Biomedical subjects

Andreas Schibler

Publications and source records attributed to Andreas Schibler.

8 recordsLinked to original sources

PubMed2006

Electrical impedance tomography in extremely prematurely born infants and during high frequency oscillatory ventilation analyzed in the frequency domain.

Functional electrical impedance tomography (EIT) measures relative impedance change that occurs in the chest during a distinct observation period and an EIT image describing regional relative impedance change is generated. Analysis of such an EIT image may be erroneous because it is based on an impedance signal that has several components. Most of the change in relative impedance in the chest is caused by air movement but other physiological events such as cardiac activity change in end expiratory level or pressure swings originating from a ventilator circuit can influence the impedance signal. We obtained EIT images and signals in spontaneously breathing healthy adults, in extremely prematurely born infants on continuous positive airway pressure and in ventilated sheep on conventional mechanical or high frequency oscillatory ventilation (HFOV). Data were analyzed in the frequency domain and results presented after band pass filtering within the frequency range of the physiological event of interest. Band pass filtering of EIT data is necessary in premature infants and on HFOV to differentiate and eliminate relative impedance changes caused by physiological events other than the one of interest.

Adult↗

PubMed2006

Physiological consequences of early-life insult.

The most commonly observed severe lung injuries in early life are the respiratory distress syndrome in premature infants and the acute respiratory distress syndrome in children. Both diseases are characterised by alveolar instability, fluid filled airspace and some degree of airway obstruction. In the acute phase, collapsed alveoli can be reopened with positive end-expiratory pressure and lung recruitment. New insight into the physiology of lung recruitment suggests that the shape of the pressure-volume curve is defined by the change in rate of alveolar opening and closing. Reduced lung volumes and severe ventilation maldistribution are found in the acute phase but may persist during childhood. Any severe lung injury in this early phase of life can cause significant structural and functional damage to the developing lung. Follow-up studies of children with chronic lung disease have shown that the functional abnormalities will improve but may still be present in later childhood.

Child↗

PubMed2006

Effect of smoke inhalation on viscoelastic properties and ventilation distribution in sheep.

Smoke inhalation injuries are the leading cause of mortality from burn injury. Airway obstruction due to mucus plugging and bronchoconstriction can cause severe ventilation inhomogeneity and worsen hypoxia. Studies describing changes of viscoelastic characteristics of the lung after smoke inhalation are missing. We present results of a new smoke inhalation device in sheep and describe pathophysiological changes after smoke exposure. Fifteen female Merino ewes were anesthetized and intubated. Baseline data using electrical impedance tomography and multiple-breath inert-gas washout were obtained by measuring ventilation distribution, functional residual capacity, lung clearance index, dynamic compliance, and stress index. Ten sheep were exposed to standardized cotton smoke insufflations and five sheep to sham smoke insufflations. Measured carboxyhemoglobin before inhalation was 3.87 +/- 0.28% and 5 min after smoke was 61.5 +/- 2.1%, range 50-69.4% (P < 0.001). Two hours after smoke functional residual capacity decreased from 1,773 +/- 226 to 1,006 +/- 129 ml and lung clearance index increased from 10.4 +/- 0.4 to 14.2 +/- 0.9. Dynamic compliance decreased from 56.6 +/- 5.5 to 32.8 +/- 3.2 ml/cmH(2)O. Stress index increased from 0.994 +/- 0.009 to 1.081 +/- 0.011 (P < 0.01) (all means +/- SE, P < 0.05). Electrical impedance tomography showed a shift of ventilation from the dependent to the independent lung after smoke exposure. No significant change was seen in the sham group. Smoke inhalation caused immediate onset in pulmonary dysfunction and significant ventilation inhomogeneity. The smoke inhalation device as presented may be useful for interventional studies.

Animals↗

PubMed2006

Decrease of functional residual capacity and ventilation homogeneity after neuromuscular blockade in anesthetized young infants and preschool children.

BACKGROUND: Based on age-dependent differences in pulmonary mechanics, the effect of neuromuscular blockade may differ in infants compared with older children. The aim of this study was to determine the impact of neuromuscular blockade and its reversal by positive end-expiratory pressure (PEEP) on functional residual capacity (FRC) and ventilation distribution in young infants and preschool children. METHODS: The authors studied 14 infants (aged 0-6 months) and 25 preschool children (aged 2-6 yr). FRC and lung clearance index were calculated. Measurements were taken (1) after intubation, (2) during neuromuscular blockade, and (3) during neuromuscular blockade plus application of PEEP (3 cm H2O). RESULTS: Functional residual capacity (mean +/- SD) decreased from 21.3 +/- 4.7 ml/kg to 12.2 +/- 4.8 ml/kg (P < 0.001) during neuromuscular blockade in infants and from 25.6 +/- 5.9 ml/kg to 23.0 +/- 5.3 ml/kg (P < 0.001) in preschool children. With the application of PEEP, FRC increased to 22.3 +/- 5.9 ml/kg (P = 0.4829, compared with baseline) in infants and 28.2 +/- 5.8 ml/kg (P < 0.001) in children. The lung clearance index increased after neuromuscular blockade, whereas baseline values were regained after the application of PEEP. The changes induced by neuromuscular blockade were significantly greater in infants compared with preschool children (P < 0.001). CONCLUSIONS: Although the use of neuromuscular blockade decreased FRC and ventilation distribution substantially in both groups, the changes were more pronounced in young infants. With PEEP, FRC increased and ventilation homogeneity was restored. These results provide a rationale to use PEEP in anesthetized, paralyzed infants and children.

Anesthesia↗

PubMed2005

The value of electrical impedance tomography in assessing the effect of body position and positive airway pressures on regional lung ventilation in spontaneously breathing subjects.

OBJECTIVE: Functional electrical impedance tomography (EIT) measures relative impedance changes in lung tissue during tidal breathing and creates images of local ventilation distribution. A novel approach to analyse the effect of body position and positive pressure ventilation on intrapulmonary tidal volume distribution was evaluated in healthy adult subjects. DESIGN AND SETTING: Prospective experimental study in healthy adult subjects in the intensive care unit at university hospital. SUBJECTS: Ten healthy male adults. INTERVENTIONS: Change in body position from supine to prone, left and right lateral during spontaneous breathing and positive pressure support ventilation. MEASUREMENTS AND RESULTS: EIT measurements and multiple-breath sulphur hexafluoride (SF6) washout were performed. Profiles of average relative impedance change in regional lung areas were calculated. Relative impedance time course analysis and Lissajous figure loop analysis were used to calculate phase angles between dependent or independent lung and total lung (phi). EIT data were compared to SF6 data washout measuring the lung clearance index (LCI). Proposed EIT profiles allowed inter-individual comparison of EIT data and identified areas with reduced regional tidal volume using pressure support ventilation. Phase angle phi of dependent lung in supine position was 11.7+/-1.4 degrees, in prone 5.3+/-0.5 degrees, in right lateral 11.0+/-1.3 degrees and in left lateral position 10.8+/-1.0 degree. LCI increased in supine position from 5.63+/-0.43 to 7.13+/-0.64 in prone position. Measured phi showed inverse relationship to LCI in the four different body positions. CONCLUSIONS: EIT profiles and phi of functional EIT are new methods to describe regional ventilation distribution with EIT allowing inter-individual comparison.

Adult↗

PubMed2004

Ventilation inhomogeneities in relation to standard lung function in patients with cystic fibrosis.

Based on serial lung function measurements performed in 142 children (68 males; 74 females) with cystic fibrosis (CF), prospectively evaluated over an age range of 6 to 20 years, we attempted to determine whether the lung clearance index (LCI) as a measure of ventilation inhomogeneities could be a discriminating factor of disease progression. Annual follow-up lung function measurements featuring FRC determined by whole-body plethysmography and multibreath nitrogen washouts, effective specific airway resistance, flow-volume curves, LCI, and gas exchange characteristics were analyzed by linear mixed-model analysis and Kaplan-Meier statistics. The earliest occurring and strongest factor of progression was the LCI, followed by maximal expiratory flow (MEF(50)) and FRC determined by plethysmography (p < 0.0001). Associations between onset of chronic Pseudomonas aeruginosa infection and CF transmembrane conductance regulator (CFTR) genotype with FEV(1) (p = 0.027) and FVC (p = 0.007) were identified. The study shows that the LCI predicts earlier in life and represented much better functional progression than FEV(1). Moreover, there is no single functional predictor of progression in CF, but aside from risk factors, such as onset of chronic P. aeruginosa infection and genotype, pulmonary hyperinflation, airway obstruction, and ventilation inhomogeneities are important pathophysiologic processes that should be evaluated concomitantly as determinants of lung progression in CF.

Adolescent↗

PubMed2003

Measurement of lung volume in mechanically ventilated monkeys with an ultrasonic flow meter and the nitrogen washout method.

OBJECTIVE: Measurement of functional residual capacity (FRC) during mechanical ventilation is important to standardise respiratory system compliance and adjust the ventilator settings to optimise lung recruitment. In the present study we compared three methods to measure FRC. DESIGN: The bias flow nitrogen washout technique (FRC(N2MC)), the multiple breath nitrogen washout (FRC(MBNW)) and the multiple breath sulphur-hexafluoride washout using the molar mass signal of an ultrasonic flow meter (FRC(MBSF6)) were compared in six adult monkeys after endotracheal intubation and during spontaneous breathing and mechanical ventilation at three different positive end-expiratory pressure (PEEP) levels of 0, 5 and 10 cmH2O. SETTING: Animal research laboratory. RESULTS: We found good agreement between all three methods and they all accurately measured changes in FRC when PEEP was increased. The coefficients of variance of the three measurement techniques were in the same range (1.3-9.2%). CONCLUSION: The measurement of the tracer gas concentration with the molar mass signal of the ultrasonic flow meter provides a good and simple alternative to respiratory mass spectrometer for FRC measurements in ventilated subjects.

Airway Resistance↗

PubMed2002

Positive end-expiratory pressure and ventilation inhomogeneity in mechanically ventilated children.

OBJECTIVE: To obtain optimal titration of positive end-expiratory pressure (PEEP) during mechanical ventilation with functional residual capacity and ventilation homogeneity measurements. DESIGN: Experimental human and animal study. INTERVENTIONS: Functional residual capacity and five indices of uneven ventilation (alveolar mean dilution number, mean dilution number, lung clearance index, mixing ratio, and pulmonary clearance delay) were investigated in 22 children aged 0 to 14 yrs with lung disease and in seven rabbits by using a sulfur-hexafluoride wash-out technique. The children and rabbits were exposed to three different levels of PEEP (0, 5, and 10 cm H(2)O for the children and 0, 3 and 6 cm H(2)O for the rabbits). RESULTS: Functional residual capacity of the children increased from 256.9 +/- 178.6 mL (0 PEEP) to 280.0 +/- 201.1 mL (5 PEEP) and to 302.2 +/- 160.4 mL (10 PEEP, p <.001). Ventilation inhomogeneity decreased significantly in all children with increasing PEEP (p <.05). The alveolar mean dilution number decreased from 2.00 +/- 0.29 (0 PEEP) to 1.82 +/- 0.37 (5 PEEP) and to 1.66 +/- 0.34 (10 PEEP), and pulmonary clearance delay decreased from 74.9 +/- 24.2% to 66.6 +/- 38.1% and to 63.9 +/- 24.2%, respectively. The reduction in ventilation inhomogeneity was associated with an improvement in Pao(2) from 101 +/- 42 mm Hg (0 PEEP) to 122 +/- 48 mm Hg (5 PEEP) and to 126 +/- 53 mm Hg (10 PEEP). Functional residual capacity of the rabbits increased from 54.1 +/- 18.7 mL at 0 PEEP to 72.3 +/- 23.4 mL at 3 PEEP and to 93.9 +/- 27.3 mL at 10 PEEP. Alveolar mean dilution number decreased from 2.93 +/- 0.1 (0 PEEP) to 2.20 +/- 0.29 (3 PEEP) and to 1.45 +/- 0.13 (6 PEEP). CONCLUSIONS: In children with lung disease receiving ventilatory support, optimal PEEP titration can be obtained by the measurement of the functional residual capacity and ventilation distribution by using a sulfur-hexafluoride wash-in-wash-out technique.

Journal Article↗