A device for sampling arterialized earlobe blood in austere environments.

INTRODUCTION: There is currently no effective method of measuring arterial blood gas tensions in austere environments such as in space or at high altitude. An alternative to direct arterial measurement is the sampling of arterialized earlobe blood, an accurate technique that has been in use in clinical medicine and physiology for more than 50 yr. We, therefore, developed an earlobe arterialized blood (EAB) collector for practical use in extreme environments. METHODS: The results from the EAB collector were compared with simultaneous samples of blood drawn from the radial artery. Six healthy subjects breathed a gas mixture of 12.8% O2 in N2 during 15 min of 8 degree head-down tilt. The blood samples were analyzed immediately. RESULTS: The mean differences in Po2 between arterialized earlobe and radial artery samples were 0.25 +/- 1.25 mmHg for Po2 and 1.0 +/- 0.75 mmHg for Pco2; neither difference was significant. There was no difference between the pH values obtained by the two techniques. CONCLUSION: This study suggests that arterialized blood sampled from the earlobe using the EAB collector may provide sufficiently accurate measurements of the Po2, Pco2 and pH of arterial blood for clinical or research use in extreme environments.

Basic life support in microgravity: evaluation of a novel method during parabolic flight.

BACKGROUND: If a cardiac arrest occurs in microgravity, the aim of current emergency procedures is to treat the patient using a medical restraint system within 2 min. The patient may require treatment while medical equipment is being deployed. The capability for one person, unaided, to successfully perform cardiopulmonary resuscitation (CPR) is, therefore, of paramount importance. A new technique has been developed whereby the practitioner encircles the thorax of the patient with his/her legs to restrain the patient to allow CPR to be performed in microgravity. METHOD: Two investigators performed both this method (during parabolic microgravity) and traditional CPR (at +1 Gz) on an instrumented CPR mannequin. The mannequin was modified to ensure accurate chest compression and ventilation measurements during microgravity. RESULTS: The mean (+/-SE) depth and rate of chest compression were 44.0+/-4.99 mm and 68.3+/-17.0 compressions x min(-1) respectively. Although the mean microgravity rate of compression proved significantly less (p < 0.05) than the +1 Gz mean (97.1+/-3.4 compressions x min(-1)), chest compression depth did not differ (p > 0.05) from +1 Gz measures (43.6+/-0.59 mm). The mean (+/-SE) microgravity tidal volume (VT) was 491+/-50.4 ml, which also did not differ (p > 0.05) from +1 Gz values (507.6+/-11.5 ml). DISCUSSION: Although difficulties in performing this method during parabolic flight primarily affected compression rate, it may be possible to conduct basic life support using this technique in any microgravity environment.