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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Modarreszadeh and Bruce (J. Appl. Physiol. 76: 2765-2775, 1994) proposed that continuous random disturbances in arterial PCO2 are more likely to elicit ventilatory oscillation patterns that mimic periodic breathing in normoxia than in hyperoxia. To test this hypothesis experimentally, in nine awake humans we applied pseudorandom binary inspired CO2 fraction stimulation in normoxia and hyperoxia to derive the closed-loop and open-loop ventilatory responses to a brief CO2 disturbance in terms of impulse responses and transfer functions. The closed-loop impulse response has a significantly higher peak value [0.143 +/- 0.071 vs. 0.079 +/- 0.034 (SD) l . min-1 . 0.01 l CO2-1, P = 0.014] and a significantly shorter 50% response duration (42.7 +/- 13.3 vs. 72.3 +/- 27.6 s, P = 0.020) in normoxia than in hyperoxia. Therefore, the ventilatory responses to transient CO2 disturbances are less damped (but generally not oscillatory) in normoxia than in hyperoxia. For the closed-loop transfer function, the gain in normoxia increased significantly (P < 0.0005), while phase delay decreased significantly (P < 0.0005). The gain increased by 108.5, 186.0, and 240.6%, while phase delay decreased by 26.0, 18.1, and 17.3%, at 0. 01, 0.03, and 0.05 Hz, respectively. Changes in the same direction were found for the open-loop system. Generally, an oscillatory ventilatory response to a small transient CO2 disturbance is unlikely during wakefulness. However, changes in parameters that lead to additional increases in chemoreflex loop gain are more likely to initiate oscillations in normoxia than in hyperoxia.
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PMID:Ventilatory stability to transient CO2 disturbances in hyperoxia and normoxia in awake humans. 926 42

Clinically significant myocardial abnormalities (e.g., arrhythmias, S-T elevation) occur in patients with mild-to-severe carbon monoxide (CO) poisoning. We enhanced our previous whole body model [Bruce, E. N., M. C. Bruce, and K. Erupaka. Prediction of the rate of uptake of carbon monoxide from blood by extravascular tissues. Respir. Physiol. Neurobiol. 161(2):142-159, 2008] by adding a cardiac compartment (containing three vascular and two tissue subcompartments differing in capillary density) to predict myocardial carboxymyoglobin (MbCO) and oxygen tensions (P(c)O2) for several CO exposure regimens at rest and during exercise. Model predictions were validated with experimental data in normoxia, hypoxia, and hyperoxia. We simulated exposure at rest to 6462 ppm CO (10 min) and to 265 ppm CO (480 min), and during three levels of exercise at 20% HbCO. We compared responses of carboxyhemoglobin (HbCO), MbCO and P(c)O2 to estimate the potential for myocardial injury due to CO hypoxia. Simulation results predict that during CO exposures and subsequent therapies, cardiac tissue has higher MbCO levels and lower P(c)O2's than skeletal muscle. CO exposure during exercise further decreases P(c)O2 from resting levels. We conclude that in rest and moderate exercise, the myocardium is at greater risk for hypoxic injury than skeletal muscle during the course of CO exposure and washout. Because the model can predict CO uptake and distribution in human myocardium, it could be a tool to estimate the potential for hypoxic myocardial injury and facilitate therapeutic intervention.
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PMID:Prediction of extravascular burden of carbon monoxide (CO) in the human heart. 1983 11