Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 2014
Clinical TrialDetection of respiratory compromise by acoustic monitoring, capnography, and brain function monitoring during monitored anesthesia care.
Episodes of apnea in sedated patients represent a risk of respiratory compromise. We hypothesized that acoustic monitoring would be equivalent to capnography for detection of respiratory pauses, with fewer false alarms. In addition, we hypothesized that the patient state index (PSI) would be correlated with the frequency of respiratory pauses and therefore could provide information about the risk of apnea during sedation. ⋯ For the 51 respiratory pauses validated by retrospective analysis, the sensitivity, specificity, and likelihood ratio positive for detection were 16, 96 %, and 3.5 for clinician observation; 88, 7 %, and 1.0 for capnography; and 55, 87 %, and 4.1 for acoustic monitoring. There was no correlation between PSI and respiratory pause events. Acoustic monitoring had the highest likelihood ratio positive for detection of respiratory pause events compared with capnography and clinician observation and, therefore, may provide the best method for respiration rate monitoring during these procedures.
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J Clin Monit Comput · Dec 2014
Measuring gas exchange with step changes in inspired oxygen: an analysis of the assumption of oxygen steady state in patients suffering from COPD.
Bedside estimation of pulmonary gas exchange efficiency may be possible from step changes in FIO2 and subsequent measurement of arterial oxygenation at steady state conditions. However, a steady state may not be achieved quickly after a change in FIO2, especially in patients with lung disease such as COPD, rendering this approach cumbersome. This paper investigates whether breath by breath measurement of respiratory gas and arterial oxygen levels as FIO2 is changed can be used as a much more rapid alternative to collecting data from steady state conditions for measuring pulmonary gas exchange efficiency. ⋯ Calculated model parameters were shown to be similar for the two data sets, with Bland-Altman bias and limits of agreement of -0.4 and -3.0 to 2.2 % for calculation of pulmonary shunt and 0.17 and -0.47 to 0.81 kPa for alveolar to end-capillary PO2, a measure of oxygen abnormality due to shunting plus regions of low [Formula: see text] A/[Formula: see text] ratio. This study shows that steady state oxygen levels may not be necessary when estimating pulmonary gas exchange using changes in FIO2. As such this technique may be applicable in patients with lung disease such as COPD.
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J Clin Monit Comput · Dec 2014
Melodic algorithms for pulse oximetry to allow audible discrimination of abnormal systolic blood pressures.
An anesthesiologist must remain vigilant of the patient's clinical status, incorporating many independent physiological measurements. Oxygen saturation and heart rate are represented by continuous audible tones generated by the pulse oximeter, a mandated monitoring device. Other important clinical parameters--notably blood pressure--lack any audible representation beyond arbitrarily-configured threshold alarms. ⋯ A rhythmic variation in which additional auditory information was conveyed only at halftime intervals, with every other "beat" of the pulse oximeter, was strongly favored. The respondents also strongly favored the use of musical chords over single tones. Given three algorithms of tones embedded in the pulse oximeter signal, anesthesiologists preferred a melodic tone to signal a significant change in blood pressure.
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J Clin Monit Comput · Oct 2014
Comparative StudyA knowledge- and model-based system for automated weaning from mechanical ventilation: technical description and first clinical application.
To describe the principles and the first clinical application of a novel prototype automated weaning system called Evita Weaning System (EWS). EWS allows an automated control of all ventilator settings in pressure controlled and pressure support mode with the aim of decreasing the respiratory load of mechanical ventilation. Respiratory load takes inspired fraction of oxygen, positive end-expiratory pressure, pressure amplitude and spontaneous breathing activity into account. ⋯ During the later course, EWS significantly modified most of the ventilator settings and reduced the imposed respiratory load. A novel prototype automated weaning system was successfully developed. The first clinical application of EWS revealed that its operation was stable, safe ventilator settings were defined and the respiratory load of mechanical ventilation was decreased.
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J Clin Monit Comput · Oct 2014
Evaluation of techniques for estimating the power spectral density of RR-intervals under paced respiration conditions.
Heart rate variability (HRV) analysis is increasingly used in anaesthesia and intensive care monitoring of spontaneous breathing and mechanical ventilated patients. In the frequency domain, different estimation methods of the power spectral density (PSD) of RR-intervals lead to different results. Therefore, we investigated the PSD estimates of fast Fourier transform (FFT), autoregressive modeling (AR) and Lomb-Scargle periodogram (LSP) for 25 young healthy subjects subjected to metronomic breathing. ⋯ Above 7 breaths per minute, all methods showed a significant increase in LF/HF ratio with increasing BF. On average, the RMSRE of FFT was lower than for LSP and AR. Therefore, under paced respiration conditions, estimating RR-interval PSD using FFT is recommend.