PubMed · 8447592
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R Kennedy. 1993. Detecting arterial puncture while inserting central venous lines.. https://pubmed.ncbi.nlm.nih.gov/8447592/
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Correlated binary data are encountered in many areas of medical research, system reliability and quality control. For monitoring failures rates in such situations, simultaneous bivariate cumulative sum (CUSUM) charts with the addition of secondary control limits are proposed. Using an approach based on a Markov chain model, the run length properties of such a monitoring scheme can be determined for sudden, or gradual, changes in the failure rates. The proposed control charts are easy to implement, and are shown to be very effective at detecting small changes in the rate of undesirable outcomes, especially when the changes are gradual. This procedure is illustrated using bivariate outcome data arising from a series of paediatric surgeries. The methodology is sufficiently general that it may be adapted for multivariate normal, binomial or Poisson responses.
OBJECTIVE: The aim of the study was to compare the mechanical and functional properties of isolated small stem villous arteries from the placentas of women who smoked heavily (>/=15 cigarettes/d) during pregnancy with those from the placentas of nonsmokers. STUDY DESIGN: Isolated stem villous arteries were mounted in small-vessel myographs. Circumference-tension relationships were established with 124 mmol/L potassium chloride. Concentration-response curves were obtained for endothelin 1, prostaglandin F2alpha, vasoactive intestinal peptide, corticotropin-releasing hormone, sodium nitroprusside, and cadmium chloride. The effect of nitric oxide was examined with N omega-nitro-l -arginine. RESULTS: Stem villous arteries from the heavy smoking group developed a significantly lower tension than did those from nonsmokers at 6 of 9 steps of the circumference-tension experiment (P <.05). Endothelin 1 evoked a significantly greater maximum vasoconstrictive response in stem villous arteries from heavy smokers than in those from nonsmokers (P <.05). CONCLUSION: Stem villous arteries of heavy smokers have altered mechanical properties and a greater vasoconstrictive response to endothelin 1 than do those from nonsmokers. These changes may compromise fetal placental blood flow and thereby contribute to the lower birth weights seen among infants born to heavy smokers.
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