Abstract
BackgroundBedside measurement of lung volume may provide guidance in the personalised setting of respiratory support, especially in patients with the acute respiratory distress syndrome at risk of ventilator-induced lung injury. We propose here a novel operator-independent technique, enabled by a fibre optic oxygen sensor, to quantify the lung volume available for gas exchange. We hypothesised that the continuous measurement of arterial partial pressure of oxygen (PaO2) decline during a breath-holding manoeuvre could be used to estimate lung volume in a single-compartment physiological model of the respiratory system.MethodsThirteen pigs with a saline lavage lung injury model and six control pigs were studied under general anaesthesia during mechanical ventilation. Lung volumes were measured by simultaneous PaO2 rate of decline (VPaO2) and whole-lung computed tomography scan (VCT) during apnoea at different positive end-expiratory and end-inspiratory pressures.ResultsA total of 146 volume measurements was completed (range 134 to 1869 mL). A linear correlation between VCT and VPaO2 was found both in control (slope = 0.9, R2 = 0.88) and in saline-lavaged pigs (slope = 0.64, R2 = 0.70). The bias from Bland–Altman analysis for the agreement between the VCT and VPaO2 was − 84 mL (limits of agreement ± 301 mL) in control and + 2 mL (LoA ± 406 mL) in saline-lavaged pigs. The concordance for changes in lung volume, quantified with polar plot analysis, was − 4º (LoA ± 19°) in control and − 9° (LoA ± 33°) in saline-lavaged pigs.ConclusionBedside measurement of PaO2 rate of decline during apnoea is a potential approach for estimation of lung volume changes associated with different levels of airway pressure.
Highlights
Bedside measurement of lung volume may provide guidance in the personalised setting of respiratory support, especially in patients with the acute respiratory distress syndrome at risk of ventilator-induced lung injury
Clinical trials aimed at reducing lung injury via the application of high positive end-expiratory pressure (PEEP) levels have demonstrated conflicting results [3], suggesting that similar ventilator settings do not produce the same response at the alveolar level between different patients, especially in the presence of the “baby lung”, a smaller lung volume available for ventilation [4]
A total number of 146 paired lung volume measurements were analysed in 6 control pigs and 13 saline lavage lung injury pig models at five different PEEP levels
Summary
Bedside measurement of lung volume may provide guidance in the personalised setting of respiratory support, especially in patients with the acute respiratory distress syndrome at risk of ventilator-induced lung injury. Clinical trials aimed at reducing lung injury via the application of high positive end-expiratory pressure (PEEP) levels have demonstrated conflicting results [3], suggesting that similar ventilator settings do not produce the same response at the alveolar level between different patients, especially in the presence of the “baby lung”, a smaller lung volume available for ventilation [4] This could be the case in the presence of lung heterogeneity like in COVID-19, where very similar arterial partial pressure of oxygen (PaO2) can be observed for very different computed tomography (CT) values [5,6,7]. There is a clear need for developments to enable individual titration of mechanical ventilation strategy, for example bedside real-time measurement of lung volume available for gas exchange, especially following changes between PEEP levels [8], which may contribute to the identification of patients with recruitable lungs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
