Validating the inspired sinewave technique to measure the volume of the 'baby lung' in a porcine lung-injury model

Douglas C Crockett; Minh C Tran; Federico Formenti; John N Cronin; Göran Hedenstierna; Anders Larsson; Phi A Phan; Andrew D Farmery

doi:10.1016/j.bja.2019.11.030

Validating the inspired sinewave technique to measure the volume of the 'baby lung' in a porcine lung-injury model

Br J Anaesth. 2020 Mar;124(3):345-353. doi: 10.1016/j.bja.2019.11.030. Epub 2020 Jan 14.

Authors

Douglas C Crockett¹, Minh C Tran², Federico Formenti³, John N Cronin⁴, Göran Hedenstierna⁵, Anders Larsson⁶, Phi A Phan⁷, Andrew D Farmery⁷

Affiliations

¹ Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK. Electronic address: douglas.crockett@ndcn.ox.ac.uk.
² Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK; Department of Engineering Science, University of Oxford, Oxford, UK.
³ Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK; Centre for Human and Applied Physiological Sciences, King's College, London, UK; Department of Biomechanics, University of Nebraska, Omaha, NE, USA.
⁴ Centre for Human and Applied Physiological Sciences, King's College, London, UK.
⁵ Hedenstierna Laboratory, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
⁶ Department of Surgical Sciences, Uppsala University, Uppsala, Sweden.
⁷ Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK.

PMID: 31952649
DOI: 10.1016/j.bja.2019.11.030

Abstract

Background: Bedside lung volume measurement could personalise ventilation and reduce driving pressure in patients with acute respiratory distress syndrome (ARDS). We investigated a modified gas-dilution method, the inspired sinewave technique (IST), to measure the effective lung volume (ELV) in pigs with uninjured lungs and in an ARDS model.

Methods: Anaesthetised mechanically ventilated pigs were studied before and after surfactant depletion by saline lavage. Changes in PEEP were used to change ELV. Paired measurements of absolute ELV were taken with IST (ELV_IST) and compared with gold-standard measures (sulphur hexafluoride wash in/washout [ELV_SF6] and computed tomography (CT) [ELV_CT]). Measured volumes were used to calculate changes in ELV (ΔELV) between PEEP levels for each method (ΔELV_IST, ΔELV_SF6, and ΔELV_CT).

Results: The coefficient of variation was <5% for repeated ELV_IST measurements (n=13 pigs). There was a strong linear relationship between ELV_IST and ELV_SF6 in uninjured lungs (r²=0.97), and with both ELV_SF6 and ELV_CT in the ARDS model (r²=0.87 and 0.92, respectively). ELV_IST had a mean bias of -12 to 13% (95% limits=±17 - 25%) compared with ELV_SF6 and ELV_CT. ΔELV_IST was concordant with ΔELV_SF6 and ΔELV_CT in 98-100% of measurements, and had a mean bias of -73 to -77 ml (95% limits=±128 - 186 ml) compared with ΔELV_SF6 and -1 ml (95% limits ±333 ml) compared with ΔELV_CT.

Conclusions: IST provides a repeatable measure of absolute ELV and shows minimal bias when tracking PEEP-induced changes in lung volume compared with CT in a saline-lavage model of ARDS.

Keywords: ARDS; computed tomography; inspired sinewave technique; lung volume measurement; method comparison.

Publication types

Research Support, Non-U.S. Gov't
Validation Study

MeSH terms

Animals
Disease Models, Animal
Lung Volume Measurements / methods
Point-of-Care Testing
Positive-Pressure Respiration / methods*
Reproducibility of Results
Respiratory Distress Syndrome / diagnostic imaging
Respiratory Distress Syndrome / etiology
Respiratory Distress Syndrome / physiopathology
Respiratory Distress Syndrome / therapy*
Saline Solution
Sus scrofa
Tomography, X-Ray Computed

Substances

Saline Solution

Abstract

Publication types

MeSH terms

Substances

Grants and funding