Changes in Intrapulmonary Shunting with Administration of 100 Percent Oxygen

Costa

et al. 2013

Critical Care Medicine

Section: Definitionsmentioning

confidence: 99%

mentioning

confidence: 99%

Bedside Estimation of Nonaerated Lung Tissue Using Blood Gas Analysis*

Costa

et al. 2013

Critical Care Medicine

Am J Respir Crit Care Med

“…It is difficult to explain why patients initially meeting AECC ARDS criteria would fail to meet these criteria on standard ventilator settings 24 hours later, although it is well established that changes in PEEP and FI O 2 alter the Pa O 2 /FI O 2 in lung-injured patients (2)(3)(4)(5)(6)(7). At an FI O 2 of 1.0, the effects of ventilation/perfusion mismatch are eliminated and true shunt is measured (4,5).…”

Section: Impact Of Fi O 2 and Peepmentioning

confidence: 99%

“…This current definition may not be adequate for inclusion of patients into clinical trials focusing on the management of ARDS. The Pa O 2 /FI O 2 in most patients can be easily manipulated by altering PEEP and FI O 2 (2)(3)(4)(5), potentially including in clinical trials patients with marked variability in lung injury and potentially different outcomes. There have been two reports (8,9) on the effect of standard ventilator settings on Pa O 2 /FI O 2 and fulfillment of definitions of ARDS/ALI.…”

mentioning

confidence: 99%

An Early PEEP/Fi_O₂ Trial Identifies Different Degrees of Lung Injury in Patients with Acute Respiratory Distress Syndrome

Villar

Pérez‐Méndez²,

López³

et al. 2007

266

200

“…They found that P(A-a)C>2 increased with increase in FIO2. Recently, Shapiro et al [14] studied 82 intubated patients in the medical, surgical, and neurosurgical in tensive care units. They found that as the fractional concentration of oxygen in the inspired gas increased to 1.0, intrapulmonary shunting increased in 132 of 140 measurements, decreased in 7 and re mained unchanged in 1 measurement.…”

Section: Discussionmentioning

confidence: 99%

Effects of Breathing Pattern and Oxygen upon the Alveolar Arterial Oxygen Pressure Difference in Lung Disease

Ploysongsang¹,

Wiltse²

1985

Respiration

It was suggested by analysis of theoretical lung models that low V/Q units are unstable and can be converted into shunt by breathing O₂. We tested this theory in 21 subjects with various lung diseases (mostly chronic obstructive pulmonary disease) by having them breathe O₂. We also increased the tidal volumes in these patients to see whether this maneuver could prevent the development of shunt. We found that mean P(A-a)O₂ increased from 30 ± 2.8 (mean ± SEM) Torr breathing room air to 135 ± 20.7 Torr breathing O₂ for 10 min (p < 0.0001), to 124 ± 20.4 Torr breathing O₂ for 20 min (p < 0.0001), and to 125 ± 19.0 Torr breathing oxygen with inspiratory capacity breaths (p < 0.0001). The corresponding shunt increased from about 2.8% of the cardiac output to 7.9 ± 1.01, 7.3 ± 1.03 and 7.3 ± 0.98%, respectively. We conclude that: (1) breathing pure oxygen can convert low V/Q units to shunt, hence measurement of P(A-a)O₂ and shunt by oxygen technique will overestimate the actual values; (2) 10 min of oxygen breathing will cause complete atelectasis of low V/Q units, and (3) increased tidal volume does not prevent absorptive atelectasis.