Adverse effect of additional weight on exercise against gravity in patients with chronic obstructive airways disease

Is the six-minute step test able to reflect the severity and symptoms based on cat score?

BACKGROUND

This is the first study to investigate the performance of 6MST in COPD patients divided into different symptom severity groups based on the CAT questionnaire score.

OBJECTIVES

To evaluate the relationship between the degree symptomatology using the chronic obstructive pulmonary disease (COPD) Assessment Test (CAT) with the six- minute step test (6MST) in COPD patients.

METHODS

This is a cross-sectional study in which 59 patients with COPD were evaluated. The groups were stratified according to the subsequent cutoff points: CAT <10 (little impact) n= 22; CAT 11-20 (moderate impact) n=20; CAT <20 (large impact) n=17. During 6MST the individuals were instructed to go up and down a single step with a height of 20 centimeters (cm).

RESULTS

Comparing the groups in relation to performance on the 6MST, the number of climbs on the step were significantly higher in the CAT group <10 when compared to the CAT group >20, the variation in HR between rest and peak exercise (∆ HRpeak- rest) was lower in the CAT>20 group compared to the CAT<10 group and the CAT 11- 20 group. We found direct relationships between the number of ascents and descents in the 6MST vs the CAT score (r=0.35, p=0.007); and 6MST vs degree of obstruction of %FEV1 (r-0.46, p=0.002) We verified a linear regression model in which the FEV1 (L) and the CAT score influenced 29% in the performance of the 6MST.

CONCLUSION

The COPD severity represented by the FEV₁ and the CAT score are associated and influenced by 29% the performance of 6-minute step test. Our findings may have important implications for the clinical evaluation of these patients as well as for rehabilitation.

Responsividade do teste do degrau de seis minutos a um programa de treinamento físico em pacientes com DPOC

OBJETIVO: Avaliar a responsividade do teste do degrau de seis minutos (TD6) a um programa de treinamento físico (PTF) aeróbio e verificar a eficácia do PTF quanto às variáveis ergoespirométricas no TD6, assim como ao desempenho físico, sensação de dispneia e SpO2 no TD6 e no teste de caminhada de seis minutos (TC6) em pacientes com DPOC. MÉTODOS: Estudo controlado, prospectivo e randomizado com pacientes com diagnóstico clínico de DPOC que apresentassem relação VEF1/CVF < 70% e condições clinicamente estáveis nos últimos dois meses. Os pacientes foram randomizados em grupo PTF, que realizaram um PTF em esteira por seis semanas, três vezes por semana, e grupo controle. Todos os participantes receberam cuidados usuais de fisioterapia respiratória durante o período de estudo e foram submetidos a anamnese, exame físico, espirometria antes e após o uso de broncodilatador, teste cardiopulmonar incremental sintoma limitado, TD6 e TC6 nos momentos basal e final. RESULTADOS: Dos 36 pacientes que completaram o estudo, 21 e 15 foram distribuídos nos grupos PTF e controle, respectivamente. Verificou-se um aumento significativo do número de subidas no degrau no TD6, da distância percorrida no TC6 (em m e % do previsto), assim como uma redução significativa da sensação de dispneia durante o TC6 somente no grupo PTF. CONCLUSÕES: O TD6 apresentou responsividade ao PTF. No entanto, acreditamos que o TC6 seja mais responsivo ao PTF proposto.

The impact of obesity on walking and cycling performance and response to pulmonary rehabilitation in COPD

BACKGROUND

We examined the influence of overweight and obesity on pulmonary function, exercise tolerance, quality of life and response to pulmonary rehabilitation in COPD.

METHODS

261 patients with COPD were divided into three groups: normal body mass index (BMI), overweight and obese. Baseline and post rehabilitation pulmonary function, 6-min walking test (6MWT), endurance time during a constant workrate exercise test (CET) and St. George's Respiratory Questionnaire (SGRQ) scores were compared between all three classes of BMI.

RESULTS

At baseline, obese and overweight patients had less severe airflow obstruction compared to normal BMI patients. There was no baseline difference in CET performance or SGRQ scores across BMI classes and 6MWT was reduced in the presence of obesity (p < 0.01). Compared to baseline, post-rehabilitation 6MWT, CET performance and SGRQ scores improved significantly in each group (p < 0.01), but 6MWT was still significantly lower in the presence of obesity.

CONCLUSIONS

Walking, but not cycling performance was worse in obese patients. This difference was maintained post rehabilitation despite significant improvements. Weight excess may counterbalance the effect of a better preserved respiratory function in the performance of daily activities such as walking. However, obesity and overweight did not influence the magnitude of improvement after pulmonary rehabilitation.

Respiratory function and the obesity paradox

PURPOSE OF REVIEW

Obese individuals have impaired respiratory function relative to their normal-weight counterparts. Despite these negative effects, obesity is paradoxically associated with better survival in individuals with chronic obstructive pulmonary disease (COPD). The purpose of this review is to describe this 'obesity paradox', to discuss the effects of obesity on respiratory function, and to speculate as to whether obesity-related alterations in respiratory mechanics can influence the natural history of COPD.

RECENT FINDINGS

Given the known negative effects of obesity on respiratory physiology, it is reasonable to predict that obese COPD patients would be more likely to experience greater dyspnea and exercise intolerance relative to COPD patients of normal weight. However, recent evidence suggests that obese COPD patients have similar or better dyspnea scores during exercise and do not have diminished exercise capacity. These observations may be attributable to the fact that obese COPD patients have reduced operating lung volumes and higher inspiratory capacity to total lung capacity ratios than their lean COPD counterparts.

SUMMARY

Obese patients with COPD do not appear to be at a disadvantage during exercise relative to lean COPD patients. Obesity may be associated with improved survival in COPD but specific mechanisms for this paradox remain to be elucidated.

Effect of obesity on constant workrate exercise in hyperinflated men with COPD

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and a high body mass index (BMI) can both affect pulmonary volumes as well as exercise tolerance, but their combined effect on these outcomes is not well known. The aim of this study was to investigate the effects of increased BMI during constant workrate cycle ergometry in patients with COPD.

METHODS

Men with COPD and hyperinflation were divided according to World Health Organization BMI classification: 84 normal BMI (NBMI), 130 overweight (OW) and 64 obese (OB). Patients underwent spirometric and lung volumes assessment and an incremental cycling exercise test. This was followed by a constant workrate exercise test (CET) at 75% of peak capacity. Inspiratory capacity and Borg dyspnea scores were measured at baseline, during and at the end of CET.

RESULTS AND DISCUSSION

FEV1 % predicted was not different across BMI classes. Total lung capacity and functional residual capacity were significantly lower in OB and OW compared to NBMI patients. Peak VO2 in L x min(-1) was significantly higher in OB and OW patients than in NBMI patients. CET time was not different across BMI classes (p = 0.11). Changes in lung volumes and dyspnea during CET were not different between BMI categories.

CONCLUSIONS

OB and OW patients with COPD had a higher peak VO2 than their lean counterparts. Endurance time, dyspnea and changes in lung volumes during CET were similar between BMI categories.

Obesity, adipokines, and lung disease

This review summarizes the state of the current literature relating to the associations of lung disease on obesity and adipokines (proteins produced by adipose tissue) in humans. Obesity is an independent risk factor for asthma. Recent studies suggest that obesity is also an independent risk factor for chronic airflow obstruction, as is seen with chronic obstructive pulmonary disease (COPD). The mechanistic basis for these associations in humans is not established, although a possible role for adipokines has been invoked. Leptin, a proinflammatory adipokine, and adiponectin, an anti-inflammatory adipokine, are causally associated with asthma in mice. Although human studies are currently inconclusive, high-serum leptin and low-serum adiponectin concentrations predict asthma, independent of obesity, in select population groups, such as premenopausal women in the United States. In contradistinction, low-serum leptin and high-serum adiponectin concentrations are associated with stable COPD, although these associations are likely confounded by fat mass. Interestingly, leptin may promote systemic and airway inflammation in stable COPD patients. On the other hand, COPD may upregulate systemic and lung adiponectin expression. The precise mechanism and significance of the associations between these adipokines and lung disease at the current stage is confusing and frankly paradoxical in places. This area of research needs additional study that may open up novel therapeutic strategies for these lung diseases.

Combined effects of obesity and chronic obstructive pulmonary disease on dyspnea and exercise tolerance

RATIONALE

Severity of lung hyperinflation is known to influence the extent of dyspnea and exercise intolerance among patients with chronic obstructive pulmonary disease (COPD) with similar degrees of airway obstruction. Lung volume components are consistently affected by body mass index (BMI) in health and in disease.

OBJECTIVES

To explore the complex interactions between obesity, lung hyperinflation, dyspnea, and exercise performance in COPD.

METHODS

We compared dyspnea intensity ratings and ventilatory responses (breathing pattern, operating lung volumes, and gas exchange) during symptom-limited incremental cycle exercise in well-characterized groups of 18 obese (mean BMI +/- SD, 35 +/- 4 kg/m(2)) and 18 normal-weight (mean BMI +/- SD, 22 +/- 2 kg/m(2)) patients with moderate to severe COPD.

MEASUREMENTS AND MAIN RESULTS

Groups were well matched for FEV(1) (mean 49% predicted) and diffusing capacity (means >70% predicted), but resting lung hyperinflation (end-expiratory lung volume [EELV]) was significantly reduced in association with increasing BMI (P < 0.005). In the obese patients, peak symptom-limited oxygen uptake was increased (P < 0.01) and dyspnea ratings at a standardized ventilation were decreased (P < 0.01) compared with normal-weight patients. Ratings of dyspnea intensity at a standardized ventilation during exercise correlated well with the concurrent dynamic EELV/total lung capacity (TLC) ratio (r = 0.68; P < 0.00001) and with the resting EELV/TLC (r = 0.67; P < 0.00001).

CONCLUSIONS

The combined mechanical effects of obesity and COPD reduced operating lung volumes at rest and throughout exercise with favorable influences on dyspnea perception and peak oxygen uptake during cycle ergometry.

Physiology of obesity and effects on lung function

In obese people, the presence of adipose tissue around the rib cage and abdomen and in the visceral cavity loads the chest wall and reduces functional residual capacity (FRC). The reduction in FRC and in expiratory reserve volume is detectable, even at a modest increase in weight. However, obesity has little direct effect on airway caliber. Spirometric variables decrease in proportion to lung volumes, but are rarely below the normal range, even in the extremely obese, while reductions in expiratory flows and increases in airway resistance are largely normalized by adjusting for lung volumes. Nevertheless, the reduction in FRC has consequences for other aspects of lung function. A low FRC increases the risk of both expiratory flow limitation and airway closure. Marked reductions in expiratory reserve volume may lead to abnormalities in ventilation distribution, with closure of airways in the dependent zones of the lung and ventilation perfusion inequalities. Greater airway closure during tidal breathing is associated with lower arterial oxygen saturation in some subjects, even though lung CO-diffusing capacity is normal or increased in the obese. Bronchoconstriction has the potential to enhance the effects of obesity on airway closure and thus on ventilation distribution. Thus obesity has effects on lung function that can reduce respiratory well-being, even in the absence of specific respiratory disease, and may also exaggerate the effects of existing airway disease.

Nutritional support in advanced lung disease. The pulmonary cachexia syndrome

Patients with advanced lung disease (ALD) demonstrate changes in body composition characteristically manifested by a progressive loss of body weight. The mechanisms of this pulmonary cachexia syndrome are multifactorial, and treatment must be comprehensive in nature. This article addresses our current knowledge regarding the relationship between nutrition and ALD.

Estimation of ventilatory reserve by stair climbing. A study in patients with chronic airflow obstruction

Clinicians and surgeons have used the subjective response to the climb of "one or two flights of stairs" to assess the "reserve" of patients with chronic airflow obstruction (CAO). Very little objective data exist regarding the metabolic and ventilatory cost for any level of stair climbing in these patients. Therefore, this study was designed to evaluate the use of symptom-limited stair climbing as a simple method to estimate the peak oxygen uptake (VO2) and minute ventilation (VE) in patients with CAO. We studied 31 men with varying degrees of CAO, who climbed stairs until they stopped at their symptom-limited maximum. During this climb, timed expired gas was intermittently collected and analyzed, and oxygen saturation and heart and respiratory rates were recorded. The patients achieved 81 +/- 14 percent of their predicted maximal heart rate and 90 +/- 27 percent of their predicted maximal VE. The number of steps or flights climbed correlated linearly with peak VO2 (r = 0.72, p < 0.01) and with VE (r = 0.7, p < 0.01). Stair climbing peak VE, VO2, heart and respiratory rate correlated well with those achieved during standard leg cycle ergometry. The mean +/- SD number of flights climbed was 4.2 +/- 1.7 with most patients (87%) reaching at least 3 flights (54 steps). The group of eight patients with very severe CAO (FEV1 < 0.9 L) climbed 3.4 +/- 0.9 flights (61 +/- 16 steps). We conclude that a symptom-limited maximal stair climb helps estimate peak VO2 and VE in patients with CAO. The frequently advocated test to climb one to two flights to evaluate cardiopulmonary reserve is not adequate for most patients with CAO. Symptom-limited maximal stair climbing is a simple, inexpensive and readily available test that may be used to evaluate the cardiopulmonary reserve of stable patients with CAO.

Body composition and exercise performance in patients with chronic obstructive pulmonary disease

To investigate whether a compromised nutritional state may limit exercise performance in patients with chronic obstructive pulmonary disease we studied 54 such patients (FEV1 less than 50% and arterial oxygen tension (PaO2) greater than 7.3 kPa) whose clinical condition was stable and who were admitted to a pulmonary rehabilitation centre. Fat free mass was assessed anthropometrically (from skinfold measurements at four sites) and by bioelectrical impedance; creatinine height index and arm muscle circumference were also assessed. The mean (SD) distance walked in 12 minutes was 845 (178) m. No association was established between the distance walked and spirometric measures. A good correlation was found between the distance walked and fat free mass in the whole group (r = 0.73 for impedance measurements and 0.65 for skinfold thickness) and in a subgroup of 23 lean patients (body weight less than 90% of ideal weight; r = 0.66 for impedance measurements and 0.46 for skinfold thickness). Body weight correlated with the distance walked only in the whole group (r = 0.61). On stepwise regression analysis fat free mass measured by bioelectrical impedance, maximal inspiratory mouth pressure, and PaO2 accounted for 60% of the variation in the distance walked in 12 minutes. We conclude that fat free mass, independently of airflow obstruction, is an important determinant of exercise performance in patients with severe chronic obstructive pulmonary disease.