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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adequate oxygenation of apneic subjects can be maintained by constant flow transtracheal oxygen (TTO), but this method alone is associated with hypercapnia. The "bellows" effect of external chest compressions (ECC) might prevent this problem if the airway were kept open by TTO. In dogs, we investigated the utility of TTO delivered at 15 L/min by a percutaneously placed intratracheal catheter, plus ECC (TTO/ECC) as an alternative method of ventilation during CPR. TTO was applied to anesthetized, paralyzed dogs in normal sinus rhythm (NSR) at various rates of ECC and during ventricular fibrillation (VF) at an ECC rate of 80/min. During NSR and VF, hypercapnia did not develop and arterial oxygen saturations were maintained above 90 percent. During NSR, the PaCO2 decreased and the pH increased as the ECC rate increased. For many of the animals, coronary perfusion pressure remained above 20 mm Hg during VF, suggesting that these animals could be resuscitated to NSR. In another phase, after 15 min of VF using TTO/ECC, seven of nine animals were defibrillated. We conclude that ventilatory and hemodynamic support adequate to permit successful resuscitation to NSR is provided by the combination of TTO/ECC to apneic dogs during VF.
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PMID:Continuous transtracheal oxygen delivery during cardiopulmonary resuscitation. An alternative method of ventilation in a canine model. 249 66

Thirty-five patients presenting to the emergency department in cardiopulmonary arrest had simultaneous measurement of central venous (cv) and arterial (a) blood gases during CPR with a pneumatic chest compressor and ventilator. The mean cv, arterial pH, and PCO2 values were markedly different (P less than .001). The mean pH gradient (pHa - pHcv) was .31 +/- .10 units and the mean PCO2 gradient (PcvCO2 - PaCO2) was 60.5 +/- 23.6 torr. This selective venous hypercarbia is probably due to a cardiac output that is inadequate to eliminate the CO2 produced from both residual aerobic metabolism and the buffering of anaerobically produced lactic acid. Central venous blood gases are probably a better reflection of actual tissue environment during prolonged cardiac arrest than are arterial blood gases.
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PMID:Selective venous hypercarbia during human CPR: implications regarding blood flow. 310 67

The venous-arterial PCO2 gradient may increase in certain low-flow states, such as CPR and canine endotoxemia. To determine whether venous hypercarbia also occurs in hemorrhagic shock, we studied 12 anesthetized, mechanically ventilated dogs. We performed laparotomies on the animals, inserting catheters into their renal, superior mesenteric, and external iliac veins. Flow in the corresponding arteries were determined using electromagnetic flow probes. The dogs were randomized into a control group (n = 6), and a hemorrhagic shock group (n = 6) which was bled to a mean arterial pressure of 45 to 50 mm Hg and maintained at this pressure for the 6-h study. The results demonstrated a significant (p less than .05) increase in lactate and venous-arterial PCO2 gradient systemically and in all three regional beds. A significant decrease of venous blood pH accompanied these changes which are consistent with our previous findings in low-flow, canine endotoxemia. We conclude that venous hypercarbia is a nonspecific phenomenon, common to low-flow states. The increased CO2 represents both an increased CO2 production and a decreased removal, secondary to low-flow.
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PMID:Venous hypercarbia in canine hemorrhagic shock. 310 60

The American Heart Association's current standards for CPR indicate that acid-base therapy should be guided by measurements of arterial blood gases. However, we have discovered a striking discrepancy between arterial and venous blood gases during CPR: severe venous hypercarbia and acidosis may coexist with simultaneous arterial alkalosis. Arterial blood gases during CPR, therefore, may not accurately reflect the acid-base status of mixed venous blood and thus may fail to indicate systemic acid-base status.
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PMID:Arterial blood gases fail to reflect acid-base status during cardiopulmonary resuscitation: a preliminary report. 405 33

In the United States debate continues about the necessity of ventilation during CPR because of fear of contracting infectious diseases. Three questions will be considered in this article. First, is ventilation necessary for the treatment of cardiac arrest? Second, is mouth-to-mouth ventilation any better than no ventilation at all? Third, are other techniques of ventilation as effective or more effective than mouth-to-mouth ventilation during basic life support CPR? Although research is still inconclusive with regard to the need for ventilation during CPR, recent findings have clarified the effect of ventilation during low blood flow states and how ventilation influences resuscitation. Ventilation affects oxygenation, carbon dioxide elimination, and pH during times of low rates of blood flow. Ventilation may be unnecessary during the first few minutes of CPR. Under conditions of prolonged, untreated cardiac arrest, ventilation during CPR affects return of spontaneous circulation. Isolated hypoxemia and hypercarbia independently have adverse effects on survival of cardiac arrest. Because ventilation with exhaled gas contains as much as 4% CO2 and less oxygen than air, it may have adverse effects during CPR. Spontaneous gasping may provide sufficient ventilation during CPR. Chest compression alone provides some pulmonary ventilation and gas exchange. Active chest compression-decompression may improve gas exchange better than does standard chest compression. Other forms of manual ventilation may also have a role in CPR.
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PMID:Reassessing the need for ventilation during CPR. 862 77