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Biomedical subjects

A Versprille

Publications and source records attributed to A Versprille.

At least 19 recordsLinked to original sources
PubMed2005

Combined biological and physico-chemical treatment of baker's yeast wastewater.

The UASB reactor (35 degrees C) was quite efficient for removal of bulk COD (52-74%) from the raw and diluted cultivation medium from the first separation process of baker's yeasts (the average organic loading rates varied in the range 3.7-16 g COD/I/d). The aerobic-anoxic biofilter (19-23 degrees C) can be used for removal of remaining BOD and ammonia from anaerobic effluents; however, it had insufficient COD to fulfil the denitrification requirements. To balance COD/N ratio, some bypass of raw wastewater (approximately 10%) should be added to the biofilter feed. The application of iron (III)-, aluminium- or calcium-induced coagulation for post-treatment of aerobic effluents can fulfil the limits for discharge to sewerage (even for colour mainly exerted by hardly biodegradable melanoidins), however, the required amounts of coagulants were relatively high.

Aluminum↗
PubMed2001

Reduction of oscillatory pressure along the endotracheal tube is indicative for maximal respiratory compliance during high-frequency oscillatory ventilation: a mathematical model study.

We hypothesized that during high-frequency oscillatory ventilation (HFOV), a reduction of peak-to-peak oscillatory pressure along the endotracheal tube is maximal when respiratory system compliance is maximal. We made a mathematical model of the endotracheal tube and the respiratory system of a neonate suffering from idiopathic respiratory distress syndrome (IRDS). The model consisted of linear viscous and inertive elements, a non-linear endotracheal tube resistance, and a non-linear compliance allowing for alveolar recruitment and overdistention. Respiratory compliance was maximal at the transition between maximal recruitment and minimal overdistention. A new variable, the oscillatory pressure ratio (OPR), was defined as the ratio between peak-to-peak oscillatory pressures at the distal end and the proximal opening of the endotracheal tube, respectively. The respiratory variables of four patients were fed into the model, and the relationship between respiratory system compliance and OPR was determined. OPR decreased as compliance increased, except for very low compliances below where 0.08 mL. cm H2O(-1), and OPR increased with increasing compliance. The relationship between mean airway pressure P(aw) and OPR revealed that the minimal OPR (range, 0.37-0.78) and maximal respiratory compliance coincided at the same P(aw). However, the relationship did depend on oscillation frequency, applied oscillatory pressure, and endotracheal tube resistance, parameters that may change during clinical application of HFOV. When 81 permutations of nominal and extreme respiratory variables were used in the model, the minimum OPR (0.60 +/- 0.23) and maximum compliance coincided in all cases. These model experiments support our hypothesis. The results indicate that the OPR may be a useful index to optimize lung expansion, where lung recruitment is maximal and overdistention minimal. In vivo tests will be needed to reveal the feasibility and reliability of such an index for biomedical and clinical application.

Airway Resistance↗
PubMed2001

A new approach to mechanical simulation of lung behaviour: pressure-controlled and time-related piston movement.

A mechanical lung simulator is described (an extension of a previous mechanical simulator) which simulates normal breathing and artificial ventilation in patients. The extended integration of hardware and software offers many new possibilities and advantages over the former simulator. The properties of components which simulate elastance and airway resistance of the lung are defined in software rather than by the mechanical properties of the components alone. Therefore, a more flexible simulation of non-linear behaviour and the cross-over effects of lung properties is obtained. Furthermore, the range of lung compliance is extended to simulate patients with emphysema. The dependency of airway resistance on lung recoil pressure and transmural pressure of the airways can also be simulated. The new approach enables one to incorporate time-related mechanics such as the influence of lung viscosity or cardiac oscillation. The different relations defined in the software can be changed from breath to breath. Three simulations are presented: (1) computer-controlled expiration in the artificially ventilated lung; (2) simulation of normal breathing; and (3) simulation of viscoelastance and cardiac influences during artificial ventilation. The mechanical simulator provides a reproducible and flexible environment for testing new software and equipment in the lung function laboratory and in intensive care, and can be used for instruction and training.

Biomechanical Phenomena↗
PubMed2000

Evaluation of diffusing capacity in patients with a restrictive lung disease.

BACKGROUND: In healthy volunteers, the single-breath diffusing capacity of the lung for carbon monoxide (DLCO) decreases and DLCO normalized per liter alveolar volume (VA; DLCO/VA) increases if VA is decreased. We hypothesized that comparison of DLCO/VA with its predicted value at predicted total lung capacity (TLC) will result in an underestimation of the diffusion disorder in patients with a restrictive lung disease, if a similar relationship exists between DLCO/VA and lung volume as found in healthy volunteers. OBJECTIVE: To test this hypothesis, we studied total gas transfer DLCO and DLCO/VA as functions of VA in patients who developed a restrictive lung disease and a diffusion disorder in a short period of time. DESIGN: An observational survey. SETTING: Pulmonary function department. PATIENTS: Thirteen patients without any initial pulmonary pathology who developed the mentioned pulmonary pathology due to bleomycin treatment. INTERVENTIONS: Bleomycin treatment. MEASUREMENTS AND RESULTS: We performed the single-breath test at various VA levels before, during, and after bleomycin treatment. In the majority of the patients, the DLCO vs VA relationship remained parabolic, but shifted downwards during therapy. Therefore, the linear DLCO/VA vs VA relationship shifted downwards, while the negative slope was not changed, indicating the development of a decreased gas transfer. Six patients also developed a volume restriction. CONCLUSIONS: The agreement of the data with the hypothesis increased its probability. Consequently, to evaluate a diffusion disorder, DLCO/VA at a lower actual TLC of patients with a lung restriction should be compared to a reference DLCO/VA at a lung volume equal to the actual TLC.

Adult↗
PubMed1999

Computer-controlled flow resistance.

A computer-controlled flow resistance (CCR), to be used in a computer-controlled lung model, is presented. Flow is forced through a slit between a cylinder and a sleeve around the cylinder. The resulting flow resistance depends on the width, circumferences and the variable length of the slit. The variation in the length is computer-controlled by the position of the sleeve with respect to the cylinder. The total flow resistance also depends on inlet and outlet resistance at both sides of the slit and on flow. The dependence on flow is primarily due to the shape of the inlet of the slit. The resistance of the slit itself is almost independent of flow. The resistance is calculated during a calibration phase at different positions of the sleeve, for flow values from 0.05 to 1.0 litre.s-1 (inflow) and from -0.05 to -1.0 litre.s-1 (outflow). To simulate a required resistance pattern, as, for instance, will occur during breathing, at each moment the set position of the sleeve is calculated by means of an interpolation from the relationship between flow resistance and position of the sleeve. The internal diameter of the sleeve is fixed. To tune the resistance range for a specific simulation, the cylinder is changed for one with different diameter, changing the width of the slit.

Airway Resistance↗
PubMed1998

The compliance of the porcine pulmonary artery depends on pressure and heart rate.

1. The influence of mean pulmonary arterial pressure (mean Ppa) on dynamic (Cd) and pseudo-static compliance (Cps) of the pulmonary artery was studied at a constant and a changing heart rate. Cd is the change in cross-sectional area (CSA) relative to the change in Ppa throughout a heart cycle. Cps is the change in mean CSA relative to the change in mean Ppa. If Cd is known, pulmonary blood flow can be computed from the Ppa using a windkessel model. We investigated whether Cps can be interchanged with Cd. 2. In nine anaesthetized pigs, we determined the mean CSA and Cd of the pulmonary artery at various Ppa levels, ranging from approximately 30 to 10 mmHg, established by bleeding. Two series of measurements were carried out, one series at a spontaneously changing heart rate (n = 9) and one series at a constant heart rate (n = 6). To determine CSA a conductance method was used. 3. Cps depended on pressure. The mean CSA versus mean Ppa curves were sigmoid and steepest in the series with the increasing heart rate (established by bleeding). The CSA versus Ppa loop during a heart cycle, giving Cd, was approximately linear and almost closed. The Cd versus mean Ppa relationship was bell shaped. Its width was smaller if the heart rate increased during the series of measurements. The pressure, where Cd was maximum, was higher at higher heart rates. Furthermore, the maximum Cd was not affected by the heart rate. 4. Because the pulmonary artery constricts with increasing heart rate, Cps will be overestimated during procedures where heart rate increases. Cd should be determined on a beat-to-beat basis to calculate flow because it changes with mean pulmonary arterial pressure and heart rate.

Algorithms↗
PubMed1998

A rebreathing method to determine carbon monoxide diffusing capacity in children: reference values for 6- to 18-year-olds [corrected] and validation in adult volunteers.

The diffusing capacity of carbon monoxide (D(L,CO)) and its value normalized to alveolar volume (D(L,CO)/V(A)) are usually estimated with the single breath method at total lung capacity (TLC). Severely ill patients and small children are not able to deliver a satisfactory vital capacity (VC) or hold their breath for 10 s at TLC. The aim of this study was to develop a rebreathing procedure in which diffusing capacity can be determined during spontaneous tidal breathing. The conventional rebreathing method during hyperventilation was modified so that rebreathing volume and gas concentrations were kept constant by CO2 absorption and O2 supplementation. In adult healthy volunteers and in patients who were able to perform both tests, the diffusion indices obtained with this rebreathing method during resting ventilation were compared with those obtained by the single breath method. Predicted (reference) values for rebreathing D(L,CO) and D(L,CO)/V(A) for children were determined. D(L,CO)/V(A) decreased with alveolar volume (V(A)) and increased with alveolar ventilation (V'(A)). In adults at V'(A) above 35 L x min(-1) rebreathing D(L,CO)/V(A) was similar to single breath D(L,CO)/V(A) at similar alveolar volumes. The D(L,CO)/V(A) relative to their corresponding reference values were the same for both methods in adult patients, irrespective of ventilation distribution disturbances. In children the newly described diffusing capacity obtained by the rebreathing method during resting ventilation can serve as a valuable index to assess and follow a diffusion disorder.

Absorption↗
PubMed1998

Tracing best PEEP by applying PEEP as a RAMP.

OBJECTIVE: The aim of this study was to show the feasibility of a slow, continuously increasing level of positive end-expiratory pressure (PEEP) (ramp manoeuvre) in selecting best PEEP and to evaluate whether best PEEP, as defined by maximal oxygen transport, coincides with best systemic arterial oxygenation or best compliance. DESIGN: In 11 anaesthetized piglets, PEEP was increased between 0 cmH2O (zero end-expiratory pressure; ZEEP) and 15 cmH2O (PEEP15) with a constant rate of 0.67 cmH2O x min(-1). This ramp manoeuvre was performed both under normal conditions and after induction of an experimental lung oedema. During the ramp manoeuvre, haemodynamic and pulmonary variables were monitored almost continuously. RESULTS: During the rise in PEEP, cardiac output declined in a non-linear way. In the series with normal conditions, best PEEP was always found at ZEEP. In the series with experimental lung oedema, best PEEP, as defined by maximum oxygen transport, was found at PEEP1-6, as defined by maximal compliance, at PEEP7.5 and by maximal arterial oxygen tension (PaO2) at PEEP10-14. CONCLUSIONS: Best PEEP according to oxygen transport is lower than best PEEP according to compliance and PaO2; the use of PEEP as a ramp might prevent unnecessarily high levels of PEEP.

Animals↗
PubMed1997

Components of carbon monoxide transfer at different alveolar volumes during mechanical ventilation in pigs.

We studied the effect of increasing alveolar volume on pulmonary carbon monoxide transfer (DLCO) and its components, i.e. membrane diffusing capacity (DM) and capillary blood volume (Qc), during mechanical ventilation in eight anaesthetized and paralysed healthy pigs (mean weight 11.2 kg). We used an inspiratory pause procedure for simulation of the single-breath technique, and inflated 15, 20, 25 and 30 ml kg-1 in random order. DM and Qc were derived using the Roughton-Forster equation. Per litre BTPS increase in effective VA, DLCO (inspiratory oxygen fraction 0.30) decreased on average by 11.8 mumol s-1 kPa-1, DM slightly increased by 2.7 mumol s-1 kPa-1 and Qc decreased by 241 ml. The increase in DM was much smaller than might be expected from the increase in VA, which we ascribe to a loss of the alveolar capillary membrane for gas transfer because of the concomitant decrease in Qc. The decrease in Qc may be explained by a squeezing effect of the intrapulmonary pressure rise on the alveolar wall and by stretching of lung tissue.

Animals↗
PubMed1996

Pulmonary diffusing capacity at reduced alveolar volumes in children.

The diffusing capacity, when normalized per liter of alveolar volume (DL,CO/VA) decreases in normal adults, whereas their total diffusing capacity (DL,CO) increases as alveolar volume (VA) increases. We studied these relationships in a group of normal children below 20 years of age. Diffusion variables were determined using the single breath technique. The effects of sex, age, and height on these relationships were estimated. DL,CO increased and DL,CO/VA decreased as alveolar volume increased. DL,CO and DL,CO/VA reference values at total lung capacity (TLC) appeared to be comparable to reference values at TLC in the literature. Reference values of DL,CO and DL,CO/VA derived from measurements at various alveolar volumes also predict similar values at TLC. The advantage of our reference equations is their applicability to patients with restrictive lung disease. Actual DL,CO/VA can be compared with reference DL,CO/VA at actual (restrictive) TLC instead of reference DL,CO/VA at reference TLC. This comparison extends the evaluation of a diffusion disorder.

Adolescent↗
PubMed1996

Cross-talk between the lungs in piglets.

HYPOTHESIS: During alternating ventilation (AV) (i.e. differential ventilation (DV) of both lungs with a phase difference of half a ventilatory cycle) volume expansion of the inflated lung will occur partly by compression of the opposite lung. OBJECTIVE: We studied whether and how large an undulating flow would occur out of and into the non-ventilated lung during unilateral ventilation. DESIGN: In 20 anaesthetized, paralysed piglets (11.0 +/- 1.0 kg) DV was applied at a rate of 10 breaths per minute (bpm). In 6 animals, 15 and 20 bpm were also applied with the tidal volume adapted no normocapnia. As the measure of interaction (cross-talk) served the volume change in the non-ventilated lung, found by integration of the low signal, in percentage of the tidal volume to the other lung. RESULTS: In all pigs, tidal volume to the left lung. (VT,l = 7.33 +/- 1.06 ml kg-1) caused a volume change in the right lung of about 21% of VT,l at 10 bpm. The right-to-left cross-talk was significantly lower and about 15% of VT,r (9.07 +/- 1.21 ml kg-1). At higher ventilatory rates, the l-to-r and the r-to-l cross-talk did not change. CONCLUSION: During unilateral ventilation, volume expansion of the inflated lung occurs partly by compression of the opposite lung. The lower mean lung volume during AV compared to synchronous differential ventilation can be explained by such compression. The mechanism of compression is similar at different ventilatory rates.

Animals↗
PubMed1996

A stable model of respiratory distress by small injections of oleic acid in pigs.

OBJECTIVE: Development of a stable model of respiratory distress in pigs with oleic acid, fulfilling clinical criteria of the adult respiratory distress syndrome (ARDS). DESIGN: Eight pigs (9.1 +/- 0.7 kg) were anesthetized with pentobarbital, paralyzed with tubocurarine and mechanically ventilated with an FIO2 of 0.6, an I:E ratio of 2:3 and a PEEP of 0.2 kPa. Oleic acid (dissolved 1:1 in 96% alcohol) was administered in a series of multiple injections of 0.1 ml until PaO2 was lower than 8 kPa. MEASUREMENTS AND RESULTS: Careful titration of the oleic acid injections on guidance of the PaO2 established a reproducible respiratory distress (PaO2 = 7.3 +/- 0.8 kPa), in which gas exchange and hemodynamic variables were stable for at least 4 h. The number of oleic acid injections (22 +/- 11, mean and SD) varied between the animals. CONCLUSIONS: With the use of multiple injections of oleic acid, a stable model of early respiratory distress in pigs can be achieved, in spite of individual differences in sensitivity. Such a stable model allows for a diversity of studies on early respiratory distress.

Animals↗
PubMed1996

Haemodynamic and respiratory conditions during alternating and synchronous ventilation of both lungs.

OBJECTIVE: We tested the hypothesis that mean thoracic expansion (and mean lung volume) is lower during alternating ventilation (AV), i.e. ventilation of both lungs with a phase shift of half a ventilatory cycle, compared to synchronous ventilation (SV) of both lungs. As a consequence, intrathoracic pressure will be lower, causing lower, central venous pressure and higher cardiac output. DESIGN: In eight anaesthetized and paralysed piglets, differential ventilation was established by fixation of an endobronchial tube in the left main bronchus. SV and AV were sequentially applied for four and three periods, respectively, of 10 minutes each. Minute ventilation was the same during AV and SV and adapted to normocapnia. Two series of observations were performed: series 1 with intact thorax and monitoring of oesophageal pressure; series 2 after perforation of the sternum, airtight closure of the thorax and monitoring of pericardial pressure. RESULTS: In both series, mean lung volume was 16 +/- 4% lower and central venous, oesophageal (series 1) and pericardial pressures (series 2) were 0.5-0.7 mmHg lower during AV compared to SV (all p < 0.001). In series 1, aortic pressure was 5 mmHg and cardiac output 8% higher (both p < 0.001). In series 2, cardiac output was 5% higher during AV (p < 0.001), but aortic pressure did not change (p = 0.07). CONCLUSION: Our data verified the hypothesis. The lower oesophageal (series 1), pericardial (series 2) and central venous pressures during AV compared to SV could be explained by the smaller thoracic expansion due to the lower mean lung volume, which was attributed to compression of the opposite lung by the, expansion of the inflated lung.

Animals↗
PubMed1996

Effects of endotoxin infusion on mean systemic filling pressure and flow resistance to venous return.

Mean systemic filling pressure (Psf) is an indicator of the filling state of the systemic circulation. Cardiac output (Q') is related linearly to the difference between Psf and central venous pressure (Pcv), according to: Q' = (Psf - Pcv)/Rsf, where Rsf is the flow resistance downstream from the sites where blood pressure is equal to Psf. In 16 anaesthetized pigs we evaluated Psf, Rsf and Q' during baseline conditions, continuous endotoxin infusion and after subsequent fluid loading. Psf and Rsf were determined from simultaneous measurements of Q' and Pcv at seven levels of lung inflation. The following results were obtained. Psf was 8.1 +/- 1.8 mm Hg (mean +/- SD) during baseline conditions, increased after endotoxin infusion to 9.9 +/- 3.2 mm Hg (P = 0.04) and remained the same after infusion of 18 ml kg-1 of Ringer s lactate. Rsf increased from 0.34 +/- 0.07 to 0.80 +/- 0.34 mm Hg ml-1 s by endotoxin and decreased after fluid infusion to 0.58 +/- 0.14. Q' changed inversely proportional to Rsf (P = 0.001). Rsf changes were highly correlated with the changes in total systemic flow resistance (Rs) (P < 0.001). Endotoxin caused haemoconcentration and a decrease in plasma volume. The stability of Psf during endotoxin infusion and after volume loading indicate that the stressed volume was well maintained and changes in blood volume are compensated by changes in non-stressed volume. The increase in Rsf can be attributed to arteriolar vasoconstriction, venous vasoconstriction and haemoconcentration.

Animals↗
PubMed1996

Systemic filling pressure in the intact circulation determined with a slow inflation procedure.

In eight mechanically ventilated, anaesthetized pigs weighing 10.3 +/- 0.8 kg (mean +/- SD) we studied the effect of the inflation time of the lung on the estimation of the mean systemic filling pressure (Psf) from the changes in venous return and central venous pressure during inflation of the lung. For this purpose we applied slow inflation procedures (SIP) to the lung with inflation times of 2.4, 4.8, 7.2, 9.6 and 12 s at tidal volumes (VT) of 15 and 30 ml/kg. The data were compared with the values of Psf obtained from inspiratory pause procedures (IPPs). A linear regression between venous return and central venous pressure applied during a SIP underestimated Psf compared with the value obtained with IPPs. An exponential fit through the values of Psf obtained from the different SIPs predicted an inflation time of about 15 s for an estimation of Psf that is not different from the Psf (IPP). The advantage of the SIP method is that the Psf can be determined much faster than with the method based on IPPs. However, due to the rather long inflation time needed, the method may be only applicable under circumstances where neurohumoral control mechanisms are suppressed as during intensive care and anaesthesia.

Anesthesia↗
PubMed1996

Determination of the mean cross-sectional area of the thoracic aorta using a double indicator dilution technique.

A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same "cold" (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSAGD), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSAGD = -1.83 + 1.06 . CSAIVUS, r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average -0.99 mm2 +/- 2.64 mm2 (mean CSAGD = 46.84 +/- 8.21 mm2, mean CSAIVUS = 47.82 +/- 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo.

Anatomy, Cross-Sectional↗