Capillary Blood Gas Sampling Research Articles

A-343 Novel In-Line Hemolysis Detection on a Blood Gas Analyzer for Capillary Samples

Abstract Background Point-of-care (POC) blood gas and electrolyte analyzers utilizing whole blood as the predominant sample type are blinded by the presence of hemolysis until today. Moreover, capillary samples are particularly vulnerable to in-vitro hemolysis due to excessive force applied during sample collection. Here, we introduce the GEM Premier 7000 with iQM3 (GEM 7000) which incorporates automatic, in-line hemolysis detection in capillary blood gas samples without a need for additional sample volume or reagents. Methods The hemolysis detection module which is integrated into the disposable GEM cartridge uses acoustophoretic technology and photometric measurements to detect hemolysis in whole blood. In GEM 7000, hemolysis of ≥ 116 mg/dL was found to have significant interference with potassium results. A hemolysis flag is presented as the degree of hemolysis: none (0 - 50 and 51 - 115), mild (116 - 200 and 201 - 300), moderate (301 - 400), and gross (≥401). Due to volume limitations with native capillary samples and challenges in assessing hemolysis levels with a comparator assay, venous blood spiked volumetrically with hemolysate and transferred to capillary devices was used to verify the hemolysis flag performance. An agreement analysis was performed using the Roche cobas hemolysis value. The device's (GEM 7000) ability to flag hemolyzed capillary samples is demonstrated in a simulated clinical setting using native and contrived fingerstick capillary samples. Results Hemolysis verification with transferred capillary samples demonstrated that 98.2% (274/279) of samples were correctly flagged based on the cobas hemolysis value of spiked hemoglobin. Hemolysis in the native capillary samples (N = 235) was primarily distributed in the 0-50 mg/dL range. Additionally, native capillary samples altered using vigorous flea mixing (> 1 minute) showed hemolysis distribution over a wide hemolysis degree (none to gross), and their potassium results were flagged accordingly. Conclusions By providing integrated hemolysis detection in capillary blood sample measurements, the GEM Premier 7000 with iQM3 system can provide quality and confidence in the clinical interpretation of critical results such as potassium.

Comparison of mathematically arterialised venous blood gas sampling with arterial, capillary, and venous sampling in adult patients with hypercapnic respiratory failure: a single-centre longitudinal cohort study

BackgroundAccurate arterial blood gas (ABG) analysis is essential in the management of patients with hypercapnic respiratory failure, but repeated sampling requires technical expertise and is painful. Missed sampling is common...

AARC Clinical Practice Guidelines: Capillary Blood Gas Sampling for Neonatal and Pediatric Patients.

In the absence of an indwelling arterial catheter, capillary blood gas sampling may be used to evaluate the acid/base and ventilation status of neonatal and pediatric patients with cardiorespiratory conditions. These guidelines were developed from a comprehensive review of the literature to provide guidance for the collection, handling, and interpretation of blood obtained from an arterialized capillary sample. Capillary and venous blood gas measurements are a useful alternative to arterial blood gas measurements for neonatal and pediatric patients who do not require close monitoring of [Formula: see text] In the presence of alterations in body temperature, blood pressure, or peripheral perfusion, agreement between a capillary blood gas with an arterial sample is recommended to determine whether changes in these physiologic conditions reduce reliability. Perfusion to the sample site should be assessed and preference given to blood sampling from a well perfused site, and blood should be analyzed within 15 min of sampling to minimize the propensity for pre-analytical errors. Clinicians should consider re-collecting a blood sample, obtained from an artery, vein, or capillary, when the blood gas or analyte result interpretation does not align with the patient's clinical presentation. A pneumatic tube system can be reliably used to transport blood gas samples collected in a syringe and capillary tube to a clinical laboratory for analysis. To reduce the cumulative pain effect and risk of complications, the capillary puncture procedure should be minimized when possible. Non-pharmacologic interventions should be used to reduce pain associated with capillary blood gas sampling. Automatic lancets are preferred to puncture the skin for capillary blood gas collection.

Detection of Chronic Hypoventilation Among Infants With Robin Sequence Using Capillary Blood Gas Sampling.

To describe the use of capillary blood gas (CBG) sampling to detect and quantify hypoventilation in infants with Robin sequence (RS). Case series with chart review at two institutions. Infants with RS presenting over a 10-year period were identified using departmental databases. CBG values obtained during infancy or until airway intervention (AI) were reviewed. From 2008 to 2018, 111 infants with RS were identified as having had been assessed and managed from birth or transfer until discharge home and having CBG data available. In most cases, CBG sampling was obtained every other day until intervention or discharge. A total of 81 (73%) infants required AI: 72 (89%) underwent mandibular distraction osteogenesis, five (6%) underwent tracheotomy, and four (5%) were discharged home with a nasopharyngeal airway. The mean PCO2 at day of life (DOL) 7-30 for the AI group was 52.7 mmHg (95% confidence interval: 51.7-53.7) and for the no AI group was 45.9 mmHg (44.8-47.0; P < .0001). The mean HCO3 at DOL 7-30 for the AI group was 29.8 mEq/L (29.4-30.1) and for the no AI group was 27.0 mEq/L (26.5-27.4; P < .0001). Receiver operating characteristic curves were created for maximum PCO2 and HCO3 values and cutoffs were established by optimizing a balance of sensitivity and specificity. Infants requiring AI surpassed the PCO2 and HCO3 cutoff at a median of DOL 9. Among infants with RS and hypoventilation, objective measures of respiratory acidosis may be apparent by DOL 9. 4 Laryngoscope, 131:2789-2794, 2021.

Arterialised Capillary Blood Gases in Accident and Emergency Department Patients - a Reliable Alternative to Arterial Sampling?

&#x0D; &#x0D; &#x0D; &#x0D; OBJECTIVES: Many patients with respiratory complaints who present to the Accident &amp; Emergency (A &amp; E) department have an arterial blood gas analysis performed at some point. It is our belief that there is no difference between arterial and capillary blood gas values in patients presenting to the A &amp; E department. It is also anticipated that body temperature and blood pressure may play a part, so these will also be reported and associations will be investigated. METHODS: Patients who require arterial blood gas analysis at any stage during their stay in the A &amp; E department at the Northern General hospital of Sheffield are eligible for inclusion in the study. In total there were 32 patients. PROCEDURE:Transvasin cream was applied to the ear lobe to improve local blood flow by dilating the capillaries. When ten minutes have elapsed after the application of the Transvasin cream, a capillary sample is taken from the ear lobe by the researchers. CONCLUSION: From the t-tests conducted, no significant difference was seen between the arterial and capillary blood gas samples for the parameters pO2 and O2 saturation. However, for pCO2, pH and [HCO3] there were significant differences observed. This result seems to disagree with the findings of most other studies that have so far shown stronger correlations generally for pH, pCO2 and bicarbonate, than for oxygen measuring parameters.&#x0D; &#x0D; &#x0D; &#x0D;

Arterialised earlobe capillary blood gases in the COPD population.

Arterialised ear lobe capillary blood (ELCB) gas sampling is a widely used clinical procedure undertaken across both primary and secondary care settings. The prevalence of this sampling method has grown among health professionals, coupled with a growing demand for domiciliary oxygen therapy in the UK, in particular for those who have chronic obstructive pulmonary disease (COPD). Research studies supporting arterialised ELCB gas sampling show inconsistencies in technique, and a survey of respiratory nurses' current practice demonstrated wider inconsistencies. In the absence of national clinical guidelines to direct this practice, and an acknowledged and accepted under-calculation of partial pressure of oxygen, this article investigates the sampling method used to obtain arterialised ELCB gas sampling and consequently questions its reliability in practice.

Curable hypoxia in an octogenarian with an undiagnosed inherited condition

An 84-year-old gentleman was referred to the chest clinic with low oxygen saturations on pulse oximetry. He reported breathlessness and wheeze since his retirement as a surveyor 16 years previously. His exercise tolerance was 350 m. He had pre-existing diagnoses of chronic obstructive pulmonary disease and hypertension. He had no avian or occupational exposures, a minimal smoking history while in his teens and had not smoked since, and no history of transient ischaemic attack or cerebrovascular accident. On examination, he was comfortable with no respiratory distress but had slight peripheral cyanosis and oxygen saturations of 89% on room air. Auscultation of his chest revealed increased vocal fremitus and crackles over the right lower lobe with occasional wheeze. The patient was investigated using lung function testing, capillary blood gas sampling, a chest radiograph and thoracic computed tomography (CT). His haemoglobin at presentation was 16.1 g·dL−1. ### Lung function The results of the lung function investigations performed as shown in table 1. Supine and erect spirometry demonstrated oxygen saturations of 93% when lying down and 86% on sitting. There was no significant reversibility to 2.5 mg nebulised salbutamol. View this table: Table 1 Lung function A capillary blood gas taken on air at rest showed an oxygen tension ( P O2) of 8.0 kPa (normal 12.0–15.0 kPa), a carbon dioxide tension ( P CO2) of 4.4 kPa (normal 4.5–6.1 kPa) and pH of 7.44 (normal 7.36–7.42). ### CT CT images are shown in figure 1. Figure 1 a) Axial and b) coronal CT slice. ### Task 1 1. What is seen on the initial CT scan (fig. 1). 2. What conditions can be associated with this? 3. Can you interpret the lung function results (table 1)? ### Answer 1 1. There is a 2-cm vascular abnormality in the right lower lobe consistent with a pulmonary arteriovenous malformation (PAVM). 2. PAVMs are most commonly seen with hereditary haemorrhagic telangiectasia (>90%) and post-cardiac …

Yoğun Bakımda Kapiller Kan Gazı Ölçümünün Değeri

Arterial blood gas ( ABG ) sampling represents the gold standard for determining the patients’ acid-base and ventilatory status. However, it has many drawbacks. This study assessed the relationship and agreement between arterial and capillary measurements in adult intensive care unit ( ICU ) patients. ABG and capillary blood gas (CBG) samples were obtained from 49 adult and 51 elderly ( a total of 100 ) patients with cardiopulmonary disorder, cerebrovascular accident, intoxication, multiple trauma, and metabolic coma. All samples, collected at the same time, were analyzed. The kendall’s tau rank correlation, unpaired t-test, paired-t test and Bland-Altman method which is used for measure ment of agreement, were used for analysis. The median age was 65 years ( min: 18, max: 90 ). There was a significant correlation between ABG and CBG values of pH, PCO 2 , and HCO 3 ( P < 0.001 ). The agreement between measurements of pH, PCO 2 , and HCO 3 in ABG and CBG was good with mean differences of 0.0085, 3.049 mmHg, and 1.268 mmol / L, respectively. Despite a statistically significant correlation between arterial and capillary PO 2 ( P < 0.001 ), the agreement between capillary and arterial measurements of PO 2 was poor ( mean difference: 16.52, 95% CI: -23.74 to 56.79 ). Blood pressure and body temperature did not alter the correlations and agreement between measurements in elderly and adult groups and all together ICU patients. Capillary blood samplings provide an accurate assessment of pH, PCO2, and HCO3 and can be used to reliably measure the acid-base and ventilatory status of patients in the presence of any limitation of or contraindication to ABG in ICU.

Capillary blood gas as a substitute for arterial blood gas: a meta-analysis

Arterial blood gas sampling forms a vital part of bedside investigation but is invasive and physician dependent. This study aimed to determine whether capillary blood gas sampling could provide an accurate and less invasive substitute for the measurement of blood gases and pH.

Institutional practices and policies in acid-base testing: a self reported Croatian survey study on behalf of the Croatian society of medical biochemistry and laboratory medicine Working Group for acid-base balance.

Introduction:The aim of this survey study was to assess the current practices and policies in use related to the various steps in the blood gas testing process, across hospital laboratories in Croatia.Materials and methods:First questionnaire was sent by email to all medical biochemistry laboratories (N = 104) within general, specialized and clinical hospitals and university hospital centres to identify laboratories which perform blood gas analysis. Second questionnaire with detailed questions about sample collection, analysis and quality control procedures, was sent only to 47 laboratories identified by the first survey. Questionnaire was designed as combination of questions and statements with Likert scale. Third questionnaire was sent to all participating laboratories (N=47) for additional clarification for either indeterminate or unclear answers.Results:Blood gas analysis is performed in 47/104 hospital laboratories in Croatia. In 25/41 (0.61) of the laboratories capillary blood gas sampling is the preferred sample type for adult patient population, whereas arterial blood sample is preferentially used in only 5/44 laboratories (0.11). Blood sampling and sample processing for capillary samples is done almost always by laboratory technicians (36/41 and 37/44, respectively), whereas arterial blood sampling is almost always done by the physician (24/29) and only rarely by a nurse (5/28). Sample acceptance criteria and sample analysis are in accordance with international recommendations for majority of laboratories. 43/44 laboratories participate in the national EQA program. POCT analyzers are installed outside of the laboratory in 20/47 (0.43) institutions. Laboratory staff is responsible for education and training of ward personnel, quality control and instrument maintenance in only 12/22, 11/20 and 9/20 institutions, respectively.Conclusions:Practices related to collection and analysis for blood gases in Croatia are not standardised and vary substantially between laboratories. POCT analyzers are not under the direct supervision by laboratory personnel in a large proportion of surveyed institutions. Collective efforts should be made to harmonize and improve policies and procedures related to blood gas testing in Croatian laboratories.

Neonatal blood gas sampling methods

Blood gas sampling is part of everyday practice in the care of babies admitted to the neonatal intensive care unit, particularly for those receiving respiratory support. There is little published guidance that systematically evaluates the different methods of neonatal blood gas sampling, where each method has its individual benefits and risks. This review critically surveys the available evidence to generate a comparison between arterial and capillary blood gas sampling, focusing on their relative accuracy and complications, as well as briefly mentioning the management of such complications. This evidence-based summary and guidance should help inform best practice in the neonatal intensive care unit, and minimise the exposure of babies to unnecessary and potentially serious risk. The most accurate and non-invasive method of measuring oxygenation is oxygen saturation monitoring. Indwelling arterial catheters are a practical, reliable and accurate method of measuring acid-base parameters, provided they are inserted and maintained with the proper care. Capillary blood gas sampling is accurate, and a good substitute for radial ‘stab’ arterial puncture avoiding many of the complications of repeated arterial puncture.

Capillary blood gas sampling at annual assessment – a service review

Capillary blood gas sampling at annual assessment – a service review

Clinical utility of arterialised capillary earlobe sampling in the critical care setting

The purpose of this study was to determine whether earlobe capillary blood gas sampling, performed by nonmedical staff, provides a clinically acceptable estimate of the pH, pCO2 and pO2 in critically ill adults.

Two-rescuer CPR results in hyperventilation in the ventilating rescuer

The “Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care – International Consensus on Science” recommend a tidal ventilation volume of 10 ml/kg body-weight without the use of supplemental oxygen during two-rescuer adult cardiopulmonary resuscitation (CPR). This relates to a ventilation volume of about 6.4 l/min. Additionally, the first aid provider ventilating the victim will breathe for him/herself during the external chest compression period adding another 3.2 l/min of ventilation. Finally, a deep breath is recommended before each ventilation to increase the end-expiratory oxygen concentration of the air exhaled. To investigate the effects of these recommendations, 20 healthy volunteers were asked to perform two-rescuer CPR in a lung model connected to a BLS-manikin. End-tidal carbon dioxide, oxygen saturation, and heart rate were recorded continuously. Capillary blood gas samples were collected and non-invasive blood pressure was recorded prior to the start of external chest compressions and immediately after the end of each measurment period. Furthermore, hyperventilation related symptoms reported by the volunteers were also recorded. The data reveal a significant decrease in capillary and end-tidal carbon dioxide pressure in the volunteers ( P < 0.001). Additionally, in 75% of test persons multiple hyperventilation associated symptoms occurred. Ventilation during two-rescuer CPR performed according to the Guidelines 2000 may cause injury to the health of first aid providers. To minimize hyperventilation, both rescuers should exchange their positions at intervals of 3–5 min. These data challenge the recommendation to take a deep breath prior to each ventilation.

Artificial ventilation for basic life support leads to hyperventilation in first aid providers

The ‘Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care — International Consensus on Science’ recommend an artificial ventilation volume of 10 ml/kg bodyweight (equivalent to a tidal volume of 700–1000 ml) without the use of supplemental oxygen in adults with respiratory arrest. For first aid providers using the mouth-to-mouth or mouth-to-nose-ventilation technique, respectively, a ventilation volume of approximately 9.6 l/min results. Additionally, a deep breath is recommended before each ventilation to increase the end-expiratory oxygen concentration of the air exhaled by the first aid provider. To investigate the effects of these recommendations in healthy volunteers, test persons were asked to ventilate an artificial lung model for a period of up to 10 min. The tidal volume was set at 800 ml at a breathing rate of 12/min. End-tidal carbon dioxide, oxygen saturation (measured by pulse oximetry), and heart rate were measured continuously. Capillary blood gas samples were collected and non-invasive blood pressure readings were recorded prior to the start of ventilation and immediately after the end of the measuring period. The data reveal a statistically significant and clinically relevant decrease in end-tidal carbon dioxide pressure ( P<0.001, median decrease 14 mmHg), and the occurrence of hyperventilation-associated symptoms such as paraesthesia, dizziness, and carpopedal spasms in more than 75% of the participants. Clinically and statistically significant hyperventilation results in first aid providers performing artificial ventilation according to the guidelines. This artificial ventilation is associated with a significant decrease in capillary and end-tidal carbon dioxide pressure as well as with multiple symptoms of an acute hyperventilation syndrome. Ventilation performed according to these guidelines may cause injury to the health of the first aid provider. Rescuers ventilating the victim should be replaced at regular intervals and the recommendation to take a deep breath before each ventilation should not be upheld in order to minimise the risk of hyperventilation.

Capillary and arterial blood gases in hemorrhagic shock: a comparative study.

To determine whether capillary blood gas samples accurately reflect the information obtained from arterial blood gas samples in a porcine hemorrhagic shock model. Randomized prospective study. Animal research laboratory at a children's hospital. Fifteen adult Yorkshire pigs. Tracheally intubated, ventilated, and anesthetized pigs were randomly assigned to either a control group (n = 10) or a hemorrhagic shock group (n = 5). After instrumentation, the hemorrhagic shock group underwent a 40-mL/kg hemorrhage over 2 hrs, while the control group did not. Animals were then monitored over a 3-hr period. Simultaneous arterial blood gas and capillary blood gas samples were obtained from each animal by using standardized technique. Capillary blood gas pH accurately predicted arterial blood gas pH in both control and hemorrhagic shock groups (r = .94, p < .01, and r = .78, p < .01, respectively). Bland-Altman analysis revealed a mean difference between arterial blood gas pH and capillary blood gas pH of 0.016 (95% limit of agreement, +/-0.037) in the control group vs. a mean difference between arterial blood gas pH and capillary blood gas pH of 0.075 (95% limit of agreement, +/-0.142) in the hemorrhagic shock group. Capillary blood gas Pco2 accurately predicted arterial blood gas Pco2 in the control group but not in the hemorrhagic shock group (r = .80, p < .01, and r = .13, p = .41, respectively). By Bland-Altman analysis, the mean difference between arterial blood gas Pco2 and capillary blood gas Pco2 was 3.9, with a 95% limit of agreement of +/-3.61 in the control group. In the hemorrhagic shock group, the mean difference between arterial blood gas Pco2 and capillary blood gas Pco2 was 11.7 with a 95% limit of agreement of +/-38.8. Hemorrhagic shock group capillary blood gas samples significantly overestimated Pco2 (Delta = 11.7, p < .01) and underestimated pH (Delta = 0.075, p < .01) compared with arterial blood gas samples. Capillary blood gas samples are poor predictors of Pco2 and pH in porcine hemorrhagic shock. These findings should be taken into account when capillary blood gas samples are used in the monitoring and management of subjects diagnosed with shock.

A Comparison of the Laryngeal Tube with the Laryngeal Mask Airway During Routine Surgical Procedures

The laryngeal mask airway (LMA; Laryngeal Mask Company, Henley-on-Thames, UK) is an established airway device, whereas the laryngeal tube (LT) is relatively new and therefore not as well investigated. Therefore, the purpose of the present prospective, randomized, controlled trial was to compare the LT with the LMA in routine clinical practice. In 50 patients undergoing general anesthesia for minor routine surgery, standardized anesthesia was induced and maintained with alfentanil and propofol. Patients were randomized to controlled ventilation (fraction of inspired oxygen = 0.4; fraction of inspired nitrous oxide = 0.6; tidal volume = 7 mL/kg; respiratory rate = 10 breaths/min) with the LT (n = 25) or the LMA (n = 25). Oxygen saturation was recorded before the induction of anesthesia and after the administration of oxygen. After 2 and 10 min of ventilation with the LT or LMA, oxygen saturation, end-expiratory carbon dioxide, expiratory tidal volume, and peak airway pressure were recorded. Capillary blood gas samples were taken before the induction of anesthesia and after 10 min of ventilation. Time of insertion and airway leak pressure of each device were measured. The time of insertion was comparable with both devices (LT versus LMA, median 21 s versus 19 s;P = not significant). Blood gas samples and ventilation variables revealed sufficient ventilation and oxygenation with either device (P = not significant). Peak airway pressure (LT, 17 ± 3 cm H2O; LMA, 15 ± 3 cm H2O) and airway leak pressure (LT, 36 ± 3 cm H2O; LMA, 22 ± 3 cm H2O) were significantly (P < 0.05) higher when using the LT compared with the LMA. In conclusion, using the LT and LMA resulted in comparable ventilation and oxygenation variables in this model of ASA physical status I and II patients undergoing routine surgical procedures. The newly developed LT may be a simple alternative device to secure the airway.

Effect of acute metabolic acid/base shifts on the human airway calibre

Acute metabolic alkalosis (NaHCO3), acidosis (NH4Cl), and placebo (NaCl) were induced in 15 healthy volunteers (12 females, median age 34 (range 24–56) years) in a double blind, placebo controlled study to evaluate the presence of the effects on airway calibre. Acid–base shifts were determined by capillary blood gas sampling. Measurements were performed at the maximal acid–base shift, 90 min after intervention. Airway resistance (Raw) and specific airway conductance (sGaw), were evaluated, as primary variables, pre and post intervention. Secondary variables, including bronchial responsiveness to histamine, maximal respiratory mouth pressures and grip strength, were evaluated post intervention. In alkalosis, base excess (BE) increased from –0.3 (−3.0–1.9) to 3.0 (1.0–4.8) mmol/l and pH increased from 7.41 (7.37–7.43) to 7.44 (7.39–7.47) (both P<0.01), accompanied by an increase in PaCO2: 4.7 (4.0–5.7) to 5.0 (4.7–6.1) kPa (P<0.05). Raw increased from 0.156 (0.134–0.263) to 0.169 (0.132–0.271) kPa s/L (P<0.05), sGaw decreased, but this was not statistically significantly. In acidosis, BE decreased from −0.2 (−2.0–2.2) to –3.5 (−6.3–1.1) mmol/l and pH decreased from 7.41 (7.39–7.45) to 7.36 (7.31–7.40) (both P<0.01), accompanied by a non-significant decrease in PaCO2. Changes in Raw and sGaw were contrary to those in alkalosis, but did not reach statistical significance. Acute metabolic acid–base shifts mildly influence the airway calibre in healthy human subjects.

Ureterosigmoidostomy: A Long-Term Follow-Up of 15 Patients with Urinary Diversion

We reviewed 15 patients who underwent 16 ureterosigmoidostomies from 1975 to 1989. The underlying disease was bladder exstrophy in 13 patients. Urinary diversions have been performed according to Mathisen in 15 patients, one reoperation has been performed according to Coffey. Standard post-operative controls consist of physical examinations, capillary blood gas samples, intravenous pyelograms, inulin clearance measurements, 123I-hippuran scintigraphies and colonoscopies. Results concerning continence are judged very satisfactory in 80% of patients. 34% of patients presented with one or more episodes of unilateral or bilateral pyelonephritis. Intravenous pyelograms showed improved or unchanged urinary tract dilatation in 45% of kidneys and moderate and severe dilatation in 55%. Inulin clearance remained in normal range in 4 out of 6 patients followed. Renal function assessed by means of renal scintigraphy remained unchanged in 61% of kidneys, slightly decreased in 22% and severely in 17%. All patients are kept on a sodium-citrate therapy. Only one patient shows growth disturbances. Out of 9 patients followed with colonoscopy, none showed signs of malignancy.

Capillary Blood Gases in the Neonate

Heel puncture capillary blood gas (CBG) measurements continue to be used in neonates for estimating arterial blood gas values. Review of the literature reveals general agreement that CBG PO2 values are of little use in predicting arterial PO2 and that CBG pH values are reliable predictors of arterial pH; opinion varies regarding CBG PCO2. We conducted a two-part study comparing postductal arterial and CBG values. First, 50 infants were studied, each only once. All infants had umbilical arterial catheters in place. Blood was obtained simultaneously from the umbilical artery catheter and the warmed heels. Results demonstrated poor predictability of arterial values from CBG pH and PCO2 as well as for PO2. Second, to determine if variation both within and among individuals was similar, repeated measurements were made in 27 additional infants comparable to the first group. We obtained 3 to 28 simultaneous postductal arterial and CBG samples from each infant. A random-effects nested analysis of variance indicated that for pH, variation was largely the result of between-subject or within-subject replicates effects, while for PO2 and PCO2, most variation was explained by differences between the two techniques (umbilical artery catheter vs CBG). The results indicate that CBG measurements do not accurately predict arterial values in neonates. Extreme caution should be used when management decisions are based on CBG values.