A modification of the Bohr method to determine airways deadspace for non-uniform inspired gas tensions

Experimental Physiology

Pacpaco

et al. 2018

Self Cite

The inspired sine-wave technique (IST) is a new method that can provide simple, non-invasive cardiopulmonary measurements. Over successive tidal breaths, the concentration of a tracer gas (i.e. nitrous oxide, N O) is sinusoidally modulated in inspired air. Using a single-compartment tidal-ventilation lung model, the resulting amplitude/phase of the expired sine wave allows estimation of end-expired lung volume (ELV), pulmonary blood flow and three indices for ventilatory heterogeneity (VH; ELV /FRC , ELV /FRC and ELV /ELV ). This investigation aimed to determine the repeatability and agreement of ELV with FRC and, as normal ageing results in well-established changes in pulmonary structure and function, whether the IST estimates of ELV and VH are age dependent. Forty-eight healthy never-smoker participants (20-86 years) underwent traditional pulmonary function testing (e.g. spirometry, body plethysmography) and the IST test, which consisted of 4 min of quiet breathing through a face mask while inspired N O concentrations were oscillated in a sine-wave pattern with a fixed mean (4%) and amplitude (3%) and a period of either 180 or 60 s. The ELV /FRC and ELV /FRC were age dependent (average decreases of 0.58 and 0.48% year ), suggesting an increase in VH with advancing age. The ELV showed a mean bias of -1.09 litres versus FRC , but when normalized for the effects of age this bias reduced to -0.35 litres. The IST test has potential to provide clinically useful information necessitating further study (e.g. for mechanically ventilated or obstructive lung disease patients), but these findings suggest that the increases in VH with healthy ageing must be taken into account in clinical investigations.

Section: Discussionmentioning

confidence: 99%

“…Using a single‐compartment tidal ventilation model of the lung, the resulting amplitude and phase of the expired sine wave allow the estimation of

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Section: Methodsmentioning

confidence: 99%

The inspired sine‐wave technique: A novel method to measure lung volume and ventilatory heterogeneity

Bruce

Experimental Physiology

Pacpaco

et al. 2018

Self Cite

“…To compensate for the error associated with the non-uniform inspired concentration, a modified Bohr method has been proposed. The modified method improves the accuracy and repeatability of the airway deadspace estimation [21] . This improvement, in turn, leads to increased accuracy and repeatability in the estimation of the lung volume \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$V_{A} $ \end{document} and the pulmonary blood flow \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$Q_{P} $ \end{document} subsequently.…”

Section: Methodsmentioning

confidence: 99%

The Inspired Sinewave Technique: A Comparison Study With Body Plethysmography in Healthy Volunteers

IEEE J. Transl. Eng. Health Med.

Zhang

Geer

et al. 2017

Self Cite

The inspired sinewave technique is a noninvasive method to measure airway dead space, functional residual capacity, pulmonary blood flow, and lung inhomogeneity simultaneously. The purpose of this paper was to assess the repeatability and accuracy of the current device prototype in measuring functional residual capacity, and also participant comfort when using such a device. To assess within-session repeatability, six sinewave measurements were taken over two-hour period in 17 healthy volunteers. To assess day-to-day repeatability, measurements were taken over 16 days in 3 volunteers. To assess accuracy, sinewave measurements were compared to body plethysmography in 44 healthy volunteers. Finally, 18 volunteers who experienced the inspired sinewave device, body plethysmography and spirometry were asked to rate the comfort of each technique on a scale of 1–10. The repeatability coefficients for dead space, functional residual capacity, and blood flow were 48.7 ml, 0.48L, and 2.4L/min respectively. Bland-Altman analyses showed a mean BIAS(SD) of −0.68(0.42)L for functional residual capacity when compared with body plethysmography. 14 out of 18 volunteers rated the inspired sinewave device as their preferred technique. The repeatability and accuracy of functional residual capacity measurements were found to be as good as other techniques in the literature. The high level of comfort and the non-requirement of patient effort meant that, if further refined, the inspired sinewave technique could be an attractive solution for difficult patient groups such as very young children, elderly, and ventilated patients.

“…2. The IST quantifies the deadspace volume by using modified Bohr method [11] and subsequently the ELV and Qp are calculated according to this one well-mixed lung compartment (Fig. 1a).…”

Section: Device and Analysismentioning

confidence: 99%

Validating the Inspired Sinewave Technique to Measure Lung Heterogeneity Compared to Atelectasis & Over-Distended Volume in Computed Tomography Images

Trân

ICASSP 2021 - 2021 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Crockett

et al. 2021

The inspired sinewave technique (IST) is a non-invasive nonionising method which can measure accurately lung parameters. Six anaesthetised pigs were studied after surfactant depletion by saline-lavage. Paired measurements of lung heterogeneity were taken with the IST and computed tomography (CT). Lung heterogeneity measured by the IST was calculated by the ratio of tracer gas outputs measured at 180s and 60s. In CT images, lungs were manually segmented and divided into different regions according to voxel density. The IST and CT show strong agreement on lung heterogeneity measurements. In the IST ventilation heterogeneity value, the linear correlation in total of six pigs are weaker than individual animal (R 2 =0.33 vs R 2 =0.67 on average). The IST perfusion heterogeneity agreements are lower than IST ventilation values due to the IST technical setup. IST has the potential to measure the lung heterogeneity in ARDS animals.