Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 1999
The relationship between modified pulse wave transit time and cardiovascular changes in isoflurane anesthetized dogs.
To clarify the relationship between blood pressure and pulse wave transit time at the peripheral artery from the R wave of the electrocardiogram (m-PWTT), the effects of cardiovascular interventions on this relationship was evaluated. ⋯ Change in m-PWTT is a good parameter to predict blood pressure changes, although the absolute blood pressure value cannot be obtained.
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J Clin Monit Comput · Dec 1999
Comparative Study Clinical TrialMonitoring of heart and respiratory rates in newborn infants using a new photoplethysmographic technique.
A new photoplethysmographic (PPG) device for respiratory and heart rate monitoring has been evaluated in the neonatal care units at the University Children's Hospital of Uppsala, Sweden. The purpose of this study was to compare this new device with more established techniques, i.e., transthoracic impedance plethysmography (TTI) for monitoring of respiratory rate and ECG for heart rate monitoring. ⋯ Electrode and motion artefacts seem to disturb the ECG signals and, particularly, the impedance signals. During periods of high quality ECG and impedance signals, the new optical device produces signals of equal quality to these traditional methods, and is in some cases even better. The new device is non-invasive and has a small optical probe. These factors indicate further advantages of the photoplethysmographic method.
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J Clin Monit Comput · Dec 1999
Comparative Study Clinical TrialA comparison of pulse oximetry and near infrared spectroscopy (NIRS) in the detection of hypoxaemia occurring with pauses in nasal airflow in neonates.
The aim of this study was to compare the ability of NIRS and pulse oximetry to detect changes in cerebral oxygenation occurring in response to a pause in nasal airflow (PNA). ⋯ We conclude that both techniques are sensitive to changes in oxygenation during PNA. Small changes in cerebral Hbdiff and arterial SpO2 do not always correlate for physiological reasons. A change in Hbdiff of >0.3 micromol 100 g brain(-1) is likely to be physiologically significant and is associated with a change in SpO2 of 12%.
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J Clin Monit Comput · Dec 1999
Autoregulation in a simulator-based educational model of intracranial physiology.
To implement a realistic autoregulation mechanism to enhance an existing educational brain model that displays in real-time the cerebral metabolic rate (CMRO2), cerebral blood flow (CBF), cerebral blood volume (CBV), intracranial pressure (ICP), and cerebral perfusion pressure (CPP). ⋯ The autoregulated brain model, with incorporated CO2 responsivity and a variable oxygen extraction, automatically produces changes in CVR, CBF, CBV, and ICP consistent with literature reports, when run concurrently with a METI full-scale patient simulator (Medical Education Technologies, Inc., Sarasota, Florida). Once the model is enhanced to include herniation, vasospasm, and drug effects, its utility will be expanded beyond demonstrating only basic neuroanesthesia concepts.
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J Clin Monit Comput · Dec 1999
The influence of left lateral position on cardiac output changes after head up tilt measured by impedance cardiography.
The value of the impedance cardiography (IC) method for measuring cardiac output (CO) with the subject in the left lateral position has not yet been established. We compared the CO after a 30 degrees head-up tilt with the subjects in the supine and left lateral position. ⋯ When using the IC method of SV measurement, the absolute value of the CI changes when moving from the supine to lateral positions. It is not clear whether this change is physiologic or an artifact of the measurement technique. However, changes in CI in response to a 30 degree head up tilt are the same in either position. We conclude that changes in CI can be measured with the IC method in the lateral position.