Publications

Using a rat model of acid-induced lung injury, we tested the hypothesis that tidal volume reduction at the same level of PEEP (10 cm H(2)O) would diminish the degree of pulmonary edema by attenuating injury to the alveolar epithelial and endothelial barriers. Tidal volume reduction from 12 to 6 to 3 ml/kg significantly reduced the rate of lung water accumulation from 690 microl/h to 310 microl/h to 210 microl/h. Ventilation with either 6 or 3 ml/kg reduced endothelial injury equally as measured by plasma vWf:Ag and permeability to albumin. Plasma RTI40, a marker of type I epithelial cell injury, decreased 46% when tidal volume was reduced from 12 to 6 ml/kg and decreased an additional 33% with 3 ml/kg (p < 0.05). The rate of alveolar epithelial fluid clearance was significantly faster in the 3-ml/kg group (24 +/- 7%/h) compared with 6 ml/kg (15 +/- 11%/h) and 12 ml/kg (3 +/- 6%/h). We conclude that low tidal volume ventilation protects both the alveolar epithelium and the endothelium in this model of acute lung injury. The additional decrease in pulmonary edema with a tidal volume of 3 ml/kg is partly accounted for by greater protection of the alveolar epithelium.

PURPOSE

To quantitatively evaluate hyperpolarized helium 3 ((3)He) diffusion magnetic resonance (MR) images of the lung in patients with emphysema and to determine whether apparent diffusion coefficients (ADCs) measured with MR imaging correlate with spirometric indexes.

MATERIALS AND METHODS

Hyperpolarized (3)He diffusion MR imaging was performed in 16 healthy volunteers and 11 patients. Coronal diffusion-sensitized MR images were obtained during suspended respiration after inhalation of laser-polarized (3)He gas, and images of the ADC were calculated. Spirometry was performed immediately before imaging. The mean and SD of the ADCs were compared between subject groups and were correlated with spirometric indexes.

RESULTS

ADC images were homogeneous in volunteers, but demonstrated regional variations in patients. The mean and SD of the ADCs for patients were significantly larger (P <.002) than those for volunteers. The mean ADCs for all subjects correlated with the percentage of predicted forced expiratory volume in 1 second, or FEV(1), (r = -0.797, P <.001) and the ratio of FEV(1) to forced vital capacity, or FVC, (r = -0.930, P <.001). ADC images in patients demonstrated a significant increase (P <.001) in the ADCs in the upper regions compared with the lower regions of the lung.

CONCLUSION

Hyperpolarized (3)He diffusion MR imaging demonstrated potential for use in evaluating the global and regional severity of emphysema.