American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Nov 1998
Comparative StudyA computed tomography scan assessment of regional lung volume in acute lung injury. The CT Scan ARDS Study Group.
The lobar and cephalocaudal distribution of aerated and nonaerated lung and of PEEP-induced alveolar recruitment is unknown in acute lung injury (ALI). Dimensions of the lungs and volumes of aerated and nonaerated parts of each pulmonary lobe were measured using a computerized tomographic quantitative analysis and compared between 21 patients with ALI and 10 healthy volunteers. Distribution of PEEP-induced alveolar recruitment along the anteroposterior and cephalocaudal axis and influence of the resting volume of nonaerated lower lobes were also assessed. ⋯ In ALI, loss of lung volume involves predominantly lower lobes. The thorax shortens along its cephalocaudal axis. PEEP-induced alveolar recruitment predominates in nondependent and cephalad lung regions and is inversely correlated with the resting volume of nonaerated lung.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Positive end-expiratory pressure improves gas exchange and pulmonary mechanics during partial liquid ventilation.
Partial liquid ventilation (PLV) with perflubron (PFB) has been proposed as an adjunct to the current therapies for the acute respiratory distress syndrome (ARDS). Because PFB has been also referred to as "liquid PEEP," distributing to the most gravity-dependent regions of the lung, less attention has been paid to the amount of applied positive end-expiratory pressure (PEEP). We hypothesized that higher PEEP levels than currently applied are needed to optimize gas exchange, and that the lower inflection point (LIP) of the pressure-volume curve could be used to estimate the amount of PEEP needed when the lung is filled with PFB. ⋯ Pulmonary shunt, and ratio of dead space volume to tidal volume (VD/VT) decreased, and static lung compliance increased with PEEP at LIP +1 cm H2O (p < 0.05). No changes were observed in hemodynamics. We conclude that increasing the dose of PFB shifts the LIP to the left, and that setting PEEP at LIP +1 cm H2O improves gas exchange at moderate to high doses of PFB.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Prostaglandins E2 and F2alpha reduce exhaled nitric oxide in normal and asthmatic subjects irrespective of airway caliber changes.
Cyclooxygenase products modulate the expression of nitric oxide synthase (NOS) in certain cell types. We determined the effect of prostaglandins (PG) E2 and F2alpha on exhaled nitric oxide (NO) concentrations measured by chemiluminescence. Inhaled PGE2 and PGF2alpha significantly reduced exhaled NO. ⋯ Although the prostaglandins did not change FEV1 in normal subjects, PGE2 caused an increase in asthmatics (from 3.6 +/- 0.3 L to 3.8 +/- 0.4 L, p < 0.05) and PGF2alpha caused a transient reduction in FEV1 from 4.0 +/- 0.2 L to 3.5 +/- 0.2 L (p < 0.05). To further determine the relationship between bronchoconstriction and exhaled NO levels, we examined the effect of inhaled methacholine which did not change exhaled NO concentrations in normal and asthmatic subjects despite a greater than 20% fall in FEV1 in asthmatics. Therefore, PGE2 and PGF2alpha reduce exhaled NO, an effect not related to airway caliber changes but which may result from an inhibition of nitric oxide synthase (NOS), particularly inducible NOS (iNOS).
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Am. J. Respir. Crit. Care Med. · Nov 1998
Effect of different pressure levels on the dynamics of lung collapse and recruitment in oleic-acid-induced lung injury.
The effects of different inspiratory and expiratory airway pressures (Paw) on the dynamics of lung collapse and recruitment were studied in 14 anesthetized, mechanically ventilated, pigs with oleic-acid-induced lung injury. Repetitive CT scans of the same slice were obtained every 0.8 s during different inspiration and expiration hold procedures. The mean lung density and amount of atelectasis were measured in each scan. ⋯ PEEP of 20 or 25 cm H2O almost prevented lung collapse during expiration. Thus, in order to avoid cyclic alveolar collapse during mechanical ventilation in oleic-acid-induced lung injury, a PEEP level >= 20 cm H2O or an expiration time <= 0.6 s is required. Long inspiratory time intervals, as used in inverse ratio ventilation, seem to be of minor importance for the recruitment of collapsed lung tissue in this experimental model.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Comparative StudyAngiotensin-converting enzyme gene polymorphism and risk of sarcoidosis.
The angiotensin-converting enzyme (ACE) has been implicated in the pathophysiology of sarcoidosis. Serum ACE levels in normal and sarcoidosis patients are influenced by an insertion (I)/deletion (D) polymorphism in the ACE gene. To elucidate the role of this ACE gene polymorphism in sarcoidosis, we conducted a case-control study in African Americans and Caucasians. ⋯ Further analyses of African-American cases showed that the ACE genotype was not associated with disease severity, extrathoracic involvement, or overall radiographic change 2 to 4 yr after diagnosis. We did find a moderate association between the II genotype and radiographic progression (OR = 2.97; 95% CI = 1.01 to 8.76). Our results suggest the ACE genotype may play a more important role in sarcoidosis susceptibility and progression in African Americans than Caucasians.