H. Lousberg

CO2 vulnerability in panic disorder.

The immediate effects of a single inhalation of a 35% CO2 mixture in oxygen were examined in 12 patients with panic disorders and 11 normal control subjects. Compared to a placebo air inhalation, the CO2 inhalation provoked short-lived autonomic panic symptoms in both patients and normals; it also elicited high subjective anxiety in patients with panic disorders. The latter rated the overall CO2-induced state as very similar to a real-life panic attack.

Specific sensitivity of patients with panic attacks to carbon dioxide inhalation

One inhalation of 35% CO2 in oxygen was administered to 36 patients with anxiety disorders and 14 healthy controls. Eighteen patients had a diagnosis of panic disorder (PD) and 18 of obsessive-compulsive disorder (OCD). As a placebo control for CO2, compressed air was administered in a double-blind design. Immediately before and after the inhalation, levels of anxiety and DSM-III-R symptoms of panic were assessed. CO2 elicited high levels of subjective anxiety in the PD group. Patients with OCD were hardly affected by the inhalation, and did not differ from healthy controls. These results suggest that CO2 challenge should be considered as a specific probe for subjects with panic-anxiety. It is speculated that CO2 may trigger some as yet undefined mechanisms, possibly linked to ventilation control, which demarcate panic from other types of pathological anxiety.

Hypercarbia versus hypocarbia in panic disorder

In order to compare the panicogenic effects of hypercarbia and hypocarbia in panic disorder (PD), 12 PD patients and 11 healthy controls underwent a 35% CO2 challenge as well as a hyperventilation provocation test in a random cross-over design. Both anxiety and anxiety symptoms proved to be significantly higher during the 35% CO2 challenge in PD patients as compared to the response during 35% CO2 in normals and during hyperventilation in both patients and normals. The results suggest that PD patients are specifically hypersensitive to an increase in pCO2.

Carbon dioxide chemosensitivity in panic disorder.

ABSTRACT— The ventilatory response to the inhalation of carbon dioxide was studied in 19 panic patients and 14 normal controls, using the Read rebreathing technique. The panic patients showed significantly higher ventilatory response compared with normal controls.

Cognitive determinants of lactate-induced anxiety

Abstract The effects of lactate infusion on subjective mood change were studied in two differently instructed groups, in a double-blind, placebo-controlled, cross-over study. S s who were told that infusions would produce anxiety reported a significant change in the expected direction after lactate but not after glucose. S s who were told that infusions would produce a state of pleasant excitement showed no change after either infusion. The possible role of cognitive parameters in experimentally-induced anxiety is discussed.

Specificity of interoceptive fear to panic disorders

It has been argued that fear of interoceptive sensations is a maintaining factor in panic disorders. This study investigated whether interoceptive fears are specific to panic disorders or whether they are a feature of neurosis in general. Twenty-nine panic patients, 28 nonpanicking neurotic controls, and 29 normal controls were compared for their scores on a 14-item questionnaire intended to measure interoceptive fears. Indeed it was found that panic patients scored considerably higher than both control groups, whereas no significant differences emerged between the two control groups. It is concluded that interoceptive fear is diagnostically specific to panic disorders.

The role of life events in the onset of panic disorder

Twenty-five panic disorder patients and fifteen obsessive-compulsive patients are compared with regard to a number of Life Events over the last 12 months prior to onset of the disorder and additionally over the total life course up until onset of the disorder. Panic Disorder patients do not differ from obsessive-compulsive disorder patients in terms of the number of life events, they experience during the last year prior to onset of their disorder. However, over the total life course, Panic Disorder patients do seem to be exposed to more Life Events than obsessive-compulsive disorder patients. The findings are discussed in light of the existing literature.

Low doses of clonazepam in the treatment of panic disorder.

In order to assess the efficacy of a high-potency benzodiazepine in the treatment of panic disorder, an open trial was conducted with clonazepam. Clonazepam was administered in relatively low doses and, after four weeks, was shown to be effective in reducing the number of panic attacks and associated features of the disorder.

Pulmonary carbon dioxide and panic-arousing sensations after 35% carbon dioxide inhalation: hypercapnia/hyperoxia versus hypercapnia/normoxia

Experimental research has demonstrated that CO2 inhalation provides a valid laboratory model for acute panic. Earlier studies employed CO2/O2 mixtures that were not only hypercapnic but also hyperoxic, raising the question of the relative contribution of the hyperoxidity. A comparison between a hypercapnic/hyperoxic mixture (35% CO2/65% O2) and a hypercapnic/normoxic mixture (35% CO2/20% O2/45% N2) revealed no differences on self-reported panic symptoms or end tidal pCO2. It is concluded that findings from previous CO2/O2 inhalation studies should be attributed to the hypercapnic, rather than to the hyperoxic, nature of the mixtures.