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Biomedical subjects

M Hochmann

Publications and source records attributed to M Hochmann.

14 recordsLinked to original sources
PubMed2003

Compensating for the effect of inlet gas temperature on heated humidifier performance.

The humidity output of heated humidifiers may be compromised by inlet gas temperatures exceeding approximately 26 degrees C, with humidity dropping below the recommended levels for intubated patients. A new version of the Fisher & Paykel MR850 humidifier claims to deal with this problem by offering a humidity compensation option. The present study tested this feature by measuring humidity output using the gravimetric method and a hygrometer at different inlet gas temperatures (16.6 degrees C to 40.0 degrees C) with compensation on and off. It was found that the compensation is effective in maintaining humidity levels despite high inlet gas temperatures.

Critical Care↗
PubMed2001

Performance of transcutaneous PCO2 and pulse oximetry monitors in newborns and infants after cardiac surgery.

We examined the effect of core and skin temperature on the accuracy of two pulse oximeters (Nellcor Symphony and Hewlett Packard saturation module, M1020A) and a transcutaneous PCO2 monitor (Fastrac Transcutaneous monitor) immediately after cardiac surgery in a group of newborns and infants. Seventy-nine sets of data were collected from 46 patients. Core temperatures ranged from 35.3 degrees C to 39.4 degrees C, skin temperatures ranged from 27.0 degrees C to 37.4 degrees C and core-skin temperature gradients ranged from 0.1 degree C to 10.1 degrees C. Data analysis consisted of comparing the difference between transcutaneous PCO2 and arterial PCO2 and the differences between oxygen haemoglobin saturation measured by both pulse oximeters and oxygen haemoglobin saturation measured by co-oximeter to core temperature, skin temperature and core-skin temperature gradients. The mean differences +/- standard deviations and limits of agreement for transcutaneous PCO2 and oxygen haemoglobin saturation measured by the Hewlett Packard and Nellcor pulse oximeters were 0.95 +/- 4.10 mmHg (-7.09 mmHg to 8.99 mmHg), -1.07 +/- 1.84% (-4.68% to 2.54%) and -1.23 +/- 2.23% (-5.60% to 3.14%) respectively. Analysis of correlation coefficients showed that the accuracy of the transcutaneous PCO2 monitor and the pulse oximeters were not affected by core temperature, skin temperature or core-skin temperature gradient in the ranges encountered. We therefore conclude that these devices are acceptably accurate and suitable for use in infants when core and skin temperatures and core-skin temperature gradient are in the range normally found after cardiac surgery.

Blood Gas Monitoring, Transcutaneous↗
PubMed2001

An evaluation of nitric oxide and nitrogen dioxide absorbers and filters.

The absorbance of NO (5-90 ppm) and NO2 (0.5-4 ppm) by a number of absorbers and filters was assessed via bench testing. All absorbers (Sodasorb, Purafil CP, Purafil Select, Sofnolime, Sofnofil and 50/50 mix of Sofnolime/Sofnofil) except Sodasorb absorbed NO almost completely. Only Sofnolime absorbed NO2 completely while Sodasorb and the Sofnolime/Sofnofil 50/50 mix had absorbances between 47% and 90%. The absorbance of four filters (ILF100, ILF150, ILF200 and HgCONO) as well as Sofnolime and the Sofnolime/Sofnofil 50/50 mix was tested in the expiratory port of a Servo 900C ventilator All absorbers and filters produced a change in ventilator pressures. The HgCONO filter Sofnolime and the Sofnolime/Sofnofil 50/50 mix all absorbed NO. At 80 ppm NO, the HgCONO filter had 100% absorbance for four hours while Sofnolime's absorbance was significantly reduced after one hour. All filters and absorbers tested on the ventilator except the Sofnolime/Sofnofil 50/50 mix and the ILF150 filter absorbed NO2 completely for a period ranging from 90 minutes to four hours. We recommend the HgCONO filter and Sofnolime to absorb both NO and NO2. If absorption of NO2 only is required we recommend the HgCONO, ILF100 or ILF200 filters or the Sofnolime absorber.

Absorption↗
PubMed1998

Accuracy of two pulse oximeters at low arterial hemoglobin-oxygen saturation.

OBJECTIVE: To evaluate the performance of two pulse oximeters in the measurement of arterial hemoglobin saturation in hypoxemic children. DESIGN: Prospective, repeated-measures observational study. SETTING: A 16-bed pediatric intensive care unit in a children's tertiary hospital. PATIENTS: Sixty-six patients with arterial saturation of <90%. INTERVENTIONS: Three arterial blood samples were taken from each subject during a 48-hr period. Pulse oximeter measurements of arterial saturation were compared with arterial saturation determined by cooximetry. MEASUREMENTS AND MAIN RESULTS: Arterial saturation was measured using one or both pulse oximeters (SpO2) and compared with the arterial hemoglobin saturation determined by cooximetry (SaO2). Sixty-two subjects were studied, using the Ohmeda pulse oximeter giving 185 data points (78 with saturations <75% [defined by the average of pulse oximeter and cooximeter]); 53 subjects were studied, using the Hewlett-Packard pulse oximeter yielding 155 data points (60 with saturations <75%). SpO2 ranged from 24% to 94%. Bias and precision of the Ohmeda pulse oximeter were -2.8% and 4.8% >75% and -0.8% and 8.0% <75%. Bias and precision of the Hewlett-Packard pulse oximeter were -0.5% and 5.1% >75% and 0.4% and 4.6% <75%. Intrapatient regression coefficient (r) for the differences between pulse oximeter and cooximeter was 0.58 for the Ohmeda and 0.59 for the Hewlett-Packard. Regression coefficients for predicting change in cooximeter value given a change in the Ohmeda pulse oximeter were 0.59 and 0.71 <75% and >75%, respectively. Similar coefficients for the Hewlett-Packard pulse oximeter were 0.50 and 0.70, respectively. CONCLUSION: The performance of the Ohmeda pulse oximeter deteriorated below an SpO2 of 75%. The Hewlett-Packard pulse oximeter performed consistently above and below an SpO2 of 75%. The ability of both pulse oximeters to reliably predict change in SaO2 based on change in pulse oximetry was limited. We recommend measurement of PaO2 or SaO2 for important clinical decisions.

Child↗
PubMed1998

An evaluation of a new analyser for inhaled nitric oxide administration.

We examined the ability of a new combined nitric oxide (NO)/nitrogen dioxide (NO2) electrochemical analyser (PrinterNOx, Micro Medical Limited, Chatham, Kent, England) to measure NO and NO2 concentrations. The PrinterNOx was compared to a chemiluminescence analyser (42H, Thermo Environmental Instruments Inc, Franklin MA, U.S.A.). NO and NO2 were generated in a standard ventilator circuit using a paediatric ventilator (900C, Siemens Elema, Sweden) connected to an artificial lung (260li, TTL Test Lung, Michigan Instruments, MI, U.S.A.). Forty-four paired NO measurements ranging from 2.56 ppm to 74.6 ppm and 50 paired NO2 measurements ranging from 0.0 ppm to 5.39 ppm were obtained. For the measurement of NO the PrinterNOx showed a tendency to overestimate the chemiluminescence analyser. Regression analysis showed a close relationship between the two analysers with r2 = 0.9981 and a regression equation of y = 1.1658 x +0.0197. In the more clinically important range of 0-25 ppm, r2 increased to 0.9996 with a regression equation of y = 1.1984 x -0.4657. Conversely the PrinterNOx underestimated the chemiluminescence analyser for the measurement of NO2. The regression equation describing this relationship was y = 0.879 x -0.0447 (r2 = 0.9993). We conclude that the PrinterNOx is of sufficient accuracy to be of clinical use in the administration of NO.

Anesthesiology↗
PubMed1995

High frequency oscillation in newborn infants with respiratory failure.

OBJECTIVE: To report ventilation strategies, survival and complications in 39 outborn infants treated with high frequency oscillatory ventilation (HFOV). METHODOLOGY: Data were collected prospectively between 1 May 1992 and 31 December 1993 on all infants treated with HFOV who had severe respiratory failure despite optimal conventional ventilation. RESULTS: Twenty-eight out of 39 (72%) survived. Of the 15 infants with birthweights < 1500 g, eight survived. Best survival rates were for infants with pulmonary interstitial emphysema with air leak (4/5) and for infants of birthweight > 1500 g with hyaline membrane disease (8/8), and meconium aspiration syndrome (7/7). Three infants deteriorated while on HFOV and required extracorporeal membrane oxygenation. Complications were: (i) development of pulmonary interstitial emphysema (1); (ii) recurrence of pneumothorax (3); (iii) hypotension (2); and (iv) bronchopulmonary dysplasia (9). One of the eight infants weighing < 1500 g who received HFOV in the first week of life developed periventricular haemorrhage. CONCLUSION: The initial results of HFOV for severe failure were encouraging although a learning curve was encountered with its introduction.

High-Frequency Ventilation↗
PubMed1995

High frequency oscillatory ventilation: initial experience in 22 patients.

OBJECTIVES: To report the outcome of a consecutive cohort of neonates treated with high frequency oscillatory ventilation (HFOV). METHODOLOGY: Prospective cohort study of 22 neonates failing conventional mechanical ventilation (CMV) between October 1992 and August 1993. Outcomes evaluated were in-hospital survival rate, comorbidities including patent ductus arteriosus (PDA), cerebroventricular haemorrhages (CVH), necrotizing enterocolitis (NEC), bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP), and acute changes in respiratory status. RESULTS: Eighteen of 22 (81.8%) survived. Of the four children who died, one did not respond to HFOV and died within 24 h of treatment. Two died of respiratory failure complicated by pulmonary haemorrhage. The remaining infant responded to HFOV but later developed severe NEC while on minimal CMV and died at 2 weeks of age. Three subjects were > or = 34 weeks' gestation; each responded well to HFOV with no substantial comorbidity. Of the remaining 19 infants < 34 weeks' gestation, six (31.6%) had a PDA, and seven (36.8%) had a CVH. One infant developed cystic periventricular leucomalacia. Three infants (15.8%) had NEC. Respiratory failure in the 15 survivors with gestational ages < 34 weeks improved dramatically with HFOV. Ten (66.7%) survivors < 34 weeks developed BPD and 10 (66.7%) ROP. CONCLUSION: High frequency oscillatory ventilation was associated with a survival rate of 81.8%, but with significant comorbidity.

Barotrauma↗
PubMed1995

A comparison of two transcutaneous monitors for the measurement of arterial PO2 and PCO2 in neonates.

We examined the ability of two transcutaneous devices (Fastrac, Sensormedics Corporation, Yorba Linda, California, U.S.A. and Hewlett Packard M1018A, Hewlett Packard Component Monitoring System, Hewlett Packard, North Hollywood, U.S.A.) to measure arterial PCO2 and PO2 in neonates. Thirty-seven neonates had transcutaneous oxygen measured with the Hewlett Packard (HPO2 group), 38 neonates had transcutaneous carbon dioxide measured with the Hewlett Packard (HPCO2 group) and the Fastrac was used on 27 neonates (FTCO2 group). Both devices were operated with electrode temperatures of 43.5 degrees C although an additional ten subjects were studied using the Fastrac with an electrode temperature of 43.0 degrees C. The mean differences (transcutaneous--arterial) and upper and lower limits of agreement were calculated for each group. For the HPO2 group they were 3.78 mmHg (-12.23 to 19.80 mmHg), for the HPCO2 group they were 0.40 mmHg (-4.50 to 5.30 mmHg) and for the FTCO2 they were -0.96 mmHg (-7.85 to 5.92 mmHg). For the Fastrac group at an electrode temperature of 43.0 degrees C the mean difference and limits of agreement were -1.00 mmHg and -4.58 mmHg to 2.58 mmHg. The average sensitivity and specificity for both machines for the detection of hypocarbia were 82% and 92% respectively while for hypercarbia they were 90% and 94% respectively. For hypoxaemia, the sensitivity and specificity were 40% and 94% while for hyperoxaemia the sensitivity and specificity were 83% and 97%. We conclude that both machines provide a useful supplement to arterial PCO2 measurements and the Fastrac performs better at 43.0 degrees C. The measurement of PO2 is less accurate but is still of clinical use.

Blood Gas Monitoring, Transcutaneous↗
PubMed1994

A comparison of syringes to collect blood for analysis of gases, electrolytes and glucose.

We studied the interchangeability of two blood gas syringes (Johns, Hardie Health Care Products Pty Ltd and Marksman, Martell Medical Products Inc) for the collection of blood for the analysis of PCO2, PO2, pH, sodium, potassium and glucose in 71 intensive care unit patients. The interchangeability of these two syringes with a specially designed syringe (Radiometer, Radiometer A/S) for the collection of blood for the analysis of ionized calcium was also studied. Analysis of pH, sodium, potassium and glucose showed no clinically significant differences between samples collected with Johns and Marksman syringes. However, differences in PCO2 and PO2 in samples collected with these syringes may be clinically significant if the PO2 is less than 100 mmHg. There were no clinically significant differences in ionized calcium levels in blood samples collected with Johns, Marksman and Radiometer syringes. We conclude that Johns and Marksman syringes are interchangeable for the collection of blood for the analysis of PCO2, PO2, pH, sodium, potassium and glucose and they are also interchangeable with Radiometer syringes for the collection of blood for ionized calcium analysis.

Adolescent↗
PubMed1993

An alarm for monitoring CPAP.

We have built a device for use within the hospital and at home that is designed to warn of circuit disconnection when used in conjunction with continuous positive airway pressure (CPAP) therapy delivered via ventilators or CPAP generating systems. The Royal Children's Hospital CPAP alarm is a compact, battery operated alarm and monitor of circuit pressure. The device includes intrinsic safety features including a safety blow-off valve, a high pressure alarm and design features that make the device practical, safe and easy to use by both trained hospital personnel and home care attendants with limited training.

Equipment Design↗
PubMed1993

An appraisal of techniques for administration of gaseous nitric oxide.

Gaseous nitric oxide (NO) is a potent selective pulmonary vasodilator. When mixed with O2 for more than 10-15 minutes it forms toxic amounts of nitrogen dioxide (NO2). We describe two techniques to administer 20 parts per million (ppm) during mechanical ventilation. A technique using flows of NO and O2 at low pressure to drive a Siemens Servo 900C ventilator provided a constant inspired concentration of NO. Another technique in which NO was added to the inspiratory limb of a Siemens Servo 900C ventilator driven by high pressure oxygen provided a highly variable concentration (9-53 ppm) of inspired NO.

Anesthesia, Inhalation↗
PubMed1992

Accuracy of the BoMED NCCOM3 bioimpedance cardiac output monitor during induced hypotension: an experimental study in dogs.

Changes in thoracic electrical bioimpedance during the cardiac cycle are utilised by the BoMed NCCOM3 monitor to measure cardiac output (COTEB). The technique provides a continuous noninvasive measurement but it has not been widely accepted. To determine the accuracy of the monitor, we compared its measurement with cardiac output measured by dye dilution (CODD) during induced hypotension and recovery in 23 dogs. After calibration of the NCCOM3 monitor during a resting state in each dog [mean blood pressure 112 +/- 17 (SD), mean CODD 3.22 +/- 0.99 l/min], the mean difference (COTEB-CODD) between paired measurements at the nadir of hypotension (blood pressure 55 +/- 24 mmHg) was 0.29 +/- 0.47 l/min whose limits of agreement (mean difference +/- 2 SD) were + 111.8% and -59.1% of the mean hypotensive CODD (1.10 +/- 0.66 l/min). Upon recovery from hypotension (mean blood pressure 102 +/- 20 mmHg), the mean difference between paired measurements was -0.28 +/- 0.66 l/min, whose limits of agreement were +44.1% and -67.8% of the mean CODD (2.36 +/- 1.01 l/min). The mean difference between the two techniques is too variable and excessive to permit substitution of one technique for the other. These results do not support the accuracy and reliability of the BoMed NCCOM3 cardiac output monitor.

Animals↗
PubMed1991

Epidural fentanyl effect on cardiac output and hepatic blood flow.

Epidural opioids provide high quality analgesia with no clinically apparent effect on the circulation or on specific organ blood flow. Little investigative data is available to support these impressions of circulatory stability. Ten patients presenting for thoracotomy were studied at rest preoperatively to determine if epidural fentanyl had any effect on the systemic circulation or hepatic blood flow. Intravascular pressure measurements, cardiac output estimation using the dye-dilution technique and estimation of altered hepatic blood flow by measuring the clearance of indocyanine green were performed. No significant changes in heart rate, perfusion pressure, cardiac output or hepatic blood flow were detected following the administration of fentanyl 50 micrograms into the epidural space.

Analgesia, Epidural↗