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Keywords: Breathing/Obesity/ Nursing Practice Respiration/Ventilation therapy Review ●This article has been double-blind Respiratory care peer reviewed Obesity hypoventilation syndrome affects physical and mental health. Treatment should focus on weight loss but is aided by managing symptoms via non-invasive ventilation Treatment of obesity hypoventilation syndrome

In this article... 5 key The impact of obesity on sleep-disordered breathing points The prevalence Pathophysiology of obesity hypoventilation syndrome 1of obesity is a Outline of the treatment options available growing problem worldwide Obese patients Author Iain Wheatley is nurse consultant, OHS, commonly associated with 2may have acute and respiratory care, Frimley Health obstructive sleep apnoea (OSA), is caused leptin resistance Foundation Trust. by upper airway obstruction, which results Adipose tissue Abstract Wheatley I (2015) Treatment of in recurrent apnoea as well as reduced air 3is a major obesity hypoventilation syndrome. Nursing flow in the airways or hypopnoea (defined contributing factor Times; 111: 51/52, 18-20. as shallow breathing or low respiratory to compromising Aside from being a health concern in itself, rate), oxygen desaturations and frequent respiratory obesity can result in other serious health episodes of sleep arousal. It is estimated function conditions. Some of these, such as cancer, that 10-20% of patients with OSA may also Volume- can result in early death, while others, have OHS (Mokhlesi et al, 2008). Box 1 out- 4targeted including sleep-disordered respiratory lines the characteristics of OHS. non-invasive problems, can compromise patients’ Respiratory hypoventilation and sleep ventilation (NIV) day-to-day quality of life and economic disorders are often unrecognised or under- is an alternative to status. This article explores how obesity diagnosed (Dabal and BaHammam, 2009). standard bilevel affects respiratory disorders and focuses on Simonds (2013) found that OHS often goes NIV obesity hypoventilation syndrome. It unrecognised until patients present with The patient’s outlines the pathophysiology and diagnosis acute hypercapnic respiratory failure. 5ideal weight of the condition, and explains how it can be should be used treated with non-invasive ventilation. Pathophysiology when setting target In people who are obese, adipose tissue tidal volumes survey of obesity prevalence mass in the abdominal and intrathoracic undertaken by Public Health regions hinders the ability of the lungs to England in 2014 shows an fully inflate, mainly by restricting the Aupward trend; this has far- normal movement of the diaphragm reaching consequences on the health of during breathing. Adipose deposits also individuals, from general sleep-disordered change the balance of elastic recoil between breathing to cardiovascular disease, and the chest and lung (Borel et al, 2012a); this from diabetes to certain cancers, ulti- reduces vital capacity (VC) – the maximum mately leading to premature death (PHE, amount of air that can be inhaled and 2014; Borel et al, 2012a). One consequence is exhaled – and functional residual capacity obesity hypoventilation syndrome (OHS), (FRC), the amount of gas in the lungs at the which is defined as a combination of: end of an exhaled tidal volume. This reduc- » Obesity; tion in VC and FRC due to excess adipose » Hypercapnia (high levels of carbon tissue distribution is a key cause of daytime dioxide in the blood in the day); hypercapnia in patients who are obese » Hypoxia (oxygen deficiency); (Laaban and Chailleux, 2005; Resta et » Sleep-disordered breathing in the al, 2001). absence of other disorders that may In a study of 1,141 patients with OSA, cause hypoventilation, such as Laaban and Chailleux (2005) found that significant lung or respiratory muscle those with hypercapnia had significantly disease (Borel et al, 2012b; Mokhlesi et higher weight and body mass index values A full face mask must be worn during the

Alamy al, 2007). and significantly lower VC, forceddelivery of non-invasive ventilation therapy

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For more articles on long-term conditions, Nursing go to nursingtimes.net/longterm Times.net expiratory volume in 1 second (FEV1 – used Box 1. characteristics of ohs to measure lung function and diagnose lung disease) and partial pressure of oxygen ● Obesity: body mass index >30kg/m2 (range for a healthy weight is 18.5-24.9kg/m2) ● in arterial blood (PaO2) values than patients Daytime hypercapnia, or elevated levels of carbon dioxide in the blood (normal with a normal level of carbon dioxide. range 4.6–6.1kPa) ● The following are all major factors that Hypoxaemia (normal range PaO2 12-14.6kPa) cause a change in physiological dynamics ● Sleep-disordered breathing in the absence of other disorders that may cause and the body’s ability to maintain a normal hypoventilation, such as significant lung or respiratory muscle disease (Borel et al, level of carbon dioxide and haemostasis: 2012a; Mokhlesi et al, 2007) » Increased mechanical load; » Restrictive lung impairment; » Increased lung resistance; cause a downward spiral. Patients are gen- who have OHS with hypercapnic respira- » Reduced lung compliance; erally lethargic, which is partly due to poor tory failure could be treated using a similar » Progression to severe muscle weakness. sleep quality, hypercapnia and the struggle bilevel NIV protocol to that used for patients Neuro-hormonal abnormalities in to sustain physical exertion. Reducing the with COPD; further to that, outcomes for patients who are obese are thought to be level of hypoventilation, hypercapnia and patients with OHS were better than for another cause of hypoventilation and sub- modulating associated sleep disorders is those with COPD. Domiciliary bilevel NIV sequent hypercapnia (Mokhlesi et al, paramount to improving pulmonary func- also improves gas exchange, daytime som- 2008). Leptin, a hormone that inhibits tion and sleep quality (Borel et al, 2012b). nolence and quality of life, and reduces hunger, and therefore weight gain, has readmissions to hospital for patients with been found to be raised in obese patients Continuous positive airway pressure OHS (Piper and Grunstein, 2011). and it has been suggested that they may be In patients with primary OSA and OHS, Bilevel NIV devices use inspiratory posi- leptin-resistant (Myers et al, 2010). Tanker- treatment with continuous positive airway tive airway pressure (IPAP) to provide ven- sley et al (1998) found that hypoventilation pressure (CPAP) has been shown to be suc- tilatory support, increasing patients’ tidal could be related to leptin levels, and that cessful (Mokhlesi et al, 2008; National volume when they inhale. Patients may raised levels of leptin and leptin resistance Institute for Health and Care Excellence, trigger the device spontaneously to pro- have also been associated with a reduction 2008). CPAP uses a positive end-expiratory vide the IPAP or, if unable to do this, a in respiratory drive and hypercapnic pressure (PEEP) to: timed breath may be delivered. response in the absence of obesity. » Prevent alveoli from collapsing; At the end of inspiration and start of Obesity may cause a chronic inflamma- » Reduce atelectasis (collapsed lung); exhalation, the device provides expiratory tory pathway that may lead not only lead to » Open the upper airway. positive airway pressure (EPAP). This main- leptin resistance but to also insulin resist- Patients with simple sleep apnoea tains a pressure to allow the alveoli to stay ance and hypofunctioning of hypotha- maintain a patent airway while sleeping, open; helping to prevent collapse of both lamic hormones related to circadian with less disruption to sleep patterns and the lower and upper airway, and allowing a rhythm, causing sleep disorder breathing fewer hypoxic periods. In addition, the gas exchange to take place and improve (Dabal and BaHammam, 2009; Zamarron et reduced level of hypoxia achieved by using PaO2. The pressure level between the IPAP al, 2008; Hatipoglu and Rubinstein, 2003). CPAP reduces the risk of stroke, diabetes and the EPAP is known as pressure support; The more adipose tissue that is accumu- and heart disease. With a better night’s this can be adjusted to increase patients’ lated, the more challenging it is for the body sleep, the patient often experiences less tidal volume, which enables more of the to maintain a normal level of function. With daytime tiredness and can be more active. carbon dioxide to be expelled, with the aim a lower physical capability – that is, how of reducing PaCO2. patients breathe mechanically, and how Bilevel non-invasive ventilation There are risks with high pressures they mobilise – added to the neurohor- In some patients with OHS, CPAP therapy including pneumothorax, so patients monal resistance to various hormones such may be sufficient, but in those with hyper- should be closely monitored in the initial as insulin and leptin – the pathway to physi- capnia and hypoxia the work of breathing stages of therapy. They must wear a nasal or ological deterioration is set. has diminished to such an extent that the full face mask, which must be well sealed to Reduced physical capability and exercise respiratory muscles weaken and are at risk make sure enough pressure is delivered. tolerance also affects patients socially and of further fatigue. In mild OSA, studies Patients can develop pressure ulcers on the psychologically – they may experience a have shown that CPAP and bilevel non- bridge of the nose as a result of wearing the lack of social participation, decrease in invasive ventilation (NIV) can be equally mask (Gregoretti et al, 2002) and wearing a activities of daily life, social isolation, effective at reducing daytime hypercapnia mask can cause discomfort (Kramer et al, unemployment and disability. In short, (Piper et al, 2008). 1995). This leads to adherence problems, OSH may have far-reaching consequences Bilevel NIV in OHS can provide both the which, in turn, as Antonelli et al (2003) affecting patients’ physiological, social, inspiratory pressure and expiratory pres- noted, reduces the duration of use. In financial and hormonal states (Fig 1). sure to enable patients to: patients with a long-term condition and » Reduce the effort required to breathe; domiciliary bilevel NIV, the overall effec- Treatment » Remove waste gases; tiveness can be reduced. Non-acute OHS » Open up the airways. Treatment of OHS involves several strate- Bilevel NIV has been shown to be effec- Average volume-assured gies, with a main focus on weight loss tive in many studies of acute hypercapnic pressure support through diet and exercise. However, symp- respiratory failure in chronic obstructive An alternative to standard bilevel NIV is toms of acute/chronic hypercapnia and pulmonary disease (COPD) (Keenan et al, average volume-assured pressure support hypoxia with sleep-disordered breathing 2011). Carrillo et al (2012) found that patients (AVAPS). This is a volume-targeted mode of

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Nursing Practice Review

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Claudett KHB et al (2013) Noninvasive mechanical Conclusion ventilation with average volume assured pressure For more on this topic go online... There is significant evidence that obesity support (AVAPS) in patients with chronic Non-invasive ventilation in COPD rates are increasing and many obese obstructive pulmonary disease and hypecapnic encephalopathy. BMC Pulmonary Medicine; 13: 12 exacerbations patients have both sleep-disordered doi: 10.1186/1471-2466-13-12. Bit.ly/NTNivCOPD breathing and hypoventilation syndrome Dabal LA, BaHammam AS (2009) Obesity

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