1. Maximum acceleration of blood has been measured in the aorta using a catheter tip velocity transducer in twelve patients undergoing diagnostic coronary angiography. Signals were obtained with the catheter tip transducer 5–6 cm above the aortic valve. From these signals, the values for peak velocity were measured, and acceleration was derived by continuous differentiation of the velocity signal. 2. The values obtained for maximum acceleration and peak velocity were inversely related to the severity of coronary artery disease as indicated by coronary angiography. 3. There was a close relationship between peak velocity, maximum acceleration and ejection fraction calculated from the left-ventricular angiogram. 4. Three patients with chest pain and no cardiac abnormality detectable by cardiac catheterization had maximum acceleration values above 1500 cm/s 2 and peak velocity above 60 cm/s. 5. Four patients with definite coronary artery disease had normal intracardiac pressures and cardiac indices, but decreased ejection fractions. The values for maximum acceleration were between 750 and 1100 cm/s 2 and for peak velocity between 32.0 and 58.0 cm/s. 6. Five patients had severe coronary disease with abnormal intracardiac pressures, cardiac indices and decreased ejection fraction. Values for maximum accelerations were below 850 cm/s 2 and for peak velocity, below 41.0 cm/s.
1. Block of the phrenic nerves in three normal subjects, produced by injection of lignocaine in the neck, caused alleviation of the thoracic sensation during breath holding and prolonged breath-holding time. 2. Injection of lignocaine in the neck without nerve block had no effect on breath holding sensation or breath-holding time. 3. A patient with a spinal-cord transection at the third cervical segment with paralysed diaphragm and chest wall, had no sensation in the chest or abdomen during breath holding. 4. This patient maintained normal ventilation by using hypertrophied sternomastoid muscles. During breath holding he experienced no sensation in the neck despite the presence of sternomastoid contraction. 5. There is previous evidence that complete muscular paralysis abolishes breath-holding sensation but that paralysis of all muscles innervated from spinal segments below the eighth cervical has no effect.
1. Resistive loads were added to the airways of patients with tracheostomies; the patients were blindfolded and the loads introduced without their knowledge. 2. The ability to detect the loads was the same in a patient with C3 transection (chest wall and diaphragm disconnected from the brain) as in a control group of patients with no neurological lesion. 3. It is concluded that receptors in the chest wall and diaphragm are not involved in the genesis of the sensation by which added resistive loads are detected.