Search NASA⌕ Search

SEARCH · Search NASA

Results for “INHALATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

240 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Obstructive apnea during sleep is associated with peripheral vasoconstriction

Obstructive apnea during sleep is associated with a substantial transient blood pressure elevation. The mechanism of this pressor response is unclear. In this study we measured muscle sympathetic nerve activity (MSNA), mean arterial pressure (Psa), and mean limb blood velocity as an index of blood flow (MBV, Doppler) and calculated changes in limb vascular resistance during and after apneas during both wakefulness and sleep in patients with the obstructive sleep apnea syndrome. Immediately postapnea during sleep Psa increased significantly compared with the earlier stages of apnea and this was preceded by a rise of MSNA (n = 5). In contrast to blood pressure, MBV remained unchanged. Because resistance = blood pressure/blood flow, limb vascular resistance increased by 29 +/- 8% from late apnea to postapnea (n = 7, p < 0.002). Voluntary breathhold maneuvers during room air exposure evoked similar responses (n = 10). Supplemental oxygen administered via nonrebreather face mask attenuated the MSNA and vasoconstrictor responses to obstructive (n = 2) and voluntary apneas (n = 10). Our data suggest that obstructive apneas in patients with the obstructive apnea syndrome are accompanied by transient limb vasoconstriction. This vasoconstrictor response appears to be, at least in part, mediated by the sympathetic nervous system and may be linked to hypoxia.

NASA Discipline Cardiopulmonary↗
NASA NTRS1998

A new preoxygenation procedure for extravehicular activity (EVA)

A 10.2 psi staged-decompression schedule or a 4-hour preoxygenation at 14.7 psi is required prior to extravehicular activity (EVA) to reduce decompression sickness (DCS) risk. Results of recent research at the Air Force Research Laboratory (AFRL) showed that a 1-hour resting preoxygenation followed by a 4-hour, 4.3 psi exposure resulted in 77% DCS risk (N=26), while the same profile beginning with 10 min of exercise at 75% of VO2peak during preoxygenation reduced the DCS risk to 42% (P<.03; N=26). A 4-hour preoxygenation without exercise followed by the 4.3 psi exposure resulted in 47% DCS risk (N=30). The 1-hour preoxygenation with exercise and the 4-hour preoxygenation without exercise results were not significantly different. Elimination of either 3 hours of preoxygenation or 12 hours of staged-decompression are compelling reasons to consider incorporation of exercise-enhanced preoxygenation.

NASA Discipline Environmental Health↗
NASA NTRS1997

Modeling the effects of exercise during 100% oxygen prebreathe on the risk of hypobaric decompression sickness

BACKGROUND: Several previous studies indicated that exercise during prebreathe with 100% O2 decreased the incidence of hypobaric decompression sickness (DCS). We report a meta-analysis of these investigations combined with a new study in our laboratory to develop a statistical model as a predictive tool for DCS. HYPOTHESIS: Exercise during prebreathe increases N2 elimination in a theoretical 360-min half-time compartment decreasing the incidence of DCS. METHODS: A dose-response probability tissue ratio (TR) model with 95% confidence limits was created for two groups, prebreathe with exercise (n = 113) and resting prebreathe (n = 113), using nonlinear regression analysis with maximum likelihood optimization. RESULTS: The model predicted that prebreathe exercise would reduce the residual N2 in a 360-min half-time compartment to a level analogous to that in a 180-min compartment. This finding supported the hypothesis. The incidence of DCS for the exercise prebreathe group was significantly decreased (Chi-Square = 17.1, p < 0.0001) from the resting prebreathe group. CONCLUSIONS: The results suggested that exercise during prebreathe increases tissue perfusion and N2 elimination approximately 2-fold and markedly lowers the risk of DCS. Based on the model, the prebreathe duration may be reduced from 240 min to a predicted 91 min for the protocol in our study, but this remains to be verified. The model provides a useful planning tool to develop and test appropriate prebreathe exercise protocols and to predict DCS risks for astronauts.

NASA Program Environmental Health↗
NASA NTRS1990

Mechanism of transport and distribution of organic solvents in blood

Little is known about the mechanism of transport and distribution of volatile organic compounds in blood. Studies were conducted on five typical organic solvents to investigate how these compounds are transported and distributed in blood. Groups of four to five rats were exposed for 2 hr to 500 ppm of n-hexane, toluene, chloroform, methyl isobutyl ketone (MIBK), or diethyl ether vapor; 94, 66, 90, 51, or 49%, respectively, of these solvents in the blood were found in the red blood cells (RBCs). Very similar results were obtained in vitro when aqueous solutions of these solvents were added to rat blood. In vitro studies were also conducted on human blood with these solvents; 66, 43, 65, 49, or 46%, respectively, of the added solvent was taken up by the RBCs. These results indicate that RBCs from humans and rats exhibited substantial differences in affinity for the three more hydrophobic solvents studied. When solutions of these solvents were added to human plasma and RBC samples, large fractions (51-96%) of the solvents were recovered from ammonium sulfate-precipitated plasma proteins and hemoglobin. Smaller fractions were recovered from plasma water and red cell water. Less than 10% of each of the added solvents in RBC samples was found in the red cell membrane ghosts. These results indicate that RBCs play an important role in the uptake and transport of these solvents. Proteins, chiefly hemoglobin, are the major carriers of these compounds in blood. It can be inferred from the results of the present study that volatile lipophilic organic solvents are probably taken up by the hydrophobic sites of blood proteins.

Solvents/administration & dosage/metabolism/pharma↗
NASA NTRS1990

Blood biochemical and cellular changes during decompression and simulated extravehicular activity

Blood biochemical and cellular parameters were measured in human subjects before and after exposure to a decompression schedule involving 6 h of oxygen prebreathing. The exposure was designed to simulate extravehicular activity for 6 h (subjects performed exercise while exposed to 29.6 kPa). There were no significant differences between blood samples from subjects who were susceptible (n = 11) versus those who were resistant (n = 27) to formation of venous gas emboli. Although several statistically significant (P less than 0.05) changes in blood parameters were observed following the exposure (increases in white blood cell count, prothrombin time, and total bilirubin, and decreases in triglycerides, very-low-density lipoprotein cholesterol, and blood urea nitrogen), the changes were small in magnitude and blood factor levels remained within normal clinical ranges. Thus, the decompression schedule used in this study is not likely to result in blood changes that would pose a threat to astronauts during extravehicular activity.

Decompression Sickness/blood/etiology/prevention &↗