Published clinical studies 

Bentsen M., Clemm H., Vollsæter M., Gudmundsdottir H., Lønning L., Markestad T., Halvorsen T. Repeatability of non-invasive infant spirometry. In: Thematic Poster
Session : Respiratory physiology and sleep disordered breathing in children. Germany: European Respiratory Society; 2014.

Introduction: Measuring lung function in infants is important but challenging. A new inductance plethysmographic technique has been developed, with measurements obtained from a baby-vest with thin metal wires in the fabric and signals derived from changes in the electromagnetic field created by respiratory movements (Volusense™). The flow variables are comparable to those produced by airflow measured at the mouth. Aim:  To investigate repeatability of this method.  Methods: Thirty infants were studied in the neonatal intensive care unit (NICU) at Haukeland University Hospital, Norway. Minimum 5 minutes of tidal breathing were recorded. The recordings were performed by two nurses (A and B) before and after a meal, and data were analyzed independently by two pediatricians.  Results: Ten healthy term-born infants (3.6 kg), ten preterm infants ready for discharge (2.3 kg) and ten preterm infants still under NICU care (1.5 kg) were examined. Tidal breathing parameters measured by Nurse A vs. Nurse B did not differ: Time to peak tidal expiratory flow to total expiratory time (Tptef/Te) 42.5 (95%CI: 37.4, 47.7) vs. 40.1 (95%CI: 34.2, 46.0), p=0.34. Selection of breath cycles for analyses by the two pediatricians did not influence recordings: Tptef/Te 39.8 (95%CI: 37.6, 42.0) vs. 39.5 (95%CI 37.4, 41.7), p=0.56. Inter observer repeatability for nurse A was adequate and measurements obtained before and after a meal were similar.  Conclusion: Within and between observer repeatability of tidal breathing measurements obtained with inductance plethysmography were adequate and comparable to that obtained with more complex methods. Analyses were not influenced by meals or by who selected the breath cycles.

Wertheim D., Williams E.M., Pickerd N., Kotecha S. Analysis of tidal volume changes in preterm infants. In: Thematic Poster
Session : Respiratory physiology and sleep disordered breathing in children. Germany: European Respiratory Society; 2014.

Assessment of tidal volume using the volume waveform relies on detection of the maximum peak and minimum trough. A possible alternative could be the calculation of a function of the mean of the squared amplitude such as the root of the mean squared amplitude (rms); this type of calculation may be less dependent on the extreme points of the volume waveform. The aim of this study was to compare assessment of rms with tidal volume. A FloRight* system (Volusense AS, Oslo, Norway) was used to assess respiration volume (Pickerd et al. J Pediatr 2014). Recordings of 15 minutes or less on seven preterm infants of post-conceptional age 29 to 39 weeks (median 30 weeks) were analysed; in these recordings the babies were receiving SiPaP (Carefusion Corporation, UK) respiratory support at pressures of 5 or 9/5 cmH2O. Raw data were low pass and high pass filtered and analysed using software that we developed using MATLAB (The MathWorks, Inc., USA). In each recording, one epoch of 60 seconds duration was analysed. The epoch chosen was the first where there were no respiratory pauses and the respiratory pattern visually appeared regular; epochs with clear artefact were excluded. For six of the seven infants there was an increase in rms volume amplitude associated with change in pressure to 9/5 cmH2O although the degree was variable. Tidal volume was assessed visually and compared with calculation of rms volume. The data were tested for consistency with a normal distribution. Using the Pearson's correlation coefficient there was a significant relation between tidal volume and rms volume (r= 0.98, p<0.001, n= 14). These results suggest that rms amplitude may help to assess changes in tidal volume.

Petrus C.M., Thamrin C., Fuchs O., Frey U. Accuracy of tidal breathing measurement of floright compared to an ultrasonic flowmeter in infants. Pediatr. Pulmonol 2014. doi: 10.1002/ppul.23006

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. 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. 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. 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.

Pickerd N, Williams EM, Watkins, WJ, Kotecha S. Tidal breathing in preterm infants receiving and weaning from continuous positive airway pressure. J. Peds. 2014. doi:10.1016/j.jpeds.2013.12.049.

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. 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. 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. 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.

Pickerd N, Williams EM, Kotecha S. Electromagnetic inductance plethysmography to measure tidal breathing in preterm and term infants. Pediatr. Pulmonol. 2013. doi: 10.1002/ppul.22584

Tidal breathing measurements which provide a non-invasive measure of lung function in preterm and term infants are particularly useful to guide respiratory support. We used a new technique of electromagnetic inductance plethysmography (EIP) to measure tidal breathing in infants between 32 and 42 weeks postconceptional age (PCA). Tidal breathing was measured in 49 healthy spontaneously breathing infants between 32 and 42 weeks PCA. The weight-corrected tidal volume (V(T) ) and minute volume (MV) decreased with advancing PCA (V(T) 6.5 ± 1.5 ml/kg and MV 0.44 ± 0.04 L/kg/min at 32-33 weeks, respectively; 6.3 ± 0.9 ml/kg and 0.38 ± 0.02 L/kg/min at 34-36 weeks; and 5.1 ± 1.1 ml/kg and 0.28 ± 0.02 L/kg/min at term, V(T) P < 0.001 and MV P < 0.01 for 32-33 weeks PCA vs. term; V(T) P = 0.016 and MV P = 0.015 for 34-36 weeks PCA vs. term). Respiratory frequency and the phase angle decreased significantly with advancing PCA but the flow parameter t(PTEF) /t(E) did not change significantly. Using a new technique to measure tidal breathing parameters in newborn infants, our data confirms its usability in clinical practice and establishes normative data which can guide future respiratory management of newborn infants.

Williams EM, Pickerd N, Eriksen M, Øygarden K, Kotecha S. Estimation of tidal ventilation in preterm and term newborn infants using electromagnetic inductance plethysmography. Physiol Meas. 2011;32(11):1833–1845.

Tidal volume (VT) measurements in newborn infants remain largely a research tool. Tidal ventilation and breathing pattern were measured using a new device, FloRight*, which uses electromagnetic inductive plethysmography,and compared simultaneously with pneumotachography in 43 infants either receiving no respiratory support or continuous positive airway pressure (CPAP).Twenty-three infants were receiving CPAP (gestational age 28 ± 2 weeks, mean ± SD) and 20 were breathing spontaneously (gestational age 34 ± 4 weeks). The two methods were in reasonable agreement, with VT (r2 = 0.69) ranging from 5 to 23 ml (4–11 ml kg−1) with a mean difference of 0.4 ml and limit of agreement of −4.7 to + 5.5 ml. For respiratory rate, minute ventilation,peak flow and breathing pattern indices, the mean difference between the two methods ranged between 0.7% and 5.8%. The facemask increased the respiratory rate (P < 0.001) in both groups with the change in VT being more pronounced in the infants receiving no respiratory support. Thus, FloRight provides an easy to use technique to measure term and preterm infants in the clinical environment without altering the infant's breathing pattern.

Kent S, Olden C, Rabe H, Seddon P.Validity of volumetric vest respiratory measurements in preterm infants with changes in posture. In: Thematic Poster Session : New Insights in paediatric respiratory physiology. Netherlands: European Respiratory Society; 2011.

Respiratory measurements in unsedated infants are problematic: applying a face mask causes arousal and changes respiratory pattern. We have previously validated a volumetric vest system (FloRight*) in normal newborn infants. However, other calibrated chest wall measurements (eg Respitrace) lose validity if posture or chest shape changes. In order to assess whether this system remained valid with chest distortion and changes in posture, we measured tidal breathing in 11 preterm infants (median 30 weeks at birth) simultaneously by mask/ultrasonic flowmeter and Floright, both in supine (S) and randomised right or left lateral position (L). The following tidal breathing parameters were compared over 20 breaths of stable breathing in quiet sleep: tidal volume (Vt), timing of peak tidal expiratory flow (tPTEF/tE) and expiratory:inspiratory time ratio (tE/tI). FloRight measurements were closely correlated with mask measurements in both S and L: Vt S r=0.99, L r=0.99; tPTEF/tE 0.94 and 0.96, tE/tI 0.97 and 0.96. FloRight Vt measurements were slightly but significantly higher than mask, both in S (+2ml, p=0.02) and L (+4ml, p=0.001) but tPTEF/tE and tE/tI measurements were not significantly different. FloRight accurately measures tidal flow timing parameters in small preterm infants both in supine and lateral posture. Tidal volume measurements are highly correlated but slightly overestimated compared to mask, especially in lateral lying: this could be due to the vest not fully conforming to chest distortion.

Olden C, Symes E, Seddon P. Measuring tidal breathing parameters using a volumetric vest in neonates with and without lung disease. Pediatr. Pulmonol. 2010;45(11):1070–1075.

Lung function measurement is difficult in unsedated infants; tidal breathing parameters are a useful non-invasive surrogate, but even these measurements cause disturbance from applying a facemask. We investigated a novel volumetric vest system (FloRight*), which measures volume changes of the respiratory system from changes in the magnetic fields induced by current-carrying coils around the entire chest and abdomen. Using a facemask and ultrasonic flowmeter as comparator, we assessed the validity and repeatability of tidal breathing parameters measured by FloRight in 10 healthy newborn infants during natural sleep. We also assessed the effect of a facemask on tidal volume and tidal expiratory flow parameters. To assess the ability of the FloRight system to detect disease, we compared the healthy infants with 11 infants suffering from bronchopulmonary dysplasia. Tidal parameters with the FloRight vest corresponded closely with facemask measurements. Mean difference, mask minus vest, for tidal volume was 0.096 ml (P < 0.05), with limits of agreement +4.5 to -4.3 ml. Coefficient of repeatability was similar for mask and vest measurements. Tidal volume measured by FloRight with mask in place (20.6 ml) was significantly higher than without mask (16.1 ml), but tidal expiratory flow parameters were not altered. FloRight measurements of tidal parameters were markedly different between the two groups of infants, with tidal volume per Kg significantly higher and tidal expiratory flow parameters significantly lower. Our findings suggest that the FloRight system is able to measure tidal breathing parameters accurately, in healthy newborn infants, without prior calibration on the infant. It appears to have at least sufficient sensitivity to detect severe respiratory disease.

Walter K, Olden C, Symes E, Seddon P. Discrimination between neonates with and without lung disease using a volumetric vest system. In: Thematic Poster Session : Paediatric and neonatal intensive care. Spain: European Respiratory Society; 2010. 

Tidal breathing parameters are a non-invasive surrogate for infant lung function measurement, but usefulness is limited by variability and the need to apply a facemask. Only T PTEF /TE has been widely studied in infants; other parameters have been proposed. We have recently validated a novel volumetric vest system (FloRight*) for measuring not only a range of tidal breathing parameters but also thoraco-abdominal asynchrony (TAA). To assess the potential of tidal breathing parameters and TAA to detect lung disease in neonates, we measured both repeatability and ability to discriminate between healthy term newborns (N) and preterm infants with bronchopulmonary dysplasia (BPD). We collected 2 periods of tidal breathing in 10 N and 11 BPD infants during quiet sleep and analysed two 20-breath segments of stable tidal breathing for each baby. The vest system not only allows to distinguish between infants with and without lung disease in several tidal breathing parameters but also detects functional differences such as TAA measured by φ.

Olden C, Seddon P. Measuring Tidal Breathing Parameters Using a Volumetric Vest in Newborn Infants. In: Thematic Poster Session, Pediatric pulmonary measurement techniques and basic studies. San Francisco, California, US: American Thoracic Society; 2007. 

Tidal breathing parameters have been used as non-invasive markers of lung function in infants, but measuring them with minimal disturbance is problematic. Usually airflow is measured via a face mask, but this causes arousal, is poorly tolerated in infants with lung disease, and adds deadspace. Respiratory inductance plethysmography is posture-dependent and requires calibration with face mask measurements if absolute tidal volumes are needed. We assessed a novel device (FloRight*, Volusense, Kongsvinger, Norway) which uses a continuous coil in a vest worn over chest and abdomen, carrying a weak alternating current, and an external magnetic field sensor. Changes in volume of the respiratory system are measured by changes in the external magnetic field generated. We aimed to assess whether tidal parameters measured by the Volusense system were equivalent to those measured directly by face mask airflow, and to assess the effect on tidal parameters of having a face mask in place. 10 newborn infants had simultaneous measurements of tidal breathing parameters -tidal volume (VT) and time to peak tidal expiratory flow as a proportion of expiratory time (TPTEF/TE) - a) by measuring flow through a face mask (Msk) and b) by measuring volume changes via vest (Vst). Tidal parameters were also measured by Vst with the mask removed. Mean (SD) VT measured by Vst was 19.8ml (4.7) and by Msk was 19.9ml (5.3) - no significant difference. Mean difference (limits of agreement) was 0.096ml (+4.5 to -4.3). Mean (SD) TPTEF/TE by Vst was 0.51 (0.15); by Msk 0.50 (0.09) - mean difference (limits) -0.01 (+0.32 to -0.35). VT by Vst with mask in place - 20.6 (4.1) was significantly higher than without mask - 16.1 (3.8), but TPTEF/TE did not change significantly. Tidal parameters can be accurately measured using this system without the need for volume calibration. As expected, presence of a facemask increases tidal volume but does not significantly alter TPTEF/TE.

 

* VoluSense Pediatrics has replaced FloRight as a trade name.