Biomedical subjects

C Jonmarker

Publications and source records attributed to C Jonmarker.

21 records · Page 2Linked to original sources

PubMed1985

An analyzer for in-line measurement of expiratory sulfur hexafluoride concentration.

An infrared analyzer for the inert tracer gas sulfur hexafluoride (SF6) is described and evaluated. The analyzer consists of a transducer and a processor unit. It is designed to operate in a nonrebreathing system with a ventilator and a computer. The transducer, which is placed over a cuvette with windows in the ventilator tubings, reads the SF6 concentration in the airway during the expiratory phase. At the end of the inspiratory phase, the zero level of the instrument is automatically reset. The response time and linearity of the analyzer were tested, and interference by other gases was assessed. Full response was reached within 20 ms after a sudden introduction of 0.5% SF6 into the cuvette. The analyzer-computer system had adequate linearity below 0.5% of SF6. Oxygen, nitrogen, and humid air had no influence on the analyzer signal. One hundred per cent nitrous oxide, 4% enflurane, 4% isoflurane, and 4% halothane caused signals corresponding to 0.010, 0.023, 0.022, and 0.043% SF6, respectively. Due to the method for zero reset, the importance of interference from these gases is greatly reduced when inspired and expired concentration approach each other. The disturbance from CO2 (10% CO2 gave a signal corresponding to 0.020% SF6) can be compensated for by including a CO2 analyzer in the set-up. The rapid response and the high sensitivity of the analyzer may make it useful for studies of pulmonary gas mixing and for measurements of lung volume during mechanical ventilation.

Equipment Design↗

PubMed1985

Measurement of functional residual capacity by sulfur hexafluoride washout.

Measurement of functional residual capacity (FRC) by the open-circuit multiple breath tracer gas washout technique is an established method. A system based upon washout of sulfur hexafluoride (SF6) during mechanical ventilation is described. The central unit in the system is a sensitive and rapid-response infrared SF6 analyzer. SF6 is washed in until the alveolar concentration of SF6 is 0.5%, a concentration so low that the supply of other gases is hardly influenced. During washout, the flow of SF6 from the lungs is calculated by a computer every 10 ms from signals representing expiratory flow and SF6 concentration. The total volume of SF6, washed out, is calculated by integration of SF6 flow. Since the alveolar concentration at the end of washin is known, the lung volume may be obtained. The measurement procedure is highly automated and the result is presented by the computer immediately after washout. Accurate and reproducible results in model lung tests were obtained during air and N2O/O2 ventilation. Comparison with body plethysmography (FRCBOX) in eight sitting healthy subjects gave the following: FRCSF6 = 7 ml + 0.98 X FRCBOX, r = 0.99. Comparison with nitrogen washout (FRCN2) in five postoperative patients gave the following: FRCSF6 = 59 ml + 0.97 X FRCN2, r = 0.97. FRCSF6 during N2O/O2 ventilation was the same as during air/O2 ventilation in a group of paralyzed patients. The measurement system has not been tested in patients with obstructive lung disease.

Adolescent↗

PubMedDate not supplied

Lung mechanics during upper abdominal surgery.

Functional residual capacity (FRC) and breath-by-breath compliance of the respiratory system (Crs) were studied after induction of anaesthesia, after insertion of retractors and after wound closure in patients undergoing upper abdominal surgery via a subcostal (n = 8) or a midline (n = 8) incision. After anaesthesia induction the mean FRC was 1.6 +/- 0.3 l. In the subcostal incision group FRC did not change between the studied stages, but Crs fell after retractor placement from 51 +/- 3 to 43 +/- 5 ml/cmH2O (p less than 0.01). In the midline incision group FRC rose by 21% (p less than 0.01) when the retractors were inserted, but regained outset level after wound closure. Crs in this group did not change significantly after retraction, but after closure of the wound it fell to 44 +/- 6 ml/cmH2O, i.e. less (p less than 0.05) than the outset value (52.6 ml/cmH2O). FRC thus did not decrease in either group, but Crs fell by about 15%. The authors conclude that the known difference in postoperative pulmonary complications between midline vs. subcostal incisions is not caused by the studied intraoperative events.

Adolescent↗