Rachel Wilson

Measuring changes in chest wall motion after lung resection using structured light plethysmography: a feasibility study

OBJECTIVES We describe the use of structured light plethysmography (SLP)-a novel, non-contact, light-based technique for measuring tidal breathing-among a cohort of patients undergoing lung resection. In this feasibility study, we examined whether changes in chest wall motion or in asynchrony between regions of the thoraco-abdominal wall could be identified after surgery. METHODS Fifteen patients underwent wedge resection (n = 8) or lobectomy (n = 7). All patients underwent two SLP assessments (before surgery and on Day 1 post-surgery). Each assessment captured data during 5 min of quiet (tidal) breathing. RESULTS When data were averaged across all patients, motion on the operated side of the thorax was significantly reduced after surgery (mean change from presurgery ± standard deviation: -14.7 ± 16.5%, P = 0.01), while motion on the non-operated side increased (15.9 ± 18.5%, P = 0.01). Thoraco-abdominal asynchrony also increased (mean change ± standard deviation: 43.4 ± 55.1%, P = 0.01), but no significant difference was observed in right-left hemi-thoracic asynchrony (163.7 ± 230.3%, P = 0.08). When analysed by resection type, lobectomy was associated with reduced and increased motion on the operated and non-operated side, respectively, and with an increase in both right-left hemi-thoracic and thoraco-abdominal asynchrony. No significant changes in motion or asynchrony were identified in patients who underwent wedge resection. CONCLUSIONS SLP was able to detect changes in chest wall motion and asynchrony after thoracic surgery. Changes in this small group of patients were consistent with the side of the incision and were most apparent in patients undergoing lobectomy.

Evaluation of the agreement of tidal breathing parameters measured simultaneously using pneumotachography and structured light plethysmography

Structured light plethysmography (SLP) is a noncontact, noninvasive, respiratory measurement technique, which uses a structured pattern of light and two cameras to track displacement of the thoraco–abdominal wall during tidal breathing. The primary objective of this study was to examine agreement between tidal breathing parameters measured simultaneously for 45 sec using pneumotachography and SLP in a group of 20 participants with a range of respiratory patterns (“primary cohort”). To examine repeatability of the agreement, an additional 21 healthy subjects (“repeatability cohort”) were measured twice during resting breathing and once during increased respiratory rate (RR). Breath‐by‐breath and averaged RR, inspiratory time (tI), expiratory time (tE), total breath time (tTot), tI/tE, tI/tTot, and IE50 (inspiratory to expiratory flow measured at 50% of tidal volume) were calculated. Bland–Altman plots were used to assess the agreement. In the primary cohort, breath‐by‐breath agreement for RR was ±1.44 breaths per minute (brpm). tI, tE, and tTot agreed to ±0.22, ±0.29, and ±0.32 sec, respectively, and tI/tE, tI/tTot, and IE50/IE50SLP to ±0.16, ±0.05, and ±0.55, respectively. When averaged, agreement for RR was ±0.19 brpm. tI, tE, and tTot were within ±0.16, ±0.16, and ±0.07 sec, respectively, and tI/tE, tI/tTot, and IE50 were within ±0.09, ±0.03, and ±0.25, respectively. A comparison of resting breathing demonstrated that breath‐by‐breath and averaged agreements for all seven parameters were repeatable (P > 0.05). With increased RR, agreement improved for tI, tE, and tTot (P ≤ 0.01), did not differ for tI/tE, tI/tTot, and IE50 (P > 0.05) and reduced for breath‐by‐breath (P < 0.05) but not averaged RR (P > 0.05).

Tidal breathing patterns derived from structured light plethysmography in COPD patients compared with healthy subjects

Purpose Differences in tidal breathing patterns have been reported between patients with chronic obstructive pulmonary disease (COPD) and healthy individuals using traditional measurement techniques. This feasibility study examined whether structured light plethysmography (SLP) – a noncontact, light-based technique – could also detect differences in tidal breathing patterns between patients with COPD and healthy subjects. Patients and methods A 5 min period of tidal (quiet) breathing was recorded in each patient with COPD (n=31) and each healthy subject (n=31), matched for age, body mass index, and sex. For every participant, the median and interquartile range (IQR; denoting within-subject variability) of 12 tidal breathing parameters were calculated. Individual data were then combined by cohort and summarized by its median and IQR. Results After correction for multiple comparisons, inspiratory time (median tI) and its variability (IQR of tI) were lower in patients with COPD (p<0.001 and p<0.01, respectively) as were ratios derived from tI (tI/tE and tI/tTot, both p<0.01) and their variability (p<0.01 and p<0.05, respectively). IE50SLP (the ratio of inspiratory to expiratory flow at 50% tidal volume calculated from the SLP signal) was higher (p<0.001) in COPD while SLP-derived time to reach peak tidal expiratory flow over expiratory time (median tPTEFSLP/tE) was shorter (p<0.01) and considerably less variable (p<0.001). Thoraco–abdominal asynchrony was increased (p<0.05) in COPD. Conclusion These early observations suggest that, like traditional techniques, SLP is able to detect different breathing patterns in COPD patients compared with subjects with no respiratory disease. This provides support for further investigation into the potential uses of SLP in assessing clinical conditions and interventions.

Tidal breathing parameters measured using structured light plethysmography in healthy children and those with asthma before and after bronchodilator

Structured light plethysmography (SLP) is a light‐based, noncontact technique that measures tidal breathing by monitoring displacements of the thoracoabdominal (TA) wall. We used SLP to measure tidal breathing parameters and their within‐subject variability (v) in 30 children aged 7–16 years with asthma and abnormal spirometry (forced expiratory volume in 1 sec [FEV1] <80% predicted) during a routine clinic appointment. As part of standard care, the reversibility of airway obstruction was assessed by repeating spirometry after administration of an inhaled bronchodilator. In this study, SLP was performed before and after bronchodilator administration, and also once in 41 age‐matched controls. In the asthma group, there was a significant increase in spirometry‐assessed mean FEV1 after administration of bronchodilator. Of all measured tidal breathing parameters, the most informative was the inspiratory to expiratory TA displacement ratio (IE50SLP, calculated as TIF50SLP/TEF50SLP, where TIF50SLP is tidal inspiratory TA displacement rate at 50% of inspiratory displacement and TEF50SLP is tidal expiratory TA displacement rate at 50% of expiratory displacement). Median (m) IE50SLP and its variability (vIE50SLP) were both higher in children with asthma (prebronchodilator) compared with healthy children (mIE50SLP: 1.53 vs. 1.22, P < 0.001; vIE50SLP: 0.63 vs. 0.47, P < 0.001). After administration of bronchodilators to the asthma group, mIE50SLP decreased from 1.53 to 1.45 (P = 0.01) and vIE50SLP decreased from 0.63 to 0.60 (P = 0.04). SLP‐measured tidal breathing parameters could differentiate between children with and without asthma and indicate a response to bronchodilator.

Tidal breathing parameters measured by structured light plethysmography in children aged 2–12 years recovering from acute asthma/wheeze compared with healthy children

Measurement of lung function can be difficult in young children. Structured light plethysmography (SLP) is a novel, noncontact method of measuring tidal breathing that monitors displacement of the thoraco–abdominal wall. SLP was used to compare breathing in children recovering from an acute exacerbation of asthma/wheeze and an age‐matched cohort of controls. Children aged 2–12 years with acute asthma/wheeze (n = 39) underwent two 5‐min SLP assessments, one before bronchodilator treatment and one after. SLP was performed once in controls (n = 54). Nonparametric comparisons of patients to healthy children and of pre‐bronchodilator to post‐bronchodilator were made for all children, and also stratified by age group (2–5 vs. 6–12 years old). In the asthma/wheeze group, IE50SLP (inspiratory to expiratory flow ratio) was higher (median 1.47 vs. 1.31; P = 0.002), thoraco–abdominal asynchrony (TAA) and left–right asynchrony were greater (both P < 0.001), and respiratory rate was faster (P < 0.001) than in controls. All other timing indices were shorter and displayed reduced variability (all P < 0.001). Variability in time to peak inspiratory flow was also reduced (P < 0.001). Younger children showed a greater effect than older children for TAA (interaction P < 0.05). After bronchodilator treatment, the overall cohort showed a reduction in within‐subject variability in time to peak expiratory flow only (P < 0.001). Younger children exhibited a reduction in relative contribution of the thorax, TAA, and variability in TAA (interaction P < 0.05). SLP can be successfully performed in young children. The potential of SLP to monitor diseases such as asthma in children is worthy of further investigation. ClinicalTrials.gov identifier: NCT02543333.

P37 Preliminary normal values for structured light plethysmography tidal breathing parameters and age and gender differences

Introduction This is the first report from an ongoing study to define normal values for Structured Light Plethysmography (SLP) tidal breathing parameters in adults. Structured Light Plethysmography (SLP) is a non-contact, non-invasive respiratory measurement technology that utilises the movement of thoraco-abdominal (TA) wall to measure a range of tidal breathing parameters. Various studies have been using SLP but lack of normative values can make any clinical judgement difficult. Methods :As a part of an on-going collaboration between PneumaCare Ltd. and Queen Elizabeth (QE) Hospital (Birmingham, UK), 107 healthy adult subjects between ages of 18 to 69 were measured with SLP during 4 to 5 minutes of seated tidal breathing. Parameter means and standard deviations for males and females aged 18–39 and 40–69 were calculated and gender and age related comparisons were made (t-test). Results Tables 1 summarises the normative values for males and females older and younger than 40 years. Three parameters showed age related differences and one parameter showed a gender related difference. Conclusion Preliminary normal values for SLP derived tidal breathing parameters are reported. Some gender and age related differences are apparent. It is interesting that tPTEF/tE was significantly lower in the older participants, possibly a sign of natural airway obstruction associated with age. Abstract P37 Table 1 SLP Tidal Breathing Parameters for adult male and female normals aged 18–69 years Parameter Males 18–39 yrs (n = 32) Mean±SD Males 40–69 yrs (n = 25) Mean ± SD Young vs older males, t (p) Females 18–39 (n = 21) Mean ± SD Females 40–69 yrs (n = 29) Mean ± SD Young vs older Females, t (p) Males vs. Females (all ages), t (p) TAA 5.7 ± 23.3 4.75 ± 2.69 1.18 (0.24) 4.85 ± 2.45 4.8 ± 1.83 0.08 (0.94) 0.92 (0.36) LRHTA 2.24 ± 2.13 2.39 ± 1.64 −0.298 (0.77) 1.58 ± 0.69 2.04 ± 1.43 −1.36 (0.18) 1.47 (0.14) %RC 45.87 ± 13.07 56.29 ± 11.03 −3.2(<0.01) 60.23 ± 8.55 61.31 ± 10.33 −0.39 (0.70) −4.62(<0.001) IE50 1.34 ± 0.27 1.25 ± 0.18 1.48 (0.14) 1.37 ± 0.2 1.42 ± 0.29 −0.64 (0.52) −1.94 (0.06) tPTEF/tE 0.34 ± 0.09 0.26 ± 0.07 3.67(<0.001) 0.32 ± 0.09 0.26 ± 0.06 2.62(<0.05) 0.91 (0.36) tPTIF/tI 0.49 ± 0.09 0.55 ± 0.09 −2.69(<0.01) 0.5 ± 0.08 0.52 ± 0.07 0.88 (0.38) −1.13 (0.26) TAA: Thoraco-abdominal asynchrony (TAA), LRHTA:left vs Right Hemi-thoracic asynchrony, IE50:Inspiratory to expiratory flow at 50% of tidal volume calculated from thoraco-abdominal wall displacement, tPTEF/tE: normalised time to reach peak tidal expiratory flow, tPTIF/tI: normalised time to reach peak tidal inspiratory flow

P38 Repeatability of structured light plethysmography (slp) for measurement of respiratory rate in normal subjects

Introduction Structured Light Plethysmography (SLP) captures movements of a light grid projected onto the thoraco-abdominal (TA) wall to produce a waveform from which a primary derived output is Respiratory Rate (RR). Assessment of repeatability is essential for clinical use, however, physiological variability can confound results. RR agrees within ± 2 breaths per minute (brpm)1 with Respiratory Inductance Plethysmography (RIP) measured simultaneously on one occasion. We propose that if measurements are repeatable, there would be no difference in agreement between devices over a series of sessions. Aim This study assessed repeatability of the agreement between SLP and RIP. Methods 14 subjects (7 male, 7 female) with no respiratory diagnosis underwent 5 minutes of simultaneous measurement with SLP and RIP during quiet breathing. This was repeated on 3 occasions over 2 days, by the same operator, at the same location and using the same devices. RR were calculated for thorax ( THRR), abdomen (ABRR) and the entire thoraco-abdominal (TARR) signals for both devices. Agreement between the two devices was assessed using Bland-Altman plots with LOA set at < ± 2 breaths/min. Results For TARR and THRR, all points were within 2 SD of the mean; for ABRR, 1 of 14 points was outside of 2 SD, but the LOA were within < ± 2 breaths/min. The mean differences between the two devices were 0.476, 0.605 and 0.524 breaths/min for TARR, THRR and ABRR, respectively. Conclusion Agreement was observed between the two devices for each set of repeated measurements. We conclude that measurement of RR are repeatable. Reference Iles R, et al. American Thoracic Society Meeting 2014,A2935.

Spirometric and structured light plethysmography derived measures of airflow obstruction in asthma

Introduction: Accurate diagnosis and monitoring of respiratory disease are important for breathing assessment. Conventional lung function techniques such as spirometry are challenging in young children, requiring their full cooperation. Structured Light Plethysmography (SLP) derives tidal breathing measures from thoraco-abdominal (TA) displacement in a non-contact environment. We have shown that IE50 SLP (ratio of inspiratory to expiratory TA displacement rate at 50% of TA displacement) measured by SLP is greater in asthmatic children with airflow obstruction than in healthy children (Hmeidi, H. et al., American Thoracic Society conf. proc. 2016; p10749). Aims: To examine the relationship between SLP-derived breathing parameters and parameters measured using conventional spirometry in children with asthma. Methods: Thirty stable asthmatic children (13 female, 7-16 years), with an FEV1% of SLP and FEV1% was examined using Spearman9s Rho test. Results: A correlation of -0.49 was found betweenIE50 SLP and FEV1% (p=0.005). Conclusion: We have shown that SLP can obtain objective measures of tidal breathing in children with asthma, and that IE50 SLP correlates well with FEV1% measured using spirometry. This novel parameter could be used to quantify the degree of airway obstruction.