Citations

Pneumotachographs (also called pneumotachometers and anemometers) measure airflow against a fixed resistance and may be found in respirometers, mechanical ventilators, incentive breathing devices, diagnostic spirometers, and other pulmonary function testing instruments. The Fleisch design is the oldest, but it requires a costly pressure transducer and analog-to-digital converter and its accuracy is affected by gas-viscosity differences and by airflow turbulence. Besides the Fleisch, ceramic, screen, orifice, hot-wire, turbine, vortex, and ultrasonic pneumotachographs are now available. They solve some of the Fleisch's problems but cannot be used in all applications. All instruments with these devices must be carefully and completely calibrated at the time of installation and routinely calibrated or checked thereafter.

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Three patients with different neurologic diseases—amyotrophic lateral sclerosis, poliomyelitis, and idiopathic bilateral diaphragm paralysis—and with chronic ventilatory failure were successfully ventilated with negative pressure. This noninvasive ventilatory technique uses a chest cuirass and provides an alternative to tracheostomy and positive-pressure ventilation. As a result of the benefits that these three patients received, we conclude that the cuirass remains an acceptable method of ventilation for some patients with chronic neurologic disease.

Abstract Spontaneous coronary artery dissection is an unusual, but increasingly recognized, cause of acute coronary syndrome. It is a potentially fatal disorder that predominantly (>90% of cases) affects women, who are about 20 years younger (age 45–52 years) than those presenting with an acute coronary syndrome due to atherosclerotic coronary artery disease, and is the commonest cause of myocardial infarction associated with pregnancy. With the advent of improved coronary artery imaging modalities, including invasive coronary angiography, intravascular ultrasonography (IVUS), and optical coherence tomography (OCT), spontaneous coronary artery dissection is being increasingly diagnosed. It is typically due to a spontaneous bleed in the tunica media of an epicardial coronary artery, with or without an intimal tear, that results in an intramural haematoma; the latter, in turn causing a separation or dissection of the lamellae formed by the layers of smooth muscle cells of the tunica media, which can propagate longitudinally. Although coronary artery dissection can be due to atherosclerotic disease that may, in fact, present spontaneously, or to trauma, or guidewire-induced intimal injury, the understanding that the entity now known as spontaneous coronary artery dissection is an idiopathic disorder that is not associated with atherosclerosis or trauma, and is not iatrogenic, is one that has emerged only relatively recently (last 10–15 years). This raises the question, what is the provenance of spontaneous coronary artery dissection as it is now defined and understood? Here, this issue is addressed by a detailed consideration of the medical literature from 1800.