Robert J. Farney

Left Ventricular Hypertrophy in Severe Obesity: Interactions Among Blood Pressure, Nocturnal Hypoxemia, and Body Mass

Obese subjects have a high prevalence of left ventricular (LV) hypertrophy. It is unclear to what extent LV hypertrophy results directly from obesity or from associated conditions, such as hypertension, impaired glucose homeostasis, or obstructive sleep apnea. We tested the hypothesis that LV hypertrophy in severe obesity is associated with additive effects from each of the major comorbidities. Echocardiography and laboratory testing were performed in 455 severely obese subjects with body mass index 35 to 92 kg/m2 and 59 nonobese reference subjects. LV hypertrophy, defined by allometrically corrected (LV mass/height2.7), gender-specific criteria, was present in 78% of the obese subjects. Multivariable regression analyses showed that average nocturnal oxygen saturation <85% was the strongest independent predictor of LV hypertrophy (P<0.001), followed by systolic blood pressure (P<0.015) and then body mass index (P<0.05). With regard to LV mass, there were synergistic effects between hypertension and body mass index (P interaction <0.001) and between hypertension and reduced nocturnal oxygen saturation. Severely obese subjects had normal LV endocardial fractional shortening (35±6% versus 35±6%) but mildly decreased midwall fractional shortening (15±2% versus 17±2%; P<0.001), indicating subtle myocardial dysfunction. In conclusion, more severe nocturnal hypoxemia, increasing systolic blood pressure, and body mass index are all independently associated with increased LV mass. The effects of increased blood pressure seem to amplify those of sleep apnea and more severe obesity.

The STOP-Bang Equivalent Model and Prediction of Severity of Obstructive Sleep Apnea: Relation to Polysomnographic Measurements of the Apnea/Hypopnea Index

BACKGROUND Various models and questionnaires have been developed for screening specific populations for obstructive sleep apnea (OSA) as defined by the apnea/hypopnea index (AHI); however, almost every method is based upon dichotomizing a population, and none function ideally. We evaluated the possibility of using the STOP-Bang model (SBM) to classify severity of OSA into 4 categories ranging from none to severe. METHODS Anthropomorphic data and the presence of snoring, tiredness/sleepiness, observed apneas, and hypertension were collected from 1426 patients who underwent diagnostic polysomnography. Questionnaire data for each patient was converted to the STOP-Bang equivalent with an ordinal rating of 0 to 8. Proportional odds logistic regression analysis was conducted to predict severity of sleep apnea based upon the AHI: none (AHI < 5/h), mild (AHI ≥ 5 to < 15/h), moderate (≥ 15 to < 30/h), and severe (AHI ≥ 30/h). RESULTS Linear, curvilinear, and weighted models (R(2) = 0.245, 0.251, and 0.269, respectively) were developed that predicted AHI severity. The linear model showed a progressive increase in the probability of severe (4.4% to 81.9%) and progressive decrease in the probability of none (52.5% to 1.1%). The probability of mild or moderate OSA initially increased from 32.9% and 10.3% respectively (SBM score 0) to 39.3% (SBM score 2) and 31.8% (SBM score 4), after which there was a progressive decrease in probabilities as more patients fell into the severe category. CONCLUSIONS The STOP-Bang model may be useful to categorize OSA severity, triage patients for diagnostic evaluation or exclude from harm.

Health outcomes of gastric bypass patients compared to nonsurgical, nonintervened severely obese

Favorable health outcomes at 2 years postbariatric surgery have been reported. With exception of the Swedish Obesity Subjects (SOS) study, these studies have been surgical case series, comparison of surgery types, or surgery patients compared to subjects enrolled in planned nonsurgical intervention. This study measured gastric bypass effectiveness when compared to two separate severely obese groups not participating in designed weight‐loss intervention. Three groups of severely obese subjects (N = 1,156, BMI ≥ 35 kg/m2) were studied: gastric bypass subjects (n = 420), subjects seeking gastric bypass but did not have surgery (n = 415), and population‐based subjects not seeking surgery (n = 321). Participants were studied at baseline and 2 years. Quantitative outcome measures as well as prevalence, incidence, and resolution rates of categorical health outcome variables were determined. All quantitative variables (BMI, blood pressure, lipids, diabetes‐related variables, resting metabolic rate (RMR), sleep apnea, and health‐related quality of life) improved significantly in the gastric bypass group compared with each comparative group (all P < 0.0001, except for diastolic blood pressure and the short form (SF‐36) health survey mental component score at P < 0.01). Diabetes, dyslipidemia, and hypertension resolved much more frequently in the gastric bypass group than in the comparative groups (all P < 0.001). In the surgical group, beneficial changes of almost all quantitative variables correlated significantly with the decrease in BMI. We conclude that Roux‐en‐Y gastric bypass surgery when compared to severely obese groups not enrolled in planned weight‐loss intervention was highly effective for weight loss, improved health‐related quality of life, and resolution of major obesity‐associated complications measured at 2 years.

Sleep disordered breathing in patients receiving therapy with buprenorphine/naloxone

Patients using chronic opioids are at risk for exceptionally complex and potentially lethal disorders of breathing during sleep, including central and obstructive apnoeas, hypopnoeas, ataxic breathing and nonapnoeic hypoxaemia. Buprenorphine, a partial &mgr;-opioid agonist with limited respiratory toxicity, is widely used for the treatment of opioid dependency and chronic nonmalignant pain. However, its potential for causing sleep disordered breathing has not been studied. 70 consecutive patients admitted for therapy with buprenorphine/naloxone were routinely evaluated with sleep medicine consultation and attended polysomnography. The majority of patients were young (mean±sd age 31.8±12.3 years), nonobese (mean±sd body mass index 24.9±5.9 kg·m−2) and female (60%). Based upon the apnoea/hypopnoea index (AHI), at least mild sleep disordered breathing (AHI ≥5 events·h−1) was present in 63% of the group. Moderate (AHI ≥15– <30 events·h−1) and severe (AHI ≥30 events·h−1) sleep apnoea was present in 16% and 17%, respectively. Hypoxaemia, defined as an arterial oxygen saturation measured by pulse oximetry, of <90% for ≥10% of sleep time, was present in 27 (38.6%) patients. Despite the putative protective ceiling effect regarding ventilatory suppression observed during wakefulness, buprenorphine may induce significant alterations of breathing during sleep at routine therapeutic doses.

Office management of common sleep-wake disorders

The prevalence of sleep disorders manifest as insomnia and fatigue of excessive daytime sleepiness in the general population; office practice is high. Poor quality sleep may pose a significant health risk for not only the patient but society in general. Sensitivity for potentially serious sleep disorders should be coupled with an organized approach to diagnosis and therapy. Differentiation of the principal complaint into insomnia versus hypersomnia and determination of duration are the key elements. Office-based management of the most common sleep-wake disorders and current diagnostic testing standards are discussed.

A decision-driven system to collect the patient history

We have developed a computer-administered history designed to directly interview hospitalized patients with pulmonary disease. A frame-based decision system is used to direct the history and to generate a one- to five-member differential diagnostic list based on this history. This system incorporates a cognitive model of question selection and a Bayesian scoring algorithm. Structures to control the choice of questions are embedded in the diagnostic frames and in a QUERY program that makes the final choice of questions. We have compared the behavior of this decision-driven approach with a history taken using a paper questionnaire. The paper-based history presents 182 questions to every patient and captured 75% of 85 pulmonary diseases in its differential lists. The decision-driven system asks 50.7 +/- 31.0 (mean +/- standard deviation) and captured 74% of 61 pulmonary diseases. Our experience suggests that the use of a computerized diagnostic knowledge base to direct the selection of pertinent questions can substantially reduce the number of questions necessary to collect a diagnostically useful patient history.

Narcolepsy: a case from India with polysomnographic findings.

Narcolepsy is a common sleep disorder with a prevalence of about 0.02%. However, it may remain largely unrecognized in the Indian population owing to the perceived low prevalence. To the best of our knowledge there is only one case of narcolepsy reported from India so far. We present a case of narcolepsy with cataplexy with classical clinical and polysomnographic findings of narcolepsy.

NREM Sleep Parasomnia Associated with Chiari I Malformation

Parasomnias are common sleep disorders in children, and most cases resolve naturally by adolescence.(1) They represent arousal disorders beginning in NREM sleep and are generally non-concerning in children. The diagnosis can usually be made by clinical assessment, and testing with polysomnography is not routinely indicated.(2) However, in certain cases with atypical features, polysomnography and more extensive neurologic evaluation are medically indicated.

Experience: Cross-Technology Radio Respiratory Monitoring Performance Study

This paper addresses the performance of systems which use commercial wireless devices to make bistatic RF channel measurements for non-contact respiration sensing. Published research has typically presented results from short controlled experiments on one system. In this paper, we deploy an extensive real-world comparative human subject study. We observe twenty patients during their overnight sleep (a total of 160 hours), during which contact sensors record ground-truth breathing data, patient position is recorded, and four different RF breathing monitoring systems simultaneously record measurements. We evaluate published methods and algorithms. We find that WiFi channel state information measurements provide the most robust respiratory rate estimates of the four RF systems tested. However, all four RF systems have periods during which RF-based breathing estimates are not reliable.

Severe Respiratory Suppression Secondary to Buprenorphine Treated with Volume Assured Pressure Support (VAPS)

The optimal therapy of chronic opioid induced sleep disordered breathing (SDB) is unclear. Supplemental oxygen may potentially prolong central apneas and increase respiratory suppression. Continuous positive airway pressure (CPAP) is generally ineffective or may even augment central apneas. Therapy with an Adaptive Servo-Ventilation (ASV) device is the most successful option for most etiologies of central apnea including opioids, but we have observed a subpopulation with OISDB that do not respond well. We evaluated a 31 year-old female by means of serial attended polysomnography who was admitted for opioid detoxification and who developed severe respiratory suppression following induction therapy with buprenorphine/naloxone. Opioid induced SDB was manifest by bradypnea, ataxic breathing, central apnea (apnea/ hypopnea index or AHI 107/hr) and hypoxemia (SpO2 74%). Supplemental oxygen corrected hypoxemia but severe central apnea and bradypnea persisted. ASV was ineffective despite high pressure settings (AHI 122/hr). Ventilation was normalized (AHI 1/ hr) and hypoxemia was corrected (SpO 2 92%) with volume assured pressure support (VAPS) without supplemental oxygen The efficacy of ASV in idiopathic central apneas or Cheyne-Stokes respiration may relate to specific pathogenic factors such as high loop gain with low apneic threshold or phase delay related to cardiac disease but with a fundamentally intact respiratory pattern generator. In patients with opioid induced SDB, the pattern generator appears dysfunctional. In these cases, VAPS in which maintenance of alveolar ventilation is the primary goal may be superior to ASV in which prevention of hyperventilation overshoot and hypocapnia are the objectives. Attended polysomnography is necessary in order to reliably validate the efficacy of therapy.