Lung Volumes in Diffuse Obstructive Pulmonary Syndromes

Young, Allan C.; Martin, C. J.; Tsunoda, Shinichiro

doi:10.1172/jci107656

Cited by 6 publications

(2 citation statements)

References 23 publications

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“…an expired volume composition not contaminated 1 by dead space, was satisfied in our patients. At any rate, even in the case when the dead space has not been completely washed out [9,10], the curves of figures 2 and 3 indicate that its contribution to the expiratc may be very small at R(t).=R.. Since at this point 320 ml , i.e.…”

Section: Discussionmentioning

confidence: 90%

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Estimates of mean alveolar gas in patients with chronic airways obstruction

Giannella-Neto¹,

Paoletti²,

Fornai³

et al. 1989

Eur Respir J

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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.

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Section: Discussionmentioning

confidence: 90%

“…Stratified diffusive ventilation may add to this unevenness [1,4,5). During tidal breathing, sampling of alveolar gas is dependent on the size of VT [6,7,8], anatomical dead space [9,10], and asynchronous emptying of air spaces [11]. All these conditions influence to various degrees the methods used for obtaining alveolar gas concentrations.…”

mentioning

confidence: 99%