Background: A 4-year-old boy and his father exhibited low oxygen saturation measured transcutaneously by pulse oximetry, a finding that could not be confirmed by arterial blood gas analysis. Both patients exhibited slight hemolysis in their blood, and the boy had a microcytic anemia. There was no evidence of hypoxemia or methemoglobinemia. Despite the normal results from the arterial blood gas analysis, a right-to-left-shunt was assumed in the boy until a cardiology examination excluded this diagnosis. Sleep apnea syndrome was suspected in the father and treated with nocturnal positive pressure respiration based on the low oxygen saturation values obtained with pulse oximetry. Only after consultation with our laboratory was a hemoglobin variant suspected and investigated. Methods: We performed hemoglobin protein analysis by HPLC, electrophoretic separation, and spectrophotometry and DNA sequence analysis of the α-globin gene. Results: Both HPLC chromatographic separation and alkaline electrophoresis revealed a unique hemoglobin peak. In both patients, α-globin gene sequencing revealed a mutation resulting in a histidine-to–aspartatic acid substitution at position α87. The low oxygen saturation measurement by pulse oximetry was due to hemoglobin Bonn oxyhemoglobin having an absorption peak at 668 nm, near the 660 nm measured by pulse oximeters. Conclusion: Hemoglobin Bonn is a novel hemoglobin variant of the proximal α-globin that results in falsely low oxygen saturation measurements with pulse oximetry.

Objectives The aim of this study was to assess the validity, accuracy, and reproducibility of real‐time 3‐dimensional (3D) echocardiography for small distances, areas, and volumes. Methods Real‐time 3D echocardiography using matrix technology was performed in small calibrated tissue‐mimicking phantoms and compared with 2‐dimensional (2D) echocardiography. In a systematic variation of variables on data acquisition and analysis including different 3D workstations (manual disk summation versus semiautomatic border detection), the relative contributions of sources of errors were determined. The clinical relevance of the in vitro findings was assessed in 5 neonates and infants. Results Distance calculation was valid (mean relative error ± SD, −0.15% ± 1.2%). Underestimation of areas and volumes was significant for both 2D and 3D echocardiography (area: 2D, −7.0% ± 2.9%; 3D, −6.0% ± 2.8%; volume: 2D, −13.1% ± 4.5%; 3D, −6.7% ± 2.5%; P < .05). Adjustment of compression and gain on data acquisition (difference of the means: 2D, 11.6%; 3D, 17.9%), gain on postprocessing (3D, 3.4%), and the border detection algorithm on analysis (2D, 4.8%; 3D, 16.6%) had a highly significant effect on volume and area calculations (P < .001). In vivo, compression and gain on acquisition (3D, 19.1%) and the 3D workstation on analysis (3D, 22.2%) had a highly significant impact on left ventricular volumetry (P < .001). Conclusions Real‐time 3D echocardiography is a reliable method for calculation of small distances, areas, and volumes comparable with the size of the neonatal and infant heart. Variables influencing boundary identification during image acquisition and analysis have a significant impact on 2D and 3D area and volume calculations. Standardized protocols are mandatory to avoid these sources of error in both clinical practice and research.

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