Carbon dioxide contributes to the beneficial effect of pressurization in a portable hyperbaric chamber at high altitude

Regional cerebral oxygenation (rSO2) and peripheral oxygen saturation (SpO2) have been studied in subjects inside a portable hyperbaric chamber at altitude during pressurization. The effects of the accumulation of carbon dioxide within the chamber on rSO2 and SpO2 have also been investigated. Three studies of cerebral regional oxygenation were undertaken, using near-IR spectroscopy, in subjects who had ascended to 3475 m in the Alps, 4680 m in the Andes or 5005 m in the Himalayas. At 3475 m and 5005 m the effects of the removal of inspired carbon dioxide by a soda lime scavenger were also studied. On pressurization of the chamber to 19.95 kPa, inspired carbon dioxide rose within the chamber from 0.03% (0.06 kPa) ambient to over 1% (1.3 kPa). At 5005 m, SpO2 rose from a baseline of 79.5% (S.D. 4.5%) to 95.9% (2.0%) (P<0.0001), and cerebral rSO2 rose from 64.6% (3.4%) to 69.4% (3.6%) (P<0.0001). The introduction of a soda lime CO2 scavenger into the breathing circuit resulted in a drop in SpO2 from 95.9% (2.03%) to 93.6% (2.07%) (P<0.001) and a fall in rSO2 from 69.4% (3.64%) to 68.5% (3.5%) (P<0.01). Chamber pressure was maintained throughout at 19.95 kPa. Similar changes were seen at the other altitudes. Cerebral rSO2 increased rapidly following pressurization at all three altitudes. Scavenging of inspired carbon dioxide was associated with a significant fall in cerebral rSO2 and SpO2, and we estimate that the contribution of carbon dioxide may account for up to one-third of the beneficial effect of the portable hyperbaric chamber.

Antiphospholipid syndrome in pregnancy: a diagnostic dilemma

OBJECTIVE

To present a case of severe pre-eclampsia in which diagnosis of the antiphospholipid syndrome was made after delivery, and to discuss pointers to the diagnosis.

CLINICAL FEATURES

A 32-year-old woman in her second pregnancy presented at 32 weeks' gestation with severe pre-eclampsia. Her persisting severe postpartum illness was investigated. The presence of anticardiolipin antibodies and lupus anticoagulant led to the diagnosis of antiphospholipid syndrome.

INTERVENTION AND OUTCOME

Induction of labour was successful, with delivery of a healthy baby girl. The patient made a full recovery after treatment with corticosteroids and warfarin.

CONCLUSION

The antiphospholipid syndrome should be considered in cases of severe early pre-eclampsia.

Non-secretion of ABO blood group antigens as a host susceptibility factor in the spondyloarthropathies

Gram negative bacteria precipitate reactive arthritis and may be concerned in the pathogenesis of ankylosing spondylitis and other spondyloarthropathies. Susceptibility to many infectious agents is associated with ABO blood group or secretor state, or both. The distribution of the ABO blood group or secretor state, or both, was therefore determined in 87 patients with ankylosing spondylitis and 32 with other forms of spondyloarthropathy. The prevalence of non-secretors was significantly increased in the total patient group (54/114; 47%) and in the subgroup with ankylosing spondylitis (41/84; 49%) compared with local controls (89/334; 27%) (p less than 0.001). Other subgroups of patients showed a similarly increased prevalence of non-secretion (33-47%). The distribution of ABO blood groups did not differ between patients and controls. The association between non-secretor state and ankylosing spondylitis strengthens the hypothesis that ankylosing spondylitis is a form of reactive arthritis. It also suggests several pathogenic mechanisms which may be relevant to the initial hostparasite interaction in ankylosing spondylitis.

Effect of acetazolamide on exercise performance and muscle mass at high altitude

The effect of acetazolamide (Az) on exercise performance and muscle mass in acclimatised subjects at an altitude of 4846 m was assessed in 11 subjects and compared with the effect of placebo on 10 other subjects. Exercise performance at 85% maximum heart rate fell by 37% in the Az group and by 45% in controls (p less than 0.05). Weight loss was greater in the placebo group at high altitude (p less than 0.01) and this correlated with the fall in exercise performance (p less than 0.001). During the expedition anterior quadriceps muscle thickness fell by 12.9% in the control group and 8.5% in the Az group (p less than 0.001), while biceps muscle thickness fell by 8.6% in controls and 2.3% in the Az group (p less than 0.001). Measurements of skin-fold thickness indicated a loss of 18% of total body fat in the placebo group and 5% in the Az group by the end of the expedition (p less than 0.001). Calorie intakes at altitudes above 3000 m were low and similar for the two groups. The Az group had fewer symptoms of acute mountain sickness but differences between the two groups were not statistically significant. Acetazolamide is therefore useful for climbers and trekkers who are acclimatised to high altitudes. It could be most useful at extreme altitudes, where maintenance of exercise performance and muscle mass are important.

The effect of antirheumatic drugs on circulating immune complexes in rheumatoid arthritis

The relationship between antirheumatic drug treatment and levels of circulating immune complexes (125I-C1q binding activity) has been investigated in a prospective two-year study of patients with rheumatoid arthritis using the erythrocyte sedimentation rate (ESR) and serum C-reactive protein concentration as indices of disease activity. Twenty-eight patients were treated with non-steroid anti-inflammatory drugs, 14 patients had 'second line' drugs and 13 patients were treated with adrenal corticosteroids. Serum 125I-C1q binding activity did not change during non-steroid anti-inflammatory drug treatment; however, immune complex levels did fall during treatment with new (ICI 55,897, sulphasalazine) and established (gold, penicillamine) second line drugs. Serum 125I-C1q binding activity reflected the response to treatment shown by serum C-reactive protein and ESR. Serum C-reactive protein concentration and ESR fell with all doses of adrenal corticosteroids. In contrast, immune complex levels did not fall when doses of adrenal corticosteroids were below 20 mg/day prednisolone. 125I-C1q binding activity fell during high dose adrenal corticosteroid therapy (greater than 40 mg/day prednisolone; 1 g methylprednisolone infusions). Serial measurements of 125I-C1q binding activity correspond to ESR and the serum C-reactive protein concentration in distinguishing between anti-inflammatory drugs, which provide symptomatic relief only, and second line drugs which may retard disease progression. The fall in circulating immune complex levels during 'high' dose corticosteroid treatment, but not during 'low' dose treatment, suggests that corticosteroids have a dose-dependent effect on the immune system in addition to their anti-inflammatory properties.

Effect of different ascent profiles on performance at 4,200 m elevation

Two groups of sea level residents were studied at the summit of Mauna Kea (4,200 m elevation) following ascent by vehicle. "Commuters" spent 6 h at the summit, while "shiftworkers" lived on the mountain for 5 d. Although PaO2 levels were lower in commuters, they experienced fewer altitude sickness symptoms than shiftworkers on the first day at 4,200 m. After 5 d, shiftworkers reported fewer symptoms and performed better at tests of numerate memory and psychomotor ability than commuters. At high altitude, pulse rates were increased in both groups, but only shiftworkers exhibited an elevation in systemic blood pressure. Arterial-alveolar oxygen tension gradients were not increased at 4,200 m. Despite frequent and rapid ascents and descents, with minimal provision for acclimatization, high altitude pulmonary and cerebral oedema were uncommon.

A comparison between clinical and laboratory tests in rheumatoid arthritis

Five clinical measurements (clinical score, articular index, visual analogue pain score, visual analogue function score, grip strength) were compared with two laboratory tests (the erythrocyte sedimentation rate and serum C-reactive protein concentration) in 68 patients with rheumatoid arthritis (RA). Patients treated with nonsteroid anti-inflammatory drugs showed clinical deterioration when treatment was interrupted, followed by improvement on resumption; there was no change in the laboratory tests. Patients treated with remission-inducing drugs (RIDs) had improved clinical measurements and also reduced erythrocyte sedimentation rate and serum C-reactive protein levels. Treatment with RID's led to similar trends in both clinical and laboratory tests, but correlation coefficients between the tests at intervals rarely attained statistical significance. The different response times for each test and probably also errors inherent in clinical measurements introduced sufficient variability to account for the discrepancy. Of the clinical tests, 'clinical score' appeared the most satisfactory.

High-dose intravenous methylprednisolone in rheumatoid arthritis

Fourteen patients with severe rheumatoid arthritis (RA) were given 27 courses of methylprednisolone intravenously, each of 3 infusions of 1 g on alternate days. After 7 days there was marked improvement in clinical state and most laboratory tests; levels of ESR and 4 serum acute-phase proteins, C3, C, IgG, and IgA, fell significantly. Serum IgM and rheumatoid factor titre were unchanged. 125I C1q binding fell in all instances where it was initially raised. Clinical remission lasted a mean of 10 weeks. Serum C-reactive protein (CRP) fell to less than 30 mg/l after all courses except one within 7 days and rose above this figure after a mean of 7 weeks. The ESR fell below 30 mm/h within seven days in 17 courses and remained below this value for a mean of 7 weeks. Three patients had clinical remissions, with serum CRP less than 30 mg/l and ESR less than 30 mm/h, lasting more than 42 weeks.

Sulphasalazine in rheumatoid arthritis

Seventy-four patients with rheumatoid arthritis were treated with sulphasalazine. There was a significant improvement in clinical score, with substantial falls in serum C-reactive protein concentrations and erythrocyte sedimentation rate four weeks after starting the drug. Improvement was maintained in the 38 patients who remained on the drug for one year. The mean Rose-Waaler titre did not change. There was little difference between the results in seropositive and seronegative patients. The commonest adverse effect was dyspepsia, but five patients developed a megaloblastic anaemia and one patient neutropenia; all made a complete recovery. The results suggest that the drug has a disease-modifying action not attributable to its "salicylate" content. The mode of action might be by an antibacterial effect on gut flora.

Rheumatoid arthritis: effects of a new agent (ICI 55 897) on serum acute phase proteins and the erythrocyte sedimentation rate

Thirty-four patients with rheumatoid arthritis (RA) were treated with a new agent (ICI 55 897) in addition to basic therapy with nonsteroid anti-inflammatory drugs. Five patients had the drug for less than 28 days; the remaining 29 were observed for periods up to a year. At 140 days, when all but 2 patients were in the study, there had been statistically significant improvement in clinical score, serum C-reactive protein, erythrocyte sedimentation rate, and plasma fibrinogen. Thereafter results continued to improve but were biased because some patients had stopped taking the drug. The final conclusion was that 17 patients had improved with 1 late relapse, and 15 had not responded. Adverse effects were trivial except in 2 instances: one patient had a transient unexplained rise in blood urea, another had a haematemesis. Neither effect could be attributed with certainty to the drug. ICI 55 897 has no intrinsic analgesic or anti-inflammatory properties. We suggest the findings of this study indicate that this agent, with low toxicity and the ability to lower acute-phase protein levels, may be an alternative to gold or penicillamine in the treatment of RA.