Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hyperventilation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,315 records · Page 73Linked to original sources
PubMed2000

Evidence for an inadequate hyperventilation inducing arterial hypoxemia at submaximal exercise in all highly trained endurance athletes.

PURPOSE: The majority of highly trained endurance athletes with a maximal oxygen uptake greater than 60 mL x min(-1) x kg(-1) develop exercise-induced hypoxemia (EIH). Yet some of them apparently do not. The pathophysiology of EIH seems to be multifactorial, and one explanatory hypothesis is a relative hypoventilation. Nevertheless, conflicting results have been reported concerning its contribution to EIH. The aim of this study was to compare the cardiorespiratory responses to maximal exercise of highly trained endurance athletes demonstrating the same aerobic capacity without EIH (N athletes) and with EIH (H athletes). METHODS: Ten N athletes and twelve H athletes performed an incremental exercise test. Measurements of arterial blood gases and cardiorespiratory parameters were performed at rest and during exercise. RESULTS: All athletes presented a significant decrease in PaO2 (P < 0.05) from rest up to 80% VO2max associated with an increase in PaCO2, both findings consistent with a relative hypoventilation. Then the H athletes, who had a greater training volume per week and a higher second ventilatory threshold than the N athletes (respectively, 17 +/- 1.1 vs 13.1 +/- 0.7 h x wk(-1); 91.8 +/- 1.7 vs 86.1 +/- 1.8% VO2max), presented a continuous PaO2 decrease up to VO2max. This was associated with a widening (Ai-a)DO2. CONCLUSION: This study showed that a relative hypoventilation, probably induced by a high level of endurance training, induced hypoxemia in all athletes. However, a nonventilatory mechanism, perhaps related to the volume of training, seemed to affect gas exchanges beyond the second ventilatory threshold in the H athletes, thereby enhancing EIH.

Adult↗
PubMed2002

Treatment of transtentorial herniation unresponsive to hyperventilation using hypertonic saline in dogs: effect on cerebral blood flow and metabolism.

We tested the hypothesis that transtentorial herniation (TTH) represents a state of cerebral ischemia that can be reversed by hypertonic saline. Because of the high mortality associated with TTH, new therapeutic strategies need to be developed for rapid and effective reversal of this process. We produced TTH (defined by acute dilatation of one or both pupils) by creating supratentorial intracerebral hemorrhage with autologous blood injection in seven mongrel dogs anesthetized using intravenous pentobarbital and fentanyl. We measured serial rCBF (regional cerebral blood flow) using radiolabeled microspheres in regions around and distant to the hematoma. Cerebral oxygen extraction and oxygen consumption (CMRO2) were measured by serial sampling of cerebral venous blood from the sagittal sinus. Mean arterial pressure (MAP) and intracranial pressure (ICP) were continuously monitored. TTH was successfully reversed over a mean period of 25.7 +/- 4.9 minutes after intravenous administration of 23.4% sodium chloride (1.4 mL/kg) in all animals. All measurements were recorded 15, 30, 60, and 90 minutes after administration of 23.4% sodium chloride. Compared to prehematoma ICP (14.1 +/- 1.7 mm Hg, mean +/- SE), elevation in ICP was observed during TTH (36.2 +/- 7.2 mm Hg) with no change in cerebral perfusion pressure (CPP) (80.4 +/- 4.7 vs. 76.7 +/- 10.1 mm Hg) because of concomitant elevation in mean arterial pressure. Compared to baseline values, there was a reduction in rCBF (mL/100 gm/min +/- SE) in brainstem (12.1 +/- 2.0 vs. 21.4 +/- 1.4), gray matter (18.2 +/- 2.1 vs. 31.4 +/- 1.8), and white matter (8.6 +/- 1.7 vs.18.7 +/- 0.9) in the hemisphere contralateral to the hematoma; and gray matter (12.9 +/- 2.9 vs. 27.9 +/- 2.2) and white matter (8.3 +/- 2.0 vs.19.9 +/- 1.0) in the ipsilateral hemisphere distant from the hematoma. Administration of 23.4% sodium chloride resulted in reduced ICP at 15 minutes (12.7 +/- 1.4) and 30 minutes (15.6 +/- 3.1) after administration. RCBF values were restored in all regions studied after administration of 23.4% sodium chloride with an increase in CMRO2 (1.8 +/- 0.4 vs. 3.9 +/- 0.7 mL O2 /100 gm/min). Compared with baseline values, rCBF increased in the ipsilateral (31.7 +/- 2.5 vs. 63.4 +/- 11.7) and contralateral (28.7 +/- 1.9 vs. 45.5 +/- 5.7) thalamus at 15 minutes after administration of 23.4% sodium chloride. TTH represented a state of ischemia in brainstem and supratentorial gray and white matter in the presence of adequate CPP, suggesting mechanical compression of vessels at the level of tentorium. Hypertonic saline reversed TTH, and restored both rCBF and CMRO2, although hyperemia was observed immediately after reversal of TTH. Administration of hypertonic saline may preserve neurologic function during the interim period between TTH and surgical intervention.

Animals↗
PubMed2003

Carbon dioxide attenuates pulmonary impairment resulting from hyperventilation.

OBJECTIVE: Deliberate elevation of PaCO2 (therapeutic hypercapnia) protects against lung injury induced by lung reperfusion and severe lung stretch. Conversely, hypocapnic alkalosis causes lung injury and worsens lung reperfusion injury. Alterations in lung surfactant may contribute to ventilator-associated lung injury. The potential for CO2 to contribute to the pathogenesis of ventilator-associated lung injury at clinically relevant tidal volumes is unknown. We hypothesized that: 1) hypocapnia would worsen ventilator-associated lung injury, 2) therapeutic hypercapnia would attenuate ventilator-associated lung injury; and 3) the mechanisms of impaired compliance would be via alteration of surfactant biochemistry. DESIGN: Randomized, prospective animal study. SETTING: Research laboratory of university-affiliated hospital. SUBJECTS: Anesthetized, male New Zealand Rabbits. INTERVENTIONS: All animals received the same ventilation strategy (tidal volume, 12 mL/kg; positive end-expiratory pressure, 0 cm H2O; rate, 42 breaths/min) and were randomized to receive FiCO2 of 0.00, 0.05, or 0.12 to produce hypocapnia, normocapnia, and hypercapnia, respectively. MEASUREMENTS AND MAIN RESULTS: Alveolar-arterial oxygen gradient was significantly lower with therapeutic hypercapnia, and peak airway pressure was significantly higher with hypocapnic alkalosis. However, neither static lung compliance nor surfactant chemistry (total surfactant, aggregates, or composition) differed among the groups. CONCLUSIONS: At clinically relevant tidal volume, CO2 modulates key physiologic indices of lung injury, including alveolar-arterial oxygen gradient and airway pressure, indicating a potential role in the pathogenesis of ventilator-associated lung injury. These effects are surfactant independent.

Animals↗