Moderate concentrations of supplemental oxygen worsen hypercapnia in obesity hypoventilation syndrome: a randomised crossover study

Comparison of high-flow nasal cannula and conventional nasal cannula during deep sedation for endoscopic submucosal dissection: a randomized controlled trial

PURPOSE

Adequate oxygenation and airway management during deep sedation can be challenging. We investigated the effect of high-flow nasal cannula (group HF) and conventional nasal cannula (group CO) during sedation for endoscopic submucosal dissection (ESD).

METHODS

Patients undergoing ESD with deep sedation were enrolled. The primary outcome was difference in lowest oxygen saturation (SpO2) between the groups. Incidence of hypoxia (SpO2 < 90%), patients with SpO2 < 95%, hypercapnia, and airway interventions; operator satisfaction; and adverse events were recorded.

RESULTS

Thirty-two patients in each group completed the study. The mean of minimum SpO2 values was significantly higher in group HF than in group CO (96.8% ± 4.2% vs. 93.3% ± 5.3%, p = 0.005). The incidence of hypoxia was comparable between the groups (4 [12.5%] vs. 6 [18.8%], p = 0.491); however, patients with SpO2 < 95% were significantly less in group HF (5 [15.6%] vs. 18 [56.3%], p = 0.003). Incidence of hypercapnia was higher in group HF than in group CO (14 [46.7%] vs. 5 [16.7%], p = 0.013). Airway rescue interventions were significantly less common in group HF. Satisfaction of operators and post-procedural complications were comparable between the two groups. In multivariable analysis, group CO and higher body mass index were risk factors for airway managements (odds ratio [95% confidence interval]: 6.204 [1.784-21.575], p = 0.004; 1.337 [1.043-1.715], p = 0.022, respectively).

CONCLUSIONS

Compared to conventional nasal cannula, high-flow nasal cannula maintained higher minimum SpO2 value during deep sedation with propofol-remifentanil for ESD.

TRIAL REGISTRATION

Clinical Trial Registry of the Republic of Korea (KCT0006618, https://cris.nih.go.kr ; registered September 29, 2021; principal investigator: Ji Won Choi).

Oxygen-induced hypercapnia: physiological mechanisms and clinical implications

Oxygen is probably the most commonly prescribed drug in the emergency setting and is a life-saving modality as well. However, like any other drug, oxygen therapy may also lead to various adverse effects. Patients with chronic obstructive pulmonary disease (COPD) may develop hypercapnia during supplemental oxygen therapy, particularly if uncontrolled. The risk of hypercapnia is not restricted to COPD only; it has also been reported in patients with morbid obesity, asthma, cystic fibrosis, chest wall skeletal deformities, bronchiectasis, chest wall deformities, or neuromuscular disorders. However, the risk of hypercapnia should not be a deterrent to oxygen therapy in hypoxemic patients with chronic lung diseases, as hypoxemia may lead to life-threatening cardiovascular complications. Various mechanisms leading to the development of oxygen-induced hypercapnia are the abolition of ‘hypoxic drive’, loss of hypoxic vasoconstriction and absorption atelectasis leading to an increase in dead-space ventilation and Haldane effect. The international guideline recommends a target oxygen saturation of 88% to 92% in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and other chronic lung diseases at risk of hypercapnia.  Oxygen should be administered only when oxygen saturation is below 88%. We searched PubMed, EMBASE, and the CINAHL from inception to June 2022. We used the following search terms: “Hypercapnia”, “Oxygen therapy in COPD”, “Oxygen-associated hypercapnia”, “oxygen therapy”, and “Hypoxic drive”. All types of study are selected. This review will focus on the physiological mechanisms of oxygen-induced hypercapnia and its clinical implications.

Impact of Oxygen Saturation on Mortality in Obese and Non-obese Critically Ill Patients With Mechanical Ventilation: A Retrospective Observational Study

Background

The main aim of this study was to evaluate the effect of oxygen saturation on mortality in critically ill patients with mechanical ventilation according to obesity status.

Methods

We conducted an observational study in mechanically ventilated patients admitted to the ICU retrospectively. Demographic, arterial blood gas, ventilator setting, interventions, and peripheral oxygen saturation (Spo₂) during the first 24 h were recorded and analyzed between non-obese and obese patients. The main exposure included Spo₂, time-weighted mean Spo₂ (TWM-Spo₂), and proportion of time spent in different Spo₂ (PTS-Spo₂) levels. The primary outcome was hospital mortality. We used multivariable logistic regression models to assess the relationship between Spo₂ and mortality, as well as the interaction between PTS-Spo₂ and obesity status.

Results

A total of 25,100 patients were included, of which 10,564 (42%) were obese patients. After adjusting for confounders, compared with TWM-Spo₂ of 94–98%, TWM-Spo₂ of < =88% (OR 3.572; CI [2.343, 5.455]; p < 0.001) and of 89–93% (OR 1.514; CI [1.343, 1.706]; p < 0.001) were both associated with higher risk of mortality. PTS-Spo₂ of 99–100% was associated with increased risk of mortality for obese patients (OR 1.028; 95% CI 1.010–1.046; p = 0.002; P_{interaction =} 0.001), while PTS-Spo₂ of 89–93% was associated with increased risk of mortality (OR 1.089; 95% CI 1.051–1.128; p < 0.001; P_{interaction =} 0.001) for non-obese patients.

Conclusions

For obese and non-obese critically ill patients with mechanical ventilation, the impact of oxygen saturation on hospital mortality is different.

Optimal Noninvasive Medicare Access Promotion: Patients with Hypoventilation Syndromes A Technical Expert Panel Report from the American College of Chest Physicians, the American Association for Respiratory Care, the American Academy of Sleep Medicine, and the American Thoracic Society

The existing coverage criteria for home noninvasive ventilation (NIV) do not recognize the diversity of hypoventilation syndromes and advances in technologies. This document summarizes the work of the Hypoventilation Syndromes Technical Expert Panel working group. The most pressing current coverage barriers identified were: 1) overreliance on arterial blood gases (particularly during sleep); 2) need to perform testing on prescribed oxygen; 3) requiring a sleep study to rule out obstructive sleep apnea as the cause of sustained hypoxemia; 4) need for spirometry; 5) need to demonstrate BPAP without a backup rate failure to qualify for BPAP S/T; and 6) qualifying hospitalized patients for home NIV therapy at the time of discharge. Critical evidence support for changes to current policies include randomized clinical trial evidence and clinical practice guidelines. In order to decrease morbidity-mortality by achieving timely access to NIV for patients with hypoventilation, particularly those with obesity hypoventilation syndrome, we make the following key suggestions: 1) Given the significant technological advances, we advise acceptance of surrogate noninvasive end tidal and transcutaneous PCO₂ and venous blood gases in lieu of arterial blood gases,; 2) Not requiring PCO₂ measures while on prescribed oxygen; 3) Not requiring a sleep study to avoid delays in care in patients being discharged from the hospital; 4) Remove spirometry as a requirement; 5) Not requiring BPAP without a backup rate failure to approve BPAP S/T. The overarching goal of the Technical Expert Panel is to establish pathways that improve clinicians' management capability to provide Medicare beneficiaries access to appropriate home NIV therapy. Adoption of these proposed suggestions would result in the right device, at the right time, for the right type of patients with hypoventilation syndromes.

Obesity and Obesity Hypoventilation, Sleep Hypoventilation, and Postoperative Respiratory Failure

Obesity hypoventilation syndrome (OHS) is considered as a diagnosis in obese patients (body mass index [BMI] ≥30 kg/m2) who also have sleep-disordered breathing and awake diurnal hypercapnia in the absence of other causes of hypoventilation. Patients with OHS have a higher burden of medical comorbidities as compared to those with obstructive sleep apnea (OSA). This places patients with OHS at higher risk for adverse postoperative events. Obese patients and those with OSA undergoing elective noncardiac surgery are not routinely screened for OHS. Screening for OHS would require additional preoperative evaluation of morbidly obese patients with severe OSA and suspicion of hypoventilation or resting hypoxemia. Cautious selection of the type of anesthesia, use of apneic oxygenation with high-flow nasal cannula during laryngoscopy, better monitoring in the postanesthesia care unit (PACU) can help minimize adverse perioperative events. Among other risk-reduction strategies are proper patient positioning, especially during intubation and extubation, multimodal analgesia, and cautious use of postoperative supplemental oxygen.

Sudden death after oxygen toxicity seizure during hyperbaric oxygen treatment: Case report

Acute cerebral oxygen toxicity (ACOT) is a known side effect of hyperbaric oxygen treatment (HBOT), which can cause generalised seizures. Fortunately, it has a low incidence and is rarely harmful. Nevertheless, we present a case of a 37 year-old patient with morbid obesity who died unexpectedly after an oxygen toxicity seizure in the hyperbaric chamber. Considering possible causes, physiologic changes in obesity and obesity hypoventilation syndrome may increase the risk of ACOT. Obesity, especially in extreme cases, may hinder emergency procedures, both in- and outside of a hyperbaric chamber. Physicians in the hyperbaric field should be aware of the possibility of a fatal outcome after ACOT through the described mechanisms and take appropriate preventative measures. Basic airway management skills are strongly advised for involved physicians, especially when specialised personnel and equipment are not immediately available.

Effectiveness of different treatments in obesity hypoventilation syndrome

Obesity hypoventilation syndrome (OHS) is an undesirable consequence of obesity, defined as daytime hypoventilation, sleep disorder breathing and obesity; during the past few years the prevalence of extreme obesity has markedly increased worldwide consequently increasing the prevalence of OHS. Patients with OHS have a lower quality of life and a higher risk of unfavourable cardiometabolic consequences. Early diagnosis and effective treatment can lead to significant improvement in patient outcomes; therefore, such data has noticeably raised interest in the management and treatment of this sleep disorder. This paper will discuss the findings on the main current treatment modalities OHS will be discussed.

The effect of 50% oxygen on PtCO2 in patients with stable COPD, bronchiectasis, and neuromuscular disease or kyphoscoliosis: randomised cross-over trials

BACKGROUND

High-concentration oxygen therapy causes increased arterial partial pressure of carbon dioxide (PaCO2) in patients with COPD, asthma, pneumonia, obesity and acute lung injury. The objective of these studies was to investigate whether this physiological response to oxygen therapy occurs in stable patients with neuromuscular disease or kyphoscoliosis, and bronchiectasis.

METHODS

Three randomised cross-over trials recruited stable patients with neuromuscular disease or kyphoscoliosis (n = 20), bronchiectasis (n = 24), and COPD (n = 24). Participants were randomised to receive 50% oxygen and 21% oxygen (air), each for 30 min, in randomly assigned order. The primary outcome was transcutaneous partial pressure of carbon dioxide (PtCO2) at 30 min. The primary analysis was a mixed linear model.

RESULTS

Sixty six of the 68 participants had baseline PtCO2 values < 45 mmHg. The intervention baseline adjusted PtCO2 difference (95% CI) between oxygen and room air after 30 min was 0.2 mmHg (- 0.4 to 0.9), P = 0.40; 0.5 mmHg (- 0.2 to 1.2), P = 0.18; and 1.3 mmHg (0.7 to 1.8), P < 0.001, in the neuromuscular/kyphoscoliosis, bronchiectasis and COPD participants respectively.

CONCLUSIONS

The small increase in PtCO2 in the stable COPD patients with high-concentration oxygen therapy contrasts with the marked increases in PaCO2 seen in the setting of acute exacerbations of COPD. This suggests that the model of studying the effects of high-concentration oxygen therapy in patients with stable respiratory disease is not generalisable to the use of oxygen therapy in the acute clinical setting. Appropriate studies of high-concentration compared to titrated oxygen in acute clinical settings are needed to determine if there is a risk of oxygen-induced hypercapnia in patients with neuromuscular disease, kyphoscoliosis or bronchiectasis.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12615000970549 Registered 16/9/15, ACTRN12615000971538 Registered 16/9/15 and ACTRN12615001056583 Registered 7/10/15.

Benefits and harms of increased inspiratory oxygen concentrations

PURPOSE OF REVIEW

The topic of perioperative hyperoxia remains controversial, with valid arguments on both the 'pro' and 'con' side. On the 'pro' side, the prevention of surgical site infections was a strong argument, leading to the recommendation of the use of hyperoxia in the guidelines of the Center for Disease Control and the WHO. On the 'con' side, the pathophysiology of hyperoxia has increasingly been acknowledged, in particular the pulmonary side effects and aggravation of ischaemia/reperfusion injuries.

RECENT FINDINGS

Some 'pro' articles leading to the Center for Disease Control and WHO guidelines advocating perioperative hyperoxia have been retracted, and the recommendations were downgraded from 'strong' to 'conditional'. At the same time, evidence that supports a tailored, more restrictive use of oxygen, for example, in patients with myocardial infarction or following cardiac arrest, is accumulating.

SUMMARY

The change in recommendation exemplifies that despite much work performed on the field of hyperoxia recently, evidence on either side of the argument remains weak. Outcome-based research is needed for reaching a definite recommendation.

Evaluation of hyperoxia-induced hypercapnia in obese patients after cardiac surgery: a randomized crossover comparison of conservative and liberal oxygen administration

PURPOSE

Recent studies on patients with stable obesity-hypoventilation syndrome have raised concerns about hyperoxia-induced hypercapnia in this population. This study aimed to evaluate whether a higher oxygen saturation target would increase arterial partial pressure of carbon dioxide (PaCO2) in obese patients after coronary artery bypass grafting surgery (CABG).

METHODS

Obese patients having CABG were recruited. With a randomized crossover design, we compared two oxygenation strategies for 30 min each, immediately after extubation: a peripheral oxygen saturation (SpO2) target of ≥ 95% achieved with manual oxygen titration (liberal) and a SpO2 target of 90% achieved with FreeO2, an automated oxygen titration device (conservative). The main outcome was end-of-period arterial PaCO2.

RESULTS

Thirty patients were included. Mean (standard deviation [SD]) body mass index (BMI) was 34 (3) kg·m-2 and mean (SD) baseline partial pressure of carbon dioxide (PCO2) was 40.7 (3.1) mmHg. Mean (SD) end-of-period PaCO2 was 42.0 (5.4) mmHg in the conservative period, compared with 42.6 (4.6) mmHg in the liberal period [mean difference - 0.6 (95% confidence interval - 2.2 to 0.9) mmHg; P = 0.4]. Adjusted analysis for age, BMI, narcotics, and preoperative PaCO2 did not substantively change the results. Fourteen patients were retainers, showing an elevation in mean (SD) PaCO2 in the liberal period of 3.3 (4.1) mmHg. Eleven patients had the opposite response, with a mean (SD) end-of-period PaCO2 decrease of 1.8 (2.2) mmHg in the liberal period. Five patients had a neutral response.

CONCLUSION

This study did not show a clinically important increase in PaCO2 associated with higher SpO2 values in this specific population of obese patients after CABG. Partial pressure of carbon dioxide increased with liberal oxygen administration in almost half of the patients, but no predictive factor was identified.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT02917668); registered 25 September, 2016.

Non-invasive ventilation for obese patients with chronic respiratory failure: Are two pressures always better than one?

Obesity-related respiratory failure is increasingly common but remains under-diagnosed and under-treated. There are several clinical phenotypes reported, including severe obstructive sleep apnoea (OSA), isolated nocturnal hypoventilation with or without severe OSA and OSA complicating chronic obstructive pulmonary disease (COPD). The presence of hypercapnic respiratory failure is associated with poor clinical outcomes in each of these groups. While weight loss is a core aim of management, this is often unachievable, and treatment of sleep-disordered breathing with positive airway pressure (PAP) therapy is the mainstay of clinical practice. Although there are few long-term clinical efficacy trials, the lack of equipoise would prevent the utilization of an untreated control group. The current data support the use of PAP therapy to improve respiratory failure and is associated with improvements in health-related quality of life, reduced healthcare utilization and reduced mortality. Both continuous PAP (CPAP) and non-invasive ventilation (NIV) appear safe and effective in patients with obesity-related respiratory failure and OSA, with or without COPD, and the current evidence would not support a single therapy choice in all patients. There are no studies of CPAP in patients with isolated nocturnal hypoventilation, and NIV would be the current recommendation in this patient group. Whichever starting therapy is used, titration should be performed to correct sleep-disordered breathing and reverse chronic respiratory failure, with consideration of step-down of the treatment based on a clinical re-evaluation. In contrast, failure to reach physiological and clinical treatment targets should lead to the consideration of treatment escalation.

Obesity hypoventilation syndrome

Obesity hypoventilation syndrome (OHS) is defined as a combination of obesity (body mass index ≥30 kg·m-2), daytime hypercapnia (arterial carbon dioxide tension ≥45 mmHg) and sleep disordered breathing, after ruling out other disorders that may cause alveolar hypoventilation. OHS prevalence has been estimated to be ∼0.4% of the adult population. OHS is typically diagnosed during an episode of acute-on-chronic hypercapnic respiratory failure or when symptoms lead to pulmonary or sleep consultation in stable conditions. The diagnosis is firmly established after arterial blood gases and a sleep study. The presence of daytime hypercapnia is explained by several co-existing mechanisms such as obesity-related changes in the respiratory system, alterations in respiratory drive and breathing abnormalities during sleep. The most frequent comorbidities are metabolic and cardiovascular, mainly heart failure, coronary disease and pulmonary hypertension. Both continuous positive airway pressure (CPAP) and noninvasive ventilation (NIV) improve clinical symptoms, quality of life, gas exchange, and sleep disordered breathing. CPAP is considered the first-line treatment modality for OHS phenotype with concomitant severe obstructive sleep apnoea, whereas NIV is preferred in the minority of OHS patients with hypoventilation during sleep with no or milder forms of obstructive sleep apnoea (approximately <30% of OHS patients). Acute-on-chronic hypercapnic respiratory failure is habitually treated with NIV. Appropriate management of comorbidities including medications and rehabilitation programmes are key issues for improving prognosis.

Obesity hypoventilation syndrome: a current review

Obesity hypoventilation syndrome (OHS) is defined as the presence of obesity (body mass index ≥ 30 kg/m²) and daytime arterial hypercapnia (PaCO2 ≥ 45 mmHg) in the absence of other causes of hypoventilation. OHS is often overlooked and confused with other conditions associated with hypoventilation, particularly COPD. The recognition of OHS is important because of its high prevalence and the fact that, if left untreated, it is associated with high morbidity and mortality. In the present review, we address recent advances in the pathophysiology and management of OHS, the usefulness of determination of venous bicarbonate in screening for OHS, and diagnostic criteria for OHS that eliminate the need for polysomnography. In addition, we review advances in the treatment of OHS, including behavioral measures, and recent studies comparing the efficacy of continuous positive airway pressure with that of noninvasive ventilation.

Automated Oxygen Delivery in Hospitalized Patients with Acute Respiratory Failure: A Pilot Study

Background and Objectives

Despite its' proven benefits, oxygen therapy may be complicated with potential adverse events such as hypoxemia or hyperoxia-driven hypercapnia. Automated oxygen delivery systems may aid in avoiding these complications. The scope of the present study is to test the efficacy and safety of a new automated oxygen delivery device.

Methods

This study included 23 patients with acute respiratory failure (ARF) hospitalized in the Respiratory Medicine Department of the University Hospital of Larissa. Both patients with purely hypoxemic or hypercapnic ARF were included. Automated oxygen administration was performed with Digital Oxygen Therapy, a new closed-loop system designed to automatically adjust oxygen flow according to target oxygen saturation (SpO₂) of 88-92% for hypercapnic patients and 92-96% for purely hypoxemic patients with ARF. The device was applied for 4 hours. Arterial blood gas analysis was performed at 1 hour and 3 hours following the device application.

Results

Mean age was 72.91 ± 13.91 years. Twelve patients were male, and 11 were female. The majority of patients suffered from hypercapnic respiratory failure (n=13, 56.5%). At 1 hour and 3 hours, SpO₂ and PaO₂ displayed excellent correlation (p < 0.001, r = 0.943, and p < 0.001, r = 0.954, respectively). We did not observe any adverse events associated with the device.

Conclusions

Our results indicate that automated oxygen treatment is feasible and safe in hospitalized patients with acute respiratory failure. Further studies are required in order to assess the long-term effects of automated oxygen delivery systems.

Effect of Supplemental Oxygen on Blood Pressure in Obstructive Sleep Apnea (SOX). A Randomized Continuous Positive Airway Pressure Withdrawal Trial

RATIONALE

Obstructive sleep apnea (OSA) is associated with systemic hypertension. Either overnight intermittent hypoxia, or the recurrent arousals that occur in OSA, could cause the daytime increases in blood pressure (BP).

OBJECTIVES

To establish the role of intermittent hypoxia in the increased morning BP in patients with OSA.

METHODS

Randomized, double-blinded, crossover trial assessing the effects of overnight supplemental oxygen versus air (sham) on morning BP, after continuous positive airway pressure (CPAP) withdrawal in patients with moderate to severe OSA. The primary outcome was the change in home morning BP after CPAP withdrawal for 14 nights, oxygen versus air. Secondary outcomes included oxygen desaturation index (ODI), apnea-hypopnea index (AHI), subjective sleepiness (Epworth Sleepiness Scale score), and objective sleepiness (Oxford Sleep Resistance Test).

MEASUREMENTS AND MAIN RESULTS

Supplemental oxygen virtually abolished the BP rise after CPAP withdrawal and, compared with air, significantly reduced the rise in mean systolic BP (-6.6 mm Hg; 95% confidence interval [CI], -11.3 to -1.9; P = 0.008), mean diastolic BP (-4.6 mm Hg; 95% CI, -7.8 to -1.5; P = 0.006), and median ODI (-23.8/h; interquartile range, -31.0 to -16.3; P < 0.001) after CPAP withdrawal. There was no significant difference, oxygen versus air, in AHI, subjective sleepiness, or objective sleepiness.

CONCLUSIONS

Supplemental oxygen virtually abolished the rise in morning BP during CPAP withdrawal. Supplemental oxygen substantially reduced intermittent hypoxia, but had a minimal effect on markers of arousal (including AHI), subjective sleepiness, or objective sleepiness. Therefore intermittent hypoxia, and not recurrent arousals, appears to be the dominant cause of daytime increases in BP in OSA.

The obese patient undergoing nonbariatric surgery

PURPOSE OF REVIEW

This article provides the reader with recent findings on the pathophysiology of comorbidities in the obese, as well as evidence-based treatment options to deal with perioperative respiratory challenges.

RECENT FINDINGS

Our understanding of obesity-associated asthma, obstructive sleep apnea, and obesity hypoventilation syndrome is still expanding. Routine screening for obstructive sleep apnea using the STOP-Bang score might identify high-risk patients that benefit from perioperative continuous positive airway pressure and close postoperative monitoring. Measures to most effectively support respiratory function during induction of and emergence from anesthesia include optimal patient positioning and use of noninvasive positive pressure ventilation. Appropriate mechanical ventilation settings are under investigation, so that only the use of protective low tidal volumes could be currently recommended. A multimodal approach consisting of adjuvants, as well as regional anesthesia/analgesia techniques reduces the need for systemic opioids and related respiratory complications.

SUMMARY

Anesthesia of obese patients for nonbariatric surgical procedures requires knowledge of typical comorbidities and their respective treatment options. Apart from cardiovascular diseases associated with the metabolic syndrome, awareness of any pulmonary dysfunction is of paramount. A multimodal analgesia approach may be useful to reduce postoperative pulmonary complications.

Prevention and care of respiratory failure in obese patients

With the increase in the global prevalence of obesity, there is a parallel rise in the proportion of obese patients admitted to intensive care units, referred for major surgery or requiring long-term non-invasive ventilation (NIV) at home for chronic respiratory failure. We describe the physiological effect of obesity on the respiratory system mainly in terms of respiratory mechanics, respiratory drive, and patency of the upper airways. Particular attention is given to the prevention and the clinical management of respiratory failure in obese patients with a main focus on invasive and NIV in intensive care during the perioperative period and long-term use of NIV on return home. We also address other aspects of care of obese patients, including antibiotic dosing and catheter-related infections.

High flow or titrated oxygen for obese medical inpatients: a randomised crossover trial

OBJECTIVE

To compare the effects on transcutaneous carbon dioxide tension (Ptco2) of high concentration and titrated oxygen therapy in medical inpatients with morbid obesity who were not selected for a pre-existing diagnosis of obesity hypoventilation syndrome.

DESIGN

A randomised, crossover trial undertaken between February and September 2015.

SETTING

Internal medicine service, Wellington Regional Hospital, New Zealand.

PARTICIPANTS

22 adult inpatients, aged 16 years or more, with a body mass index exceeding 40 kg/m².

INTERVENTIONS

Participants received in random order two 60-minute interventions, with a minimum 30-minute washout period between treatments: titrated oxygen therapy (oxygen delivered, if required, via nasal prongs to achieve peripheral oxygen saturation [Spo2] of 88-92%), and high concentration oxygen therapy (delivered via Hudson mask at 8 L/min, without regard to Spo2). Ptco2 and Spo2 were recorded at 10-minute intervals.

MAIN OUTCOME MEASURE

Ptco2 at 60 minutes, adjusted for baseline.

RESULTS

Baseline Ptco2 was 45 mmHg or lower for 16 participants with full data (73%). The mean difference in Ptco2 between high concentration and titrated oxygen therapy at 60 minutes was 3.2 mmHg (95% CI, 1.3-5.2 mmHg; P = 0.002).

CONCLUSION

High concentration oxygen therapy increases Ptco2 in morbidly obese patients. Our findings support guidelines that advocate oxygen therapy, if required in patients with morbid obesity, be titrated to achieve a target Spo2 of 88-92%.

CLINICAL TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12610000522011.

Obesity Hypoventilation Syndrome: Choosing the Appropriate Treatment of a Heterogeneous Disorder

The obesity hypoventilation syndrome (OHS) is associated with significant morbidity and increased mortality compared with simple obesity and eucapnic obstructive sleep apnea. Accurate diagnosis and commencement of early and appropriate management is fundamental in reducing the significant personal and societal burdens this disorder poses. Sleep disordered breathing is a major contributor to the developmental of sleep and awake hypercapnia, which characterizes OHS, and is effectively addressed through the use of positive airway pressure (PAP) therapy. This article reviews the current evidence supporting different modes of PAP currently used in managing these individuals.

Mechanisms of hypoxemia

Oxygen is an essential element for life and without oxygen humans can survive for few minutes only. There should be a balance between oxygen demand and delivery in order to maintain homeostasis within the body. The two main organ systems responsible for oxygen delivery in the body and maintaining homeostasis are respiratory and cardiovascular system. Abnormal function of any of these two would lead to the development of hypoxemia and its detrimental consequences. There are various mechanisms of hypoxemia but ventilation/perfusion mismatch is the most common underlying mechanism of hypoxemia. The present review will focus on definition, various causes, mechanisms, and approach of hypoxemia in human.

The Effect of Supplemental Oxygen in Obesity Hypoventilation Syndrome

STUDY OBJECTIVES

Low flow supplemental oxygen is commonly prescribed to patients with obesity hypoventilation syndrome (OHS). However, there is a paucity of data regarding its efficacy and safety. The objective of this study was to assess the medium-term treatment efficacy of adding supplemental oxygen therapy to commonly prescribed treatment modalities in OHS.

METHODS

In this post hoc analysis of a previous randomized controlled trial, we studied 302 sequentially screened OHS patients who were randomly assigned to noninvasive ventilation, continuous positive airway pressure, or lifestyle modification. Outcomes at 2 mo included arterial blood gases, symptoms, quality of life, blood pressure, polysomnography, spirometry, 6-min walk distance, and hospital resource utilization. Statistical analysis comparing patients with and without oxygen therapy in the three treatment groups was performed using an intention-to-treat analysis.

RESULTS

In the noninvasive ventilation group, supplemental oxygen reduced systolic blood pressure although this could be also explained by a reduction in body weight experienced in this group. In the continuous positive airway pressure group, supplemental oxygen increased the frequency of morning confusion. In the lifestyle modification group, supplemental oxygen increased compensatory metabolic alkalosis and decreased the apnea-hypopnea index during sleep. Oxygen therapy was not associated with an increase in hospital resource utilization in any of the groups.

CONCLUSIONS

After 2 mo of follow-up, chronic oxygen therapy produced marginal changes that were insufficient to consider it, globally, as beneficial or deleterious. Because supplemental oxygen therapy did not increase hospital resource utilization, we recommend prescribing oxygen therapy to patients with OHS who meet criteria with close monitoring. Long-term studies examining outcomes such as incident cardiovascular morbidity and mortality are necessary.

CLINICAL TRIALS REGISTRATION

Clinicaltrial.gov, ID: NCT01405976.

Avoiding Management Errors in Patients with Obesity Hypoventilation Syndrome

The prevalence of obesity hypoventilation syndrome and obstructive sleep apnea are increasing rapidly in the United States in parallel with the obesity epidemic. As the pathogenesis of this chronic illness is better understood, effective evidence-based therapies are being deployed to reduce morbidity and mortality. Nevertheless, patients with obesity hypoventilation still fall prey to at least four avoidable types of therapeutic errors, especially at the time of hospitalization for respiratory or cardiovascular decompensation: (1) patients with obesity hypoventilation syndrome may develop acute hypercapnia in response to administration of excessive supplemental oxygen; (2) excessive diuresis for peripheral edema using a loop diuretic such as furosemide exacerbates metabolic alkalosis, thereby worsening daytime hypoventilation and hypoxemia; (3) excessive or premature pharmacological treatment of psychiatric illnesses can exacerbate sleep-disordered breathing and worsen hypercapnia, thereby exacerbating psychiatric symptoms; and (4) clinicians often erroneously diagnose obstructive lung disease in patients with obesity hypoventilation, thereby exposing them to unnecessary and potentially harmful medications, including β-agonists and corticosteroids. Just as literary descriptions of pickwickian syndrome have given way to greater understanding of the pathophysiology of obesity hypoventilation, clinicians might exercise caution to consider these potential pitfalls and thus avoid inflicting unintended and avoidable complications.

Noninvasive Ventilation in the Critically Ill Patient With Obesity Hypoventilation Syndrome: A Review

Obesity is a global epidemic that adversely affects respiratory physiology. Sleep-disordered breathing and obesity hypoventilation syndrome (OHS) are among the most common pulmonary complications related to obesity class III. Patients with OHS may present with acute hypercapnic respiratory failure (AHRF) that necessitates immediate noninvasive ventilation (NIV) or invasive ventilation and intensive care unit (ICU) monitoring. The OHS is underrecognized as a cause of AHRF. The management of mechanical ventilation in obese ICU patients is one of the most challenging problems facing respirologists, intensivists, and anesthesiologists. The treatment of AHRF in patients with OHS should aim to improve alveolar ventilation with better alveolar gas exchange, as well as maintaining a patent upper airway, which is ideally achieved through NIV. Treatment with NIV is associated with improvement in blood gases and lung mechanics and may reduce hospital admissions and morbidity. In this review, we will address 3 main issues: (1) NIV of critically ill patients with acute respiratory failure and OHS; (2) the indications for postoperative application of NIV in patients with OHS; and (3) the impact of OHS on weaning and postextubation respiratory failure. Additionally, the authors propose an algorithm for the management of obese patients with AHRF.

The clinical characteristics and hospital and post-hospital survival of patients with the obesity hypoventilation syndrome: analysis of a large cohort

OBJECTIVE

The worldwide prevalence of obesity has reached epidemic proportions. Obesity hypoventilation syndrome (OHS) is a common yet largely undiagnosed and mistreated condition that likely carries a high mortality. The aim of this study was to determine the clinical characteristics, hospital outcome, outcome following hospital discharge and predictors of death in a large cohort of patients hospitalized with OHS. OHS is an important condition as many patients with this syndrome are misdiagnosed and receive inappropriate treatment.

METHODS

We reviewed the electronic medical records of patients with unequivocal OHS admitted to a 525-bed tertiary-care teaching hospital over a 5-year period. Demographic and clinical data as well as hospital disposition were recorded. In order to determine the patients' post-discharge status, we linked our database to the database of death certificates of the State Registrar of Vital Records.

RESULTS

We identified 600 patients who met the inclusion criteria for this study. The patients' mean age was 58 ± 15 years with a mean body mass index of 48.2 ± 8.3 kg m-2; 64% were women. Thirty-seven percent had a history of diabetes and 43% had been misdiagnosed as having chronic obstructive pulmonary disease, while none had been previously diagnosed with OHS. The most common admission diagnoses were respiratory failure, heart failure and sepsis. Ninety (15%) patients died during the index hospitalization. The patients' age, S-creatinine, respiratory failure, sepsis and admission to the ICU were independent predictors of hospital mortality. The hospital survivors were followed for a mean of 1,174 ± 501 d (3.2 ± 1.3 years) from the index hospitalization. On follow-up, 98 of the 510 (19%) hospital survivors died, with an overall cumulative mortality of 31.3%. The patients' age, S-creatinine and admission to the ICU were independent predictors of post-hospital mortality.

CONCLUSION

Obesity hypoventilation syndrome is a common disease that is frequently misdiagnosed and mistreated and carries a 3-year morality, which is significantly worse than that for most cancers combined. Considering the high mortality of this disease, all patients with a body mass index > 35 kg m-2 should be screened for OHS; those patients with both early and established OHS should be referred to a pulmonary and/or sleep specialist for evaluation for non-invasive positive pressure ventilation, to a dietician for dietary counseling and lifestyle modification and to a bariatric surgeon for evaluation for bariatric surgery.

Obesity Hypoventilation Syndrome: Weighing in on Therapy Options

Obesity hypoventilation syndrome is becoming an increasingly encountered condition both in respiratory outpatient clinics and in hospitalized patients. The health consequences and social disadvantages of obesity hypoventilation syndrome are significant. Unfortunately, the diagnosis and institution of appropriate therapy is commonly delayed when the syndrome is not recognized or misdiagnosed. Positive airway pressure therapy remains the mainstay of treatment and is effective in controlling sleep-disordered breathing and improving awake blood gases in the majority of individuals. Evidence supporting one mode of therapy over another is limited. Both continuous and bilevel therapy modes can successfully improve daytime gas exchange, with adherence to therapy an important modifiable factor in the response to treatment. Despite adherence to therapy, these individuals continue to experience excess mortality primarily due to cardiovascular events compared with those with eucapnic sleep apnea using CPAP. This difference likely arises from ongoing systemic inflammation secondary to the morbidly obese state. The need for a comprehensive approach to managing nutrition, weight, and physical activity in addition to reversal of sleep-disordered breathing is now widely recognized. Future studies need to evaluate the impact of a more aggressive and comprehensive treatment plan beyond managing sleep-disordered breathing. The impact of early identification and treatment of sleep-disordered breathing on the development and reversal of cardiometabolic dysfunction also requires further attention.

Treatment of Sleep Disordered Breathing Liberates Obese Hypoxemic Patients from Oxygen

Background

Obese hypoxemic patients have a high prevalence of sleep disordered breathing (SDB). It is unclear to what extent treatment of SDB can improve daytime hypoxemia.

Methods

We performed a retrospective cohort study of obese hypoxemic individuals, all of whom underwent polysomnography, arterial blood gas analysis, and subsequent initiation of positive airway pressure (PAP) therapy for SDB. Patients were followed for one year for change in partial pressure of arterial oxygen and the need for supplemental oxygen.

Results

One hundred and seventeen patients were treated with nocturnal PAP and had follow-up available. Adherence to PAP was satisfactory in 60%, and was associated with a significant improvement in daytime hypoxemia and hypercapnea; 56% of these patients were able to discontinue supplemental oxygen. Adherence to PAP therapy and the baseline severity of OSA predicted improvement in hypoxemia, but only adherence to PAP therapy predicted liberation from supplemental oxygen.

Conclusions

The identification and treatment of SDB in obese hypoxemic patients improves daytime hypoxemia. It is important to identify SDB in these patients, since supplemental oxygen can frequently be discontinued following treatment with PAP therapy.

Obesity hypoventilation syndrome in the critically ill

This article summarizes available data on the obesity hypoventilation syndrome and its pertinence to intensivists, outlines clinical and pathophysiologic aspects of the disease, discusses multidisciplinary treatments, and reviews the available literature on outcomes specific to the critically ill patient.

Obesity Hypoventilation Syndrome

Obesity hypoventilation syndrome is a respiratory consequence of morbid obesity that is characterized by alveolar hypoventilation during sleep and wakefulness. The disorder involves a complex interaction between impaired respiratory mechanics, ventilatory drive and sleep-disordered breathing. Early diagnosis and treatment is important, because delay in treatment is associated with significant mortality and morbidity. Available treatment options include non-invasive positive airway pressure (PAP) therapies and weight loss. There is limited long-term data regarding the effectiveness of such therapies. This review outlines the current concepts of clinical presentation, diagnostic and management strategies to help identify and treat patients with obesity-hypoventilation syndromes.