scholarly journals Calculation of Physiologic Dead Space: Comparison of Ventilator Volumetric Capnography to Measurements by Metabolic Analyzer and Volumetric CO2 Monitor

2012 ◽  
Vol 58 (7) ◽  
pp. 1143-1151 ◽  
Author(s):  
Mark S Siobal ◽  
Hannah Ong ◽  
Josephine Valdes ◽  
Julin Tang
Keyword(s):  
Dead Space ◽  
Volumetric Capnography ◽  
Physiologic Dead Space

A New Equal Area Method to Calculate and Represent Physiologic, Anatomical, and Alveolar Dead Spaces

2006 ◽  
Vol 104 (4) ◽  
pp. 696-700 ◽  
Author(s):  
Yongquan Tang ◽  
Martin J. Turner ◽  
A Barry Baker
Keyword(s):  
Carbon Dioxide ◽  
Dead Space ◽  
Graphical Method ◽  
Mean Difference ◽  
Equal Area ◽  
Area Method ◽  
Physiologic Dead Space ◽  
Anatomical Dead Space ◽  
The Mean ◽  
The Difference

Background Physiologic dead space is usually estimated by the Bohr-Enghoff equation or the Fletcher method. Alveolar dead space is calculated as the difference between anatomical dead space estimated by the Fowler equal area method and physiologic dead space. This study introduces a graphical method that uses similar principles for measuring and displaying anatomical, physiologic, and alveolar dead spaces. Methods A new graphical equal area method for estimating physiologic dead space is derived. Physiologic dead spaces of 1,200 carbon dioxide expirograms obtained from 10 ventilated patients were calculated by the Bohr-Enghoff equation, the Fletcher area method, and the new graphical equal area method and were compared by Bland-Altman analysis. Dead space was varied by varying tidal volume, end-expiratory pressure, inspiratory-to-expiratory ratio, and inspiratory hold in each patient. Results The new graphical equal area method for calculating physiologic dead space is shown analytically to be identical to the Bohr-Enghoff calculation. The mean difference (limits of agreement) between the physiologic dead spaces calculated by the new equal area method and Bohr-Enghoff equation was -0.07 ml (-1.27 to 1.13 ml). The mean difference between new equal area method and the Fletcher area method was -0.09 ml (-1.52 to 1.34 ml). Conclusions The authors' equal area method for calculating, displaying, and visualizing physiologic dead space is easy to understand and yields the same results as the classic Bohr-Enghoff equation and Fletcher area method. All three dead spaces--physiologic, anatomical, and alveolar--together with their relations to expired volume, can be displayed conveniently on the x-axis of a carbon dioxide expirogram.

Postural variations in dead space and CO2 gradients breathing air and O2

1962 ◽  
Vol 17 (3) ◽  
pp. 417-420 ◽  
Author(s):  
C. P. Larson ◽  
J. W. Severinghaus
Keyword(s):  
Dead Space ◽  
Normal Limit ◽  
Healthy Adult ◽  
Sitting Position ◽  
Alveolar Dead Space ◽  
Vascular Bed ◽  
Postural Changes ◽  
Physiologic Dead Space ◽  
Pulmonary Vascular Bed

Effects of postural changes on anatomic and physiologic dead space and arterial-alveolar CO2gradients were studied in 11 healthy, adult subjects breathing air and O2. Results indicate that, on moving from the supine to the sitting position, Vads and Vpds increased by corresponding amounts (42 and 37 ml) with no increase in alveolar dead space or volume of lung which is nonperfused. Arterial-alveolar CO2 gradients were unaffected by posture, but more than doubled with O2 breathing, suggesting that O2 may relax the pulmonary vascular bed and diminish perfusion of highest lung segments. Isoproterenol aerosol (0.5%) produced significant bronchodilatation (27 ml increase in Vads), but only small and inconsistent increases in alveolar dead space and CO2 gradients. The PDS/Vt ratio in these subjects while sitting, breathing air, averaged 31 ± 6%, which is higher than the normally accepted value of 30%. As a result, the upper normal limit for PDS/Vt has been increased to 40% in our laboratories. Submitted on January 22, 1962

Validation of Bohr dead space measured by volumetric capnography: reply to Graf

2011 ◽  
Vol 37 (8) ◽  
pp. 1397-1398 ◽  
Author(s):  
Gerardo Tusman ◽  
Fernando Suarez Sipmann ◽  
Joao B. Borges ◽  
Göran Hedenstierna ◽  
Stephan H. Bohm
Keyword(s):  
Dead Space ◽  
Volumetric Capnography

Circulation and physiologic dead space changes on controlling the ventilation of dogs

1966 ◽  
Vol 21 (6) ◽  
pp. 1855-1859 ◽  
Author(s):  
K. Suwa ◽  
J. Hedley-Whyte ◽  
H. H. Bendixen
Keyword(s):  
Dead Space ◽  
Physiologic Dead Space
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