Carbon Dioxide Inhalation Induces Dose-Dependent and Age-Related Negative Affectivity

BACKGROUND: Carbon dioxide inhalation is known to induce an emotion similar to spontaneous panic in Panic Disorder patients. The affective response to carbon dioxide in healthy subjects was not clearly characterized yet. METHODOLOGY/PRINCIPAL FINDINGS: Sixty-four healthy subjects underwent a double inhalation of four mixtures containing respectively 0, 9, 17.5 and 35% CO(2) in compressed air, following a double blind, cross-over, randomized design. Affective responses were assessed according to DSM IV criteria for panic, using an Electronic Visual Analogue Scale and the Panic Symptom List. It was demonstrated that carbon dioxide challenges induced a dose dependent negative affect (p<0.0001). This affect was semantically identical to the DSM IV definition of panic. Older individuals were subjectively less sensitive to Carbon Dioxide (p<0.05). CONCLUSIONS/SIGNIFICANCE: CO(2) induced affectivity may lay on a continuum with pathological panic attacks. Consistent with earlier suggestions that panic is a false biological alarm, the affective response to CO(2) may be part of a protective system triggered by suffocation and acute metabolic distress

Tradução e adaptação transcultural do Questionário de Atividade Física Habitual

BACKGROUND: There has been a growing scientific interest on the interface between exercise and psychiatric disorders. However, there is a lack of self-report instruments to assess levels of physical activity adapted to Brazilian Portuguese. OBJECTIVE: To translate, assess the semantic equivalence of the Habitual Physical Activity Questionnaire and perform a non-psychometric pre-test with subjects (n = 30) from the Brazilian population, with different educational backgrounds. METHODS: The cross-cultural adaptation process consisted of two translations and back translations performed by two independent evaluators; an evaluation of the versions and the development of a synthetic version; and a commented pretest of the questionnaire. RESULTS: For each item of the instrument, the results of the four stages are reported. Most of the participants (91%) did not present any difficulties comprehending the items of the instrument. Further studies should be addressed to determine the adequacy of using this instrument in the less-educated population. We recommend that less instructed subjects be supervised while responding the questionnaire. DISCUSSION: The use of two translations versions, their critical appraisal and the assessment of the target population conceives more safety to the process of semantic equivalence.CONTEXTO: Atualmente há na literatura um crescente interesse na interface entre exercício físico e transtornos psiquiátricos. Apesar disso, ainda há uma deficiência de instrumentos de autorrelato para medir os níveis de atividade física dos pacientes. OBJETIVO: A tradução, a aferição da equivalência semântica e uma aplicação piloto (n = 30), sem pretensão psicométrica, do Questionário de Atividade Física Habitual, visando sua utilização na população brasileira de diferentes níveis de escolaridade. MÉTODOS: O processo envolveu duas traduções e retrotraduções realizadas por avaliadores independentes, avaliação das versões seguida da elaboração de uma versão síntese e pré-teste comentado. RESULTADOS: A maioria dos participantes (91%) não apresentou dificuldades de compreensão com o questionário. Para cada item do instrumento, apresentam-se os resultados das quatro etapas. Mais estudos são necessários para determinar a adequação para populações de baixa escolaridade. Os autores recomendam que sujeitos menos instruídos sejam supervisionados ao preencher o questionário. CONCLUSÕES: A utilização de duas versões de tradução e retrotradução, a discussão sobre a versão síntese e a interlocução com a população-alvo proporcionam maior segurança ao processo de equivalência semântica

Effects of tryptophan depletion and tryptophan loading on the affective response to high-dose CO2 challenge in healthy volunteers

It has been reported that in panic disorder (PD), tryptophan depletion enhances the vulnerability to experimentally induced panic, while the administration of serotonin precursors blunts the response to challenges. Using a high-dose carbon dioxide (CO2) challenge, we aimed to investigate the effects of acute tryptophan depletion (ATD) and acute tryptophan loading (ATL) on CO2-induced panic response in healthy volunteers. Eighteen healthy volunteers participated in a randomized, double-blind placebo-controlled study. Each subject received ATD, ATL, and a balanced condition (BAL) in separate days, and a double-breath 35% CO2 inhalation 4.5 h after treatment. Tryptophan (Trp) manipulations were obtained adding 0 g (ATD), 1.21 g (BAL), and 5.15 g (ATL) of l-tryptophan to a protein mixture lacking Trp. Assessments consisted of a visual analogue scale for affect (VAAS) and panic symptom list. A separate analysis on a sample of 55 subjects with a separate-group design has also been performed to study the relationship between plasma amino acid levels and subjective response to CO2. CO2-induced subjective distress and breathlessness were significantly lower after ATD compared to BAL and ATL (p &lt;0.05). In the separate-group analysis, Delta VAAS scores were positively correlated to the ratio Trp:I LNAA pound after treatment (r = 0.39; p &lt;0.05). The present results are in line with preclinical data indicating a role for the serotonergic system in promoting the aversive respiratory sensations to hypercapnic stimuli (Richerson, Nat Rev Neurosci 5(6):449-461, 2004). The differences observed in our study, compared to previous findings in PD patients, might depend on an altered serotonergic modulatory function in patients compared to healthy subjects

35% CO2 sensitivity in social anxiety disorder

The 35% carbon dioxide (CO(2)) challenge is a well-established model of panic. This study aimed to investigate 35% CO(2) sensitivity in patients with social anxiety disorder (SAD) compared with patients with panic disorder (PD) and normal controls. First, a 35% CO(2) challenge was conducted including 16 patients with generalized SAD, 16 with PD and 16 normal subjects. Outcome was assessed by a Visual Analogue Scale for Fear (VAS-F) and the Panic Symptom List (PSL). Second, meta-analyses of fear and panic scores were performed, including data from the present experiment and from previous 35% CO(2) challenge studies in patients with SAD. The present 35% CO(2) challenge found equal increases in VAS-F and PSL in patients with SAD compared with normal controls, whereas the CO(2) response in patients with PD was significantly stronger than in controls. The meta-analyses confirmed the experimental data from this study, and in addition showed an intermediate panic rate in SAD patients, in between that of normal controls and patients with PD. In conclusion, neither our experiment nor the meta-analyses found evidence for a similarly exaggerated 35% CO(2) sensitivity in SAD and PD, suggesting that the pathogenesis of SAD is different from PD, although patients with SAD may be slightly more sensitive than non-anxious controls.status: publishe