Estimation of inspiratory muscle pressure in critically ill patients.
BACKGROUND
Recently, a new technology has been introduced aiming to monitor and improve patient ventilator interaction (PVI monitor). With the PVI monitor, a signal representing an estimation of the patient's total inspiratory muscle pressure (Pmus(PVI)) is calculated from the equation of motion, utilizing estimated values of resistance and elastance of the respiratory system.


OBJECTIVE
The aim of the study was to prospectively examine the accuracy of Pmus(PVI) to quantify inspiratory muscle pressure.


METHODS
Eleven critically ill patients mechanically ventilated on proportional assist ventilation with load-adjustable gain factors were studied at three levels of assist (30, 50 and 70%). Airway, esophageal, gastric and transdiaphragmatic (Pdi) pressures, volume and flow were measured breath by breath, whereas the total inspiratory muscle pressure (Pmus) was calculated using the Campbell diagram.


RESULTS
For a given assist, Pmus(PVI) throughout inspiration did not differ from the corresponding values calculated using the Pdi and Pmus signals. Inspiratory and expiratory time did not differ among the various methods of calculation. Inspiratory muscle pressure decreased with increasing assist, and the magnitude of this decrease did not differ among the various methods of pressure calculation.


CONCLUSIONS
A signal generated from flow, volume and airway pressure may be used to provide breath-by-breath quantitative information of inspiratory muscle pressure.
Kondili
Eumorfia
E
Intensive Care Medicine Department, University Hospital of Heraklion, Medical School, University of Crete, Heraklion, Crete, Greece.
Alexopoulou
Christina
C
Xirouchaki
Nectaria
N
Vaporidi
Katerina
K
Georgopoulos
Dimitris
D
D000368:Aged; D000704:Analysis of Variance; D016638:Critical Illness; D003964:Diaphragm / Q000502:physiology; D004548:Elasticity; D004947:Esophagus / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D011312:Pressure; D011446:Prospective Studies; D012123:Pulmonary Ventilation / Q000502:physiology; D012121:Respiration, Artificial / Q000379:methods*; D012132:Respiratory Muscles / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013270:Stomach / Q000502:physiology; D035441:Thoracic Wall / Q000502:physiology