Clinical physiology and functional imaging
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Clin Physiol Funct Imaging · May 2009
Changes in left ventricular ejection time and pulse transit time derived from finger photoplethysmogram and electrocardiogram during moderate haemorrhage.
Early identification of haemorrhage is difficult when a bleeding site is not apparent. This study explored the potential use of the finger photoplethysmographic (PPG) waveform derived left ventricular ejection time (LVET(p)) and pulse transit time (PTT) for detecting blood loss, by using blood donation as a model of controlled mild to moderate haemorrhage. ⋯ Shortening of LVET(p) from 303+/-2 to 293+/-3 ms (mean+/-SEM; P<0.01) and prolongation of PTT from 177+/-3 to 186+/-4 ms (P<0.01) were observed in 81% and 91% of subjects respectively when comparing PRE and POST. During blood donation, progressive blood loss produced falling trends in LVET(p) (P<0.01) and rising trends in PTT (P<0.01) in FIRST and SECOND, but a falling trend in RRi (P<0.01) was only observed in SECOND. Monitoring trends in timing variables derived from non-invasive ECG and finger PPG signals may facilitate detection of blood loss in the early phase.
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Clin Physiol Funct Imaging · May 2009
Experimental case report: development of a pneumothorax monitored by electrical impedance tomography.
Electrical impedance tomography (EIT) is a non-invasive, radiation-free functional imaging technique, which allows continuous bedside measurement of regional lung ventilation. Pneumothorax is an uncommon but nevertheless potentially dangerous incident that may arise unexpectedly. We report an incident of an accidental tension pneumothorax during an experimental ventilation study in a pig that was continuously monitored by EIT. ⋯ At the same time the ventilation-related impedance changes of the left lung remained almost unchanged. The pneumothorax onset was localized using a newly introduced pneumothorax dynamics map directly derived from dynamic EIT data. We conclude that non-invasive EIT may be helpful as a tool to detect the development of a pneumothorax, which could be of particular interest during invasive procedures such as insertion of a central venous catheter.