The humidification of anaesthetic gases: its importance and control.
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Biomedical subjects
Publications and source records attributed to J Chalon.
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Damage to the ciliated cells of the tracheobronchial tree and incidence of postoperative pulmonary complications were measured by point-scoring systems in 202 patients who breathed dry and humidified anesthetic gases for 225 +/- 78 min. The incidence of postoperative pulmonary complications decreased as the humidity of administered anesthetic gases increased from 0 to 32.5 mg H2O/l. A similar relationship was found between the amount of inhaled moisture and the damage to the ciliated epithelium of the tracheobronchial tree. These results appear to indicate that a high inspired humidity is beneficial for operations on normothermic patients, and that cellular damage caused by dryness is a possible contributory factor in the production of the pulmonary atelectasis that follows stoppage of the mucociliary transport system in the immmediate postoperative period.
A computer program was developed to calculate intrapulmonary venous admixture on a Texas Instruments TI 59 programmable calculator. The program incorporates the following characteristics: 1) a correction for saturated water vapor pressure which varies with body temperature; 2) a mathematical model of the standard oxyhemoglobin dissociation curve; and 3) correction factors for shifts of the dissociation curve due to variations in pH and carbon dioxide tension. It also corrects oxygen tensions obtained at electrode temperature to those at patient temperature, and calculates variations of the Bunsen solubility coefficient of oxygen in blood with body temperature.
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A scaled-down version of a modified adult circle system capable of increasing normal humidity output 300% was constructed for pediatric use. The moisture content of the gases leaving the system was tested and found to be superior to that of any pediatric circle system commercially available that does not incorporate an electrically heated water vaporizer.
Allegedly toxic heme pigments have been described in the serum of animals bled to hemorrhagic shock (5,7). In addition, Sears et al. (9), and Braun et al. (1) have shown that the products derived from the degradation of hemoglobin following intravascular hemolysis were toxic (heme carried by hemopexin and albumin). The accumulation of metabolites, caused by the impeded circulation, degrades free hemoglobin into heme pigments and their concentration then reaches a level which exceeds the normal heme-carrying capacity of serum proteins. We have already demonstrated the presence of abnormal heme pigments in clinical cases of shock using scanning spectrophotometry (3). We have endeavored to identify these pigments by serum electrophoresis, and to relate the appearance of some of these compounds to mortality rates. There were no deaths associated with the presence of haptoglobin-hemoglobin alone in serum. As shock deepened and mortality rose, hemopexin-heme and methemalbumin appeared. The highest mortality rate (4 out of 5 cases) was found when both hemopexin-heme and methemalbumin were present. It appears, therefore, that the administration of serum proteins in shock may reduce the toxicity of the products of degradation formed in low-flow states.
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Inverse correlations were established between the percentage of iron-laden macrophages (heart-failure cells), found in the sputum of patients with various types of heart ailment, and cardiac index. Less than 2% iron-laden macrophages were seen when cardiac index was in the region of 3 liter/min/sq mm of body surface area (BSA). This fraction increased to approximately 75% when the cardiac index attained 1 liter/min/sq mm of BSA. Since there was noticeable heterogeneity of data when the cardiac index was below 3 liters/min/sq mm of BSA and above 1 liter/min/sq mm of BSA, it was concluded that a second factor was probably at play: this was the degree of activity of the reticuloendothelial system of the subjects concerned.
Histiocytes counted in smears made from the tracheobronchial washings of 208 patients with malignant melanomas were found to be 3.12 times more numerous than in a control group comparable in sex, age (decades), and smoking habit but without any type of prediagnosed malignant lesion. The discovery of this phenomenon may lead to the development of a new method for the evaluation of therapeutic methods in patients with melanotic lesions. It may open novel pathways for the investigation of cell-mediated immunity in patients with certain forms of malignant disease.
Significantly elevated numbers of iron laden histiocytes have been shown to appear in the tracheobronchial secretions of subjects in hemorrhagic shock and in patients undergoing open heart-surgery during cardiopulmonary bypass (3,4). Abnormal heme pigments have also been demonstrated in the serum of dogs bled to hemorrhagic shock (6) and have been felt to be toxic. Because the ingestion of abnormal heme pigments by histiocytes may be part of a defense mechanism, we have attempted to correlate the percentage of iron laden histiocytes found in the tracheobronchial secretions of patients in hemorrhagic shock (Prussian blue method) with the presence of degradation of products of hemoglobin found in their serum by scanning spectrophotometry. There were, generally speaking, few iron laden histiocytes when hemoglobin degradation was advanced, and always numerous iron laden histiocytes when abnormal heme pigments were absent or spectrophotometric findings revealed minor degrees of degradation. Our findings probably reflect the process in the reticuloendothelial systems which eliminates toxic products accumulating in the circulation in low-flow states.
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Patients with malignant disease are known to have an increased incidence of multinucleation in their tracheobronchial ciliated epithelial cells as compared with controls matched by age, sex and smoking habit. A seasonal relationship of viral inclusion bodies in the cilated epithelium of asymptomatic subjects has also been shown and is not related to age, sex and smoking habit. We have conducted an epidemiologic study to determine the possible relationships between these factors. Smears from 4,150 patients with a wide variety of pathologic conditions were examined for the presence of viral inclusions and multinucleated, ciliated epithelial cells. High degress of multinucleation were observed least frequenctly in the summer both in patients with and without known malignancy. Cytoplasmic inclusion bodies were also seen least frequently in the summer and autumn both in patients with and without know malignancy. In the presence of cancer, multinucleated epithelial cells and inclusion bodies were seen more frequently regardless of the season. When the seasonal incidence of multinucleated cells in 155 smears containing viral inclusion bodies was analyzed, it was found that patients without cancer had the lowest levels of multinucleation in the summer, whereas cancer patients had a depressed incidence of multinucleation in the winter and spring. Respiratory viruses may have a specific effect on the ciliated epithelium of cancer patients.
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Multinucleation of noncancerous ciliated tracheobronchial epithelial cells seen in smears from 412 patients suffering from malignant tumors originating from a wide variety of organs was found to be 2.03 times more frequent than in a control group without prediagnosed malignant disease, matched by age (decades), sex, and smoking habit (p less than 0.0005). Multinucleation involving at least 3% of cells was seen four times more frequently in patients with invasive tumors without known metastases than in controls. Excessive smoking habit in control females as well as site of origin and stage of tumor influenced statistical significance, otherwise unaffected by age, sex, and smoking habit in males. A prospective study is being planned in which incidence and degree of tracheobronchial epithelial multinucleation will be used in conjunction with biochemical tests for the diagnosis of occult cancer.
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