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Effect of breathing pattern on the pressure-time product calculation
G Natalini1, M Marchesini, A Tessadrelli
1Department of Anesthesia, Intensive Care and Emergency, Poliambulanza Hospital, Brescia, Italy. natalini-giuseppe@poliambulanza.it
Acta Anaesthesiologica Scandinavica
|April 23, 2004
Summary
Breathing patterns significantly alter the pressure-time product (PTP) calculation, even with constant mechanical load and inspiratory time. A corrected PTP method better reflects the metabolic cost of breathing in mechanically ventilated patients.
Area of Science:
- Mechanical Ventilation
- Respiratory Physiology
Background:
- The pressure-time product (PTP) is a common metric for assessing respiratory load.
- Its calculation is theoretically dependent on mechanical load and inspiratory time per minute.
Purpose of the Study:
- To determine if breathing pattern affects PTP calculation when mechanical load and inspiratory time per minute are constant.
Main Methods:
- Respiratory mechanics and PTP were measured in 10 mechanically ventilated patients.
- Three different respiratory rate/tidal volume combinations were used, keeping minute ventilation and inspiratory time per minute constant.
Main Results:
- Despite constant elastic load, elastic PTP increased over 200% with lower respiratory rates.
- A 'corrected' elastic PTP, elastic double product, and mean elastic pressure per minute did not significantly change.
Conclusions:
- Breathing pattern significantly impacts PTP, independent of mechanical load and inspiratory time.
- The standard PTP may not accurately estimate the metabolic cost of breathing.
- A 'corrected' PTP, mean inspiratory pressure, or respiratory system double product can overcome this limitation.