Bengt Arne Sjöqvist

Calculation of Lung Volume in Newborn Infants by Means of a Computer-assisted Nitrogen Washout Method

ABSTRACT. 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 babys 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.

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

ABSTRACT: 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.

Method for analysing multiple-breath nitrogen washouts.

A method of analysing multiple-breath nitrogen washouts is described and discussed. The method is objective and introduces no weighting into the results. The necessary raw data are obtained from a computer-assisted nitrogen washout test. During the analysis, objective parameters which characterise the alveolar ventilation in terms of nitrogen elimination pattern and gas-mixing efficiency are calculated, together with estimates of functional residual capacity (FRC), tidal volume, dead space, and effective part of the tidal volume. The elimination pattern is described through linear fitting of exponential models to the obtained washout course and is performed by using the z-transform. The dead space and the effective part of the tidal volume are estimated from a gas-mixing model. The applied estimation procedure difines a dead space which is larger than the corresponding single-breath dead space and has been designated ‘effective dead space’. The gas-mixing efficiency is described by two indices, one describing the efficiency within an idealised breath and the other the overall efficiency of the lungs. The calculation algorithms are fast and the results are easy to interpret, which makes the method suitable for clinical online applications. The method has been evaluated in a group of 24 healthy newborns at about 26 hours of age, but the application is not restricted to this category of patient.

A randomized controlled study about the use of eHealth in the home health care of premature infants

BackgroundOne area where the use of information and communication technology (ICT), or eHealth, could be developed is the home health care of premature infants. The aim of this randomized controlled study was to investigate whether the use of video conferencing or a web application improves parents’ satisfaction in taking care of a premature infant at home and decreases the need of home visits. In addition, nurses’ attitudes regarding the use of these tools were examined.MethodThirty-four families were randomized to one of three groups before their premature infant was discharged from the hospital to home health care: a control group receiving standard home health care (13 families); a web group receiving home health care supplemented with the use of a web application (12 families); a video group with home health care supplemented with video conferencing using Skype (9 families). Families and nursing staff answered questionnaires about the usefulness of ICT. In addition, semi-structured interviews were conducted with 16 families.ResultsAll the parents in the web group found the web application easy to use. 83% of the families thought it was good to have access to their child’s data through the application. All the families in the video group found Skype easy to use and were satisfied with the video calls. 88% of the families thought that video calls were better than ordinary phone calls. 33% of the families in the web group and 75% of those in the video group thought the need for home visits was decreased by the web application or Skype. 50% of the families in the web group and 100% of those in the video group thought the web application or the video calls had helped them feel more confident in caring for their child. Most of the nurses were motivated to use ICT but some were reluctant and avoided using the web application and video conferencing.ConclusionThe families were satisfied with both the web application and video conferencing. The families readily embraced the use of ICT, whereas motivating some of the nurses to accept and use ICT was a major challenge.

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).

Attitudes among healthcare professionals towards ICT and home follow-up in chronic heart failure care

BackgroundeHealth applications for out-of-hospital monitoring and treatment follow-up have been advocated for many years as a promising tool to improve treatment compliance, promote individualized care and obtain a person-centred care. Despite these benefits and a large number of promising projects, a major breakthrough in everyday care is generally still lacking. Inappropriate organization for eHealth technology, reluctance from users in the introduction of new working methods, and resistance to information and communication technology (ICT) in general could be reasons for this. Another reason may be attitudes towards the potential in out-of-hospital eHealth applications. It is therefore of interest to study the general opinions among healthcare professionals to ICT in healthcare, as well as the attitudes towards using ICT as a tool for patient monitoring and follow-up at home. One specific area of interest is in-home follow-up of elderly patients with chronic heart failure (CHF). The aim of this paper is to investigate the attitudes towards ICT, as well as distance monitoring and follow-up, among healthcare professionals working with this patient group.MethodThis paper covers an attitude survey study based on responses from 139 healthcare professionals working with CHF care in Swedish hospital departments, i.e. cardiology and medicine departments. Comparisons between physicians and nurses, and in some cases between genders, on attitudes towards ICT tools and follow-up at home were performed.ResultsOut of the 425 forms sent out, 139 were collected, and 17 out of 21 counties and regions were covered in the replies. Among the respondents, 66% were nurses, 30% physicians and 4% others. As for gender, 90% of nurses were female and 60% of physicians were male. Internet was used daily by 67% of the respondents. Attitudes towards healthcare ICT were found positive as 74% were positive concerning healthcare ICT today, 96% were positive regarding the future of healthcare ICT, and 54% had high confidence in healthcare ICT. Possibilities for distance monitoring/follow-up are good according to 63% of the respondents, 78% thought that this leads to increased patient involvement, and 80% thought it would improve possibilities to deliver better care. Finally, 72% of the respondents said CHF patients would benefit from home monitoring/follow-up to some extent, and 19% to a large extent. However, the best method of follow-up was considered to be home visits by nurse, or phone contact.ConclusionThe results indicate that a majority of the healthcare professionals in this study are positive to both current and future use of ICT tools in healthcare and home follow-up. Consequently other factors have to play an important role in the slow penetration of out-of-hospital eHealth applications in daily healthcare practice.

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.

On scene injury severity prediction (OSISP) algorithm for car occupants

Many victims in traffic accidents do not receive optimal care due to the fact that the severity of their injuries is not realized early on. Triage protocols are based on physiological and anatomical criteria and subsequently on mechanisms of injury in order to reduce undertriage. In this study the value of accident characteristics for field triage is evaluated by developing an on scene injury severity prediction (OSISP) algorithm using only accident characteristics that are feasible to assess at the scene of accident. A multivariate logistic regression model is constructed to assess the probability of a car occupant being severely injured following a crash, based on the Swedish Traffic Accident Data Acquisition (STRADA) database. Accidents involving adult occupants for calendar years 2003-2013 included in both police and hospital records, with no missing data for any of the model variables, were included. The total number of subjects was 29128, who were involved in 22607 accidents. Partition between severe and non-severe injury was done using the Injury Severity Score (ISS) with two thresholds: ISS>8 and ISS>15. The model variables are: belt use, airbag deployment, posted speed limit, type of accident, location of accident, elderly occupant (>55 years old), sex and occupant seat position. The area under the receiver operator characteristic curve (AUC) is 0.78 and 0.83 for ISS>8 and ISS>15, respectively, as estimated by 10-fold cross-validation. Belt use is the strongest predictor followed by type of accident. Posted speed limit, age and accident location contribute substantially to increase model accuracy, whereas sex and airbag deployment contribute to a smaller extent and seat position is of limited value. These findings can be used to refine triage protocols used in Sweden and possibly other countries with similar traffic environments.

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

Summary: 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:ρ = 53.0(1 + χ · h)/(1 - h)whereχ = 1.2h = H/100 (H = hematocrit).Speculation: Hematocrit varies over a wide range during the newborn period. Accurate knowledge of resistivity-hematocrit relationships over the entire hematocrit range is essential whenever blood resistivities are to be estimated from hematocrit values. This study reveals that a better correlation is obtained when using the Maxwell-Frick model instead of the ordinary exponential model. Thus, a tool is offered to improve the accuracy of the impedance cardiography method in newborns.

Effects of Delivery by Caesarean Section on Lung Function in Healthy Newborn Infants

ABSTRACT. 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.