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1 Service de Gastroentérologie et Nutrition, Clinique Résidence du Parc, Marseille, 2 Dépt de Médecine Aiguë Spécialisée, Centre Hospitalier Universitaire (CHU), Grenoble, 3 Service de Pneumologie, CHU, Saint-Etienne, 4 Service de Biochimie A and 5 Service de Pneumologie et de Réanimation Respiratoire, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôtel-Dieu, Paris, 6 Service de Réanimation Médicale et d'Assistance Respiratoire, Hospices Civils de Lyon, Lyon, 7 Service de Pneumologie, CHU, Rouen, and 8 Service des Maladies Infectieuses, 9 Service de Réanimation Médicale, AP-HP, Hôpital Raymond Poincaré, Garches, France, 10 Dépt de Nutrition Clinique, Hôpital Cantonal Universitaire, Genève, Suisse
CORRESPONDENCE: C.M. Pison, Dépt de Médecine Aiguë Spécialisée, Pneumologie, Hôpital A. Michallon, Centre Hospitalier Universitaire de Grenoble, BP217X 38043, Grenoble Cedex 9, France. Fax: 33 476765617. E-mail: CPison@chu-grenoble.fr
Keywords: bioelectric impedance, fat-free mass, hypoxaemia, long-term oxygen therapy, malnutrition, smoking
Received: October 10, 2001
Accepted January 17, 2002
The present study was supported by the Société Francophone de Nutrition Entérale et Parentérale and Astra-Zeneca, France.
| Abstract |
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In 744 patients (M:F 1.68, aged 65±15 yrs) with chronic obstructive pulmonary disease (COPD, 40%), restrictive disorders (27%), mixed respiratory failure (15%), neuromuscular diseases (13%) and bronchiectasis (5%), body mass index (BMI), fat-free mass (FFM), serum albumin, transthyretin, 6-min walking test, forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and blood gases were recorded.
FFM was the most sensitive parameter for detecting malnutrition, being abnormal in 53.6% of patients, while BMI was <20 in 23.2%, serum albumin <35 g·L1 in 20.7 %, and serum transthyretin <200 mg·L1 in 20%. FFM depletion predominated in neuromuscular, bronchiectasis and restrictive disorders. BMI and FFM were correlated with FEV1, FVC and 6-min walking test. In multivariate analysis a BMI<20 was related to FEV1 and smoking habits, and a low FFM to smoking, FEV1 and female sex.
Malnutrition is highly prevalent in home-assisted respiratory patients and is related to causal disease, forced expiratory volume in one second, smoking and disability. Fat-free mass appeared to be the most sensitive and relevant nutritional parameter according to impairment and disability.
The association between nutritional depletion and chronic respiratory diseases has been recognised for many years and mainly documented in chronic obstructive pulmonary disease (COPD) 14. In this setting, body weight loss and muscle wasting have an impact on physical performance and respiratory muscle function and are responsible for an increase in healthcare requirements independently of the degree of airflow obstruction 5. In COPD patients with chronic respiratory failure, long-term oxygen therapy (LTOT) and/or home mechanical ventilation (HMV) improve survival. Nevertheless, in such patients, the prognosis remains poor with a median survival of 3 yrs in COPD patients receiving LTOT 6. Nutritional status appears to be a major factor for survival in these patients independently of lung function 4, 6, 7. Conversely, nutritional support has been shown to improve body weight, fat-free mass (FFM), respiratory muscle function 8, 9 and prognosis in COPD patients 10. Until now, the assessment of nutritional status in chronic respiratory failure patients on LTOT and/or HMV was based mainly on the calculation of body mass index (BMI, weight/height2) 4, 6, and data are lacking for important parameters such as body composition and protein markers of malnutrition. In addition, the reliability of BMI as a nutritional marker can be questioned in chronic respiratory disease due to fluid retention or obesity 3. Thus, a more complete evaluation of nutritional status and of its relationship with the causes, the severity of respiratory failure and related inflammatory status is of major interest, particularly for screening patients requiring nutritional interventions during rehabilitation.
The aims of the present study were to: estimate the prevalence of malnutrition using various nutritional parameters according to the cause of chronic respiratory failure; determine the relationships between nutritional status and respiratory impairment/disability and smoking; identify clinically-relevant tools for routine nutritional assessment.
| Methods |
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8 kPa at initiation of home treatment (not requested for neuromuscular patients) and informed consent. Exclusion criteria were sleep apnoea syndrome, history of exacerbation during the last 3 months and any condition compromising the prognosis within 6 months. Five respiratory diseases groups were considered: COPD, bronchiectasis, neuromuscular diseases, restrictive disorders (including pulmonary fibrosis and chest wall diseases) and mixed respiratory failure. The study protocol was approved by the Ethical Committee of the Société Francophone de Nutrition Entérale et Parentérale. The length and type of home treatment, underlying respiratory disease, blood gases in room air and with LTOT/HMV, forced expiratory volume in one second (FEV1), forced vital capacity (FVC) 11, and 6-min walking distance test 12 in room air were recorded. The body weight was noted at the time of enrolment and 1 yr prior to this and expressed as per cent of ideal body weight in medium frame size (BW%IBW) according to life insurance tables 13. Fat mass and FFM were evaluated using bio-electric impedance in 35.2% of patients (50 kHz apparatus, STAR 50; Spengler®, Paris, France) and calculated according to a specific formula 14. FFM and fat mass were expressed as per cent of IBW (FFM%IBW) 3. Serum albumin, transthyretin (prealbumin) and C-reactive protein were determined using conventional methods. A quality control of participating laboratories resulted in exclusion of albumin and transthyretin data from two centres (variation coefficient >10%), and C-reactive protein data from one. For each parameter, malnutrition was defined as: body weight loss >10% during the year before enrolment, BW%IBW <90%, BMI <20 kg·m2, FFM%IBW <63% in females or<67% in males, serum albumin <35 g·L1 or serum transthyretin <200 mg·L1 3. Patients were classified as corticoid users if they had been given oral corticoids for >3 months during the previous year. The number of antibiotic courses was recorded during the same period.
Results are presented as mean±sd. Analysis of variance was used to compare continuous variables between the five respiratory disease groups, with post hoc analysis using Fisher's Predicted Least Significant Difference test. The Chi-squared test was used to compare modalities of respiratory assistance. Relationships between nutritional parameters as well as between nutritional and functional parameters were tested using the Pearson's-correlation matrix with the Fisher's Z test. Determinants of BMI <20 were determined in the whole population, as well as in the subgroup of patients with FFM determination, using univariate and multivariate logistic regression analysis. Similarly, determinants of FFM%IBW <63% in females and <67% in males were established.
| Results |
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5.86 kPa without between-group differences. Hypoxaemia was more pronounced in COPD patients. Neuromuscular patients presented the highest Pa,O2 and the lowest FVC. Hypoxaemia was corrected by LTOT and/or HMV whereas hypercapnia was only corrected by HMV. Twenty-two per cent were unable to complete the 6-min walking test and 20% required oxygen to perform this test. In non-neuromuscular patients, the 6-min walking distance was 238±107 m and did not vary according to the causal disease.
Nutrition and inflammation assessment
The nutrition and inflammation assessments are shown in (table 3
). The median of body weight variation during the 12 months before the nutritional survey was equal to zero (data not shown). A loss in body weight
10% within 1 yr was noted in 6.8% of patients. BW%IBW differed significantly according to respiratory disease, with bronchiectasis and neuromuscular diseases being the most depleted. BMI was similar in males and females (data not shown) and varied significantly according to respiratory diseases. FFM%IBW varied according to the lung disease. Among non-neuromuscular patients, bronchiectasis subjects exhibited the lowest FFM. Serum albumin varied according to lung disease, with neuromuscular patients exhibiting the highest values. These differences persisted after adjustment for age. The median of serum C-reactive protein was 5 mg·L1 and C-reactive protein was >10 mg·L1 in 27.8%.
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In univariate analysis, FFM depletion, defined by FFM%IBW <63% in females or <67% in males, was related to smoking habits (FFM%IBW lower in active smokers than in exsmokers and nonsmokers, Chi-squared=19.1, p<0.0001), FEV1 % pred (Chi-squared=8.3, p<0.01), sex (females more depleted, Chi-squared=5.5, p<0.05) and age (FFM%IBW decreased with ageing, Chi-squared=5.1, p<0.05), whereas in multivariate analysis FFM depletion was determined by smoking habits (Chi-squared=15.7, p=00004), FEV1 % pred (Chi-squared=12.1, p=0.0005)and sex (Chi-squared=5.1, p=0.02).
| Discussion |
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The comparison of the present study with the ANTADIR study 6 showed that the two series were very similar and suggested that the present data are representative of French patients on LTOT and/or HMV. In fact, in each group of lung disease, age and sex distribution as well as Pa,O2 in room air, FVC and FEV1 % pred were similar. However, due to a higher recruitment of neuromuscular patients, a greater proportion of neuromuscular disease was observed (12.9 versus 4.2%). Another difference was the higher proportion of patients with HMV, which probably reflected recent changes (since the beginning of the 1980s) in home management of respiratory failure.
Nutritional data varied according to lung disease (table 3
, fig. 1
). Most studies 2, 3, 7, 518 have examined stable, non-LTOT and/or HMV COPD outpatients. Very few studies 6, 19 have been specifically devoted to the nutritional status of COPD patients on LTOT and/or HMV. In the present series, the percentage of COPD patients with BMI <20 kg·m2 (17.3%) appeared to be lower than in the Maastricht series 3, 19. When compared to the most severe COPD patients from the Maastricht group, COPD patients from the present series showed a lower prevalence of malnutrition. In the present COPD series, BW%IBW was <90% in 23.3 versus 46% in the Maastricht study 3, FFM%IBW <63% in females and 67% in males in 37.5 versus 48%, serum albumin <35 g·L1 in 23.8 versus 44%, and serum transthyretin <200 mg·L1 in 17.1 versus 23%. Data evaluating the role of smoking habits and subtypes of COPD (emphysema versus chronic bronchitis), which may explain the differences between the two series, are lacking. The difference between the results achieved in the two studies may be related to the much higher use of corticoids in the Maastricht series (73.9 versus 14% in the present study) 19. The same group recently reported a negative relationship between maintenance treatment with oral corticoids and BMI 19.
Non-COPD patients with LTOT and/or HMV form an inhomogeneous group in which nutritional status has been poorly studied. When compared with data from the ANTADIR study 15, the patients in the present study presented with a similar BMI in the different groups of causal disease, with bronchiectasis and neuromuscular diseases showing the lowest values (table 3
, fig. 1
). Patients with bronchiectasis as compared with COPD, showed significantly lower values of BW%IBW, BMI and FFM%IBW. Considering the different groups of lung diseases, patients with bronchiectasis also exhibited the lowest values of serum albumin and transthyretin and the highest values of serum C-reactive protein. Although between-group differences were not always significant, these data suggest a higher inflammatory activity in patients with bronchiectasis 20. As described previously in younger patients with Duchenne disease 2122, neuromuscular patients are characterised by the magnitude of FFM depletion. However, most of these patients showed normal serum albumin, transthyretin and C-reactive protein suggesting that in these patients muscle wasting was mostly determined by muscle disease and not by malnutrition or inflammation. As compared to COPD, restrictive disorders and mixed respiratory failure were characterised by a higher proportion of patients with reduced FFM%IBW.
Figure 1
and table 3
showed that FFM was the most sensitive tool for detecting malnutrition: FFM was altered in 3780% of patients according to respiratory disease groups, while BMI was <20 in only 1739%. Although it was recognised that overall correlation between nutritional parameters and respiratory impairment/disability was weak (table 5
), FFM appeared to be better correlated than BMI with functional parameters such as FEV1, FVC and 6-min walking test. The interest of FFM evaluation would have probably been strengthened if this parameter had been available in a higher number of patients. Malnutrition per se was previously reported to impair diaphragm function, as assessed by lung volumes, in severely malnourished patients with anorexia nervosa 23. The apparently paradoxical inverse relationship between Pa,O2 in room air and BMI and FFM may be explained by a higher oxygen consumption due to a bigger body cell mass. Another explanation may be related to the variations of Pa,O2 according to the subtype of COPD patients. When compared to chronic bronchitis patients, emphysematous patients are characterised by a more pronounced depletion and a higher Pa,O2 in room air 24. Interestingly, transthyretin appeared to be correlated in a coherent manner with BMI, FFM, lung volumes and Pa,CO2. Both albumin and transthyretin were negatively correlated with C-reactive protein showing that during respiratory failure, as in other diseases, albumin and transthyretin serum levels are dependent on both nutritional status and inflammation 25. The prognostic values of these plasma proteins remain to be evaluated.
Although a relationship between malnutrition and inflammation, as assessed by plasma tumour necrosis factor (or the soluble 55 fraction of the receptor to TNF, was reported in stable COPD patients 20, 26, 27, in the present series BMI and FFM%IBW were not related to serum C-reactive protein. Multivariate analysis showed that BMI was independently determined by FEV1 and smoking habits and that FFM%IBW was related to FEV1, smoking habits and sex. These data are consistent with the effects of smoking on food intake 28 and energy expenditure 29 and underline the deleterious effects of active smoking on nutritional status in patients with chronic respiratory failure. Similarly, airflow obstruction has been proposed as a factor of hypermetabolism in COPD patients, particularly during exacerbations 30.
To conclude, the present study is the first specifically devoted to the nutritional assessment of a population of stable outpatients, defined by hypoxaemia or hypercapnia, requiring long-term oxygen therapy or/and home mechanical ventilation. Fat-free mass and fat mass, expressed as a per cent of the ideal body weight, was more sensitive than the body mass index for detecting malnutrition and showed better correlation with ventilatory pump and disability. Airflow obstruction and smoking habits appeared to be independent determinants of malnutrition. A cohort study is required in order to analyse the predictive value of these nutritional parameters on patient morbidity and mortality.
| Acknowledgements |
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| References |
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