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Biomedical subjects

A A Bühlmann

Publications and source records attributed to A A Bühlmann.

18 recordsLinked to original sources
PubMed1989

[Pathophysiology of dyspnea].

The sensation of dyspnea is related to pathologically increased breathing work as a result of hyperventilation and/or increased airway resistance. Low cardiac output resulting in tissue hypoxia provokes hyperventilation. In diffuse interstitial lung diseases, hyperventilation is combined with severely reduced lung compliance. In severe airway obstruction, hypoventilation is the result of excessively enhanced breathing work. Habituation and acute changes of situation have an important bearing on the subjective sensation of dyspnea.

Airway Resistance↗
PubMed1989

[Incidents in sports diving].

Barotrauma of the ear is the most frequent incident in sport-diving. In some cases, inner ear disorders appear. Barotrauma with rupture of the lung can provoke gas embolism into the central nervous system and unconsciousness. Gas embolism into the spinal cord and decompression sickness of the spinal cord provoke practically the same neurological disturbances. The lower half of the body is mostly affected. Drowning in sport-diving is mostly the result of loss of consciousness resulting from hypoxia or hyperoxia, nitrogen-narcosis or gas embolism into the brain. Inner ear disorders, gas embolism in the brain or the spinal cord, decompression sickness of the spinal cord or the muscles and joints require treatment in the pressure chamber with hyperbaric oxygen. This treatment remains effective even if started some days after the dive.

Barotrauma↗
PubMed1989

[Decompression problems in diving in mountain lakes].

The relationship between tolerated high-pressure tissue nitrogen and ambient pressure is practically linear. The tolerated nitrogen high pressure decreases at altitude, as the ambient pressure is lower. Additionally, tissues with short nitrogen half-times have a higher tolerance than tissues which retain nitrogen for longer duration. For the purpose of determining safe decompression routines, the human body can be regarded as consisting of 16 compartments with half-times from 4 to 635 minutes for nitrogen. The coefficients for calculation of the tolerated nitrogen-high pressure in the tissues can be deduced directly from the half-times for nitrogen. We show as application the results of 573 simulated air dives in the pressure-chamber and 544 real dives in mountain lakes in Switzerland (1400-2600 m above sea level) and in Lake Titicaca (3800 m above sea level). They are in accordance with the computed limits of tolerance.

Altitude↗
PubMed1988

[Computation of low-risk compression. Computation model and results of experimental decompression research].

1. The relationship between tolerated nitrogen oversaturation and ambient pressure is practically linear. 2. Tissues with short half-times have a higher tolerance than tissues with long half-times. 3. The human body can be regarded as consisting of 16 compartments with half-times from 4 to 635 minutes for nitrogen and from 1.5 to 240 minutes for helium. 4. The coefficients for calculation of minimal tolerated ambient pressure for a given PN2 in the tissue can be deduced directly from the half-times for nitrogen. 5. The results of 573 simulated air dives and 544 real dives in mountain lakes are in accordance with the computed limits of tolerance. 6. The ZH-L16 system is applicable to all exposures with air or oxygen-nitrogen mixtures. 7. Adaptation to breathing of oxy-helium or trimix is simple.

Atmospheric Pressure↗
PubMed1987

Decompression after repeated dives.

Seventy-six men and 7 women performed a 2nd dive in a pressure chamber under dry conditions after intervals at the surface of 10, 30, 90, or 120 min. Of these, 35 persons performed a 3rd dive after an interval of 20 or 90 min (118 repeated dives). Air was the breathing gas during all phases of the tests. During exposure to overpressure the divers exercised on a bicycle-ergometer. The decompressions for dives 2 and 3 were the same as for the first dive. After the 2nd or 3rd dive, certain symptoms of decompression sickness of the skin occurred in 5 of the 118 exposures, and 1 diver complained of muscular aches. These results suggest that no general sensitization occurred after the 1st dive. We concluded that a slightly more conservative decompression with regard to ascent velocity and profile is feasible for repeated dives.

Adult↗
PubMed1979

[Hyperventilation and airway resistance. Bronchial spasms after hyperventilation].

Airway resistance, FEV1.0 and lung volume were measured by body plethysmography before and after voluntary hyperventilation. In normal subjects, resistance increased to 130--140% of the initial value measured before hyperventilation. The same increase was observed in silicosis patients without chronic obstructive bronchitis. Asthmatic patients in an asymptomatic phase showed a rise in airway resistance to an average of 255% of the nearly normal initial values, and also a reduction in FEV1.0. In normal subjects and asthmatic patients, the administration of bronchodilators inhibits the rise in airway resistance induced by hyperventilation. The hyperventilation test can be used to identify increased susceptibility to bronchoconstriction.

Asthma↗
PubMed1979

[Hyperventilation and oxygen supply of the myocardium. II. Effect of nitroglycerin and dipyridamole].

1. Voluntary hyperventilation during rest in the recumbent position induces a fall in H+ concentration, PCO2 and PO2 in mixed venous blood and in the blood of the coronary sinus. 2. If the breathing volume is increased during voluntary hyperventilation between 2- and 2.5 fold above the volume at rest, O2 uptake increases by only 6% but CO2 excretion rises by 66%. 3. Cardiac output decreases by 8% and the O2 extraction of the myocard increases by 12%. There is a quantitative relationship between arterial pH or PCO2 and changes in the systemic and coronary circulation. Blood pressure decreases in the pulmonary circulation. 4. Nitroglycerin during hyperventilation produces an additional reduction in cardiac output but no effect on the O2 extractions of the myocard. 5. With dipyridamol, the O2 extraction of the myocard is reduced and the PO2 in the blood of the coronary sinus increases. 6. In the case of severe coronary obstruction, the effect of dipyridamol can cause acute angina pectoris and left heart insufficiency due to poststenotic ischemis (steal syndrome).

Adult↗
PubMed1979

[Normal values for vital capacity and forced expiratory capacity of the lungs in old age].

In 545 healthy men aged 71-90 years and 160 women aged 71-85 years, vital capacity and FEV1.0 in the standing position were measured using a closed spirometer system. Analysis of the results from different groups based on age and body size makes it possible to extend an already existing nomogram for prediction of normal values for vital capacity up to 90 years in men and up to 80 years in women. There is no linear relationship between age and vital capacity in men and women aged 20-90 years. The average FEV1.0 is more than 70% of the effective vital capacity in men and women aged 71-90 and 71-85 years respectively. A reduction of more than 20% in vital capacity, and a FEV1.0 below 65% of the actual vital capacity, is to be considered pathological in men and women of any age.

Age Factors↗
PubMed1978

[Hyperventilation and oxygen supply to the myocardium].

1. Voluntary hyperventilation during rest and in the recumbent position induces a fall in H+ concentration, PCO2 and PO2 in mixed venous blood and in the blood of the coronary sinus. 2. In 7 of 12 patients the arterio-venous O2 difference increased by more than 10% of the control value (mean increase 21%). At the same time the O2 extraction of the myocard increased (mean increase 17%) in these subjects. Blood pressure and pulse rate varied only slightly in these experiments. 3. Chest pain and angina pectoris due to hyperventilation are the result of impaired myocardial O2 supply, a finding which is valid for subjects with and without coronary heart disease.

Angina Pectoris↗
PubMed1978

[Lung emphysema].

1. Elastic recoil, size of the perfused surface for gas exchange and flow resistance of the small airways influence the symptomatology and lung function of pulmonary emphysema independently of each other. 2. The loss of elastic force and surface for gas exchange are predominant in panlobular emphysema. Ventilation-perfusion disturbances due to increased airway resistance during inspiration and expiration predominate in chronic obstructive bronchitis with centrilobular emphysema. 3. In the presence of identical values for vital capacity and FEV1.0, arterial blood gas studies during rest and exercise provide the most reliable information on gas exchange surface and ventilation-perfusion disorders.

Airway Obstruction↗
PubMed1977

[Cheyne-Stokes respiration in chronic heart insufficiency].

1.26 of 340 patients with chronic heart failure (aortic-valve or mitral-valve disease, congestive cardiomyopathy) showed Cheyne-Stokes respiration in supine position. 2. The incidence of Cheyne-Stokes respiration in males is more than twice as high as in females with similar hemodynamic conditions. 3. Lung volumes and airway resistance did not appreciably deviate from the predicted values and are therefore of no etiologic significance. 4. Delay of the feedback between changes in the alveolar gas tensions and respiratory center caused by a prolonged circulation time (decreased cardiac index and increased central blood volume) is the predominant cause of Cheyne-Stokes breathing in patients with chronic heart failure. 5. Metabolic alkalosis (e.g. after diuretics) favors Cheyne-Stokes respiration in patients with congestive heart failure and low cardiac output, by lessening respiratory changes in pH of blood and cerebrospinal fluid.

Aged↗
PubMed1976

[Functional diagnosis of laryngeal and tracheal stenoses].

In 20 patients with upper airway obstruction in the region of the larynx and the extrathoracic and intrathoracic trachea, inspiratory and expiratory resistance, FIV1, FEV1 and total and vital capacity were determined. In patients with obstruction in the larynx and the extrathoracic trachea FIV1 is generally below FEV1. So-called "dynamic" obstruction, depending on flow and direction of flow, leads to a considerable descrepancy between FIV1 and FEV1. Impairment of respiration can be assummed if, in the adult, airway resistance during spontaneous breathing is higher than 6 cm H2O/l/sec during inspiration and/or expiration. After successful surgical correction airway resistance and FIV1 and FEV1 are restored to normal values.

Adolescent↗
PubMed1976

[Silicosis, chronic bronchitis and smoking habits].

In 333 patients suffereing from silicosis the incidence of chronic bronchitis and/or obstruction of the respiratory tract has been correlated with cigarette smoking. The incidence of chronic bronchitis and/or airway obstruction in patients who had acquired either slight or severe silicosis in Switzerland was over 50%. A positive correlation between cigarette smoking and chronic bronchitis and/or airway obstruction could be found only in younger patients with slight silicosis. Chronic bronchitis and/or airway obstruction was not more frequent in foundry-workers suffering from silicosis where they had been exposed to fumes which irritated the respiratory tract. Deformation of the respiratory tract due to silicosis has a greater bearing on the development of chronic bronchitis and airway obstruction than immoderate cigarette smoking.

Adult↗
PubMed1976

Diving at diminished atmospheric pressure: air decompression tables for different altitudes.

Fifty subjects performed 106 simulated dives at a final ambient pressure of 0.7 at (3000 m above sea level). One hundred and forty-three subjects performed 278 actual controlled dives at altitudes 900-1700 m above sea level. From the experience of these dives, air-decompression tables for altitudes 0-3200 m above sea level were calculated. Tables up to 2000 m above sea level were tested on humans under wet conditions.

Altitude↗
PubMed1975

[Proceedings: Lung lesions caused by "rare earths"].

Three reproduction photographers were found to have light patchy and reticular infiltrates on the chest x-rays. They had a 30-year history of inhaling "rare earths" and thorium deriving from the dust of the electric carbon arc-light. The diagnosis was confirmed by whole-body gamma-counting in all cases and by additional lung biopsy in one. This type of pneumoconiosis shows no definite disease progression and no serious functional deterioration.

Aged↗