Physiological measurement
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Physiological measurement · Dec 2005
Clinical TrialEstimation of breathing interval from the photoplethysmographic signals in children.
Two important parameters that are generally under continual observation during clinical monitoring are heart rate (HR) variability and breathing interval (BI) of patients. Current HR monitoring during night-long childhood respiratory sleep studies is well tolerated but BI monitoring requires instrumentation, like nasal cannula, that can be less accommodating for children. In this study, BI was extracted from the photoplethysmographic (PPG) signals using a two-stage signal processing technique termed zero-phase digital filtering. ⋯ Statistical analysis revealed that mean BI attained from the PPG signals were significantly related during tidal breathing (r(2) = 0.76; range 0.61-0.83; p < 0.05) and with the IRL (r(2) = 0.79; range 0.68-0.85; p < 0.05) in the absence of motion artefacts. Preliminary findings herein suggest that besides having the capability to monitor HR and arterial blood oxygen saturation measurements, the PPG signals can be used to derive BI for children. This can be an attractive alternative for children who are more disturbed by intrusive techniques in prolonged clinical monitoring.
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Physiological measurement · Dec 2005
The influence of cardiac preload and positive end-expiratory pressure on the pre-ejection period.
The pre-ejection period (PEP) has recently been described as a potential parameter for monitoring cardiac preload. This study further investigated the influence of changes in intravascular volume status and the application of positive end-expiratory pressure (PEEP) on the pre-ejection period. In ten pigs, ECG, arterial pressure and stroke volume derived from an aortic flowprobe were registered. ⋯ However, PEP did not change significantly (from 73 to 82 ms, P > 0.05). No correlation between the changes in PEP and changes in any other variable was observed. It is concluded that PEP is not sensitive to the changes in intravascular volume status.
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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
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
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.