Should we routinely screen for hypercapnia in sleep apnea patients before elective noncardiac surgery?

Characteristics of Obese Patients with Acute Hypercapnia Respiratory Failure Admitted in the Department of Pneumology: An Observational Study of a North African Population

Background. Acute hypercapnic respiratory failure (AHRF) is a common life-threatening event in patients with obesity hypoventilation syndrome (OHS). Objectives. To study the clinical pattern, noninvasive ventilatory support, as well as the short- and long-term outcomes of patients with OHS admitted in a ward because of AHRF. Methods. We conducted a retrospective cohort study including all adults with OHS $\text{aged}\ge 18-\text{year}-\text{old}$ , admitted in a 90-bed-ward for AHRF. Results. A total of 44 patients were included. Fifteen (34.1%) and 29 (65.9%) patients were diagnosed with malignant OHS (mOHS) and nonmalignant OHS (non-mOHS), respectively, while 36 (81.8%) had coexisting obstructive sleep apnea hypopnea syndrome (OSAHS). Patients with mOHS had a significantly higher rate of heart failure (100% vs. 31%; $p<0.001$ ), chronic renal insufficiency (CRI) (73.3% vs. 41.4%; $p=0.04$ ), and dyslipidemia (66.7% vs. 34.5%; $p=0.04$ ) than those with non-mOHS. The mean forced vital capacity (FVC) in our patients was of $59.5\%\pm 18.5$ of the predicted value, lower than what is usually reported in stable patients with OHS. At hospital admission, more than two-thirds ( $n=34$ , 77.3%) were misdiagnosed as having asthma exacerbation ( $n=4$ , 4.9.1%), chronic obstructive pulmonary disease (COPD) exacerbation ( $n=12$ , 27.3%) and/or heart failure ( $n=29$ , 65.9%). Acute pulmonary oedema (ACPE) ( $n=16$ , 36.4%) and acute viral bronchitis ( $n=12$ , 27.3%) were the main identified causal factors, while no cause could be determined in 5 (11.4%) patients. Noninvasive positive pressure ventilation (NIPPV) using bilevel positive airway pressure (BIPAP) was very highly effective to treat AHRF, with only 2.27% of patients failing the modality. Median overall duration of ventilation was 9 hours per day (1.3–20) and was significantly longer in patients with mOHS than in those with non-mOHS (10 [6–18] vs. 8 [1.3–20], respectively; $p=0.01$ ). Forty two of the forty-three patients discharged alive were treated with BIPAP or continuous positive airway pressure (CPAP) in 26 and 16 patients, respectively. The probability of survival was 90% at 12 months, while the probability of readmission for a new episode of AHRF was 56% at 6 months and 22% at 12 months, respectively. Conclusion. AHRF in OHS patients is a life-threatening event which can be successfully and safely treated with BIPAP, with a low long-term mortality even in patients with mOHS.

Predictors of obesity hypoventilation syndrome among patients with sleep-disordered breathing in India

Introduction

No study has been done in India to evaluate obesity hypoventilation syndrome (OHS) among patients with sleep-disordered breathing (SDB). The known predictors of OHS, i.e., body mass index (BMI) >35 kg/m² and forced vital capacity (FVC) <3.5 L for men and <2.3 L for women from western countries, cannot be applied to Indian patients.

Objectives

To find out the prevalence of OHS and to determine the predictors of OHS among Indian SDB patients.

Materials and Methods

It was a retrospective observational study conducted in a tertiary care institute from September 1, 2017, to August 31, 2018. All the patients who underwent polysomnography were analyzed for the presence of OHS. Of 85 patients referred for polysomnography, 76 had SDB. Thirteen patients were excluded because of hypoventilation due to other known causes or could not perform spirometry.

Results

The prevalence of OHS among SDB after excluding the other causes of hypoventilation was 15.87% (10/63). The predictors were determined using univariate analysis between daytime partial pressure of carbon dioxide (PaCO₂) and other predictors. PaCO₂ significantly correlated with minimum nocturnal oxygen saturation by pulse oximetry (SpO₂), FVC %predicted, BMI, daytime SpO₂, forced expiratory volume %predicted, and partial pressure of oxygen (PaO₂). Following a stepwise multiple regression, minimum nocturnal SpO₂, FVC %predicted, and BMI were found to be independent predictors of OHS. A minimum nocturnal SpO₂ threshold of 60%, FVC %predicted <74.5%, BMI >30.95 kg/m², and absolute FVC <2.33 L for men and <1.68 L for women were found to be predictors of OHS.

Conclusion

The prevalence of OHS in Indian patients is similar to Caucasians. OHS is seen in Indian patients even at a lower BMI and lower spirometric parameters.

Efficacy of bilevel ventilatory support in the treatment of stable patients with obesity hypoventilation syndrome: systematic review and meta-analysis

OBJECTIVE

To systematically review the effects of bilevel ventilatory support (BVS) in patients with Obesity Hypoventilation Syndrome (OHS).

METHODS

A search of databases (MEDLINE accessed by PubMed, Cochrane CENTRAL, EMBASE and LILACS) was conducted from inception to June 2018. Randomized trials comparing BVS to other therapeutic modalities such as lifestyle counseling, continuous positive airway pressure (PAP) or BVS with average volume assured pressure support for the treatment of patients with OHS were included. The primary outcome was a change in daytime arterial carbon dioxide levels (PaCO₂). Secondary outcome measures included arterial partial pressure of oxygen (PaO₂), blood bicarbonate (HCO₃), percentage of total sleep time (TST) with oxygen saturation <90%, transcutaneous pressure of carbon dioxide (PtcCO₂), Epworth Sleepiness Scale (ESS), Medical Outcome Survey Short Form (SF36), Functional Outcomes of Sleep Questionnaire (FOSQ), Severe Respiratory Insufficiency Questionnaire (SRI), compliance with treatment, and weight loss.

RESULTS

Of 176 articles identified, seven studies were included. When BVS was compared to lifestyle counseling, the intervention was superior in improving PaCO₂ (-2.90 mmHg; 95%CI -4.28 to -1.52), PaO₂ (2.89 mmHg; 95%CI 0.33 to 5.46), HCO₃ (-2.55 mmol/L; 95%CI -3.28 to -1.81), percentage of TST<90% (-30.55%; 95%CI -37.98 to -23.12), ESS (-2.52; 95%CI -4.16 to -0.88) and FOSQ (6.33; 95%CI 1.78 to 10.88). However, when BVS was compared to other PAP modalities, there was no difference in any of the outcomes evaluated.

CONCLUSIONS

Treatment using BVS therapy is superior to lifestyle counseling. Different PAP modalities appear to be equally effective in improving outcomes. CRD42017065326.

The relationship between obstructive sleep apnea and obesity hypoventilation syndrome: a systematic review and meta-analysis

Obstructive Sleep Apnea and Obesity Hypoventilation Syndrome are two similar diseases. Obstructive Sleep Apnea has been receiving more and more attention while the diagnostic rate of Obesity Hypoventilation Syndrome is not high. Few studies directly evaluated the relationship between them. We systematically analyzed the relevance of the two diseases. MEDLINE^®, EMBASE^® and the Cochrane Library were carried out to find studies until May 2017. Pooled mean difference and 95% confidence interval were calculated to evaluate the value of clinical and physiologic variables in the prediction of Obesity Hypoventilation Syndrome. 9 Studies (n = 2085) fulfilled the predefined selection criteria. Totally 575 patients (28%) with Obesity Hypoventilation Syndrome were diagnosed from 2085 Obstructive Sleep Apnea patients. Among clearly diagnosed Obstructive Sleep Apnea patients, higher Body Mass Index levels(mean difference:4.72 kg/m²; 95% confidence interval: 4.26 to 5.17; p < 0.00001), higher Apnea-Hypopnea Index (mean difference: 8.36; 95% confidence interval: −3.88 to −2.84; p < 0.00001), greater neck circumference (mean difference:1.01; 95% confidence interval: 0.10 to 1.92; p = 0.03) and lower percent predicted FEV1 (mean difference:−10.28; 95% confidence interval:−11.33 to −9.22; p < 0.00001)were associated with the occurrence with obesity hypoventilation syndrome. We should be highly skeptical of obesity hypoventilation syndrome in Obstructive Sleep Apnea patients with these factors as early identification and appropriate treatment can improve prognosis.

Nutrition and Exercise Rehabilitation in Obesity hypoventilation syndrome (NERO): a pilot randomised controlled trial

Background

Respiratory management of obesity hypoventilation syndrome (OHS) focusses on the control of sleep-disordered breathing rather than the treatment of obesity. Currently, there are no data from randomised trials of weight loss targeted rehabilitation programmes for patients with OHS.

Intervention

A 3-month multimodal hybrid inpatient–outpatient motivation, exercise and nutrition rehabilitation programme, in addition to non invasive ventilation (NIV), would result in greater per cent weight loss compared with standard care.

Methods

A single-centre pilot randomised controlled trial allocated patients to either standard care or standard care plus rehabilitation. Primary outcome was per cent weight loss at 12 months with secondary exploratory outcomes of weight loss, exercise capacity and health-related quality of life (HRQOL) at the end of the rehabilitation programme to assess the intervention effect.

Results

Thirty-seven patients (11 male, 59.8±12.7 years) with a body mass index of 51.1±7.7 kg/m2 were randomised. At 12 months, there was no between-group difference in per cent weight loss (mean difference −5.9% (95% CI −14.4% to 2.7%; p=0.17)). At 3 months, there was a greater per cent weight loss (mean difference −5% (95% CI −8.3% to −1.4%; p=0.007)), increased exercise capacity (6 min walk test 60 m (95% CI 29.5 to 214.5) vs 20 m (95% CI 11.5 to 81.3); p=0.036) and HRQL (mean difference SF-36 general health score (10 (95% CI 5 to 21.3) vs 0 (95% CI −5 to 10); p=0.02)) in the rehabilitation group.

Conclusion

In patients with OHS, a 3-month comprehensive rehabilitation programme, in addition to NIV, resulted in improved weight loss, exercise capacity and QOL at the end of the rehabilitation period, but these effects were not demonstrated at 12 months, in part, due to the limited retention of patients at 12 months.

Trial registration number

Pre-results; NCT01483716.

Morbidity and mortality associated with obesity

Obesity and its repercussions constitute an important source of morbidity, impaired quality of life and its complications can have a major bearing on life expectancy. The present article summarizes the most important co-morbidities of obesity and their prevalence. Furthermore, it describes classification and grading systems that can be used to assess the individual and combined impact of co-morbid conditions on mortality risk. The literature was screened for assessment tools that can be deployed in the quantification of morbidity and mortality risk in individual patients. Thirteen specific domains have been identified that account for morbidity and mortality in obesity. Cardiovascular disease (CVD) and cancer account for the greatest mortality risk associated with obesity. The King's Criteria and Edmonton Obesity Staging System (EOSS) were identified as useful tools for the detection and monitoring of individual patient mortality risk in obesity care. The stark facts on the complications of obesity should be capitalized on to improve patient management and knowledge and referred to in the wider dissemination of public health messages aimed at improving primary prevention.

The role of compact polysomnography/polygraphy in sleep breathing disorder patients' management

While managing obstructive sleep apnea (OSA) or suspicious OSA patients, the otorhinolaryngologist frequently has to deal with patients undergoing repeated polysomnography (PSG) or portable monitoring (PM) and, on the other hand, should be confident about the quality and consistency of the polysomnographic diagnosis. The main polysomnographic traces compressed in a unique epoch, defined as compact PSG/PM (CP), which should be reported in all PSG/PM report, could represent an efficient tool to confirm the quality of PSG/PM diagnosis and to recognize the sleep breathing disorders (SBD): OSA, no-OSA SBD and overlap of OSA with no-OSA SBD. In this study, a synthetic and clear guided iconography and an easy decision-making algorithm based on desaturation patterns (phasic, prolonged and overlap desaturation patterns) identifiable on the CP are suggested for a quick check of the quality of PSG/PM diagnosis and to achieve an improvement in the patient's clinical management.

Drugs influencing acid base balance and bicarbonate concentration readings

Serum bicarbonate dosage is sensitive to pharmacological interferences. However, elevated bicarbonate concentration reflects chronic hypoventilation and has been proposed as a simple marker for screening patients with Obesity Hypoventilation Syndrome (OHS), a currently underdiagnosed multimorbid and high mortality disease. We provide a practical overview of the different drugs acting on the acid-base equilibrium to aid clinicians to interpret bicarbonate concentration readings. Little is known about the chronic impact of the usual doses of these drugs on serum bicarbonate concentration and further studies are needed. It is essential to take into account drugs that could interfere with this parameter to avoid misinterpretation of serum bicarbonate levels.

Obesity hypoventilation syndrome in Japan and independent determinants of arterial carbon dioxide levels

BACKGROUND AND OBJECTIVE

Obesity hypoventilation syndrome (OHS) prevalence was previously estimated at 9% in patients with obstructive sleep apnoea (OSA) in Japan. However, the definition of OSA in that study was based on an apnoea-hypopnoea index (AHI) of ≥ 20/h rather than ≥ 5/h. Therefore, the prevalence of OHS in OSA was not measured in the same way as for Western countries. Our study objectives were to investigate the characteristics of Japanese patients with OHS.

METHODS

Nine hundred eighty-one consecutive patients investigated for suspected OSA were enrolled. At least 90% of them were from urban areas, including 162 with obese OSA (body mass index (BMI) ≥ 30 kg/m(2) and AHI ≥ 5/h).

RESULTS

The prevalence of OHS (BMI 36.7 ± 4.9 kg/m(2) ) in OSA and that in obese OSA were 2.3% and 12.3%, respectively. Multiple regression analysis revealed that independent of age and BMI, arterial oxygen pressure (contribution rate (R(2) ) = 7.7%), 4% oxygen desaturation index (R(2)  = 8.9%), carbon monoxide diffusing capacity/alveolar volume (R(2)  = 8.3%), haemoglobin concentration (R(2)  = 4.9%) and waist circumference (R(2)  = 4.9%) were independently associated with arterial carbon dioxide pressure. After 12.3 ± 4.6 months of CPAP treatment, more than 60% of OHS patients no longer had hypercapnia.

CONCLUSIONS

The prevalence of OHS in OSA in Japan was 2.3%. The mean BMI of patients with OHS in Japan was lower than that in Western countries (36.7 kg/m(2) vs 44.0 kg/m(2) ).

Diagnostic predictors of obesity-hypoventilation syndrome in patients suspected of having sleep disordered breathing

INTRODUCTION

Obesity-hypoventilation syndrome (OHS) is associated with significant morbidity and mortality and requires measurement of arterial pCO2 for diagnosis.

OBJECTIVE

To determine diagnostic predictors of OHS among obese patients with suspected obstructive sleep apnea/hypopnea syndrome (OSAHS).

METHODS

Retrospective analysis of data on 525 sleep clinic patients (mean age 51.4 ± 12.7 years; 65.7% males; mean BMI 34.5 ± 8.1). All patients had sleep studies, and arterialized capillary blood gases (CBG) were measured in obese subjects (BMI > 30 kg/m2).

RESULTS

Of 525 patients, 65.5% were obese, 37.2% were morbidly obese (BMI > 40 kg/m2); 52.3% had confirmed OSAHS. Hypercapnia (pCO2 > 6 kPa or 45 mm Hg) was present in 20.6% obese and 22.1% OSAHS patients. Analysis of OHS predictors showed significant correlations between pCO2 and BMI, FEV1, FVC, AHI, mean and minimum nocturnal SpO2, sleep time with SpO2 < 90%, pO2, and calculated HCO3 from the CBG. PO2 and HCO3 were independent predictors of OHS, explaining 27.7% of pCO2 variance (p < 0.0001). A calculated HCO3 cutoff > 27 mmol/L had 85.7% sensitivity and 89.5% specificity for diagnosis of OHS, with 68.1% positive and 95.9% negative predictive value.

CONCLUSION

We confirmed a high prevalence of OHS in obese OSAHS patients (22.1%) and high calculated HCO3 level (> 27 mmol/L) to be a sensitive and specific predictor for the diagnosis of OHS.

Respiratory mechanics and ventilatory control in overlap syndrome and obesity hypoventilation

The overlap syndrome of obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD), in addition to obesity hypoventilation syndrome, represents growing health concerns, owing to the worldwide COPD and obesity epidemics and related co-morbidities. These disorders constitute the end points of a spectrum with distinct yet interrelated mechanisms that lead to a considerable health burden. The coexistence OSA and COPD seems to occur by chance, but the combination can contribute to worsened symptoms and oxygen desaturation at night, leading to disrupted sleep architecture and decreased sleep quality. Alveolar hypoventilation, ventilation-perfusion mismatch and intermittent hypercapnic events resulting from apneas and hypopneas contribute to the final clinical picture, which is quite different from the “usual” COPD. Obesity hypoventilation has emerged as a relatively common cause of chronic hypercapnic respiratory failure. Its pathophysiology results from complex interactions, among which are respiratory mechanics, ventilatory control, sleep-disordered breathing and neurohormonal disturbances, such as leptin resistance, each of which contributes to varying degrees in individual patients to the development of obesity hypoventilation. This respiratory embarrassment takes place when compensatory mechanisms like increased drive cannot be maintained or become overwhelmed.

Although a unifying concept for the pathogenesis of both disorders is lacking, it seems that these patients are in a vicious cycle. This review outlines the major pathophysiological mechanisms believed to contribute to the development of these specific clinical entities. Knowledge of shared mechanisms in the overlap syndrome and obesity hypoventilation may help to identify these patients and guide therapy.

Obesity hypoventilation syndrome: mechanisms and management

Obesity hypoventilation syndrome describes the association between obesity and the development of chronic daytime alveolar hypoventilation. This syndrome arises from a complex interaction between sleep-disordered breathing, diminished respiratory drive, and obesity-related respiratory impairment, and is associated with significant morbidity and mortality. Therapy directed toward reversing these abnormalities leads to improved daytime breathing, with available treatment options including positive pressure therapy, weight loss, and pharmacological management. However, a lack of large-scale, well-designed studies evaluating these various therapies has limited the development of evidence-based treatment recommendations. Although treatment directed toward improving sleep-disordered breathing is usually effective, not all patients tolerate mask ventilation and awake hypercapnia may persist despite effective use. In the longer term, weight loss is desirable, but data on the success and sustainability of this approach in obesity hypoventilation are lacking. The review outlines the major mechanisms believed to underlie the development of hypoventilation in this subgroup of obese patients, their clinical presentation, and current therapy options.