American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jul 1999
Neuropsychological sequelae and impaired health status in survivors of severe acute respiratory distress syndrome.
Acute respiratory distress syndrome (ARDS) is a disease of acute respiratory failure manifested by severe hypoxemia with a high mortality rate. Previous outcome studies of ARDS have assessed survival and/or pulmonary function as the primary outcome variables. Cognitive or psychological outcomes following ARDS have not been described, despite the possibility that ARDS patients are at risk for brain injury through hypoxemia or other mechanisms. ⋯ At 1 yr after ARDS, 17 of 55 (30%) patients still exhibited generalized cognitive decline. Forty-three of 55 (78%) patients had all or at least one of the following: impaired memory, attention, concentration and/or decreased mental processing speed. One year after ARDS a substantial portion of ARDS survivors exhibit impaired health status and cognitive sequelae which may be due to hypoxemia, emboli, inflammation, drug toxicity, and/or other etiologies.
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Am. J. Respir. Crit. Care Med. · Jul 1999
Antibacterial components in bronchoalveolar lavage fluid from healthy individuals and sarcoidosis patients.
Antibacterial peptides and proteins are an integral part of the epithelial defense barrier that provides immediate protection against bacterial invasion. In humans, alpha-defensins are mainly bactericidal effectors in circulating granulocytes, beta-defensin-1 is synthesized in epithelial cells, and LL-37 is produced in granulocytes but is also induced in skin epithelia during inflammation. To investigate the importance of these defense effectors in disease, we analyzed bronchoalveolar lavage fluid (BALF) for bactericidal activity. ⋯ In addition, the antibacterial peptide LL-37 was located in alveolar macrophages, bronchial epithelial cells, and bronchial glands, suggesting that it has a defensive role in airway mucosa. In conclusion, the airway epithelium is protected by a complex antibacterial defense system. This is activated in sarcoidosis, and may explain why these patients seldom develop severe respiratory tract infections.
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Am. J. Respir. Crit. Care Med. · Jul 1999
Comparative StudyExpiratory washout versus optimization of mechanical ventilation during permissive hypercapnia in patients with severe acute respiratory distress syndrome.
The aim of this study was to compare three ventilatory techniques for reducing PaCO2 in patients with severe acute respiratory distress syndrome treated with permissive hypercapnia: (1) expiratory washout alone at a flow of 15 L/min, (2) optimized mechanical ventilation defined as an increase in the respiratory frequency to the maximal rate possible without development of intrinsic positive end- expiratory pressure (PEEP) combined with a reduction of the instrumental dead space, and (3) the combination of both methods. Tidal volume was set according to the pressure-volume curve in order to obtain an inspiratory plateau airway pressure equal to the upper inflection point minus 2 cm H2O after setting the PEEP at 2 cm H2O above the lower inflection point and was kept constant throughout the study. The three modalities were compared at the same inspiratory plateau airway pressure through an adjustment of the extrinsic PEEP. ⋯ Extrinsic PEEP had to be reduced by 5.3 +/- 2.1 cm H2O during expiratory washout and by 7.3 +/- 1.3 cm H2O during the combination of the two modes, whereas it remained unchanged during optimized mechanical ventilation alone. In conclusion, increasing respiratory rate and reducing instrumental dead space during conventional mechanical ventilation is as efficient as expiratory washout to reduce PaCO2 in patients with severe ARDS and permissive hypercapnia. When used in combination, both techniques have additive effects and result in PaCO2 levels close to normal values.
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Am. J. Respir. Crit. Care Med. · Jul 1999
Progressive mechanical ventilatory constraints with aging.
To investigate the progressive nature of mechanical ventilatory constraints with aging, we studied 20 young (age 39 +/- 3 yr), 14 senior (70 +/- 2 yr), and 11 elderly (88 +/- 2 yr) men and women during exercise. All subjects had normal pulmonary function and performed graded cycle ergometry to exhaustion. Minute ventilation (V E), lung volume, and expiratory airflow limitation (EAFL) were measured during each 1-min increment in work rate. ⋯ EAFL (% of VT) increased with aging; elderly subjects experienced greater EAFL at rest (p < 0.05), VTh (p < 0.01), and peak exercise (p < 0.01) than both young and senior subjects. We conclude that mechanical ventilatory constraints are progressive with aging, elderly subjects demonstrating marked mechanical ventilatory constraints during exercise. The impact of these constraints on exercise tolerance cannot be determined from this investigation and remains unclear.
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Am. J. Respir. Crit. Care Med. · Jul 1999
Comparative StudyCalibration of seven ICU ventilators for mechanical ventilation with helium-oxygen mixtures.
The study evaluated seven intensive care unit (ICU) ventilators (Veolar FT, Galileo, Evita 2, Evita 4, Servo 900C, Servo 300, Nellcor Puritan Bennett 7200 Series) with helium-oxygen (HeO2), using a lung model, to develop correction factors for the safe use of HeO2. A 70:28 helium-O2 mixture (heliox) replaced air and combined with O2 (HeO2). Theoretical impact of HeO2 on inspiratory valves and gas mixing was computed. ⋯ With the Evita 4, VTdel > VTset (nonlinear relationship), whereas with the Servo 300 VTdel = VTset. In pressure control, VTdel was identical to control measurements, except with the 7200 Series (ventilator malfunction). Correction factors were developed that can be applied to most ventilators.