Search PubMed⌕ Search

Biomedical subjects

F W Cheney

Publications and source records attributed to F W Cheney.

113 records · Page 7Linked to original sources
PubMedDate not supplied

Oxygen and resolution of lung injury.

We investigated the effects of varying inspired oxygen concentrations on the resolution of oleic acid-induced lung injury in rabbits. Rabbits were injected intravenously with oleic acid and maintained in room air, or exposed to 60, 70, or 80% oxygen for periods of 7 or 10 days. Oleic acid caused hemorrhagic pulmonary edema with hypoxemia. Hypoxemia was more profound in the oxygen-treated animals, a difference that was significant after 7 days' exposure to 60 and 70% oxygen, and after 4 days to 80% oxygen. Mortality was increased in the animals maintained in 80% oxygen. The data suggest that environmental oxygen concentrations greater than 60% interfere with the return to normal lung function following oleic acid injury in rabbits. The hypoxemia may be due to either mismatching of ventilation and perfusion or to a diffusion block resulting from the increased septal width. There was no evidence of massive pulmonary edema as a cause of the hypoxemia. It was not possible to distinguish between injury primarily caused by oxygen and its interference with the healing process.

Animals↗
PubMedDate not supplied

Comparison of the effects of minoxidil and nifedipine on hypoxic pulmonary vasoconstriction in dogs.

We studied the effects of hypoxia on pulmonary hemodynamics and gas exchange before and after minoxidil or nifedipine administration. The studies were carried out in eight normal dogs to determine the relative effects of these two drugs in inhibiting hypoxic pulmonary vasoconstriction. Each dog was studied twice--once with each drug--and exposed repeatedly to hypoxia on each day. Minoxidil raised cardiac output from 2.84 +/- 0.19 to 4.67 +/- 0.29 L/min (mean +/- SE), whereas nifedipine raised it from 3.04 +/- 0.25 to 4.38 +/- 0.38 L/min. Prior to the drugs, hypoxia raised pulmonary vascular resistance 2.4-fold. Minoxidil abolished this pressor response, while nifedipine reduced this response to a 1.6-fold increase. Minoxidil raised venous admixture during normoxia from 6 +/- 1 to 16 +/- 4%, while nifedipine raised it from 7 +/- 1 to 11 +/- 2%. Both drugs are inhibitors of the vasoconstrictive response to hypoxia. At the doses used, minoxidil was a more potent inhibitor of the pressor response to hypoxia than was nifedipine.

Animals↗
PubMedDate not supplied

Comparison of positive end-expiratory pressure and inspiratory positive pressure plateau in ventilation of rabbits with experimental pulmonary edema.

We investigated the effects of an inspiratory positive pressure plateau produced by a high (4/1) inspiratory-expiratory (I/E) ratio in rabbits with pulmonary edema induced with oleic acid. With an inspiratory pressure plateau, intrapulmonary shunt was significantly reduced compared to a standard 1/2 I/E ratio. Reduction in shunt was also obtained when positive end-expiratory pressure (PEEP) was added to the 1/2 I/E ratio ventilatory pattern. Since the improvement in shunt could have been caused by either recruitment of alveoli or by maintenance of lung volume at end exhalation we measured tidal volume and thoracic gas volume to distinguish between the two. With both patterns, improvement in shunt was associated with an increase in thoracic gas volume. The increase in thoracic gas volume was greater with PEEP than with 4/1 for an equivalent increase in mean airway pressure. The results suggest that an inspiratory pressure plateau improves gas exchange in pulmonary edema, but that this improvement occurs because of an increase in end-expiratory lung volume. Positive end-expiratory pressure is a preferable method of increasing end expiratory lung volume because a greater increase occurs for the same change in airway pressure.

Animals↗