Optimization of the Advanced Earth Observing Satellite II Global Imager channels by use of radiative transfer calculations

The channel specifications of the Global Imager onboard the Advanced Earth Observing Satellite II have been determined by extensive numerical experiments. The results show that there is an optimum feasible position for each ocean color channel. The bandwidth of the 0.763-microm channel should be less than 10 nm for good sensitivity to the cloud top height and geometric thickness of the cloud layer; a 40-nm bandwidth is suitable for the 1.38-microm channel to have the strongest contrast between cloudy and clear radiance with a sufficient radiant energy; and a 3.7-microm channel is better than a 3.95-microm channel for estimation of the sea surface temperature (SST) and determination of the cloud particle size when the bandwidth of the channel is 0.33 microm. A three-wavelength combination of 6.7, 7.3, and 7.5 microm is an optimized choice for water vapor profiling. The combination of 8.6, 10.8, and 12.0 microm is suitable for cloud microphysics and SST retrievals with the split-window technique.

Resistance index of uterine artery and placental location in intrauterine growth retardation

BACKGROUND

Our aim was to investigate the relationship between placental location and resistance index (RI) of uterine arteries in cases with intrauterine growth retardation (IUGR).

METHODS

Placental location and flow velocity waveforms of uterine arteries in 86 normal and 20 IUGR cases from 33 to 38 weeks of gestation were examined using a combined real-time scanner and pulsed Doppler ultrasonography. The location of placenta was classified as lateral when most of it was located to either the right or the left side of the uterine midline. Otherwise it was called central. Cases where the placenta was located in the uterine fundus or in the lower segment were not included. RI values were calculated from the uterine arteries on the placental side, on the non-placental side and in case of central placentas as a mean of both uterine arteries. In normal cases, the calculations were done every second week from 33 to 38 weeks of gestation, and the difference in variance among three gestational ages in each artery was tested by a one-way ANOVA. In IUGR cases, a standard deviation score (SDS) was calculated individually in each artery as (RI - normal mean)/normal SD. Differences in SDS between three categories of uterine arteries were examined by non-parametric tests.

RESULTS

In normal cases, there was no significant difference in variance of RIs among three gestational ages in each category of arteries. In IUGR cases, SDSs on the placental side were higher than those on the non-placental side and those in central placenta, (p<0.01, Wilcoxon's and Mann Whitney's tests, respectively). SDSs in five of eight cases with central placentas were below 1.0. Two of 12 cases with lateral placentas had higher SDSs on the non-placental side than on the placental side and resulted in abruptio placentae.

CONCLUSIONS

Deviation of RIs in uterine arteries with IUGR could be affected by the pathologic conditions of the utero-placental blood flow on the placental side of lateral placenta rather than in central placenta and might be done by dramatic increase in resistance to flow of the myometrial vessels on the non-placental side.

Assessment of c-erbB2 and vascular endothelial growth factor mRNA expression in fine-needle aspirates from early breast carcinomas: pre-operative determination of malignant potential

AIMS

Although axillary lymph nodes status, tumour size, hormonal-receptor status and histological grade at diagnosis are frequently used to orient the treatment of breast cancer patients, some tumours recur in patients with early stage disease. Pre-operative assessment of individual tumour characteristics, based on oncogenes and growth factors related to tumour growth, invasion or metastasis, may guide the treatment for patients with breast carcinomas.

METHODS

We examine here the prognostic significance of cyclin D1, urokinase type plasminogen activator, vascular endothelial growth factor (VEGF), platelet-derived growth factor, and c-erbB2 expression in pre-operatively obtained fine-needle aspirates from breast carcinomas less than or equal to 3 cm in size. Correlation between mRNA expression of these factors and clinicopathological characteristics was analysed.

RESULTS

The level of c-erbB2 mRNA expression was significantly higher in tumours with lymph node metastases than in those without lymph node metastases. VEGF mRNA expression positively correlated with the degree of angiogenesis as quantitated by immunohistological staining with a CD31 monoclonal antibody.

CONCLUSIONS

Analysis of c-erbB2 and VEGF mRNA expression in fine-needle aspirates may be useful in assessing the malignant potential of individual breast carcinomas, leading to a pre-operative discrimination of a high-risk group.

Development of a health promotion system for the elderly: Committee of Health Evaluation for Elderly Persons Council of Japan AMHTS Institutions

A new health promotion approach for elderly persons is required which maintains not only their physical health but also their quality of life. We are developing a health promotion system which makes use of questionnaires dealing with physical conditions and quality of life, and makes health reports. Health evaluation is carried out in three steps. First, detailed information about the physical health of each client is collected. Second, quality of life is evaluated according to five health indicators. Last, health recommendations are generated. An artificial intelligence (AI) program produces detailed questions to collect necessary information for the evaluation of a client's health. The information related to quality of life is converted into five health indicators and presented as a radar-chart in documents and displays. The knowledge-based AI program automatically generates the health recommendation documents. This information is available for physicians and nurses for health counseling.

Simulator for virtual surgery using deformable organ models and force feedback system

This paper describes a real-time surgery planning system using virtual reality techniques. This system allows us to simulate incision of skin and organs which respond as elastic objects with surgical tools in virtual space. Inner structures such as blood vessels and lesions can be seen and manipulated in the simulation. In addition to these functions we attempted to add a feedback function that responds to the operator's hands. We developed a force feedback device to manipulate the elastic organ model based on pressure from the operator's fingers.

Preoperative assessment of tumor angiogenesis by vascular endothelial growth factor mRNA expression in homogenate samples of breast carcinoma: fine-needle aspirates vs. resection samples

BACKGROUND AND OBJECTIVES

Tumor angiogenesis is receiving increased attention as a prognostic factor and also as a possible target for new anticancer agents. We investigated whether extent of vascular endothelial growth factor (VEGF) mRNA expression correlated with degree of neovascularization, and whether this expression in fine-needle aspirates could be a marker for assessing angiogenic potential of breast tumors.

METHODS

VEGF mRNA expression was semiquantitated by reverse transcriptase-polymerase chain reaction (RT-PCR) followed by Southern blotting. Tumor neovascularization was assessed by immunohistochemical staining with anti-CD31 (PECAM) antibody.

RESULTS

There was a positive correlation between degree of neovascularization and semiquantitated VEGF mRNA expression in invasive ductal carcinomas (r2 = 0.346, n = 48, P < 0.05). Extent of VEGF mRNA expression in fine-needle aspirates was closely correlated with that in resected invasive ductal carcinomas equal to or less than 3 cm in size (r2 = 0.874, n = 14, P < 0.05).

CONCLUSION

These data suggest that semiquantitation of VEGF mRNA expression in fine-needle aspirates is useful for assessing angiogenic potential of invasive ductal carcinomas.

Nonlinear analysis of visual evoked potentials elicited by color stimulation

The relationship between chromatically modulated stimuli and visual evoked potentials (VEPs) was considered. VEPs of normal subjects elicited by chromatically modulated stimuli were measured under several color adaptations, and their binary kernels were estimated. Up to the second-order, binary kernels obtained from VEPs were so characteristic that the VEP-chromatic modulation system showed second-order nonlinearity. First-order binary kernels depended on the color of the stimulus and adaptation, whereas second-order kernels showed almost no difference. This result indicates that the waveforms of first-order binary kernels reflect perceived color (hue). This supports the suggestion that kernels of VEPs include color responses, and could be used as a probe with which to examine the color visual system.

The effect of behavioral states on fetal heart rate and middle cerebral artery flow-velocity waveforms in normal full-term fetuses

OBJECTIVES

To evaluate the effect of fetal behavioral states on the relationship between fetal heart rate (FHR) and middle cerebral artery resistance index (MCA RI) in normal fetuses.

METHODS

The FHR and MCA RI of 10 normal cases from 37 to 40 weeks of gestation were recorded consecutively over a 45-min period. Correlations between the MCA RI and FHR during resting and active phases, classified by an actocardiotocogram, were analyzed by simple regression analysis.

RESULTS

The mean FHR and MCA RI were significantly higher during the active phase (140.3 +/- 6.6 bpm, 0.79 +/- 0.06) than those during the resting phase (137.4 +/- 6.8 bpm, 0.75 +/- 0.07, P < 0.01, two sample t-test). There was a significant negative correlation (r = - 0.22, n = 2642, P < 0.01) between RI and FHR during the active phase and a significant positive correlation (r = 0.28, n = 2066, P < 0.001) during the resting phase.

CONCLUSIONS

The relationship between FHR and the MCA RI during the resting phase is different from during the active phase.

Nitric oxide (NO) measurement accuracy

BACKGROUND

Evaluation of the clinical utility of NO requires accurate assessment of inspired [NO]. Currently, chemiluminescence analyzers are the clinical standard for analysis; however, their performance in the clinical setting has not been systemically evaluated.

METHODS

We evaluated the performance of four chemiluminescence analyzers (270B NOA, Sievers Instruments, Inc.; CLA 510S, Horiba Co., Ltd.; CLD 700 AL, Eco Physics Corp.; Model 42, Thermo Environmental Instruments Inc.) in simulated clinical settings. Transport delay and dynamic 95% response time were measured by the balloon in a glass chamber puncture technique. Fluctuating [NO] in a continuous flow of gas and [NO] during mechanical ventilation, where NO was premixed prior to entering the ventilator, were evaluated.

RESULTS

Transport delay ranged from 1.02 +/- 0.02 to 24.36 +/- 2.47 s (p < 0.05) and the 95% response time ranged from 0.22 +/- 0.04 to 70.03 +/- 0.03 s (p < 0.05). Accurate analysis of [NO] in a continuous flow system was only possible with the most rapid response analyzer (270B NOA). All other analyzers under reported the maximum [NO] (p < 0.05) and over reported the minimum [NO] (p < 0.05). All analyzers accurately determined [NO] in the inspiratory limb of the ventilator circuit, but none accurately determined [NO] at the airway opening.

CONCLUSIONS

Measurements of inhaled [NO] can vary greatly, dependent upon the performance characteristics of the analyzer and the location of NO analysis. All studies evaluating the clinical use of NO should fully describe the technical gas delivery methodology and the response time and transport delay of the chemiluminescence analyzer used.

Mapping visual field with positron emission tomography by mathematical modeling of the retinotopic organization in the calcarine cortex

We developed an objective and quantitative method of mapping the human visual field with positron emission tomography (PET) and magnetic resonance image (MRI). The regional cerebral blood flow (rCBF) images were acquired with H2(15)O-PET under visual fixation as well as under visual stimulation with flickering diodes arranged along the ring at 0 degree, 3 degrees, 7 degrees, 14 degrees, 21 degrees, or 29 degrees from the fixation point. After coregistration of PET and MR images, we extracted the surface of the calcarine cortex from the MR images and unfolded it to a two-dimensional (2-D) elliptic plane, on which the activated PET images were superimposed. Then we transformed the unfolded calcarine cortex into the visual field coordinates using the complex logarithmic function proposed by Schwartz. A large individual variation was observed in the retinotopical organization as well as in the morphology of the calcarine cortex. The formula was valid only within 15 degrees from the center of the visual field. The constant parameter in the formula was estimated to be 1.5. The cortical linear magnification factor was 12.1, 2.8, and 1.6 at 0, 5, and 10 degrees, respectively. The areas of the central 10 degrees and 40 degrees in the visual field correspond to 50% and 81% of the calcarine surface, respectively.

Two novel missense mutations in the ATP-binding domain of the adrenoleukodystrophy gene: immunoblotting and immunocytological study of two patients

Two novel missense mutations, 1939G to A (R518Q) and 2017A to G (Q544R) were identified in Japanese patients with adrenoleukodystrophy (ALD). They are located in exon 6, which encodes part of the putative adenosine triphosphate binding domain of ALD protein. The ALD protein carrying the R518Q mutation was undetectable in fibroblasts, by immunoblot and immunofluorescence analysis, while the Q544R mutation had no apparent effect on the stability and localization of the ALD protein, but is expected to affect its function.

[Comparison of the number of parameters using nonlinear iteration methods for compartment model analysis with 18F-FDG brain PET]

In the analysis of the brain kinetic images with 18F-FDG, compartment models with 3 or 4 parameters and an estimation method of nonlinear least squares (NLS) have been applied. We compared the Simplex method and the modified Marquardt method as an iterative NLS algorithm on the simulation data with variable noise. The estimated k-values were equal in the both algorithms. The calculation with modified Marquardt method was three times faster than that of the Simplex method. The dependence of modified Marquardt estimates on the initial values was larger than that of the Simplex, but the permissible initial value range was wide enough for clinical data. Therefore, the modified Marquardt method was found to be more suitable for the compartment model analysis of 18F-FDG than the Simplex method. We also compared the 3-parameter with 4-parameter models for 45 min and 120 min data acquired after administration. The 3-parameter model was suitable for the 45-minute data acquisition, and the 4-parameter model was suitable for the 120-minute data acquisition.

Molecular cloning of cDNA encoding rat very long-chain acyl-CoA synthetase

The cDNA encoding rat very long-chain acyl-CoA synthetase (VLACS) was cloned, using degenerative primers synthesized according to the partial amino acid sequences of the peptide fragments of the purified rat liver enzyme. The longest cDNA insert was 2972 base pairs with a 1860-base pair open reading frame encoding 620 amino acids. The calculated molecular mass of 70,692 daltons was consistent with size of the purified enzyme. In Northern blot analysis, a single band was detected at the position of about 3 kilobases, corresponding to the size of the cloned cDNA. cDNA-directed expression in Escherichia coli resulted in accumulation of expressed protein, as an inclusion body. An antibody was raised using this expressed protein to characterize the cDNA and the enzyme. The subcellular localization of VLACS in peroxisomes and microsomes was demonstrated in Western blot analysis. The specific activity and the substrate specificity of the cDNA expressed enzyme in COS-1 cells were consistent with those of the purified rat enzyme. The predicted amino acid sequence of VLACS had a high sequence similarity to fatty acid transport protein (Schaffer, J. E., and Lodish, H. F. (1994) Cell 79, 427-436), and was considered to have domains for adenylation and thioester formation. The entire structure of VLACS was dissimilar to that of long-chain acyl-CoA synthetase (Suzuki, H., Kawarabayashi, Y., Kondo, Y., Abe, T., Nishikawa, K., Kimura, S., Hashimoto, T., and Yamamoto, T. (1990) J. Biol. Chem. 265, 8681-8685), except for the domains.

Interleukin 4 inhibits hepatocyte growth factor-induced invasion and migration of colon carcinomas

Hepatocyte growth factor (HGF) is known to have a number of biological properties including promoting tumor progression of human carcinomas. Metastasis involves a number of events that are attributed to induction by paracrine factors such as HGF. Identification of natural inhibitors of these events would allow better control of tumor progression. Recently we demonstrated that interleukin 4 (IL-4) can regulate proliferation of various human carcinoma cell lines. In the present study, we used established human colon carcinoma cell lines and primary colon carcinoma cell cultures to determine if IL-4 could regulate HGF-induced cell proliferation and other events of tumor progression such as MMP (matrix metalloproteinases)-1, -2, and -9 production, cell migration and cell-matrix invasive activity. All colon carcinoma cell lines expressed HGF and IL-4 receptors. IL-4 significantly inhibited HGF-induced proliferation of one cell line. Cell-matrix invasion was significantly enhanced by HGF (0.1-10 ng/ml); IL-4 (1-10 U/ml) significantly inhibited HGF-induced invasion in a dose-dependent manner. IL-4 also inhibited HGF-induced cell-matrix invasion of metastatic colon carcinoma cells and HGF-induced cell migration. HGF enhanced MMP-1, -2, and -9 production by cell lines. This effect could be inhibited by IL-4. These findings indicate that IL-4 is a potent inhibitor of HGF-induced invasion and metastasis-related functions of human colon carcinoma cells.

Vascular endothelial growth factor and platelet-derived growth factor are potential angiogenic and metastatic factors in human breast cancer

BACKGROUND

Angiogenesis is a prerequisite for tumor growth and metastasis. Tumor angiogenesis may be mediated by several angiogenic factors such as vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), transforming growth factor-alpha, and basic fibroblast growth factor.

METHODS

Differential mRNA expressions of VEGF, PDGF (A chain), transforming growth factor-alpha and basic fibroblast growth factor in 32 primary invasive breast tumors were examined by reverse transcriptase-polymerase chain reaction. We analyzed relationships between mRNA expressions of these angiogenic factors and the degree of angiogenesis, tumor size, and metastasis. Quantification of angiogenesis was achieved by the immunohistochemical staining of endothelial cells with antibody to CD31.

RESULTS

VEGF and PDGF-A mRNAs were expressed more frequently in breast tumors than in nontumor breast tissues, whereas no difference was found in expression frequency of either transforming growth factor-alpha or basic fibroblast growth factor mRNA. Vascular counts in tumors correlated with each expression frequency of VEGF and PDGF-A mRNA. PDGF-A mRNA was expressed more frequently in tumors with lymph node metastasis than in those without metastasis.

CONCLUSIONS

Expression of VEGF and PDGF mRNAs detected by reverse transcriptase-polymerase chain reaction in breast tumors correlates with tumor-related characteristics of angiogenesis and metastatic potential. Analysis of these mRNAs by reverse transcriptase-polymerase chain reaction may be useful for assessing the biologic behavior of a breast tumor before surgical treatment.

In vitro analysis of peritoneal adhesions in peritonitis

Peritoneal adhesions due to peritonitis make surgery more difficult and may cause complications. Clarifying the formation mechanism of peritoneal adhesions could help identify methods useful for their prevention. We cultured mesothelial monolayers on plates and microcarriers to simulate the parietal and visceral peritoneum, respectively. We then investigated the effects of lipopolysacchride (LPS) and tumor necrosis factor (TNF) on the homologous adhesion of these mesothelial monolayers. There was no adhesion of mesothelial monolayers in the control medium. When monolayers were cultured with endotoxin (LPS), approximately 90% of the microcarriers adhered to the mesothelial microplate. Adhesions occurred at LPS concentrations of 10 ng/ml and increased linearly in a dose-dependent manner. Kinetic studies revealed that the mesothelial adhesion appeared at 12 hr, and that 90% of the microcarriers were adherent after 24 hr. Open intercellular spaces were observed after a 24-hr treatment with LPS. Scanning electron microscopy revealed that the mesothelial cells adhered to the naked glass. LPS also caused increased permeability of the mesothelial monolayer. TNF did not cause any significant adhesion. Through our experiments we were able to develop an in vitro model of peritoneal adhesion using peritoneal mesothelial cell culture. Endotoxin caused an increase in homologous adhesion of peritoneal mesothelial monolayers, which may correspond to the initial stage of peritoneal adhesion formation in peritonitis.

Diurnal variations in resting-active cycles in full-term fetal heart rate changes

To elucidate the mechanism of the resting-active cycles (RAC) of fetal heart rates (FHR), in the resting and non-resting phases (RP and NRP), 24-h FHR recordings were made on 16 normal full-term pregnant women. RP, NRP, RAC-1 (NRP-NRP cycle), and RAC-2 (RP-RP cycle) were defined based on the criteria of Nijhuis et al. Frequency distributions were plotted separately for the entire 24-h period as well as for the day-time (07:00-21:00 h) and night-time (21:00-07:00 h), and were compared using Kolmogorov-Smirnov two-sample tests. The mean durations (+/- S.D.) (min) of RP, NRP, RAC-1, and RAC-2 were 22.7 +/- 11.2, 67.3 +/- 47.2, 90.0 +/- 47.6, and 89.9 +/- 48.6 during 24-h periods, 20.1 +/- 7.7, 68.3 +/- 52.3, 88.6 +/- 53.1, and 88.4 +/- 53.0 during the day-time, and 25.4 +/- 13.2, 66.2 +/- 41.2, 91.4 +/- 41.0, and 91.5 +/- 43.4 during the night-time. Length of RP was the only factor significantly different during the day and night (P < 0.05). We propose that there are different mechanisms controlling RP and NRP.

Mucopolysaccharidosis type I: identification of common mutations that cause Hurler and Scheie syndromes in Japanese populations

alpha-L-Iduronidase (IDUA) deficiency (mucopolysaccharidosis type I; MPS-I) is an inborn error of lysosomal degradation of glycosaminoglycans that results in storage of undegraded glycosaminoglycans in lysosomes. Previous studies in Caucasian populations showed that (1) homozygosity or compound heterozygosity for the W402X and Q70X mutations are the common causes of MPS-I with a severe form (Hurler syndrome), and (2) the presence of R89Q may lead to a milder phenotype. We studied mutations in the IDUA gene from 19 MPS-I patients, including two pairs of siblings, with various clinical phenotypes (Hurler, 6 cases; Hurler/Scheie, 7 cases; Scheie, 6 cases). We report the presence of two common mutations that account for 42% of the 38 alleles in these patients. One is a novel 5-bp insertion between the thymidine at nt 704 and a cytosine at nt 705 (704ins5), which is seen only in the Japanese population. The other is a missense mutation, R89Q, which is also seen in Caucasians, although uncommonly. In the 19 Japanese MPS-I patients, the 704ins5 mutation accounted for 7 of 38 alleles (18%), while the R89Q accounted for 9 of 38 (24%). No Japanese patient was found to carry the W402X or Q70X alleles, the two most common MPS-I mutations in Caucasians. Homozygosity for the 704ins5 mutation is associated with a severe phenotype, and for the R89Q mutation with a mild phenotype. Compound heterozygosity for these two mutations produced an intermediate phenotype. Haplotype analysis using polymorphisms linked to the IDUA locus demonstrated that each mutation occurs on a different specific haplotype, suggesting that individuals with each of these common mutations derive from common founders. These data continue to document the molecular heterogeneity and racial differences in mutations in MPS-I.

A possible role of TGF-beta in the formation of malignant effusions

The detailed mechanisms underlying the formation of malignant effusions are incompletely defined. In order to determine whether transforming growth factor-beta (TGF-beta) would contribute to the formation of malignant effusions, we investigated the effect of TGF-beta on the morphology, growth, and permeability of human mesothelial cells, which are thought to serve as a permeability barrier in the pleuroperitoneal cavities. Treatment of the mesothelial cells with a TGF-beta dose ranging from 0.1 to 10 ng/ml for 96 hr induced distinct morphologic changes in the cells. Each cell increased in size as did the volume of the intercellular spaces. TGF-beta also significantly inhibited the growth of mesothelial cells at a concentration ranging from 0.1 to 10 ng/ml. This growth inhibition was blocked completely by the addition of anti-TGF-beta antibody. Treatment of the mesothelial cells with 2.0 ng/ml TGF-beta significantly increased the permeability of a mesothelial cell monolayer as assessed by a FITC-albumin permeability assay. In our clinical analysis using 10 effusion samples obtained from patients with various types of carcinoma cells, considerable level of TGF-beta could be detected by ELISA, ranged from 0.90 to 8.75 ng/ml. Our data suggest that TGF-beta plays an important role in the formation of malignant effusions through structural and functional damage to the mesothelial cells. Malignant effusions may accumulate in the pleuroperitoneal cavity as a result of the mesothelial cell damage caused by this cytokine which is released from disseminated cancer cells.

Pulmonary resistance in dogs: a comparison of xenon with nitrous oxide

Xenon (Xe) may cause an increase in airway resistance due to its high density and viscosity. The object of this study was to examine the effects of Xe on pulmonary resistance using dog models with normal and methacholine-treated airways. During anaesthesia 22 mongrel dogs' tracheas were intubated and the lungs were mechanically ventilated with 70% N2/30% O2 as a control gas. The gases 70% nitrous oxide (N2O), 50% N2O, 70% Xe and 50% Xe were administered in a random order for 25 min. Bronchoconstriction was produced by a continuous infusion of methacholine, 0.22 mg.kg-1.hr-1. Pulmonary resistance (RL) was calculated by the isovolume method using flow at the airway opening, volume and transpulmonary pressure. In normal dogs, RL breathing 70% Xe (mean +/- SEM, 0.84 +/- 0.12 cm H2O.L-1.sec-1) was greater (P < 0.05) than with 70% N2O, 50% N2O or control gas (0.61 +/- 0.08, 0.59 +/- 0.06 and 0.62 +/- 0.06 cmH2O.L-1.sec-1). Breathing 50% Xe the RL (0.77 +/- 0.10 cmH2O.L-1.sec-1) was not different from 50% N2O or control. Methacholine infusion increased RL 3.92 +/- 1.98 (mean +/- SD) times. The RL breathing 50% Xe (2.55 +/- 0.44 cmH2O.L-1.sec-1) was not greater than during 50% N2O or control (2.08 +/- 0.33 and 2.13 +/- 0.33 cmH2O.L-1.sec-1) in methacholine-treated dogs. The data suggest that inhalation of high concentrations of Xe increases airway resistance, but only to a modest extent in dogs with normal or methacholine-treated airways.

A comparative evaluation of pressure-triggering and flow-triggering in pressure support ventilation (PSV) for neonates using an animal model

The triggering system in pressure support ventilation needs to respond rapidly, especially in neonates. The aim of this study was to compare the effects of flow-triggered and pressure-triggered pressure support ventilation on neonatal mechanical ventilation using an animal model. Respiratory flow, airway pressure, oesophageal pressure, and diaphragmatic electromyogram were measured during pressure support ventilation in five anaesthetized rabbits. The animals were connected to a VIPBIRD (Bird, U.S.A.) (CPAP mode, pressure support ventilation, 5 cm H2O and PEEP 0 cm H2O). Flow-triggering sensitivity was set at 0.2l/min, 0.5l/min, 1.01l/min, or 1.5l/min. Pressure-triggering sensitivity was set at -1.0 cm H2O. Shorter trigger delay and longer pressure support time were observed in flow-triggering. There was also less diaphragmatic activity in flow-triggering as evidenced by the amplitude of integrated diaphragmatic electromyogram and negative deflection of oesophageal pressure. The findings suggest that flow-triggering will prove superior to pressure-triggering in pressure support ventilation for neonates.