Computed tomography in adult respiratory distress syndrome: what has it taught us?

Pelosi, Paolo; Crotti, Stefania; Brazzi, Luca; Gattinoni, Luciano

doi:10.1183/09031936.96.09051055

Cited by 117 publications

(55 citation statements)

References 34 publications

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“…In the early stages of ARDS there is a small number of working lung units, sometimes as little as 25% of normal (referred to some authors as "baby lung"), which receive all the adjusted tidal volume (V T ), resulting in high ventilation pressures (8). These high ventilation pressures, achieved with conventional V T (e.g., 10 to 12 ml/kg), have been related to pulmonary injury in different experimental models (9,10).…”

Section: Introductionmentioning

confidence: 99%

Ventilation with high tidal volume induces inflammatory lung injury

Bueno

Santos

et al. 2002

Braz J Med Biol Res

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Mechanical ventilation with high tidal volumes (V T ) has been shown to induce lung injury. We examined the hypothesis that this procedure induces lung injury with inflammatory features. Anesthetized male Wistar rats were randomized into three groups: group 1 (N = 12): V T = 7 ml/kg, respiratory rate (RR) = 50 breaths/min; group 2 (N = 10): V T = 21 ml/kg, RR = 16 breaths/min; group 3 (N = 11): V T = 42 ml/kg, RR = 8 breaths/min. The animals were ventilated with fraction of inspired oxygen of 1 and positive end-expiratory pressure of 2 cmH 2 O. After 4 h of ventilation, group 3, compared to groups 1 and 2, had lower PaO 2 [280 (range 73-458) vs 517 (range 307-596), and 547 mmHg (range 330-662), respectively, P<0.05], higher wet lung weight [3.62 ± 0.91 vs 1.69 ± 0.48 and 1.44 ± 0.20 g, respectively, P<0.05], and higher wet lung weight/dry lung weight ratio [18.14 (range 11.55-26.31) vs 7.80 (range 4.79-12.18), and 6.34 (range 5.92-7.04), respectively, P<0.05]. Total cell and neutrophil counts were higher in group 3 compared to groups 1 and 2 (P<0.05), as were baseline TNF-α concentrations [134 (range <10-386) vs 16 (range <10-24), and 17 pg/ml (range <10-23), respectively, P<0.05]. Serum TNF-α concentrations reached a higher level in group 3, but without statistical significance. These results suggest that mechanical ventilation with high V T induces lung injury with inflammatory characteristics. This ventilatory strategy can affect the release of TNF-α in the lungs and can reach the systemic circulation, a finding that may have relevance for the development of a systemic inflammatory response.

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Section: Introductionmentioning

confidence: 99%

Ventilation with high tidal volume induces inflammatory lung injury

Bueno

Santos

et al. 2002

Braz J Med Biol Res

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“…ARDS affects adversely the mechanical properties of the respiratory system with reduced compliance and, to a lesser extent, increased resistance as hallmarks [3,4]. The syndrome is characterized by heterogeneous lung involvement, with relatively well preserved areas and severely diseased areas [5]. This heterogeneous involvement may affect the pattern of lung emptying during passive expiration.…”

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confidence: 99%

Lung emptying in patients with acute respiratory distress syndrome: effects of positive end-expiratory pressure

Kondili¹,

Prinianakis²,

Athanasakis³

et al. 2002

Eur Respir J

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The pattern of lung emptying was studied in 10 mechanically-ventilated patients with acute respiratory distress syndrome.At four levels of positive end-expiratory pressure (PEEP) (0, 5, 10 and 15 cmH 2 O) tracheal (Ptr) and airway pressures (Paw), flow (V9) and volume (V) were continuously recorded. Tidal volume was set between 0.5-0.6 L and V9/V curves during passive expiration were obtained. Expired volume was divided into five equal volume slices and the time constant (te) and effective deflation compliance (Crs eff ) of each slice was calculated by regression analysis of V/V9 and postocclusion V/Ptr relationships, respectively. In each slice, the presence or absence of flow limitation was examined by comparing V9/V curves with and without decreasing Paw. For a given slice, total expiratory resistance (Rtot) (consisting of the respiratory system (Rrs), endotracheal tube (Rtube) and ventilator circuit (Rvent)) was calculated as the te/Crs eff ratio. In the absence of flow limitation Rrs was obtained by subtracting Rtube and Rvent from Rtot, while in the presence of flow limitation Rrs equaled Rtot. The te of the pure respiratory system (ters) was calculated as the product of Rrs and Crs eff .At zero PEEP, ters increased significantly towards the end of expiration (52¡31%) due to a significant increase in Rrs (46¡36%). Application of PEEP significantly decreased Rrs at the end of expiration and resulted in a faster and relatively constant rate of lung emptying.In conclusion, without positive end-expiratory pressure the respiratory system in patients with acute respiratory distress syndrome deflates with a rate that progressively decreases, due to a considerable increase in expiratory resistance at low lung volumes. Application of positive end-expiratory pressure decreases the expiratory resistance, probably by preventing airway closure, and as a result modifies the pattern of lung emptying.

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“…Essa densidade é, provavelmente, devida à coleção de líquidos nos alvéolos e no interstício. O peso aumentado dos pulmões na SARA promove uma distribuição desigual da infiltração de líquidos, sujeita à ação da gravidade no aumento do gradiente (vertical) da pressão transpulmonar, resultando em uma área pulmonar dependente colapsada (porções posteriores quando em decúbito dorsal) 8,24 .…”

Section: Discussionunclassified

“…Nesta eventualidade não deveriam existir outros fatores que pudessem trazer algum impacto positivo na oxigenação destes pacientes em tão pouco tempo. Através de estudos tomográficos de tórax, sabe-se que, em poucos minutos após a mudança de posição supina para a prona, a densidade desloca-se da região dorsal para a ventral, que coincide com melhora da oxigenação (da antiga região dependente para a nova região dependente) 7,8,11 .…”

Section: Discussionunclassified

“…A paralisia e a sedação, comumente utilizadas em pacientes com SARA, poderão aumentar a pressão pleural e as atelectasias na região dorsal do pulmão 6,7 . A TC de tórax, ao contrário do raio X de tórax, no paciente com SARA e em prona, mostra uma rápida redistribuição da opacidade pulmonar da região dorsal para a ventral [8][9][10] , com a melhora da oxigenação devido à redução da fração do shunt (diminui a mistura sangüínea) e com o aumento do número de unidades V/Q próximas ao normal, obtidas através do recrutamento de áreas não ventiladas, mas perfundidas, no dorso do pulmão 6,11 .…”

Section: Short-term Effects Of Prone Positioning On the Oxygenation Ounclassified

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Efeito a curto prazo da posição prona na oxigenação de crianças em ventilação mecânica

Bruno¹,

Piva²,

García³

et al. 2001

J. Pediatr. (Rio J.)

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Objective: to analyze the short-term effects of prone positioning on the oxygenation of mechanically-ventilated children suffering from severe hypoxemia.Materials and Methods: a prospective, nonrandomized trial (each patient as his/her own control) was conducted between July 1998 and July 1999. Mechanically-ventilated children with peak inspiratory pressure (PIP) greater than or equal to 30 cm H 2 O, FiO 2 greater than or equal to 0.5, and PaO 2 /FiO 2 ratio less than or equal to 200 were included in the study. Each patient was kept in the prone position for two hours, returning to the supine position after this period. Oxygenation was assessed by means of PaO 2 /FiO 2 in the supine position (one hour before prone positioning), one hour after prone positioning, and one hour after returning to the supine position. Patients who presented an increase of at least 20 in PaO 2 /FiO 2 were considered responsive. The results were compared by Student t-test, Friedman test, chi-square test, Fisher's exact test, and confidence interval (CI).Results: eighteen children (10 males), whose mean age was 11.5 +11.5 months, with initial PaO 2 /FiO 2 of 96.06 + 41.78, participated in the study. After one hour in the prone position, 27.7% of the patients (5/18) improved their PaO 2 /FiO 2 ratio (P=0.045). Six of these patients presented reduced lung compliance (four of them had acute respiratory distress syndrome); and twelve patients showed increased airway resistance (six of them presented bronchiolitis). No significant difference was observed between these two groups (reduced lung compliance x increased airway resistance) in terms of age, sex, duration of ventilation prior to change in position, peak inspiratory pressure, FiO 2 , severity of hypoxemia, and outcome.Conclusion: prone positioning during mechanical ventilation of children with severe hypoxemia may improve the PaO 2 /FiO 2 ratio in the first hour.J Pediatr (Rio J) 2001; 77 (5): 361-8: pronation, oxygenation, acute respiratory distress syndrome, pediatric intensive care unit, children, artificial respiration. ResumoObjetivos: analisar o efeito a curto prazo da posição prona na oxigenação de pacientes pediátricos com hipoxemia severa e submetidos a ventilação mecânica.Material e Métodos: ensaio clínico prospectivo, não randomizado, sendo cada paciente o seu próprio controle, realizado no período de julho de 1998 a julho de 1999. Incluídas todas as crianças com diagnóstico de insuficiência respiratória aguda, em ventilação mecânica, com pressão inspiratória positiva (PIP) > 30cm H 2 O e fração de oxigênio inspirada (FiO 2 ) > 0,5, que apresentassem paO 2 / FiO 2 < 200. Os pacientes foram mantidos duas horas na posição prona, retornando, a seguir, à posição supina. Avaliou-se a oxigenação, através da paO 2 /FiO 2 , na posição supina (1 hora antes da mudança de posição), com 1 hora de posição prona e 1 hora após retornar à posição supina. Considerou-se responsivo todo o paciente que apresentasse um aumento de, no mínimo, 20 na paO 2 /FiO 2 . Os resultados foram com...

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Computed tomography in adult respiratory distress syndrome: what has it taught us?

Cited by 117 publications

References 34 publications

Ventilation with high tidal volume induces inflammatory lung injury

Ventilation with high tidal volume induces inflammatory lung injury

Lung emptying in patients with acute respiratory distress syndrome: effects of positive end-expiratory pressure

Efeito a curto prazo da posição prona na oxigenação de crianças em ventilação mecânica

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