Marvin A. Sackner

The lifeShirt. An advanced system for ambulatory measurement of respiratory and cardiac function.

An accurate ambulatory breathing monitor is needed to observe acute respiratory changes in patients with medical or psychological disorders outside the clinic (e.g., hyperventilation during panic or apneas during sleep). Significant limitations of existing monitors are size, troublesome operation, and difficulty holding chest and abdomen bands in place during 24-hour recordings. Recently, a garment has been developed with embedded inductive plethysmography sensors for continuous ambulatory monitoring of respiration, heart activity, inductive cardiography, motility, postural changes, and other functions. The signals are displayed and stored on a handheld computer (Visor), and then analyzed offline, extracting more than 40 clinical parameters relating to cardiorespiratory function (e.g., heart rate, respiratory sinus arrhythmia, tidal volume, stroke volume, pre-ejection period, apnea-hypopnea index, thoraco-abdominal coordination, sighing). The device also serves as an electronic diary of symptoms, moods, and activities. This advanced system may open a new era in ambulatory monitoring for clinical practice and scientific research.

Effect of Mouthpiece Breathing on Cardiorespiratory Response to Intense Exercise

Use of mouthpiece and noseclips after breathing pattern at rest and during moderate exercise. Our purpose was to extend observations on mouthpiece breathing to its effects on the cardiorespiratory response to intense exercise and to develop and validate an algorithm for computer-assisted analysis of breathing pattern recorded with respiratory inductive plethysmography. Six normal men performed incremental bicycle exercise to volitional exhaustion on two occasions with and without mouthpiece and noseclip. ECG and breathing pattern recorded with a respiratory inductive plethysmograph were analyzed manually and with computer assistance. Mouthpiece breathing increased tidal volume and respiratory cycle time by up to 63 and 33% respectively (p < 0.02) during mild exercise, but it did not alter performance, heart rate, or breathing pattern at maximal exercise. Mean differences between inductive plethysmographic and spirometric tidal volumes were < 5% during validation at rest and maximal exercise. Application of the proposed algorithm for semiautomatic breathing pattern analysis provided significant time savings with no loss in precision compared with manual analysis. In conclusion, in normal men, performance and breathing pattern during maximal exercise are not altered by a mouthpiece and noseclip, and accurate computer-assisted measurement of ventilation from external transducers may be performed even during intense exercise.

Thoracocardiography: Noninvasive monitoring of left ventricular stroke volume☆

PURPOSE Thoracocardiography noninvasively monitors global stroke volume by inductive plethysmographic recording of ventricular volume curves as previously validated by thermodilution. Our purpose was to investigate the potential of thoracocardiography to individually assess stroke volume of the left ventricle. We hypothesized that curves predominantly reflecting left ventricular volume could be obtained by recording waveforms from thoracocardiographic transducers placed at various levels around the chest, and by identifying their origin as the left ventricle if mean expiratory exceeded mean inspiratory stroke volumes during spontaneous breathing. MATERIALS AND METHODS Stroke volumes obtained by thoracocardiography in normal subjects were compared beat by beat with estimates derived from simultaneous measurements of left ventricular cavity stroke area by echocardiography with automatic boundary detection. Changes in respiratory variations of stroke volumes were analyzed during spontaneous breathing at fixed rate and tidal volume, during mechanical ventilation, and resistive loaded breathing. RESULTS In 170 comparisons of beat-by-beat stroke volumes, 89% of thoracocardiographic fell within +/-20% of echocardiographic estimates. Changes in tidal volume, resistive loaded breathing, and mechanical ventilation induced respiratory variations of thoracocardiographic derived stroke volumes consistent with the known effect of respiratory changes in intrapleural pressure on left ventricular stroke volumes. CONCLUSIONS The results suggest that thoracocardiography noninvasively tracks changes in left ventricular stroke volumes. Their absolute value may also be monitored if an initial calibration by an independent technique, such as echocardiography, is performed.

Inductance cardiography (thoracocardiography): A novel, noninvasive technique for monitoring left ventricular filling☆

PURPOSE Thoracocardiography noninvasively records left ventricular volume curves by an inductive plethysmographic transducer transversely encircling the chest near the xiphoid process. Amplitudes of thoracocardiographic curves track stroke volume as previously validated by thermodilution. We investigated whether thoracocardiographic curves reflect left ventricular filling. MATERIALS AND METHODS We studied nine men in horizontal and 30 degrees head-up position during tidal breathing and Valsalva maneuvers. The ratio of peak slope of left ventricular volume curves during early rapid filling relative to that during atrial contraction (E/A ratio) and isovolumic relaxation time (interval from aortic component of second heart sound to early rapid filling onset) were measured with thoracocardiography and compared with Doppler-echocardiographic-derived indices of transmitral flow velocity. RESULTS Isovolumic relaxation times estimated by the two methods agreed closely (bias = -2 ms, limits of agreement = -28 to +24 ms, 75 comparisons). E/A ratios by thoracocardiography and Doppler echocardiography were significantly correlated (R = 0.53, n = 75, P<.001), but individual values differed. Both methods provided identical trends of changes in E/A ratios with interventions in 50 of 66 (76%) comparisons. CONCLUSIONS Thoracocardiography reflects characteristics of left ventricular filling similar to Doppler echocardiography. Because it does not require hand-holding a transducer, thoracocardiography has the potential for continuous monitoring of mechanical cardiac performance.

Biological basis of neuroprotection and neurotherapeutic effects of Whole Body Periodic Acceleration (pGz).

Exercise is a well known neuroprotective and neurotherapeutic strategy in animal models and humans with brain injury and cognitive dysfunction. In part, exercise induced beneficial effects relate to endothelial derived nitric oxide (eNO) production and induction of the neurotrophins; Brain Derived Neurotrophic Factor (BDNF) and Glial Derived Neurotrophic Factor (GDNF). Whole Body Periodic Acceleration (WBPA (pGz), is the motion of the supine body headward to footward in a sinusoidal fashion, at frequencies of 100-160 cycles/min, inducing pulsatile shear stress to the vascular endothelium. WBPA (pGz) increases eNO in the cardiovascular system in animal models and humans. We hypothesized that WBPA (pGz) has neuroprotective and neurotherapeutic effects due to enhancement of biological pathways that include eNOS, BDNF and GDNF. We discuss protein expression analysis of these in brain of rodents. Animal and observational human data affirm a neuroprotective and neurotherapeutic role for WBPA (pGz). These findings suggest that WBPA (pGz) in addition to its well known beneficial cardiovascular effects can be a simple non-invasive neuroprotective and neurotherapeutic strategy with far reaching health benefits.