Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 1998
Influence of pulse oximeter settings on the frequency of alarms and detection of hypoxemia: Theoretical effects of artifact rejection, alarm delay, averaging, median filtering or a lower setting of the alarm limit.
The potential benefit of a reduced frequency of false pulse oximeter low oxyhemoglobin saturation (SpO2) alarms is that the attention of personnel is only directed to patients who experience hypoxemia. The present study was undertaken to better understand the effects of different settings of the pulse oximeter on false (artifact) and true (hypoxemia) alarms. ⋯ The data from the present study suggest that in order to effectively suppress false alarms caused by pulse oximeter artifacts, it may be preferable to use a longer filtering epoch of approximately 40 s, rather than to decrease the lower alarm limit.
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J Clin Monit Comput · Apr 1998
Estimation of ventricular volume and elastance from the arterial pressure waveform.
We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. ⋯ This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation is limited to the simplified model used and requires experimental validation, it demonstrates that the technique is theoretically feasible.
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J Clin Monit Comput · Apr 1998
Propagation of nitric oxide pools during controlled mechanical ventilation.
Infusing nitric oxide at a constant rate into a breathing circuit with intermittent mainstream flow causes formation of nitric oxide pools between successive breaths. We hypothesized that incomplete mixing of these pools can confound estimates of delivered nitric oxide concentrations. ⋯ Incomplete mixing of nitric oxide confounds estimates of delivered nitric oxide concentrations. When nitric oxide is infused at a constant rate into a breathing circuit, we doubt that any sampling site outside the patient's lungs can reliably predict delivered nitric oxide concentrations. Strategies to ensure complete mixing and representative sampling of nitric oxide should be considered carefully when designing nitric oxide delivery systems.