J. P. Viale

Spontaneous Cardiac Baroreflex in Humans Comparison With Drug-Induced Responses

We compared two methods of assessment of baroreflex sensitivity in eight supine healthy volunteers during repeated baseline measurements and various conditions of cardiac autonomic blockade. The spontaneous baroreflex method involved computer scanning of recordings of continuous finger arterial pressure and electrocardiogram to locate sequences of three or more beats in which pressure spontaneously increased or decreased, with parallel changes in pulse intervals. The mean regression slope of all these sequences during each study condition was considered to represent the mean spontaneous baroreflex slope. In the drug-induced method, sigmoidal curves were constructed from data obtained by bolus injections of phenylephrine and nitroprusside; the tangents taken at the resting pressure of each of these curves were compared with the mean spontaneous baroreflex slopes. The two methods yielded slopes that were highly correlated (r = .96, P < .001), with significant but similar intraindividual baseline variability. Atropine virtually eliminated the baroreflex slope; subsequent addition of propranolol did not alter it further. Propranolol or clonidine alone increased average baroreflex slope to the extent that they increased resting pulse interval (r = .69 to .83). The spontaneous baroreflex method provides a reliable, noninvasive assessment of human vagal cardiac baroreflex sensitivity within its physiological operating range.

Clinical validation of the Deltatrac monitoring system in mechanically ventilated patients

AbstractObjectiveTo evaluate a monitor of pulmonary gas exchange (Deltatrac, Datex) in a clinical setting.DesignAfter in vitro evaluation, comparison over 2 min between

Sympathovagal effects of spinal anesthesia assessed by the spontaneous cardiac baroreflex

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Added inspiratory work of breathing during CPAP ventilation: comparison of two demand-valve devices with a continuous flow-system

and

The effects of norepinephrine infusion on oxygen consumption in a patient with septic shock

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Additional Inspiratory Work in Intubated Patients Breathing with Continuous Positive Airway Pressure Systems

values measured by the Deltatrac and the Douglas bag technique. Comparisons were also achieved over 8 h periods between the Deltatrac and a system using a mass-spectrometer.SettingPolyvalent intensive care unit (ICU 15 beds) in a 1200 bed general hospital.PatientsComparison with the Douglas bag technique in 10 patients undergoing controlled ventilation. Comparison with the massspectrometer system in 25 other patients undergoing controlled or pressure support ventilation.Measurements and resultsCompared to the results obtained by the Douglas bag technique, the bias (±2SD) for