eMedicine Specialties > Pediatrics: General Medicine > Pulmonology

Obesity-Hypoventilation Syndrome and Pulmonary Consequences of Obesity

Author: Mary E Cataletto, MD, Associate Director, Division of Pediatric Pulmonology, Winthrop University Hospital; Professor of Clinical Pediatrics, State University of New York at Stony Brook; Director of Children's Sleep Services, Winthrop University Hospital
Coauthor(s): Gila Hertz, PhD, ABSM, Director, Center for Insomnia and Sleep Disorders, Clinical Associate Professor of Psychiatry and Behavioral Sciences, State University of New York at Stony Brook
Contributor Information and Disclosures

Updated: Nov 25, 2008

Introduction

Background

Obesity in children is a complex disorder. Its prevalence has increased so significantly in recent years that many consider it a major health concern of the developed world. In the United States alone, 33.6% of children aged 2-19 years were at risk of being overweight (defined as an age-specific and gender-specific body mass index [BMI] in the 85th-94th percentile for age) and 17.1% of children aged 2-19 years were overweight (defined as age-specific and gender-specific BMI ³ 95th percentile for age).¹

The National Health and Nutrition Examination Survey (NHANES) indicates that the prevalence of obesity is increasing in all pediatric age groups, in both genders, and in various ethnic and racial groups. Many factors, including genetics, environment, metabolism, lifestyle, and eating habits, are believed to play a role in the development of obesity. However, more than 90% of cases are idiopathic; less than 10% are associated with hormonal or genetic causes. Obesity-hypoventilation syndrome is a relatively uncommon finding in children who are obese, with an estimated frequency of 1-3%. Stated from a different point of view, 10% of patients with obstructive sleep apnea are obese.

No firm diagnostic criteria to define obesity-hypoventilation syndrome are recognized; this fact, along with limited pediatric studies and discrepant definitions of obesity and abnormal pediatric polysomnographic findings, make the diagnosis somewhat difficult. However, obesity, sleep-disordered breathing, and hypercarbia during wakefulness are features generally described with obesity-hypoventilation syndrome. Other features include excessive daytime sleepiness, hyperactivity, poor school performance with difficulty attending to tasks and impaired memory, hypoxia, and signs of cor pulmonale.

In adult patients, male sex and obesity are common risk factors for obstructive sleep apnea. Apnea, loud disruptive snoring, and daytime sleepiness are frequent presenting complaints. However, in children, neither these risk factors nor the symptom profile is as predictive for obstructive sleep apnea, except in children who are obese. In fact, 27% of children with obstructive sleep apnea have failure to thrive. In one study, daytime sleepiness occurred with the same overall frequency as in control subjects; in another study, daytime sleepiness was found to be more frequent in obese children with obstructive sleep apnea. Mental retardation has also been associated with obesity-hypoventilation syndrome.

Pathophysiology

The exact mechanism for development of obesity-hypoventilation syndrome is unknown; however, it is believed to be primarily related to abnormalities in ventilatory drive and response to hypoxia and hypercarbia, rather than the mechanical factors related to excessive body weight. Other authors feel that body weight and, more importantly, the distribution of body fat, hormones, and upper airway size and dynamics play important roles.

Additionally, animal studies are addressing circulating plasma leptin levels and their effect on expression of several hypothalamic neuropeptides. Leptin is also involved in respiratory control. Leptin deficient mice (ob/ob) have been found to have hypoventilation, obesity, and an impairment in hypercapnic ventilatory response in both wakefulness and sleep, suggesting that leptin may play a central role in obesity-hypoventilation syndrome.

Associated upper airway obstruction is important in the occurrence of obstructive sleep apnea (OSA) and hypoventilation or hypopnea (OSA/H) because OSA/H is observed more frequently when the 2 conditions occur together, compared with the simultaneous presentation of OSA/H and simple obesity. Other factors that may play a role in the development of airway obstruction during sleep include rapid eye movement (REM) atonia, increased soft tissue and fatty infiltration around the neck, decreased chest wall compliance, and decreased lung volumes (especially in the supine position) secondary to the upward displacement of the diaphragm caused by increased abdominal fat. In children, tonsillar hypertrophy added to obesity appears to be more predictive of abnormal polysomnographic findings.

Frequency

United States

The prevalence of obesity continues to rise in the pediatric age groups, in both genders, without regard for ethnicity or race. The prevalence in minority communities is a rising concern.

International

International data reporting varies, and accuracy may be less than optimal; however, Eneli and Dele Davies (2008) report that in 77% of the countries analyzed, the prevalence rate for children who were overweight was at least 10%.² Notably, the highest rates for children at risk for obesity were found in Malta (25.4%) and the United States (25.1%). Lithuania and Latvia had the lowest rates (5.1% and 5.9%, respectively).

Mortality/Morbidity

Higher rates of morbidity and mortality are associated with childhood obesity. Childhood and, especially, adolescent obesity is predictive of adult obesity, which is associated with an increased incidence of diabetes, hypertension, gallstones, and hypercholesterolemia. Pulmonary consequences observed in children and adolescents include an increased frequency of reactive airways, poor exercise tolerance, increased work of breathing, and increased oxygen consumption. The few people who develop obesity-hypoventilation syndrome experience right-sided heart failure with right ventricular hypertrophy.

Race

Race and ethnicity are associated with increased rates of obesity in children and adolescents. Puerto Rican, Cuban American, and Native American preschoolers have an increased incidence of obesity. Black, Native American, Puerto Rican, Mexican, and native Hawaiian school-aged children have the highest rates of obesity in this age group. Approximately 25% of black adolescents are obese. Rosen reported that OSA/H is more commonly seen in black children than in Hispanic or white children.³

Sex

During the second decade of life, females are more likely to be obese than males, except for black teenagers, among whom males are more likely to be obese than females. Although the male sex is associated with an increased incidence of OSA in adults, no differences have been identified in children before puberty.

Age

Adolescent obesity is predictive of adult obesity, with 80% of teenagers who are obese continuing on to be obese as adults. Obesity is more likely to occur during specific periods of life, such as when children are aged 5-7 years and during adolescence. Tonsils and adenoids are at their peak size, relative to the size of the oropharynx, when children are aged 2-7 years.

Clinical

History

Although pediatricians have long valued a good history and physical examination, studies have indicated that the predictive value of the recorded history and physical examination is only 30-50% compared with overnight polysomnography in patients with obesity-hypoventilation syndrome.

• Symptoms during sleep may include the following:
  • Enuresis: This symptom alone has a predictive value for obstructive sleep apnea (OSA) of 46%.
  • Snoring intensity higher than 30 dB: This symptom has a predictive value for OSA of 60%. Characteristically, snoring tends to be worse during flare-ups of nasal allergies and during upper respiratory infections. Approximately 10% of children who snore have significant sleeping and breathing problems.
  • Restless sleep
  • Parasomnias, especially nightmares and sleep walking
  • Witnessed apneas
  • Irregular breathing patterns in sleep
  • Sweating at night
  • Sleep with head extended
• During wakefulness, symptoms may include the following:
  • Chronic mouth breathing
  • Daytime sleepiness: This occurs much less frequently in children with OSA than in their adult counterparts, except in children who are obese.
  • Hyperactivity: Younger children are more likely to show symptoms of sleep deprivation than excessive daytime sleepiness (EDS).
  • Morning headaches
  • Cyanosis
  • Cardiac rhythm disturbances
  • Systemic hypertension, pulmonary hypertension
  • Poor school performance, poor memory, and/or poor concentration
• Careful drug and alcohol history: Sleep apnea and daytime sleepiness can be aggravated by the use of alcohol, sedating antihistamines, CNS depressants, and some over-the-counter (OTC) cold preparations.
• Increased incidence of hyperreactive airways (ie, asthma) is observed in children with who are obese (30%). Decreased exercise tolerance is also observed in children who are obese.

Physical

The physical examination begins in the waiting room. Evaluate sleepy children who cannot stay awake during the course of a physical examination or who consistently are found sleeping in the waiting room.

Less than 10% of children who are obese have endogenous obesity. Therefore each child should be assessed for dysmorphic features, short stature, developmental delay, and abnormal genitalia.

• Vital signs: With obesity, tidal volume can be decreased with a resultant increase in respiratory rate to maintain minute ventilation. Every child who is obese should be screened for hypertension. Hypertension in children is defined as systolic blood pressure, diastolic blood pressure, or both in the 95th percentile or higher on 3 or more separate visits. 
• Color: Cyanosis in this scenario is suggestive of cor pulmonale.
• Nutritional status and body habitus: The degree of obesity and fat distribution have an impact on the degree of respiratory symptoms during wakefulness and sleep. Adjusted body mass index (BMI) in the 95th percentile or higher is most frequently used. BMI is not static during childhood and is age-specific and gender-specific. Skinfold thickness and bioelectric impedance are additional measures for obesity.
• Head, ear, eye, nose, and throat (HEENT) examination: During a HEENT examination, pay specific attention to features of various cardiofacial dysmorphologies, especially those associated with macroglossia, retrognathia, micrognathia, or high-arched palate. Note large tonsils and adenoids, dental malocclusion, and oropharyngeal crowding secondary to a large uvula or low-hanging soft palate. Evidence of nasal obstruction can be sought by simple rhinoscopy. Large adenoids, nasal polyps, cysts, deviation of the nasal septum, and swollen nasal turbinates can limit nasal airflow.
• Neck: Search for evidence of compression secondary to chin folds, excessive fatty deposition, tumors, lymph nodes, or thyroid.
• Chest: Thoracic kyphosis has been associated with obesity. An acquired pectus excavatum due to increased muscle use in overcoming the extrathoracic obstruction with sleep has been described in children with OSA. Some of the syndromes (eg, Prader-Willi syndrome) associated with obesity-hypoventilation syndrome also have an increased incidence of scoliosis. Pay attention to the possibility of additional risk factors for restrictive ventilatory defects. Cor pulmonale may be suspected by a displaced cardiac impulse and a loud pulmonic second (heart) sound (P2). Measured tidal volume may be decreased.
• Abdomen: Abdominal obesity is associated with an upward displacement of the diaphragm, which is more pronounced in the supine position.
• Extremities: Ankle edema, in this context, is suggestive of congestive heart failure. Digital clubbing is associated with pulmonary osteoarthropathy.

Causes

• Drugs
• Environment
• Heredity
• Lifestyle
• Eating habits
• Genetic syndromes

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