Biomedical subjects

P Loula

Publications and source records attributed to P Loula.

18 recordsLinked to original sources

PubMed1999

Using IP-videoconferencing systems in a surgery consulting.

In this paper we describe how to use IP-videoconferencing systems in medical surgery consulting. We started to think about how we could use special doctor's services without patients having to travel a long way. The answer to this question is that the information goes from one place to another, not the patient. First we had a pilot project, where we used the 3xISDN transmission rate and now we are using ATM. We have here in Satakunta a local area network between our Satakunta Central Hospital and the Health Care Center in Noormarkku and Kankaanpää, so we have very good environment to do this kind of research. Our network is quite fast, we can use the 10 Mbps bitrate and in this network there are no other activities in this moment, so there are not any interferences. There is a surgery specialist in the hospital and a doctor in the health care center with a patient. The specialist looks at the monitor, where there is a videopicture of the patient from the health care center. Then the specialist makes the treatment plan for the patient.

Adolescent↗

PubMed1999

End-user point of view to establish real-time broadband ATM connection over Europe.

There have so far been few discussions about how the international broadband services will be created in practice. In this paper we concentrate on two separate international telemedicine trials in which Satakunta Central Hospital took part in the HIM project. In these trials we tested real-time video consultation over the international point-to-point ATM network connection between hospitals in Finland, Portugal and Germany. The quality of the consultations were clinically first-rate in both trials. The technological lesson learned from these trials was valuable for the operators in establishing broadband connections in Europe. The network connection was analysed based on transmission capabilities of the network connection.

Computer Communication Networks↗

PubMed1999

Automatization of physicians' phone-in hours.

In this paper we present a computer-based system that is designed to reduce the number of patient calls in physicians' phone-in hours. Simultaneously it will offer a parallel alternative channel for the patients to listen to their laboratory results. The system requirements were reliability, security and the low costs. The results showed after a two-month test period that the tailored system proved extremely successful. The average time that the physician saved by using this system was over 4 minutes and doctors can leave the messages to the server also outside the phone-in hours.

Computer Systems↗

PubMed1997

Respiratory sinus arrhythmia during anaesthesia: assessment of respiration related beat-to-beat heart rate variability analysis methods.

Beat-to-beat heart rate variability analysis is a powerful tool for the diagnosis of neuropathy. Respiration-related heart rate variability (respiratory sinus arrhythmia, RSA) reflects the function of parasympathetic nervous system during spontaneous ventilation while awake. RSA is also claimed to monitor the depth of anaesthesia. Power spectrum analysis or various averaging techniques of the heart rate variability are usually applied. The current literature, however, does not usually interpret the ground rules and limitations of the method used, and this may sometimes lead to erroneous conclusions on the data. The aim of our study was to compare and analyse critically the performance of different methods of evaluating RSA during anaesthesia and positive pressure ventilation. Power spectrum analysis, the root mean square of the successive RR-interval difference (RMSSD), and two respiration related methods, RSA index and average phase RSA, were included in the comparison. To test these methods, 11 patients were anaesthetised with isoflurane and their lungs were ventilated mechanically with a frequency of 6 cycles min-1. Each patient received a bolus dose of atropine (20 micrograms kg-1) during the trial. Electrocardiogram, electroencephalogram and tracheal pressure signal from respirator were recorded and analyses were performed off-line. We demonstrated that general indices, such as RMSSD, may be strongly affected by heart rate level and other non-respiration related variations in heart rate. We also showed that the effect of unwanted fluctuations on RSA can be reduced with respiration dependent beat-to-beat methods. Furthermore we confirmed that in addition to the amplitude, also the pattern of respiratory sinus arrhythmia is of interest: the pattern is reversed in phase compared to spontaneous breathing while awake, as we have shown earlier. To analyse RSA during anaesthesia, we recommend the use of an average phase RSA method based on beat-to-beat variability that shows both the amplitude and pattern of RSA. Finally, no measure of RSA should be used without a presentation of the actual beat-to-beat heart rate curve.

Adjuvants, Anesthesia↗

PubMed1997

The detection of drowsiness and sleep onset periods from ambulatory recorded polygraphic data.

A 30 min sample recording at the sleep onset of 7 healthy male subjects was used to further develop a computer-scoring algorithm applied earlier for the analysis of MSLT recordings. The performance of this algorithm was tested on 7 patients with obstructive sleep apnea by using 6 h daytime recordings including drowsiness and sleep episodes. The total epoch-by-epoch agreement between visual and computer scoring was over 90% and the accurate detection rate of non-REM sleep was 64%. The hypnograms produced by the computer scoring corresponded sufficiently to those obtained by visual scoring. Our automatic scoring system can give a good estimation of the daytime vigilance profile but for clinical diagnosis the results have to be verified visually. However, by using modern digital recording, analyzing and scoring techniques the speed of analysis and thus the costs can markedly been reduced as compared to traditional visual analysis.

Adult↗

PubMed1997

Distributed clinical neurophysiology.

We have developed a consultation forum for clinical neurophysiology in Finland. The system connects local digital electroencephalography (EEG) recording and analysing networks using a high-speed asynchronous transfer mode (ATM) network. Clinicians can obtain a second opinion using interactive data and video consultations or using data-only consultations. In addition, the system can be used for off-line review of pre-recorded data. During a one-month evaluation, 66 EEG recordings were made altogether in Satakunta Central Hospital and consultations were required on 12 occasions. Nine of them were data-only consultations and three were data and video consultations. A data consultation lasted 15-20 min and a data and video consultation 35-45 min. Clinically, there were numerous benefits for the hospitals. The system established a link to a centre of excellence for second opinions or continuing education. It also helped with on-duty arrangements and enabled the construction of national data banks.

Electroencephalography↗

PubMed1996

Linear multivariate models for physiological signal analysis: theory.

The general linear parametric multivariate modelling concept is presented. This model combines a variety of different kinds of multivariate linear models. The concept of partial spectral analysis is derived from the general model. Some emphasis is laid on the causality demands of the model, and it is shown that the classic strictly-causal structure must be abandoned in order to utilise the modelling in many practical situations. Two special sub-class models are described in detail: the multivariate autoregressive model and the multivariate dynamic adjustment model. Furthermore, time-varying modelling is considered. The modelling of the real system is presented on a general level as a system identification cycle. The application of the methods to real physiological data is presented in the companion paper.

Data Collection↗

PubMed1996

Linear multivariate models for physiological signal analysis: applications.

Some applications of linear multivariate modelling methods in the analysis of physiological signals are presented. These applications illustrate the methods in the analysis of cardiovascular dynamics, which has been one of the main application fields of the multivariate modelling during the last ten years. It is demonstrated that physiologically meaningful information about the causal interactions in the cardiovascular system can be drawn from the routinely available clinical signals. Both static and dynamic conditions are considered.

Humans↗

PubMed1996

Nonlinear eye movement detection method for drowsiness studies.

Automatic long-term vigilance analysis systems require information about the occurrence and type of eye movements, in addition to information about other physiological signals. This paper presents a method to detect different types of eye movements in ambulatory recordings. The method is based on the application of a weighted FIR-median-hybrid filter in the preprocessing of the signal and on the novel use of linear correlation between two EOG signals which are obtained using a new, improved electrode montage. The evaluation of the method showed that it performed well in detecting isolated unambiguous eye movements, but differences were observed in comparison to visual scoring in borderline cases. The method was found to be suitable for use as part of a signal analysis system for drowsiness studies.

Electrooculography↗

PubMed1995

The effect of skin incision followed by alfentanil on catecholamine levels and on the T-wave amplitude of ECG during isoflurane anaesthesia.

Haemodynamic, ECG T-wave amplitude and plasma potassium changes and plasma catecholamine responses to skin incision followed by alfentanil were studied in 24 ASA I patients. Propofol and vecuronium were used without anticholinergics for induction of anaesthesia followed by isoflurane in 02/air. End-tidal isoflurane concentration was kept constant (0.7%) for 30 min before the skin incision. Five min after the skin incision alfentanil 30 mu g kg-1 was given. Blood samples for catecholamines and plasma potassium concentrations were drawn from right ventricle of the heart one minute before and after the skin incision and two minutes after alfentanil. Heart rate, systolic and diastolic arterial pressures increased after the skin incision (P < 0.001), and decreased after alfentanil (P < 0.001). Plasma adrenaline and noradrenaline concentrations increased slightly after the skin incision (P < 0.05 and P < 0.01, respectively). Noradrenaline levels continued to increase after alfentanil (P < 0.001) despite totally abolished haemodynamic responses to the skin incision. ECG T-wave amplitude changes, measured as R/T ratio, did not correlate to the changes in plasma catecholamine levels: both rapid increases and decreases in R/T ratio were seen. No plasma potassium changes were seen during the trial. T-wave changes, occurring in seconds after the skin incision, are probably produced by a direct catecholamine release from cardiac sympathetic nerve endings.

Adult↗

PubMed1995

ECG T-wave amplitude changes during thiopentone induction with or without alfentanil.

The T-wave amplitude of ECG is thought to reflect the sympathetic tone of the heart but anaesthesia studies on this topic are rare. Haemodynamic and ECG T-wave amplitude changes were studied during induction of anaesthesia in 24 ASA I-II patients. Twelve patients were given alfentanil 30 micrograms kg-1 at induction while physiologic saline was given to the rest (control). Thiopentone was then administered at the rate of 5 mg s-1 until eyelash reflex disappeared. Vecuronium 0.1 mg kg-1 was given thereafter. No anticholinergics were used. The lungs were ventilated with 40% oxygen in air. Haemodynamic parameters and T-wave amplitude were measured before induction, before intubation, 30 s, 3 min and 5 min after intubation. A significantly higher amount of thiopentone was needed to abolish the eyelash reflex in the control group than in the alfentanil group (P < 0.001). There were no changes in heart rate (HR) in the alfentanil group during the trial. Systolic and diastolic arterial pressures (SAP and DAP) were continuously below the preinduction levels in the alfentanil group. After baseline HR, SAP and DAP were significantly higher in the control group than in the alfentanil group at each data point. T-wave amplitude flattened significantly (P < 0.001) after intubation in the control group while no significant changes were seen in the alfentanil group. T-wave flattening correlated to the increases in HR (P < 0.01) and SAP (P < 0.01). Three control patients with flattened T-wave had a transient bigeminia period after intubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

The relationship between EEG delta activity and autonomic activity as measured by SCSB during daytime sleep.

The aim of the present work was to study the applicability of the static-charge-sensitive bed (SCSB) method to sleep studies, by comparing autonomic nervous activity measured with the SCSB and EEG delta activity (0.5-2 Hz). Simultaneous polygraphic and SCSB measurements of the first sleep cycle (110 min) were recorded from seven subjects. The amount of delta activity filtered from the EEG was compared in 3 min epochs to an autonomic activity index (AAI) based on cardiac, respiratory and body movement activity. Individual Spearman rank order correlation coefficients between delta amplitude and the AAI varied from 0.17 to -0.60. Therefore, it is concluded that the relationship between the delta activity and the AAI is not systematic enough for defining 'depth' of sleep at any point in time by using the AAI. However, on average, the SCSB differentiates high and low delta values quite well. With some further improvement of the scoring system the SCSB is a useful tool in comparative sleep studies.

Journal Article↗

PubMed1994

DC-level detection of burst-suppression EEG.

The EEG signal is usually recorded with low time constant analog prefilters to avoid low frequency artefacts. During this kind of recording the frequency components below the cutoff frequency of the analog prefilter (usually below about 1 to 3 Hz) are lost. By visual examination of some experimental recordings taken with a higher time constant, it was noticed that during burst-suppression EEG the DC-level of the signal rises sharply when the burst begins and falls when the burst ends. Thus, a burst actually consists of a mixed frequency discharge on a pulse-like DC-shift. We developed a filter algorithm to estimate the change in the DC-level during bursts as accurately as possible.

Algorithms↗

PubMed1994

Nonlinear interpretation of respiratory sinus arrhythmia in anesthesia.

A non-parametric method is presented for modelling nonlinear dynamic mechanisms of respiratory sinus arrhythmia (RSA) in anesthesia caused by positive pressure ventilation. RR interval sequences are shown with Tsay's linearity test to contain both short-term and long-term nonlinear components, which cannot completely be modelled with optimal linear methods. The nonlinear approach is based on Wiener's theory for broad-band random input signal. The input-output model is formed for tracheal pressure and RR interval sequence. Second-order and third-order nonlinearities in RSA fluctuation are found and demonstrated.

Adult↗

PubMed1993

The effect of small differences in electrode position on EOG signals: application to vigilance studies.

The primary aim of the study was to determine the best electrode positions for EOG signals in vigilance studies. Two-channel recordings were conducted in analogy to the Rechtschaffen and Kales (1968) system. Twenty electrodes (10 electrode pairs) were compared. Both EOG amplitudes and amplitude asymmetries within an electrode pair were studied. The amplitude of the EOG signal is sensitive to relatively small differences in electrode position. This concerns especially distance from the eye, the direction of eye movement and the effect of the upper eye lid movement. Larger and more symmetrical EOG amplitudes were obtained for different eye movements by placing the electrodes more medially than in the conventionally used system. EOG asymmetry in different electrode positions was dependent on the eye movement direction and even on the starting and end points of a movement with equal angular degrees. Most of the data could be explained by a simple monopolar model when combined with the effects of the upper eye lid movements. The most unexpected finding was that the EOG amplitudes of the horizontal and oblique eye movements were significantly larger when the eyes were moving towards an electrode than when they were moving to the opposite direction.

Adult↗

PubMed1993

Validation of computer analysed polygraphic patterns during drowsiness and sleep onset.

A computer system for the automatic analysis of polygraphic records was validated. Records from 9 subjects made during routine MSLT tests were analysed both by two preliminary and one consensus scorer and by a computer system. Special attention was paid to the analysis of drowsiness periods. Therefore a classification system including 7 stages, three for wakefulness and movement, one for drowsiness and three for the sleep stages S1, S2 and SREM was used. Adaptive segmentation was used to divide the records into short segments of variable length (mean 1.6 sec, range 0.5-13.7 sec). The agreements between the computer and visual scores were relatively good for 5 subjects having a prominent occipital alpha activity during wakefulness (range 70-79%) but less promising (range 64-70%) for the other 4 subjects with "poor" occipital alpha activity. The values obtained corresponded to the inter-scorer agreements. Most of the discrepancies were between adjacent stages. At times in the presence of strongly fluctuating EEG amplitudes and especially with the "low-alpha" subjects it was very difficult to determine exactly even by visual scoring when, for instance, drowsiness became sleep. It is concluded that the reliability of the system is sufficient for practical purposes especially if critical parts of the records are visually reexamined. It was found to be difficult to define unambiguous scoring criteria for subjects with poorly defined EEG rhythms giving insufficient landmarks for stage determination.

Adult↗

PubMed1993

Atropine abolishes electroencephalogram-associated heart rate changes without an effect on respiratory sinus arrhythmia during anaesthesia in humans.

Heart rate fluctuates with the electroencephalogram burst suppression pattern during anaesthesia: increasing at burst onset and decreasing at suppression. Heart rate also oscillates with positive pressure ventilation. The effects of atropine on these heart rate changes were studied in 12 patients during isoflurane anaesthesia and positive pressure ventilation at a frequency of 6 cycles min-1. Four additional patients served as controls. A bolus dose of atropine (20 micrograms kg-1 intravenously) abolished the electroencephalogram-correlated heart rate changes; however, the amplitude of respiratory sinus arrhythmia was not changed after atropine. The control mechanism of the burst suppression pattern in electroencephalogram also affects parasympathetic heart rate control. The control mechanisms of respiratory sinus arrhythmia during anaesthesia with positive pressure ventilation differ from those during spontaneous breathing awake.

Adult↗

PubMedDate not supplied

A computerized analysis system for vigilance studies.

A digital signal analysis system for vigilance studies is presented. The analysis is based on adaptive segmentation, band pass filtering, nonlinear eye movement detection and rule-based decision making. A preliminary evaluation of seven subjects falling asleep showed that the system is able to detect small vigilance fluctuations reliably.

Artifacts↗