The precision and accuracy of Nellcor and Masimo oximeters at low oxygen saturations (70%) in newborn lambs

Intermittent Hypoxemia and Bronchopulmonary Dysplasia with Pulmonary Hypertension in Preterm Infants

Rationale: Bedside biomarkers that allow early identification of infants with bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH) are critically important, given the higher risk of death in these infants. Objectives: We hypothesized that infants with BPD-PH have patterns of intermittent hypoxemia (IH) that differ from infants with BPD without PH. Methods: We conducted a matched case-control study of extremely preterm infants from 22 weeks 0 days to 28 weeks 6 days born between 2018 and 2020 at the University of Alabama at Birmingham. BPD-PH status was determined using echocardiographic data performed after postnatal Day 28. Physiologic data were compared between infants with BPD-PH (cases) and BPD alone (control subjects). Receiver operating characteristic (ROC) analysis estimated the predictive ability of cumulative hypoxemia, desaturation frequency, and duration of intermittent hypoxemic events in the week preceding echocardiography to discriminate between cases and control subjects. Measurements and Main Results: Forty infants with BPD-PH were compared with 40 infants with BPD alone. Infants with and without PH had a similar frequency of IH events, but infants with PH had more prolonged hypoxemic events for desaturations below 80% (7 s vs. 6 s; P = 0.03) and 70% (105 s vs. 58 s; P = 0.008). Among infants with BPD-PH, infants who died had longer hypoxemic events below 70% (145 s vs. 72 s; P = 0.01). Using the duration of hypoxemic events below 70%, the areas under the ROC curves for diagnosis of BPD-PH and death in BPD-PH infants were 0.71 and 0.77, respectively. Conclusions: Longer duration of intermittent hypoxemic events was associated both with a diagnosis of BPD-PH and with death among infants with BPD-PH.

Standards for preclinical research and publications in developmental anaesthetic neurotoxicity: expert opinion statement from the SmartTots preclinical working group

In March 2019, SmartTots, a public-private partnership between the US Food and Drug Administration and the International Anesthesia Research Society, hosted a meeting attended by research experts, anaesthesia journal editors, and government agency representatives to discuss the continued need for rigorous preclinical research and the importance of establishing reporting standards for the field of anaesthetic perinatal neurotoxicity. This group affirmed the importance of preclinical research in the field, and welcomed novel and mechanistic approaches to answer some of the field's largest questions. The attendees concluded that summarising the benefits and disadvantages of specific model systems, and providing guidance for reporting results, would be helpful for designing new experiments and interpreting results across laboratories. This expert opinion report is a summary of these discussions, and includes a focused review of current animal models and reporting standards for the field of perinatal anaesthetic neurotoxicity. This will serve as a practical guide and road map for novel and rigorous experimental work.

Evaluation of the reliability of pulse oximetry, at different attachment sites, to detect hypoxaemia in immobilized impala (Aepyceros melampus)

OBJECTIVE

Evaluation of the reliability of pulse oximetry at four different attachment sites compared to haemoglobin oxygen saturation measured by a co-oximeter and calculated by a blood gas analyser in immobilized impala.

STUDY DESIGN

Randomized crossover study.

ANIMALS

A total of 16 female impala.

METHODS

Impala were immobilized with etorphine or thiafentanil alone, or etorphine in combination with a novel drug. Once immobilized, arterial blood samples were collected at 5 minute intervals for 30 minutes. Then oxygen was insufflated (5 L minute^-1) intranasally at 40 minutes and additional samples were collected. A blood gas analyser was used to measure the arterial partial pressure of oxygen and calculate the oxygen haemoglobin saturation (cSaO₂); a co-oximeter was used to measure the oxygen haemoglobin saturation (SaO₂) in arterial blood. Pulse oximeter probes were attached: under the tail, to the pinna (ear) and buccal mucosa (cheek) and inside the rectum. Pulse oximeter readings [peripheral oxygen haemoglobin saturation (SpO₂) and pulse quality] were recorded at each site and compared with SaO₂ and cSaO₂ using Bland-Altman and accuracy of the area root mean squares (A_rms) methods to determine the efficacy. P value < 0.05 was considered significant.

RESULTS

Pulse quality was 'good' at each attachment site. SpO₂ measured under the tail was accurate and precise but only when SaO₂ values were above 90% (bias = 3, precision = 3, A_rms = 4). The ear, cheek and rectal probes failed to give accurate or precise readings (ear: bias = -4, precision = 14, A_rms = 15; cheek: bias = 12, precision = 11, A_rms = 16; and rectum: bias = 5, precision = 12, A_rms = 13).

CONCLUSIONS AND CLINICAL RELEVANCE

In order to obtain accurate and precise pulse oximetry readings in immobilized impala, probes must be placed under the tail and SaO₂ must be above 90%. Since SaO₂ values are usually low in immobilized impala, pulse oximeter readings should be interpreted with caution.

Neonatal monitoring during delivery room emergencies

Fetal to neonatal transition after birth is a complex, well-coordinated process involving multiple organ systems. Any significant derangement in this process increases the risk of death and other adverse outcomes, underlying the importance of continuous monitoring to promptly detect and correct these derangements by effective resuscitative support. In recent years, there has been increasing efforts to move from subjective and discontinuous monitoring to more objective and continuous monitoring of different physiological parameters. Some of them like pulse oximetry for arterial oxygen saturation and electrocardiography for heart rate monitoring are now part of resuscitation guidelines whereas others like respiratory function monitoring, near infrared spectroscopy, or amplitude integrated electroencephalography are being evaluated. In this review, we describe some of the physiological parameters that can be monitored during delivery room emergencies and review the evidence for some of the monitoring technologies currently being evaluated.

Intermittent Hypoxemia in Preterm Infants

Intermittent hypoxemia (IH) events are common during early postnatal life, particularly in preterm infants. These events have been associated with multiple morbidities, including retinopathy of prematurity, sleep disordered breathing, neurodevelopmental impairment, and mortality. The relationship between IH and poor outcomes may depend on the patterns (frequency, duration, and timing) of the IH events. Current treatment modalities used in the clinical setting have been only partially successful in reducing the incidence of apnea and accompanying IH, but the risks and benefits of more aggressive interventions should include knowledge of the relationship between IH and morbidity.

Case Report of Anemia Following Fetal-Maternal Hemorrhage

BACKGROUND

Any maternal history of blood loss, ABO or Rh incompatibility, and hydrops fetalis often leads to suspicion of neonatal anemia postnatally. When maternal history consists only of decreased fetal movement, recognition of neonatal anemia can be problematic.

CLINICAL FINDINGS

This case was a transported late preterm neonate who presented initially with persistent hypoxia unresponsive to usual respiratory support. On examination, mild paleness was noted.

PRIMARY DIAGNOSIS

Anemia caused by fetal-maternal hemorrhage was the ultimate diagnosis confirmed by a Kleihauer-Betke test on maternal serum examining fetal cells.

INTERVENTIONS

Neonatal resuscitation included positive pressure ventilation, oxygen, and intubation. However, oxygenation did not improve prompting consultation with the neonatologist. Sedation and a paralytic were given. A chest radiograph ruled out pneumothoraces and pleural effusions as causative. Initiation of inhaled nitric oxide produced a mild response. Eventually, the transport nurse obtained a complete blood count indicating severe anemia, which prompted an emergent blood transfusion. The accepting neonatology team consulted with the obstetrician and a Kleihauer-Betke test was performed on mother's blood confirming a large fetal-maternal hemorrhage.

OUTCOMES

This neonate responded well to blood transfusions, a pressor, and respiratory support and was discharged home at 7 days of life.

PRACTICE RECOMMENDATIONS

Recognition of postnatal anemia is vital to sustaining life and this can occur in the transport environment. When maternal history is nonspecific and a neonate is hypoxic, uncommon causes of hypoxia can be identified with consultation and a complete blood count.

Intermittent hypoxemia and oxidative stress in preterm infants

Intermittent hypoxemia events (IH) are common in extremely preterm infants and are associated with many poor outcomes including retinopathy or prematurity, wheezing, bronchopulmonary dysplasia, cognitive or language delays and motor impairment. More recent data in animal and rodent models have suggested that specific patterns of IH may increase the risk for morbidity. The pathway by which these high risk patterns of IH initiate a pathological cascade is unknown but animal models suggest that oxidative stress may play a role. This review describes early postnatal patterns of IH in preterm infants, their relationship with morbidity, oxidative stress biomarkers relevant to the newborn infant and the relationship between IH and reactive oxygen species.

Evaluation of pulse co-oximetry to determine haemoglobin saturation with oxygen and haemoglobin concentration in anaesthetized horses: a retrospective study

OBJECTIVE

This study compared the values of variables measured by pulse co-oximetry (Masimo Radical 7; Masimo Europe Limited, UK) with those measured by a co-oximeter-enabled blood gas analyser (Siemens Rapid-point 500; Siemens Healthcare Limited, UK) in anaesthetized horses.

STUDY DESIGN

Retrospective study.

ANIMALS

A total of 30 anaesthetized horses.

METHODS

In total, 47 heparinized arterial blood samples were collected for blood gas analysis to determine haemoglobin concentration (tHb, g L^-1) and percentage of haemoglobin saturation with oxygen (SaO₂). Arterial haemoglobin saturation with oxygen was determined noninvasively by pulse co-oximetry (Masimo SpO₂). Pulse co-oximetry also provided arterial haemoglobin concentration (SpHb) and arterial oxygen content (SpCaO₂). Arterial oxygen content was calculated (CaO₂) in 39 samples using SaO₂ and the value of Hüfner's constant used by Masimo Radical 7 (1.3 mL g^-1). Data were compared using Bland-Altman analysis, correlation tests, accuracy root mean square (ARMS) statistics and total allowable error, where available.

RESULTS

Low bias but wide limits of agreement (LoA) were found between Masimo SpO₂ and SaO₂ (bias = -1.4%, LoA = -4.0 to 1.3%), with an ARMS of 3%. Compared with tHb, SpHb showed low bias (6.2 g L^-1) but wide LoA (-39.6 to 52.6 g L^-1); its % bias (5.2%) was still within the 7% limits recommended by the Clinical Laboratory Improvement Amendments (CLIA) for humans. When comparing SpCaO₂ and CaO₂, the bias and LoA were -0.2 mL dL^-1 and -6.7 to 6.2 mL dL^-1, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Masimo SpO₂ was acceptable for current ARMS standards, and SpHb measurements also met CLIA limits. The wide LoA in this study, however, suggest that the Masimo Radical 7 cannot be recommended as a substitute for direct measurements. As blood gas machines, pulse oximeters and co-oximeters use algorithms based on human haemoglobin, no true gold standard exists for horses.

Devices used for stabilisation of newborn infants at birth

This review examines devices used during newborn stabilisation. Evidence for their use to optimise the thermal, respiratory and cardiovascular management in the delivery room is presented. Mechanisms of action and rationale of use are described, current developments are presented and areas of future research are highlighted.

The Accuracy of Noninvasive Peripheral Pulse Oximetry After Palliative Cardiac Surgery in Patients With Cyanotic Congenital Heart Disease

BACKGROUND

Children with cyanotic congenital heart disease (CCHD) live with oxyhemoglobin saturations that are typically expressed as percentages in the range of 70s and 80s. Peripheral pulse oximetry (measurement of SpO₂) performs poorly in this range and yet is widely used to inform clinical decisions in these patients. The reference standard is co-oximetry of arterial samples (SaO₂).

METHODS

In this study, 515 paired measurements of SpO₂ and SaO₂ were taken from 19 children who had undergone palliative cardiac surgery.

RESULTS

SpO₂ (Masimo SET LNCS Neo pulse oximeter) overestimated oxyhemoglobin saturation in 82% of measurements (mean 4.6% ± 6.6%). There was a strong negative correlation between mean bias and SaO₂ ( r = -.96, P = .002, 95% confidence interval: -0.99 to -0.68).

CONCLUSION

The results raise a concern that critical hypoxemia may go undetected and untreated if pulse oximetry is relied upon as the primary means of assessing oxyhemoglobin saturation in children with CCHD. Strong preference must be given to co-oximetry of arterial samples.

Reliability of Pulse Oximetry during Progressive Hypoxia, Cardiopulmonary Resuscitation, and Recovery in a Piglet Model of Neonatal Hypoxic Cardiac Arrest

BACKGROUND

Pulse oximetry is widely used in intensive care and emergency conditions to monitor arterial oxygenation and to guide oxygen therapy.

OBJECTIVE

To study the reliability of pulse oximetry in comparison with CO-oximetry in newborn piglets during progressive hypoxia, cardiac arrest, cardiopulmonary resuscitation (CPR), and after return of spontaneous circulation (ROSC).

METHODS

Thirty-three newborn piglets were exposed to hypoxia until asystole occurred and then resuscitated until ROSC. Arterial oxygen saturation was monitored continuously by pulse oximetry (SpO2) with one sensor applied to the wrist of the right forelimb (FL) and another to the thigh of the left hind limb (HL). Arterial functional oxygen saturation (SaO2) was measured at baseline and at predefined intervals during each phase of the experiment. SpO2 was compared with coinciding SaO2 values and bias considered whenever the difference (SpO2 - SaO2) was beyond ±5%.

RESULTS

Bias values were lower at the baseline measurements (-3.7 ± 2.3% in FL and -4.1 ± 3.4% in HL) as well as after ROSC (1.5 ± 4.2% in FL and 0.2 ± 4.6% in HL) with higher precision and accuracy than during other experiment phases. During hypoxia induction, cardiac arrest, and CPR, there was a marked decrease in precision and accuracy as well as an increase in bias up to 43 ± 26 and 56 ± 27% in FL and HL, respectively, over a range of SaO2 from 13 to 51%.

CONCLUSION

Pulse oximetry showed increased bias and decreased accuracy and precision during marked hypoxemia in a model of neonatal hypoxic cardiac arrest.

Accuracy of the Masimo SET® LNCS neo peripheral pulse oximeter in cyanotic congenital heart disease

Introduction Non-invasive peripheral pulse oximeters are routinely used to measure oxyhaemoglobin saturation (SpO2) in cyanotic congenital heart disease. These probes are calibrated in healthy adult volunteers between arterial saturations of ~75 and 100%, using the gold standard of co-oximetry on arterial blood samples. There are little data to attest their accuracy in cyanotic congenital heart disease. Aims We aimed to assess the accuracy of a commonly used probe in children with cyanotic congenital heart disease.

METHODS

Children with cyanotic congenital heart disease admitted to the Paediatric Intensive Care Unit with an arterial line in situ were included to our study. Prospective simultaneous recordings of SpO2, measured by the Masimo SET® LNCS Neo peripheral probe, and co-oximeter saturations (SaO2) measured by arterial blood gas analysis were recorded.

RESULTS

A total of 527 paired measurements of SpO2 and SaO2 (using an ABL800 FLEX analyser) in 25 children were obtained. The mean bias of the pulse oximeter for all SaO2 readings was +4.7±13.8%. The wide standard deviation indicates poor precision. This mean bias increased to +7.0±13.7% at SaO2 recordings <75%. The accuracy root mean square of the recordings was 3.30% across all saturation levels, and this increased to 4.98% at SaO2 <75%.

CONCLUSIONS

The performance of the Masimo SET® LNCS Neo pulse oximeter is poor when arterial oxyhaemoglobin saturations are below 75%. It tends to overestimate saturations in children with cyanotic congenital heart disease. This may have serious implications for clinical decisions.

Pulse oximetry performance in mechanically ventilated newborn infants

Pulse oximetry is widely used to target oxygenation in newborn infants. In a retrospective chart review of 138 mechanically ventilated infants, pulse oximetry overestimated blood oxygen saturation compared to arterial blood gas analyses. Despite improvements in pulse oximeter technology, pulse oximetry performance in sick newborns should still be under scrutiny.

Assessing the tongue colour of newly born infants may help to predict the need for supplemental oxygen in the delivery room

AIM

It takes several minutes for infants to become pink after birth. Preductal oxygen saturation (SpO2) measurements are used to guide the delivery of supplemental oxygen to newly born infants, but pulse oximetry is not available in many parts of the world. We explored whether the pinkness of an infant's tongue provided a useful indication that supplemental oxygen was required.

METHODS

This was a prospective observational study of infants delivered by Caesarean section. Simultaneous recording of SpO2 and visual assessment of whether the tongue was pink or not was made at 1-7 and 10 min after birth.

RESULTS

The 38 midwives and seven paediatric trainees carried out 271 paired assessments on 68 infants with a mean (SD) birthweight of 3214 (545) grams and gestational age of 38 (2) weeks. When the infant did not have a pink tongue, this predicted SpO2 of <70% with a sensitivity of 26% and a specificity of 96%.

CONCLUSION

Tongue colour was a specific but insensitive sign that indicated when SpO2 was <70%. When the tongue is pink, it is likely that an infant has an SpO2 of more than 70% and does not require supplemental oxygen.

Monitoring Oxygenation and Gas Exchange in Neonatal Intensive Care Units: Current Practice in the Netherlands

BACKGROUND

Although recommendations in oxygenation and gas exchange monitoring in the neonatal intensive care unit (NICU) are available, little is known of the current practice.

AIM

To evaluate the current practice in oxygenation and gas exchange monitoring of the NICUs in the Netherlands.

METHODS

An online survey-based questionnaire concerning preferences and current practice of monitoring oxygenation and gas exchange was sent out to all 107 neonatal staff members (neonatologists, neonatal fellows, and physician assistants) of the 10 NICUs in the Netherlands.

RESULTS

The response rate was 42%. Pulse oximetry (PO), partial pressure of oxygen in arterial blood gas (paO2), and oxygen saturation in arterial blood gas (saO2) was used by, respectively, 100, 80, and 27% of the staff members for monitoring oxygenation. Of all staff members, 76% considered PO as the best parameter for monitoring oxygenation, 22% paO2, and 2% saO2. Blood gas, transcutaneous gas monitoring, endotracheal gas monitoring, and near-infrared spectroscopy was used by, respectively, 100, 82, 40, and 18% of the staff members for monitoring gas exchange. During endotracheal ventilation, 67% of the caregivers would exclusively accept arterial blood gas for gas exchange monitoring. In contrast, during non-invasive ventilation, 68% of the caregivers did not prefer arterial or capillary blood gas (CBG). CBG is found reliable in infants with warm extremities by 76% of the caregivers. Venous blood gas would be accepted by 60% of the caregivers, independent of the mode of respiratory support, and only when venous blood sample was needed for other reasons.

CONCLUSION

This survey identified a wide variation in preference in monitoring oxygenation and gas exchange monitoring among Dutch neonatal staff members.