843 Paradoxical Waking Hypoxemia that Improves with Sleep

Introduction We present a case of paradoxically worsened hypoxia during wake phase of polysomnography while undergoing a CPAP titration study. Nighttime hypoxemia is a common feature in obstructive sleep apnea, due to obstructive events that manifest while sleeping. Excluding OSA, there remains an extensive differential for disease processes that cause hypoxemia while asleep; however, none of these processes can explain waking hypoxemia that improves upon sleeping. Report of case(s) A 70 year old male with severe OSA diagnosed by home sleep test (REI 46.5, nadir O2=76%) underwent polysomnography with PAP titration and demonstrated several hours of interrupted sleep without hypoxia and minimal obstructive events on CPAP 9–13 cmH2O. During the study, while awake at CPAP of 14 cmH2O, he developed hypoxia to mid-high 80s and supplemental oxygen bleed in was added starting at 3L and increased to 5L during a prolonged period of wakefulness. On CPAP 15 cmmH2O with 5L bleed-in, the patient fell asleep and oxygen saturation again increased to low 90s. He underwent an extensive workup for other cardiopulmonary causes of hypoxemia, with pulmonary function testing showing moderate obstructive ventilatory defect and mild DLCO impairment. An echocardiogram with saline contrast bubble study was relatively unremarkable, without evidence of right to left shunting. He underwent a chest CTA which was negative for pulmonary embolism, though it did reveal an enlarged pulmonary artery consistent with pulmonary hypertension. His chronic hypoxemia was treated with 2L supplemental oxygen during the day and bleed-in with CPAP at night. Conclusion Though nocturnal hypoxemia is common with OSA, polysomnography with paradoxical hypoxemia during wake phase has not been reported. Notably, the patient was without prolonged hypoxia during his sleep phase while on CPAP treatment with minimal apneic/hypopneic events. Pulmonary hypertension can also present as nocturnal hypoxemia, but it should worsen with sleep, rather than improve. There are case reports of right to left shunting worsened by PAP, though his hypoxemia persisted despite PAP. His paradoxical worsening hypoxemia with wakefulness is still unexplained. Support (if any):

Anesthesia of a high-altitude area inhabitant who underwent aortic dissection emergency surgery in a low-altitude area

Heart surgery in patients from high-altitude areas is more challenging than usual. Few studies have been published on this issue, and none of them have discussed the effect of an altitude change (from high to low altitude) on a patient’s physiology or its effects on a patient’s perioperative management. Here, we present the case of a 46-year-old man who was a long-time resident of Tibetan area in Sichuan (altitude >3000 m) who underwent Stanford type A aortic dissection emergency surgery on the plain. Anesthetic management occurred through monitoring of the bispectral index (BIS) and transesophageal echocardiography (TEE), and we used a relatively loose fluid hydration strategy. The surgery was performed using cardiopulmonary bypass (CPB), deep hypothermia (DH), and selective antegrade cerebral perfusion. The most prominent anesthesia challenges for these patients are physiological changes due to habitation in an high-altitude environment (chronic hypoxemia), which can cause hyperhemoglobinemia, polycythemia, hypercoagulable blood, and even pulmonary hypertension, cor pulmonale, or congestive heart failure. Optimized perioperative management and close cooperation among the entire cardiac medical team were the key factors in the successful management of this rare case.

Prominent Eustachian Valve and Atrial Septal Defect Presenting With Chronic Hypoxemia in a Teenager

Prominent Eustachian valves, with obligate right-to-left shunts, have been reported as a cause of neonatal hypoxemia. This anomaly can present as an obstructive structure that inhibits antegrade flow through the tricuspid valve and furthermore contributes to right-to-left atrial shunting in the presence of a patent foramen ovale or atrial septal defect. This case highlights the evaluation and diagnostic workup for chronic hypoxemia in an adolescent female patient and considerations for percutaneous atrial septal defect closure.

High-Flow Oxygen Therapy During Exercise Training in Patients With Chronic Obstructive Pulmonary Disease and Chronic Hypoxemia: A Multicenter Randomized Controlled Trial

Objective The study aimed to evaluate whether high-flow oxygen therapy (HFOT) during training was more effective than oxygen in improving exercise capacity in hypoxemic chronic obstructive pulmonary disease (COPD). Methods A total of 171 patients with COPD and chronic hypoxemia were consecutively recruited in 8 rehabilitation hospitals in a randomized controlled trial. Cycle-ergometer exercise training was used in 20 supervised sessions at iso inspiratory oxygen fraction in both groups. Pre- and post-training endurance time (Tlim), 6-minute walking distance (6MWD), respiratory and limb muscle strength, arterial blood gases, Barthel Index, Barthel Dyspnea Index, COPD Assessment Test, Maugeri Respiratory Failure questionnaire, and patient satisfaction were evaluated. Results Due to 15.4% and 24.1% dropout rates, 71 and 66 patients were analyzed in HFOT and Venturi mask (V-mask) groups, respectively. Exercise capacity significantly improved after training in both groups with similar patient satisfaction. Between-group difference in post-training improvement in 6MWD (mean: 17.14 m; 95% CI = 0.87 to 33.43 m) but not in Tlim (mean: 141.85 seconds; 95% CI = −18.72 to 302.42 seconds) was significantly higher in HFOT. The minimal clinically important difference of Tlim was reached by 47% of patients in the V-mask group and 56% of patients in the HFOT group, whereas the minimal clinically important difference of 6MWD was reached by 51% of patients in the V-mask group and 69% of patients in the HFOT group, respectively. Conclusion In patients with hypoxemic COPD, exercise training is effective in improving exercise capacity. Impact Statement The addition of HFOT during exercise training is not more effective than oxygen through V-mask in improving endurance time, the primary outcome, whereas it is more effective in improving walking distance.