American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Oct 1996
Mechanism of short-term improvement in lung function after emphysema resection.
We prospectively investigated the mechanism of airflow limitation before and after targeted emphysematous resection in 12 consecutively studied adult patients 68 +/- 4 yr of age (mean +/- SD) with very severe COPD undergoing bilateral thoracoscopic stapling techniques. Lung function, static lung elastic recoil, and airway conductance was measured 2 wk before and 5 to 6 mo after surgery. After surgery, there was a significant (p < 0.01) reduction in TLC (9.3 +/- 0.3 [mean +/- SEM] to 7.7 +/- 0.4 L), functional residual capacity, and residual volume. ⋯ Analysis of maximal expiratory flow-static elastic recoil pressure curve indicated that conductance of the S segment (Gs) increased from 0.20 +/- 0.03 (mean +/- SEM) to 0.27 +/- 0.03 L/s/cm H20 (p < 0.01), and the critical transmural pressure (Ptm') decreased from 3.1 +/- 0.2 to 2.4 +/- 0.2 cm H20 (p < 0.02). Mean airway conductance increased from 0.14 to 0.22 L/s/cm H20 (p < 0.01). The improvement in maximal expiratory airflow can be primarily attributed to increased lung elastic recoil and its secondary effect on enlarging airway diameter causing increased airway conductance, increased Gs, and decreased Ptm'.
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Am. J. Respir. Crit. Care Med. · Oct 1996
Microcirculatory changes in rat skeletal muscle in sepsis.
The aim of this study was to confirm that microvascular perfusion was abnormal during the early phases of normotensive sepsis and to determine whether these changes were due to the development of tissue edema. Skeletal muscle red blood cell (RBC) flow was studied in rats made septic by cecal ligation and perforation (CLP). After anesthesia with halothane, arterial and venous cannulae were inserted and, in the treatment group, a CLP performed. ⋯ This study shows that sepsis was associated with increased RBC flow heterogeneity. These changes, which occur within 24 h of the septic insult, are a persistent feature of the evolving septic process in the absence of tissue edema. These observations support the view that extrinsic compression of the microcirculation by tissue edema is not the primary cause of alterations in microcirculatory flow in sepsis.
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Am. J. Respir. Crit. Care Med. · Oct 1996
Chest wall compliance in infants and children with neuromuscular disease.
Respiratory muscle weakness is the primary cause of respiratory dysfunction in neuromuscular disease (NMD), but structural abnormalities of the chest wall also play a role. In adults with NMD, restrictive lung disease is in part caused by reduced chest wall compliance (C(W)), believed to reflect stiffening of connective tissue resulting from chronically reduced chest wall motion in the presence of respiratory muscle weakness. We hypothesized that chronic limitation of chest wall motion in young children with NMD leads to structural underdevelopment of the chest wall, and results in increased, rather than decreased, C(W). ⋯ C(W)/kg was higher in subjects with NMD than in controls, at 5.2 +/- 2.8 (mean +/- SD) versus 2.4 +/- 0.8 ml/cm H2O (p < 0.001). In subjects who had normal lung compliance values during spontaneous breathing (C(Lspont)), C(W)/C(Lspont) was significantly greater in subjects with NMD (5.5 +/- 3.2) than in controls (1.9 +/- 1.0) (p < 0.001). By predisposing to rib cage deformation and reduced end-expiratory lung volume, abnormally high C(W) in infants and young children with NMD may contribute to respiratory dysfunction.