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Monitoring of heart and respiratory rates in newborn infants using a new photoplethysmographic technique
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Department of Pediatrics, University Children´s Hospital, Uppsala, Sweden.
1999 (English)In: Journal of clinical monitoring and computing, ISSN 1387-1307, E-ISSN 1573-2614, Vol. 15, no 7-8, 461-467 p.Article in journal (Refereed) Published
Abstract [en]

Objective.A new photoplethysmographic (PPG) device for respiratoryand heart rate monitoring has been evaluated in the neonatal care units at theUniversity Children's Hospital of Uppsala, Sweden. The purpose of thisstudy was to compare this new device with more established techniques, i.e.,transthoracic impedance plethysmography (TTI) for monitoring of respiratoryrate and ECG for heart rate monitoring.

Methods.Data were acquiredcontinuously for 8-hours in each of 6 neonates. The signals were analysed forperiods of 30 seconds, in which the heart and respiratory signals from the PPGdevice were compared with the ECG and the impedance plethysmogram.

Results.The ECG recordings were of high quality in 77% of the analysed periods.In these periods, excluding periods (6%) disturbed by offset-adjustement ofthe PPG signal, the PPG heart signal included 1.1% (±0.7% SD) falsenegative beats and 0.9% (±0.6%) false positive beats. In periods withan impedance signal of high quality (29% of total time), the part of the PPGsignal synchronous with respiration included 2.7% (±1.1%) falsenegative breaths and 1.5% (±0.4%) false positive breaths. Here, 2% ofthe periods were discarded because of offset-adjustment. From the periods oflow signal quality, two other conclusions were drawn: 1) The impedance signalcontains more power in the respiratory range than the corresponding PPGrespiratory signal. 2) The breaths are easier to identify in the PPGrespiratory signal than in the impedance signal (subjective measure).

Conclusions.Electrode and motion artefacts seem to disturb the ECGsignals and, particularly, the impedance signals. During periods of highquality ECG and impedance signals, the new optical device produces signals ofequal quality to these traditional methods, and is in some cases even better.The new device is non-invasive and has a small optical probe. These factors indicate further advantages of the photoplethysmographic method.

Place, publisher, year, edition, pages
1999. Vol. 15, no 7-8, 461-467 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-32558DOI: 10.1023/A:1009912831366Local ID: 18471OAI: oai:DiVA.org:liu-32558DiVA: diva2:253381
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
In thesis
1. Photoplethysmography in multiparameter monitoring of cardiorespiratory function
Open this publication in new window or tab >>Photoplethysmography in multiparameter monitoring of cardiorespiratory function
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Photoplethysmography (PPG) is an optical, non-invasive method to assess tissue blood volume/perfusion. When measured on human skin, the PPG signal includes both cardiac synchronous variations (AC) and respiratory induced intensity variations (RIIV). This makes the PPG signal appropriate for cardiorespiratory monitoring, as a single non-invasive sensor extracts both cardiac and respiratory information.

In this thesis, the origin of the RIIV signal is discussed, and invasive measurements of pressures in the circulatory system support the hypothesis of a venous origin. Important factors are intrathoracic and intra-abdominal pressure fluctuations, affecting venous return from the extrathoracic veins and the peripheral venous bed.

Previous reports have demonstrated a possibility to extract the RIIV signal for assessing respiratory rates. A more effective and reliable monitoring would be achieved if tidal volumes could be estimated from the PPG signal in addition to respiratory rates. This would provide a possibility to calculate and detect ventilatory trends. A relationship between the RIIV amplitude and the tidal volume was hypothesised, demonstrated in healthy subjects and verified in a theoretical (Windkessel) model of the circulatory system. Other factors than tidal volume influence intrathoracic and intra-abdominal pressures. Effects of thoraco-abdominal separation, posture and respiratory rate were observed, and their influence in tidal volume/ventilation monitoring was discussed.

Monitoring the cardiorespiratory function is essential in the postoperative and neonatal care environments. Studies have been performed in clinical settings including comparisons between the PPG method and more established monitoring systems. PPG was found to be suitable for monitoring heart and respiratory rates in these environments.

The arterial blood pressure contains respiratory related information, including heart rate fluctuations (respiratory sinus arrhythmia, RSA) and respiratory variations in cardiac stroke volume. These phenomena are seen in the PPG signal as frequency and amplitude modulation of the AC signal. An algorithm based on pattern recognition (neural networking) is presented, in which these respiratory components are extracted and combined with the RIIV signal. As the respiratory components are of different origins, the neural network algorithm is robust and more accurate for breath detection than algorithms utilising the components separately.

The main purposes of cardiorespiratory monitoring are to detect pathologic minute ventilation, apnoea, hypoxaemia, cardiac arrest, arrhythmia, and trends in heart rate. By using PPG, simultaneous information about heart rate, respiratory rate and tidal volume is obtained. Furthermore, as the measurement of arterial oxygen saturation by PPG is well established, a good coverage of the cardiorespiratory function can be obtained from a single non-invasive sensor.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2000. 63 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 629
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29446 (URN)14793 (Local ID)91-7219-715-3 (ISBN)14793 (Archive number)14793 (OAI)
Public defence
2000-04-28, Elsa Brändströms sal, Universitetssjukhuset, Linköping, 13:15 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-02-19

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Johansson, AndersÖberg, Åke

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