Overestimation of Oxygen Saturation Measured by Pulse Oximetry in Hypoxemia. Part 1: Effect of Optical Pathlengths-Ratio Increase.

On average, arterial oxygen saturation measured by pulse oximetry (SpO2) is higher in hypoxemia than the true oxygen saturation measured invasively (SaO2), thereby increasing the risk of occult hypoxemia. In the current article, measurements of SpO2 on 17 cyanotic newborns were performed by means of a Nellcor pulse oximeter (POx), based on light with two wavelengths in the red and infrared regions (660 and 900 nm), and by means of a novel POx, based on two wavelengths in the infrared region (761 and 820 nm). The SpO2 readings from the two POxs showed higher values than the invasive SaO2 readings, and the disparity increased with decreasing SaO2. SpO2 measured using the two infrared wavelengths showed better correlation with SaO2 than SpO2 measured using the red and infrared wavelengths. After appropriate calibration, the standard deviation of the individual SpO2-SaO2 differences for the two-infrared POx was smaller (3.6%) than that for the red and infrared POx (6.5%, p < 0.05). The overestimation of SpO2 readings in hypoxemia was explained by the increase in hypoxemia of the optical pathlengths-ratio between the two wavelengths. The two-infrared POx can reduce the overestimation of SpO2 measurement in hypoxemia and the consequent risk of occult hypoxemia, owing to its smaller increase in pathlengths-ratio in hypoxemia.

Capnography for catheter location confirmation in minimally invasive surfactant administration.

OBJECTIVES: Minimally Invasive Surfactant Treatment (MIST) is a common method for administering surfactant as a treatment for respiratory distress syndrome. However, tracheal catheter placement can be difficult to confirm. We assessed the presence of carbon dioxide (CO2) in tracheal and esophageal gas aspirated using CO2 detector. STUDY DESIGN: Retrospective arm: 20 infants, MIST catheter placement was assessed with a CO2 detector in two techniques and confirmed with clinical response. Prospective arm-10 infants, aimed to check for CO2 presence in aspirated esophageal gas during routine nasogastric tube insertion. RESULTS: Retrospective arm: All infants had positive capnography. One infant that had no clinical response to MIST was diagnosed with total anomalous pulmonary venous return. All 10 infants of the prospective arm had a Negative capnography (P < 0.001, Fisher's exact test). CONCLUSIONS: Readily available CO2 detectors can distinguish between tracheal and esophageal placement of MIST catheters prior to MIST.

Feasibility of Precision Medicine in Hypertension Management-Scope and Technological Aspects.

Personalized management of diseases by considering relevant patient features enables optimal treatment, instead of management according to an average patient. Precision management of hypertension is important, because both susceptibility to complications and response to treatment vary between individuals. While the use of genomic and proteomic personal features for widespread precision hypertension management is not practical, other features, such as age, ethnicity, and cardiovascular diseases, have been utilized in guidelines for hypertension management. In precision medicine, more blood-pressure-related clinical and physiological characteristics in the patient's profile can be utilized for the determination of the threshold of hypertension and optimal treatment. Several non-invasive and simple-to-use techniques for the measurement of hypertension-related physiological features are suggested for use in precision management of hypertension. In order to provide precise management of hypertension, accurate measurement of blood pressure is required, but the available non-invasive blood pressure measurement techniques, auscultatory sphygmomanometry and oscillometry, have inherent significant inaccuracy-either functional or technological-limiting the precision of personalized management of hypertension. A novel photoplethysmography-based technique for the measurement of systolic blood pressure that was recently found to be more accurate than the two available techniques can be utilized for more precise and personalized hypertension management.

Mitral valve Doppler for cardiac output assessment in preterm neonates.

INTRODUCTION: Cardiac output (CO) assessment in neonates is commonly done by echocardiography. It is unclear which is the best site to measure the left ventricular (LV) outflow tract for CO assessment (the aortic valve [AV] aortic sinus [AS] or the sinotubular junction [STJ]). In the normal heart, the blood flow entering the LV equals the blood ejected from it. Therefore, measuring the blood flow into the LV through the mitral valve (MV) is an alternative way to measure CO. METHODS: In stable preterm infants the MV CO was compared with the right ventricular (RV) CO and the three ways to measure LV CO, in 30 stable preterm neonates. Interobserver variability for MV CO was established. RESULTS: In the 30 neonates studied, MV CO was best correlated and had a minimal bias to the RV CO and LV CO measured at the STJ. Left ventricular CO measured at the AV and AS had significant bias relative to RV CO and MV CO. MV CO inter-observer variability was similar to other echocardiographic CO assessment methods. CONCLUSION: MV CO may be used as an alternative way to assess CO. The STJ may be the optimal site to measure LV outflow tract.

Dual Therapy vs. Monotherapy for the Patent Ductus Arteriosus: A Systematic Review.

To evaluate the efficacy of dual patent ductus arteriosus (PDA) pharmacotherapy compared to monotherapy we searched Medline, Embase, Cochrane Library, and references of relevant articles through October 20, 2021 for randomized clinical trials (RCTs) and cohort studies comparing dual PDA treatment vs. monotherapy. Data were analyzed using a fixed effects model. The fixed effects model assumes that all studies included in a meta-analysis are estimating a single true underlying effect, that of ductal closure. Primary outcome was ductal closure; secondary outcome was surgical ligation. Of 170 articles retrieved, three cohort studies and two RCTs were included, totaling 470 patients: 384 babies received monotherapy and 86 dual therapy. Because of the small numbers, RCTs and cohort studies were pooled for analysis. Ductus closed in 67% of those who received combination compared with 58% those with monotherapy. Overall fixed effect shows an OR of 1.97 [1.10; 3.53; p = 0.023] favoring dual therapy. Dual pharmacologic treatment appears more effective than monotherapy. Future well-powered, high-quality, prospective RCTs are needed to further investigate this potential approach.

Vitamin D and Asthma: a Systematic Review of Clinical Trials.

PURPOSE OF THE REVIEW: To perform a systematic review of prospective clinical trials to determine whether improving vitamin D status improves asthma control. RECENT FINDINGS: In cross sectional studies suboptimal viramin D status is often associated with poor asthma control. However, decreased 25-hydroxycholecalciferol (25 (OH) D) concentrations might not be causally associated with asthma control. We performed a systematic review until December 15, 2021 according to PRISMA guideline, searching MEDLINE, MEDLINE In-Process, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials. Two searches were performed, the first using "vitamin D" and the second using "Vitamin D" or "ergocalciferol" or "cholecalciferol" and "Asthma". From 419 retrieved papers, after removal of duplicate and after using exclusion criteria, 28 full-text articles were eligible, of which 6 remained for quantitative analysis and 11 (9 studies) for qualitative analysis. From both analyses, prospective studies do not support that improving the vitamin D status of asthmatic children improves asthma control.

Nucleated Red Blood Cells as Markers of Perinatal Adaptation in Preterm Neonates Receiving Minimally Invasive Surfactant Therapy.

OBJECTIVE: The study aimed to assess the association of nucleated red blood cells (NRBC), a surrogate of intrauterine hypoxia, and elevated pulmonic vascular resistance (E-PVR) and oxygen requirement after minimally invasive surfactant therapy (MIST). STUDY DESIGN: Retrospective study of a cohort of preterm neonates that received MIST in a single unit. RESULTS: NRBC were measured in 65 of 75 (87%) neonates administered MIST during the period. In total, 22 of 65 (34%) infants had pre-MIST echocardiography (ECHO).Neonates with elevated NRBC (predefined as >5 × 109/L, n = 16) required higher post-MIST fraction of inspired oxygen (FiO2) than neonates with normal NRBC (<1 × 109/L, n = 17; FiO2 = 0.31 ± 0.10 and 0.24 ± 0.04, respectively, p = 0.02).NRBC correlated positively with % of time in right to left ductal shunt (r = 0.51, p = 0.052) and inversely with right ventricular stroke volume (r = -0.55, p = 0.031) and time to peak velocity to right ventricular ejection time ratio (r = -0.62, p < 0.001). CONCLUSION: Elevated NRBC are associated with elevated FiO2 after MIST and elevated E-PVR. Intrauterine hypoxia may impact postnatal circulatory adaptations and oxygen requirement. KEY POINTS: · Post-MIST FiO2 requirements are significantly higher in infants with elevated NRBC.. · NRBC correlates positively with elevated PVR in neonates requiring.. · Intrauterine hypoxia may play a role in postnatal circulatory adaptations in neonates with RDS..

Toward rational management of patent ductus arteriosus: ductal disease staging and first line paracetamol.

AIMS: To study paracetamol (PCM) use as first line therapy for significant patent ductus arteriosus (sPDA) closure, stratified by echocardiography. METHODS: In this retrospective observational study, a prepublished score comprising PDA size and velocity, PDA:left pulmonary artery ratio, diastolic flow in main and LPA, LA:Ao ratio and left ventricular:aortic ratio were included for shunt severity. Successful closure was defined a priori as closure or ≥50% reduction in score. Comparisons were made between infants with sPDA who were treated and not treated. RESULTS: During November 2017-2018, 227 infants from 23 to 31+6 weeks' gestational age (GA) were admitted; 50 (22%) infants were diagnosed with PDA, 32 treated with PCM, overall treatment rate of 32/227 (14%). Successful therapy was noted in 23/32 (72%) and was higher when treated at ≤7 days (80 versus 68%, p = .68), in infants >26 weeks GA (62.5 versus 100%, p = .07) and BW >1000 g (65.4 versus 100%, p = .14). Univariate analysis noted statistical significance only for GA. Eighteen infants were managed conservatively. Treated infants had a lower GA and BW, higher composite ECHO score (14.4 ± 0.5 versus 19 ± 0.4, p < .001). CONCLUSIONS: Composite scoring helped reduce exposure, and focus more on infants with lower GA and BW with greater shunt severity.

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation.

Adequate oxygen delivery to a tissue depends on sufficient oxygen content in arterial blood and blood flow to the tissue. Oximetry is a technique for the assessment of blood oxygenation by measurements of light transmission through the blood, which is based on the different absorption spectra of oxygenated and deoxygenated hemoglobin. Oxygen saturation in arterial blood provides information on the adequacy of respiration and is routinely measured in clinical settings, utilizing pulse oximetry. Oxygen saturation, in venous blood (SvO2) and in the entire blood in a tissue (StO2), is related to the blood supply to the tissue, and several oximetric techniques have been developed for their assessment. SvO2 can be measured non-invasively in the fingers, making use of modified pulse oximetry, and in the retina, using the modified Beer-Lambert Law. StO2 is measured in peripheral muscle and cerebral tissue by means of various modes of near infrared spectroscopy (NIRS), utilizing the relative transparency of infrared light in muscle and cerebral tissue. The primary problem of oximetry is the discrimination between absorption by hemoglobin and scattering by tissue elements in the attenuation measurement, and the various techniques developed for isolating the absorption effect are presented in the current review, with their limitations.

Impact of Skin-to-Skin Parent-Infant Care on Preterm Circulatory Physiology.

OBJECTIVES: To ascertain the impact of skin-to-skin care between parents and infants on cardiac function and cerebral blood flow in preterm infants. STUDY DESIGN: We undertook a prospective study of 40 self-ventilating preterm infants at a quaternary center and assessed cardiac performance and cerebral blood flow. Assessments were carried out two hours before skin-to-skin care and then 60 minutes after skin-to-skin care (with the infant still on parent and turned supine). RESULTS: Infants were 30.5 ± 0.6 weeks' gestational age and 1378 ± 133 g birthweight. Axillary temperature noted a nonsignificant increase during skin-to-skin care from 36.7 ± 0.07°C to 36.9 ± 0.07°C (P = .07). Cardiac contractility (right ventricular fractional area change [26.5% ± 0.3% vs 27.8% ± 0.4; P < .001] and tricuspid annular plane systolic excursion [0.73 ± 0.03 cm vs 0.77 ± 0.03 cm; P = .02]) increased significantly, coincident with decreased measures of pulmonary vascular resistance. An increase in systemic cardiac output was associated with increased cerebral blood flow and reduced middle cerebral artery resistive index (0.81 ± 0.02 vs 0.74 ± 0.02; P = .0001). CONCLUSIONS: We documented a significant circulatory beneficial adaptation to a common neonatal practice. These findings align with previously documented physiologic benefits in cardiorespiratory stability and cardiac rhythm in preterm infants, and may be mediated through modulation of the autonomic nervous system.

Elevated Nucleated Red Blood Cells in Neonates with Down Syndrome and Pulmonary Hypertension.

We report an association between higher absolute nucleated red blood cells and mean corpuscular volume and idiopathic persistent pulmonary hypertension of the newborn in neonates with Down syndrome. Elevation of these blood indicies should prompt echocardiographic studies to monitor pulmonary arterial pressures.

Effect of rewarming in oxygenation and respiratory condition after neonatal exposure to moderate therapeutic hypothermia.

BACKGROUND: To assess changes in clinical condition and oxygenation in neonates after rewarming following moderate therapeutic hypothermia (MTH) for neonatal encephalopathy. METHODS: Retrospective study of 28 neonates receiving MTH in a tertiary neonatal intensive care unit in Israel. We compared pre-and 24 h post-rewarming arterial oxygen saturation (SaO2) as measured by the blood gases analyzer, pulse-oximetry saturation (SpO2), and cardio-respiratory condition. RESULTS: The SpO2 declined from 96.9% (±2.9) before rewarming to 95.2% (±2.6) after rewarming (p < 0.001). Twelve neonates (42.9%) had clinical respiratory impairment (needing higher respiratory support or had new onset desaturations). In 16 neonates (57.1%) with no change in respiratory support after rewarming, SpO2 decreased from 98.3 ± 1.9% to 95.6 ± 3.0% (p < 0.001) and SaO2 decreased from 97.1 ± 1.7% to 96.0 ± 2.3% (p = 0.002). The mean SpO2 decrease was greater than mean SaO2 decrease (2.63 ± 1.8 and 1.1 ± 1.3 respectively, p = 0.021). CONCLUSION: Neonates who underwent MTH showed reduction in oxygenation after rewarming either by decreasing SpO2 or increasing FiO2 requirements. The SpO2 decline was larger than the SaO2 decline. We suggest careful monitoring of neonates after rewarming.

Pulse Oximetry with Two Infrared Wavelengths without Calibration in Extracted Arterial Blood.

Oxygen saturation in arterial blood (SaO2) provides information about the performance of the respiratory system. Non-invasive measurement of SaO2 by commercial pulse oximeters (SpO2) make use of photoplethysmographic pulses in the red and infrared regions and utilizes the different spectra of light absorption by oxygenated and de-oxygenated hemoglobin. Because light scattering and optical path-lengths differ between the two wavelengths, commercial pulse oximeters require empirical calibration which is based on SaO2 measurement in extracted arterial blood. They are still prone to error, because the path-lengths difference between the two wavelengths varies among different subjects. We have developed modified pulse oximetry, which makes use of two nearby infrared wavelengths that have relatively similar scattering constants and path-lengths and does not require an invasive calibration step. In measurements performed on adults during breath holding, the two-infrared pulse oximeter and a commercial pulse oximeter showed similar changes in SpO2. The two pulse oximeters showed similar accuracy when compared to SaO2 measurement in extracted arterial blood (the gold standard) performed in intensive care units on newborns and children with an arterial line. Errors in SpO2 because of variability in path-lengths difference between the two wavelengths are expected to be smaller in the two-infrared pulse oximeter.

Ductus arteriosus outcome with focus on the initially patent but hemodynamically insignificant ductus in preterm neonates.

BACKGROUND/OBJECTIVES: The hemodynamically insignificant (hisPDA) ductus arteriosus often progresses to hemodynamic significance. In this review, we sought risk factors predictive of progression. METHODS: Early hisPDAs were subdivided into those that closed spontaneously vs. those that progressed to hsPDA. RESULTS: Sixty percent of early hisPDAs subsequently progressed to hsPDAs. In all but one, the ductus never closed, but rather became progressively more significant over time. The echocardiographic parameters best associated with subsequent progression were an increased transductal diameter (1.81 ± 0.77 vs. 1.21 ± 0.44 mm; p < 0.001) and the presence of diastolic flow reversal. ROC curve analysis showed that the best ductal diameter criterion for predicting the progression to hsPDA was >1.4 (sensitivity = 91; specificity = 81). The combined morbidity score was higher in those infants who progressed to hsPDA as compared with those who did not (p = 0.0038). CONCLUSIONS: Increased ductal diameter and diastolic flow reversal on the first echocardiogram were best correlated with progression of hisPDA to hsPDA.

The effect of patent ductus arteriosus on pre-ductal and post-ductal perfusion index in preterm neonates.

OBJECTIVE: The ductus arteriosus is a blood vessel that connects the pulmonary artery to the descending aorta during fetal life and generally undergoes spontaneous closure shortly after birth. In premature neonates it often fails to close (patent ductus arteriosus-PDA), which can result in diversion of a significant part of the left-ventricular cardiac output to the pulmonary circulation. This left-to-right shunt may result in significant increase of pulmonary blood flow and decrease of systemic perfusion (hemodynamically significant PDA-hsPDA), which may lead to severe neonatal morbidity. The study objective was to find the relationship between hsPDA and perfusion index (PI), a photoplethysmographic parameter related to systemic perfusion. APPROACH: PI measures the relative systolic increase in tissue light absorption due to the systolic increase in the tissue blood volume. PI has been found to be directly related to tissue perfusion and is therefore expected to be affected by hsPDA. MAIN RESULTS: PI was found to be higher in preterm neonates with hsPDA after first week of life, in comparison to those with closed DA, despite the lower systemic perfusion, probably due to reverse flow during diastole. SIGNIFICANCE: In our study, perfusion index increased despite the lower systemic perfusion, indicating that in neonates with hsPDA, perfusion index is not necessarily a measure of perfusion. Nevertheless, PI can be used as a screening tool for suspicious PDA, in order to select a relatively small group of neonates for a more definitive examination by echocardiography, which is not suitable for universal screening.

Packed red blood cells transfusion in neonates: effect on FiO2 and PaO2/SaO2 ratio, and implications for neonatal saturation targeting.

OBJECTIVE: To assess the effect of blood transfusions in neonates on partial pressure of oxygen in arterial blood (PaO2), arterial hemoglobin oxygen saturation (SaO2) and arterial hemoglobin oxygen saturation as measured by pulse oximetry (SpO2). STUDY DESIGN: Retrospective study of neonates that received a first blood transfusion while having an indwelling arterial line. We compared PaO2, SaO2, SpO2, SaO2/PaO2 ratio and fraction of inspired oxygen (FiO2) 12 h before and after blood transfusion. RESULTS: Post-transfusion neonates had higher PaO2 and SaO2, had lower SaO2/PaO2 ratio, and received higher FiO2 with no change in SpO2. CONCLUSIONS: Post-transfusion, neonates had lower hemoglobin oxygen affinity. They received higher FiO2 and had higher PaO2 at the same SpO2. We speculate that FiO2 was increased in order to maintain SpO2. Larger prospective trials are needed to confirm our findings.