Effects of hyperinflation on the oxygen pulse as a marker of cardiac performance in COPD.

A decreased inspiratory capacity (IC)/total lung capacity (TLC) ratio is associated with dynamic hyperinflation and decreased exercise capacity. The present authors hypothesised that static (low IC/TLC) and dynamic hyperinflation impair cardiac function as assessed by oxygen pulse at rest and during cardiopulmonary exercise testing (CPET). Lung function, body mass index, hand grip strength and CPET parameters were measured (oxygen uptake (mL x kg(-1) x min(-1)) and oxygen pulse (mL x beat(-1))) in 87 chronic obstructive pulmonary disease (COPD) patients (American Thoracic Society/European Respiratory Society/Global Initiative for Chronic Obstructive Lung Disease stage 3-4) and 46 controls. The patients were divided into those with IC/TLC > 25% or < or = 25%. The IC/TLC ratio at rest and at peak exercise was associated significantly with oxygen pulse. Patients with IC/TLC < or = 25% (n = 45) had significantly lower exercise capacity, peak oxygen pulse, peak minus baseline oxygen pulse, peak IC, peak IC/TLC ratio and % change from baseline to peak IC/TLC ratio compared with patients with IC/TLC > 25% and controls. During CPET, the oxygen pulse was lower at iso-work in patients with IC/TLC < or = 25% than in those with IC/TLC > 25%. Resting hyperinflation (inspiratory capacity/total lung capacity) is associated with lower oxygen pulse, peak exercise inspiratory capacity/total lung capacity and exercise capacity in patients with severe chronic obstructive pulmonary disease. The present results support an interaction between hyperinflation and decreased cardiac function that may contribute to exercise limitation in these patients.

Fretting corrosion accelerates crevice corrosion of modular hip tapers.

The use of multiple-component systems in orthopedic surgery gives the surgeon increased flexibility in choosing the optimal implant, but introduces the possibility of interfacial corrosion. Such corrosion could limit the longevity of prostheses due either to tissue reactions to corrosion products, or to device failure. The incidence and nature of corrosion of modular total hips was evaluated in a consecutive series of 79 retrieved implants from University Hospitals of Cleveland. Surfaces were examined with stereo- and scanning electron microscopy. Several laboratory studies were undertaken to examine mechanisms that might contribute to the initiation of corrosion. The first set of experiments investigated the effect of head neck extension; the second study looked at the effect of material combinations on fretting corrosion and crevice corrosion. Analysis of retrieved implants demonstrated that fretting corrosion played a major role in the initiation of interface corrosion, and that a correlation existed between corrosion and length of neck extensions. Laboratory studies showed that longer head neck extensions may be more susceptible to fretting corrosion because of an instability at the interface. Short-term mixed-metal corrosion studies demonstrated that the coupling of cobalt and titanium alloys did not render the interface more susceptible to corrosion. It is hypothesized that fretting corrosion contributes to the initiation of modular interface corrosion, and that the problem can be reduced by design changes that increase the stability of the interface.