Rationale: Periodic occlusion of the upper airway in patients with obstructive sleep apnea leads to chronic intermittent hypoxia, which increases acute hypoxic ventilatory response (AHVR). Animal studies suggest that oxidative stress may modulate AHVR by increasing carotid body sensitivity hypoxia. This has not been shown humans.Objectives: To determine whether 4 days exposure hypoxia and strength association between AHVR.Methods: After two normoxic control (Day −4 Day 0), 10 young healthy...

Intermittent hypoxia (IH) is believed to contribute the pathogenesis of hypertension in obstructive sleep apnea through mechanisms that include activation renin-angiotensin system. The objective this study was assess role type I angiotensin II receptor mediating an increase arterial pressure associated with a single 6-hour IH exposure. Using double-blind, placebo-controlled, randomized, crossover design, we exposed 9 healthy male subjects sham IH, placebo medication, and antagonist losartan....

Key points The oxygen cost of breathing represents a significant fraction total uptake during intense exercise. At given ventilation, women have greater work compared with men, and because is linearly related to we hypothesized that their would also be greater. For had absolute breathing, this represented uptake. Regardless sex, those who developed expiratory flow limitation at maximal in indicates (and possibly cardiac output) directed the respiratory muscles, which may influence blood...

Acute mountain sickness (AMS) may affect individuals who (rapidly) ascend to altitudes higher than 2,000-3,000 m. A more serious consequence of rapid ascent be high-altitude pulmonary edema, a hydrostatic edema associated with increased capillary pressures. Acetazolamide is effective against AMS, possibly by increasing ventilation and cerebral blood flow (CBF). In animals, it inhibits hypoxic vasoconstriction.We examined the influence acetazolamide on response hypoxia ventilation, CBF,...

Intermittent hypoxia (IH) is thought to be responsible for many of the long-term cardiovascular consequences associated with obstructive sleep apnoea (OSA). Experimental human models IH can aid in investigating pathophysiology these complications. The purpose this study was determine effects on and cerebrovascular response acute hypercapnia an experimental model that simulates hypoxaemia experienced by OSA patients. We exposed 10 healthy, male subjects 4 consecutive days. profile involved 2...

Key points By virtue of their smaller lung volumes and airway diameters, women develop more mechanical ventilatory constraints during exercise, which may result in increased vulnerability to hypoxaemia exercise. Hypoxaemia developed at all exercise intensities with varying patterns was common aerobically trained subjects; however, some untrained also hypoxaemia. Mechanical respiratory directly lead prevent adequate reversal most women. Experimentally reversing heliox gas partially reversed...

Intermittent hypoxia (IH) is associated with increased risk of cardiovascular disease. Exosomes are secreted by most cell types and released in biological fluids, including plasma, play a role modifying the functional phenotype target cells. Using an experimental human model IH, we investigated potential exosome-derived biomarkers IH-induced vascular dysfunction.Ten male volunteers were exposed to room air (D0), IH (6 h/day) for 4 days (D4) allowed recover (D8). Circulating plasma exosomes...

We investigated 1) the regional distribution of cerebral blood flow (CBF), 2) influence end-tidal Pco2 (PetCO2) on CBF, and 3) potential for an extracranial "steal" from anterior brain region during passive hyperthermia. Nineteen (13 male) volunteers underwent supine heating until a steady-state esophageal temperature 2°C above resting was established. Measurements were obtained normothermia (Normo), poikilocapnic hyperthermia (Hyper), with PetCO2 Po2 clamped to Normo levels (Hyper-clamp)....

We asked if the higher work of breathing (Wb) during exercise in women compared with men is explained by biological sex. created a statistical model that accounts for both viscoelastic and resistive components total Wb independently compares effects applied to esophageal pressure-derived values obtained an incremental cycle test exhaustion. Subjects were healthy (n = 17) 18) range maximal aerobic capacities (V̇o2 max range: 40-68 39-60 ml·kg(-1)·min(-1)). also calculated dysanapsis ratio...

We sought to characterize and quantify the performance of a portable dynamic end-tidal forcing (DEF) system in controlling partial pressure arterial CO2 (Pa(CO2)) O2 (Pa(O2)) at low (LA; 344 m) high altitude (HA; 5,050 during an isooxic test isocapnic test, which is commonly used measure ventilatory vascular reactivity humans (n = 9). The tests involved step changes (PET(CO2)) -10, -5, 0, +5, +10 mmHg from baseline. consisted 10-min hypoxic (PET(O2) 47 mmHg) baseline LA 5-min euoxic 100 HA....

Our aim was to quantify the end-tidal-to-arterial gas gradients for O 2 (P ET -PaO ) and CO (Pa-P during a reactivity test determine their influence on cerebrovascular (CVR) ventilatory (HCVR) response in subjects with (PFO+, n = 8) without (PFO−, 7) patent foramen ovale (PFO). We hypothesized that 1) Pa-P would be greater hypoxia compared normoxia, 2) similar, whereas P gradient those PFO, 3) HCVR CVR underestimated when plotted against PaCO , 4) previously derived prediction algorithms...

We examined the effects of age, sex, and their interaction on mechanical ventilatory constraint dyspnea during exercise in 22 older (age = 68 ± 1 yr; n 12 women) younger 25 y, 11 subjects. During submaximal exercise, subjects had higher end-inspiratory (EILV) end-expiratory (EELV) lung volumes than (both P < 0.05). maximal similar EILV ( > 0.05) but EELV No sex differences or were observed. noted that women a work breathing (Wb) for given minute ventilation (V̇e) ≥65 l/min men Wb V̇e ≥60 age...

We determined the ventilatory, cardiovascular and cerebral tissue oxygen response to two protocols of normobaric, isocapnic, intermittent hypoxia. Subjects ( n = 18, male) were randomly assigned short‐duration hypoxia (SDIH, 12% O 2 separated by 5 min normoxia for 1 h) or long‐duration (LDIH, 30 ). Both groups had 10 exposures over a 12 day period. The hypoxic ventilatory (HVR) was measured before each daily exposure on days 1, 3, 5, 8, 12. HVR again 3 after end During all procedures,...

The mechanism leading to increased risk of stroke in patients with obstructive sleep apnea (OSA) is unknown. It may occur through alteration the regulation cerebral blood flow, reflected part by response vasculature hypoxia. We hypothesized that cerebrovascular hypoxia reduced OSA.To determine flow OSA.The 20 minutes isocapnic was measured eight male OSA before and after 4 6 weeks continuous positive airway pressure (CPAP) therapy 10 matched healthy control subjects.The significantly lower...

Key points High work of breathing and exercise‐induced arterial hypoxaemia (EIAH) can decrease O 2 delivery exacerbate quadriceps fatigue in healthy men. Women have a higher during exercise, dedicate greater fraction whole‐body towards their respiratory muscles develop EIAH. Despite reduction men's breathing, the attenuation was similar between sexes. The degree EIAH sexes, regardless sex, those who developed greatest exercise demonstrated most fatigue. Based on our previous finding that...

The aim of this study was to assess the role type 1 angiotensin II (AT(1)) receptor in increase oxidative stress and NO metabolism during a single 6 h exposure intermittent hypoxia (IH). Nine healthy young men were exposed, while awake, sham IH, IH with placebo medication, AT(1) antagonist, losartan, using double-blind, placebo-controlled, randomized, crossover design. In addition blood pressure, stress, peroxynitrite activity, uric acid, global antioxidant status end-products (NOx) measured...

Purpose: Expiratory flow limitation (EFL) can occur in healthy young women during exercise. We questioned whether the occurrence and severity of EFL were related to aerobic fitness or anatomical factors. Methods: Twenty-two (<40 yr) performed a progressive cycle test exhaustion. The subjects' maximum expiratory flow-volume curve was compiled from several effort-graded vital capacity maneuvers before after curve, along with inspiratory maneuvers, used determine lung volumes flows quantify...

The effects of partial acclimatization to high altitude (HA; 5,050 m) on cerebral metabolism and cerebrovascular function have not been characterized. We hypothesized (1) increased reactivity (CVR) at HA; (2) that CO2 would affect more than hypoxia. PaO2 PaCO2 were manipulated sea level (SL) simulate HA exposure, HA, SL blood gases simulated; CVR was assessed both altitudes. Arterial-jugular venous differences measured calculate metabolic rates flow (CBF). observed yields a steeper CO2-H(+)...

Cerebrovascular reactivity impacts CO₂-[H(+)] washout at the central chemoreceptors and hence has marked influence on control of ventilation. To date, integration cerebral blood flow (CBF) ventilation been investigated exclusively with measures anterior CBF, which a differential from vertebrobasilar system perfuses brainstem. We hypothesized that: (1) posterior versus CBF would have stronger relationship to chemoreflex magnitude during hypercapnia, (2) that higher lead greater hypoxic...

Key points Vasovagal syncope (a common form of fainting) is frequently associated with excessive breathing and leads to reductions in carbon dioxide (hypocapnia) cerebral hypoperfusion. The prevention hypocapnia during orthostatic stress has been shown improve tolerance, but it still remains be quantified a larger population, more sustained stress. Resting brain blood flow impact tolerance; however, the importance resting per se pathophysiology vasovagal not clearly explicated. Our findings...

Intermittent hypoxia leads to long-lasting increases in muscle sympathetic nerve activity and blood pressure, contributing increased risk for hypertension obstructive sleep apnoea patients. We determined whether augmented vascular responses increasing vasomotor outflow, termed neurovascular transduction (sNVT), accompanied changes pressure following acute intermittent hypercapnic men. Lower body negative was utilized induce a range of vasoconstrictor firing while measuring beat-by-beat...