Why are congenital heart defects being missed?

OBJECTIVE: Congenital heart defects (CHD) are still missed frequently in prenatal screening programs, which can result in severe morbidity or even death. The aim of this study was to evaluate the quality of fetal heart images, obtained during the second-trimester standard anomaly scan (SAS) in cases of CHD, to explore factors associated with a missed prenatal diagnosis. METHODS: In this case-control study, all cases of a fetus born with isolated severe CHD in the Northwestern region of The Netherlands, between 2015 and 2016, were extracted from the PRECOR registry. Severe CHD was defined as need for surgical repair in the first year postpartum. Each cardiac view (four-chamber view (4CV), three-vessel (3V) view and left and right ventricular outflow tract (LVOT, RVOT) views) obtained during the SAS was scored for technical correctness on a scale of 0 to 5 by two fetal echocardiography experts, blinded to the diagnosis of CHD and whether it was detected prenatally. Quality parameters of the cardiac examination were compared between cases in which CHD was detected and those in which it was missed on the SAS. Regression analysis was used to assess the association of sonographer experience and of screening-center experience with the cardiac examination quality score. RESULTS: A total of 114 cases of isolated severe CHD at birth were analyzed, of which 58 (50.9%) were missed and 56 (49.1%) were detected on the SAS. The defects comprised transposition of the great arteries (17%), aortic coarctation (16%), tetralogy of Fallot (10%), atrioventricular septal defect (6%), aortic valve stenosis (5%), ventricular septal defect (18%) and other defects (28%). No differences were found in fetal position, obstetric history, maternal age or body mass index (BMI) or gestational age at examination between missed and detected cases. Ninety-two cases had available cardiac images from the SAS. Compared with the detected group, the missed group had significantly lower cardiac examination quality scores (adequate score (≥ 12) in 32% vs 64%; P = 0.002), rate of proper use of magnification (58% vs 84%; P = 0.01) and quality scores for each individual cardiac plane (4CV (2.7 vs 3.9; P < 0.001), 3V view (3.0 vs 3.8; P = 0.02), LVOT view (1.9 vs 3.3; P < 0.001) and RVOT view (1.9 vs 3.3; P < 0.001)). In 49% of missed cases, the lack of detection was due to poor adaptational skills resulting in inadequate images in which the CHD was not clearly visible; in 31%, the images showed an abnormality (mainly septal defects and aortic arch anomalies) which had not been recognized at the time of the scan; and, in 20%, the cardiac planes had been obtained properly but showed normal anatomy. Multivariate regression analysis showed that the volume of SAS performed per year by each sonographer was associated significantly with quality score of the cardiac examination. CONCLUSIONS: A lack of adaptational skills when performing the SAS, as opposed to circumstantial factors such as BMI or fetal position, appears to play an important role in failure to detect CHD prenatally. The quality of the cardiac views was inadequate significantly more often in undetected compared with detected cases. Despite adequate quality of the images, CHD was not recognized in 31% of cases. A high volume of SAS performed by each sonographer in a large ultrasound center contributes significantly to prenatal detection. In 20% of undetected cases, CHD was not visible even though the quality of the images was good. © 2019 Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

The effect of intrathecal bupivacaine/morphine on quality of recovery in robot-assisted radical prostatectomy: a randomised controlled trial.

Robot-assisted radical prostatectomy causes discomfort in the immediate postoperative period. This randomised controlled trial investigated if intrathecal bupivacaine/morphine, in addition to general anaesthesia, could be beneficial for the postoperative quality of recovery. One hundred and fifty-five patients were randomly allocated to an intervention group that received intrathecal 12.5 mg bupivacaine/300 µg morphine (20% dose reduction in patients > 75 years) or a control group receiving a subcutaneous sham injection and an intravenous loading dose of 0.1 mg.kg-1 morphine. Both groups received standardised general anaesthesia and the same postoperative analgesic regimen. The primary outcome was a decrease in the Quality of Recovery-15 (QoR-15) questionnaire score on postoperative day 1. The intervention group (n = 76) had less reduction in QoR-15 on postoperative day 1; median (IQR [range]) 10% (1-8 [-60% to 50%]) vs. 13% (5-24 [-6% to 50%]), p = 0.019, and used less morphine during the admission; 2 mg (1-7 [0-41 mg]) vs. 15 mg (12-20 [8-61 mg]), p < 0.001. Furthermore, they perceived lower pain scores during exertion; numeric rating scale (NRS) 3 (1-6 [0-9]) vs. 5 (3-7 [0-9]), p = 0.001; less bladder spasms (NRS 1 (0-2 [0-10]) vs. 2 (0-5 [0-10]), p = 0.001 and less sedation; NRS 2 (0-3 [0-10]) vs. 3 (2-6 [0-10]), p = 0.005. Moreover, the intervention group used less rescue medication. Pruritus was more severe in the intervention group; NRS 4 (1-7 [0-10]) vs. 0 (0-1 [0-10]), p = 0.000. We conclude that despite a modest increase in the incidence of pruritus, multimodal pain management with intrathecal bupivacaine/morphine remains a viable option for robot-assisted radical prostatectomy.

Fetuses with Isolated Congenital Heart Defects Show Normal Cerebral and Extracerebral Fluid Volume Growth: A 3D Sonographic Study in the Second and Third Trimester.

OBJECTIVE: The aim of our study is to explore whether the cerebral growth is delayed in fetuses with congenital heart defects (CHD) in the second and early third trimester. METHODS: A prospective cohort study was conducted in 77 CHD cases, with 75 healthy controls. 3D cerebral volume acquisition was performed sequentially. The volumes of the fetal hemicerebrum and extracerebral fluid were compared by linear regression analysis, and the Sylvian fissure was measured. RESULTS: Between 19 and 32 weeks of gestation, 158 measurements in cases and 183 measurements in controls were performed (mean 2.2/subject). The volume growth of the hemicerebrum (R2 = 0.95 vs. 0.95; p = 0.9) and the extracerebral fluid (R2 = 0.84 vs. 0.82, p = 0.9) were similar. Fetuses with abnormal oxygen delivery to the brain have a slightly smaller brain at 20 weeks of gestation (p = 0.02), but this difference disappeared with advancing gestation. CHD cases demonstrated a slightly shallower Sylvian fissure (mean ratio 0.146 vs. 0.153; p = 0.004). CONCLUSIONS: Our study shows no differences in cerebral growth, studied in an unselected cohort, with successive cases of isolated CHD. Even in the severest CHD cases, cerebral size is similar in the early third trimester. The cause and meaning of a shallower Sylvian fissure is unclear; possibly, it is a marker for delayed cerebral maturation or it might be an expression of decreasing amount of extracerebral fluid.

Right ventricular outflow tract obstruction in complicated monochorionic twin pregnancy.

OBJECTIVES: Severe right ventricular outflow tract obstruction (RVOTO) is a potential complication in recipient twins of twin-to-twin transfusion syndrome (TTTS) that requires postnatal follow-up or treatment. We aimed to evaluate pregnancy characteristics of neonates with RVOTO from complicated monochorionic twin pregnancies, determine the incidence of RVOTO in TTTS cases and construct a prediction model for its development. METHODS: This was an observational cohort study of all complicated monochorionic twin pregnancies with a postnatal diagnosis of RVOTO examined at our center. Cases were referred for evaluation of the need for fetal therapy or intervention because of TTTS, selective intrauterine growth restriction (sIUGR) or multiple congenital malformations in one of the twins. Ultrasound data were retrieved from our monochorionic twin database. Among liveborn TTTS recipients treated prenatally with laser therapy, those with RVOTO were compared with those without RVOTO (controls). We describe four additional cases with RVOTO that were not TTTS recipients. RESULTS: A total of 485 twin pregnancies received laser therapy for TTTS during the study period. RVOTO was diagnosed in 3% (11/368) of liveborn TTTS recipients, of whom two showed mild Ebstein's anomaly. Before laser therapy, pericardial effusion was seen in 45% (5/11) of RVOTO cases (P < 0.01) and abnormal A-wave in the ductus venosus (DV) in 73% (8/11) (P = 0.03), significantly higher proportions than in controls. Mean gestational age at laser therapy was 17 + 3 weeks in RVOTO cases compared with 20 + 3 weeks in controls (P = 0.03). A prediction model for RVOTO was constructed incorporating these three significant variables. One TTTS donor had RVOTO after the development of transient hydrops following laser therapy. Three larger twins in pregnancies complicated by sIUGR developed RVOTO, the onset of which was detectable early in the second trimester. CONCLUSIONS: RVOTO occurs in TTTS recipient twins but can also develop in TTTS donors and larger twins of pregnancies complicated by sIUGR. Abnormal flow in the DV, pericardial effusion and early gestational age at onset of TTTS are predictors of RVOTO in TTTS recipients, which suggests increased vulnerability to hemodynamic imbalances in the fetal heart in early pregnancy. These findings could guide diagnostic follow-up protocols after TTTS treatment. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Improved xylose uptake in Saccharomyces cerevisiae due to directed evolution of galactose permease Gal2 for sugar co-consumption.

AIMS: Saccharomyces cerevisiae does not express any xylose-specific transporters. To enhance the xylose uptake of S. cerevisiae, directed evolution of the Gal2 transporter was performed. METHODS AND RESULTS: Three rounds of error-prone PCR were used to generate mutants with improved xylose-transport characteristics. After developing a fast and reliable high-throughput screening assay based on flow cytometry, eight mutants were obtained showing an improved uptake of xylose compared to wild-type Gal2 out of 41 200 single yeast cells. Gal2 variant 2·1 harbouring five amino acid substitutions showed an increased affinity towards xylose with a faster overall sugar metabolism of glucose and xylose. Another Gal2 variant 3·1 carrying an additional amino acid substitution revealed an impaired growth on glucose but not on xylose. CONCLUSIONS: Random mutagenesis of the S. cerevisiae Gal2 led to an increased xylose uptake capacity and decreased glucose affinity, allowing improved co-consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: Random mutagenesis is a powerful tool to evolve sugar transporters like Gal2 towards co-consumption of new substrates. Using a high-throughput screening system based on flow-through cytometry, various mutants were identified with improved xylose-transport characteristics. The Gal2 variants in this work are a promising starting point for further engineering to improve xylose uptake from mixed sugars in biomass.

A comparative study of the homogeneous enzyme immunoassay (EMIT) and two radioimmunoassays (RIA's) for digoxin.

Our experience with the determination of digoxin in plasma or serum using a homogeneous enzyme immunoassay technique (EMIT) is reported. The day-to-day precision of the EMIT digoxin assay was investigated with different series of calibrators. Coefficients of variation varied from 10 to 25 percent in the range of 0.65--7.0 ng digoxin/ml. The accuracy was established by determining the mean recovery (96 percen) of spiked serum samples (0.0--6.0 ng digoxin/ml). The cross reactivity of structure related compounds: digitoxin, spironolactone (Aldactone) and prednisone were investigated. Amniotic fluid, umbilical cord serum and serum of pregnant patients were examined for false positive reaction. Serum samples of 111 patients from two hospitals, who were treated with digoxin, were analysed by EMIT and 3H-radioimmunoassay (RIA); 38 of these samples were also determined by 125I-RIA. A good correlation was found between EMIT assay and these techniques (r =0.90 and 0.91, respectively).

Identification of genes responsible for improved cryoresistance in fermenting yeast cells.

Using repetitive freezing and thawing, different mutant industrial Saccharomyces cerevisiae strains with increased freeze resistance have been isolated. To get a better insight in the mechanisms responsible for this elevated resistance and to give us the opportunity to modify other strains so that they become more suitable for use in frozen dough preparations, we applied the microarray technology in order to identify genes that are differentially expressed in a freeze-resistant mutant when compared to a freeze-sensitive industrial yeast strain.

Characterization of a new set of mutants deficient in fermentation-induced loss of stress resistance for use in frozen dough applications.

In frozen dough applications a prefermentation period during the preparation of the dough is unavoidable and might also be important to obtain bread with a good texture. A major disadvantage of the prefermentation period is that it is associated with a rapid loss of the freeze resistance of the yeast cells. A major goal for the development of new baker's yeast strains for use in frozen dough applications is the availability of strains that maintain a better freeze resistance during the prefermentation period. We have isolated mutants that retain a better stress resistance during the initiation of fermentation. Some of these showed the same growth rate and fermentation capacity as the wild type cells. These mutants are called 'fil', for deficient infermentation induced loss of stress resistance. First we used laboratory strains and heat stress treatment, given shortly after the initiation of fermentation, as the selection protocol. The first two mutants isolated in this way were affected in the glucose-activation mechanism of the Ras-cAMP pathway. The fil1 mutant had a partially inactivating point mutation in CYR1, the gene encoding adenylate cyclase, while fil2 contained a nonsense mutation in GPR1. GPR1 encodes a member of the G-protein coupled receptor family which acts as a putative glucose receptor for activation of the Ras-cAMP pathway. In a next step we isolated fil mutants directly in industrial strains using repetitive freeze treatment of doughs as selection protocol. Surviving yeast strains were tested individually for maintenance of fermentation capacity after freeze treatment in laboratory conditions and also for the best performing strains in frozen doughs prepared with yeast cultivated on a pilot scale. The most promising mutant, AT25, displayed under all conditions a better maintenance of gassing power during freeze-storage. It was not affected in other commercially important properties and will now be characterised extensively at the biochemical and molecular level.

[Diagnosis of dermatomycoses using the sellotape-KOH method]. / Diagnostiek van dermatomycosen door middel van de sellotape-KOH-methode.

In a group of 84 adult male workers in an industrial plant, who used a common shower room, the applicability of the adhesive tape-KOH technique for routine mycologic examination was investigated. The tape technique was compared with the conventional cover slip technique in interdigital and plantar lesions. The tape technique gave more frequent positive results than the cover slip technique (74% and 57% respectively). However, examination of the tapes was more difficult than that of the cover slips. The latter method therefore appears more appropriate for routine microscopical mycologic examination.

Fetal cardiac contractility before and after intrauterine transfusion.

OBJECTIVE: To evaluate the effect of fetal anemia and intrauterine transfusion on ventricular shortening fraction. METHODS: The end-diastolic and end-systolic transverse dimensions of the left and right ventricles were obtained using M-mode ultrasonography. The shortening fractions of both ventricles were calculated at three time points: before, immediately after and one day after intrauterine transfusion. The blood volume given at intrauterine transfusion was expressed as a percentage of estimated fetoplacental blood volume. RESULTS: Complete measurements were obtained from 49 transfusions in 23 fetuses. Intrauterine transfusion was performed at a median gestational age of 31 (range, 19-35) weeks. Median hemoglobin concentration before and after intrauterine transfusion was 7.9 (range, 2.7-13.7) g/dL and 14.3 (range, 12.7-16.1) g/dL, respectively. Both left and right ventricular shortening fractions differed significantly between the three time points. Left ventricular shortening fraction decreased immediately after transfusion in 43 (88%) of the 49 procedures. Right ventricular shortening fraction decreased immediately after transfusion in 42 (86%) of the 49 procedures. At the first intrauterine transfusion, there was only a weak correlation between the decrease in shortening fraction of both ventricles and the transfused volume (left: R(2) = 0.15; P = 0.20/right: R(2) = 0.005; P = 0.81). CONCLUSION: Transfusion significantly decreases the shortening fraction of both ventricles of the fetal heart. There is, however, little correlation between the decrease in shortening fraction and the volume of red cells given at intrauterine transfusion. Published by John Wiley & Sons, Ltd.

Review: the dominant flocculation genes of Saccharomyces cerevisiae constitute a new subtelomeric gene family.

The quality of brewing strains is, in large part, determined by their flocculation properties. By classical genetics, several dominant, semidominant and recessive flocculation genes have been recognized. Recent results of experiments to localize the flocculation genes FLO5 and FLO8, combined with the in silicio analysis of the available sequence data of the yeast genome, have revealed that the flocculation genes belong to a family which comprises at least four genes and three pseudogenes. All members of this gene family are located near the end of chromosomes, just like the SUC, MEL and MAL genes, which are also important for good quality baking or brewing strains. Transcription of the flocculation genes is repressed by several regulatory genes. In addition, a number of genes have been found which cause cell aggregation upon disruption or overexpression in an as yet unknown manner. In total, 33 genes have been reported that are involved in flocculation or cell aggregation.

Physical localization of the flocculation gene FLO1 on chromosome I of Saccharomyces cerevisiae.

The genetics of flocculation in the yeast Saccharomyces cerevisiae are poorly understood despite the importance of this property for strains used in industry. To be able to study the regulation of flocculation in yeast, one of the genes involved, FLO1, has been partially cloned. The identity of the gene was confirmed by the non-flocculent phenotype of cells in which the C-terminal part of the gene had been replaced by the URA3 gene. Southern blots and genetic crosses showed that the URA3 gene had integrated at the expected position on chromosome I. A region of approximately 2 kb in the middle of the FLO1 gene was consistently deleted during propagation in Escherichia coli and could not be isolated. Plasmids containing the incomplete gene, however, were still able to cause weak flocculation in a non-flocculent strain. The 3' end of the FLO1 gene was localized at approximately 24 kb from the right end of chromosome I, 20 kb centromere-proximal to PHO11. Most of the newly isolated chromosome I sequences also hybridized to chromosome VIII DNA, thus extending the homology between the right end of chromosome I and chromosome VIII to approximately 28 kb.

Transcriptional regulation of flocculation genes in Saccharomyces cerevisiae.

Northern analysis showed that DNA from the flocculation gene FLO1 hybridized to mRNA molecules of 4.8 kb. This transcript was specific for the FLO1 gene at the right end of chromosome I since disruption of this gene resulted in the disappearance of the transcript. We further found an absolute correlation between flocculation and the presence of transcripts hybridizing to FLO1 DNA, both in various flocculent and non-flocculent strains and in cells from the non-flocculating and flocculating stages of growth. In all cases transcripts were present in flocculating and absent from non-flocculating cultures. From these results we conclude that the FLO1 gene is transcriptionally regulated. Mutations in TUP1 or SSN6 cause flocculation. Several transcripts hybridizing to FLO1 DNA were present in the mutants but not in the corresponding wild-type strains. Disruption of the FLO1 gene in the tup1 and ssn6 strains showed that one of the transcripts corresponded to the FLO1 gene. Disruption of FLO1 did not abolish flocculation completely but only reduced it, indicating that at least two flocculation genes, including FLO1, are activated or derepressed by mutations in the TUP1/SSN6 regulatory cascade.

Localization of the dominant flocculation genes FLO5 and FLO8 of Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae three dominant flocculation genes, FLO1, FLO5 and FLO8 have been described. Until now only the FLO1 gene, which is located at chromosome I, has been cloned and sequenced. FLO5 and FLO8 were previously localized at chromosomes I and VIII respectively (Vezinhet, F., Blondin, B. and Barre, P. (1991). Mapping of the FLO5 gene of Saccharomyces cerevisiae by transfer of a chromosome during cytoduction. Biotechnol. Lett. 13, 47-52; Yamashita, I. and Fukui, S. (1983). Mating signals control expression of both starch fermentation genes and a novel flocculation gene FLO8 in the yeast Saccharomyces. Agric. Biol. Chem. 47, 2889-2896). This was not in agreement with our results. Here, we report the location of FLO5 and FLO8 on chromosomes VIII and I respectively. By induced chromosome loss and genetic mapping, the FLO5 gene was localized at the right end of chromosome VIII approximately 34 cM centromere distal of PET3. This is part of the region that is present both at chromosome I and chromosome VIII. The location of FLO5 in this area of chromosome VIII made it necessary to re-evaluate the localization of FLO8, which was previously thought to occur in this region. Both genetic and physical mapping showed that FLO8 is allelic to FLO1. Hence, there are only two known dominant flocculation genes, FLO1 and FLO5. Analysis of the nucleotide sequence of chromosome VIII of a non-flocculent strain revealed an open reading frame encoding a putative protein that is approximately 96% identical to the Flo1 protein. This suggests that both dominant flocculation genes encode similar, cell wall-associated, proteins with the same function in the flocculation mechanism.

A comparative study of the electrode systems of three pH and blood gas apparatus.

We present a comparative evaluation of the electrode systems of three modern blood gas analysers: IL-413, ABL-1 and AVL-937C. The response curves, accuracy and precision of the pH-, pCO2- and pO2-electrodes were established with tonometered blood and buffer solutions. pH values (range 6.8-7.8) measured on the AVL deviate (-0.03 pH for blood and +0.03 pH for buffer) from those of BMS2 Mk2; whereas on the IL and ABL analysers the pH values deviate by not more than 0.01 pH. The standard deviation was better than 0.005 pH. pCO2 values of blood and buffer (range 14-106 mm Hg) deviate from the calculated tonometer values by quantities ranging from 3 to 10 mm Hg. The average precision (CV)1) of the pCO2 measurement on each analyser was better than 1.8%. pO2 values of blood (range 0-130 mm Hg) did not differ by more than 3 mm Hg from the calculated values. Above 130 mm Hg a linear negative increasing difference was seen. For buffer solutions a linear relationship between pO2 difference and pO2 value was found over the whole range from zero up to 642 mm Hg: a positive difference below and a negative difference above the pO2 of the previous calibration; if the calibration pO2 is higher, the sample pO2 is shifted to a higher value. The average precision of the pO2 measurements was better than 3%. In the (patho)-physiological range the three instruments may provide suitable results for the clinician. Suggestions are made for standardization and improvement of the electrode systems.

RNA polymerase induces DNA bending at yeast mitochondrial promoters.

Yeast mitochondrial RNA polymerase can bind specifically to promoter-containing DNA fragments in vitro as detected by DNAse I or methidiumpropyl-EDTA. Fe(II) protection assays and gel retardation experiments. Retardation of RNA polymerase-DNA complexes was most pronounced when the promoter was located in the middle of a DNA fragment and was diminished when RNA polymerase was bound near one of the ends. This indicates that upon RNA polymerase-binding the DNA undergoes a conformational change which is most likely a bend. The degree of introduced bending correlated with the efficiency of transcription and promoter-binding in a series of promoter mutants, suggesting that bending is a functional event during promoter utilisation.

Sequence of the open reading frame of the FLO1 gene from Saccharomyces cerevisiae.

The cloned part of the flocculation gene FLO1 of Saccharomyces cerevisiae (Teunissen, A.W.R.H., van den Berg, J.A. and Steensma, H.Y. (1993). Physical localization of the flocculation gene FLO1 on chromosome I of Saccharomyces cerevisiae, Yeast, in press) has been sequenced. The sequence contains a large open reading frame of 2685 bp. The amino acid sequence of the putative protein reveals a serine- and threonine-rich C-terminus (46%), the presence of repeated sequences and a possible secretion signal at the N-terminus. Although the sequence is not complete (we assume the missing fragment consists of repeat units), these data strongly suggest that the protein is located in the cell wall, and thus may be directly involved in the flocculation process.

A Saccharomyces cerevisiae G-protein coupled receptor, Gpr1, is specifically required for glucose activation of the cAMP pathway during the transition to growth on glucose.

In the yeast Saccharomyces cerevisiae the accumulation of cAMP is controlled by an elaborate pathway. Only two triggers of the Ras adenylate cyclase pathway are known. Intracellular acidification induces a Ras-mediated long-lasting cAMP increase. Addition of glucose to cells grown on a non-fermentable carbon source or to stationary-phase cells triggers a transient burst in the intracellular cAMP level. This glucose-induced cAMP signal is dependent on the G alpha-protein Gpa2. We show that the G-protein coupled receptor (GPCR) Gpr1 interacts with Gpa2 and is required for stimulation of cAMP synthesis by glucose. Gpr1 displays sequence homology to GPCRs of higher organisms. The absence of Gpr1 is rescued by the constitutively activated Gpa2Val-132 allele. In addition, we isolated a mutant allele of GPR1, named fil2, in a screen for mutants deficient in glucose-induced loss of heat resistance, which is consistent with its lack of glucose-induced cAMP activation. Apparently, Gpr1 together with Gpa2 constitute a glucose-sensing system for activation of the cAMP pathway. Deletion of Gpr1 and/or Gpa2 affected cAPK-controlled features (levels of trehalose, glycogen, heat resistance, expression of STRE-controlled genes and ribosomal protein genes) specifically during the transition to growth on glucose. Hence, an alternative glucose-sensing system must signal glucose availability for the Sch9-dependent pathway during growth on glucose. This appears to be the first example of a GPCR system activated by a nutrient in eukaryotic cells. Hence, a subfamily of GPCRs might be involved in nutrient sensing.

Evaluation of ampouled tonometered buffer solutions as a quality-control system for pH, pCO2, and pO2 measurement.

In response to the need for an adequate quality-control system for blood-pH and blood-gas analyzers, we investigated the practical application of ampouled phosphate-bicarbonate-chloride solutions tonometered with mixtures of carbon dioxide, oxygen, and nitrogen. This system offers three discrete sets of pH, pCO2, AND PO2 values, which are consistent with normal and pathophysiologically high and low values. The stated values were based on the U.S. National Bureau of Standards scale for pH and on gas analysis for pCO2 and pO2. Influence of temperature, air contact, calibration gas, and storage was established. Internal and external quality control by means of these ampoules is presented. The system is stable, accurate, precise, and suitable for simultaneous quality control of pH, pCO2, and pO2 measurements.