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Maintaining nutritional status in COPD patients

David Proud
Registered Dietitian
Specialist Dietitian
Pulmonary Rehabilitation Unit
University Hospital Llandough

Charlotte E Bolton
Clinical Senior Lecturer in Respiratory Medicine
Honorary Consultant
University of Nottingham and Nottingham University Hospital Trust

While COPD is primarily a respiratory disease leading to breathlessness, sputum production and impaired exercise tolerance, there are important systemic consequences, of which malnutrition is one. This article will focus on the nutritional aspects of COPD care

COPD is a worldwide problem and, in the UK, nearly a million people have been diagnosed, with a further estimated 2 million remaining undiagnosed.1 COPD is defined as airflow limitation that is not fully reversible. By far the most common cause in the UK is smoking. Recent COPD guidelines from the National Institute for Health and Clinical Excellence (NICE) have highlighted the importance of multidisciplinary support.1

Optimising nutrition is a fundamental aspect of management in patients with COPD. Identifying patients and addressing any malnutrition can be challenging. Prompt referral to a dietitian should be made where outlined, but this article summarises practical advice on nutritional issues for the COPD patient that can be adopted with patients in our clinics.

What is malnutrition?
The British Association for Parenteral and Enteral Nutrition (BAPEN) defines malnutrition as "a state of nutrition in which a deficiency, excess or imbalance of energy, protein, and other nutrients causes measurable adverse effects on tissue (shape, size, composition), function and clinical outcome".2 Both under- and over-nutrition can have a disabling effect. Standard assessments of malnutrition can include body mass index (BMI), waist circumference, weight change over a period of time or measurement of fat/non-fat mass.

Assessment of malnutrition in COPD
The simple assessment tool of BMI is calculated by dividing weight (kilograms) by the square of height (metres). Standard World Health Organization (WHO) BMI categories have been adapted to be COPD applicable (see Table 1). Given that COPD affects an older population with the possibility of height loss, postural change and change in the muscle:fat ratio - none of which BMI accounts for - other parameters, such as change in absolute weight, are important to recognise.

[[Tab 1 COPD]]

In COPD, BMI should be measured at diagnosis and at least annually, and more regularly in severe and very severe airways obstruction. However, severity of COPD is not just airways obstruction and one composite measure, the BODE index: B (BMI), O (obstruction), D (dyspnoea) and E (exercise tolerance) is gaining recognition.3 BMI offers prognostic information. The MUST (Malnutrition Universal Screening Tool) may provide a useful screening tool but there is little relating to this screening in COPD currently.2 The MUST score is a composite score of BMI, weight loss and also the score accounts for acute disease states that may further hinder nutritional intake.

Waist circumference
In the general population, an increased waist in subjects with a BMI from 25 to 35 kg/m2 adds further risk to health.4 It has not been specifically explored in subjects with COPD and is not applicable to BMI outside this range.

Body composition
The body is composed of fat and fat-free mass (FM and FFM); the latter comprising skeletal muscle, water, bone and organs. It is possible to lose FM or FFM disproportionately to each other; however, loss in one may be masked by the other and, therefore, is not apparent on BMI. Unfortunately, there are no "quick and cheap" assessment options to predict FFM. Methods encompass skin calliper recording of fat tissue;5,6 bio-electrical impedance using a validated machine that passes a small electric signal through the body tissue and calculates body composition depending on resistance encountered; or DEXA - the device routinely used to calculate bone mineral density, osteoporosis and can also body composition. All options, however, have limitations that may affect their applicability, reliability and ability to monitor change. Skin calliper measurements rely heavily on operator skill and experience, valid BIA units are expensive and dependent on hydration status and DEXA is not routinely used in the clinical setting.

People with COPD are at risk of over-consuming macronutrients (fat, carbohydrate, and protein, all providing calories) for the same reasons as the rest of the population. However, some factors are particularly amplified in these patients - weight gain associated with smoking cessation due to increased calorific intake, reduced metabolic rate and/or reduced activity levels.7 Additionally, subjects with COPD can be less active due to breathlessness. Oral corticosteroid treatment can stimulate appetite. There is an increased risk of
insulin resistance and diabetes with COPD.8 Excess weight contributes to the additional load on the respiratory system and can worsen breathlessness.

Recommendations for patients with increased BMI
The NICE COPD guidelines recommend that anyone with a BMI above the "normal" range (20-25 kg/m2) should be referred to the local dietetic service for specialist advice. In the meantime, discussing the implications of weight gain and, importantly, firstline healthy eating advice can be empowering for the patient (Table 2). It is helpful to recommend improving activity levels, which, if the subject has a MRC breathless score of 3 or more should be through pulmonary rehabilitation.

[[Tab 2 COPD]] 

Being underweight has been classically associated with the emphysema subtype of COPD for decades. It has been the focus of considerable research in recent years and the complex mechanisms thought to be driving the process are being unravelled. Previously nihilistic, we now know that with appropriate assessment and intervention, malnutrition can be prevented, minimised or even reversed. The prevalence of low BMI varies depending on the method used and time point - whether assessed at stability or during a hospital admission and on the severity of the airflow obstruction. Clinical studies suggest over 25% can have a low BMI.9-11
Originally, the cause of being underweight was felt to be a simple imbalance of low energy intake for the energy expended; with impaired pulmonary mechanics due to the COPD increasing the work of breathing. However, the increased inflammation circulating and hormonal imbalance add further. Intake can be impaired by the increased effort required for eating and feeling bloated, discussed further below. Added to that, inactivity causes muscle deconditioning, leading to loss of muscle mass and function.

During an exacerbation of COPD, there is even more work of breathing, more inflammation and often bedrest. In addition, the treatment for exacerbations such as steroids and antibiotics make these exacerbation periods particular "at risk" periods for undernutrition.

There is an increased risk of all cause mortality in patients with COPD with a BMI

Recommendations for patients with low BMI
If BMI is

[[Tab 3 COPD]]

Studies of ONS in subjects with COPD tend to be small and of limited duration, but indicate nutritional repletion, improved exercise performance and restoration of FFM when combined with exercise.15 They can take various forms including milk-based products, fruit juice, yoghurt and dessert. Offering choice improves compliance but usually necessitates trying several first. They deliver both macronutrients and micronutrients (vitamins and minerals) with some products favouring specific protein:carbohydrate balances.

However, it is important to remember ONS are designed to supplement an optimal dietary intake and not become meal replacements. Over-prescription of ONS has been shown to be ineffective as a result of a decrease in habitual food intake.16 Educating patients is paramount - that they are burning lots of calories even if activity is low. Nasogastric tube (NGT) feeding is not routinely recommended for subjects. In patients with extremely low BMI, particularly at times of exacerbations where there is further negative energy balance, NGT may be considered in conjunction with the dietitian, medical team and, importantly, the patient.

Other common factors affecting intake
Subjects with COPD can often struggle to consume an adequate amount of nutrients for several reasons. Let's try to deal with a few of the most common of these.

Early meal fatigue
Increased breathlessness, particularly at mealtimes, is a regular complaint. See Table 4 for possible causes. Early meal fatigue can contribute to under-nutrition. In addition, patients requiring non-invasive ventilation (NIV) have an increased risk of aerophagia.

[[Tab 4 COPD]]

Patients who require oxygen during meals should be advised on the correct delivery system to allow oxygenation but not restrict eating.

Dry mouth
Table 5 identifies common causes of a dry mouth and provides suggested strategies to resolve the cause.

[[Tab 5 COPD]]

Rsk of constipation is increased in patients with COPD due to poor dietary balance, especially if low fibre intake, but also due to the inactivity, often inadequate fluid intake. In addition, medication can contribute. Constipation leading to straining when passing stools may also worsen breathlessness. General advice encourages adequate fluid intake, fibre-rich foods and aiming for five portions of fruit and vegetables.

Social and psychological pressures
Social pressures can be significant and common, ultimately threatening to impact on the individual's ability to stay nourished. Reasons include social isolation, lack of family or care support and inability to cope with everyday life, financial difficulties, lack of cooking skills and/or facilities. Depression is common in subjects with COPD, but is often unrecognised. Similarly, anxiety is frequently experienced. Both conditions can significantly impact on a person's desire or ability to eat a balanced diet.

Iatrogenic causes
In considering malnutrition, it is important to consider iatrogenic causes. This may include inhaled corticosteroid leading to oral candidiasis or taste changes. Anticholinergics also lead to a dry mouth. Good inhaler technique, gargling and even changing method of inhaler delivery can be considered. Antibiotics can lead to numerous gastrointestinal (GI) side-effects including taste change, oral candidiasis, nausea and diarrhoea. Theophyllines and PDE4 inhibitors medication are also associated with GI symptoms which need to be considered in managing patients. Oxygen can also dry the mouth and oxygen and NIV masks can be physical barriers to eating.

Risk of osteoporosis
A further malnutrition experienced in COPD is osteoporosis. Originally perceived to be related to severe disease or oral corticosteroid use, it occurs in both males and females, and even in those with milder airflow obstruction. In addition to general risk factors, such as an older population and smoking, oral corticosteroid medication, sedentary lifestyle, poor diet, hormone imbalance, low BMI and inflammation may play a role. Standard recommendations including ensuring adequate calcium and vitamin D intake are beyond the scope of this review. Identifying osteoporosis in patients with COPD is imperative, especially if there are additional risks with subsequent appropriate medical therapy and addressing modifiable risk factors relating to lifestyle.

A place for pulmonary rehabilitation
Management of the COPD patient needs to address nutritional aspects and ensure optimal status. This often demands a multidisciplinary approach. Pulmonary rehabilitation may provide the opportunity for this by allowing correct prescription of exercise for both ends of the BMI spectrum and recognition of muscle dysfunction with the physiotherapist. In addition, exercise is an anabolic stimulus.

Social and psychological barriers and also drug side-effects can be addressed while encouraging a healthy lifestyle and optimal nutritional input in conjunction with the dietitian. General education can be administered to the rehab class on nutrition but additionally it often necessitates an individual consultation to address specific matters and allow follow-up both during and after rehabilitation. A very low BMI may necessitate specific nutritional input first to allow build up of muscle bulk and ensure the subject is receiving sufficient calories to then expend during the rehab class.

COPD is not just confined to the lungs but has important systemic consequences. Addressing nutritional care is imperative and a task for the multidisciplinary team. While the dietitian is ideally placed to provide specialised nutritional support, there are management strategies that all of the team can consider with their patients. However, first and foremost is considering and assessing nutritional status.

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