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Study objectivesChronic mountain sickness (CMS) is commonly observed among Andean and other highland populations. Sleep-disordered breathing (SDB) is highly prevalent at high altitude, and SDB and nocturnal hypoxemia have been observed in CMS. Phlebotomy is commonly performed to treat CMS, but it is unknown whether reducing hematocrit improves SDB. We hypothesized that isovolemic hemodilution (IVHD) in CMS would reduce SBD severity and improve sleep efficiency.MethodsSix participants with CMS and 8 without CMS, all residents of Cerro de Pasco, Peru (altitude 4340 m), completed baseline nocturnal sleep studies. CMS participants then underwent IVHD, and nocturnal sleep studies were repeated 24-48 hours after IVHD. We analyzed sleep apnea severity, nocturnal oxygenation, and sleep quality in those with CMS relative to those without CMS, and the effects of IVHD in CMS participants.ResultsParticipants with CMS did not have altered sleep architecture, sleep apnea severity, or nocturnal oxygenation relative to non-CMS participants. However, IVHD in CMS increased apnea-hypopnea index (40.9 ± 6.9 events/h to 61.5 ± 7.7 events/h, P = .009). IVHD increased oxyhemoglobin desaturation index (P = .008) and the percentage of sleep time spent with oxyhemoglobin saturation at or below 80% (P = .012). There was no effect of IVHD on sleep efficiency, arousal index, or sleep staging.ConclusionsIn this cohort, CMS was not associated with worsened SDB or changes in sleep architecture. IVHD, a putative therapeutic option for participants with CMS, appears to worsen nocturnal oxygenation and SDB within 48 hours post-IVHD.CitationSanchez-Azofra A, Villafuerte FC, DeYoung PN, et al. Isovolemic hemodilution in chronic mountain sickness acutely worsens nocturnal oxygenation and sleep apnea severity. J Clin Sleep Med. 2022;18(10):2423-2432.

Background: Sleep quality is poor in severe emphysema. We hypothesized that in addition to nocturnal oxygen desaturation, the severity of airflow obstruction and degree of thoracic hyperinflation are responsible. Methods: Twenty-five patients (14 males, 64 ±± 6 [[ ±± SD]] yrs, BMI 24.7 ±± 4.2 kg/m2) with severe emphysema (FEV1 == 28 ±± 8%% predicted, TLC == 125 ±± 14%% predicted) were studied. Measurements included spirometry, lung volumes, arterial blood gas, length of the diaphragm's zone of apposition (LZAP) and a polysomnogram. Results: Total sleep time (TST) was 227 ±± 93 minutes with a sleep efficiency (SE) of 56 ±± 21%%. The mean SaO2, lowest SaO2, and%% TST with a SaO2 < 90%% were 90 ±± 5%%, 83 ±± 8%% and 29 ±± 40%%, respectively. TST correlated with FEV1%% (r == 0.5, p == 0.02), FVC%% (r == 0.4, p == 0.03) and LZAP (r == 0.5, p == 0.01). SE correlated with FEV1%% (r == 0.5, p == 0.02) and LZAP (r == 0.5, p == 0.01), but not with FVC%% (r == 0.4, p == 0.07). Additionally, TST and SE correlated negatively with residual volume%% (r == -0.4, p == 0.046, and r == -0.4, p == 0.03, respectively). There was no correlation between TST and SE and measures of nocturnal oxygenation. Multiple linear regression was used to predict TST, with 50%% (r2 == 0.49) explained by a combination of LZAP (27%%), mean SaO2 (23%%), and the lowest SaO2 (< 1%%). To predict SE, 44%% (r2 == 0.43) was explained by a combination of LZAP (29%%), mean SaO2 (14%%), and the lowest SaO2 (1%%). Conclusion: Although parameters of respiratory function and mechanics correlate with sleep quality, both nocturnal oxygenation and measurements of respiratory function/mechanics predict sleep quality in severe emphysema. [ABSTRACT FROM AUTHOR]