This investigation tests the hypothesis that the normal cerebral image obtained non-invasively during continuous inhalation of C15O2 is related to cerebral blood flow. Trace amounts of CO2 labeled with the positron-emitting radionuclide 15O were administered to 4 normal subjects at normo- and hypocapnia and to 2 of these subjects at hypercapnia. Hypocapnia typically caused a marked decrease in ...

Panic disorder is characterized by the paroxysmal occurrence and fear of bodily symptoms. In recent years it has been proposed that patients "learn" to fear cardiorespiratory sensations through interoceptive conditioning. This study sought to model the initial stage of this process in healthy volunteers (N=44) using mild cardiac sensations. An additional aim was to explore whether anxiety sensi...

The perioperative course of 41 patients undergoing 85 endoscopic laser resections of central airway lesions under general anaesthesia was reviewed. The CO2 laser was used in 60 procedures and the Nd:YAG in 25. Intravenous anaesthesia and Venturi ventilation were utilized for 65 resections; 20 procedures involved predominantly inhalation anaesthesia via the ventilating bronchoscope. Significant ...

BACKGROUND We have previously reported that 35% CO2 challenge induced myocardial ischemia in 81% of coronary artery disease (CAD) patients with comorbid panic disorder (PD) and previous positive nuclear exercise stress tests. However, it is yet unclear whether this is the case among CAD patients with PD and normal nuclear exercise stress test results. We hypothesized that a potent mental stress...

We examined the effect of hypoxia and hypercapnia administered during deliberately induced periodic breathing (PB) in seven lambs following posthyperventilation apnea. Based on our theoretical analysis, the sensitivity or loop gain (LG) of the respiratory control system of the lamb is directly proportional to the difference between alveolar PO2 and inspired PO2. This analysis indicates that dur...

Transcranial Doppler ultrasound (TCD) allows measurement of blood flow velocities in the intracranial vessels, and can be used to assess cerebral vasodilator responses to a hypercapnic stimulus. The reliability of this technique has not been established, nor is there agreement about whether the technique should be performed in sitting or lying postures. We tested the intra- and inter-rater reli...

Numerous studies have confirmed the role of endogenous carbon monoxide (CO) gas as a signal transmitter. However, CO is considered an intracellular transmitter, as no studies have demonstrated the redistribution of CO from the blood to tissue cells. Tracer analyses of 13CO2 production following 13CO gas inhalation demonstrated that CO is oxidized to carbon dioxide (CO2) in the body and that CO ...

Distribution of cerebral blood flow was measured with an array of 200 ultra-pure germanium radiation detectors and 133-Xe by inhalation. The array "sees" the head as a composite of different subvolumes and enables measurement of the concentration history of tracer every 1-10 sec in each subvolume simultaneously. Subvolume mean flows, (fm), and partition coefficients, lambda m, are derived by co...