Document Detail


Anatomic dead space cannot be predicted by body weight.
MedLine Citation:
PMID:  18593489     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: Anatomic dead space (also called airway or tracheal dead space) is the part of the tidal volume that does not participate in gas exchange. Some contemporary ventilation protocols, such as the Acute Respiratory Distress Syndrome Network protocol, call for smaller tidal volumes than were traditionally delivered. With smaller tidal volumes, the percentage of each delivered breath that is wasted in the anatomic dead space is greater than it is with larger tidal volumes. Many respiratory and medical textbooks state that anatomic dead space can be estimated from the patient's weight by assuming there is approximately 1 mL of dead space for every pound of body weight. With a volumetric capnography monitor that measures on-airway flow and CO2, the anatomic dead space can be automatically and directly measured with the Fowler method, in which dead space equals the exhaled volume up to the point when CO2 rises above a threshold. METHODS: We analyzed data from 58 patients (43 male, 15 female) to assess the accuracy of 5 anatomic dead space estimation methods. Anatomic dead space was measured during the first 10 min of monitoring and compared to the estimates. RESULTS: The coefficient of determination (r2) between the anatomic dead space estimate based on body weight and the measured anatomic dead space was r2 = 0.0002. The mean +/- SD error between the body weight estimate and the measured dead space was 60 +/- 54 mL. CONCLUSIONS: It appears that the anatomic dead space estimate methods were sufficient when used (as originally intended) together with other assumptions to identify a starting point in a ventilation algorithm, but the poor agreement between an individual patient's measured and estimated anatomic dead space contradicts the assumption that dead space can be predicted from actual or ideal weight alone.
Authors:
Lara M Brewer; Joseph A Orr; Nathan L Pace
Related Documents :
15713329 - Carcinogen specific dosimetry model for passive smokers of various ages.
10757619 - Validation of bio-impedance spectroscopy: effects of degree of obesity and ways of calc...
3697549 - A computerized method for measuring respiratory mechanics during mechanical ventilation.
10829399 - Effect of generator nonlinearities on the accuracy of respiratory impedance measurement...
22910679 - Closing the gap between clinic and cage: sensori-motor and cognitive behavioural testin...
2793729 - Minimization of lung pressure swings during high-frequency ventilation: a model.
21120819 - Sensitivity analysis for multiple right censoring processes: investigating mortality in...
20614689 - Pharmacokinetic/pharmacodynamic model-based combination therapy approach to target anti...
24056349 - Deviations from bilinearity in multivariate voltammetric calibration models.
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Respiratory care     Volume:  53     ISSN:  0020-1324     ISO Abbreviation:  Respir Care     Publication Date:  2008 Jul 
Date Detail:
Created Date:  2008-07-02     Completed Date:  2008-11-18     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7510357     Medline TA:  Respir Care     Country:  United States    
Other Details:
Languages:  eng     Pagination:  885-91     Citation Subset:  IM    
Affiliation:
Department of Anesthesiology, University of Utah Health Sciences Center, Salt Lake City, Utah, USA. lbrewer@abl.med.utah.edu
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:
Adolescent
Adult
Aged
Aged, 80 and over
Body Weight / physiology*
Capnography
Female
Humans
Male
Middle Aged
Prognosis
Respiration, Artificial / methods,  standards
Respiratory Dead Space / physiology*
Respiratory Distress Syndrome, Adult / diagnosis,  physiopathology*,  therapy
Severity of Illness Index
Comments/Corrections
Comment In:
Respir Care. 2008 Jul;53(7):860-1   [PMID:  18593486 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  An analysis of features of respiratory therapy departments that are avid for change.
Next Document:  Spirometric correlates of dyspnea improvement among emergency department patients with chronic obstr...