Physiological measurement
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Physiological measurement · Aug 2005
Clinical Trial Controlled Clinical TrialInfluence of data resolution and interpolation method on assessment of secondary brain insults in neurocritical care.
Continuous monitoring of physiologic vital signs is routine in neurocritical care. However, this patient information is usually only recorded intermittently (most often hourly) in the medical record. It is unclear whether this is sufficient to represent the occurrence of secondary brain insults (SBIs) or whether more frequent data collection will provide more comprehensive information for patient care. ⋯ MR data tended to underestimate the number of total events. 95% limits of agreement were most narrow for trapezoidal interpolation of MR data, but even these limits were fairly broad. Assessment of secondary brain insults is highly dependent on (1) the temporal resolution of the method used to acquire patient data and on (2) the interpolation method if data are acquired intermittently. High frequency data acquisition may be necessary for more precise evaluation of secondary brain injury in neurocritical care.
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Physiological measurement · Aug 2005
Randomized Controlled Trial Comparative Study Clinical TrialVariability in time delay between two models of pulse oximeters for deriving the photoplethysmographic signals.
Pulse oximetry is commonly used as an arterial blood oxygen saturation (SaO2) measure. However, its other serial output, the photoplethysmography (PPG) signal, is not as well studied. Raw PPG signals can be used to estimate cardiovascular measures like pulse transit time (PTT) and possibly heart rate (HR). ⋯ Novametrix differed from ECG by 0.71+/-0.58% (p<0.05) while Masimo differed by 4.51+/-3.66% (p>0.05). Modern oximeters can be attractive for their improved SaO2 measurement. However, using raw PPG signals obtained directly from these oximeters for timing-related measurements warrants further investigations.
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Physiological measurement · Aug 2005
Air mattress sensor system with balancing tube for unconstrained measurement of respiration and heart beat movements.
The cardio-respiratory signal is a fundamental vital sign used for assessment of a patient's status. Additionally, the cardio-respiratory signal provides a great deal of information to healthcare providers wishing to monitor healthy individuals. The air mattress sensor system allows the measurement of the respiration and heart beat movements without the use of a harness or sensor on the subject's body, which eliminates the difficulties these pose for long term measurements. ⋯ With this balancing tube, the meaningful frequency range could be selected using a pneumatic method. A mathematical model was constructed and validation experiments were performed for step and sinusoidal input signals. This technique was applied to measurements of respiration and heart beat movements in the supine posture on the bed, which showed potential for applications in sleep analysis, unconstrained healthcare monitoring and neonate monitoring.
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Physiological measurement · Aug 2005
Clinical TrialMeasuring the performance of audible alarms for anaesthesia.
The ergonomic performance of an integrated set of 17 audible alarm sounds, divided into low, medium and high priority classes has been undertaken. The sounds were tested for their ease of learning/recall, and how closely their intrinsic perceived urgency matched to a clinical assessment of urgency. The tests were computer-administered and performed on 21 volunteers aged from 18 to 52, in two sessions a few days apart. ⋯ The mean correct identification rate for the sounds was 48.4% (range 10.3-90.0%) with 97.5% of misidentifications within sound priority class. The urgency correlation was statistically significant (r=0.85, p<0.001) with all priority classes included but within priority class correlations were not statistically significant. Poor within priority class performances were ascribable to a priori aspects of the design of the sound system.
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Physiological measurement · Aug 2005
Coordinated FA-MS and SIFT-MS analyses of breath following ingestion of D2O and ethanol: total body water, dispersal kinetics and ethanol metabolism.
A coordinated study of the dispersal of water between the various body compartments (stomach and gut, blood stream and tissue) and the similar dispersal kinetics of ethanol and its metabolism has been carried out involving two healthy volunteers using flowing afterglow mass spectrometry, FA-MS, and selected ion flow tube mass spectrometry, SIFT-MS. Thus, using these techniques, the variations of HDO and ethanol in breath, measured in successive single exhalations, were followed in real time after the ingestion of measured quantities of D2O and ethanol in proportion to the body weights of the subjects at the dose rates D2O approximately 0.283 g kg-1, ethanol approximately 0.067 g kg-1. During the FA-MS experimental periods (about 2 h), the dispersion of HDO into the body water and finally its equilibration in the total body water is observed from which total body water for each subject was determined. ⋯ Thus, in one subject 30% and in the other subject 40% of the ingested alcohol is metabolized in the first 20 min following ingestion. The good time resolution allowed by non-invasive breath analysis ensures that the rates of processes such as ethanol metabolism can be accurately measured. Simultaneous measurements of breath acetaldehyde (largely formed via the ethanol metabolism) and acetone were also performed during the SIFT-MS single breath exhalations.