Jan Zandbergen

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.

Attenuation of carbon dioxide‐induced panic after clonazepam treatment

Ten patients meeting the DSM‐III‐R criteria for panic disorder were treated with clonazepam. Prior to clonazepam treatment and after a 5‐week treatment period, patients underwent a 35% carbon dioxide challenge procedure. Following clonazepam treatment, a significant reduction in carbon dioxide vulnerability was observed.

Breath-holding in Panic Disorder

In earlier studies, it was found that exogenous carbon dioxide administration provoked high anxiety in panic disorder (PD) patients, whereas healthy normals and patients suffering from other anxiety disorders were hardly affected. Breath-holding provides a simple method to induce endogenous CO2 accumulation. Fourteen PD patients, 14 patients suffering from other anxiety disorders, and 14 healthy controls were asked to hold their breath as long as possible. Apnea times appeared to be longer in the normal control group than in the other two groups. Using a one-tailed t test, a trend for a difference was found between the PD subjects and other anxiety patients, the PD patients having slightly lower values. No differences were found with respect to increase in anxiety during breath-holding or the ratio of apnea times before and after hyperventilation.

Ventilatory response to CO2 in panic disorder

The Read rebreathing technique was used to measure the ventilatory response to inhalation of carbon dioxide in 15 panic disorder patients, 15 obsessive-compulsive disorder patients, and 15 healthy control subjects. No significant differences in ventilatory response were found among the three groups. The tidal volume and frequency components of the ventilatory response also did not differ among the groups. The hypothetical pCO2 value corresponding with zero ventilation was significantly lower in the panic disorder patients than in normal control subjects.

No chronic hyperventilation in panic disorder patients

Arterial blood gases were measured and base excess calculated in 18 nonpanicking panic disorder (PD) patients, 12 subjects suffering from other anxiety disorders, and 18 normal control subjects. There was neither chronic nor clinically significant acute hyperventilation in either group.

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.

An analysis of panic symptoms during hypercarbia compared to hypocarbia in patients with panic attacks

Twenty panic disorder patients underwent a 35% CO2 challenge test and a hyperventilation provocation test. CO2-induced anxiety proved to correlate significantly with respiratory symptoms. These symptoms appeared to be considerably more severe during CO2 inhalation than during the hyperventilation provocation test, which induced no significant anxiety.

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.