Journal of clinical monitoring
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Flow through an endotracheal tube (ETT) causes a pressure loss across the tube. This loss results in a difference between pressure measured at the airway and pressure measured in the trachea. This difference can lead to errors when calculating pulmonary mechanics and when setting ventilators. We have tested a method of estimating tracheal pressure from the pressure in the ETT cuff. ⋯ The cuff estimation technique gives real-time, continuous, noninvasive tracheal pressure measurements in intubated animals with cuffed ETTs.
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Comparative Study
A new system to record reliable pulse oximetry data from the Nellcor N-200 and its applications in studies of variability in infant oxygenation.
We have developed a simple system for internal validation of oximetry data collected over many hours from the Nellcor N-200 pulse oximeter (Nellcor, Inc., Hayward, CA). This system uses signals from the oximeter alone and a validation algorithm that is based in a computer connected to the oximeter. Unlike other validation systems, this system does not require connections to other monitors. ⋯ While variability in infant SpO2 is a well-known phenomenon, the amount seen here was unexpected. For example, the range of true saturations frequently recorded was quite wide at a reported mean SpO2 of 90% (from 81 to 94%; but, the range was only from 92 to 98% at a mean SpO2 of 96%). These findings demonstrate the usefulness of the new system and, if substantiated in more detailed studies, have important implications for the use of pulse oximeters to assess oxygenation in newborns.
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Two commercially available complete anesthetic simulators were studied in the United States. Although there are some differences between the two systems, each consists of an adult manikin allowing some direct anesthetic interventions, a system of producing physiologic signals to any commercial monitoring system, and the ability to interface with an anesthetic machine and ventilator. In addition, both simulators model the responses to a variety of drugs used by anesthetists. ⋯ Now available are combined systems using manikins controlled by computer, with interfaces to anesthetic machines, ventilators, and monitoring equipment. Two systems are commercially available in the United States. In this report, we briefly describe their technical specifications and how we saw them being used.
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The mechanical properties of the respiratory system (i.e., elastance and resistance) depend on the frequency, tidal volume, and shape of the flow waveform used for forcing. We developed a system to facilitate accurate measurements of elastance and resistance in laboratory and clinical settings at the frequencies and tidal volumes in the physiologic range of breathing. ⋯ Accurate, standardized measurements of lung and chest wall properties can be obtained in many settings with relative ease with the system described. These properties, and their frequency and tidal volume dependences in the physiologic range, provide important information to aid in the understanding of changes in respiratory function caused by day-to-day conditions, clinical intervention and pathologies.