Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
5
pubmed:dateCreated
1989-9-14
pubmed:abstractText
Alveolar to arterial differences (AaD) may be computed from representative alveolar gas pressures (PA). These are particularly difficult to obtain in patients with chronic airways obstruction (CAO) and severe inhomogeneity of the ventilation/perfusion (VA/Q) ratio. In 25 such patients, using a computerized mass spectrometer, representative values of alveolar gas were obtained: 1. as end-tidal concentrations (ET); 2. using the alveolar air equation with PACO2 derived from Bohr's equation (BE); 3. putting PACO2 = PACO2 into the alveolar air equation to compute ideal O2 alveolar pressure (ID); 4. applying Rahn's definition of "mean" alveolar gas (RD), i.e. taking within each jth breath, the alveolar pressures corresponding to the moment when the instantaneous gas exchange ratio R(t)j equals the overall exchange ratio for that breath Rj. During quiet breathing, the point where R(t)j equals Rj occurred at 71% of tidal volume (VT). Alveolar pressures by BE and RD resulted in similar values (115.5 +/- 6.9 and 115.5 +/- 6.6 mmHg for O2 and 30.3 +/- 5.7 and 30.8 +/- 5.7 mmHg for CO2, respectively), but they were significantly different from those by ET and ID (106.2 +/- 9.5 and 95.6 +/- 13.5 mmHg for O2 and 36.3 +/- 7.7 and 48.2 +/- 11.2 mmHg for CO2, respectively). These findings may be explained considering that PA(BE) and PA(RD) represent both high and low VA/Q units, whereas PA(ET) and PA(ID) represent mainly low VA/Q units. AaDCO2 by RD and BE appeared proportional to the severity of CAO as estimated from VT. Automated techniques make it possible to substitute end-tidal determinations with more accurate estimates either by measuring anatomical dead-space and using Bohr's equation or by applying Rahn's definition.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0903-1936
pubmed:author
pubmed:issnType
Print
pubmed:volume
2
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
451-60
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1989
pubmed:articleTitle
Estimates of mean alveolar gas in patients with chronic airways obstruction.
pubmed:affiliation
CNR Institute of Clinical Physiology, Italy.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't