Effects of limping on normal exercise response.

Ten subjects performed two identical exercise tests on a motor-driven treadmill while walking normally or while limping. The two tests were separated by a rest period sufficient to permit return to a base-line state and the sugjects were randomly assigned to a normal-limp or limp-normal exercise sequence. Work rate was varied progressively by increasing treadmill grade in 5-degree increments to a maximum of 20 degrees, while limping was induced by insertion of a 0.5-cm wooden spike under the heel of the dominant foot. At all work rates, limping produced consistent increases in all variables studied, except for tidal volume where a decrease was seen. At the highest work rate these differences tended to disappear. Even considering the greater O2 consumption induced by limping, there were still significant (P less than 0.01) increases in both respiratory rate and ventilation at all but the highest work rate, accompanied by an insignificant fall in tidal volume. This suggests that these changes were not induced by the alterations in the internal or external work of walking and that limping somehow alters the regulation of exercise hyperpnea.

The effects of copper in heated nebulizers.

The antibacterial potential of copper mesh in heated nebulizers was evaluated by simulating clnical usage in the laboratory and comparing the relationship between the copper levels achieved in nebulizer water and the growth of Pseudomonas aeruginosa organisms. Mesh size, length of immersion, temperature, water replacement, and nebulization all affected copper concentration. Antibacterial acitivity was demonstrated over a wide range of copper levels for as long as three weeks. Nebulizers driven for one hour by 10 L/min of gas flow and containing 8 gm of copper mesh were inoculated with more than 31,000 organisms and became sterile within 60 minutes of inoculation. Units without copper showed a much slower decline in colony counts. Solutions of copper salts also proved to be effective antibacterial substances but only in much higher concentrations than those achieved with copper mesh. It it is concluded that metallic copper mesh is an effective antibacterial substance when used in water-containing heated nebulizers. Attempts to quantitate aerosolization of copper were not sucessful, and potential upper-airway deposition and human toxicity with this technique remain to be defined.