Pulsatile flow

About: Pulsatile flow is a research topic. Over the lifetime, 6278 publications have been published within this topic receiving 149638 citations.

Pulsatile gas flow in bronchi caused by the heart beat.

Abstract: Pulsatile gas flow in lobar and segmental bronchi synchronous with the heart beat has been measured during routine diagnostic bronchoscopy, using a new type of flowmeter. Pulsations were detected in three-quarters of the 60 patients examined, and occurred in all parts of the lung though they were more marked on the left side. They were seen both during inspiration and expiration, but were most obvious in the postexpiratory pauses. At a given instant in the cardiac cycle, the phase of the pulsations was sometimes different in different parts of the lung, gas going into some lobes and coming out of others. Volume flow rates up to 2.5 liter/min and displaced volumes up to 5 ml were recorded. The pulsatile flow is probably caused by changes in volume of the beating heart, and by its movements within the chest so that some parts of the lung are compressed while others expand. Because of their size and frequency, the pulsations promote mixing of the anatomical dead-space gas with alveolar gas. Submitted on Octo...

Blood flow in pulmonary veins: II. The influence of events transmitted from the right and left sides of the heart.

Abstract: The wave form of blood flow in the large extra parenchymal pulmonary veins has an inverse relationship to the pressure wave form in the left atrium during each cardiac cycle. However, when vein flow from the lungs is separated from the left atrium by diverting it into a constant pressure reservoir, its wave form then resembles a lung capillary flow pulse, though delayed from it in time and reduced in amplitude. The pulsatility of flow in pulmonary veins separated from the left atrium is further reduced when transcapillary pressure is elevated by lung inflation. However, in the intact state, the relation between the pattern of pulmonary vein flow and left atrial pressure remains unaffected by lung inflation. It is postulated that the thin walled extraparenchymal pulmonary veins together behave as a collapsible reservoir which enables outflow from them to be determined by changes in left atrial pressure, in spite of variations of pulsatile flow into them from the lungs.

Pulsatile drug delivery system

Abstract: Pulsatile drug delivery system is the most interesting time- and site-specific system. This system is designed for chronopharmacotherapy which is based on circadian rhythm. The principle rationale for the use of pulsatile release is for the drugs where a constant drug release, i.e., a zero-order release is not desired. Pulsatile drug delivery system is defined as the rapid and transient release of certain amount of molecules within a short time period immediately after a predetermined off-release period, i.e., lag time. Various systems like capsular systems, osmotic systems, pulsatile system based on the use of soluble or erodible polymer coating, use of rupturable membranes and pulsatile system based on membrane permeability are summarized in this article.These systems are beneficial for the drugs having chronopharmacological behavior where night time dosing is required and for the drugs having high first-pass effect and having specific site of absorption in gastrointestinal tract.

Umbilical blood flow patterns directly after birth before delayed cord clamping

Abstract: Background Delayed umbilical cord clamping (DCC) affects the cardiopulmonary transition and blood volume in neonates immediately after birth. However, little is known of blood flow in the umbilical vessels immediately after birth during DCC. The objective is to describe the duration and patterns of blood flow through the umbilical vessels during DCC. Methods Arterial and venous umbilical blood flow was measured during DCC using Doppler ultrasound in uncomplicated term vaginal deliveries. Immediately after birth, the probe was placed in the middle of the umbilical cord, pattern and duration of flow in vein and arteries were evaluated until cord clamping. Results Thirty infants were studied. Venous flow: In 10% no flow was present, in 57% flow stopped at 4:34 (3:03–7:31) (median (IQR) min:sec) after birth, before the cord was clamped. In 33%, flow continued until cord clamping at 5:13 (2:56–9:15) min:sec. Initially, venous flow was intermittent, increasing markedly during large breaths or stopping and reversing during crying, but then became continuous. Arterial flow: In 17% no flow was present, in 40% flow stopped at 4:22 (2:29– 7:17) min:sec, while cord pulsations were still palpable. In 43% flow continued until the cord was clamped at 5:16 (3:32–10:10) min:sec. Arterial flow was pulsatile, unidirectional towards placenta or bidirectional to/from placenta. In 40% flow became continuous towards placenta later on. Conclusions During delayed umbilical cord clamping, venous and arterial umbilical flow occurs for longer than previously described. Net placental transfusion is probably the result of several factors of which breathing could play a major role. Umbilical flow is unrelated to cessation of pulsations.