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The difficulty of raising the arterial Po2 having been established, it seems of little value to expose patients to the hazards of oxygen toxicity10 to gain a few millimeters' increase in the arterial P02. Arterial oxygen pressures of 60 were well tolerated by young, healthy combat casualties.3 Atelectasis is generally assumed to be the predominant factor responsible for the ventilation-perfusion imbalance. Literally, this is an example of "collapsed airlessness," such an airless alveolus distal to a mucous obstruction of a terminal bronchiole. Other examples of airlessness include alveoli filled with edema fluid, detritus, leukocytes, or retained secretions. Good ventilation and vigorous endotracheal suctioning will help to clear the aveoli of this material. An alveolus may be partially filled with fluid and yet prone to collapse. This paradox may be explained by Laplace's law, which states that the tension in the wall of a distensible sphere is proportional to the radius and the pressure in the lumen (T=Pxr). It follows, therefore, assuming a constant pressure in the lumen, that a decrease in radius will lead to rather sudden collapse at a critical, closing radius, owing to the inability to maintain sufficient tension on the wall to insure an inflated state. As interstitial fluid accumulates (Fig. 3), the radius decreases making collapse more likely. Simultaneously, surfactant is being inactivated by the fluid accnmulating in the alveolus,11 raising the surface tension at the tissue-air interface, also enhancing collapse. A method of maintaining alveoli with a large enough radius so that available tension on the wall is sufficient to maintain inflation has been applied successfully by Ashbaugh.12 Expiration is normally accomplished passively. If forced to expire against resistance, patients will increase their functional residual capacity (Fig. 4), storing more elastic energy in the chest wall to accomplish expiration. By incorporating this measure with positive pressure ventilation, alveoli are maintained in a hyperinflated state, T = P x r La Place's Law Fig. 3. Interstitial edema in the alveolus on the right decreases the radius and makes collapse more likely. and even at end expiration, the alveolar radius is sufficient to maintain wall tension above the closing level. In spite of the higher intrathoracic pressures resulting from this technique of ventilation and the associated theoretical reduction in venous return, Ashbaugh was unable to document a significant reduction in cardiac output. Pulmonary capillary perfusion is normally governed in part by alveolar oxygen tension,13 an important mechanism to prevent capillary-alveolar perfusion abnormalities. Thus as airless alveoli develop a low arterial Po2, the capillary perfusion of these alveoli is decreased, with preferential redistribution of pulmonary arterial blood to better ventilated por- > H < A < W r A w z Tidal volume Functional residual capacity Increased expiratory resistance I Tidal volume Functional residual capacity Fig. 4. Increase in the functional residual capacity after institution of expiratory resistance prevents atelectasis. March 1972, NCMJ 211
Object Description
Rating | |
Fixed Title * | NCHH-17: North Carolina Medical Journal [1940-2001] |
Document Title | North Carolina Medical Journal [1940-2001] |
Subject Topical Other | Public Health -- Periodicals.; Physicians -- North Carolina -- Directory.; Societies, Medical -- North Carolina -- Periodicals. |
Description | Includes Transactions of the Society, -1960; 1961- , Transactions issued separately, bound in.; Includes Transactions of the auxiliary to the Medical Society of the State of North Carolina and Proceedings of the North Carolina Public Health Association. Official organ of the Medical Society of the State of North Carolina, 1940-May 1972; of the North Carolina Medical Society, June 1972-. Vols. for 1940-May 1972 published by the Medical Society of the State of North Carolina; June 1972- by the North Carolina Medical Society. |
Contributor | Medical Society of the State of North Carolina. Transactions.; Medical Society of the State of North Carolina.; North Carolina Medical Society.; North Carolina Medical Society. Transactions.; North Carolina Public Health Association. Proceedings. |
Publisher | [Winston-Salem] : North Carolina Medical Society [etc.], 1940- |
Repository | University of North Carolina at Chapel Hill. Health Sciences Library. |
Host | University of North Carolina at Chapel Hill |
Date | 1972 |
Identifier | NCHH-17-033 |
Form General | Periodicals |
Language | English |
Rights | This item is part of the North Carolina History of Health Digital Collection. Some materials in the Collection are protected by U.S. copyright law. This item is presented by the Health Sciences Library of the University of North Carolina at Chapel Hill for research and educational purposes. It may not be republished or distributed without permission of the Health Sciences Library. |
Digital Collection | North Carolina History of Health Digital Collection |
Sponsor | The North Carolina History of Health Digital Collection is an open access publishing initiative of the Health Sciences Library of the University of North Carolina at Chapel Hill. Financial support for the initiative was provided in part by a multi-year NC ECHO (Exploring Cultural Heritage Online) digitization grant, awarded by the State Library of North Carolina, and funded through the Library Services and Technology Act (LSTA). |
Volume Number | 33 |
Health Discipline | Medicine |
Digital Format | JPEG 2000 |
Print / Download PDF Version | http://archives.hsl.unc.edu/nchh/nchh-17/nchh-17-033.pdf |
Document Sort | all; nchh-17 |
Volume Link | http://dc.lib.unc.edu/cdm/search/collection/nchh/field/identi/searchterm/NCHH-17-033 |
Title Link | http://dc.lib.unc.edu/cdm/search/collection/nchh/field/documa/searchterm/NCHH-17 |
Catalog Record link | http://search.lib.unc.edu/search?R=UNCb1306322 |
Revision History | done |
Description
Fixed Title * | Page 211 (images) |
Document Title | North Carolina Medical Journal [1940-2001] |
Subject Topical Other | Public Health -- Periodicals.; Physicians -- North Carolina -- Directory.; Societies, Medical -- North Carolina -- Periodicals. |
Description | Includes Transactions of the Society, -1960; 1961- , Transactions issued separately, bound in.; Includes Transactions of the auxiliary to the Medical Society of the State of North Carolina and Proceedings of the North Carolina Public Health Association. Official organ of the Medical Society of the State of North Carolina, 1940-May 1972; of the North Carolina Medical Society, June 1972-. Vols. for 1940-May 1972 published by the Medical Society of the State of North Carolina; June 1972- by the North Carolina Medical Society. |
Contributor | Medical Society of the State of North Carolina. Transactions.; Medical Society of the State of North Carolina.; North Carolina Medical Society.; North Carolina Medical Society. Transactions.; North Carolina Public Health Association. Proceedings. |
Publisher | [Winston-Salem] : North Carolina Medical Society [etc.], 1940- |
Repository | University of North Carolina at Chapel Hill. Health Sciences Library. |
Host | University of North Carolina at Chapel Hill |
Date | 1972 |
Identifier | NCHH-17-033-0149 |
Form General | Periodicals |
Page Type | all; all images; diagram; all images; chart/table; article |
Language | English |
Rights | This item is part of the North Carolina History of Health Digital Collection. Some materials in the Collection are protected by U.S. copyright law. This item is presented by the Health Sciences Library of the University of North Carolina at Chapel Hill for research and educational purposes. It may not be republished or distributed without permission of the Health Sciences Library. |
Filename | ncarolinamed331972medi_0149.jp2 |
Digital Collection | North Carolina History of Health Digital Collection |
Sponsor | The North Carolina History of Health Digital Collection is an open access publishing initiative of the Health Sciences Library of the University of North Carolina at Chapel Hill. Financial support for the initiative was provided in part by a multi-year NC ECHO (Exploring Cultural Heritage Online) digitization grant, awarded by the State Library of North Carolina, and funded through the Library Services and Technology Act (LSTA). |
Volume Number | 33 |
Issue Number | 3 |
Page Number | 211 |
Health Discipline | Medicine |
Full Text | The difficulty of raising the arterial Po2 having been established, it seems of little value to expose patients to the hazards of oxygen toxicity10 to gain a few millimeters' increase in the arterial P02. Arterial oxygen pressures of 60 were well tolerated by young, healthy combat casualties.3 Atelectasis is generally assumed to be the predominant factor responsible for the ventilation-perfusion imbalance. Literally, this is an example of "collapsed airlessness" such an airless alveolus distal to a mucous obstruction of a terminal bronchiole. Other examples of airlessness include alveoli filled with edema fluid, detritus, leukocytes, or retained secretions. Good ventilation and vigorous endotracheal suctioning will help to clear the aveoli of this material. An alveolus may be partially filled with fluid and yet prone to collapse. This paradox may be explained by Laplace's law, which states that the tension in the wall of a distensible sphere is proportional to the radius and the pressure in the lumen (T=Pxr). It follows, therefore, assuming a constant pressure in the lumen, that a decrease in radius will lead to rather sudden collapse at a critical, closing radius, owing to the inability to maintain sufficient tension on the wall to insure an inflated state. As interstitial fluid accumulates (Fig. 3), the radius decreases making collapse more likely. Simultaneously, surfactant is being inactivated by the fluid accnmulating in the alveolus,11 raising the surface tension at the tissue-air interface, also enhancing collapse. A method of maintaining alveoli with a large enough radius so that available tension on the wall is sufficient to maintain inflation has been applied successfully by Ashbaugh.12 Expiration is normally accomplished passively. If forced to expire against resistance, patients will increase their functional residual capacity (Fig. 4), storing more elastic energy in the chest wall to accomplish expiration. By incorporating this measure with positive pressure ventilation, alveoli are maintained in a hyperinflated state, T = P x r La Place's Law Fig. 3. Interstitial edema in the alveolus on the right decreases the radius and makes collapse more likely. and even at end expiration, the alveolar radius is sufficient to maintain wall tension above the closing level. In spite of the higher intrathoracic pressures resulting from this technique of ventilation and the associated theoretical reduction in venous return, Ashbaugh was unable to document a significant reduction in cardiac output. Pulmonary capillary perfusion is normally governed in part by alveolar oxygen tension,13 an important mechanism to prevent capillary-alveolar perfusion abnormalities. Thus as airless alveoli develop a low arterial Po2, the capillary perfusion of these alveoli is decreased, with preferential redistribution of pulmonary arterial blood to better ventilated por- > H < A < W r A w z Tidal volume Functional residual capacity Increased expiratory resistance I Tidal volume Functional residual capacity Fig. 4. Increase in the functional residual capacity after institution of expiratory resistance prevents atelectasis. March 1972, NCMJ 211 |
Digital Format | JPEG 2000 |
Print / Download PDF Version | http://archives.hsl.unc.edu/nchh/nchh-17/nchh-17-033.pdf |
Document Sort | all; nchh-17 |
Article Title | Post-Traumatic Pulmonary Insufficiency: A Physiologic Basis For Treatment |
Article Author | H. J. Proctor |
Volume Link | http://dc.lib.unc.edu/cdm/search/collection/nchh/field/identi/searchterm/NCHH-17-033 |
Title Link | http://dc.lib.unc.edu/cdm/search/collection/nchh/field/documa/searchterm/NCHH-17 |
Catalog Record link | http://search.lib.unc.edu/search?R=UNCb1306322 |
Revision History | done |
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