Tissue nitrogen (N2) exchange is primarily dependent on circulation, which may be modified by body thermal status. Thermal effects on uptake and washout of N2 have not been systematically investigated earlier. In the present study of eight subjects, N2 was washed out in thermally neutral ambient conditions (TN; skin temperature (Ts) = 33.
View Article and Find Full Text PDFDuring denitrogenation for rescue, crew members of an internally pressurized disabled submarine (DISSUB) must sit upright, which may hamper venous return, cardiac output and peripheral circulation. Since negative pressure breathing (NPB) might counteract this problem, denitrogenation was measured in sitting subjects performing NPB. Seven male subjects completed 125-minute nitrogen (N2) washouts breathing either 100% oxygen (O2) or a normoxic gas (21% O2 in argon) in control conditions and intermittent (I: inspirations only) or continuous (C) NPB at -10 or -15 cmH2O.
View Article and Find Full Text PDFTo compare two different types of respiratory muscle training on exercise performance, a protocol was devised consisting of a combination of a 4-week, 12-session resistive respiratory muscle training (RRMT) followed by a 4-week, 12-session voluntary isocapnic hyperpnea training (VIHT) and conducted in experienced runners (4 men, 4 women). Measurements before and 5 days after training included: pulmonary function (spirometry), maximal inspiratory and expiratory mouth pressures, respiratory endurance time, maximal oxygen uptake (V(o2)max), running time to voluntary exhaustion at 80% V(o2)max, blood lactate concentration, and minute ventilation. There were no statistically significant differences in pulmonary functions and V(o2)max post-RRMT and post-VIHT compared to pre-RMT.
View Article and Find Full Text PDFAviat Space Environ Med
July 2011
Introduction: The reasons for wide variability in the incidence of decompression sickness (DCS) are not well known, but diet may play a role. The hypothesis of the present study was that raising plasma triglycerides via a high-fat meal would increase the rate of nitrogen washout and, therefore, might be a useful adjunct when denitrogenation is used to reduce the likelihood of DCS in diving and exposure to altitude.
Methods: Nitrogen elimination was measured for 125 min in 10 subjects by gas chromatography while they breathed a normoxic argon-oxygen mixture at sea level.
J Appl Physiol (1985)
November 2010
Introduction: CO2 accumulation may limit crew survival in a disabled submarine. Reversible sedation using diazepam and flumazenil was proposed to reduce CO2 production.
Methods: Two groups of three resting subjects were studied during a 48-h placebo phase with diazepam and flumazenil placebos, followed by a 48-h drug phase with oral diazepam to induce sedation and intranasal flumazenil to reverse it.
Artif Cells Blood Substit Immobil Biotechnol
April 2010
Rationale: Earlier work has shown that experimental conditions calling for improved tissue oxygenation could be assisted by i.v. infusion of a dodecafluoropentane emulsion (DDFPe) forming oxygen-transporting microbubbles.
View Article and Find Full Text PDFResistance respiratory muscle training (RRMT) increases respiratory muscle and swimming performance at depths down to 17 msw. It is unknown if RRMT improves swimming performance at greater depths and if the improvements are associated with a reduced work of breathing (WOB), altered respiratory mechanics and/or improved respiratory muscle performance. Eight male subjects (30.
View Article and Find Full Text PDFJ Appl Physiol (1985)
January 2009
This is a brief overview of physiological reactions, limitations, and pathophysiological mechanisms associated with human breath-hold diving. Breath-hold duration and ability to withstand compression at depth are the two main challenges that have been overcome to an amazing degree as evidenced by the current world records in breath-hold duration at 10:12 min and depth of 214 m. The quest for even further performance enhancements continues among competitive breath-hold divers, even if absolute physiological limits are being approached as indicated by findings of pulmonary edema and alveolar hemorrhage postdive.
View Article and Find Full Text PDFThe effects of voluntary isocapnic hyperpnea (VIH) training (10 h over 4 weeks, 30 min/day) on ventilatory system and running performance were studied in 15 male competitive runners, 8 of whom trained twice weekly for 3 more months. Control subjects (n = 7) performed sham-VIH. Vital capacity (VC), FEV1, maximum voluntary ventilation (MVV), maximal inspiratory and expiratory mouth pressures, VO2max, 4-mile run time, treadmill run time to exhaustion at 80% VO2max, serum lactate, total ventilation (V(E)), oxygen consumption (VO2) oxygen saturation and cardiac output were measured before and after 4 weeks of VIH.
View Article and Find Full Text PDFRespiratory muscles can fatigue during prolonged and maximal exercise, thus reducing performance. The respiratory system is challenged during underwater exercise due to increased hydrostatic pressure and breathing resistance. The purpose of this study was to determine if two different respiratory muscle training protocols enhance respiratory function and swimming performance in divers.
View Article and Find Full Text PDFArtif Cells Blood Substit Immobil Biotechnol
September 2006
It has earlier been hypothesized that intravascular microbubbles, derived from a dodecafluoropentane (DDFP) emulsion, can transport physiologically significant amounts of oxygen in the animal body. To test this notion, anesthetized oxygen breathing rats were rendered severely anemic by bleeding and volume replacement. Rats treated with 0.
View Article and Find Full Text PDFBackground: The rate of nitrogen elimination during decompression is primarily dependent on tissue perfusion and, therefore, cardiac output (CO). Negative pressure breathing (NPB) is thought to increase CO by enhancing venous return and, consequently, the rate of nitrogen elimination. This notion was investigated in the present study.
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