Significant exercise-induced hypoxaemia with equivocal desaturation in patients with chronic obstructive pulmonary disease.

BACKGROUND: The wide 95% confidence interval for S(a)O2 measured by pulse oximetry (S(P)O2) and the inherent characteristics of the oxyhaemoglobin dissociation curve can lead to modest but significant decreases in P(a)O2 (deltaP(a)O2 > or = 5 mmHg) that may be under-appreciated. AIM: To avoid missing potentially significant deltaP(a)O2 by using S(P)O2, this study establishes a threshold of deltaS(P)O2 to detect deltaP(a)O2 by examining the correlation between deltaS(P)O2 and deltaP(a)O2. METHODS: We enrolled 29 elderly patients with moderate to severe chronic obstructive pulmonary disease as assessed by lung function testing. Arterial blood gases and S(P)O2 measurements were carried out during maximal exercise testing. The patients were assigned to groups based on P(a)O2 measurements: group 1 had P(a)O2 at peak exercise (P(a)O2peak) > or = 60 mmHg without a deltaP(a)O2; group 2 had P(a)O2peak > or = 60 mmHg with a deltaP(a)O2; group 3 had P(a)O2peak < 60 mmHg without a deltaP(a)O2; and group 4 had P(a)O2peak < 60 mmHg with a deltaP(a)O2. RESULTS: The study population was evenly distributed between groups 1, 2 and 4. However, group 3 did not have any patients enrolled in this study that met group 3 criteria. The sensitivity of pulse oximetry required to detect S(a)O2 below 90% was 19%. DeltaS(P)O2 of 3% may increase the low sensitivity of S(P)O2 and was shown by a 92% positive predictive value for deltaP(a)O2 > or = 5 mmHg. CONCLUSION: This study suggests that important changes in oxygenation may be avoided if using deltaS(P)O2 rather than absolute values of S(P)O2 in patients with chronic obstructive pulmonary disease undergoing exercise testing to detect exercise-induced hypoxaemia.

Oligoclonal immunoglobulin G in acute subarachnoid hemorrhage and stroke.

Oligoclonal Ig bands were found in serum and CSF of 13 of 83 patients (16%) with verified subarachnoid hemorrhage (SAH). Serum Ig bands were more common in patients with SAH than in those with cerebral ischemia. The reverse was true with oligoclonal Ig bands in CSF. These patterns suggest that there are two different mechanisms and sites of IgG synthesis: an inflammatory process after acute stage of vascular damage and a latent immunologic process--ie, polyclonal B-cell activation by injury to the brain.

Incorporation of radioactivity from U-14C-glucose into oligodendrocytes and myelin of quaking mice and their littermate controls.

Oligodendrocytes and myelin were purified from the cerebra of quaking mice and their littermate controls (11-60 days of age) after injecting the animals intraperitoneally with U-14C-glucose. A peak of incorporation of radioactivity in the lipid extract of oligodendrocytes of both quaking and normal mice at 16-18 days of age was found, suggesting that the onset of myelination in the cerebra starts approximately at the same time for quaking mice and their littermate controls. Nevertheless the level of incorporation per cell was lower in the oligodendrocytes of quaking mice (50% of the control). The pattern of incorporation into myelin during development was similar between the two strains, but the specific activity as measured in dpm/mg protein was higher in the myelin of young quaking animals (up to 16 days). Peaks of incorporation were found in cerebrosides and sulfatides of oligodendrocytes and myelin in normal controls at 18 days. In the quaking mice these peaks were absent in oligodendrocytes and much delayed in the myelin of the mutant. The results would suggest that the defect in the quaking mutant in respect to myelination is in oligodendrocyte metabolism and thus in an early stage of the assembly of the myelin membrane.