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Biomedical subjects

B Jonson

Publications and source records attributed to B Jonson.

176 records · Page 10Linked to original sources
PubMedDate not supplied

Cardiorespiratory and metabolic effects of profound hypothermia.

At operation the body temperature of mechanically ventilated infants was initially decreased to 25--22 degrees C with surface cooling and further lowered to 16 degrees C by total body perfusion. During circulatory arrest, averaging 40 min, repair of complex intracardiac deformities was carried out. Rewarming to 36 degrees C was achieved by 35--65 min of total body perfusion. Of 29 infants, 23 under 10 kg survived their correction; normothermic ventilation without added CO2 was given throughout the cooling period. The following measurements were made: gas exchange, lung mechanics, heart rate, arterial pressure, right atrial pressure, cardiac output (Qt), ECG, core and nasopharyngeal temperature, as well as biochemical determinations. During surface cooling O2 consumption (VO2), CO2 production (VCO2), endtidal CO2 (PETCO2) and PaCO2 decreased proportionally and linearly with body temperature. Inspiratory resistance, total compliance, physiological dead space (VD/VT), and the single breath CO2 curve did not reveal disturbed lung function. Mean arterial pressure was 98, 90, and 70 mm Hg and heart rate was 141, 107, and 76 beat/min, at temperature 35, 30, and 25 degrees C, respectively. Cardiac index was 2.2 +/- 0.2 liter/min/m2 (mean +/- SEM, n = 25) 2 hours after surgery. Arterial lactate reached peak values of 4.1 +/- 0.3 mM/liter (n = 17), during rewarming but returned to normal. Respiratory alkalosis caused by hyperventilation during cooling caused no apparent harm. No neurological damage was observed. It is concluded that surface cooling performed with normothermic ventilation under guidance of core temperature, VO2, PETCO2, and VCO2, is a safe method.

Body Temperature↗
PubMedDate not supplied

Lung mechanics in patients undergoing mitral valve replacement. The value of monitoring of compliance and resistance.

Measurements of compliance, resistance of the respiratory system, and left atrial pressure were made before, during, and after mitral valve replacement in 30 patients. Postoperatively left atrial pressures decreased, resistance decreased and compliance increased significantly. Monitoring and recordkeeping of lung mechanics were found to be useful in predicting the feasibility for extubation and as indicators of impending disasters, e.g., due to bleeding in the thoracic cavity.

Airway Resistance↗
PubMedDate not supplied

Gas tension and pH in middle ear effusion.

The composition of gases and the gas tension in middle ear effusion in patients with serous otitis media have been investigated. By using a specially designed micro-method, very small amounts of middle ear fluid could be analyzed. The effusion was obtained by puncturing the air cells of the mastoid process. The average value of P-O2 was 41 mm Hg; Pco2 was 58 mm Hg, pH 7.24. The possible mechanism for the impaired perfusion of the mucous membranes is discussed as well as some clinical consequences.

Atmospheric Pressure↗
PubMedDate not supplied

Criteria for early extubation after intracardiac surgery in adults.

Of 142 adult patients undergoing open-heart surgery, 123 were extubated either in the operating room or within 3 hours after admission to the recovery room, to avoid the discomfort and risks of prolonged mechanical ventilation. The remaining 19 patients, who had impaired cardiac function, were mechanically ventilated for 1 to 7 days postoperatively. The most important criteria for cardiopulmonary malfunction indicating the need for continued mechnical ventilation were a low mixed venous O2 saturation (SVO2) of less than 60% and a high left atrial pressure (greater than 20 torr). Of the 123 patients, 118, had an uneventful postoperative recovery and 5 needed reintubation, 2 because of low SVO2 and 3 because of complications unrelated to respiratory management. Most adult patients can spontaneously breathe adequately immediately after or within 3 hours of completed open-heart surgery, but a thorough physiologic and clinical evaluation should precede extubation, to identify those who need prolonged mechanical ventilation in the postoperative phase. Criteria for selection of patients for early extubation are presented.

Adolescent↗
PubMedDate not supplied

Pressure-dependent variation in volume of mucosal lining of the middle ear.

A method is described for studying pressure-dependent variation in the volume of the mucosa of the middle ear. Studies were performed at different pressures in the middle ear as well as at different ambient pressures. It was found that the pressure-dependent volumetric changes of the mucosa were the same whether the pressure in the middle ear was changed directly by altering the intratympanic or indirectly by altering the ambient pressure. With the method described it is also possible to determine the middle ear volume without artefacts due to the middle ear mucosa. The volume-pressure relationship of the middle ear mucosa varied from 0.6 to 1.7 mul/cm H2O and linearly with the volume of the middle ear. Comparisons between determinations of the middle ear volume with and without consideration of the mucosal compliance showed differences, especially in small middle ears. The effect on the volume of the mucosa caused by variation of posture was also studied. The physiological middle ear pressure depends on the functional state of the Eustachian tube, the middle ear volume, the tympanic membrane and the middle ear mucosa. Thus, knowledge of the mucosa compliance is important for calculating middle ear pressure as well as for determining the volume of the air-filled middle ear space. The method might also prove a useful tool in the elucidation of the vascular bed both in health and in disease as well as the reaction of the mucosal vessels to drugs.

Atmospheric Pressure↗
PubMedDate not supplied

Rhinomanometry. I. Simple equipment.

A rhinomanometer for clinical work and research is presented. It adheres to the principle that pressure and flow should be recorded X-Y wise. A storage oscilloscope is used and the tracing pencilled down on a preprinted diagram via an oscillotracer. Anterior and posterior rhinomanometry can be performed. In the former variety, one nostril is occluded and connected to the pressure transducer by an adhesive tape. This does not deform or irritate the nasal airway. A mask for anaesthesia connects the nose to the pneumotachograph. Miniature transducers mounted on the pneumotachograph provide mechanical advantages. Simple means that allow dynamic calibration of the rhinomanometer are described. The cost to set up and operate the equipment is low.

Airway Resistance↗
PubMedDate not supplied

Monitoring of ventilation and lung mechanics during automatic ventilation. A new device.

A device that allows continuous monitoring and recording of expired minute volume, tidal volume, resistance, compliance, indices of hyperinflation and other measures of ventilation and lung mechanics during automatic ventilation is described. After connection to the ventilator (Servoventilator 900) with one cable it is operating without any calibrations or other measures. The calculation of expired minute volume is done in a new way that eliminates errors due to compression of gas in the connecting lines. Calculations of compliance is made in a way allowing measurements even in patients with hyperinflation. Expiratory and inspiratory resistance values are obtained. The indices of hyperinflation in terms of measured flow and estimated alveolar pressure at the end of an expiration are discussed. The problems and benefits associated with measurements in much obstructive patients are analyzed. A short study of the performance of the calculator is presented.

Lung Compliance↗
PubMedDate not supplied

Rhinomanometry. II. A system for numerical description of nasal airway resistance.

Various ways of expressing rhinomanometric results have been an obstacle for exchange of information. A method that could be generally accepted must: 1) easily give the clinician an informative figure describing the nasal airway patency in all cases: 2) provide a basis for statistical evaluation: and 3) allow a numerical description of the whole pressure-flow (P-V) curve. In our system P-V curves are traced X-Y wise and described with polar coordinates (angles and radii). The system can be applied in three modes. The 'clinical' mode describes resistance at a standardized condition defined by a circle of the pressure-flow diagram. Data can be read direct from the pressure-flow curve. The 'statistical' mode yields nearly normal distribution. The 'mathematical' mode describes the whole pressure-flow curve, in terms of changing angle with radius. This mode brings about good and stable curve-fitting. Calculation of properties of the total nose from data of each cavity can be done with a pocket calculator.

Adolescent↗
PubMedDate not supplied

Rhinomanometry. IV. A pre- and postoperative evaluation in functional septoplasty.

One hundred patients, subjected to functional septoplasty, were examined pre- and postoperatively with anterior rhinomanometry, questionnaire and rhinoscopy. Nasal airway resistance was described as a resistance (R2) for clinical, and as an angle of the pressure-flow curve (v2) for statistical use. Before operation uni- or bilateral R2 after mucosal decongestion was abnormally high in 72 of the patients. Regression analysis showed that patients with a preoperative R2 greater than 4.5 cmH2O/(l/sec) in at least one cavity were improved after surgery, as shown by rhinomanometry. Patients with such postoperative improvement were significantly more often satisfied and free from nasal obstruction than patients with decreased nasal patency. It is concluded that rhinomanometry is an indispensable aid in the selection of patients for functional septoplasty and for assessing the results of operation.

Adolescent↗