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PubMedDate not supplied

Additional intravitreal gas injection in the early postoperative period for an unclosed macular hole treated with internal limiting membrane peeling.

PURPOSE: To study the efficacy of additional intravitreal gas injection for unclosed macular holes within 2 weeks after surgery with internal limiting membrane peeling. METHODS: We reviewed the results for five consecutive eyes receiving additional intravitreal gas injection for unclosed macular holes within 2 weeks after initial macular hole surgery with internal limiting membrane peeling. The initial surgery consisted of standard pars plana vitrectomy with phacoemulsification and intraocular lens implantation, indocyanine green-assisted peeling of the retinal internal limiting membrane, and fluid-gas exchange with 20% sulfur hexafluoride. The patients were instructed to assume face down positioning for > or =7 days after surgery. If an unclosed macular hole was found after the residual gas volume decreased to <30% of the eyeball volume, fluid-gas exchange was performed using 15% octafluoropropane. RESULTS: All five eyes receiving additional intravitreal gas 7 to 14 days after vitrectomy had complete macular hole closure with macular flattening, as shown by optical coherence tomography 1 month after the additional gas injection. Visual acuity improved (range, 20/100 to 20/30). A minimum of 9 months of follow-up revealed no reopening or serious complications. CONCLUSION: Additional gas injection during the early postoperative period is recommended for eyes with unclosed macular holes that have undergone vitrectomy with internal limiting membrane peeling.

Aged↗
PubMed1999

Postoperative gas bubble foot drop. A case report.

STUDY DESIGN: An unusual case of foot drop occurring 10 days after disc surgery is reported. Imaging studies identified a gas bubble compressing the nerve root. OBJECTIVE: To describe the origin and management of a radiculopathy caused by an intraspinal gas bubble. SUMMARY OF BACKGROUND DATA: A recurrent lumbar disc herniation was diagnosed by clinical and imaging studies. A vacuum disc also was noted at the same level. These are common and not considered to be of pathologic significance. METHODS: The patient underwent a microdiscectomy for a lumbar disc extrusion. The postoperative course was excellent, with relief of symptoms and no neurologic deficit. Ten days later, the awoke with a foot drop and pain in the leg. Imaging studies showed a 4-mm gas bubble compressing the nerve root. Oral steroids were given for 10 days. RESULTS: Progressive improvement occurred, and the patient was asymptomatic 6 weeks later. Although in some instances it may be necessary to evacuate intraspinal gas, an initial period of observation is warranted, because the gas and its resulting symptoms may disappear spontaneously. CONCLUSION: Intradiscal gas accumulation, better known as vacuum disc, is considered to be a benign indication of degenerative disc disease. On occasion it can be a cause of symptoms. A case is reported in which gas leaked after surgery into the spinal canal, causing a foot drop. The symptoms and gas disappeared spontaneously without further treatment.

Adult↗
PubMed2004

A modified ICRP 66 iodine gas uptake model and its parametric uncertainty.

Intakes via inhalation may occur from radionuclides released in the form of a gas. The chemical characteristics pertaining to the release influence the intake and subsequent dose to an exposed individual. Gases are taken up or absorbed in the entire respiratory tract and the associated uptake mechanisms are quite different from deposition of particulates. Gaseous iodine can exist in various chemical forms, e.g., elemental iodine, inorganic, and organic iodine compounds. These different chemical species play an integral role in the gaseous uptake o f iodine in t he respiratory tract. Gas uptake in the various regions of the respiratory tract results in the intake of iodinated material into the body. The radioactive iodine taken up in the gas-exchange tissues is absorbed into the bloodstream of an individual and subsequently transferred to other organs. Iodine in the circulatory system can then be taken up by the thyroid gland, with resulting dose to the thyroid. The magnitude and uncertainty in regional gas uptake is important in the assessment of individuals exposed to airborne releases of radioiodine. The current ICRP 66 model is rudimentary and estimates regional gas uptake based on solubility and reactivity of the different radionuclides entering the respiratory tract. The modified model proposed here employs methodology and a mathematical structure to determine estimates of fractional gas uptake rather than defaulting to literature values, as in the current ICRP model. Model parameters have been assigned input distributions and estimates of uncertainty have been determined. A sensitivity analysis of these parameters has been performed to demonstrate the importance of each of these parameters. The sensitivity analysis ranks the model-input parameters by their importance to estimates of regional gas uptake. The model developed herein may be used for improved estimation of gas uptake in the respiratory tract and subsequent dose estimates from the different chemical forms of radioiodine.

Adult↗
PubMed1991

Antibodies to the N-terminal sequence of GVPa bind to the ends of gas vesicles.

Antibodies were raised against intact gas vesicles of Anabaena flos-aquae, and against a synthetic peptide (GVPaNT) whose sequence is identical to the N-terminal region of the main gas vesicle protein, GVPa. A two-stage centrifugation procedure is described for separating gold-labelled antibodies bound to gas vesicles from unbound antibodies. The GVPaNT antibody bound to gas vesicles that had been previously rinsed with SDS to remove the outer gas vesicle protein, GVPc. Treatment with this antibody caused the gas vesicles to aggregate together end-to-end rather than side-by-side. The binding of the anti-GVPaNT-immunogold particles to the gas vesicle was restricted to the conical ends of the structure. These observations indicate that the sequence to which the GVPaNT antibodies were raised, residues 1 to 13 of the GVPa molecule, is exposed only at the outer surface of the cones and that it is normally obscured by GVPc. As GVPa forms both the conical ends and the cylindrical midsection of the gas vesicle, exposure of the N-terminal sequence only in the cones must be due to differences in the contact between adjacent GVPa molecules in the central cylinders and end-cones.

Amino Acid Sequence↗
PubMed2002

Molecular dynamics simulation of the response of a gas to a spherical piston: implications for sonoluminescence.

Sonoluminescence is the phenomena of light emission from a collapsing gas bubble in a liquid. Theoretical explanations of this extreme energy focusing are controversial and difficult to validate experimentally. We propose to use molecular dynamics simulations of the collapsing gas bubble to clarify the energy focusing mechanism, and determine physical parameters that restrict theories of the light emitting mechanism. In this paper, we model the interior of a collapsing noble gas bubble as a hard sphere gas driven by a spherical piston boundary moving according to the Rayleigh-Plesset equation. We also include a simplified treatment of ionization effects in the gas at high temperatures. The effects of water vapor are neglected in the model. By using fast, tree-based algorithms, we can exactly follow the dynamics of 10(6) particle systems during the collapse. Our preliminary model shows strong energy focusing within the bubble, including the formation of shocks, strong ionization, and temperatures in the range of 50 000-500 000 K. Our calculations show that the gas-liquid boundary interaction has a strong effect on the internal gas dynamics, and that the gas passes through states where the mean free path is greater than the characteristic distance over which the temperature varies. We also estimate the duration of the light pulse from our model, which predicts that it scales linearly with the ambient bubble radius. As the number of particles in a physical sonoluminescing bubble is within the foreseeable capability of molecular dynamics simulations, we also propose that fine scale sonoluminescence experiments can be viewed as excellent test problems for advancing the art of molecular dynamics.

Journal Article↗
PubMed1987

Regulation of Soybean Nitrogen Fixation in Response to Rhizosphere Oxygen: II. Quantification of Nodule Gas Permeability.

Nodule nitrogen fixation rates are regulated by a mechanism which is responsive to the rhizosphere oxygen concentration. In some legumes, this oxygen-sensitive mechanism appears to involve changes in the gas permeability of a diffusion barrier in the nodule cortex. In soybean evidence for such a mechanism has not been found. The purpose of this research was to make quantitative measurements of soybean nodule gas permeability to test the hypothesis that soybean nodule gas permeability is under physiological control and responsive to the rhizosphere oxygen concentration. Intact hydroponically grown soybean plants were exposed to altered rhizosphere oxygen concentrations, and the nodule gas permeability, acetylene reduction and nodule respiration rates were repeatedly assayed. After a change in the external oxygen concentration, nitrogenase activity and nodule respiration rates displayed a short-term transient response after which the values returned to rates similar to those observed under ambient oxygen conditions. In contrast to steady-state nitrogenase activity and nodule respiration, nodule gas permeability was dramatically affected by the change in oxygen concentration. Decreasing the external oxygen concentration to 0.1 cubic millimeter per cubic millimeter resulted in a mean increase in nodule gas permeability of 63%. Increasing the rhizosphere oxygen concentration resulted in decreased nodule gas permeability. These data are consistent with the hypothesis that soybean nodules are capable of regulating nitrogen fixation and nodule respiration rates in response to changes in the rhizosphere oxygen concentration and indicate that the regulatory mechanism involves physiological control of the nodule gas permeability.

Journal Article↗
PubMed1995

Complementation studies with the gas vesicle-encoding p-vac region of Halobacterium salinarium PHH1 reveal a regulatory role for the p-gvpDE genes.

Gas-vesicle (Vac) synthesis in Halobacterium salinarium PHH1 involves the expression of the p-vac region consisting of 14 different gvp genes that are arranged in two clusters: p-gvpACNO and, oppositely oriented, p-gvpDEFGHIJKLM. The latter cluster of genes is transcribed as two units: p-gvpDE and p-gvpF-M. The 5'-terminus of the p-gvpF-M mRNA was located 169 nucleotides upstream of p-gvpF within p-gvpE. The p-gvpG and p-gvpK gene was expressed in Escherichia coli and antibodies to proteins obtained were raised in rabbits. Both proteins could be detected in halobacterial cell lysates; in gas-vesicle preparations, however, neither GvpG nor GvpK could be found. The requirement for single p-gvp gene expression for gas-vesicle synthesis was determined by transformation experiments using the Vac- species Haloferax volcanii as recipient. Construct delta A containing all p-gvp genes except for p-gvpA, encoding the major gas-vesicle structural protein, produced Vac- transformants, but the addition of p-gvpA on a second vector restored gas-vesicle synthesis to wild-type level (Vac++). Similarly, double transformants containing p-gvpD-M plus p-gvpACNO, or p-gvpG-M (fused to the promoter of the halobacterial ferredoxin gene for expression) plus p-gvpFED-ACNO were Vac++. Transformants containing the p-vac region either lacking gvpA, gvpF, or gvpGHI were Vac-, indicating the absolute requirement of these gvp genes (or at least one in the case of gvpGHI) for gas-vesicle formation. Double transformants containing the constructs p-gvpF-M plus p-gvpACNO (delta DE) accumulated gas vesicles (Vac+) but synthesized fewer than the wild type, showing that the p-gvpDE genes are not necessary for gas-vesicle assembly. A repressor function affecting the synthesis of the p-gvpF-M mRNA could be suggested for p-gvpD and the 5'-region of its mRNA.

Archaeal Proteins↗
PubMed1991

Risk analysis of a gas-processing complex in India.

ONGC's Hazira Gas-Processing Complex (HGPC) consists of facilities for receiving natural gas along with associated condensate from an off-shore field at a rate of 20 MMN M3 per day. After separating the condensate, which is processed in condensate fractionation units, the gas is processed through various steps to recover LPG and to reduce its dew point to less than 5 degrees C in order to make it suitable for transportation over long distances. The acid gas recovered during the gas-sweetening step is processed to obtain sulphur. The major products manufactured at HGPC therefore are lean sweet gas, LPG, NGL, and sulphur. The Oil and Natural Gas Commission awarded the assignment on Hazard Study and Risk Analysis of their Hazira Gas-Processing Complex (HGPC) to the Council of Scientific and Industrial Research (CSIR) in association with the Netherlands Organisation for Applied Scientific Research (TNO). The scope of this assignment covered a number of closely related and fully defined activities normally encountered in this type of work. Identification of hazards through the most appropriate methods, assigning frequency of occurrence of major unwanted incidents, quantification and assessment of probable damage to plant equipment, environment, human and animal life due to an unexpected event, and evaluation of various methods for reducing risk, together constituted the methodology for this assignment. Detailed recommendations aimed at reducing risk and enhancing reliability of plant and machinery were made. This article gives an overview of the assignment.

Accidents, Occupational↗
PubMed2000

Quantitative analysis of bowel gas using plain abdominal radiograph in patients with irritable bowel syndrome.

OBJECTIVE: Ideally, the diagnosis of irritable bowel syndrome (IBS) would be achieved using a minimal number of procedures. It is presumed that bowel gas is related to IBS, and it is easily visualized by plain abdominal radiograph. In the present study, to clarify the relationship between IBS and the quantity of bowel gas, the measured bowel gas volume using plain abdominal radiographs was compared with the pathology of IBS. METHODS: Plain abdominal radiographs were digitized and transmitted to a computer (computed radiography) in 30 IBS patients and 30 normal controls. The quantity of bowel gas, determined as the pixel value on images and standardized by physique, was defined as the gas volume score (GVS). Using the mean +/- 2SD of GVS in the control group as the normal score, IBS patients were divided into three groups: high, normal, and low. To examine the sequential reproducibility of a similar quantity of bowel gas, a second plain abdominal radiography was performed about 2 months later, and the GVS were compared. The colonic transit time was determined using radiopaque markers. RESULTS: There was a strong correlation between the quantities of bowel gas measured by two independent gastroenterologists. The mean GVS of IBS patients was significantly higher than that in the control group (p < 0.001). The sequential reproducibility was recognized in all 10 IBS patients. There was no significance between colonic transit time and GVS, nor between symptoms and GVS. CONCLUSIONS: Abdominal gas was analyzed objectively by using GVS, and GVS was considered to represent a useful tool for the diagnosis of IBS.

Adult↗
PubMed2002

Gastric distension and duodenal lipid infusion modulate intestinal gas transit and tolerance in humans.

OBJECTIVE: Patients with unexplained abdominal complaints often attribute their symptoms to intestinal gas and indicate that symptoms are exacerbated by ingestion of a meal. However, the mechanisms responsible are unknown. Our aim was to analyze the specific influence of two meal-related factors, gastric distension, and intestinal nutrients, on intestinal gas dynamics and tolerance. METHODS: In 35 healthy subjects, gas evacuation and perception of jejunal gas infusion (12 ml/min) were measured for 3 h, during simultaneous duodenal infusion of saline, as control, lipids at 1 Kcal/min, or gastric distension. RESULTS: Infusion of lipids into the duodenum induced gas retention (584 +/- 154 ml, p < 0.05 vs 161 +/- 86 ml after saline infusion) without perception (2.2 +/- 0.5 score), whereas gastric distension induced perception (score 5.6 +/- 0.4, p < 0.05 vs score 1.9 +/- 0.4 after saline) without gas retention (7 +/- 205 ml). CONCLUSIONS: Different meal-related factors exert specific effects on intestinal gas dynamics and tolerance, and these mechanisms may interact to produce postprandial gas symptoms.

Abdominal Pain↗
PubMed2006

Physical activity and intestinal gas clearance in patients with bloating.

BACKGROUND: Patients complaining of abdominal bloating have impaired tolerance and clearance of intestinal gas loads. Mild exercise enhances intestinal clearance and prevents retention of intestinal gas loads in healthy subjects. Our aim was to evaluate the putative beneficial effects of physical activity in patients with abdominal bloating. METHODS: In eight patients complaining of bloating, seven with irritable bowel syndrome, and one with functional bloating, according to Rome II criteria, a gas mixture was continuously infused (12 mL/min) into the jejunum for 120 min with simultaneous duodenal lipid perfusion (1 kcal/min). Gas evacuation, perception (0-6 scale), and abdominal girth were measured at 15-min intervals. Paired studies were randomly performed in the supine position during intermittent pedaling (5 min with 3-min rest intervals at 40 rpm and 0.15 kp load) versus rest (as control). RESULTS: During rest, a significant proportion of the gas infused was retained in the gut (45 +/- 9%, P < 0.01 vs basal), but retention was significantly lower during exercise (24 +/- 7%, P < 0.05 vs rest). Gas retention during rest was associated with significant abdominal symptoms (3.6 score; P < 0.01 vs basal), and symptoms also improved during exercise (2.8 score, P < 0.05 vs rest). During the test, patients developed abdominal distension, which was related to the volume of gas retained (r = 0.68, P < 0.05). CONCLUSION: Mild physical activity enhances intestinal gas clearance and reduces symptoms in patients complaining of abdominal bloating.

Adult↗
PubMed2002

Mathematical model of diffusion-limited gas bubble dynamics in unstirred tissue with finite volume.

Models of gas bubble dynamics for studying decompression sickness have been developed by considering the bubble to be immersed in an extravascular tissue with diffusion-limited gas exchange between the bubble and the surrounding unstirred tissue. In previous versions of this two-region model, the tissue volume must be theoretically infinite, which renders the model inapplicable to analysis of bubble growth in a finite-sized tissue. We herein present a new two-region model that is applicable to problems involving finite tissue volumes. By introducing radial deviations to gas tension in the diffusion region surrounding the bubble, the concentration gradient can be zero at a finite distance from the bubble, thus limiting the tissue volume that participates in bubble-tissue gas exchange. It is shown that these deviations account for the effects of heterogeneous perfusion on gas bubble dynamics, and are required for the tissue volume to be finite. The bubble growth results from a difference between the bubble gas pressure and an average gas tension in the surrounding diffusion region that explicitly depends on gas uptake and release by the bubble. For any given decompression, the diffusion region volume must stay above a certain minimum in order to sustain bubble growth.

Air Pressure↗
PubMed1993

The rightward gas vesicle operon in Halobacterium plasmid pNRC100: identification of the gvpA and gvpC gene products by use of antibody probes and genetic analysis of the region downstream of gvpC.

The extreme halophile Halobacterium halobium synthesizes intracellular gas-filled vesicles that confer buoyancy. A cluster of 13 genes on the 200-kb endogenous plasmid pNRC100 has been implicated in the biosynthesis of gas vesicles. Here, we show that two gas vesicle proteins are encoded by genes in the rightward operon, gvpA and gvpC, by Western blotting (immunoblotting) analysis with antibodies directed against LacZ-GvpA and LacZ-GvpC fusion proteins. Our results are consistent with previous data showing that the gvpA gene product is the major gas vesicle protein and demonstrate for the first time that the gvpC gene product is also present in H. halobium gas vesicles. Northern (RNA) blotting analysis showed two RNA species, an abundant 0.35-kb transcript of gvpA and a minor 2.5-kb transcript of gvpAC, and a third gene 3' to gvpAC, named gvpN. The gvpN gene encodes a hypothetical acidic protein with a molecular weight of 39,000 and a nucleotide binding motif. We used a site-directed mutagenesis method involving double recombination in Escherichia coli to insert a kanamycin resistance cassette just beyond the stop codon of gvpN. Introduction of the mutated gene cluster into an H. halobium mutant with a deletion of the entire gas vesicle gene cluster resulted in gas vesicle-positive transformants; this result suggests that gvpN is the last gene of the rightward gas vesicle transcription unit. We discuss the design and utility of the kanamycin resistance cassette for the mutagenesis of other genes in large operons.

Archaeal Proteins↗
PubMed1994

Wild-type gas vesicle formation requires at least ten genes in the gvp gene cluster of Halobacterium halobium plasmid pNRC100.

To study the functions of the 13 gvp genes, gvpMLKJIHGFEDACN, on plasmid pNRC100 of Halobacterium halobium in gas vesicle formation, we carried out linker scanning mutagenesis of the gene cluster. We constructed a 24.5-kb Escherichia coli-H. halobium shuttle plasmid, pFL2, containing the gvp gene cluster and introduced a kanamycin resistance (kappa) cassette into each gene (except for gvpA). Transformation of H. halobium SD109, which had the entire gvp gene cluster deleted, with pFL2 and mutated pFL2 derivatives showed that while the unmutated gene cluster successfully programmed gas vesicle formation, derivatives with insertion of the kappa cassette in any of the gvp genes, except gvpM, did not lead to production of normal gas vesicles. Insertions in gvpL, -K, -J, -I, and -F resulted in a complete block in gas vesicle synthesis, while insertions in gvpH, -G, -E, -D, -C, and -N resulted in greatly reduced gas vesicle synthesis. In most cases, the block in gas vesicle synthesis did not result from polar effects, since similar results were obtained for derivatives of the insertion mutants in which most of the internal portion of the kappa cassette was deleted and only small (15 to 54-bp) insertions remained. The only exceptions were for gvpH and gvpD, where deletion of the internal portion of the kappa insertions resulted in phenotypic reversion. Electron microscopic analysis of the kappa mutants revealed that interruptions of gvpC and gvpN result in the formation of smaller gas vesicle than in the wild type, while interruptions of gvpF, -G, -H, -J, -K, and -L produce no discernible vesicle intermediates. These results indicate the gvpA, -C, and -N, which have the rightward transcriptional orientation, encode structural proteins, with gvpC and gvpN necessary for late stages of vesicle formation, and gvpL, -K, -J, -I, -H, -G, and -F, which have the leftward transcriptional orientation encode proteins involved in early steps in the assembly of gas vesicles.

DNA Transposable Elements↗
PubMed1996

Functional studies of the gvpACNO operon of Halobacterium salinarium reveal that the GvpC protein shapes gas vesicles.

Gas vesicle (Vac) synthesis in Halobacterium salinarium PHH1 involves the expression of the plasmid pHH1-encoded vac (p-vac) region consisting of 14 different gvp genes that are arranged in two clusters, p-gvpACNO and, oriented in the direction opposite to that of gvpA, p-gvpDEFGHIJKLM. The p-gvpACNO region was analyzed at the transcriptional and functional levels in H. salinarium and in Haloferax volcanii transformants containing subfragments of the p-vac region. The p-gvpACNO genes were transcribed as several mRNAs: the 270-nucleotide (nt) p-gvpA transcript, encoding the major structural protein, occurred in large amounts, and minor amounts of three different readthrough transcripts (p-gvpACN, and p-gvpACNO mRNA) were found. In addition, the p-gvpO gene gave rise to two separate mRNA species: a 550-nt mRNA starting at the ATG and spanning the entire reading frame and a 420-nt RNA encompassing the second half of the p-gvpO gene. The requirement of p-gvpC, p-gvpN, and p-gvpO gene expression for gas vesicle synthesis was assessed by transformation experiments using the VAC- species Haloferax volcanii as the recipient. A delta C transformant, harboring the p-vac region with a deletion of the p-gvpC gene, produced large amounts of irregularly shaped gas vesicles. A shape-forming function of p-GvpC was demonstrated by complementation of the delta C transformant with the p-gvpC gene, resulting in wild-type-shaped gas vesicles. In the delta N transformant, the level of gas vesicle synthesis was very low, indicating that the p-GvpN protein is not required for gas vesicle assembly but may enhance gas vesicle synthesis. The p-gvpN deletion did not affect accumulation of p-gvpACO mRNA but reduced the separate p-gvpO transcription. The delta O transformant was Vac- and had a strongly decreased level of p-gvpACN mRNAs, demonstrating that the p-GvpO protein is required for gas vesicle synthesis and may affect transcription of this DNA region.

Archaeal Proteins↗
PubMed1992

Detection of bacterial growth by gas absorption.

When 24 different aerobic organisms were grown in a shaken culture, all were found to first absorb gas from the headspace. In a rudimentary medium, such as tryptic soy broth, 16 of the 24 organisms did not produce gas following the initial gas absorption. We have developed a simple, noninvasive method for detecting both gas absorption and production in multiple culture vials. The time to positivity was compared with that obtained by the BACTEC 460 blood culture system. For nearly all of these organisms, there was no difference. For some of those organisms that did not produce gas, e.g. Staphylococcus epidermidis, Moraxella osloensis, and Neisseria meningitidis, detection by gas absorption was a few hours faster. Gas absorption appears to be a promising technique for a new automated blood culture system because of its simplicity and because medium without special additives can be used to detect organisms that do not produce gas.

Absorption↗
PubMed1999

Patterns of gas and liquid reflux during transient lower oesophageal sphincter relaxation: a study using intraluminal electrical impedance.

BACKGROUND: Belching has been proposed as a major mechanism underlying acid gastro-oesophageal reflux in normal subjects. However, the presence of oesophageal gas has not been measured directly but only inferred from manometry. AIMS: To investigate, using intraluminal electrical impedance, the patterns of gas and liquid reflux during transient lower oesophageal sphincter (LOS) relaxations, the main mechanism of acid reflux in normal subjects. METHODS: Impedance changes associated with the passage of gas were studied in vitro, and in vivo in cats. Oesophageal manometry, pH, and intraluminal electrical impedance measurements were performed in 11 normal subjects after a meal. RESULTS: Gas reflux caused a sudden increase in impedance that propagated rapidly to the proximal oesophagus whereas liquid reflux induced a retrogressively propagated fall in impedance. Impedance showed gas or liquid reflux during most (102/141) transient LOS relaxations. When acid reflux occurred, impedance showed evidence of intraoesophageal retrograde flow of liquid in the majority (78%) of events. Evidence of gas retroflow was found in almost half (47%) of acid reflux episodes. When present together, however, liquid preceded gas on 44% of occasions. Overall, gas reflux occurred as the initial event in only 25% of acid reflux episodes. CONCLUSIONS: These findings suggest that in upright normal subjects, although belching can precipitate acid reflux, most acid reflux occurs as a primary event.

Adolescent↗
PubMed1993

Respiratory symptoms and lung function effects of domestic exposure to tobacco smoke and cooking by gas in non-smoking women in Singapore.

STUDY OBJECTIVES: To investigate the effects of passive exposure to tobacco smoke and gas cooking at home on respiratory symptoms and lung function of non-smoking women. SETTING: Evidence on the effects of passive smoking and exposure to nitrogen dioxide from gas cooking on the respiratory health of adults is limited and variable. Over 97% of women in Singapore do not smoke, and a principal source of indoor air pollution for housewives is passive smoking and gas cooking. DESIGN: This was a cross sectional (prevalence) study of a population based sample of 2868 adults aged 20 to 74 years in Singapore. A structured questionnaire administered by trained interviewers was used to collect data on passive smoking, gas cooking, respiratory symptoms, and other relevant variables. Passive smoking was defined as exposure to cigarette smoke from one or more members of the household who had ever smoked. Gas cooking was defined in terms of the weekly frequency of gas cooking, as well as the frequency with which the respondent's kitchen was filled with heavy cooking fumes (rarely, occasionally, often). Forced expiratory volume in one second (FEV1) was measured by using a portable Micro-spirometer. Multivariate analyses were used to estimate relative odds of association for respiratory symptoms and FEV1 effect, with adjustment for potential confounding variables. PARTICIPANTS: Of a total of 1438 women in the sample, 1282 women who had never smoked provided questionnaire data and 1008 women provided acceptable readings of FEV1 for analysis. MAIN RESULTS: Passive smoking was significantly associated with greater relative odds of usual or chronic cough and phlegm, wheezing, and breathlessness on exertion, as well as lower FEV1. Greater relative odds of respiratory symptoms were also associated with the weekly frequency of gas cooking, although these results were statistically insignificant. Chronic cough and phlegm and breathlessness on exertion, however, were significantly associated with the frequency with which the kitchen was filled with heavy cooking fumes. A lower FEV1 was found in women who cooked frequently (more than thrice a week). CONCLUSION: Domestic exposure to cigarette smoke and gas cooking is associated with increased risks of respiratory symptoms and impairment of lung function in non-smoking women in Singapore.

Adult↗