An analytical model has been developed for the pressure waveform radiated underwater when an offshore steel pipe pile is struck by a hammer. The model is based on the coupled equations of motion for axial and radial vibration of a thin shell and yields frequency-dependent phase velocity and attenuation of these vibrations. A harmonic solution is obtained for the radiated sound pressure, using J...

Because of the high noise levels radiated by military jet aircraft, it has been hypothesized that nonlinearity influences the propagation of the noise. A numerical model, which accounts for second-order cumulative nonlinearity, atmospheric absorption and dispersion, and geometrical spreading, has been developed to propagate jet noise waveforms. Numerical propagation of recorded waveforms from r...

International standards for calculating heart period variability (HPV) from a series of R-wave intervals (R-R) in an electrocardiographic (ECG) recording have been widely accepted. It is possible, and potentially useful in various settings, to use systolic blood pressure waveform intervals to estimate HPV, but the validity of HPV derived from blood pressure (BP) waveforms has not been establish...

The purpose of this study is to measure blood velocities in carotid, brachial and femoral arteries with synchronized measurement of electrocardiogram (ECG) during head-up tilt (HUT) using a developed telemetry measurement system. The velocity waveforms and ECG are continuously measured in six putatively healthy young subjects for 130 s during supine and 90 degrees HUT. From the measured peak sy...

Pressure support ventilation (PSV) is a commonly used mode. It is patient-triggered, pressure-limited, and (normally) flow-cycled. Triggering difficulty occurring during PSV is usually due to intrinsic positive end-expiratory pressure. The airway pressure generated at the initiation of inhalation is determined by the pressure support setting and the pressure rise time (pressurization rate) sett...

Haemodynamic monitoring may potentially lead to improved quality of care in haemodynamic compromised patients. However, the usefulness of invasive techniques using the pulmonary artery catheter is questioned. Noninvasive techniques which provide data on haemodynamics might provide a good alternative. New techniques have been developed in recent years to monitor cardiac output and other paramete...

BACKGROUND Respiratory-induced arterial and plethysmographic (pulse oximetry) waveform changes were shown to be good predictors of cardiac output response to increased preload. The aim of this study was to evaluate the reliability of arterial and plethysmographic waveform variables in patients with mild hypovolemia. METHODS Patients undergoing autologous hemodilution were studied. After anest...