Obesity hypoventilation syndrome: a current review

Ventilation in the obese: physiological insights and management

Obesity can have profound adverse effects on the respiratory system, including an impact on pulmonary function, respiratory mechanics, respiratory muscle strength and endurance, gas exchange, control of breathing, and exercise capacity. Lung mechanics are modified by increased pleural pressure resulting from increased abdominal mass and subsequent peripheral airway occlusion and worsening of lung compliance due to reduced functional residual capacity without impairment of chest wall compliance. Arterial blood gases are frequently altered in these subjects and these abnormalities are directly proportional to body mass index. Mechanisms that may account for gas exchange abnormalities are multiple: ventilation/perfusion inequality (responsible for isolated hypoxaemia) and alveolar hypoventilation (responsible for so-called "obesity hypoventilation syndrome" (OHS)). Hypoventilation in obese patients results from a diversity of mechanisms, among which the two most frequently raised are mechanical limitation and blunted ventilatory drive. OHS is frequently underappreciated and diagnosis is frequently made during a first acute exacerbation. Obstructive sleep apnoea is a condition frequently associated with obesity and must be systematically screened for in this population because of its impact on morbidity and therapeutic management. Ventilatory management of these patients will depend on the patient's underlying situation, clinical presentation and physiology, including sleep study results; it may include continuous positive airway pressure or non-invasive ventilation. The goal of this narrative review is to provide a physiological-based overview of the impact of obesity on the respiratory system with a special focus on ventilatory management of patients with obesity-related respiratory disturbances.

Obesity hypoventilation syndrome, literature review

Obesity is a global health concern that has been increasing over the years, and it is associated with several pathophysiological changes affecting the respiratory system, including alveolar hypoventilation. Obesity hypoventilation syndrome (OHS) is one of the six subtypes of sleep-hypoventilation disorders. It is defined as the presence of obesity, chronic alveolar hypoventilation leading to daytime hypercapnia and hypoxia, and sleep-disordered breathing. The existence of a sleep disorder is one of the characteristics that patients with OHS present. Among them, 90% of patients have obstructive sleep apnea (OSA), and the remaining 10% of patients with OHS have non-obstructive sleep hypoventilation without OSA or with mild OSA. This review aims to provide a comprehensive understanding of the epidemiological and pathophysiological impact of OHS and to highlight its clinical features, prognosis, and severity, as well as the available treatment options.

Acute Respiratory Failure Secondary to Low-Dose Opioid Administration in a Patient With Obstructive Sleep Apnea and Obesity Hypoventilation Syndrome After Undergoing Trans-sphenoidal Tumor Resection

We present a case of an obese 56-year-old male with obstructive sleep apnea (OSA), obesity hypoventilation syndrome (OHS), and pituitary macroadenoma, who underwent nasal endoscopic trans-sphenoidal resection. Surgery was performed under general anesthesia, uneventfully as planned. The patient experienced, however, delayed emergence despite receiving adequate neuromuscular blockade agent reversal. Extubation was performed and the patient was transferred to the recovery room on a Venturi mask (50% fraction of inspired oxygen, FIO2)and 93% saturation. Postoperatively, the patient was complaining of acute pain that did not resolve with non-opioid medications and a low morphine dose (0.035 mg/kg) for pain management was administered. Subsequently, he developed severe respiratory depression, requiring intubation. After three hours, the patient was extubated, transferred to the intensive care unit, and discharged five days later. Although the patient recovered favorably, this case highlights the risks of administering opioids to patients with OSA and OHS. To our knowledge, this is the first case reporting extreme respiratory depression secondary to the administration of a very low dose of morphine in patients with these comorbidities. Therefore, it is essential to be cautious with the use of opioids and to explore multimodal pain relief methods for these patients.

Revisiting the Role of Serotonin in Sleep-Disordered Breathing

Serotonin or 5-hydroxytryptamine (5-HT) is a ubiquitous neuro-modulator-transmitter that acts in the central nervous system, playing a major role in the control of breathing and other physiological functions. The midbrain, pons, and medulla regions contain several serotonergic nuclei with distinct physiological roles, including regulating the hypercapnic ventilatory response, upper airway patency, and sleep-wake states. Obesity is a major risk factor in the development of sleep-disordered breathing (SDB), such as obstructive sleep apnea (OSA), recurrent closure of the upper airway during sleep, and obesity hypoventilation syndrome (OHS), a condition characterized by daytime hypercapnia and hypoventilation during sleep. Approximately 936 million adults have OSA, and 32 million have OHS worldwide. 5-HT acts on 5-HT receptor subtypes that modulate neural control of breathing and upper airway patency. This article reviews the role of 5-HT in SDB and the current advances in 5-HT-targeted treatments for SDB.

Wavelet Analysis of Respiratory Muscle sEMG Signals during the Physiological Breakpoint of Static Dry End-Expiratory Breath-Holding in Naive Apneists: A Pilot Study

The wavelet spectral characteristics of three respiratory muscle signals (scalenus (SC), parasternal intercostal (IC), and rectus abdominis (RA)) and one locomotor muscle (brachioradialis (BR)) were analyzed in the time-frequency (T-F) domain during voluntary breath-holding (BH), with a focus on the physiological breakpoint that is commonly considered the first involuntary breathing movement (IBM) that signals the end of the easy-going phase of BH. The study was performed for an end-expiratory BH physiological breaking point maneuver on twelve healthy, physically active, naive breath-holders/apneists (six professional athletes; six recreational athletes, and two individuals in the post-COVID-19 period) using surface electromyography (sEMG). We observed individual effects that were dependent on muscle oxygenation and each person's fitness, which were consistent with the mechanism of motor unit (MU) recruitment and the transition of slow-twitch oxidative (type 1) to fast-twitch glycolytic (type 2) muscle fibers. Professional athletes had longer BH durations (BHDs) and strong hypercapnic responses regarding the expiratory RA muscle, which is activated abruptly at higher BHDs in a person-specific range below 250 Hz and is dependent on the BHD. This is in contrast with recreational athletes, who had strong hypoxic responses regarding inspiratory IC muscle, which is activated faster and gradually in the frequency range of 250-450 Hz (independent of the person and BHD). This pilot study preliminarily indicates that it is possible to noninvasively assess the physiological characteristics of skeletal muscles, especially oxygenation, and improve physical fitness tests by determining the T-F features of elevated myoelectric IC and RA activity during BH.

The assessment and management of obstructive sleep apnoea-hypopnoea syndrome and obesity hypoventilation syndrome in obesity

Obesity is associated with respiratory dysfunction. It is a key risk and contributory factor in the sleep related breathing disorders, obstructive sleep apnoea/hypopnoea syndrome (OSAHS) and obesity hypoventilation syndrome (OHS). Weight management is an integral part of the management of these disorders, in addition to continuous positive airways pressure (CPAP) and non-invasive ventilation (NIV). Untreated, these conditions are associated with a high disease burden and as treatment is effective, early recognition and referral is critical. Best practice in on-going care is multidisciplinary.

Comparing the influence of foot reflexology and fasting mimicking diet on quality of life and sleep quality in obesity hypoventilation syndrome

OBJECTIVES

Obesity hypoventilation syndrome is one of the most serious outcomes of obesity-related respiratory difficulties, resulting in higher healthcare costs as well as increased cardio-respiratory morbidity and mortality.

METHODS

Sixty-two males who had a high risk of obstructive sleep apnea according to the STOP-BANG Sleep Apnea Questionnaire were enrolled in the study. Their age is 50-60 years old, and they have a BMI of 35-40 kg/m², daytime hypercapnia, and sleep breathing problems. The patients were divided into two equal groups at random reflexology fasting-mimicking diet groups. Weight, height, waist, and neck circumference were assessed at the beginning of the study and after two months of the intervention. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI), which is used to evaluate sleep quality. The Maugeri Obstructive Sleep Apnea Syndrome (MOSAS) questionnaire was used to assess a patient's quality of life.

RESULTS

There was a significant change in the MOSAS and PSQI questionnaires for both groups post-intervention, as the p-value was less than 0.05. The percentage change in the MOSAS questionnaire score and PSQI questionnaire was higher in the mimic diet group than in the reflexology group. Also, the mimic diet group's weight and neck circumference were considerably reduced after the intervention, with no change in the reflexology group.

CONCLUSIONS

Reflexology and a fasting-mimicking diet were found to have a substantial impact on enhancing the quality of life and sleep in people with obesity hypoventilation syndrome.

Practice recommendations for the role of physiotherapy in the management of sleep disorders: the 2022 Brazilian Sleep Association Guidelines

This clinical guideline supported by the Brazilian Sleep Association comprises a brief history of the development of Brazilian sleep physiotherapy, outlines the role of the physiotherapist as part of a sleep health team, and describes the clinical guidelines in respect of the management of some sleep disorders by the physiotherapist (including sleep breathing disorders, i.e., obstructive sleep apnea, central sleep apnea, upper airway resistance syndrome, hypoventilation syndromes and overlap syndrome, and pediatric sleep breathing disorders; sleep bruxism; circadian rhythms disturbances; insomnia; and Willis-Ekbom disease/periodic limb movement disorder. This clinical practice guideline reflects the state of the art at the time of publication and will be reviewed and updated as new information becomes available.

Brazilian Thoracic Association Consensus on Sleep-disordered Breathing

Sleep is essential for the proper functioning of all individuals. Sleep-disordered breathing can occur at any age and is a common reason for medical visits. The objective of this consensus is to update knowledge about the main causes of sleep-disordered breathing in adult and pediatric populations, with an emphasis on obstructive sleep apnea. Obstructive sleep apnea is an extremely prevalent but often underdiagnosed disease. It is often accompanied by comorbidities, notably cardiovascular, metabolic, and neurocognitive disorders, which have a significant impact on quality of life and mortality rates. Therefore, to create this consensus, the Sleep-Disordered Breathing Department of the Brazilian Thoracic Association brought together 14 experts with recognized, proven experience in sleep-disordered breathing.

Hipercapnia refractaria en paciente con síndrome de obesidad-hipoventilación maligno y COVID-19. Reporte de caso y propuesta de manejo

El síndrome de obesidad-hipoventilación asociado a la COVID-19 conduce rápidamente a la insuficiencia respiratoria aguda severa con la necesidad de ventilación mecánica invasiva, convirtiéndose en un reto terapéutico hacia el personal del cuidado intensivo debido a la ausencia de estrategias ventilatorias. A continuación se expone el caso de un paciente masculino de 51 años con antecedentes de síndrome de Pickwick que presentó neumonía grave por SARS-CoV-2, el cual progresa tempranamente a un síndrome de dificultad respiratoria aguda grave requiriendo soporte mecánico ventilatorio invasivo con presión positiva y la necesidad de soporte vasoactivo, cursando además con un síndrome de obesidad-hipoventilación de fenotipo maligno. En base a lo anterior se realiza una propuesta de manejo clínico institucional basado en la literatura científica actual del síndrome de obesidad-hipoventilación y neumonía grave secundario a SARS-CoV-2. A pesar de la alta mortalidad relacionada con la COVID-19 y la dificultad presentada durante la ventilación mecánica invasiva, el desenlace final del paciente fue favorable.

Weight Maintenance after Dietary Weight Loss: Systematic Review and Meta-Analysis on the Effectiveness of Behavioural Intensive Intervention

After a low-calorie diet, only 25% of patients succeed in maintaining the result of weight loss for a long time. This systematic review and meta-analysis aims to explore whether patients undergoing intensive intervention during the maintenance phase have a greater preservation of the weight achieved during the previous slimming phase than controls. A bibliographic search was conducted using PubMed, Scopus, and Cochrane databases for clinical trials and randomised, controlled trials investigating the role of choice in weight-loss-maintenance strategies. Only studies with a follow-up of at least 12 months were considered. A total of eight studies, for a total of 1454 patients, was identified, each comparing a group that followed a more intensive protocol to a control group. Our metanalysis highlighted that an intensive approach even in the maintenance phase could be important to ensure greater success in the phase following the weight-loss period. However, it should be pointed out that the improvement was not so different from the trend of the respective controls, with a non-statistically significant mean difference of the effect size (0.087; 95% CI −0.016 to 0.190 p = 0.098). This finding, along with the observation of a weight regain in half of the selected studies, suggests this is a long work that has to be started within the weight-loss phase and reinforced during the maintenance phase. The problem of weight control in patients with obesity should be understood as a process of education to a healthy lifestyle and a balanced diet to be integrated in the context of a multidisciplinary approach.

Elucidating Predictors of Obesity Hypoventilation Syndrome in a Large Bariatric Surgery Cohort

Rationale: Although understanding predictors of obesity hypoventilation syndrome (OHS), a condition associated with increased morbidity and mortality, is of key importance for risk prediction, existing characterization is limited.Objectives: We hypothesize that OHS patients referred for bariatric surgery have more severe obstructive sleep apnea and metabolic derangements compared with their eucapnic counterparts.Methods: A total of 1,718 patients undergoing polysomnography with end-tidal CO₂ monitoring prior to bariatric surgery at Cleveland Clinic from September 2011 to September 2018 were included. OHS was defined by body mass index (BMI) ≥ 30 kg/m² and either polysomnography-based end-tidal CO₂ ≥ 45 mm Hg or serum bicarbonate levels ≥ 27 mEq/L based on the updated European Respiratory Society guidelines. Unadjusted and multivariable logistic regression models (odds ratio; 95% confidence interval) were used to examine OHS predictors consisting of factors in domains of patient characteristics, polysomnography (cardiorespiratory and sleep architecture), laboratory, and metabolic parameters.Results: The analytic sample comprised 1,718 patients with the following characteristics: age of 45.3 ± 12.1 years, 20.7% were male, BMI = 48.6 ± 9 kg/m², and 63.6% were white individuals. OHS prevalence was 68.4%. Unadjusted analyses revealed a 1.5% increased odds of OHS (1.01; 1.00-1.03) per 1-unit BMI increase, 1.7% (1.02; 1.01-1.02) per 1% increase in sleep time Sa_O2 < 90%, 12% increase (1.12; 1.03-1.22) per 1-U increase in hemoglobin A1c, and 3.4% increased odds (1.03; 1.02-1.05) per 5-U increase in apnea-hypopnea index. The association of apnea-hypopnea index with OHS persisted after adjustment for age, sex, race, and BMI and its comorbidities (1.02; 1.01-1.04).Conclusions: OHS was highly prevalent in patients referred for bariatric surgery by more than two-thirds. Even after consideration of confounders including obesity, obstructive sleep apnea remained a strong OHS predictor, as were increasing age, male sex, nocturnal hypoxia, and impaired long-term glucose control. These findings can inform OHS risk stratification in bariatric surgery and set the stage for experimental studies to examine sleep-related respiratory and metabolic contributions to hypoventilation.

Obstructive sleep apnoea/hypopnoea syndrome: relationship with obesity and management in obese patients

Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a disease characterised by upper airway obstruction during sleep, quite frequent in the general population, even if underestimated. Snoring, sleep apnoea and diurnal hypersomnia are common in these patients. Central obesity plays a key role: it reduces the size and changes the conformation of the upper airways, besides preventing lung expansion, with consequent reduction of lung volumes. Furthermore, obese people are also resistant to leptin, which physiologically stimulates ventilation; as a result, this causes scarce awakening during apnoea. OSAHS diagnosis is based on the combination of clinical parameters, such as apnoea/hypopnoea index (AHI), medical history, physical examination and Mallampati score. The first objective reference method to identify OSAHS is polysomnography followed by sleep endoscopy. Therapy provides in the first instance reduction of body weight, followed by continuous positive airway pressure (CPAP), which still remains the treatment of choice in most patients, mandibular advancement devices (MAD) and finally otolaryngology or maxillofacial surgery. Among surgical techniques, central is barbed reposition pharyngoplasty (BRP), used in the field of multilevel surgery.

Hemorrhagic Pseudocyst: A Rare Cerebral Mass Lesion Causing Death. A Case Report and Brief Review of Literature

ABSTRACT

Mass lesions in the brain encompass a wide range neoplastic and nonneoplastic entities. These can present as a diagnostic pitfall, with nonspecific, overlapping symptoms and similar appearances on radiology. They may cause death through varied mechanisms, either specific to the underlying pathophysiology or due to the space-occupying effect of the lesion. We report a case of fatal hemorrhagic cerebral pseudocyst, a rare mass lesion, associated with a cerebral varix, causing death in a morbidly obese individual. To the best of our knowledge, there is no previous documentation in the postmortem literature of this entity as a cause of death. This case aims to document this rare entity in the differential diagnosis of a tumor-like lesion in the brain, highlight the clinical difficulty in its assessment, and demonstrate an uncommon mechanism of death, of a mass lesion acting as a focus causing seizures, with resulting hypoxia due to effects of morbid obesity and heart failure.

[Deterioration of gas exchange in subjects with an increase in body mass index at an altitude of 2,240 meters above sea level]

Introducción

Las alteraciones del intercambio gaseoso se han reconocido en la obesidad mórbida; sin embargo, no se conoce su comportamiento conforme se incrementa el índice de masa corporal.

Objetivo

Conocer el comportamiento del intercambio gaseoso a la altura de la Ciudad de México en el desarrollo de obesidad mórbida.

Métodos

Mediante un diseño transversal analítico se estudió a sujetos pareados por género y edad de cuatro grupos diferentes de índice de masa corporal (kg/m2): normal (18.5-24.9), sobrepeso (25-29.9), obesidad (30-39.9) y obesidad mórbida (≥ 40). Se obtuvieron sus antecedentes patológicos y demográficos, variables de gasometría arterial y espirometría simple. Las variables se determinaron de acuerdo con las características de la muestra; las diferencias entre grupos se realizaron mediante Anova de una vía con ajuste de Bonferroni, así como la correlación de Pearson para las variables relacionadas. Una p < 0.05 se consideró con significación estadística.

Resultados

Se estudió a 560 pacientes en cuatro grupos. La edad promedio fue de 49 ± 11 años. La mayor frecuencia de diabetes mellitus (34.29%), hipertensión arterial (50%) e hiperlipidemia (36.43%) se registró en el grupo de obesidad, y la de roncador (73.57%) en la obesidad mórbida. Se identificaron diferencias desde el grupo normal respecto de la obesidad mórbida: PaCO2 31.37 ± 2.08 vs. 38.14 ± 5.10 mmHg; PaO2 68.28 ± 6.06 vs. 59.86 ± 9.28 mmHg y SaO2 93.51 ± 1.93 vs. 89.71 ± 5.37%, todas con p = 0.0001. Correlación IMC-PaCO2: 0.497, e IMC-PaO2: -0.365, p = 0.0001, respectivamente.

Conclusiones

A la altitud de la Ciudad de México y con índice de masa corporal > 30 kg/m2, las variables relacionadas con el intercambio gaseoso y espirometría simple comienzan a deteriorarse; son evidentes con IMC > 40 kg/m2.

Introduction

Alterations of gas exchange have been recognized in morbid obesity, however, it is not known how their behavior would be as the body mass index increases.

Objective

To know the behavior of gas exchange at the level of Mexico City in the development of morbid obesity.

Methods

Through analytical design, subjects matched by gender and age were studied from four different groups of body mass index (kg/m2), normal (18.5-24.9), overweight (25-29.9), obesity (30-39.9) and morbid obesity (≥ 40). Their pathological and demographic antecedents, arterial blood gas and simple spirometry variables were obtained. The variables were shown according to their sample characteristic. The differences between groups were made using one way Anova with Bonferroni adjustment, as well as Pearson’s correlation for the related variables. Statistical significance was considered with p < 0.05.

Results

560 subjects were studied in 4 groups. The average age 49 ± 11 years old. The highest frequency of diabetes mellitus (34.29%), arterial hypertension (50%) and hiperlipidemia (36.43%) was in the obesity group, and being snoring (73.57%) in morbid obesity. There were differences from the normal group versus. morbid obesity: PaCO2 31.37 ± 2.08 versus. 38.14 ± 5.10 mmHg; PaO2 68.28 ± 6.06 versus. 59.86 ± 9.28 mmHg and SaO2 93.51 ± 1.93 versus. 89.71 ± 5.37%, all with p = 0.0001. The IMC-PaCO2 correlation: 0.497, and IMC-PaO2: −0.365, p = 0.0001 respectively.

Conclusions

At the altitude of Mexico City and body mass index > 30 kg/m2 the variables related to gas exchange and simple spirometry begin to deteriorate; are evident with BMI > 40 kg/m2.

Missed Diagnoses and Health Problems in Adults With Prader-Willi Syndrome: Recommendations for Screening and Treatment

CONTEXT

Prader-Willi syndrome (PWS) is a complex hypothalamic disorder, combining hyperphagia, hypotonia, intellectual disability, and pituitary hormone deficiencies. Annual mortality of patients with PWS is high (3%). In half of the patients, the cause of death is obesity related and/or of cardiopulmonary origin. Health problems leading to this increased mortality often remain undetected due to the complexity and rareness of the syndrome.

OBJECTIVE

To assess the prevalence of health problems in adults with PWS retrospectively.

PATIENTS, DESIGN, AND SETTING

We systematically screened 115 PWS adults for undiagnosed health problems. All patients visited the multidisciplinary outpatient clinic for rare endocrine syndromes at the Erasmus University Medical Center, Rotterdam, Netherlands. We collected the results of medical questionnaires, interviews, physical examinations, biochemical measurements, polygraphy, polysomnography, and radiology.

MAIN OUTCOME MEASURES

Presence or absence of endocrine and nonendocrine comorbidities in relation to living situation, body mass index, genotype, and demographic factors.

RESULTS

Seventy patients (61%) had undiagnosed health problems, while 1 in every 4 patients had multiple undiagnosed health problems simultaneously. All males and 93% of females had hypogonadism, 74% had scoliosis, 18% had hypertension, 19% had hypercholesterolemia, 17% had type 2 diabetes mellitus, and 17% had hypothyroidism. Unfavorable lifestyles were common: 22% exercised too little (according to PWS criteria) and 37% did not see a dietitian.

CONCLUSIONS

Systematic screening revealed many undiagnosed health problems in PWS adults. Based on patient characteristics, we provide an algorithm for diagnostics and treatment, with the aim to prevent early complications and reduce mortality in this vulnerable patient group.

Supraglottic jet oxygenation and ventilation for obese patients under intravenous anesthesia during hysteroscopy: a randomized controlled clinical trial

Background

Supraglottic jet oxygenation and ventilation (SJOV) can effectively maintain adequate oxygenation in patients with respiratory depression, even in apnea patients. However, there have been no randomized controlled clinical trials of SJOV in obese patients. This study investigated the efficacy and safety of SJOV using WEI Nasal Jet tube (WNJ) for obese patients who underwent hysteroscopy under intravenous anesthesia without endotracheal intubation.

Methods

A single-center, prospective, randomized controlled study was conducted. The obese patients receiving hysteroscopy under intravenous anesthesia were randomly divided into three groups: Control group maintaining oxygen supply via face masks (100% oxygen, flow at 6 L/min), the WNJ Oxygen Group with WNJ (100% oxygen, flow: 6 L/min) and the WNJ SJOV Group with SJOV via WNJ [Jet ventilator working parameters:100% oxygen supply, driving pressure (DP) 0.1 MPa, respiratory rate; (RR): 15 bpm, I/E; ratio 1:1.5]. SpO₂, P_ETCO₂, BP, HR, ECG and BIS were continuously monitored during anesthesia. Two-Diameter Method was deployed to measure cross sectional area of the gastric antrum (CSA-GA) by ultrasound before and after SJOV in the WNJ SJOV Group. Episodes of SpO₂ less than 95%, P_ETCO₂ less than 10 mmHg, depth of WNJ placement and measured CSA-GA before and after jet ventilation in the WNJ SJOV Group during the operation were recorded. The other adverse events were collected as well.

Results

A total of 102 patients were enrolled, with two patients excluded. Demographic characteristics were similar among the three groups. Compared with the Control Group, the incidence of P_ETCO₂ < 10 mmHg, SpO₂ < 95% in the WNJ SJOV group dropped from 36 to 9% (P = 0.009),from 33 to 6% (P = 0.006) respectively,and the application rate of jaw-lift decreased from 33 to 3% (P = 0.001), and the total percentage of adverse events decreased from 36 to 12% (P = 0.004). Compared with the WNJ Oxygen Group, the use of SJOV via WNJ significantly decreased episodes of SpO₂ < 95% from 27 to 6% (P = 0.023), P_ETCO₂ < 10 mmHg from 33 to 9% (P = 0.017), respectively. Depth of WNJ placement was about 12.34 cm in WNJ SJOV Group. There was no significantly difference of CSA-GA before and after SJOV in the WNJ SJOV Group (P = 0.234). There were no obvious cases of nasal bleeding in all the three groups.

Conclusions

SJOV can effectively and safely maintain adequate oxygenation in obese patients under intravenous anesthesia without intubation during hysteroscopy. This efficient oxygenation may be mainly attributed to supplies of high concentration oxygenation to the supraglottic area, and the high pressure jet pulse providing effective ventilation. Although the nasal airway tube supporting collapsed airway by WNJ also plays a role. SJOV doesn’t seem to increase gastric distension and the risk of aspiration. SJOV can improve the safety of surgery by reducing the incidence of the intraoperative involuntary limbs swing, hip twist and cough.

Trial registration

Chinese Clinical Trial Registry. Registration number, ChiCTR1800017028, registered on July 9, 2018.