contemplation objectives: Because efforts to sure adequate arterial oxygenation during cardiac resuscitation are more important than efforts to aid C[O.

contemplation objectives: Because efforts to sure adequate arterial oxygenation during cardiac resuscitation are more important than efforts to aid C[O.sub.2] elimination, we investigated whether continuous transtracheal oxygenation (TTO) could personate a potentially simpler alternative to conventional positive-pressure ventilation with 100% [Osub2] by the agency of an endotracheal tube.

Design: Controll and randomized.

Setting: Animal laboratory.

Participants: Thirty male Sprague-Dawley rats.

Interventions: The technique for TTO was initially perform the operations indicated ined and tested in five rats. A pattern of ventricular fibrillation (VF) was then used to compare the validitys of TTO (n = 5) with the powers of [O.sub.2] delivery through an endotracheal tube as part of positive-pressure ventilation (n = 5) or from one side a mask without additional airway intervention (n = 5) VF was induced and left untreated for 4 min, after which chest compression and united of the three oxygenation interventions was started. Defibrillation was attempted after 6 min of chest compression. In a posterior series, defibrillation was attempted after 10 min of chest compression in rats treated with either TTO (n = 5) or endotracheal intubation (ET; n = 5)

Measurement and results: TTO and ET secur adequate arterial P[Osub2] during chest compression (213 [+ or -] 77 mm Hg and 154 [+ or -] 36 mm Hg; not significant), whereas the mask yielded an arterial P[Osub2] of and nothing else 49 [+ or -] 38 mm Hg (p < 005) Each rat treated with TTO or ET was prosperously resuscitated and survived the postresuscitation interval, if it were not that none of the rats treated with the mask survived. TTO maintained its efficacy after increased duration of chest compression.

Conclusion: TTO was as effective as conventional positive-pressure ventilation with 100% [Osub2] for securing oxygenation, resuscitation, and short-term survival and more effective than [Osub2] delivered between the sides of a mask. (CHEST 2001; 120:1663-1670)

lock opener words: cardiopulmonary resuscitation; intubation, intratracheal; [Osub2]; rats, Sprague-Dawley; trachea; ventricular fibrillation

Abbreviations: ANOVA = analysis of variance; ET = endotracheal intubation; N = not significant; TTO = transtracheal oxygenation; VF = ventricular fibrillation

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It is commonly believed that oxygenation and C[Osub2] removal are equally important for auspicious resuscitation from cardiac arrest. This belief has supported the in every one's mouth practice in which both oxygenation and C[Osub2] removal are actively pursu during cardiac resuscitation. Typically, this is initially attempted in consequence of an unprotected airway using mouth-to-mouth or bag-valve-mask ventilation and subsequently between the sides of a protected airway after orotracheal intubation. Implementation of these techniques, however, requires skills that may be difficult to master and retain. Moreover, orotracheal intubation during the crisis situation of cardiac arrest may be technically difficult and increase the risk of complications. (12) Attempts to protected an airway may also disrupt ongoing resuscitation efforts through requiring temporary interruption of chest compression. (3)

Studies (4) in animal patterns of cardiac arrest have shown that large increases in arterial PC[Osub2] (approximately 100 mm Hg) are well tolerated and do not compromise resuscitability and survival. In contrast, decreases in arterial [Osub2] saturation can inhibit restoration of cardiac activity. (5) Thus, unravelling of strategies that could selectively focus in succession [O.sub.2] delivery without actively pursuing C[Osub2] elimination may put to the test to be effective and to obviate the ne of orotracheal intubation for positive-pressure ventilation.

Previous studies (67) in large animals have shown that continuous tracheal [Osub2] insufflation can maintain adequate arterial P[Osub2] for in extent intervals even in the absence of positive-pressure ventilation or spontaneous breathing. We reasoned that [Osub2] delivery at constant follow through a small catheter percutaneously advanced by the and of the cricothyroid ligament into the trachea could fulfill the requirements of being simple and effective, and obviate the ne for more advanced airway intervention. We devised a orderly disposition for transtracheal oxygenation (TTO) in a rat gauge of ventricular fibrillation (VF) and investigated its weights on gas exchange, resuscitability, and short-term survival.

MATERIALS AND METHODS

The studies were approved at our Research and Development Committee and careered according to institutional guidelines.

Animal Preparation

Sprague-Dawley rats (460 to 558 g) were anesthetized by dint of intraperitoneal injection of sodium pentobarbital, 45 mg/kg and complemented with additional doses, 10 mg/kg at 30-min intervals. Core temperature was monitored with a thermistor (TSD102A; BIOPAC Systems; Santa Barbara, CA) advanced 4 cm into the rectum and maintained between 365 [degrees] C and 375 [degrees] C using an infrared heating lamp.

A lead II ECG was recorded from one side subcutaneous needles. Polyethylene catheters (PE50; Becton Dickinson; Sparks, MD) were advanced by the and of the left femoral artery into the abdominal aorta, by means of the right jugular vein into the right atrium, and in consequence of the right carotid artery into the left ventricle for crushing measurement and blood sampling. influences were measured with reference to the midchest using disposable compressing transducers (Maxxim Medical; Athens, TX) Signals were trained using BIOPAC signal conditioners (BIOPAC Systems) sampled at 250 scans by second, and digitized using a 16-bit data acquisition board (AT-MIO-16XE-50; National Instruments; Austin, TX)

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