<b><i>Introduction:</i></b> Traditional transcutaneous oxygen (tcPO₂) measurements are affected by measurement drift, limiting accuracy and usability. The new potentially drift-free oxygen fluorescence quenching technique has been combined in a single sensor with conventional transcutaneous carbon dioxide (tcPCO₂) monitoring. This study aimed to validate optical tcPO₂ and conventional tcPCO₂ against arterial blood gas samples in preterm neonates and determine measurement drift. <b><i>Methods:</i></b> In this prospective observational study, during regular care, transcutaneous measurements were paired to arterial blood gases from preterm neonates aged 24–31 weeks of gestational age (GA) with an arterial catheter. Samples were included based on stability criteria and stratified for sepsis status. Agreement was assessed using the Bland-Altman analysis. Measurement drift per hour was calculated. <b><i>Results:</i></b> Sixty-eight premature neonates were included {median (interquartile range [IQR]) GA of 26 4/7 [25 3/7–27 5/7] weeks}, resulting in 216 stable paired samples. Agreement of stable samples in neonates without sepsis (<i>n</i> = 38) and with suspected sepsis (<i>n</i> = 112) was acceptable for tcPO₂ and good for tcPCO₂. However, in stable samples of neonates with sepsis (<i>n</i> = 66), tcPO₂ agreement (bias and 95% limits of agreement) was −32.6 (−97.0 to 31.8) mm Hg and tcPCO₂ agreement was 4.2 (−10.5 to 18.9) mm Hg. The median (IQR) absolute drift values were 0.058 (0.0231–0.1013) mm Hg/h for tcPO₂ and 0.30 (0.11–0.64) mm Hg/h for tcPCO₂. <b><i>Conclusion:</i></b> The accuracy of optical tcPO₂ in premature neonates was acceptable without sepsis, while electrochemically measured tcPCO₂ remained accurate under all circumstances. Measurement drift was negligible for tcPO₂ and highly acceptable for tcPCO₂.

Background: Heart rate (HR) detection in premature infants using electrocardiography (ECG) is challenging due to a low signal amplitude and the fragility of the premature skin. Recently, the dynamic light scattering (DLS) technique has been miniaturized, allowing noninvasive HR measurements with a single sensor. Objective: The aim was to determine the accuracy of DLS for HR measurement in infants, compared to ECG-derived HR. Methods: Stable infants with a gestational age of ≥26 weeks, monitored with ECG, were eligible for inclusion. HR was measured with the DLS sensor at 5 different sites for 15 min each. We recorded every 10th second of the DLS-derived HR and the DLS signal-to-noise ratio (SNR), and the ECG-derived HR was extracted for analysis. Patients were randomly divided into 2 groups. In the first group, the optimal SNR cutoff value was determined and then applied to the second group to assess agreement. Results: HR measurements from 31 infants were analyzed. ECG-DLS paired data points were collected at the forehead, an upper extremity, the thorax, a lower extremity, and the abdomen. When applying the international accuracy standard for HR detection, DLS accuracy in the first group (n = 15) was optimal at the forehead (SNR cutoff 1.66). Application of this cutoff to the second group (n = 16) showed good agreement between DLS-derived HR and ECG-derived HR (bias-0.73 bpm; 95% limits of agreement-15.46 and 14.00 bpm) at the forehead with approximately 80% (i.e., 1,066/1,310) of all data pairs remaining. Conclusion: The investigated DLS sensor was sensitive to movement, overall providing less accurate HR measurements than ECG and pulse oximetry. In this study population, specific measurement sites provided excellent signal quality and good agreement with ECG-derived HR.

Current haemodynamic monitoring is mainly aimed at the macrocirculation. Multiple studies have demonstrated the importance of the microcirculation in relation to the patient’s condition and impact of treatment strategies. However, continuous monitoring of the microcirculation is not yet possible in the neonatal field. A novel dynamic light scattering (DLS) sensor technology for continuous monitoring of the microcirculation was investigated in the neonatal population. Thirty-one haemodynamically stable infants were included. Sequential measurements at the forehead, upper extremity, thorax, abdomen and lower extremity were conducted with the DLS sensor. For analyses stable measurements were selected. The DLS parameters, total blood flow (TBF) and relative blood velocity (RBV), were compared between measurement locations. Changes in relative haemodynamic indices (relHIs), indicating the distribution of blood flow in the microcirculatory blood vessels, were associated with heart rate decelerations. Measurements performed at the forehead had significantly lower TBF levels, compared to measurements at other locations. Early changes in relHIs around a heart rate deceleration were recorded a median (IQR) of 22.0 (13.5–27.0) s before the onset. Measurement of the currently unavailable parameters TBF, RBV and relHIs is possible with DLS technology. Validation of the DLS technology is needed for clinical implementation.

BACKGROUND:In neonates with post-asphyxial neonatal encephalopathy, further neuronal damage is prevented with therapeutic hypothermia (TH). In addition, fluctuations in carbon dioxide levels have been associated with poor neurodevelopmental outcome, demanding close monitoring. This study investigated the accuracy and clinical value of transcutaneous carbon dioxide (tcPCO 2 ) monitoring during TH. METHODS: In this retrospective cohort study in neonates, agreement between arterial carbon dioxide (PaCO 2 ) values and tcPCO 2 measurements during TH was determined. TcPCO 2 levels during the first 24 h of hypothermia were tested for an association with ischemic brain injury on magnetic resonance imaging (MRI). RESULTS: Thirty-four neonates were included. Agreement (bias (95% limits of agreement)) between tcPCO 2 and PaCO 2 levels was 3.9 (−12.4-20.2) mm Hg. No relation was found between the body temperature and tcPCO 2 levels. TcPCO 2 levels differed significantly between patients with considerable and minimal damage on MRI; after 6 h (P = 0.02) and 9 h (P = 0.04). CONCLUSIONS: Although tcPCO 2 provided a limited estimation of PaCO 2 , it can be used for trend monitoring during TH. TcPCO 2 levels after birth could provide an early indicator of ischemic brain injury. This relation should be investigated in large prospective studies, in which adjustments for confounders can be made.

<b><i>Introduction:</i></b> Transcutaneous blood gas monitoring allows for continuous non-invasive evaluation of carbon dioxide and oxygen levels. Its use is limited as its accuracy is dependent on several factors. We aimed to identify the most influential factors to increase usability and aid in the interpretation of transcutaneous blood gas monitoring. <b><i>Methods:</i></b> In this retrospective cohort study, transcutaneous blood gas measurements were paired to arterial blood gas withdrawals in neonates admitted to the neonatal intensive care unit. The effects of patient-related, microcirculatory, macrocirculatory, respiratory, and sensor-related factors on the difference between transcutaneously and arterially measured carbon dioxide and oxygen values (ΔPCO₂ and ΔPO₂) were evaluated using marginal models. <b><i>Results:</i></b> A total of 1,578 measurement pairs from 204 infants with a median [interquartile range] gestational age of 27³/₇ [26¹/₇–31³/₇] weeks were included. ΔPCO₂ was significantly associated with the postnatal age, arterial systolic blood pressure, body temperature, arterial partial pressure of oxygen (PaO₂), and sensor temperature. ΔPO₂ was, with the exception of PaO₂, additionally associated with gestational age, birth weight Z-score, heating power, arterial partial pressure of carbon dioxide, and interactions between sepsis and body temperature and sepsis and the fraction of inspired oxygen. <b><i>Conclusion:</i></b> The reliability of transcutaneous blood gas measurements is affected by several clinical factors. Caution is recommended when interpreting transcutaneous blood gas values with an increasing postnatal age due to skin maturation, lower arterial systolic blood pressures, and for transcutaneously measured oxygen values in the case of critical illness.