Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 2011
Evaluation of a CO2 partial rebreathing functional residual capacity measurement method for use during mechanical ventilation.
There is a need for an automated bedside functional residual capacity (FRC) measurement method that does not require a step change in inspired oxygen fraction. Such a method can be used for patients who require a high inspired oxygen fraction to maintain arterial oxygenation and for patients ventilated using a circle breathing system commonly found in operating rooms, which is not capable of step changes in oxygen. We developed a CO(2) rebreathing method for FRC measurement that is based on the change in partial pressure of end-tidal carbon dioxide and volume of CO(2) eliminated at the end of a partial rebreathing period. This study was designed to assess the accuracy and precision of the proposed FRC measurement system compared to body plethysmography and nitrogen washout FRC. ⋯ The CO(2) rebreathing method for FRC measurement provides acceptable accuracy and precision during stable ventilation compared to the gold standards of body plethysmography and nitrogen washout. The results based on periods of stable ventilation best approximate the performance of the system in the likely areas of application during controlled mechanical ventilation. Further study of the CO(2) rebreathing method is needed to evaluate accuracy in a larger group of controlled mechanical ventilation patients, including patients with respiratory insufficiency and significant lung injury.
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J Clin Monit Comput · Dec 2011
Impact of central hypovolemia on photoplethysmographic waveform parameters in healthy volunteers part 2: frequency domain analysis.
The photoplethysmographic (PPG) waveforms are modulated by the respiratory, cardiac and autonomic nervous system. Lower body negative pressure (LBNP) has been used as an experimental tool to simulate loss of central blood volume in humans. The aim of our research is to understanding PPG waveform changes during progressive hypovolemia. ⋯ The pulse oximeter waveform contains a complex mixture of the effect of cardiac, venous, autonomic, and respiratory systems on the central and peripheral circulation. The occurrence of autonomic modulation needs to be taken into account when studying signals that have their origins from central sites (e.g. ear and forehead).
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J Clin Monit Comput · Dec 2011
Pulse oximetry saturation patterns detect repetitive reductions in airflow.
Postoperative patients exhibiting signs or symptoms of obstructive sleep apnea (OSA) have been identified to be at increased risk for respiratory compromise. One of the key markers associated with OSA is repetitive reductions in airflow (RRiA). A real-time pulse oximeter saturation pattern recognition algorithm (OxiMax SPD™ intended for adult in-hospital use only) designed to detect specific signatures in the SpO(2) trend associated with RRiA may provide caregivers early indication of its presence so they can treat the patient appropriately. The purpose of our study was to test the performance of saturation pattern detection (SPD) in a clinical study targeting subjects with a high prevalence of RRiA. ⋯ The real-time SPD algorithm was able to detect episodes of RRiA in sleep lab patients with a high degree of sensitivity and specificity.
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J Clin Monit Comput · Dec 2011
Impact of central hypovolemia on photoplethysmographic waveform parameters in healthy volunteers. Part 1: time domain analysis.
Our study sought to explore changes in photoplethysmographic (PPG) waveform param- eters, during lower body negative pressure (LBNP) which simulated hypovolemia, in spontaneously breathing volunteers. We hypothesize that during progressive LBNP; there will be a preservation of ear PPG parameters and a decrease in finger PPG parameters. ⋯ PPG waveform parameters may prove to be sensitive and specific as early indicators of blood loss. These PPG changes were observed before profound decreases in arterial blood pressure. The relative sparing of central cutaneous blood flow is consistent with the increased parasympathetic innervation of central structures.
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J Clin Monit Comput · Dec 2011
Capability of a new paediatric oesophageal Doppler monitor to detect changes in cardiac output during testing of external pacemakers after cardiac surgery.
The Cardio QP™ oesophageal Doppler monitor measures the velocity time integral of the blood flow in the descending aorta. Based on system integrated normograms of the aortic cross-sectional area of a paediatric population, the cardiac output is calculated and displayed. ⋯ The Cardio QP™ seems to be capable of detecting slight changes in cardiac output.