Overview

What is obesity hypoventilation syndrome? 

Obesity hypoventilation syndrome (OHS), also known as Pickwickian syndrome, is a respiratory condition that results from obesity and is characterised by elevated carbon dioxide levels (CO₂) in the lungs causing decreased breathing or hypoventilation during wakefulness, in the absence of other conditions. Early diagnosis and treatment are important as it affects one's daily life activities.¹

How common is obstructive hypoventilation syndrome? 

OHS is closely related to the degree of obesity, measured by the body mass index (BMI). In recent years, some studies have highlighted the rising prevalence of OHS as obesity worsens. Because patients undergoing weight-reducing surgeries are often more obese, the prevalence of OHS in them is predicted to be higher.² 

It is unclear why this syndrome affects some individuals while others don’t, but what's obvious is that the increased fat in the body makes it difficult to breathe and produces hormones that also affect breathing.³

Obstructive sleep apnea versus obesity hypoventilation syndrome

Obstructive sleep apnea (OSA) is the presence of hypoventilation during sleep which causes similar symptoms of OHS, while OHS is a broader term that includes both day and night symptoms. Another difference is that in OSA the body tends to compensate for the accumulation of CO₂ levels while in OHS this compensation is defective resulting in elevated levels of CO₂ (hypercapnia).⁴ Therefore, OHS is a broader term than OSA and their causes differ.

Brief on signs and symptoms of OHS

If you experience difficulty sleeping along with low oxygen blood levels (you can get an insight into this if you have a smartwatch for example), these might cause OHS. Symptoms may include:⁵

• Tiredness at day/night
• Decreased energy
• Morning slowness
• Headache
• Feeling dizzy
• Snoring at night
• Choking or gasping
• Respiratory pause that your partner might notice

Diagnosis of OHS

Hypoventilation, the key feature of OHS, has many causes so it is important to exclude other causes of it such as underlying obstructive respiratory illnesses, neuropathic illnesses that affect the respiratory system and any sedatives or drugs that might cause hypoventilation.⁶

Diagnosis involves taking a history of your symptoms including your sleeping habits and any notes from your partner by your physician. Moreover, your weight and height will be recorded to calculate your BMI and determine the degree of obesity. Your respiratory parameters will be recorded such as respiratory rate, oxygen and carbon dioxide levels either by a non-invasive device called a pulse oximeter or by a prick in your wrist artery.

A chest x-ray and pulmonary function tests may be performed to rule out any other potential reasons for your difficulties with breathing. To determine if OSA is present along with OHS, a sleep study (also known as polysomnography) is usually done, although it is not required for the diagnosis of OHS.

If you are susceptible to OHS, you must determine whether you have sleep apnea and how serious it is. Furthermore, the sleep study may be used to determine the efficacy of continuous positive airway pressure (CPAP machine) in treating OSA and hypoventilation during sleep.⁷

Treatment options for OHS

Lifestyle modifications

The first logical treatment option that can come across anyone’s mind is weight reduction. Losing weight improves the physiological imbalances involved in the pathology of OHS. In individuals with OHS and concurrent OSA syndrome, weight reduction decreases the amount of sleep-disordered breathing episodes (apneas and hypopneas) and decreases daytime hypercapnia thus sleepiness.⁸ 

Another lifestyle modification option that can improve your symptoms is quitting smoking. Smoking is known to cause a direct damaging effect on your lungs thus aggravating hypercapnia and hypoxia.

Non-invasive ventilation

The idea behind using positive airway pressure ventilation is to open the airways and lung sacs (alveoli) leading to continuous exchange of gasses through its membrane thus improving sleepiness during daytime. There are two types of positive-pressure ventilation: 

• CPAP (continuous airway pressure)– It delivers continuous positive airway pressure
• BiPAP (bilevel positive airway pressure)–It uses two modes for delivering air to the lungs and can be automatically adjusted 
• Other non-invasive modalities (NIV)

The recent recommendation for individuals who have both OHS and OSA is to use CPAP instead of NIV.⁹ You can discuss these options with your physician and it is convenient to use these devices nowadays. 

Surgical options: bariatric surgeries

Bariatric surgeries (surgeries to reduce weight) are an option for individuals who have high BMI and have tried other weight-reducing measures and failed. The National Institutes of Health (NIH) discusses surgical treatment options for obesity and obesity with coexisting medical problems.

These guidelines state that patients with a body mass index of more than 40 kg/m2 and those with a body mass index of more than 35 kg/m2 who also have an obesity-related comorbid condition (including OHS) are indicated for surgical treatment.⁹

Diaphragmatic pacing

Diaphragmatic pacing means surgically placing an electrode onto the phrenic nerve, which is the nerve that stimulates the diaphragm. This electrode is connected to a subcutaneous (under the skin) receiver which is battery-operated. The device settings are adjusted based on the respiratory rate and volume of air entering the lungs. It allows proper oxygen delivery and removal of carbon dioxide. The disadvantage of this method is that it causes irreversible damage to the phrenic nerve over time.^10,11

Pharmacological interventions

Oxygen therapy

Your physician may prescribe oxygen therapy to you if you have hypoxaemia or low partial pressure of oxygen during the daytime. Long-term hypoxaemia could lead to deleterious effects on the whole body thus oxygen therapy is indicated in patients with OHS and COPD at the same time. 

However, oxygen therapy should be used cautiously because if too much oxygen is used, hypercapnia can develop in some situations. Additionally, in most cases, oxygen treatment shouldn't be administered to patients with neuromuscular illness without ventilatory assistance.

Respiratory stimulants

Respiratory stimulants are drugs that stimulate respiration. They should be the last option when other modalities fail.¹² Examples of these are:

• Medroxyprogesterone – acts centrally on the brain by stimulating the respiratory centre therefore regulating breathing. The dose is divided 2 to 3 times per day. However, the drug has little to no effect on improving sleepiness or apnea interval thus many experts do not recommend using it
• Acetazolamide – it works by creating a state of acidosis in the blood that in turn stimulates respiration. It should be used cautiously as it may lead to abnormal heartbeats (cardiac dysrhythmias)
• Theophylline – though it has limited use, it works by stimulating both the diaphragm and the respiratory centre in the brain

Prognosis of OHS

It is anticipated that a multimodal and multidisciplinary therapeutic strategy combining weight loss and rehabilitation programmes with non-invasive ventilation will have a higher influence on the outcomes related to heart and metabolism. It has been demonstrated that losing weight improves respiratory drive, respiratory muscle strength, lung function, and sleep-disrupted breathing. Numerous research studies have demonstrated the effects of weight loss by showing notable improvements in gas exchange and pulmonary function testing. 

If OHS is not addressed, it can result in possible fatal outcomes such as heart and blood vessel problems. A deficiency of oxygen causes your heart to work harder. You run the chance of experiencing issues linked to sleep deprivation as well. Your risk of hospitalisation rises and your quality of life declines without therapy.

For those who do not receive therapy, the prognosis is not good. Death from obesity-related hypoventilation syndrome usually results from untreated cases. Over 18 months, the death rate from OHS is 23% in individuals with underlying medical issues.⁵

Complications of OHS

OHS can lead to consequences from inadequate sleep if left untreated. These issues might include:

• Feeling depressed
• Irritation and agitation
• Higher chance of accidents
• Sexual problems
• Cardiac problems such as elevated blood pressure (hypertension), heart failure on the right side, or elevated pulmonary blood pressure (pulmonary hypertension)

Summary

Obesity hypoventilation syndrome is a treatable complication of obesity, although serious. As long as obesity leads, there will always be a rise in the prevalence of OHS. It is sometimes misdiagnosed and usually underdiagnosed. Patients have a low quality of life associated with their health, a high mortality rate, longer hospital stays, and deterioration of co-morbidities related to their disease if they go untreated and undetected. 

Diagnosis involves excluding other respiratory disorders and evaluating respiratory parameters, sometimes using a sleep study. Treatment options include bariatric surgery or weight reduction through lifestyle modifications. The best breathing techniques are non-invasive ones like CPAP, however diaphragmatic pacing and medication treatments are also available.

Losing weight and using interdisciplinary methods improves the prognosis because untreated OHS can cause serious consequences like heart issues and even death. Untreated OHS increases the risk of depression, heart problems, and sexual dysfunction, underscoring the significance of prompt treatment.