Nellcor N-200 Research Articles

Prevalence and predictors of hypoxaemia in hospitalised children at the emergency unit of a resource constrained cen

Background: Hypoxaemia is often poorly detected and treated in emergently-ill children in resource-poor centres because of the non-availability of pulse oximeters and similar facilities to detect it. This study sets out to determine the prevalence and simple predictors of hypoxaemia among children with or without respiratory features at the emergency unit of the Wesley Guild Hospital, Ilesa, Nigeria Methods: Children aged one month to 14 years were consecutively recruited and prospectively studied over an eight month period. All the children had their peripheral oxygen saturation (SpO 2 ) measured at presentation using a portable pulse oximeter (Nellcor (R) N-200, USA) and hypoxaemia was defined as SpO 2 < 90%. Relevant history and examination findings were compared among hypoxaemic and nonhypoxaemic children. Multivariate analysis was used to predict the presence of hypoxaemia. Results: Four hundred and two children were recruited with male to female ratio of 1.3:1 and105 (26.1) presented with respiratory features. Eighty three (20.6%) were hypoxaemic including 40 (38.1%) of those with respiratory features at admission. Infancy, chest in-drawing, cyanosis and grunting were associated with hypoxaemia (p < 0.05) among those with respiratory features, while infancy, pallor and tachycardia were significant among those with no respiratory features. Grunting (OR = 7.875; 95% CI=1.029- 15.797; p = 0.045) and Cyanosis (OR =13.579; 95% CI = 1.360- 14.379; p = 0.009) independently predict hypoxaemia among the children with respiratory features. Conclusion: Hypoxaemia occurred in approximately one out of five ill children admitted to the emergency unit of the WGH, Ilesa and was significantly associated with mortality. Emergently ill children with cyanosis and grunting especially infants should preferentially be placed on oxygen therapy even when hypoxaemia cannot be confirmed. Keywords: Emergently ill children, hypoxaemia, predictors, resource- poor

PO-0725e Cerebral Tissue Oxygenation At Birth In Term Infants: Comparison Between Early And Late Cord Clamping

Background and aims The aim of our study is to compare the postnatal cerebral tissue oxygenation values in babies with early versus late cord clamping born after elective C/S. Methods In this prospective, observational study, we included term newborns delivered by elective C/S. Babies were segregated into two groups as early (within 15 seconds) and late cord clamping (at 60th seconds). Peripheral arterial oxygen saturation (SpO 2 ) and heart rate were measured using pulse oximetry (Nellcor N200) and regional oxygen saturation of the brain (rSO 2 brain) were measured (Invos 5100) between the 3rd and15th minutes and recorded every minute. Fractional tissue oxygen extraction (FTOE) was calculated for each minute (FTOE=pulse oximetry value-rSO 2 /pulse oximetry value). The measurements were compared for both groups. Results The demographical characteristics, SpO 2 levels, heart rates and umbilical cord blood gas values were not significantly different between the groups (p > 0.05). Cerebral oxygenation measurements and FTOE values were significantly higher for each minute in the late cord clamping group (p 2 was faster and the rSO 2 plateau was reached earlier in the late cord clamping group (Figure). Conclusions In our study we found that rSO 2 brain measurements and FTOE values were higher in the late cord clamping group without the need for any therapy as a result of high bilirubin and hematocrit levels.

Avoiding hyperoxemia during neonatal resuscitation: time to response of different SpO2 monitors

AimTo assess the time to obtain reliable oxygen saturation readings by different pulse oximeters during neonatal resuscitation in the delivery room or NICU.MethodsProspective study comparing three different pulse oximeters: Masimo Radical-7 compared simultaneously with Ohmeda Biox 3700 or with Nellcor N395, in newborn infants who required resuscitation. Members of the research team placed the sensors for each of the pulse oximeters being compared simultaneously, one sensor on each foot of the same baby. Care provided routinely, without interference by the research team. The time elapsed until a reliable SpO2 was obtained was recorded using a digital chronometer. Statistical comparisons included chi-square and student's T-test.ResultsThirty-two infants were enrolled; median gestational age 32 weeks. Seventeen paired measurements were made with the Radical-7 and Biox 3700; mean time to a stable reading was 20.2 ± 7 sec for the Radical-7 and 74.2 ± 12 sec for the Biox 3700 (p = 0.02). The Radical-7 and the N- 395 were paired on 15 infants; the times to obtain a stable reading were 20.9 ± 4 sec and 67.3 ± 12 sec, respectively (p = 0.03).ConclusionThe time to a reliable reading obtained simultaneously in neonatal critical situations differs by the type of the pulse oximeter used, being significantly faster with Masimo Signal Extraction Technology. This may permit for better adjustments of inspired oxygen, aiding in the prevention of damage caused by unnecessary exposure to high or low oxygen.

Pulse oximetric thresholds for tonsillectomy and adenotomy in children: significance of 1–2% decline in oxyhemoglobin saturation

We aimed to establish optimal overnight pulse oximetric thresholds for determining the indication of tonsillectomy and adenotomy (TA) in children by revising the definition of 'desaturation'. One hundred and thirty four children scheduled for TA (TA group, 5.3 +/- 1.4 years old) and 112 otherwise healthy children scheduled for elective minor surgery (control group, 5.4 +/- 1.5 years old) were enrolled into this prospective study. Data were recorded and stored every 10 s using Nellcor N-395. Desaturation/resaturation events were defined as x% change (x = 1-4) of SpO2 (oxyhemoglobin saturation by pulse oximetry) in 10 s. The desaturation/resaturation indices were calculated as events per hour of total sleeping time. For each index, a wide range of temporary thresholds was set. The optimal thresholds for TA were the ones that maximized the weighted average for sensitivity, specificity (based on whether the index improved or not after TA), and the percentage of the control children whose indices were below the threshold. For all the indices, the optimal thresholds that fulfilled the above condition were determined. Compared with the x = 3-4% results, the application of x = 1-2% approximately doubled the TA patients whose preoperative 'positive' indices improved after TA, with the weighted averages of 84.3-92.3% as described above. By defining desaturation/resaturation as a 1-2% change in SpO2 from the preceding value, children with adenotonsillar hypertrophy whose pulse oximetric indices are expected to improve after TA can be detected by pulse oximetry with relatively high sensitivity and specificity.

Acute effects of vecuronium on pulmonary function and hypoxemic episodes in preterm infants

Varying effects of pancuronium on neonatal pulmonary mechanics have been documented, including a decrease in pulmonary compliance or no significant change in compliance; but measurements of respiratory mechanics or quantification of episodes of hypoxemia in preterm newborns receiving vecuronium (Norcuron, Bedford Labs, Bedford, OH, USA) have not been reported. The objective of the present study was to quantify the short-term effects of vecuronium on pulmonary mechanics and episodes of hypoxemia in preterm infants receiving mechanical ventilation. A total of 15 preterm infants (birthweight 610-1560 g, gestational age 25-32 weeks, postnatal age 0.2-22 days) was studied. The initial dose of vecuronium used for the study was 0.2 mg/kg i.v. Measurements of respiratory mechanics were obtained 1 h prior to and 1 h after the initial dose of vecuronium at comparable ventilator settings and fractional inspired oxygen concentration (FiO(2)). Dynamic respiratory compliance and respiratory resistance were calculated by two-factor least mean square analysis. Pulse oximeter oxygen saturation (SpO(2)) was measured during both 1 h intervals with the Nellcor N-200 oximeter, a computer, and a software program for quantification of episodes of hypoxemia. Heart rate and blood pressure were also monitored. There were no significant differences in tidal volume, respiratory compliance, or respiratory resistance when comparing measurements obtained before and after vecuronium administration. However, fewer episodes of hypoxemia (SpO(2) < 85%, P = 0.025; and SpO(2) < 80%, P = 0.04) were observed during muscle relaxation. No significant changes in heart rate or blood pressure were noted. The preliminary data indicate: (i) a single dose of vecuronium does not significantly change respiratory compliance or respiratory resistance in preterm infants and (ii) during muscle relaxation fewer episodes of desaturation (hypoxemia) are observed.

Decreased accuracy of pulse oximetry measurements during low perfusion caused by sepsis: is the perfusion index of any value?

To evaluate the effects of deteriorating perfusion caused by sepsis on the accuracy of pulse oximetry measurements using two more recently available techniques (Nellcor N-395 and Masimo Radical) and to evaluate the perfusion index as a marker of impaired peripheral perfusion to indicate that accuracy of pulse oximetry readings may be affected. Interventional cohort study in a university animal research facility. Thirty-seven adult anesthetized, ventilated rabbits. Pneumonia/sepsis was induced by tracheal instillation of Escherichia coli. Oxygen saturation and perfusion index as a marker of peripheral perfusion were measured by pulse oximetry (SpO2) and recorded continuously for 8 h. Arterial oxygen saturation (SaO2) was measured every 30 min by CO oximetry, and bias (SpO2 - SaO2) was calculated at each time point for each device to assess time-dependent changes in bias. Bias increased significantly across time for both devices tested comparing the first with the second half of the experimental period. Bias measurements during the second half of the experimental time were beyond the +/-3% error limit in 21.4% of cases with Nellcor and in 22.6% with Masimo. A lower perfusion index was associated with increased bias, but sensitivity, specificity, and positive and negative predictive values of this marker for increased bias was very limited. We conclude that accuracy of pulse oximetry measurements was considerably affected with both devices with progressively deteriorating hemodynamics in this animal model of severe sepsis. Perfusion index as a marker for increased risk of bias was not a useful tool.

Fetal Pulse Oximetry and Neonatal Outcome: A Study in a Developing Country

The aim of this cohort, prospective study was to compare the diagnostic value of intrapartum fetal pulse oximetry (FPO) with that of fetal scalp blood gas (FSBG) for an abnormal neonatal outcome in cases with abnormal fetal heart rate (FHR) tracings. Fetal oxygen saturation was continuously monitored with Nellcor N-400 FPO during labor. Simultaneous FSBG determinations were obtained. The results were analyzed in relation to umbilical arterial cord blood pH and neonatal outcome. Studied FPO cutoff levels were 30 and 40% hemoglobin saturation and that of FSBG pH was 7.2. During the study, there were 9825 deliveries; 415 had abnormal FHR. Only 150 fulfilled the whole screening panel. When the outcome variable was umbilical arterial pH, the positive predictive values of the three methods (FPO30, FPO40, FSBG) were 57, 61 and 65% and the negative predictive values were 43, 39 and 35% respectively. The sensitivity of FPO30 was highest (75%). Considering abnormal neonatal outcome, again the sensitivity was also highest for FPO30 (89%). The sensitivity of FSBG was 82%. The specificity of the three methods were 53, 49 and 38% respectively. The diagnostic value of intrapartum FPO compares favorably with FSBG. FPO seems to be a reliable and less invasive tool and may decrease unnecessary interventions and unnecessary fetal scalp blood sampling in cases of suspected fetal distress. The FPO cutoff of 30% saturation defined by previous studies appears to be appropriate.

Unattended home sleep studies for the evaluation of suspected obstructive sleep apnoea syndrome in children

Children suspected of obstructive sleep apnoea syndrome (OSAS) are traditionally investigated in hospital with overnight sleep studies, and single-channel pulse oximetry is the commonest form of initial study. A prospective study was conducted comparing unsupervised sleep studies, using a Nellcor N-395 pulse oximeter, performed in hospital and at home. Two hundred and eleven patient studies were completed in 18 months, 158 in hospital and 53 at home. The median age of patients was four years in both groups. The mean study duration was 9 h 5 min in hospital and 9 h 12 min at home (P = 0.75). The mean time in pulse search was 0.4% (SD = 0.7) in hospital and 0.2% (SD = 0.4) at home (P = 0.008). The number of failed studies was 96 of 254 (38%) in hospital and three of 56 (5%) at home (P < 0.001). Overall, 149 hospital bed days were saved (at pounds 690 per bed day), representing pounds 68,540 saved annually. The results show that unattended home sleep studies in the form of overnight pulse oximetry can be performed to a standard better than hospital studies, where local community nursing facilities exist.

Episodes of hypoxemia during synchronized intermittent mandatory ventilation in ventilator‐dependent very low birth weight infants

Distinct patterns of asynchrony, and episodes of hypoxemia, may occur in a spontaneously breathing preterm infant during conventional intermittent mandatory ventilation (IMV) on traditional time-cycled, pressure-limited ventilators. Synchronized IMV (SIMV) and assist/control ventilation are frequent modes of patient-triggered ventilation used with infant ventilators. The objective of this study was to use computerized pulse oximetry to quantify the occurrence of episodes of hypoxemia (oxygen desaturation) during SIMV vs. IMV, in preterm infants < or = 1,250 g who required mechanical ventilation at > or = 14 days of age. We performed a randomized, crossover study with each infant being randomized to IMV or SIMV (Infant Star ventilator) for initial testing for a 1-hr period. Patients were subsequently tested on the alternate modality after a stabilization period of 10 min at the same ventilator and fractional inspired oxygen concentration (FiO2) settings. Pulse oximetry data were obtained with a Nellcor N-200 monitor, a microcomputer, and a software program (SatMaster). An investigator blinded to the randomized assignment evaluated all measurements. Eighteen very low birth weight (VLBW) infants with a birth weight of 777 +/- 39 g (mean +/- SEM) and gestational age 25.1 +/- 0.3 weeks were studied. The average pulse oximeter oxygen saturation (SaO2) was higher on SIMV than IMV (P < 0.01). During SIMV, these infants had significantly fewer episodes of hypoxemia (duration of episodes of oxygen desaturation as a percentage of scorable recording time) to 86-90% SaO2 (P < 0.01), 81-85% SaO2 (P < 0.01), and 76-80% SaO2 (P < 0.05) when compared to IMV. There was also a significant decrease in percentage of time of desaturation to SaO2 < 90% (P = 0.002), < 85% SaO2 (P = 0.003), and < 80% SaO2 (P = 0.02) during SIMV vs. IMV. Our preliminary findings indicate that the use of SIMV in a population of VLBW ventilator-dependent infants (> or = 14 days of age) results in better oxygenation and decreased episodes of hypoxemia as compared to IMV.

Clinical Evaluation of the Effects of Signal Integrity and Saturation on Data Availability and Accuracy of Masimo SET?? and Nellcor N-395 Oximeters in Children

Clinical Evaluation of the Effects of Signal Integrity and Saturation on Data Availability and Accuracy of Masimo SET?? and Nellcor N-395 Oximeters in Children

Motion resistant pulse oximetry in neonates

Background: Pulse oximetry is widely used in neonates. However, its reliability is often affected by motion artefact. Clinicians confronted with questionable oxygen saturation (Spo2) values often estimate the reliability by...

Predictive value of pulse oximetry and fetal scalp blood pH in the case of meconium-stained amniotic fluid

Objective: To compare the predictive value of intrapartum fetal pulse oximetry to that of fetal scalp blood pH for an abnormal neonatal outcome in the case of thick meconium. Study design: A prospective multicenter observational study was performed from June 1994 to November 1995. Fetal oxygen saturation was monitored using a Nellcor N-400 fetal pulse oximeter in case of abnormal FHR. The last readings of fetal oxygen saturation and fetal scalp blood pH before birth were used to assess the ability of both techniques to predict an abnormal neonatal status. Results: At a 30% cutoff, the negative predictive value of fetal oxygen saturation was not altered in case of meconium when compared to clear amniotic fluid (79 and 83%, respectively). Fetal scalp blood pH at a 7.20 threshold had a poor negative predictive value in case of meconium when compared to clear amniotic fluid (56% versus 88%, respectively). The receiver operator characteristic curve showed similar performance of fetal scalp blood pH and pulse oximetry in cases with clear amniotic fluid. In cases with meconium, the performance of fetal scalp blood pH was poor, whereas that of pulse oximetry remained unchanged. In three cases with meconium below the vocal cords, a drop in fetal oxygen saturation was observed during labor whereas fetal scalp blood pH remained within normal values. Conclusion: The predictive value of fetal scalp blood pH is poor in case of meconium, whereas the predictive value of pulse oximetry seems to be unchanged in this situation.

A Combined Ear Sensor for Pulse Oximetry and Carbon Dioxide Tension Monitoring: Accuracy in Critically Ill Children

A Combined Ear Sensor for Pulse Oximetry and Carbon Dioxide Tension Monitoring: Accuracy in Critically Ill Children

Effects of Signal Integrity and Saturation on Data Availability in Masimo SET and Nellcor N395 Pulse Oximeters

Effects of Signal Integrity and Saturation on Data Availability in Masimo SET and Nellcor N395 Pulse Oximeters

Clinical Evaluation of Masimo SET and Nellcor N395 Oximeters during Optimal Signal Conditions in Difficult-to-Monitor Neonates

Clinical Evaluation of Masimo SET and Nellcor N395 Oximeters during Optimal Signal Conditions in Difficult-to-Monitor Neonates

Effects of Signal Integrity and Saturation on Accuracy of Masimo SET and Nellcor N395 Pulse Oximeters

Effects of Signal Integrity and Saturation on Accuracy of Masimo SET and Nellcor N395 Pulse Oximeters

Reliability of Conventional and New Pulse Oximetry in Neonatal Patients

Pulse oximetry is widely used in the NICU, but clinicians often distrust the displayed values during patient motion, i.e., questionable oxygen saturation (SpO(2)) and pulse rate (PR) values. Masimo Corporation (Irvine, CA) has developed pulse oximetry with claims of resistance to sources of interference. To test this premise, we compared the performance of the Masimo SET pulse oximeter to a conventional device, Nellcor N-200, and then with three other new-generation pulse oximeters, Nellcor N-395, Novametrix MARS, and Philips Viridia 24C. We studied 26 nonsedated NICU infants who were on supplemental oxygen and/or mechanical ventilation. ECG heart rate (HR) from a bedside monitor and SpO(2) and PR from the two pulse oximeters were captured by a PC for a total of 156 hours. The ECG HR and pulse oximeter spectral waveform were analyzed at alarms for hypoxemia (SpO(2)< or = 85%) and/or bradycardia (HR< or = 80 bpm). We then compared the performance of the Masimo SET to three other new-generation pulse oximeters, Agilent Viridia 24C, Nellcor N-395, and Novametrix MARS, in a similar population of seven infants for a total of 28 hours. We added to the test criteria the ability of the various pulse oximeters to track acute changes in HR. Compared with Nellcor, Masimo SET had 86% fewer false alarms, which also were shorter in duration, resulting in 92% less total alarm time. Masimo SET also identified nearly all bradycardias versus 14% for the Nellcor. Compared with the new-generation pulse oximeters, false desaturations, data drop-outs, and false bradycardias were lowest for Masimo SET, as was the capture of true desaturations and bradycardias. Notably, the new-generation devices differed greatly in their ability to detect changes in HR (i.e., the frequency of frozen PR during times of ECG HR change was 0, 6, 11, and 46 for Masimo, Nellcor, Philips, and Novametrix, respectively). Masimo SET pulse oximetry recorded markedly fewer false SpO(2) and PR alarms and identified more true hypoxic and bradycardic events than either conventional or other new-generation pulse oximeters. Masimo SET also most closely reflected the ECG rate irrespective of accelerations or decelerations in HR. Routine use of Masimo SET pulse oximetry in the NICU could improve clinician confidence in the parameter leading to more judicious titration of oxygen with possible reductions in hypoxic (e.g., pulmonary hypertension) and hyperoxic (e.g., retinopathy of prematurity) pathology. Additionally, a more trustworthy technology should equate with fewer confirmatory arterial blood gas analyses (less blood loss), and faster weaning from the mechanical ventilation (less chronic lung disease).

Oxygen saturation in healthy newborn infants immediately after birth measured by pulse oximetry.

Pre- and postductal arterial oxygen saturation (SpO2) rates were measured in 50 healthy vaginally delivered newborn infants to establish reference values of SpO2 rates immediately after birth. We compared the SpO2 values in the pre- and postductal areas and assessed the influence of oxitocin and analgetics applied during delivery. Fifty neonates were examined by the 2nd minute (min) of life using Nellcor N-3000 pulse oximeters on the right hand and foot. Measurements were carried out until a SpO2 of 95% was achieved. Heart rates were registered simultaneously. Two min after birth the mean preductal SpO2 was 73% (44-95%) and 67% (34-93%) in the postductal region. SpO2 rates of > 95% were reached after 12 min (2-55 min) preductally and after 14 min (3-55 min) postductally. Our results demonstrate that it takes 12-14 min for healthy neonates to reach an oxygen saturation of 95% prerespectively postductal, in some cases even 55 min. All neonates were in good clinical condition and didn't require any supplemental oxygen. Additionally, we were able to show that epidural anaesthesia (PDA) during delivery increases the heart rate of the newborn infant.

Desaturation events in neonates during mechanical ventilation.

This study examines the accuracy of oxygen saturation measured by Nellcor N200 pulse oximetry (SpO2) compared with arterial oxygen saturation (SaO2) measured through a three-wavelength fiberoptic umbilical catheter in 10 neonates who needed mechanical ventilation. Real-time SaO2 was validated with a reference method every 4 hours. Oxygen saturation readings (SaO2 and SpO2), along with pulse rate and pulsation, were recorded continuously every second through a computer. Concurrent care events and neonatal responses were recorded. Data were completed on 10 neonates who had an umbilical arterial catheter. Desaturation events (<90%) as measured by both SaO2 and SpO2 were described and compared. A total of 959 desaturation events occurred during an average of 51 hours of monitoring per subject. Of these events, 63% were associated with frozen SPO2 readings, and 18% of frozen readings occurred when SaO2 was <90%. Bias for SpO2 compared with SaO2 was +5.03%, with 5.6% of the readings outside the range of two standard deviations. However, 67% of the readings exceeded the 4% difference criterion between measurements. Future studies need to examine the desaturation events in relation to oxygenation status as measured by different methods.

A prototype device for standardized calibration of pulse oximeters II.

There is no commonly accepted in vivo calibration method for pulse oximeters available up to now. On the basis of a prototype device for the calibration of pulse oximeters which was introduced recently, a second approach based on the same concept was tackled in order to design a reliable method for standardized calibration of pulse oximeters. An extensive clinical database of time-resolved optical transmission spectra of patient fingers is used to simulate the behavior of patients. A device which is capable of playing back these spectroscopic data to pulse oximeters, and a database where the oxygen status measured with the reference method (Co-Oximetry) is stored, are the main parts of the concept. The playback device has an artificial finger as interface to the pulse oximeters and serves to collect light from the pulse oximeter for analysis and to playback simulated light to the pulse oximeter. The light intensity emitted by two LEDs which illuminates the pulse oximeter detector is controlled via a computer in such a way that it is the same as if the pulse oximeter light had passed the finger. The pulse oximeter display during the data playback can thus be compared to the true SaO2 of the patient. The device is tested with 4 pulse oximeters based on 100 patient spectra. For the four pulse oximeters used in this investigation, an Agilent Technologies CMS monitor (formerly Hewlett-Packard), an Ivy 2000 with Masimo Set technology and Nellcor N-3000 and N-395, there is good correlation between SPO2 and SaO2, and mean and standard deviation of in vivo SpO2-SaO2 and playback SpO2-SaO2 are in good agreement. For two instruments, Nellcor N3000 and Agilent CMS Monitor, a quantitative comparison between the in vivo and in vitro SpO, results was derived. A mean of the deviation playback vs. in vivo SpO2 is less than 0.5% SpO2. The error limits are comparable with the calibration error of the conventional calibration routine. The device is also capable of data playback even in situations with rapid desaturation changes, as displayed in Figure 2. For the other tested pulse oximeters the results are comparable. Compared to the first prototype the current version is simpler and less expensive in production. Many of previously existing problems are solved and the applicability to a large variety of pulse oximeters and sensors is given. The novel concept for the calibration of pulse oximeters is a tool for assessing the performance of pulse oximeters.