American journal of respiratory and critical care medicine
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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.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Comparative StudyAerosolized soluble nitric oxide donor improves oxygenation and pulmonary hypertension in acute lung injury.
Acute respiratory distress syndrome (ARDS) is a major cause of morbidity and mortality in critically ill patients. The associated ventilation/perfusion mismatch and pulmonary hypertension are amenable to treatment with inhaled nitric oxide (NO) gas. Compounds formed by reacting NO with various nucleophiles (NONOates) release NO spontaneously and induce vasodilation. ⋯ After aerosol treatment, animals in the DMAEP/NO group had a greater reduction in pulmonary vascular resistance index (PVRI) than did control animals (from 81 +/- 17 dyne. s/cm5/kg to 34 +/- 8 dyne. s/cm5/kg; and from 104 +/- 16 dyne. s/cm5/kg to 64 +/- 11 dyne. sec/cm5/ kg in the saline group at 60 min, p < 0.05). There were no differences between the groups in systemic vascular resistance index (SVRI), cardiac index (CI), methemoglobin, nitrite/nitrate, or lung pathology scores. We conclude that DMAEP/NO improves oxygenation and has selective pulmonary vasodilating properties without causing significant systemic toxicity in this porcine model of acute lung injury.
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Am. J. Respir. Crit. Care Med. · Nov 1998
Diaphragm sarcolemmal injury is induced by sepsis and alleviated by nitric oxide synthase inhibition.
Endotoxemia is associated with impaired diaphragm contractility, and increased nitric oxide (NO) production has recently been implicated in this phenomenon. However, the precise nature of sepsis-related alterations in diaphragm myofiber function remains unclear. We tested the hypothesis that enhanced NO synthesis during sepsis produces diaphragm sarcolemmal injury with attendant abnormalities of myofiber membrane electrophysiology. ⋯ An inhibitor of NOS activity, LNMMA, significantly decreased morphologic as well as electrophysiologic signs of myofiber membrane injury and dysfunction. Therefore, we conclude that both acute endotoxemia and subacute peritonitis models of sepsis lead to significant sarcolemmal damage and altered Em in diaphragm myofibers. These changes appear to be mediated, at least in part, through the pathway of increased nitric oxide production.