American journal of respiratory and critical care medicine
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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.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Comparative StudyLimitations of radionuclide angiographic assessment of left ventricular systolic function before lung transplantation.
To evaluate the influence of increased right ventricular afterload on radionuclide assessment of the left ventricular ejection fraction (LVEF), we compared the preoperative and postoperative value of isotopic LVEF in 11 patients who underwent lung transplantation and had a preoperative LVEF value below 55% (normal value: 68 +/- 8%). The underlying disease conditions were obstructive lung disease (n = 7) and pulmonary fibrosis (n = 4). The transplantation procedure was unilateral in 10 patients and bilateral in one. ⋯ We hypothesize that the low preoperative isotopic LEVF was not related to intrinsic dysfunction of the left ventricle, but rather to right ventricular pressure overload, leading to bulging of the interventricular septum into the left ventricle and to subsequent geometric distortion of the left ventricle. We conclude that isotopic LVEF may underestimate intrinsic left-ventricular systolic function in patients with severe chronic lung disease. Candidates for lung transplantation should not be rejected on the basis of a low isotopic LVEF, provided echocardiographic examination does show apparently normal left ventricular contraction.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Hypercapnic acidosis may attenuate acute lung injury by inhibition of endogenous xanthine oxidase.
Relative hypoventilation, involving passively-or "permissively"-generated hypercapnic acidosis (HCA), may improve outcome by reducing ventilator-induced lung injury. However, the effects of HCA per se on pulmonary microvascular permeability (Kf,c) in noninjured or injured lungs are unknown. We investigated the effects of HCA in the isolated buffer-perfused rabbit lung, under conditions of: (1) no injury; (2) injury induced by warm ischemia-reperfusion; and (3) injury induced by addition of purine and xanthine oxidase. ⋯ HCA (FICO2 25% versus 5%) reduced the elevation in Kf,c, capillary (Pcap), and pulmonary artery (Ppa) pressures in lung injury induced by exogenous purine/xanthine oxidase; inhibition of endogenous NO synthase in the presence of 25% FICO2 had no effect on Kf,c, but attenuated the reduction of Pcap and Ppa. HCA inhibited the in vitro generation of uric acid from addition of xanthine oxidase to purine. We conclude that in the current models, HCA is not harmful in uninjured lungs, and attenuates injury in free-radical-mediated lung injury, possibly via inhibition of endogenous xanthine oxidase.
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Am. J. Respir. Crit. Care Med. · Nov 1998
End-expiratory lung volume during arm and leg exercise in normal subjects and patients with cystic fibrosis.
There are no reports concerning the regulation of end-expiratory lung volume (EELV) and flow-volume relationships during upper limb exercise in health and disease. We studied EELV during such exercise in 22 adults with cystic fibrosis (CF) and nine age-matched healthy control subjects. Subjects with CF were grouped according to the severity of their lung disease, as follows: mild = FEV1 > 80% predicted; moderate = FEV1 40 to 80% predicted, and severe = FEV1 < 40% predicted. ⋯ For CF subjects there was a significant inverse relationship between FEV1 and changes in EELV from rest to peak arm exercise (r = -0.46, p < 0.05). In normal subjects, there was a difference in the EELV response for arm versus leg exercise. In CF subjects with airflow limitation, dynamic hyperinflation occurred with both forms of exercise.