Regional distribution of gas and tissue in acute respiratory distress syndrome. I. Consequences for lung morphology. CT Scan ARDS Study Group.

OBJECTIVE: To compare the computed tomographic (CT) analysis of the distribution of gas and tissue in the lungs of patients with ARDS with that in healthy volunteers. DESIGN: Prospective study over a 53-month period. SETTING: Fourteen-bed surgical intensive care unit of a university hospital. PATIENTS AND PARTICIPANTS: Seventy-one consecutive patients with early ARDS and 11 healthy volunteers. MEASUREMENTS AND RESULTS: A lung CT was performed at end-expiration in patients with ARDS (at zero PEEP) and healthy volunteers. In patients with ARDS, end-expiratory lung volume (gas + tissue) and functional residual capacity (FRC) were reduced by 17% and 58% respectively, and an excess lung tissue of 701+/-321 ml was observed. The loss of gas was more pronounced in the lower than in the upper lobes. The lower lobes of 27% of the patients were characterized by "compression atelectasis," defined as a massive loss of aeration with no concomitant excess in lung tissue, and "inflammatory atelectasis," defined as a massive loss of aeration associated with an excess lung tissue, was observed in 73% of the patients. Three groups of patients were differentiated according to the appearance of their CT: 23% had diffuse attenuations evenly distributed in the two lungs, 36% had lobar attenuations predominating in the lower lobes, and 41% had patchy attenuations unevenly distributed in the two lungs. The three groups were similar regarding excess lung tissue in the upper and lower lobes and reduction in FRC in the lower lobes. In contrast, the FRC of the upper lobes was markedly lower in patients with diffuse or patchy attenuations than in healthy volunteers or patients with lobar attenuations. CONCLUSIONS: These results demonstrate that striking differences in lung morphology, corresponding to different distributions of gas within the lungs, are observed in patients whose respiratory condition fulfills the definition criteria of ARDS.

Regional distribution of gas and tissue in acute respiratory distress syndrome. III. Consequences for the effects of positive end-expiratory pressure. CT Scan ARDS Study Group. Adult Respiratory Distress Syndrome.

OBJECTIVE: To determine whether differences in lung morphology assessed by computed tomography (CT) affect the response to positive end-expiratory pressure (PEEP). DESIGN: Prospective study over a 53-month period. SETTING: Fourteen-bed surgical intensive care unit of a university hospital. PATIENTS AND PARTICIPANTS: Seventy-one consecutive patients with early adult respiratory distress syndrome (ARDS). MEASUREMENTS AND RESULTS: Fast spiral thoracic CT was performed at zero end-expiratory pressure (ZEEP) and after implementation of PEEP 10 cmH2O. Hemodynamic and respiratory parameters were measured in both conditions. PEEP-induced overdistension and alveolar recruitment were quantified by specifically designed software (Lungview). Overdistension occurred only in the upper lobes and was significantly correlated with the volume of lung, characterized by a CT attenuation ranging between -900 and -800 HU in ZEEP conditions. Cardiorespiratory effects of PEEP were similar in patients with primary and secondary ARDS. PEEP-induced alveolar recruitment of the lower lobes was significantly correlated with their lung volume (gas + tissue) at functional residual capacity. PEEP-induced alveolar recruitment was greater in the lower lobes with "inflammatory atelectasis" than in the lower lobes with "mechanical atelectasis." Lung morphology as assessed by CT markedly influenced the effects of PEEP: in patients with diffuse CT attenuations PEEP induced a marked alveolar recruitment without overdistension, whereas in patients with lobar CT attenuations PEEP induced a mild alveolar recruitment associated with overdistension of previously aerated lung areas. These results can be explained by the uneven distribution of regional compliance characterizing patients with lobar CT attenuations (compliant upper lobes and stiff lower lobes) contrasting with a more even distribution of regional compliances observed in patients with diffuse CT attenuations. CONCLUSIONS: In patients with ARDS, the cardiorespiratory effects of PEEP are affected by lung morphology rather than by the cause of the lung injury (primary versus secondary ARDS). The regional distribution of the loss of aeration and the type of atelectasis -- "mechanical" with a massive loss of lung volume, or "inflammatory" with a preservation of lung volume-- characterizing the lower lobes are the main determinants of the cardiorespiratory effects of PEEP.

A lung computed tomographic assessment of positive end-expiratory pressure-induced lung overdistension.

The aim of this study was to assess positive end-expiratory pressure (PEEP)-induced lung overdistension and alveolar recruitment in six patients with acute lung injury (ALI) using a computed tomographic (CT) scan method. Lung overdistension was first determined in six healthy volunteers in whom CT sections were obtained at FRC and at TLC with a positive airway pressure of 30 cm H2O. In patients, lung volumes were quantified by the analysis of the frequency distribution of CT numbers on the entire lung at zero end-expiratory pressure (ZEEP) and PEEP. In healthy volunteers at FRC, the distribution of the density histograms was monophasic with a peak at -791 +/- 12 Hounsfield units (HU). The lowest CT number observed was -912 HU. At TLC, lung volume increased by 79 +/- 35% and the peak CT number decreased to -886 +/- 26 HU. More than 70% of the increase in lung volume was located below -900 HU, suggesting that this value can be considered as the threshold separating normal aeration from overdistension. In patients with ALI, at ZEEP the distribution of density histograms was either monophasic (n = 3) or biphasic (n = 3). The mean CT number was -319 +/- 34 HU. At PEEP 13 +/- 3 cm H2O, lung volume increased by 47 +/- 19% whereas mean CT number decreased to -538 +/- 171 HU. PEEP induced a mean alveolar recruitment of 320 +/- 160 ml and a mean lung overdistension of 238 +/- 320 ml. In conclusion, overdistended lung parenchyma of healthy volunteers is characterized by a CT number below -900 HU. This threshold can be used in patients with ALI for differentiating PEEP-induced alveolar recruitment from lung overdistension.

A manobra de Brandt & Daroff modificada na reabilitaçäo da vertigem postural / Modified Brandt & Daroff maneuver in postural vertigo rehabilitation

A vertigem é um dos sintomas mais freqüentes na otoneurologia clínica. Acomete mais de 33 por cento das pessoas em alguma época de sua vida, aflige 47 por cento dos homens e 61 por cento das mulheres com mais de 70 anos de idade. A vertigem em determinadas posições da cabeça e do corpo ou as mudanças de posições é muito comum, e ocorre diante de uma excitação anormal do labirinto.As características mais comuns dos pacientes vertiginosos são: insegurança, limitações nas atividades da vida diária, tendência ao isolamento social e ansiedade. A reabilitação vestibular é necessária para reintegrar o indivíduo ao ambiente, restabelecendo sua autoconfiança, por meio de exercícios que facilitem a compensação vestibular. Os tratamentos podem ser realizados por meio da reabilitação vestibular, medicamentos e cirurgia. No presente estudo, 22 pacientes com queixa vestibular de vertigem postural foram submetidos à avaliação otorrinolaringológica, audiométrica e vestibular, e posteriormente encaminhados para um programa de reabilitação vestibular no Setor de Equilibriometria da Disciplina de Otoneurologia da UNIFESP-EPM. Todos os pacientes foram orientados quanto aos hábitos e dietas alimentares, exercícios posturais (Manobra de Brandt & Daroff modificada) para serem realizados diariamente em casa, e comparecimento ao setor após 30 dias para reavaliação. Observou-se melhora sintomatológica relevante em mais de 80 por cento dos pacientes, tendo sido possível concluir que esta manobra foi eficaz no tratamento da vertigem postural.