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At least 955 records · Page 53Linked to original sources
PubMed1975

Nitrogen exchange across the lungs in resting man.

The relationship between the partial pressure of N2 in the inspired air (PIN2), and the nitrogen transfer across the lungs (VN2), has been examined in 8 resting subjects, and a study made of the effect of diet upon this relationship. Alterations in PIN2, over the range 60 mm Hg below, to 20 mm Hg above ambient PIN2, caused changes in VN2 which could be described by a linear equation. These changes agreed both in magnitude and direction with those predicted by a four-compartment electrical analogue of the body N2 stores. They were not affected by the protein content of a meal taken 3/4 hr before the start of measurements of VN2. The study has shown that any imbalance in N2 transfer across the lungs is very small and that the open-circuit method of measuring O2 consumption is valid.

Adult↗
PubMed1987

An electronic processor for use with a whole body plethysmograph to determine specific airways conductance.

The panting manoeuvre traces produced by a whole body plethysmograph during the measurement of specific airways conductance (sGaw) are traditionally analysed by hand. Since this technique is tedious and time consuming it is prone to error, as well as suffering from considerable inter-observer variability. We describe a new inexpensive analogue electronic processor which rapidly produces readouts of sGaw and overcomes many of the problems associated with hand analysis. The system takes as its inputs the mouth flow and plethysmograph volume outputs from a pressure-corrected flow-displacement whole body plethysmograph, but it could be adapted for use with other types of plethysmograph. Since the processor is intended mainly for use during serial measurements of sGaw it does not carry out an unnecessary correction for flowmeter resistance. Using an electronic simulator of sGaw signals the output of the processor was found to be linear to better than 2% of full scale and to be insensitive to drift on the volume signal. The system has been comprehensively evaluated using signals from both normal subjects and patients. The processor output was found to agree well with the results of hand analysis, an agreement which was comparable with that obtained from computer based systems. For the normal subjects the equal value line adequately described the relationship between the processor and hand estimates of sGaw. However, for patients the slope of the best fit line was 18% less than unity but the correlation coefficient was high: 0.95. Reproducibility was found to be better than 3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1988

Analogue computer system for the evaluation of hip joint moments during normal walking.

Hip joint moments were determined by analogue computer techniques, using as inputs the angles formed by body segments during normal walking. The control algorithm was based on the division of the walking cycle into six stages; each activated by contact of heel, mid-foot and fore-foot. The problem of the accuracy of double differentiation was overcome by means of two filters which amplify the gain at the basic frequency of the walking cycle, while reducing it above 10 Hz. The analogue model gave reasonable results, suggesting that it could be used as an input to a real time microcomputer-based adaptive control system for the maintenance of hip joint balance in an amputee during walking.

Computer Simulation↗
PubMed2005

The relationship between object files and conscious perception.

Object files (OFs) are hypothesized mid-level representations which mediate our conscious perception of persisting objects-e.g. telling us 'which went where'. Despite the appeal of the OF framework, not previous research has directly explored whether OFs do indeed correspond to conscious percepts. Here we present at least one case wherein conscious percepts of 'which went where' in dynamic ambiguous displays diverge from the analogous correspondence computed by the OF system. Observers viewed a 'bouncing/streaming' display in which two identical objects moved such that they could have either bounced off or streamed past each other. We measured two dependent variables: (1) an explicit report of perceived bouncing or streaming; and (2) an implicit 'object-specific preview benefit' (OSPB), wherein a 'preview' of information on a specific object speeds the recognition of that information at a later point when it appears again on the same object (compared to when it reappears on a different object), beyond display-wide priming. When the displays were manipulated such that observers had a strong bias to perceive streaming (on over 95% of the trials), there was nevertheless a strong OSPB in the opposite direction-such that the object files appeared to have 'bounced' even though the percept 'streamed'. Given that OSPBs have been taken as a hallmark of the operation of object files, the five experiments reported here suggest that in at least some specialized (and perhaps ecologically invalid) cases, conscious percepts of 'which went where' in dynamic ambiguous displays can diverge from the mapping computed by the object-file system.

Attention↗
PubMed2004

Remifentanil used to supplement propofol does not improve quality of sedation during spontaneous respiration.

STUDY OBJECTIVE: To evaluate whether the use of remifentanil to supplement propofol during spontaneous respiration confers any benefits in terms of quality of sedation and recovery, or in terms of reduction in propofol requirements. DESIGN: Prospective, randomized, double-blind study. SETTING: University hospital. PATIENTS: 50 ambulatory adult ASA physical status I and II patients scheduled for total colonoscopy. INTERVENTIONS: Patients were randomized to receive either propofol alone or propofol plus remifentanil 0.1 microg/kg/min, while independently maintaining spontaneous respiration. MEASUREMENTS: Cardiovascular and respiratory variables were measured before induction and at 1-minute intervals thereafter. Recovery from anesthesia was assessed using simple verbal commands and the Steward Post Recovery Score. Patient satisfaction was measured with a visual analog scale. Computer simulation was used to calculate the effect-site concentrations of propofol and remifentanil. MAIN RESULTS: The depressant effects on blood pressure and respiratory function were significantly higher when propofol and remifentanil were combined. Although the addition of remifentanil resulted in a decrease of propofol usage, recovery of anesthesia was faster and patient satisfaction was higher when using propofol alone. CONCLUSIONS: The addition of remifentanil to propofol during spontaneous ventilation offered no benefits compared with the use of propofol alone.

Adjuvants, Anesthesia↗
PubMed1977

A monitor for the continuous assessment of left ventricular performance after open-heart operations.

A cardiac monitoring system has been developed that incorporated phasic aortic blood flow measurement by an extractable electromagnetic flow probe and high-fidelity arterial blood pressure recordings. Cardiac output, stroke volume, and peak aortic blood flow are measured continuously; using logarithmic amplifiers, the pressure-flow derivatives of left ventricular function, such as cardiac power and stroke work, are obtained beat by beat. This monitor is used to follow the postoperative course of patients undergoing cardiac operations and to evaluate the hemodynamic effect of therapeutic agents.

Cardiac Surgical Procedures↗