Nutritional supplementation for stable chronic obstructive pulmonary disease

Low body weight is common in people with chronic obstructive pulmonary disease (COPD). It can weaken their heart and lung function, and reduce their ability to exercise. Some degree of malnutrition is common in people with COPD but it is unclear whether this is the cause of their deterioration, or just part of the progress of the disease. This review of 17 studies (632 participants) that provided nutritional supplementation for patients with COPD for more than two weeks found growing evidence that nutritional supplementation improved body weight, respiratory muscle strength, walking and quality of life.

Authors' conclusions: 

We found moderate-quality evidence that nutritional supplementation promotes significant weight gain among patients with COPD, especially if malnourished. Nourished patients may not respond to the same degree to supplemental feeding. We also found a significant change from baseline in fat-free mass index/fat-free mass, fat mass/fat mass index, MAMC (as a measure of lean body mass), six-minute walk test and a significant improvement in skinfold thickness (as measure of fat mass, end score) for all patients. In addition, there were significant improvements in respiratory muscle strength (MIP and MEP) and overall HRQoL as measured by SGRQ in malnourished patients with COPD.

These results differ from previous reviews and should be considered in the management of malnourished patients with COPD.

Read the full abstract...
Background: 

Individuals with chronic obstructive pulmonary disease (COPD) and low body weight have impaired pulmonary status, reduced diaphragmatic mass, lower exercise capacity and higher mortality than those who are adequately nourished. Nutritional support may be useful for their comprehensive care.

Objectives: 

To assess the impact of nutritional support on anthropometric measures, pulmonary function, respiratory and peripheral muscles strength, endurance, functional exercise capacity and health-related quality of life (HRQoL) in COPD.

If benefit is demonstrated, to perform subgroup analysis to identify treatment regimens and subpopulations that demonstrate the greatest benefits.

Search strategy: 

We identified randomised controlled trials (RCTs) from the Cochrane Airways Review Group Trials Register, a handsearch of abstracts presented at international meetings and consultation with experts. Searches are current to April 2012.

Selection criteria: 

Two review authors independently selected trials for inclusion, assessed risk of bias and extracted the data. Decisions were made by consensus.

Data collection and analysis: 

We used post-treatment values when pooling the data for all outcomes, and change from baseline scores for primary outcomes. We used mean difference (MD) to pool data from studies that measured outcomes with the same measurement tool and standardised mean difference (SMD) when the outcomes were similar but the measurement tools different. We contacted authors of the primary studies for missing data.

We established clinical homogeneity prior to pooling. We presented the results with 95% confidence intervals (CI) in the text and in a 'Summary of findings' table.

Main results: 

We included 17 studies (632 participants) of at least two weeks of nutritional support. There was moderate-quality evidence (14 RCTs, 512 participants, nourished and undernourished) of no significant difference in final weight between those who received supplementation and those who did not (MD 0.69 kg; 95% CI -0.86 to 2.24). Pooled data from 11 RCTs (325 undernourished patients) found a statistically significant weight gain (MD 1.65 kg; 95% CI 0.14 to 3.16) in favour of supplementation; three RCTs (116 mixed population) found no significant difference between groups (MD -1.28 kg; 95% CI -6.27 to 3.72). However, when analysed as change from baseline, there was significant improvement with supplementation: 14 RCTs (five of which had imputed SE), MD 1.62 kg (95% CI 1.27 to 1.96 ); 11 RCTs (malnourished), MD 1.73 kg (95% CI 1.29 to 2.17) and three RCTs (mixed), MD 1.44 kg (95% CI 0.68 to 2.19).

There was low-quality evidence from five RCTs (six comparisons, 287 participants) supporting a significant improvement from baseline for fat-free mass/fat-free mass index (SMD 0.57; 95% CI 0.04 to 1.09), which was larger for undernourished patients (three RCTs, 125 participants; SMD 1.08; 95% CI 0.70 to 1.47). There was no significant change from baseline noted for adequately nourished patients (one RCT, 71 participants; SMD 0.27; 95% CI -0.20 to 0.73), or for a mixed population (two RCTs, 91 participants; SMD -0.05; 95% CI -0.76 to 0.65).

There was moderate-quality evidence from two RCTs (91 mixed participants) that nutritional supplementation significantly improved fat mass/fat mass index from baseline (SMD 0.90; 95% CI 0.46 to 1.33).

There was low-quality evidence (eight RCTs, 294 participants) of an increase in mid-arm muscle circumference change (MAMC; MD 0.29; 95% CI 0.02 to 0.57).

There was low-quality evidence (six RCTs, 125 participants) of no significant difference in change from baseline scores for triceps measures (MD 0.54; 95% CI -0.16 to 1.24).

There was low-quality evidence (five RCTs, 142 participants) of no significant difference between groups in the six-minute walk distance (MD 14.05 m; 95% CI -24.75 to 52.84), 12-minute walk distance or in shuttle walking. However, the pooled change from baseline for the six-minute walk distance was significant (MD 39.96 m; 95% CI 22.66 to 57.26).

There was low-quality evidence (seven RCTs, 228 participants) that there was no significant difference between groups in the forced expiratory volume in one second (FEV1; SMD -0.01; 95% CI -0.31 to 0.30) when measured in litres or percentage predicted.

There was low-quality evidence (nine RCTs, 245 participants) of no significant between group difference in maximum inspiratory pressure (MIP; MD 3.54 cm H2O; 95% CI -0.90 to 7.99), but those who received supplementation had a higher maximum expiratory pressure (MEP; MD 9.55 cm H2O; 95% CI 2.43 to 16.68). For malnourished patients (seven RCTs, 189 participants), those with supplementation had significantly better MIP (MD 5.02; 95% CI 0.29 to 9.76) and MEP (MD 12.73; 95% CI 4.91 to 20.55).

There was low-quality evidence (four RCTs, 130 participants) of no significant difference in HRQoL total score (SMD -0.36; 95% CI -0.77 to 0.06) when pooling results from both the St George's Respiratory Questionnaire (SGRQ) and the Chronic Respiratory Questionnaire (CRQ).

Two trials (67 participants) used the SGRQ to measure individual domains of activity, impact and symptoms. At the end of treatment, the pooled total SGRQ score was both statistically and clinically significant (MD -6.55; 95% CI -11.7 to -1.41). The three RCTs (123 participants) that used the CRQ to measure the change in individual domains (dyspnoea, fatigue, emotion, mastery), found no significant difference between groups.

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