Synchronous Ventilation Research Articles

MR "microscopy" of the rat thorax.

High resolution images can be obtained from anywhere in the body of small animals with magnetic resonance combined with cardiac gating and scan synchronous ventilation. We used these methods to examine the intrathoracic anatomy of the rat. Anesthetized rats were intubated and ventilated in synchrony with imaging acquisition. Images were obtained in a 1 m bore, 1.5 T system fitted with a 28 cm diameter high field gradient coil and a 5 cm radio-frequency coil. We used cardiac gated, three-dimensional spin warp acquisitions. Eight contiguous slices (2.5 mm thick) were obtained simultaneously. In addition to visualizing major vessels and cardiac chambers, cardiac valves and papillary muscles were clearly demonstrated. Major pulmonary vessels and peripheral parenchyma were also seen. These results demonstrate MR "microscopy" can be used to image all major cardiopulmonary structures in the rat with respect to selected times of the cardiac cycle. This capability for noninvasive "microscopy" opens new avenues for cardiopulmonary research using well characterized rodent models.

A ventilator for magnetic resonance imaging.

Breathing motion severely degrades the quality of magnetic resonance images (MRI) of the thorax and upper abdomen and interferes with the acquisition of quantitative data. To minimize these motion effects, we built an MRI compatible ventilator for use in animal studies. Solid state circuitry is used for controlling ventilation parameters. The ventilator can be triggered internally at frequencies of 0.1 to 30 Hz or it can be triggered externally such as by the MRI pulse sequence. When triggered by the scanner, ventilation is synchronized to occur between image data acquisitions. Thus, image data are obtained when there is no breathing motion and at a minimum lung volume when hydrogen density is maximum. Since the ventilator can be adjusted to operate at virtually any frequency from conventional to high frequency, ventilation can be synchronized to all commonly used repetition times (100 ms to 2000 ms or more; 600 to 30 breaths/min). Scan synchronous ventilation eliminates breathing motion artifacts from most imaging sequences (single and multiple spin echo and inversion recovery). Best image quality is obtained when scan synchronous ventilation is combined with cardiac gating. These methods are also useful for quantitative research studies of thoracic and abdominal organs.

Synchronous and asynchronous ventilation during cardiopulmonary resuscitation

Synchronous and asynchronous ventilation during cardiopulmonary resuscitation

Intermittent Mandatory Ventilation: Is Synchronization Important?

Intermittent mandatory ventilation (IMV) allows patients to breathe spontaneously between mechanically supported breaths. Recently, several manufacturers have implied that nonsynchronous application of the mechanical breath may depress cardiovascular function and increase pulmonary barotrauma. Because it is technically difficult and expensive to synchronize mechanical ventilation to spontaneous breathing, we sought to determine whether there is any significant difference in cardiopulmonary function during synchronous and nonsynchronous mandatory ventilation. Our investigation failed to support the hypothesis that synchronization of spontaneous and mechanically mediated breathing is physiologically beneficial.

Effect of mean circulatory filling pressure and other peripheral circulatory factors on cardiac output.

I P ONE studies curves which depict the relationship of cardiac output to mean right atria1 pressure (one of the forms of Starling’s curves), it is obvious that, within the normal range of function of the heart, cardiac output can change tremendously while the right atria1 pressure changes only slightly. This fact led to the early belief that it is not the function of the heart itself which controls cardiac output but instead that cardiac output is controlled by the various factors in the peripheral circulatory system which regulate the return of blood to the heart. Though it is not entirely true that cardiac output is independent of the function of the heart (I), nevertheless, it is hoped to emphasize in the present paper the special importance of the peripheral circulatory factors which affect venous return. In order to do this, a mathematical circuit analysis of the closed circuit circulatory system has been made. This circuit analysis has been specifically simplified so that the factors derived would be amenable to experimental test. Two of the factors which have proved to be of importance, as shown both by this circuit analysis and by experimental data, are a) ‘capacitance’ and b) ‘mean circulatory filling pressure.’ As used in these studies the term capacitance means dV/dP or, in other words, the change in volume of a particular part of the circulatory system with each unit change in pressure. This term has been used in the present paper because there is at present no term in common usage in hydrodynamics which means dV/dP. This is different from the term ‘distensibility’ which is commonly used to mean dV/dP + V. The term mean circulatory filling pressure (MCFP) has been defined previously (2), and it means ,__-