [SD, 3.0] cmH(2)O/L/s; P = 0.02), with a weak positive correlation. Although the bias calculated by the Bland-Altman method was small, the limits of agreement were too large to be clinically useful.ConclusionBased on these data, respiratory mechanics estimated from the (pulse) technique are too inaccurate to be clinically useful.

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