Biomedical subjects

D A Norman

Publications and source records attributed to D A Norman.

At least 19 recordsLinked to original sources

PubMed1990

The 'problem' with automation: inappropriate feedback and interaction, not 'over-automation'.

As automation increasingly takes its place in industry, especially high risk industry, it is often blamed for causing harm and increasing the chance of human error when failures do occur. I propose that the problem is not the presence of automation, but rather its inappropriate design. The problem is that the operations under normal operating conditions are performed appropriately, but there is inadequate feedback and interaction with the humans who must control the overall conduct of the task. When the situations exceed the capabilities of the automatic equipment, then the inadequate feedback leads to difficulties for the human controllers. The problem, I suggest, is that the automation is at an intermediate level of intelligence, powerful enough to take over control that used to be done by people, but not powerful enough to handle all abnormalities. Moreover, its level of intelligence is insufficient to provide the continual, appropriate feedback that occurs naturally among human operators. This is the source of the current difficulties. To solve this problem, the automation should either be made less intelligent or more so, but the current level is quite inappropriate. The overall message is that it is possible to reduce error through appropriate design considerations. Appropriate design should assume the existence of error, it should continually provide feedback, it should continually interact with operators in an effective manner, and it should allow for the worst situations possible. What is needed is a soft, compliant technology, not a rigid, formal one.

Accidents, Aviation↗

PubMed1989

Direct current electrotherapy of internal hemorrhoids: an effective, safe, and painless outpatient approach.

Hemorrhoid disease is one of the most frequently occurring, disabling conditions of man. We report the results of 120 patients with symptomatic internal and mixed hemorrhoid disease treated with direct current (d.c.) via a dual-tipped disposable needle probe (negative electrode). Evaluation and treatment utilized an operative anoscope which visualized one-eighth of the anal canal. Five hundred ninety segments revealed hemorrhoid disease (grade 1 = 114, 2 = 222, 3 = 178, 4 = 76). One or more segments (highest grade) were treated per office visit. Symptoms, frequency, and mean number of treatment applications per patient for complete symptom resolution were: bleeding, 85%, 4.0; protrusion, 58%, 3.9; pain, 52%, 3.6; and pruritus, 49%, 3.9. Ablation of hemorrhoid disease grade was directly correlated with milliampere current and time of application. No major complications occurred. All patients were successfully treated and remained symptom-free at a mean duration of follow-up of 23 months. Direct current electrotherapy is an effective, painless, and safe outpatient treatment approach to all grades of internal and mixed hemorrhoid disease.

Adult↗

PubMed1985

Retropharyngeal infection in a pregnant diabetic. A case report.

A retropharyngeal infection occurred in a pregnant class C diabetic at 31 weeks' gestation. Early diagnosis, prompt therapy with antibiotics and possibly surgery for drainage if an abscess develops constitute optimal management.

Abscess↗

PubMed1983

Effect of 1,25-dihydroxyvitamin D3 on calcium and magnesium absorption in the healthy human jejunum and ileum.

In calcium deficiency states such as chronic renal failure, 1,25-dihydroxyvitamin D3 increases calcium and magnesium absorption toward normal levels. In the present study, the ability of exogenous 1,25-dihydroxyvitamin D3 to increase calcium and magnesium absorption above normal rates in healthy subjects was investigated. Steady-state perfusion studies were performed in 30 cm segments of jejunum and ileum before and after one week of 1,25-dihydroxyvitamin D3 administration (2 micrograms per day, 10 subjects). Serum 1,25-dihydroxyvitamin D concentration increased from 25.8 +/- 2.5 pg/ml to 56.4 +/- 6.6 (mean +/- SEM, p less than 0.05). In the basal state, calcium absorption was significantly higher in the jejunum than in the ileum. Vitamin D administration resulted in a significant increase in calcium absorption which was quantitatively similar in both the jejunum and ileum. The changes in net movement were due to an increase in lumen-to-plasma flux of calcium; the plasma-to-lumen flux remained unchanged. Jejunal magnesium absorption also was enhanced by 1,25-dihydroxyvitamin D3. These studies demonstrate that in healthy persons, exogenous 1,25-dihydroxyvitamin D3 increases calcium absorption in both the jejunum and the ileum, and increases magnesium absorption in the jejunum.

Adult↗

PubMed1981

An apparent 1,25-dihydroxyvitamin D-independent stimulation of intestinal calcium absorption in patients with Paget disease of bone during a short-term diphosphonate therapy.

Six patients with Paget disease of bone were treated with a 6-mo course of disodium-ethane-1-hydroxy-1, 1-diphosphate (EHDP) at a dosage of 5 mg/kg/day (one patient) or 20 mg/kg/day (five patients). In addition to symptomatic and biochemical improvement which persisted 3 mo after discontinuance of therapy, EHDP resulted in a significant increase in intestinal calcium absorption that was not correlated with a change in serum 1 alpha, 25-(OH)2-vitamin D concentration. EHDP appears to stimulate intestinal calcium transport by either a vitamin D independent process or by an increased intestinal mucosal cell sensitivity to vitamin D.

Aged↗

PubMed1980

Massive gastrointestinal hemorrhage from a diverticulum of the appendix.

A patient with massive gastrointestinal hemorrhage found to be bleeding from a diverticulum of the appendix is presented. Appendectomy was curative and pathologic changes were those associated with colonic diverticular hemorrhage. A review of the literature reveals this to be a previously unreported cause of gastrointestinal bleeding.

Appendectomy↗

PubMed1980

Simultaneous hepatic and renal involvement in acute syphilis. Case report and review of the literature.

An unusual case of simultaneously occurring acute syphilitic hepatic and renal disease is presented and a concise literature review of both the pathological and clinical findings in this disease is included. Hepatic and renal biopsies were useful in excluding other diagnostic possibilities and in establishing the correct diagnosis in the case presented.

Acute Disease↗

PubMed1980

Ambulatory evaluation of nephrolithiasis. Classification, clinical presentation and diagnostic criteria.

Using the ambulatory protocol previously described, 241 patients with nephrolithiasis were evaluated. They could be categorized into 10 groups from the results obtained. Absorptive hypercalciuria type I (87 per cent male) comprised 24.5 per cent and was characterized by normocalcemia, normal fasting urinary calcium (less than 0.11 mg/100 ml glomerular filtration), an exaggerated urinary calcium following an oral calcium load (greater than 0.20 mg/mg creatinine), normal urinary cyclic adenosine monophosphate (AMP) (less than 5.4 nmol/100 ml glomerular filtration) and serum parathyroid hormone (PTH), and hypercalciuria (greater than 200 mg/day during a calcium- and sodium-restricted diet). Absorptive hypercalciuria type II (50 per cent male) accounted for 29.8 per cent; its biochemical features were the same as those for absorptive hypercalciuria type I, except for normocalciuria during a restricted diet and low urine volume (1.42 +/- 0.55 SD liter/day). Renal hypercalciuria (56 per cent male), disclosed in 8.3 per cent, was represented by normocalcemia and high values for fasting urinary calcium (0.160 +/- 0.054 mg/100 ml glomerular filtration), urinary cyclic AMP (6.80 +/- 2.10 nmol/100 ml glomerular filtration) and serum PTH. Primary hyperparathyroidism (57 per cent female), accounted for 5.8 per cent, typically included hypercalcemia, hypophosphatemia, hypercalciuria and high urinary cyclic AMP. Hyperuricosuric calcium urolithiasis (100 per cent male) comprised 8.7 per cent, and was characterized by hyperuricosuria (776 +/- 164 mg/day) and urinary pH exceeding pK for uric acid (5.91 +/- 0.33). In enteric hyperoxaluria (60 per cent female), encountered in 2.1 per cent of cases, urinary oxalate was increased (6.29 +/- 13.2 mg/day). Noncalcium-containing stones were found in 2.1 per cent of the patients with uric acid lithiasis (100 per cent male) and in another 2.1 per cent of the patients with infection lithiasis (60 per cent female). These conditions were typified by low urinary pH (5.29 +/- 0.12) and high urinary pH (6.69 +/- 1.16), respectively. Renal tubular acidosis was found in one patient (male, 0.4 per cent). In 10.8 per cent of the patients (81 per cent male), no metabolic abnormality could be found, although urine volume was low (1.41 +/- 0.51 liter/day). Hypercalciuria could not be differentiated between absorptive hypercalciuria and renal hypercalciuria in 5.4 per cent of the patients. Thus, this ambulatory protocol disclosed a physiologic disturbance in nearly 90 per cent of the cases and provided a definitive diagnosis in 95 per cent of the patients.

Adult↗

PubMed1979

A patient with pseudohypoparathyroidism with increased serum calcium and 1 alpha, 25-dihydroxyvitamin D after exogenous parathyroid hormone administration.

The cause for the normal calcemic response to exogenous parathyroid hormone (PTH) was explored in a case of pseudohypoparathyroidism. The diagnosis of pseudohypoparathyroidism in this 29-yr-old woman was well established, since she had hypocalcemia (6.6 mg/dl), hyperphosphatemia (5.0 mg/ dl), high serum immunoreactive PTH, and negligible urinary cAMP response to exogenous PTH. Treatment with Amphojel slightly increased serum calcium (to 7.4 mg/dl) and lowered serum phosphorus (to 4.1 mg/dl) without altering the serum concentration of 1 alpha, 25-dihydroxyvitamin D [1,25(OH)2D]. After im administration of parathyroid extract (400 U/day for 4 days), serum calcium increased to 9.2 mg/dl, commensurate with significant elevations in serum 1,25(OH)2D (from 1.2 to 2.6 ng/dl) and fractional (intestinal) calcium absorption (from 0.22 to 0.43). The results suggest that the synthesis of 1,25(OH)2D upon PTH challenge was relatively intact and may have accounted for the normal calcemic response.

Adult↗

PubMed1978