Severe Hypoxemia Research Articles

Hypoxia-altitude simulation test to predict altitude-related adverse health effects in COPD patients.

Amongst numerous travellers to high altitude (HA) are many with the highly prevalent COPD, who are at particular risk for altitude-related adverse health effects (ARAHE). We then investigated the hypoxia-altitude simulation test (HAST) to predict ARAHE in COPD patients travelling to altitude. This prospective diagnostic accuracy study included 75 COPD patients: 40 women, age 58±9 years, forced expiratory volume in 1 s (FEV1) 40-80% pred, oxygen saturation measured by pulse oximetry (S pO2 ) ≥92% and arterial carbon dioxide tension (P aCO2 ) <6 kPa. Patients underwent baseline evaluation and HAST, breathing normobaric hypoxic air (inspiratory oxygen fraction (F IO2 ) of 15%) for 15 min, at low altitude (760 m). Cut-off values for a positive HAST were set according to British Thoracic Society (BTS) guidelines (arterial oxygen tension (P aO2 ) <6.6 kPa and/or S pO2 <85%). The following day, patients travelled to HA (3100 m) for two overnight stays where ARAHE development including acute mountain sickness (AMS), Lake Louise Score ≥4 and/or AMS score ≥0.7, severe hypoxaemia (S pO2 <80% for >30 min or 75% for >15 min) or intercurrent illness was observed. ARAHE occurred in 50 (66%) patients and 23 out of 75 (31%) were positive on HAST according to S pO2 , and 11 out of 64 (17%) according to P aO2 . For S pO2 /P aO2 we report a sensitivity of 46/25%, specificity of 84/95%, positive predictive value of 85/92% and negative predictive value of 44/37%. In COPD patients ascending to HA, ARAHE are common. Despite an acceptable positive predictive value of the HAST to predict ARAHE, its clinical use is limited by its insufficient sensitivity and overall accuracy. Counselling COPD patients before altitude travel remains challenging and best focuses on early recognition and treatment of ARAHE with oxygen and descent.

Bilevel positive airway pressure for gastroscopy with sedation in patients at risk of hypoxemia: A prospective randomized controlled study

Study objectiveHypoxemia is one of the most frequent adverse events during sedated gastroscopy, and there is still no effective means to prevent and cure it. Therefore, we conducted this randomized trial to confirm our hypothesis that, compared with the nasal cannula group, bilevel positive airway pressure (BPAP) would decrease the incidence of hypoxemia in patients with obstructive sleep apnea (OSA) or overweight status undergoing gastroscopy. DesignIn a single-center, prospective, randomized controlled clinical trial, 80 patients aged 18–65 years and with OSA or overweight status who underwent gastroscopy with sedation were randomly assigned to two groups: the nasal cannula and BPAP groups. The primary outcome was the incidence of hypoxemia (75% < peripheral oxygen saturation [SpO2] < 90% for >5 sand <60 s). Main resultsCompared to the nasal cannula group, BPAP therapy significantly decreased the incidence of hypoxemia from 40.0% to 2.5% (absolute risk difference [ARD], 37.5% [95% confidence interval (CI), 21.6 to 53.4], p < 0.001), decreased subclinical respiratory depression from 52.5% to 22.5% (ARD, 30.0% [95% CI, 9.8 to 50.2], p = 0.006), and decreased severe hypoxemia from 17.5% to 0% (ARD, 17.5% [95% CI, 5.7 to 29.3], p = 0.006). The BPAP intervention also decreased the total propofol dosage and operation time and improved anesthesiologist's satisfaction. ConclusionBPAP therapy significantly decreased the incidence of hypoxemia in patients with OSA or overweight status who underwent gastroscopy.

Obstructive sleep apnea and pulmonary hypertension: the pendulum swings again.

Obstructive sleep apnea and pulmonary hypertension: the pendulum swings again.

1116. Comparative Efficacy of Tocilizumab and Baricitinib in Treatment of Severe COVID-19 Infections

Abstract Background Tocilizumab (TOCI) and baricitinib (BARI) have been shown to improve mortality in patients with severe COVID-19. However, there is limited comparative data between the two agents head to head. The purpose of this study was to evaluate patient characteristics and efficacy of BARI versus TOCI for the treatment of severe COVID-19. Methods A retrospective, observational chart review was conducted during September 2020 to November 2021 in a three hospital health system in New Jersey. Hospitalized patients were included if they were ≥ 18 years old, requiring supplemental oxygenation and being treated for severe COVID-19 with TOCI. These patients were then matched based on BMI, age, and severity of hypoxemia with patients who received BARI. Patients were excluded if they required invasive mechanical ventilation (IMV) at the start of therapy. The primary outcome of the study was to assess incidence of all cause inpatient mortality (ACIM) in patients receiving TOCI or BARI. A subgroup analysis was performed that assessed clinical improvement and progression to IMV between both treatment groups. Secondary endpoints included analysis of independent variables associated with ACIM. Results Total of 194 patients were screened for eligibility and of these 87 patients in the TOCI group were matched with 87 patients in the BARI group. Overall, there was no difference seen in ACIM between TOCI compared to BARI (22% vs 33% OR 1.11 (0.49-2.71, P=0.18). For subgroup analysis, more patients in TOCI group experienced clinical improvement compared to BARI group (44% vs 22%, P=0.004). Additionally, patients in TOCI group were less likely to progress to require IMV (10% vs 26%, P=0.02). When logistic regression model was used to assess mortality predicting factors, patients receiving BARI who required ICU level of care (OR 2.10, CI 0.91-0.08, p=0.00055) and IMV (OR 2.40, CI 1.16-3.64, p=0.00015) had higher odds of ACIM compared to TOCI. Mortality predicting factors among patients receiving tocilizumab or baricitinib Conclusion There was no difference seen in ACIM between TOCI and BARI. At the end of hospitalization patients receiving TOCI were more likely to experience clinical improvement compared to BARI. TOCI should be preferred in patients requiring ICU level of care and IMV. Disclosures All Authors: No reported disclosures.

Prone Positioning During Venovenous Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome-Better Together?

Prone Positioning During Venovenous Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome-Better Together?

Antibiotic treatment failure in children aged 1 to 59 months with World Health Organization-defined severe pneumonia in Malawi: A CPAP IMPACT trial secondary analysis.

Pneumonia is a leading cause of mortality in children <5 years globally. Early identification of hospitalized children with pneumonia who may fail antibiotics could improve outcomes. We conducted a secondary analysis from the Malawi CPAP IMPACT trial evaluating risk factors for antibiotic failure among children hospitalized with pneumonia. Participants were 1-59 months old with World Health Organization-defined severe pneumonia and hypoxemia, severe malnutrition, and/or HIV exposure/infection. All participants received intravenous antibiotics per standard care. First-line antibiotics were benzylpenicillin and gentamicin for five days. Study staff assessed patients for first-line antibiotic failure daily between days 3-6. When identified, patients failing antibiotics were switched to second-line ceftriaxone. Analyses excluded children receiving ceftriaxone and/or deceased by hospital day two. We compared characteristics between patients with and without treatment failure and fit multivariable logistic regression models to evaluate associations between treatment failure and admission characteristics. From June 2015-March 2018, 644 children were enrolled and 538 analyzed. Antibiotic failure was identified in 251 (46.7%) participants, and 19/251 (7.6%) died. Treatment failure occurred more frequently with severe malnutrition (50.2% (126/251) vs 28.2% (81/287), p<0.001) and amongst those dwelling ≥10km from a health facility (22.3% (56/251) vs 15.3% (44/287), p = 0.026). Severe malnutrition occurred more frequently among children living ≥10km from a health facility than those living <10km (49.0% (49/100) vs 35.7% (275/428), p = 0.014). Children with severe malnutrition (adjusted odds ratio (aOR) 2.2 (95% CI 1.52, 3.24), p<0.001) and pre-hospital antibiotics ((aOR 1.47, 95% CI 1.01, 2.14), p = 0.043) had an elevated aOR for antibiotic treatment failure. Severe malnutrition and pre-hospital antibiotic use predicted antibiotic treatment failure in this high-risk severe pneumonia pediatric population in Malawi. Our findings suggest addressing complex sociomedical conditions like severe malnutrition and improving pneumonia etiology diagnostics will be key for better targeting interventions to improve childhood pneumonia outcomes.

Bilateral diaphragm paralysis: a clinical case

Diaphragm dysfunction is a rare cause of respiratory distress with a variety of clinical manifestations that complicate diagnosis and treatment. The given clinical case demonstrates the possibility of detecting bilateral diaphragm paralysis using available general clinical and instrumental diagnostic methods. Among the physical data, high standing of the lower borders of the lungs with limited mobility and paradoxical movement of the diaphragm during the Mueller test have a high diagnostic value. Chest X-ray demonstrates the high standing of both domes of the diaphragm and subsegmental atelectasis in the basal parts of the lungs. Severe hypoxemia developed: oxygen saturation in clino- and orthostasis was 72 and 96%, respectively. The tests of pulmonary function showed significant restrictive impairments, a decrease in the vital capacity of the lungs was also determined. Ultrasound examination of the diaphragm revealed hyperechogenicity, lack of inspiratory thickening, and respiratory mobility of the domes of the diaphragm. Electromyography confirmed gross right and left phrenic nerve axonopathy. An idiopathic variant of diaphragm dysfunction can be assumed based on the patient stabilization during CPAP therapy, physiotherapy exercises, chest massage, followed by the disappearance of signs of bilateral diaphragm paralysis. Conclusion. The presented case demonstrates the difficulties of diagnosing bilateral diaphragm paralysis. The final diagnosis was made through the use of specific research methods recommended for suspected diaphragm dysfunction. The prognosis of the idiopathic variant of bilateral diaphragm paralysis, as in this case, is favorable. Spontaneous remission was observed.

The Heavy Heart: An Unusual Cause of Ventricular Tachycardia

A 17-year-old female presented to the emergency department with a one-hour history of abdominal pain, nausea, vomiting and weakness. Physical examination on admission revealed a heart rate of 106 beats per minute, blood pressure of 136/88 mmHg and a respiratory rate of 25 breaths per minute. Her medical history was unremarkable with no prior medical comorbidities or surgical history. She denied taking any prescribed or over the counter medications. The initial ECG showed ventricular tachycardia (VT) (Figure 1), with investigations revealing a normal troponin I level of <0.03ng/ml (reference range <0.3 ng/mL), elevated N-terminal pro-brain natriuretic peptide level of 439.2 ng/L (reference range <300 ng/L) and normal serum potassium level of 4.0 mmol/L (reference range 3.5-5.3 mmol/L). Over the next hours, the patient developed shallow respirations, with rapid worsening of muscle weakness involving all four limbs. An arterial blood gas obtained on room air revealed severe acidosis (pH, 7.178) and hypoxemia (PaO2, 65.8 mmHg). A repeated blood test conducted four hours after admission noted profound hypokalemia (serum potassium, 1.9 mmol/L).

COVID-19 in elderly: Correlations of viral load, clinical course, laboratory parameters, among patients vaccinated with CoronaVac.

SARS-CoV-2 virus was initially identified in Wuhan, China, in December 2019 and a global pandemic was declared in March 2020 by World Health Organization. COVID-19 disease is characterized with severe pneumonia and hypoxemia, especially in the elderly population. The elderly population was primarily vaccinated with CoronaVac, which is a whole virion inactivated vaccine (Sinovac Biotech, China) in Turkey. This study aimed to investigate the association of viral load and laboratory parameters with the severity of the disease and vaccination status in elderly (older than 60 years old) COVID-19 patients. The age range of the patients was 61-97 years old with a mean of 71.80. Vaccinated patients had a lower viral load (P = 0.253) in nasopharyngeal swabs during breakthrough COVID-19 infection compared to unvaccinated ones and were hospitalized for a shorter period of time in hospital wards (P = 0.035). A lower number of patients were vaccinated in both moderate (n = 33, 29.20%) and severe/critical group (n = 46, 34.07%) (P = 0.412). Only 17 (32.08%) vaccinated patients were hospitalized in an intensive care unit (ICU), whereas 36 (67.92%) of the ICU patients were unvaccinated (P= 0.931). Severe/critical patients had higher c-reactive protein (CRP), platelet-to-lymphocyte ratio (PLR), fibrinogen, ferritin, and lactate dehydrogenase (LDH) levels compared to the moderate group on the admission day (P < 0.05). Our study suggested that elderly patients vaccinated with CoronaVac had a shorter stay in hospitals and according to our results CRP, PLR, fibrinogen, ferritin, and LDH levels could be used to determine the severity of the infections.

Acute Onset of Refractory Hypoxemia: A Rare Hemodynamic Cause of Dyspnea

Platypnea-orthodeoxia syndrome (POS) is a rare condition of positional dyspnea with hypoxemia that can pose a diagnostic challenge to clinicians. We report two cases of POS with different pathophysiologic triggers and similar clinical features. In our report, both patients manifested a severe hypoxemia with low response to increase of fractional inspired oxygen, unremarkable physical examination of the lungs, and no radiological findings of the pulmonary embolism. In both cases, an interatrial communication was found in association with a right-to-left interatrial shunting. Recognition of POS is crucial because symptoms can be quickly relieved by recumbency, unlike other types of hypoxemia. This simple solution may prevent the use of sedative therapy, invasive ventilatory support, and vasopressor agents, which could even exacerbate the right-to-left extrapulmonary shunt and worsen clinical conditions.

Role of Oral Valganciclovir in Sick Preterm with Cytomegalovirus Virus Infection and Ventilation Dependence

Cytomegalovirus (CMV) is the most common congenital viral infection in neonates. Postnatal infection regarding infants rarely has significant clinical consequences. However, preterm may be at higher risk of developing symptomatic postnatal CMV disease. A multipara woman delivered vaginally a male preterm infant at 30 weeks' gestation who was suspected of early-onset sepsis in view of chronic leaking. The baby developed severe hypoxemia, and persistent pulmonary hypertension after delivery, with progressive deterioration and minimal effect of advanced ventilation, antibiotics, and pulmonary vasodilators. Sepsis screen and cultures for bacteria and fungi were negative. The baby was having enlarged liver and spleen which was noticed on day 15 of life. TORCH titer of the baby revealed CMV IgM and subsequently, CMV was isolated in the urine and in the blood plasma by polymerase chain reaction. Oral valganciclovir improved hematological parameters of the baby and respiratory support could be weaned. CMV being the most common intrauterine infection should be considered in differential diagnosis in unusual presentation of suspected sepsis and oral valganciclovir can be considered as good option for treatment.

Prone Ventilation in ARDS

ARDS is a clinical syndrome characterised by severe refractory hypoxaemia associated with significant mortality and morbidity. Low tidal volume ventilation and restricting plateau pressure has got maximum survival benefit. Various others measures to tackle refractory hypoxaemia in patients with ARDS have been studied. Prone ventilation is one such rescue therapy which has shown promising results. This article is intended to discuss the benefits of prone ventilation and to clarify some of the common queries one has in practising prone ventilation.

Growth Arrest of Alveolar Cells in Response to Cytokines from Spike S1-Activated Macrophages: Role of IFN-γ.

Acute respiratory distress syndrome (ARDS) is characterized by severe hypoxemia and high-permeability pulmonary edema. A hallmark of the disease is the presence of lung inflammation with features of diffuse alveolar damage. The molecular pathogenetic mechanisms of COVID-19-associated ARDS (CARDS), secondary to SARS-CoV-2 infection, are still not fully understood. Here, we investigate the effects of a cytokine-enriched conditioned medium from Spike S1-activated macrophage on alveolar epithelial A549 cells in terms of cell proliferation, induction of autophagy, and expression of genes related to protein degradation. The protective effect of baricitinib, employed as an inhibitor of JAK-STAT, has been also tested. The results obtained indicate that A549 exhibits profound changes in cell morphology associated to a proliferative arrest in the G0/G1 phase. Other alterations occur, such as a blockade of protein synthesis and the activation of autophagy, along with an increase of the intracellular amino acids content, which is likely ascribable to the activation of protein degradation. These changes correlate to the induction of IFN-regulatory factor 1 (IRF-1) due to an increased secretion of IFN-γ in the conditioned medium from S1-activated macrophages. The addition of baricitinib prevents the observed effects. In conclusion, our findings suggest that the IFN-γ-IRF-1 signaling pathway may play a role in the alveolar epithelial damage observed in COVID-19-related ARDS.

High-Flow Nasal Cannula Therapy for Respiratory Support in Adult Intensive Care Unit Patients

What is the effectiveness of high-flow nasal cannula (HFNC) therapy compared with standard oxygen therapy, noninvasive ventilation, or noninvasive positive pressure (NIPPV) ventilation for respiratory support in adults in the intensive care unit?Critically ill patients are at high risk for severe hypoxemia that can lead to significant tissue damage and death if not corrected. Supplemental oxygen can be delivered via multiple methods, including mechanical ventilation, noninvasive ventilation, NIPPV, HFNC therapy, and low-flow nasal cannula (LFNC) therapy.1 Up to 40% of all patients admitted to the intensive care unit (ICU) receive mechanical ventilation; although this method is often necessary, it presents risks and potential complications, including trauma to the pulmonary system and increased mortality.2,3To avoid these complications, the use of alternative methods of respiratory support that can provide adequate oxygen levels is often considered. Use of LFNC therapy can be helpful but often cannot provide a sufficiently high level of oxygen for critically ill patients. However, HFNC therapy can provide high levels of oxygen, and its use in the ICU has been growing in recent years.4High-flow nasal cannula therapy delivers heated and humidified oxygen via the nose at high flow rates of up to 60 L/min. The high flow rates produce low levels of positive pressure in the upper airways, which can clear out expired carbon dioxide, leading to reduced work of breathing and decreased respiratory rate.5 Noninvasive positive pressure ventilation, which refers primarily to continuous positive airway pressure or bilevel positive airway pressure ventilation, can be used when patients require high levels of supplemental oxygen and need some level of mechanical support. The oxygen is delivered via a tight-fitting mask, typically over the nose, mouth, or both; this mask can be uncomfortable and make it difficult to maintain adequate positioning.6The purpose of this review was to compare the efficacy and safety of HFNC therapy with those of the other common noninvasive respiratory support methods in the ICU setting.This summary was based on an update to a previously published systematic review conducted in 2017.7 As new evidence on a topic becomes available, updates are necessary to account for the results that the new evidence presents. This update, conducted by Lewis et al,8 included 31 randomized controlled trials comprising 5136 adult participants. The authors of this review investigated several outcomes, with the primary ones being treatment failure (need to escalate to invasive ventilation), in-hospital mortality, and adverse events (pneumonia).The authors independently assessed the risk of bias for each study, including selection, performance, detection, attrition, reporting, and publication biases. They resolved any disagreements by reviewing the data together and through discussion.Lewis et al8 used risk ratios (RRs) with 95% CIs for dichotomous outcomes as measures of treatment effect between various comparisons and outcomes. They used the internationally approved Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach to determine the certainty of evidence—high, moderate, low, or very low—for each outcome9: This review showed that, overall, there was little or no difference in the evidence when comparing HFNC use with standard oxygen therapy or NIPPV in the outcomes explored. There was low-certainty evidence showing that HFNC therapy may lead to less treatment failure compared with standard oxygen therapy, with the classification of low certainty based on heterogeneity (differences in how the studies were conducted) and an unclear risk of bias in the studies.Currently, more than 50 studies are being conducted on the use of HFNC therapy; this high level of research activity is likely related to the increase in the use of HFNC therapy resulting from the COVID-19 pandemic. Upon publication, these studies can be added to the evaluation to provide additional guidance.The evidence from this systematic review can affect the decisions of clinical care teams when they are creating treatment plans for critically ill patients. Advocating for the best evidence-based treatment remains an important part of the role of critical care nurses. We must always consider the best available evidence and understand the feasibility, appropriateness, meaningfulness, and effectiveness of any intervention to determine whether it is suitable to implement in our individual context.

Risk factors of transient tachypnea of the newborn developing into pulmonary hypertension of the newborn: a case-control study.

Transient tachypnea of the newborn (TTN) is the consequence of delayed resorption of lung fluid. When TTN develops, the infant may develop severe hypoxemia and progress to persistent pulmonary hypertension of the newborn (PPHN). To examine factors associated with the development of PPHN in TTN infants. This retrospective study comprised 23 infants in whom a diagnosis of TTN with PPHN (TTN-PPHN) was confirmed and 59 infants with severe TTN without PPHN who required mechanical ventilation between 2009 and 2018 at Songklanagarind Hospital, Thailand. Logistic regression was used to assess factors associated with TTN and PPHN. The factors identified by univariate analysis that were associated with development of PPHN were oxygen saturation (SpO2) <90% and respiratory rate (RR) ≥70 breaths/min at the time of admission, mean airway pressure (MAP) ≥8 cmH2O, oxygen index (OI) ≥10, partial pressure of oxygen (PaO2) ≤60, partial pressure of carbon dioxide (PCO2) ≥45 mmHg, and infants who did not receive positive pressure ventilation (PPV). In multivariate analyses, RR ≥70 breaths/min (adjusted odds ratio [aOR] 9.96, 95% confidence interval [CI] 2.1-47.29, P < 0.001) and OI ≥10 (aOR 29.22, 95% CI 4.46-191.23, P < 0.001) remained statistically significantly associated with PPHN. High RR and high OI were factors associated with PPHN in TTN infants.

Use of Palliative Oxygen in Cancer Patients.

Background: Despite the lack of evidence to support the use of palliative oxygen to relieve dyspnea at the end of life, its prescription is widespread and often supported by local and national practice guidelines. Objectives: The objectives of this study were (1) to determine to what extent oxygen prescriptions meet the proposed prescription criteria in our institution, (2) to examine the indication of individual prescriptions in relation to the severity of dyspnea and (3) to review the utilization of opioids in patients receiving palliative oxygen. Methods: Retrospective chart review of cancer patients who were prescribed palliative oxygen between April 2015 and January 2020 through a respiratory home care program in Quebec City, Canada. According to provincial prescription guidelines, palliative oxygen was provided and reimbursed in case of severe hypoxemia (pulse oximetry saturation at rest < 88%) in cancer patients with an estimated prognosis of less than 3months. Results: 134 patients receiving palliative oxygen were included; 25 (19%) did not fulfill reimbursement criteria. Median survival was 44 days. At initiation of palliative oxygen, 48 patients (36%) had only mild or moderate dyspnea (Medical Research Council dyspnea score 1-3), 26 (19%) did not receive opioids, and 9 (7%) were prescribed palliative oxygen without being dyspneic or receiving opioids. Conclusion: Most prescriptions of palliative oxygen met the proposed prescription criteria in our institution. Half of those who received palliative oxygen were only mildly dyspneic and/or were not receiving opioids at the time of the prescription.

Immunomodulators in Mechanically Ventilated Patients With COVID-19: Lessons Learned From Underpowered Trials.

Immunomodulators in Mechanically Ventilated Patients With COVID-19: Lessons Learned From Underpowered Trials.

Acute respiratory distress syndrome following administration of gadolinium contrast agent: a case report

BackgroundGadolinium-based contrast agents are used extensively in magnetic resonance imaging to assist diagnosis of medical conditions. Despite their documented safety profile, severe adverse events do occur, and their documentation may serve to raise the awareness of the medical community.Case presentationWe report the case of a 15-year-old white Latin American female patient admitted to the intensive care unit for acute respiratory distress syndrome following administration of gadolinium. She did not have rash or tongue swelling but developed hypotension responsive to fluid administration and severe hypoxemia. Chest computed tomography revealed bilateral pulmonary compromise with multiple confluent consolidations. She received methylprednisolone and noninvasive ventilatory support including bilevel positive airway pressure ventilation and high-flow nasal cannula, and underwent a rapid recovery.ConclusionGadolinium-based contrast agent-induced acute respiratory distress syndrome, albeit rare, should be included in the differential diagnosis of respiratory failure shortly after magnetic resonance imaging, which is nowadays a frequent diagnostic procedure, potentially increasing the awareness of this serious complication.

P116 Increased airflow limitation during nocturnal respiratory events is associated with increased psychomotor vigilance task lapses in obstructive sleep apnoea patients

Abstract Introduction Impaired daytime vigilance is common in obstructive sleep apnoea (OSA) patients. However, the apnoea-hypopnea index (AHI) has been shown to have a weak correlation with daytime vigilance. This may be because the AHI only quantifies respiratory event frequency. Thus, we aimed to test our hypothesis that increased airflow limitation during nocturnal respiratory events is associated with daytime vigilance impairment. Methods 495 OSA patients (AHI≥5) completed a psychomotor vigilance task (PVT) and in-lab polysomnographic recording. The number of lapses (response time &amp;gt;500ms) was the primary outcome. Airflow limitation was quantified from nasal airflow using a validated algorithm. Linear regression models were adjusted for age, sex, and body mass index. Results The percentage of flow-limited breaths during respiratory events was associated with the number of PVT lapses (R=0.119, p&amp;lt;0.05); AHI was not (p&amp;gt;0.05). One standard deviation (SD, 20%) increase in the percentage of flow-limited breaths during respiratory events increased the number of lapses by 2.5. This effect-size was greater than that for age (one SD increase, 12.5 years, increased the number of lapses by 1.3). These results were similar after adjusting for AHI, arousal index, and desaturation event area. Similar findings were observed using the percentage of flow-limited breaths during all sleep. Discussion Increased airflow limitation during nocturnal respiratory events was associated with decreased daytime vigilance in OSA patients. This association appeared to be independent of respiratory event frequency, arousal frequency, and hypoxaemia severity. This suggests that disproportionately large ventilatory drive versus achieved ventilation (i.e. flow-limitation) contributes to daytime vigilance impairment.

Abstract 14839: Clinical, Polysomnographic and Echocardiographic Correlates of Excessive Daytime Sleepiness

Introduction: Excessive Daytime Sleepiness (EDS) has been associated with adverse CVD outcomes. However, the mechanisms of elevated CVD risk in persons with EDS remains uncertain. In this study, we examined polysomnographic and echocardiographic correlates of EDS in a population of adults who underwent both sleep and cardiac stress tests. Methods: We analyzed data from 264 participants who had an in-lab polysomnogram (PSG) and a cardiac stress test between 2016 and 2019. All patients completed the Epworth Sleepiness Scale (ESS) questionnaire. EDS was categorized into 3 groups no EDS (ESS&lt;10), non-severe EDS (ESS 10-14), and severe EDS (ESS ≥15). T90%, the percentage of sleep time spent with oxygen desaturation &lt; 90%, was categorized into severe (≥ 20%) and non-severe nocturnal hypoxemia (&lt;20%). We assessed the relationship between EDS and CV risk factors, and EDS and echocardiographic parameters of diastolic dysfunction such as the E/e’, E/A ratio, left atrial volume index, tricuspid regurgitation jet velocity, and systolic function (ejection fraction, EF). Results: The mean age (SD) of the participants was 59 (11) years, and 59% were female. In logistic regression analysis severe EDS was associated with &gt;3-fold odds of a history of stroke or TIA [a OR 3.2 (95%CI:1.2-8.2), P=0.017] and nearly 4 times the odds of severe nocturnal hypoxemia [aOR 3.8 (95%CI: 1.7-8.6, P=0.002] compared to those with no EDS. We found no other association between EDS and demographic or CV characteristics or PSG variables. In the subset of patients with available echocardiogram data (n=199 - 213), there was no association between EDS and EF or echocardiographic parameters of diastolic dysfunction. Conclusions: EDS is strongly associated with severe nocturnal hypoxia and a history of stroke or TIA in adults with OSA. Further studies are needed to characterize the relationship between EDS and CVD.