RESUMO
At high altitude, hypoxia amplifies oxyhemoglobin saturation (SPO2) swings with changes in respiratory mechanics. Our objective was to examine the effects of posture on SPO2 and determine predictors of postural SPO2 changes in highlanders. 50 native highlanders from Puno, Peru (3825 m) assumed supine and upright-seated postures, in rotating sequence, while undergoing continuous pulse-oximetry. We compared mean SpO2 in each posture with a paired t-test. We examined associations of BMI, age, sex and spirometry with postural SpO2 changes with mixed-effects linear regression. In highlanders, SpO2 was 84% in the supine posture and was 1.0% ± 1.1 (p < 0.0001) greater in the upright-seated posture. Greater postural changes in SpO2 were associated with older age (p = 0.01 for interaction) but not with sex, BMI, FVC or FEV1. In highlanders, SpO2 is higher in the upright-seated compared to supine posture, especially with older age. Because we generally sleep flat, posture may contribute significantly to highlanders' hypoxemic burden during sleep. Postural intervention during sleep may mitigate nocturnal hypoxemia.
Assuntos
Altitude , Hipóxia/metabolismo , Oxiemoglobinas/metabolismo , Fenômenos Fisiológicos Respiratórios , Postura Sentada , Sono/fisiologia , Decúbito Dorsal/fisiologia , Fatores Etários , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Oximetria , PeruRESUMO
Associations between sleep disordered breathing (SDB) and cardiometabolic outcomes have not been examined in highlanders.We performed nocturnal polygraphy in Peruvian highlanders (3825â m). Multivariable linear regression models examined associations between SDB metrics and haemoglobin, glucose tolerance (haemoglobin A1c (HbA1c)), fasting glucose, homeostatic model-based assessments of insulin resistance and ß-cell function (HOMA-IR and HOMA-ß, respectively), blood pressure, and lipids, while adjusting for age, sex, body mass index (BMI) and wake oxygenation.Participants (n=187; 91 men) were (median (interquartile range)) 52 (45-62) years old, and had a BMI of 27.0 (24.3-29.5) kg·m-2 and 87% (85-88%) oxyhaemoglobin (arterial oxygen) saturation during wakefulness. In fully adjusted models, worsening nocturnal hypoxaemia was associated with haemoglobin elevations in men (p=0.03), independent of wake oxygenation and apnoea-hypopnoea index (AHI), whereas worsening wake oxygenation was associated with haemoglobin elevations in older women (p=0.02). In contrast, AHI was independently associated with HbA1c elevations (p<0.05). In single-variable models, nocturnal hypoxaemia was associated with higher HbA1c, HOMA-IR and HOMA-ß (p<0.001, p=0.02 and p=0.04, respectively), whereas AHI was associated with HOMA-IR, systolic blood pressure and triglyceride elevations (p=0.02, p=0.01 and p<0.01, respectively). These associations were not significant in fully adjusted models.In highlanders, nocturnal hypoxaemia and sleep apnoea were associated with distinct cardiometabolic outcomes, conferring differential risk for excessive erythrocytosis and glucose intolerance, respectively.
Assuntos
Altitude , Intolerância à Glucose , Hemoglobinas Glicadas/análise , Oximetria , Policitemia , Síndromes da Apneia do Sono , Idoso , Determinação da Pressão Arterial/estatística & dados numéricos , Índice de Massa Corporal , Meio Ambiente , Feminino , Intolerância à Glucose/diagnóstico , Intolerância à Glucose/epidemiologia , Humanos , Resistência à Insulina/fisiologia , Lipídeos/análise , Masculino , Pessoa de Meia-Idade , Oximetria/métodos , Oximetria/estatística & dados numéricos , Peru/epidemiologia , Policitemia/diagnóstico , Policitemia/epidemiologia , Polissonografia/métodos , Fatores de Risco , Síndromes da Apneia do Sono/diagnóstico , Síndromes da Apneia do Sono/epidemiologia , Síndromes da Apneia do Sono/metabolismo , Síndromes da Apneia do Sono/fisiopatologiaRESUMO
Pham, Luu V., Christopher Meinzen, Rafael S. Arias, Noah G. Schwartz, Adi Rattner, Catherine H. Miele, Philip L. Smith, Hartmut Schneider, J. Jaime Miranda, Robert H. Gilman, Vsevolod Y. Polotsky, William Checkley, and Alan R. Schwartz. Cross-sectional comparison of sleep-disordered breathing in native Peruvian highlanders and lowlanders. High Alt Med Biol. 18:11-19, 2017. BACKGROUND: Altitude can accentuate sleep disordered breathing (SDB), which has been linked to cardiovascular and metabolic diseases. SDB in highlanders has not been characterized in large controlled studies. The purpose of this study was to compare SDB prevalence and severity in highlanders and lowlanders. METHODS: 170 age-, body-mass-index- (BMI), and sex-matched pairs (age 58.2 ± 12.4 years, BMI 27.2 ± 3.5 kg/m2, and 86 men and 84 women) of the CRONICAS Cohort Study were recruited at a sea-level (Lima) and a high-altitude (Puno, 3825 m) setting in Peru. Participants underwent simultaneous nocturnal polygraphy and actigraphy to characterize breathing patterns, movement arousals, and sleep/wake state. We compared SDB prevalence, type, and severity between highlanders and lowlanders as measured by apnea-hypopnea index (AHI) and pulse oximetry (SPO2) during sleep. RESULTS: Sleep apnea prevalence was greater in highlanders than in lowlanders (77% vs. 54%, p < 0.001). Compared with lowlanders, highlanders had twofold elevations in AHI due to increases in central rather than obstructive apneas. In highlanders compared with lowlanders, SPO2 was lower during wakefulness and decreased further during sleep (p < 0.001). Hypoxemia during wakefulness predicted sleep apnea in highlanders, and it appears to mediate the effects of altitude on sleep apnea prevalence. Surprisingly, hypoxemia was also quite prevalent in lowlanders, and it was also associated with increased odds of sleep apnea. CONCLUSIONS: High altitude and hypoxemia at both high and low altitude were associated with increased SDB prevalence and severity. Our findings suggest that a large proportion of highlanders remain at risk for SDB sequelae.