Electromagnetic inductance plethysmography to measure tidal breathing in preterm and term infants

Prediction of Tidal Volume in Newborns Through a Novel Three-Dimensional Model: A Viability Study

INTRODUCTION

Although noninvasive monitoring through quantifying rib cage movement has been useful in serial assessment of pulmonary function in newborns, measuring tidal volume (TV) is commonly performed invasively. As it is the most basic measure of pulmonary function, expanding its assessment to a noninvasive measure can contribute to clinical findings and interpretations in neonatal clinical practice.

OBJECTIVE

(1) Create a noninvasive measurement tool for TV for neonatal clinical use; (2) Evaluate the agreement between measured TV and predicted TV.

METHODS

Observational study with healthy newborns. Predicted TV was calculated based on the newborns' weight using the mid-range of the volumes usually set during mechanical ventilation of term infants (5 mL/kg). For measured TV, newborns were filmed in supine position using a digital camera, and their chest circumferences were measured with a nonelastic tape. Body markers delimited the segmentation of the area of interest, and a MATLAB software routine established their relationship with the area in cm² and generated a representative image of the thoracic and abdominal areas in a cylindrical, elliptical-based format, as well as a three-dimensional model to represent quantitative data of measured TV. Paired t-test assessed the means of measured and predicted TV, Pearson's correlation assessed level of association, and Kappa coefficient assessed the agreement between them.

RESULTS

Newborns' gestational ages ranged from 38 to 40 weeks and weights from 2190 to 4125 g. A total of 56 respiratory cycles were validated for analysis. The mean predicted TV according to weight was 5.06 mL/kg, and measured TV was 5 ml/kg (p = 0.31), with a correlation of 0.7 (p < 0.001) and a kappa coefficient of 0.39 (p = 0.01).

CONCLUSIONS

MATLAB software routine was a practical and easy-to-use tool to monitor noninvasive TV in a neonatal setting. There was no difference between predicted and estimated TV, with fair agreement between them.

Surfactant status assessment and personalized therapy for surfactant deficiency or dysfunction

Surfactant is a pivotal neonatal drug used both for respiratory distress syndrome due to surfactant deficiency and for more complex surfactant dysfunctions (such as in case of neonatal acute respiratory distress syndrome). Despite its importance, indications for surfactant therapy are often based on oversimplified criteria. Lung biology and modern monitoring provide several diagnostic tools to assess the patient surfactant status and they can be used for a personalized surfactant therapy. This is desirable to improve the efficacy of surfactant treatment and reduce associated costs and side effects. In this review we will discuss these diagnostic tools from a pathophysiological and multi-disciplinary perspective, focusing on the quantitative or qualitative surfactant assays, lung mechanics or aeration measurements, and gas exchange metrics. Their biological and technical characteristics are described with practical information for clinicians. Finally, available evidence-based data are reviewed, and the diagnostic accuracy of the different tools is compared. Lung ultrasound seems the most suitable tool for assessing the surfactant status, while some other promising tests require further research and/or development.

Tidal breathing lung function analysis of wheezing and non-wheezing infants with pneumonia: A retrospective observational study

To compare lung function in wheezing and non-wheezing infants with pneumonia through tidal breathing analysis and explore the correlation between tidal breathing lung function and clinical characteristics. This retrospective observational study included infants with pneumonia hospitalized in the Affiliated Hospital of Guizhou Medical University between January 2018 and December 2018. Medical records were used to obtain the demographic characteristics, clinical characteristics, tidal breathing lung function results before and after a bronchodilator test, and positive remission rates after the bronchodilator test for each patient. Eighty-six wheezing infants (64 males, aged 6.5 [4.8, 9] months) and 27 non-wheezing infants (18 males, aged 7 [5, 12] months) were included. Non-wheezing infants were more likely to have normal airway function compared to wheezing infants (44.4% vs 23.3%, P = .033). Peak tidal expiration flow/tidal expiratory flow (TEF)25 in wheezing infants was significantly higher than that in non-wheezing infants (162.4 [141.2, 200.7] vs 143.3 [131, 178.8], P = .037). The positive remission rate of tidal inspiratory flow (TIF50)/TEF50 (53.5% vs 29.6%, P = .03) and TEF50 (58.1% vs 33.3%, P = .024) were significantly higher in the wheezing infants compared to non-wheezing infants (P = .03 and P = .024, respectively). Furthermore, respiratory rate, tidal volume, peak expiration flow, TEF25, TEF50, and TEF75 were significantly correlated to the age, height, weight, and platelet counts of infants in both the wheezing and non-wheezing infants (all P < .05). Wheezing infants with pneumonia were more likely to have worse tidal breathing lung function compared to non-wheezing infants with pneumonia. The tidal breathing lung function parameter (respiratory rate, tidal volume, peak expiration flow, TEF25, TEF50, and TEF75) were correlated to the age, height, weight, and platelet counts of both wheezing and non-wheezing infants.

Accuracy and reliability of the optoelectronic plethysmography and the heart rate systems for measuring breathing rates compared with the spirometer

Measuring breathing rates without a mouthpiece is of interest in clinical settings. Electrocardiogram devices and, more recently, optoelectronic plethysmography (OEP) methods can estimate breathing rates with only a few electrodes or motion-capture markers placed on the patient. This study estimated and compared the accuracy and reliability of three non-invasive devices: an OEP system with 12 markers, an electrocardiogram device and the conventional spirometer. Using the three devices simultaneously, we recorded 72 six-minute epochs on supine subjects. Our results show that the OEP system has a very low limit of agreement and a bias lower than 0.4% compared with the spirometer, indicating that these devices can be used interchangeably. We observed comparable results for electrocardiogram devices. The OEP system facilitates breathing rate measurements and offers a more complete chest-lung volume analysis that can be easily associated with heart rate analysis without any synchronisation process, for useful features for clinical applications and intensive care.

Electromagnetic inductance plethysmography to study airflow after nebulized saline in bronchiolitis

BACKGROUND

Spirometric effects from therapeutic interventions in infants with severe respiratory distress cannot readily be measured, hampering development of better treatment for acute bronchiolitis. Inhaled normal saline is regularly used in these infants, with little knowledge of how this influences lung physiology.

OBJECTIVES

Assess feasibility of infant lung function testing using electromagnetic inductance plethysmography (EIP) in a clinical setting in a busy pediatric department, and explore effects from inhaled normal saline on tidal flow-volume loops in infants with acute bronchiolitis.

METHODS

Observational study conducted at the Children's Clinic, Haukeland University Hospital, Bergen, Norway during the winters 2016 and 2017, enrolling children with bronchiolitis below six months of age. EIP was performed immediately before and 5 and 20 min after saline inhalation. EIP is a noninvasive method to measure tidal breathing parameters by quantifying volume changes in the chest and abdomen during respiration. The method consists of an electromagnet/antenna and a patient vest.

RESULTS

EIP was successfully applied in 36/45 (80%) enrolled infants at mean (standard deviation) age 2.9 (2.5) months, after a hospital stay of 2.2 (1.9) days. After saline inhalation, tidal expiratory to inspiratory time ratio (Te/Ti) had increased significantly, whereas the other relevant flow/volume parameters had changed numerically in a direction compatible with a more obstructive pattern.

CONCLUSIONS

EIP could successfully be used to obtain tidal breathing parameters in infants with respiratory distress and appears a promising tool for assessment of therapeutic interventions in bronchiolitis. Saline inhalations should be used with caution as placebo in intervention studies.

Pulmonary mechanics measurements by respiratory inductive plethysmography and esophageal manometry: Methodology for infants on non-invasive respiratory support

BACKGROUND

Infants are commonly supported with non-invasive ventilation (NIV) such as nasal CPAP and high flow nasal cannula (HFNC). These modes utilize a nasal/oral interface precluding use of a traditional airway flow sensor, such as a pneumotachometer (PNT), needed for pulmonary mechanics (PM) measurements. Respiratory Inductive Plethysmography (RIP), when properly calibrated, records tidal volume non-invasively from chest wall movements. Our aim was to integrate RIP into an existing neonatal pulmonary function testing system to measure PM in infants on NIV and to compare measurements of dynamic lung compliance (CL) and resistance (RL) using RIP with those obtained using a PNT.

DESIGN/METHODS

RIP ribcage (RC) and abdominal (ABD) signals were recorded simultaneously with the flow signal from a PNT; transpulmonary pressure was estimated using an esophageal catheter. Two calibration algorithms were applied to obtain RC and ABD scaling factors.

RESULTS

Forty PM measurements were performed on 25 infants (GA 31.5±2.9 weeks; birth weight 1598±510 g; median age 7 days). Correlation coefficients for RIP- vs. PNT-based PM were r2 = 0.987 for CL and r2 = 0.997 for RL. From Bland-Altman analysis, the mean bias (±95% CI) between RIP and PNT methods was -0.004±0.021 ml/cmH2O/kg for CL and 0.7±2.9 cmH2O/(L/sec) for RL. The upper, lower limits of agreement (±95% CI) were 0.128±0.037, -0.135±0.037 ml/cmH2O/kg for CL and 18.6±5.1, -17.2±5.1 cmH2O/(L/sec) for RL.

CONCLUSION

Properly calibrated RIP may be a useful tool with sufficient diagnostic accuracy for PM measurements without need for a nasal/oral airflow sensor in infants receiving NIV.

Ventilator flow data predict bronchopulmonary dysplasia in extremely premature neonates

Early prediction of bronchopulmonary dysplasia (BPD) may facilitate tailored management for neonates at risk. We investigated whether easily accessible flow data from a mechanical ventilator can predict BPD in neonates born extremely premature (EP). In a prospective population-based study of EP-born neonates, flow data were obtained from the ventilator during the first 48 h of life. Data were logged for >10 min and then converted to flow-volume loops using custom-made software. Tidal breathing parameters were calculated and averaged from ≥200 breath cycles, and data were compared between those who later developed moderate/severe and no/mild BPD. Of 33 neonates, 18 developed moderate/severe and 15 no/mild BPD. The groups did not differ in gestational age, surfactant treatment or ventilator settings. The infants who developed moderate/severe BPD had evidence of less airflow obstruction, significantly so for tidal expiratory flow at 50% of tidal expiratory volume (TEF₅₀) expressed as a ratio of peak tidal expiratory flow (PTEF) (p=0.007). A compound model estimated by multiple logistic regression incorporating TEF₅₀/PTEF, birthweight z-score and sex predicted moderate/severe BPD with good accuracy (area under the curve 0.893, 95% CI 0.735-0.973). This study suggests that flow data obtained from ventilators during the first hours of life may predict later BPD in premature neonates. Future and larger studies are needed to validate these findings and to determine their clinical usefulness.

Lung function at term in extremely preterm-born infants: a regional prospective cohort study

OBJECTIVES

To compare lung function of extremely preterm (EP)-born infants with and without bronchopulmonary dysplasia (BPD) with that of healthy term-born infants, and to determine which perinatal characteristics were associated with lung function at term and how predictive these measurements were for later respiratory health in EP-born infants.

METHODS

Perinatal variables were recorded prospectively, and tidal breathing parameters were measured at term-equivalent age using electromagnetic inductance plethysmography. Respiratory morbidity was defined by hospital readmissions and/or treatment with asthma medications during the first year of life.

RESULTS

Fifty-two EP-born infants (mean gestational age 26¹, range 22⁶-27⁶ weeks) and 45 term-born infants were included. There was evidence of significant airway obstruction, higher tidal volumes and increased minute ventilation in the EP-born infants with and without BPD, although generally more pronounced for those with BPD. Male gender, antenatal steroids and number of days on continuous positive airway pressure were associated with lung function outcomes at term. A prediction model incorporating two unrelated tidal breathing parameters, BPD, birth weight z-score and gender, predicted respiratory morbidity in the first year of life with good accuracy (area under the curve 0.818, sensitivity and specificity 81.8% and 75.0%, respectively).

CONCLUSION

Lung function measured at term-equivalent age was strikingly abnormal in EP-born infants, irrespective of BPD. Tidal breathing parameters may be of value in predicting future pulmonary health in infants born premature.

TRIAL REGISTRATION NUMBER

NCT01150396; Results.

Electromagnetic inductance plethysmography is well suited to measure tidal breathing in infants

Reliable, accurate and noninvasive methods for measuring lung function in infants are desirable. Electromagnetic inductance plethysmography has been used to perform infant spirometry and VoluSense Pediatrics (VSP) (VoluSense, Bergen, Norway) represents an updated version of this technique. We aimed to examine its accuracy compared to a validated system measuring airflow via a facemask using an ultrasonic flowmeter.

We tested 30 infants with postmenstrual ages between 36 to 43 weeks and weights from 2.3 to 4.8 kg, applying both methods simultaneously and applying VSP alone. Agreement between the methods was calculated using Bland–Altman analyses and we also estimated the effect of applying the mask.

Mean differences for all breathing parameters were within ±5.5% and limits of agreement between the two methods were acceptable, except perhaps for peak tidal expiratory flow (PTEF). Application of the facemask significantly increased tidal volume, minute ventilation, PTEF, the ratio of inspiratory to expiratory time and the ratio of expiratory flow at 50% of expired volume to PTEF.

VSP accurately measured tidal breathing parameters and seems well suited for tidal breathing measurements in infants under treatment with equipment that precludes the use of a facemask.

Accuracy of VoluSense Pediatricshttp://ow.ly/BIFS304sheG

Basic principles of respiratory function monitoring in ventilated newborns: A review

Respiratory monitoring during mechanical ventilation provides a real-time picture of patient-ventilator interaction and is a prerequisite for lung-protective ventilation. Nowadays, measurements of airflow, tidal volume and applied pressures are standard in neonatal ventilators. The measurement of lung volume during mechanical ventilation by tracer gas washout techniques is still under development. The clinical use of capnography, although well established in adults, has not been embraced by neonatologists because of technical and methodological problems in very small infants. While the ventilatory parameters are well defined, the calculation of other physiological parameters are based upon specific assumptions which are difficult to verify. Incomplete knowledge of the theoretical background of these calculations and their limitations can lead to incorrect interpretations with clinical consequences. Therefore, the aim of this review was to describe the basic principles and the underlying assumptions of currently used methods for respiratory function monitoring in ventilated newborns and to highlight methodological limitations.

A new non-invasive method of infant spirometry demonstrates a level of repeatability that is comparable to traditional methods

AIM

The FloRight system provides novel non-invasive infant spirometry based on electromagnetic inductance plethysmography. We investigated the consistency of repeated measurements carried out in a Norwegian neonatal intensive care unit (NICU) using the system and how well these were tolerated.

METHODS

Tidal flow-volume loops were obtained from 10 preterm infants at discharge, 10 stable growing preterm infants weighing about 1500 g and 10 term-born infants. A nurse experienced with the system measured all patients before and after meals, and these measurements were repeated by nurses new to the system.

RESULTS

The measurements were well tolerated by the infants. The repeatability for the two parameters 'tidal volume' (Vt) and 'time to peak tidal expiratory flow to total expiratory time' (Tptef/Te) were relatively poor, similar to previous methods. However, the repeatability was good for the new 'flow-volume gravity mid-point' (FVg) parameter. Repeatability was better for term than preterm infants, when measurements were obtained by the experienced nurse and for measurements carried out before meals.

CONCLUSION

The FloRight system proved feasible in a NICU setting. The repeatability of the lung function measurements was similar to those reported for traditional infant spirometry. The nurse's experience and the relationship to meals appeared to be important.

Evaluation of bedside pulmonary function in the neonate: From the past to the future

Pulmonary function testing and monitoring plays an important role in the respiratory management of neonates. A noninvasive and complete bedside evaluation of the respiratory status is especially useful in critically ill neonates to assess disease severity and resolution and the response to pharmacological interventions as well as to guide mechanical respiratory support. Besides traditional tools to assess pulmonary gas exchage such as arterial or transcutaenous blood gas analysis, pulse oximetry, and capnography, additional valuable information about global lung function is provided through measurement of pulmonary mechanics and volumes. This has now been aided by commercially available computerized pulmonary function testing systems, respiratory monitors, and modern ventilators with integrated pulmonary function readouts. In an attempt to apply easy-to-use pulmonary function testing methods which do not interfere with the infant́s airflow, other tools have been developed such as respiratory inductance plethysmography, and more recently, electromagnetic and optoelectronic plethysmography, electrical impedance tomography, and electrical impedance segmentography. These alternative technologies allow not only global, but also regional and dynamic evaluations of lung ventilation. Although these methods have proven their usefulness for research applications, they are not yet broadly used in a routine clinical setting. This review will give a historical and clinical overview of different bedside methods to assess and monitor pulmonary function and evaluate the potential clinical usefulness of such methods with an outlook into future directions in neonatal respiratory diagnostics.

Accuracy of tidal breathing measurement of FloRight compared to an ultrasonic flowmeter in infants

INTRODUCTION

Monitoring breathing pattern is especially relevant in infants with lung disease. Recently, a vest-based inductive plethysmograph system (FloRight®) has been developed for tidal breathing measurement in infants. We investigated the accuracy of tidal breathing flow volume loop (TBFVL) measurements in healthy term-born infants and infants with lung disease by the vest-based system in comparison to an ultrasonic flowmeter (USFM) with a face mask. We also investigated whether the system discriminates between healthy infants and those with lung disease.

METHODS

Floright® measures changes in thoracoabdominal volume during tidal breathing through magnetic field changes generated by current-carrying conductor coils in an elastic vest. Simultaneous TBFVL measurements by the vest-based system and the USFM were performed at 44 weeks corrected postmenstrual age during quiet unsedated sleep. TBFVL parameters derived by both techniques and within both groups were compared.

RESULTS

We included 19 healthy infants and 18 infants with lung disease. Tidal volume per body weight derived by the vest-based system was significantly lower with a mean difference (95% CI) of -1.33 ml/kg (-1.73; -0.92), P < 0.001. Respiratory rate and ratio of time to peak tidal expiratory flow over total expiratory time (tPTEF/tE) did not differ between the two techniques. Both systems were able to discriminate between healthy infants and those with lung disease using tPTEF/tE.

CONCLUSION

FloRight® accurately measures time indices and may discriminate between healthy infants and those with lung disease, but demonstrates differences in tidal volume measurements. It may be better suited to monitor breathing pattern than for TBFVL measurements.

Options for assessing and measuring chest wall motion

Assessing chest wall motion is a basic and vital component in managing the child with respiratory problems, whether these are due to pathology in the lungs, airways, chest wall or muscles. Since the 1960s, clinical assessment has been supplemented with an ever-growing range of technological options for measuring chest wall motion, each with unique advantages and disadvantages. Measurements of chest wall motion can be used to: (1) Assess respiratory airflow and volume change, as a non-invasive alternative to measurement at the airway opening, (2) Monitor breathing over long periods of time, to identify apnoea and other types of sleep-disordered breathing, (3)Identify and quantify patterns of abnormal chest wall movement, whether between ribcage and abdominal components (thoracoabdominal asynchrony) or between different regions of the ribcage (eg in scoliosis and pectus excavatum). Measuring chest wall motion allows us to do things which simply cannot be done by more mainstream respiratory function techniques measuring flow at the airway opening: it allows respiratory airflow to be measured when it would otherwise be impossible, and it tells us how the different parts of the chest wall (eg ribcage vs abdomen, right vs left) are moving in order to generate that airflow. The basis of the different techniques available to assess and measure chest wall motion will be reviewed and compared, and their relevance to paediatric respiratory practice assessed.

Tidal breathing in preterm infants receiving and weaning from continuous positive airway pressure

OBJECTIVE

To compare tidal breathing on different continuous positive airway pressure (CPAP) devices and pressures and to serially measure tidal breathing during weaning off CPAP using electromagnetic inductive plethysmography.

STUDY DESIGN

Using electromagnetic inductive plethysmography, tidal breathing was measured in 29 preterm infants receiving CPAP, gestational age 28 ± 2 weeks. Variable-flow nasal CPAP (nCPAP), bubble CPAP (bCPAP) at pressures of 5, 7, and 9 cmH2O, nasal bi-level positive airway pressure (nBiPAP) system at pressures of 5, 7/5, and 9/5 cmH2O, and unsupported breathing were studied. Twenty-one infants had weekly tidal breathing measurements on and off nCPAP.

RESULTS

Minute volume (MV/kg) was similar between all devices (0.30-0.33 L/kg/min). On bCPAP, weight corrected tidal volume (VT/kg) was the least, changing little with increasing pressures. On nCPAP and nBiPAP, VT/kg increased with increasing pressure and the respiratory rate (fR) decreased. The delivered pressure varied slightly from the set pressure being most dissimilar on nBiPAP and similar on bCPAP. Compared with unsupported breathing, all devices decreased VT/kg, MV/kg, and phase angle, but did not alter fR. Serial tidal breathing measurements showed decreasing difference for VT/kg over time on and off nCPAP.

CONCLUSIONS

At different pressure settings, on all CPAP devices the measured MV/kg was similar either through increasing VT/kg and decreasing fR (nCPAP and nBiPAP) or maintaining both (bCPAP). Serial tidal breathing measurements may aid weaning from CPAP.

Asthma across the ages: knowledge gaps in childhood asthma

The Eunice Kennedy Shriver National Institute of Child Health and Human Development convened an Asthma Group in response to the Best Pharmaceuticals for Children Act. The overall goal of the Best Pharmaceuticals for Children Act Program is to improve pediatric therapeutics through preclinical and clinical drug trials that lead to drug-labeling changes. Although significant advances have been made in the understanding and management of asthma in adults with appropriately labeled medications, less information is available on the management of asthma in children. Indeed, many medications are inadequately labeled for use in children. In general, the younger the child, the less information there is available to guide clinicians. Because asthma often begins in early childhood, it is incumbent on us to continue to address the primary questions raised in this review and carefully evaluate the medications used to manage asthma in children. Meanwhile, continued efforts should be made in defining effective strategies that reduce the risk of exacerbations. If the areas of defined need are addressed in the coming years, namely prevention of exacerbations and progression of disease, as well as primary intervention, we will see continuing reduction in asthma mortality and morbidity along with improved quality of life for children with asthma.