Search

Obstructive sleep apnea (OSA) is common in heart and kidney disease, both conditions prone to fluid retention. Nocturnal rostral fluid shift contributes to the pathogenesis of OSA in men more than women, suggesting a potential role for sex differences in body fluid composition in the pathogenesis of OSA, with men having a predisposition to more severe OSA due to an underlying volume expanded state. Continuous positive airway pressure (CPAP) increases intraluminal pressure in the upper airway and mitigates the rostral fluid shift; this, in turn, may prevent fluid redistribution from other parts of the body to the upper airway. We sought to determine the impact of CPAP on sex differences in body fluid composition. Twenty‐nine (10 women, 19 men) incident, sodium replete, otherwise healthy participants who were referred with symptomatic OSA (oxygen desaturation index >15/h) were studied pre‐ and post‐CPAP (>4 h/night × 4 weeks) using bioimpedance analysis. Bioimpedance parameters including fat‐free mass (FFM, %body mass), total body water (TBW, %FFM), extracellular and intracellular water (ECW and ICW, %TBW), and phase angle (°) were measured and evaluated for sex differences before and after CPAP. Pre‐CPAP, despite TBW being similar between sexes (74.6 ± 0.4 vs. 74.3 ± 0.2%FFM, p = 0.14; all values women vs. men), ECW (49.7 ± 0.7 vs. 44.0 ± 0.9%TBW, p < 0.001) was increased, while ICW (49.7 ± 0.5 vs. 55.8 ± 0.9%TBW, p < 0.001) and phase angle (6.7 ± 0.3 vs. 8.0 ± 0.3°, p = 0.005) were reduced in women compared to men. There were no sex differences in response to CPAP (∆TBW –1.0 ± 0.8 vs. 0.7 ± 0.7%FFM, p = 0.14; ∆ECW –0.1 ± 0.8 vs. −0.3 ± 1.0%TBW, p = 0.3; ∆ICW 0.7 ± 0.4 vs. 0.5 ± 1.0%TBW, p = 0.2; ∆Phase Angle 0.2 ± 0.3 vs. 0.0 ± 0.1°, p = 0.7). Women with OSA had baseline parameters favoring volume expansion (increased ECW, reduced phase angle) compared to men. Changes in body fluid composition parameters in response to CPAP did not differ by sex. We utilized bio‐electrical impedance analysis to assess sex differences in body composition in 10 women and 19 men with obstructive sleep apnea (OSA) before and after treatment with continuous positive airway pressure (CPAP) therapy. We observed that despite similar total body water (% fat‐free mass), women with OSA had increased extracellular water and reduced intracellular water compared to men, suggestive of a volume expanded state, though the response of these body composition parameters to 1 month of CPAP therapy did not differ by sex. Our findings support that there are underlying sex differences in body composition in OSA, though contrary to our expectations, women with OSA in our study had body composition parameters which favored volume expansion compared to men. Importantly, the impact of CPAP therapy on body composition did not differ by sex. [ABSTRACT FROM AUTHOR]

Men have faster loss of kidney function and greater renal renin-angiotensin system (RAS) activity compared with women. Obstructive sleep apnea (OSA) is common in chronic kidney disease; the vascular effects of OSA differ by sex, and OSA-associated glomerular hyperfiltration can be reversed by continuous positive airway pressure (CPAP) therapy. We evaluated sex differences in the effect of CPAP on renal hemodynamics and the renal RAS in OSA. Twenty-nine Na-replete, otherwise healthy study participants with OSA (10 women and 19 men) with nocturnal hypoxemia were studied pre- and post-CPAP (-4 h/night for 4 wk). Renal hemodynamics [renal plasma flow (RPF), glomerular filtration rate (GFR), and filtration fraction(FF)] were measured at baseline and in response to ANG II challenge, as a marker of renal RAS activity, pre- and post-CPAP therapy for 1 mo. In women, CPAP was associated with increased RPF (626 ± 22 vs. 718 ± 43 mL/min, P = 0.007, pre- vs. post- CPAP), maintained GFR (108 ± 2 vs. 105 ± 3 mL/min, P = 0.8), and reduced FF (17.4 ± 0.8% vs. 15.0 ± 0.7%, P = 0.017). In men, CPAP was associated with maintained RPF (710 ± 37 vs. 756 ± 38 mL/min, P = 0.1), maintained GFR (124 ± 8 vs. 113 ± 6 mL/min, P = 0.055), and reduced FF (18.6 ± 1.7% vs. 15.5 ± 1.1%, P = 0.035). Pre-CPAP, there were no sex differences in renal hemodynamic responses to ANG II. CPAP use was associated with a greater renovasoconstrictive response to ANG II in women (RPF at 30 min: -100 ± 27 vs. -161 ± 25 mL/min, P = 0.007, and RPF at 60 min: -138 ± 27 vs. -206 ± 32 mL/min, P = 0.007) but not men. CPAP use was associated with improved renal hemodynamics in both sexes and downregulated renal RAS activity in women but not men. [ABSTRACT FROM AUTHOR]

Rationale: Obstructive sleep apnea (OSA) and nocturnal hypoxemia are associated with chronic kidney disease and up-regulation of the renin-angiotensin system (RAS), which is deleterious to renal function. The extent to which the magnitude of RAS activation is influenced by the severity of nocturnal hypoxemia and comorbid obesity has not been determined.Objectives: To determine the association between the severity of nocturnal hypoxemia and RAS activity and whether this is independent of obesity in patients with OSA.Methods: Effective renal plasma flow (ERPF) response to angiotensin II (AngII) challenge, a marker of renal RAS activity, was measured by paraaminohippurate clearance technique in 31 OSA subjects (respiratory disturbance index, 51 ± 25 h(-1)), stratified according to nocturnal hypoxemia status (mean nocturnal SaO2, ≥90% [moderate hypoxemia] or <90% [severe hypoxemia]) and 13 obese control subjects.Measurements and Main Results: Compared with control subjects, OSA subjects demonstrated decreased renovascular sensitivity (ERPF, -153 ± 79 vs. -283 ± 31 ml/min; P = 0.004) (filtration fraction, 5.4 ± 3.8 vs. 7.1 ± 2.6%; P = 0.0025) in response to 60 minutes of AngII challenge (mean ± SD; all P values OSA vs. control). The fall in ERPF in response to AngII was less in patients with severe hypoxemia compared with those with moderate hypoxemia (P = 0.001) and obese control subjects after 30 minutes (P < 0.001) and 60 minutes (P < 0.001) of AngII challenge, reflecting more augmented renal RAS activity. Severity of hypoxemia was not associated with the blood pressure or the systemic circulating RAS component response to AngII.Conclusions: The severity of nocturnal hypoxemia influences the magnitude of renal, but not the systemic, RAS activation independently of obesity in patients with OSA. [ABSTRACT FROM AUTHOR]

Rationale: Obstructive sleep apnea (OSA) has been associated with kidney function loss, which may be related to changes in the renin–angiotensin system (RAS). Objectives: We sought to determine the effect of continuous positive airway pressure (CPAP) of patients with OSA on renal hemodynamics at baseline and in response to angiotensin II (AngII), which reflects RAS activity. Methods: Twenty normotensive, nondiabetic, newly diagnosed OSA subjects (15 men, 5 women, 50 ± 2 yr, respiratory disturbance index [RDI] > 15 h-1) with nocturnal hypoxemia (SaO2 < 90% for >12% of the night) were studied in high-salt balance pre- and post-CPAP therapy (>4 h CPAP use/night for 1 mo). Glomerular filtration rate (GFR), renal plasma flow (RPF), and filtration fraction (FF) (a surrogate marker for intraglomerular pressure) we remeasured pre- and post-CPAP using inulin and para-aminohippurate clearance techniques at baseline and in response to graded AngII infusion (3 ng/kg/min × 30 min and 6 ng/kg/min × 30 min, respectively). Measurements and Main Results: CPAP corrected OSA and hypoxemia (RDI: 42 ± 4 vs. 4 ± 1 h-1, P < 0.001; duration SaO2 < 90%: 36% 6 5% vs. 6 6 2%, P , 0.001). CPAP reduced GFR (124 × 8 ml/min vs. 110 × 6 ml/min, P = 0.014), increased RPF (692 ± 36 ml/min vs. 749 ± 40 ml/min, P = 0.059), and reduced baseline FF (18.9 ± 1.6% vs. 15.3 ± 1.0%, P = 0.004). Post-CPAP demonstrated a blunted GFR response (-9 ± 3 ml/min vs. -2 ± 2 ml/min, P = 0.033) and augmented RPF response (-182 ± 22 ml/min vs. -219 ± 25 ml/min, P = 0.024) to AngII. FF response was maintained (P = 0.4). CPAP reduced baseline mean arterial pressure (94 ± 2 vs. 89 ± 2 mm Hg, P = 0.002), plasma aldosterone (149 ± 18 vs. 109 ± 10 pmol/L, P = 0.003), and urinary protein excretion (61 [39–341] mg/day vs. 56 [22–204] mg/d, P = 0.003). Conclusions: CPAP therapy was associated with improved renal hemodynamics and down-regulation of renal RAS activity, suggesting a potential therapeutic benefit for kidney function. [ABSTRACT FROM AUTHOR]