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Biomedical subjects

C S Houston

Publications and source records attributed to C S Houston.

At least 127 records · Page 7Linked to original sources

Introductory address: lessons to be learned from high altitude.

A historical account of the important landmarks in man's experience with the high altitude environment is followed by comments on the important stages in the understanding of its physiological effects. The work of The Mount Logan High Altitude Physiology Study on acute mountain sickness is reviewed from its inception in 1967 until the present.

Acclimatization↗

The relationship between acute mountain sickness and pulmonary ventilation at 2,835 meters (9,300 ft).

We have demonstrated a small but statistically significant decrease in forced vital capacity and in pulmonary flow rates among 126 persons studied daily for the first three days after arrival at an altitude of 2,835 meters (9,300 ft). Nearly half of these individuals had symptoms attributable to altitude sickness, and those with the most dyspnea and worst headache also showed the greatest changes in pulmonary function studied. We suggest that there is a relationship between the symptoms of altitude sickness and pulmonary function consistent with the appearance of early interstitial or alveolar edema.

Acute Disease↗

Native children's lung.

A high proportion of Cree and other North American Indian children have a chronic cough and many have bronchial wall thickening on radiographs, reminiscent of white children with asthma, mild cystic fibrosis, or immune deficiency. When compared to postmortem studies, radiographs underestimate the degree of bronchial wall thickening present. As compared to white children, Indian children in the first two years of life are more susceptible to recurrent bronchitis and pneumonia, are much more likely to develop pneumonia with rubeola and pertussis, and are more likely to develop chronic lung disease after adenovirus infections. Staphylococcal complications with pneumatocele formation are more common. A greater number acquire pneumonia while in hospital with other medical or surgical problems. Indian children with pneumonia recover more slowly, and some continue to deteriorate even after admission to hospital.

Adolescent↗

Short-term adaptation to moderate altitude. Patients with chronic obstructive pulmonary disease.

Eight patients with mild-to-moderate chronic obstructive pulmonary disease (COPD) and average resting Pao2 of 66 mm Hg were studied clinically and physiologically at sea level and after ascent to 1,920 m. At sea level the patients were symptomatic but not disabled. After ascent the patients had only mild symptoms of fatigue and insomnia, and one had severe headache during exercise on the first day. Funduscopic changes were not observed, nor did cardiac or pulmonary findings change. Resting sea level Pao2 dropped to 51.5 mm Hg within three hours of ascent, and the Paco2 fell from 37.8 to 33.9 mm Hg. Over the next three days, the Pao2 increased to 54.5 mm Hg as hyperventilation continued. At exercise, sea level Pao2 dropped from a mean value of 63 to 46.8 mm Hg at altitude. Pulse rates at rest or exercise did not change. Normal values for 2,3-diphosphoglycerate (2,3-DPG) did not change after ascent at 16 and 42 hours. We believe aircraft flight or travel to moderate altitudes for this type of COPD patient is safe. Preexisting hypoxemia resulting from disease may facilitate the adaptation of patients to severe hypoxia and may prevent symptoms similar to acute mountain sickness.

Adaptation, Physiological↗

The radiologist's opportunity to teach bone dynamics.

Activity and muscle strength are important for bone growth and for development and maintenance of bone density. The rediologist should help students to understand the important relationship between muscular activity and bone strength.

Adolescent↗

Diagnostic irradiation of women during the reproductive period.

The date of onset of the last menstrual period should be given on radiographic requisitions for all women of reproductive age. Every effort should be made to avoid unnecessary irradiation of any woman who might be pregnant. Radiation damage in the first 2 weeks of pregnancy, however, should be "all or none", resulting in either a miscarriage or a normal child. Diagnostic radiology procedures are not indications for therapeutic abortion. Ultrasound has now replaced ionizing radiation in most examinations of the fetus and placenta. Pelvimetry should be done only when the decision to do a cesarean section hinges on precise knowledge of measurements of the bony pelvis. On the rare occasion when a radiograph of the fetus is necessary the woman should be prone for the examination. All such examinations are best ordered after consultation with a radiologist. Radiography of distant areas with the beam directed away from the woman's abdomen can be done without concern at any stage of pregnancy.

Abortion, Therapeutic↗

Potential hazards of diagnostic radiation.

There are no precise data for determining the extent of somatic damage from small doses of radiation used in diagnostic radiology. Diagnostic radiation given to pregnant women, knowingly or unknowingly, should rarely reach teratogenic levels causing brain and eye abnormalities. Evidence suggests that it does increase the risk of childhood malignancy, especially leukemia. Although rapidly growing tissues seem most susceptible, all radiation probably carries a very small risk of carcinogenesis. Genetic damage is equally difficult to estimate. Diagnostic radiation of females, even in childhood, may be related to an increased incidence of Down's syndrome in older mothers. Radiation also causes point mutations, which may explain the increase of some genetic abnormalities in progeny of older fathers. Whenever an abdominal or pelvic radiograph is ordered before the end of the reproductive period, there must be a potential benefit to balance the small risk involved.

Animals↗