Lung ultrasound of the dependent lung detects real-time changes in lung volume in the preterm lamb

Abstract

BackgroundEffective lung protective ventilation requires reliable, real-time estimation of lung volume at the bedside. Neonatal clinicians lack a readily available imaging tool for this purpose.ObjectiveTo determine the ability of lung ultrasound (LUS) of the dependent region to detect real-time changes in lung volume, identify opening and closing pressures of the lung, and detect pulmonary hysteresis.MethodsLUS was performed on preterm lambs (n=20) during in vivo mapping of the pressure-volume relationship of the respiratory system using the super-syringe method. Electrical impedance tomography was used to derive regional lung volumes. Images were blindly graded using an expanded scoring system. The scores were compared with total and regional lung volumes, and differences in LUS scores between pressure increments were calculated.ResultsChanges in LUS scores correlated moderately with changes in total lung volume (r=0.56, 95% CI 0.47-0.64, p<0.0001) and fairly with right whole (r=0.41, CI 0.30-0.51, p<0.0001), ventral (r=0.39, CI 0.28-0.49, p<0.0001), central (r=0.41, CI 0.31-0.52, p<0.0001) and dorsal (r=0.38, CI 0.27-0.49, p<0.0001) regional lung volumes. The pressure-volume relationship of the lung exhibited hysteresis in all lambs. LUS was able to detect hysteresis in 17 (85%) lambs. The greatest changes in LUS scores occurred at the opening and closing pressures.ConclusionLUS was able to detect large changes in total and regional lung volume in real time and correctly identified opening and closing pressures but lacked the precision to detect small changes in lung volume. Further work is needed to improve precision prior to translation to clinical practice.

Quantitative lung ultrasound detects dynamic changes in lung recruitment in the preterm lamb

“…2). Q-LUS MGV was able to differentiate between pressures (median volume [IQR]) of 15 cm H 2 O (5 [4][5] ml/kg) and 30 cm H 2 O (18 [15][16][17][18][19][20][21][22] ml/kg) during the inflation series (p = 0.01), and 20 cm H 2 O (19 [15][16][17][18][19][20][21][22][23] ml//kg) and 10 cm H 2 O (12 [10][11][12][13][14][15][16] ml/kg) during the deflation series (p = 0.04) (Supplementary Table E1). Q-LUS MGV demonstrated distinct inflation and deflation limbs, and pulmonary hysteresis in all lambs (Individual pressure/Q-LUS MGV relationships, Supplementary Fig.…”

“…3 Ultrasound interaction with the pleura produces consistent artefact patterns that correspond with lung aeration, 4 forming the foundations of visual scoring systems for LUS. 5,6 Despite traditional LUS scoring systems reliably diagnosing some neonatal respiratory conditions, 5,[7][8][9] and detecting large lung volume changes in adults 10 and in animal models of the preterm lung, 11 they cannot measure small changes in lung volume. 12 There are few reports of the accuracy of LUS against gold-standards measurements of lung volume such as gas washout, computed tomography (CT) or the super-syringe technique, 13 and only one has specifically studied the preterm lung.…”

“…12 There are few reports of the accuracy of LUS against gold-standards measurements of lung volume such as gas washout, computed tomography (CT) or the super-syringe technique, 13 and only one has specifically studied the preterm lung. 11 Thus, whilst a role for LUS is established, some aspects such as the assessment of preterm lung recruitment need further evaluation. [14][15][16] The shortcomings of traditional LUS may be overcome by supplementing interpretation with computer-assisted image analysis.…”

ERS International Congress 2022: highlights from the Paediatrics Assembly

“…Novel techniques such as automated oxygen control systems were reported to improve time spent within target oxygen saturations in the intensive care settings, with large trials reporting on the long-term outcomes being recommended [ 51 ]. Lung ultrasound is becoming much more widely available and accessible, and can be used as a diagnostic tool, to guide respiratory support, and predict outcomes [ 52 , 53 ]. Electrical impedance tomography is an up-and-coming non-invasive method used to define pulmonary physiology and describe regional lung aeration and mechanics, and to guide the titration of positive end-expiratory pressure [ 54 , 55 ].…”