Design evaluation of a home-based telecare system for Chronic Heart Failure patients.

In order to improve the care of Chronic Heart Failure (CHF) patients, a system has been developed for monitoring symptoms and document subjective judgments on health conditions in a home environment. Since system usability is an important issue, a two step evaluation of the solution was conducted. First a ten-patient survey was conducted, which was aimed at spotting possible problem areas. The second step involved a small trial in a home setting with CHF patients. The results are promising, indicating that the system is user friendly and easy to use, and that it is suitable as a prototype for the intended use.

Telemedicine and decision support in emergency ambulances in Uppsala.

In Sweden, as in many other countries, paramedics or nurses constitute the majority of prehospital personnel. If tasks usually performed by doctors are to be performed by these personnel, there is a need for guidelines and triage in the handling of medical emergencies. We describe an information management system used in ambulances for data communication, documentation, triaging and presentation of checklists. In most cases, data are input while the patient is being cared for. The information is collected and stored together with data automatically received from the dispatch centre. The latter date are transferred by a mobile radio network to the ambulance. Medical date (e.g. electrocardiograms) are transferred from the ambulance over the data network to the receiving medical facility. All transferred data are finally collected in a database for statistical analysis and follow-up.

Moment analysis of multibreath nitrogen washout in healthy preterm infants.

Moment analysis (MA) of multibreath nitrogen washout (MBNW) has not previously been applied to newborn infants. The aim of the present study was to adapt this method to healthy preterm infants using an improved technique suitable for small infants, and to determine reference values of MA. Twenty healthy preterm infants with a mean birth weight (+/-SD) of 1,666+/-402 g and a mean gestational age of 31.3+/-2.1 weeks were studied during their first 7-28 days of life. Computerized bedside equipment with very low dead space was constructed. The limits of normal variability were determined from results of duplicate studies. Outcome variables included functional residual capacity (FRC), the first-to-zeroth moment ratio (M1/M0), the second-to-zeroth moment ratio (M2/M0), and the lung clearance index (LCI). The starting point for MA had considerable impact on the results. Mean M1/M0 and M2/M0 were 2.18+/-0.18 and 8.71+/-1.24, respectively. No significant relation between moment ratios and weight, gender or age was found. Intrasubject coefficients of variation (CV) for M1/M0 (7.9+/-5.9%) and for M2/M0 (12.1+/-9.1%) and intersubject CV for M1/M0 (8%) and M2/M0 (14%) were similar to those reported in children and adults. Mean lung clearance index was 10.8+/-1.4 and intra- and intersubject CVs were 11.3+/-8.9% and 13%, respectively. Mean functional residual capacity (FRC) was 22.5+/-2.1 ml/kg. Mean intra- and intersubject CVs for FRC were 8.3% and 9%, respectively. We conclude that the MBNW test can be performed by a simple bedside method and that MA appears to be a suitable method for measuring gas mixing in preterm infants.

Surfactant replacement therapy improves ventilation inhomogeneity in infants with respiratory distress syndrome.

Surfactant deficiency in newborn infants with hyaline membrane disease (HMD) reduces peripheral airway stability, leading to lung atelectasis, inhomogeneity of distribution of ventilation, ventilation/perfusion mismatch, and hypoxemia. The aim of this study was to evaluate the immediate effect of exogenous surfactant treatment on ventilation inhomogeneity (VIH) in infants with HMD. Homogeneity of ventilation was measured repeatedly in ten infants (median gestational age 30 weeks and birthweight 1.50 kg) after Exosurf, and in six infants (median gestational age 30 weeks and birthweight 1.42 kg) after Survanta treatment. Lung function was measured before and 0.5, 2, and 6 hours after administration of a single dose of surfactant. The multiple breath nitrogen washout method was used to measure the time pattern of nitrogen elimination from the lungs. VIH was evaluated by using both a compartmental lung model and a model-independent moment analysis. The two-compartment lung model was found to dominate before surfactant treatment, while a single-compartment model (implying homogeneous ventilation) fitted the washout data best 6 hours after Exosurf treatment (P < 0.01). The same pattern occurred 2 hours after Survanta administration. Moment analysis confirmed the reduction in VIH by both surfactants. This study supports the hypothesis that the improved oxygenation after surfactant treatment in infants with HMD results from a reduction in VIH and an increase in functional residual capacity (FRC).

Establishment of functional residual capacity in infants delivered vaginally and by elective cesarean section.

Functional residual capacity (FRC) was measured with an open circuit N2 washout method in 20 vaginally born infants and 15 delivered by cesarean section, 30 and 120 min after birth. Umbilical artery blood was collected and analyzed for pH and catecholamine concentration. FRC was significantly higher in the cesarean section infants than in the vaginally delivered infants at 120 min of age (23.8 versus 16.8 ml/kg). The cesarean section infants also tended to have lower tidal volumes and higher respiratory frequencies than infants delivered vaginally. No significant correlation was found between catecholamine levels in umbilical artery and FRC in either group although there was a significant correlation between catecholamine level at birth and the increase of FRC from 30 to 120 min in the cesarean section group. It is suggested that the higher FRC, higher respiratory frequency and lower tidal volume in the cesarean section infants is an adaptation to a higher pulmonary water content to ensure an efficient gas exchange with the least respiratory work.

A plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants.

We have developed and tested a plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants during intensive care. Information about the mechanics of the respiratory system is obtained from the respiratory flow as measured by volume displacement plethysmography and from airway pressure measured in the artificial airway. Data on lung volumes, ventilation, and distribution of ventilation is obtained simultaneously by combining the respiratory flow measurements with nitrogen concentration analyses of the respiratory gas. No significant differences were found when the estimations of mechanical parameters and FRC were compared with reference methods and when determinations of the same parameters were repeated in the same subjects. The plethysmograph was shown to be safe and convenient to use, even in studies lasting several hours.

Clinical evaluation of an ensemble-averaging impedance cardiograph for monitoring stroke volume during spontaneous breathing.

Simultaneous determination of stroke volume (SV) with an ensemble-averaging impedance cardiograph (AIGG) and the thermodilution technique (TD) was compared in 10 patients scheduled for major vascular surgery. A small, successive increase in SV was achieved by a step-wise infusion of dextran-70 and elevation of the patient's legs. The patients were allowed to breathe normally during the measurement procedures. There was no difference between the ability of AICG and TD to monitor changes in SV and the correlation coefficient for the measurement of changes in SV by the two methods was 0.88. There was no difference between the reproducibility of AICG- (4.6 ml) and TD- (9.2 ml) determined SV or between the coefficient of variation for AICG (4.8%) and TD (9.9%). The mean difference between AICG- and TD-determined SV at the different measurement points (range 1.3-4.2 ml) was well within acceptable limits. In conclusion, the ensemble-averaging impedance cardiograph described in this study was found to be reliable for monitoring changes in SV during uninterrupted, spontaneous breathing.

Hemodynamic changes during laparoscopy with positive end-expiratory pressure ventilation.

Hemodynamic measurements were performed in 10 healthy women undergoing elective laparoscopy for the investigation of infertility. A standardized anesthetic technique which included the application of positive end-expiratory pressure (PEEP), 0.49 kPa (3.7 mmHg) was utilized. The following variables were studied: cardiac output, stroke volume and left ventricular ejection time (determined non-invasively with impedance cardiography), heart rate, blood pressure, total peripheral vascular resistance and end-tidal carbon dioxide (ET-CO2). The combination of 25 degrees head-down tilt and PEEP ventilation during laparoscopy was associated with a pressure response that restored arterial pressures to essentially pre-anesthetic levels. Net cardiac effects were small. With this regime low pressure 0.7-1.1 kPa (5-8 mmHg) intra-abdominal insufflation with CO2 was associated with only minor cardiovascular changes. There were no indications that 0.49 kPa PEEP during laparoscopy produced adverse cardiovascular effects. The application of PEEP reduced (P less than 0.001) ET-CO2. There was no net increase in ET-CO2 after CO2-insufflation compared to the measurement after induction of anesthesia. This is in contrast to earlier studies without PEEP where a significant net increase in ET-CO2 was reported after CO2-insufflation.

Lung function in newborn infants with tachypnea of unknown cause.

Twenty-one infants with tachypnea (f greater than 60/min) lasting more than 2 h and diagnosed as mild respiratory disease or pulmonary maladaptation according to previously presented criteria were studied during the course of the disease and after clinical recovery. Lung physiology (total and alveolar ventilation, efficiency and distribution of ventilation, functional residual capacity, and lung mechanics) was studied in combination with clinical data. The pathophysiological findings were characterized by increased total ventilation but normal alveolar ventilation, reduced efficiency of ventilation but more even distribution of ventilation (nitrogen elimination pattern) during disease than after clinical recovery, hyperinflation, reduced dynamic lung compliance but unaffected specific lung conductance. Infants with low gestational ages were most severely affected and had longer duration of disease than full-term infants. Our findings suggest that this condition is caused by small airway disease. Disturbances in normal pulmonary adaptation with abnormal retention of lung fluid is the most probable cause.

Efficiency of ventilation in neonatal pulmonary maladaptation.

Lung physiology was studied in sixteen infants with pulmonary maladaptation (PMA) during the course of the disease and after clinical recovery. A sensitive nitrogen washout method was used. During the disease the infants showed reduced ventilatory efficiency and increased dead space. Total ventilation increased simultaneously, while alveolar ventilation was maintained. The majority of the infants showed greater functional residual capacity during the disease than after clinical recovery. The results suggest that gas mixing efficiency is impaired in infants with PMA and that this might be due to effects on the small airway function in the lungs.

Effects of delivery by caesarean section on lung function in healthy newborn infants.

With the aim of extending previous studies showing differences in lung function after birth between infants delivered vaginally (VD) and by Caesarean section (CS) we investigated lung volumes, ventilation, efficiency of ventilation, and lung mechanics in 24 healthy, full term infants with no clinical signs of respiratory disease, 12 after VD and 12 after CS. Measurements were made on two occasions: 2 and 26 hours after birth. At 2 hours no differences in any measured quantity were found between the groups. The only difference found 24 hours later was that the average thoracic gas volume (TGV), was lower in infants after CS than after VD. The difference in functional residual capacity was, however, not significant. This means that the difference in TGV, previously also found by other workers, did not affect the ventilated air space. Our results do not support the theory of general inferiority in lung performance after birth in healthy, full term infants without respiratory disease delivered by CS.

Calculation of lung volume in newborn infants by means of a computer-assisted nitrogen washout method.

A clinically adapted method for the calculation of the functional residual capacity in newborn infants has been developed. The method is based on a multiple breath nitrogen washout test, during which the ventilatory air flow and the nitrogen concentration signals are sampled by a minicomputer, which also performs the calculations. The ventilatory air flow is measured by a pneumotachometer connected to a face-out volume displacement body plethysmograph, and the nitrogen concentration by a nitrogen analyzer. The functional residual capacity volume is calculated from the sampled signals by adding the expired nitrogen volumes during each expiration, and finally dividing this sum by the initial alveolar nitrogen concentration. Before the calculations, the sampled signals are adjusted regarding nitrogen analyzer delay and plethysmograph characteristics. The method presented is designed to minimize the test equipment influence on the baby's respiration and also to inhibit the necessity of pneumotachometer compensations normally connected with washout methods. Furthermore, the calculated breath-by-breath values of end-expiratory nitrogen concentration, nitrogen volume, inspired and expired tidal volume, are stored on disk for further analysis and resimulation of the test. The method has been tested on a mechanical lung model and on washouts from healthy newborn infants. The model tests indicate that the accuracy and the reproducibility of the method are good, and the results from the infants are in good agreement with previously obtained results.

Analysis of alveolar ventilation in the newborn.

Twelve healthy term infants were examined at the median ages of 2 1/2 and 26 hours. Their alveolar ventilation, efficiency of ventilation, functional residual capacity, and lung nitrogen elimination patterns were studied by means of a computerised nitrogen wash out method. The results showed that alveolar ventilation and functional residual capacity increased over the period studied. At the same time effective dead space decreased leaving minute ventilation unchanged. Distribution of ventilation did not change.

Relation between blood resistivity and hematocrit in fresh human fetal blood.

This study determined the relation between hematocrit and resistivity of fetal blood and compared it with values obtained in similar studies on adult blood. Both exponential and Maxwell-Frick-estimated relationships were calculated and compared. The results indicate that there is no significant difference between resistivity in adult and fetal blood. The best relation between blood resistivity and fetal hematocrit is obtained by using the Maxwell-Frick estimated curve calculated in the following manner: (formula: see text).