Daily Physical Activity After A Lung Volume Reduction Biology Essay
In an experimental study, the effect and safety of Lung Volume Reduction-coils insertion in severe emphysema patients is investigated. The procedure is assumed to block the weak parts of the long, so the more healthy parts of the lung could expand to work more effective.
Objectives: The purpose of this study was to investigate the short-term effects of a LVR-coil insertion on daily physical activity measured in a performance based way.
Methods: After admission to the LVR-coil study, patients were asked to participate in this movement analysis study, in a pre-experimental design. The primary outcome was daily physical activity assessed by a DynaPort MoveMonitor. Daily physical activities were examined during a 1-week measurement period, before and after the LVR-coil procedure. Secondary outcomes were exercise capacity, pulmonary function and psychological factors (motivation to exercise and self efficacy).
Results: No statistically significant differences were found in daily physical activity level, in contrast to improvements in exercise capacity, the degree of hyperinflation and psychological factors. High effect sizes were found for 6MWT (-0.635, p=0.028), RV/TLC (-0.635, p=0.028) and SRQ-E (-0.529, p=0.080).
Conclusion: This study showed that the LVR-coil procedure in severe emphysema patients does not improve daily physical activity after 4 weeks, in contrast to high effect sizes in exercise capacity, the degree of hyperinflation and psychological factors.
The World Health Organisation (WHO) lists chronic obstructive pulmonary disease (COPD) as the third leading cause of death in the world,(1) and unfortunately the prevalence of COPD is still increasing.(2) It mainly affects middle-aged and elderly people, who generally have smoked more than 10 pack years. COPD is characterised by progressive airflow limitation which is not fully reversible.(3) Chronic bronchitis and emphysema are two classical phenotypes of COPD that may occur together or apart.(3) This study will focus on severe emphysema patients. The diagnosis of emphysema is based on an anatomical definition: abnormal permanent enlargement of the air spaces distal to the terminal bronchioles which is accompanied by destruction of the bronchioles walls, without obvious fibrosis.(3;4)
During the natural course of COPD and particularly emphysema, physical activities may become increasingly limited and patients may become dyspnoeic with minor exertion or even at rest.(5) Unfortunately, emphysema patients end up in a cycle of decline. Physical inactivity leads to deconditioning, which can be defined as the premature accumulation of lactate at low work rates.(6) The efflux of lactate from deconditioned muscles necessitates bicarbonate buffering, and the generation of the carbon dioxide necessitates an increase in the ventilatory requirements. The increase in ventilatory requirements leads to hyperinflation and air trapping, which worsens dyspnoea and reduces the exercise tolerance, leading to more physical inactivity.(6) Regular exercise has been shown to reduce shortness of breath, the most disabling symptom experienced in emphysema patients.(7)
The major therapeutic modalities consist of inhaled bronchodilators to decrease airway resistance, anti-inflammatory drugs to prevent and treat exacerbations and antibiotics to treat infections.(5) Furthermore, supplemental oxygen or stop smoking could also benefit and increase quality of life, however the disease cannot be cured.
The finding that many emphysema patients have portions of lung which are more affected than others, led to the development of lung volume reduction surgery (LVRS), a procedure which removes approximately 20-35% of the poorly functioning lung space.(8) By reducing the lung size, the remaining lung and surrounding muscles are able to work more efficiently. The removal of diseased and functionless lung may particularly improve the function of the remaining lung by decreasing the degree of hyperinflation. A decrease in the degree of hyperinflation leads to improvements in dyspnoea during effort, ventilatory capacity of the lung and functional capacity of the body.(8) The surgery requires general anaesthesia and can be done through either a breast bone incision or a smaller chest incision using video surgery. LVRS has been described in a large number of emphysema studies. Overall, studies have found substantial and clinically relevant improvements in lung function, walking distance and quality of life. (9) However, LVRS is also associated with disadvantages: the high costs and great risks of the surgery. There are many millions of potential candidates, so a more efficient and less invasive procedure is required.
In an experimental study, the effect and safety of 'Lung Volume Reduction-coils' (LVR-coils) insertion through bronchoscopy is investigated. Like the LVRS, the experimental LVR-coil procedure is assumed to block the weak parts of the lung, so the more healthy parts of the lung could expand to work more effective. An advantage of this experimental study in comparison to the traditional LVRS, is the absence of surgery. Therefore, patients may leave the hospital the next day; leading to reduced admission time in the hospital and lower costs.
We hypothesize that the LVR-coil procedure is gradually leading to an increased daily physical activity, as a result of a decrease in hyperinflation, higher exercise capacity, higher self efficacy with respect to physical ability, and a higher level of motivation to exercise. Before long-term effects of this method can be measured, first short-term effects must be exposed. Therefore, the purpose of this study was to investigate the short-term effects of a LVR-coil insertion on daily physical activity measured in a performance based way, and secondary those improvements were compared to improvements in pulmonary function, exercise capacity and psychological factors.
The study population consisted of 13 severe lung emphysema patients, who participated in the experimental LVR-coil procedure. Eligibility criteria are summarized in table 1.
Table 1 Inclusion and exclusion criteria for a LVR-coil procedure
- Patient ≥ 35 years of age.
- CT scan indicates bilateral heterogeneous and homogeneous emphysema.
- Post-bronchodilator FEV1a ≤ 45% predicted.
- RVc>175% predicted.
- Dyspnoea scoring ≥ 2 on the MRC-scaledof 0-4.
- Stopped smoking for a minimum of 8 weeks prior to entering the study.
- Change of FEV1a>20% post-bronchodilator.
- DLCOe<20% predicted.
- History of recurrent clinically significant respiratory infection.
- Uncontrolled hypertension defined by right ventricular pressure >50 mmHg and or evidenced by echocardiogram.
- Inability to walk >140 meters (150 yards) in 6 minutes.
- Evidence of other disease that may compromise survival.
- Pregnant or lactating.
- Inability to tolerate bronchoscopy under moderate sedation or anaesthesia.
- Clinically significant bronchiectasis.
- Giant bullae >1/3 lung volume.
- Previous LVRSf, lung transplant or lobectomy.
- Involvement in other pulmonary drug studies with 30 days prior to this study.
- >20mg Prednisone (or similar steroid) daily.
- Patient is on an antiplatelet agent (such as Plavix) or anticoagulant therapy (such as Heparin or Coumadin) or has not been weaned off prior to procedure.
- Other diseases that would interfere with completion of the study, follow up assessments or that would adversely affect outcomes.
- Severe homogeneous emphysema by CT-scan.
Note: a. FEV1 = forced expiratory volume in 1 second.
b. TLC = total lung capactity.
c. RV = residual volume.
d. MRC-scale = medical research counsel-scale, for grading the degree of a patient's breathlessness.(11)
e. DLCO = diffusing capacity of the lung for carbon monoxide.
f. LVRS = lung volume reduction surgery.
2.2 Study design
Patients, included for a LVR-coil procedure were recruited by means of their treating pulmonologists in The Netherlands. After admission to the LVR-coil study, patients were asked to participate in this movement analysis study, in a pre-experimental design.
Before the LVR-coil procedure (baseline)daily physical activities were examined with a DynaPort MoveMonitor during a 1-week measurement period. Patients were instructed to wear the DynaPort MoveMonitor for one week, except during showering and swimming. Moreover, two questionnaires, the LIVAS and SRQ-E were asked to be accomplished.
The LVR-coil procedure consists of two interventions; the LVR-coils are inserted to one lung at a time. LVR-coils are delivered in airways using a bronchoscope in a simple procedure, under conscious sedation or general anaesthesia, using a proprietary delivery system. First, the airway in the selected segment is identified and a low stiffness guidewire is advanced into the airway under fluoroscopic guidance.(10) A catheter is passed over the guidewire and radioopaque markers on the guidewire are used to measure the length of the airway. After removing the guidewire, a straightened LVR-coil is introduced into the distal end of the catheter with a grasper under fluoroscopic guidance. Next, the catheter is removed and the proximal end of the LVR-coil is held in place. As the catheter is pulled back, the coil recovers to a preformed shape that bends the airway and causes local compression of the parenchyma. Commonly, 3-6 coils are placed in a damaged lobe, which takes about 45 minutes.(10) The procedure was well tolerated and feasible in all patients. Between the two interventions, one month recovery period was allocated.
The follow-up measurement was examined four weeks after the LVR-coils insertion to the second lung. Patients were again instructed to wear the DynaPort MoveMonitor for one week and the two questionnaires, the LIVAS and SRQ-E were asked to be accomplished. These instructions were given during a control visit of the LVR-coil study, in which also the 6-minute walk test (6MWT) was performed and the pulmonary function measures were obtained.
2.3 Outcome measures
Daily physical activities
Daily physical activities were measured with the DynaPort MiniMod MoveMonitor (Mc Roberts, The Hague, The Netherlands). The DynaPort MoveMonitor (size: 92 x 61 x 9 mm, weight: 53 gram) is fixed with a neoprene strap near the body's centre of mass.(12) The DynaPort MoveMonitor is used to detect postures (lying, sitting and standing), locomotion (shuffling and walking) and transitions, and to estimate physical activity level (PAL). PAL is calculated as total energy expenditure (TEE) divided by resting energy expenditure (REE).(13) The DynaPort MoveMonitor is proved to be an accurate instrument to provide complementary information on habitual physical activity in COPD patients.(14) The measurement duration is limited to 72 hours by internal energy supply, this can be extended to a 1-week measurement period by connecting an external battery (74 x 46 x 11 mm, weight: 30 gram) to the main device by a wire. A 1GB SD-card was used to store data for one week and MIRA 2 software was used for SD-card preparation, reading and data storage. The DynaPort web server analysed the data. The DynaPort MiniMod MoveMonitor has a sensitivity ranged between 63.5%(standing) and 99.3%(lying) and a specificity ranged between 91.6%(sitting) and 99.7%(locomotion).(15) The ICC for intra- and inter-instrumental reproducibility was found to be 0.99 in both posterior-anterior and caudal-cranial directions.(16) The intra-observer reproducibility was also good (ICC = 0.97). Compared to the intra-observer reproducibility, the inter-observer reproducibility was lower (ICC = 0.88), but still good.(16)
Pulmonary function testing
Pulmonary function was measured using a spirometer (Jaeger MS-IOS) and a bodyplethysmograph according to standardized guidelines.(17;18) Outcome measures were: forced expiratory volume in 1 second (FEV1), rest volume (RV), total lung capacity (TLC), (FEV1)/forced vital capacity (FVC) and RV/TLC. RV/TLC is used as a measure for the degree of hyperinflation.
To measure exercise capacity, patients performed the 6-minute walk test (6MWT), they ought to be able to walk at least 140 meters in 6 minutes. This test is widely accepted as a test of functional exercise capacity in COPD patients. The 6MWT has a good reliability and a good criterion validity compared with the golden standard of maximal exercise testing in this population.(19;20)
Psychological factors (self efficacy and motivation to exercise)
Self efficacy with respect to physical ability was measured with the LIVAS, which is a Dutch version of the Perceived Physical Ability Subscale of Physical Self-Efficacy Scale (reliability: Cronbach's α 0.70).(21) Research has shown that self-efficacy is associated consistently with physical activity.(21)
The level of motivation to exercise was measured using the Self-Regulation Questionnaire for Exercise (SRQ-E).(22) Responses of the SRQ-E represent intrinsic motivation, identified regulation, introjected regulation and external regulation.
The long term effectiveness of exercise requires adherence to exercise interventions.(7) Adherence to exercise is poor in individuals with emphysema. It depends on one's ability to self-regulate and persist despite potential difficulties.(7)
2.4 Data analysis
Statistical analysis was performed with the Scientific Package of Social Sciences (SPSS), version 16.0. Medians and ranges were calculated for descriptive characteristics at baseline and outcome measures. The outcome measures of daily physical activity were percentage of time lying, sitting, standing, walking and shuffling, mean steps per day, physical activity level (PAL) and mean walking time per day.(13) The outcome measures for pulmonary function were forced expiratory volume in 1 second (FEV1), rest volume (RV), total lung capacity (TLC), FEV1/ forced vital capacity (FVC) and RV/TLC. The outcome measure for exercise capacity was the 6-minute walk test (6MWT), and the outcome measures of psychological factors were the total score on the LIVAS and the RAI-score on the SRQ-E. (22) The Wilcoxon signed rank test was used to test for significant differences between baseline and follow up measurements. Effect sizes were calculated to facilitate the interpretation of results. An effect size of 0.1 is regarded as a small effect, 0.3 as a medium effect and 0.5 as a large effect.(23) Spearman's correlation coefficient was used to determine the relation between changes in daily physical activity and improvements in pulmonary function, exercise capacity and psychological factors.
Thirteen patients agreed to participate in this study. In seven patients it was not possible to obtain follow-up data, because of exacerbations. Descriptive characteristics at baseline are shown in table 2. There were no significant differences in descriptive characteristics between the selected population and the end population at baseline.
Table 2 Characteristics of the study population at baseline with and without drop-outs.
With drop-outs (n=13) Without drop-outs (n=6)
FEV1 (% pred)e
TLC (% pred)f
RV (% pred)g
Note: a. Body mass index.
b. Packs smoked per day * years as a smoker.
c. Medical research counsel-scale, for grading the degree of a patient's breathlessness.
d. 6-minute walk distance.
e. Forced expiratory volume in 1 second.
f. Total lung capacity.
g. Rest volume.
h. Lower scores indicate more obstruction.
i. Higher scores indicate more air trapping.
j. Dutch version of the Perceived Physical Ability Subscale of Physical Self-Efficacy Scale.
k. Self-Regulation Questionnaire for Exercise, the relative autonomy index (RAI), higher scores indicate more intrinsic motivation.
3.1 Daily physical activity
As shown in table 3 and figure 1A t/m 1C, there were no great differences in postures and locomotion times between baseline and follow-up data. The PAL and steps per day even showed a small decrease in follow-up compared to baseline.
The effect size was medium (>0.3) for percentage of time standing. For percentage of the time lying, sitting and shuffling effect sizes were small (>0.1). Effect sizes were very small for percentage of the time walking, PAL and steps/day.
Table 3 Effects of the LVR-coil procedure on main outcome variables.
a. Physical Activity Level.
b. 6-minute walk distance.
c. Forced expiratory volume in 1 second.
d. Total lung capacity.
e. Rest volume.
f. Lower scores indicate more obstruction..
g. Higher scores indicate more air tapping.
h. Dutch version of the Perceived Physical Ability Subscale of Physical Self-Efficacy Scale.
i. Self-Regulation Questionnaire for Exercise.
* p < 0.05 (Wilcoxon signed rank test).
As shown in figure 1A, PAL showed a variable pattern; some subjects decreased and some subjects increased their physical activity level. The median is constant between baseline and follow-up. Figure 1B also shows a variable pattern, with a small decrease in the median of steps per day. Remarkable is the great decrease in steps per day and walking time for 1 subject (Figure 1C). As shown in figure 1C, walking time per day also showed a variable pattern and the median is constant between baseline and follow-up.
3.2 Lung function measures
As shown in table 3, FEV1 increased and TLC and RV decreased after the LVR-coil procedure. FEV1/FVC indicated a very small decrease and RV/TLC indicated a large decrease in the follow up measurement. Effect sizes were large (>0.5) for RV and RV/TLC, and medium (>0.3) for FEV1, TLC and FEV1/FVC. Figure 1D describes the changes in FEV1 per subject. The median showed a small increase in FEV1. Figure 1E describes the changes in RV, all subjects developed a decrease in RV.
3.3 Exercise capacity
Table 3 showed there was a great increase in 6-minute walking distance. Effect sizes were large (>0.5) for the 6MWT. This increase is also demonstrated in figure 1F; all subjects showed an increase in walking distance on the 6MWT.
Figure 1 Baseline and follow-up data of daily physical activity, pulmonary function, exercise capacity and psychological factors, the red dots describe the median.
3.4 Psychological factors
Table 3 showed that both the LIVAS and the SRQ-E increased after the LVR-coil insertion. Effect sizes were large (>0.5) for SRQ-E and medium (>0.3) for the LIVAS. As shown in figure 1G, every subject, except 1 increased their score on the SRQ-E. Figure 1H showed the LIVAS scoring has a more variable change between baseline and follow up. The median showed a small increase.
3.5 Changes in daily physical activity compared to changes in pulmonary function measures, exercise capacity and psychological factors.
As shown in table 4, differences in daily physical activity measures were related to each other; as expected walking time is significantly related to steps/day (p<0.01) and PAL (p<0.01), and PAL is also significantly related to steps/day (p<0.01). Differences in pulmonary function were also related; TLC is significantly related to RV (p<0.05).
Table 4 showed no significant correlations between change in daily physical activity and change in exercise capacity, neither significant correlations between change in daily physical activity and change in lung function measures.
Changes in psychological factors were related to change in daily physical activity and lung function measures; SRQ-E is significantly related to PAL (p<0.05) and FEV1 (p<0.01), and the LIVAS is significantly related to TLC (p<0.05).
Figure 2 showed the relation between changes in PAL and changes in SRQ-E; if a subject increased their physical activity level, the RAI-score on the SRQ-E also increased.
Figure 2 Changes in PAL related to changes in SRQ-E.
Table 4 Correlation between changes in important outcome variables.
Note: a. Physical activity level.
b. Walking time per day in minutes.
c. 6-minute walk test.
d. Forced expiratory volume in 1 second.
e. Total lung capacity.
f. Rest volume.
g. Dutch version of the Perceived Physical Ability Subscale of Physical Self-Efficacy Scale
h. Self-Regulation Questionnaire for Exercise.
* p<0.05 (Spearman's correlation coefficient).
** p<0.01 (Spearman's correlation coefficient).
The aim of this study was to investigate the short-term effects of a LVR-coil procedure on daily physical activity measured in a performance based way. Secondary effects of the LVR-coil procedure, effects on pulmonary function, exercise capacity and psychological factors (self efficacy and motivation to exercise) were also analysed.
No great differences were found in postures and locomotion times between baseline and follow-up. Unexpectedly PAL and steps/day even showed a small decrease. An explanation for the absence of great improvements in daily physical activity measures could be the short time interval between LVR-coils insertion and the measurement period.
The great number of drop-outs is also related to the short time period between the LVR-coil procedure and the follow-up measurement. It is well-known that severe emphysema patients form a difficult study population to measure accurately due to their great possibility to drop out, as an exacerbation is very common in this group. Moreover, negative effects of the bronchoscopic manipulations worsen temporary the health status of a patient, and even can cause exacerbations, which made it sometimes impossible to obtain follow-up data after 4 weeks. To better assess the negative effects of the LVR-coil procedure, future trials need an independent and unbiased assessment.(10) However, most subjects were still recovering from their hospitalization and they sometimes had an exacerbation right before the follow-up measurement. It is provided that the occurrence of an exacerbation in COPD patients could reduce the time spent in weight-bearing activities (walking and standing).(24) Because of drop-out reasons, an intention to treat analysis was not performed.
The number of steps per day in the study population was far beneath the number of steps per day that Tudor-Locke and Myers suggested for older adults and those living with a chronic disease could take (3500-5500 steps per day).(25) Compared with other moderate to severe COPD patients (3700 steps per day) daily physical activity in LVR-coil patients was much lower (2217 steps per day).(26) These comparisons indicate the low physical activity level in this study sample, which possibly made them more susceptible to exacerbations and other health problems.
In contrast to the daily physical activity outcome measures, some great improvements were found in pulmonary function. Interesting are the increased FEV1, an important diagnostic measurement of COPD, and the significantly decreased RV. The increased FEV1 could be interpreted as an improvement in the degree of obstruction and the decrease in RV could be interpreted as an improvement in the degree of air trapping. Improvements in these lung function measures will be associated with a decrease in the degree of hyperinflation. The same reduction as found in this study, decreased RV and TLC, were also found in lung volume reduction surgery.(6)
The improvements in pulmonary function correspond with the improvements in exercise capacity. All subjects increased their 6 minute walking distance at follow-up, compared to baseline. An improvement of 25 m has been investigated as the least change in 6MWT that results in a minimal important difference (MID), the smallest difference in the outcome score of interest that informed patients or proxies perceive as important.(27) The median difference of 74 m was thus significantly higher than this minimal important clinical difference. The past LVRS studies also showed significant improvements in exercise capacity in terms of 6MWT, but these improvements were less convincing; LVRS patients have been reported to increase the 6MWT by a mean of 55 m.(28;29)
In a study of Belza et al. daily physical activity measured with an accelerometer, was strongly associated with maximal distance walked during the 6MWT, level of airway obstruction and walking self efficacy.(30) Concluding from the improvements in pulmonary function and exercise capacity, patients should be able to improve their daily physical activity pattern. One possible explanation for the absence of great improvements could be that their behaviour is still modified to avoid dyspnoea.(6) However, some interesting changes in self efficacy and motivation to exercise were found. The LIVAS has shown some small improvements and moreover the SRQ-E score significantly improved. Self efficacy is a relevant and promising determinant of behaviour change related to the process of becoming physically active.(21) The basic issue of the SRQ-E concerns the degree to which one feels autonomous with respect to engaging in physical activities.(26) The results of this study assume that LVR-coil patients are highly motivated to be physically active after the LVR-coil procedure, therefore improvements in daily physical activity would be expected. The significant correlation found between PAL and SRQ-E(p < 0.05) is therefore as expected, although the small sample size possibly influenced this correlation.
Another possible explanation for the absence of great improvements can be found in the disadvantage of the DynaPort MoveMonitor to measure non-ambulatory activities (e.g. cycling and swimming). Nevertheless, walking is one of the most common forms of activity.(31)
Finally, another possible factor is the influence of weather; it appears that levels of physical activity vary with seasonality, and the ensuing effect of extreme or poor weather has been identified as a barrier to participate in physical activities among various populations.(32;33) The effect of weather was also analysed in this study population (data not shown). One patient, who's follow up data was obtained in extreme heat showed a great decrease in daily physical activity. The differences in weather between baseline and follow-up measurement could possibly be an explanation to the absence of improvements in daily physical activities.
The strength of this study was that objective data of both physical activity (accelerometer-determined steps/day, PAL and walking time), pulmonary function (spirometry-determined RV, TLC, FVC and FEV1) and exercise capacity (6MWT) were utilized.
Limitations of this study were the small sample size and the absence of a control group. This may account for the many non-significant results. Obviously, we were not allowed to change the protocol of this METc-approved study. Another important limitation of this study, is the short term (4 weeks) follow-up period. This period may have been too short to lose the negative effects of the bronchoscopic manipulations, and too short to translate improved hyperinflation and exercise capacity into daily physical activity. However the present study is ongoing and we have to await longer follow-up measurements. If long-term physical activity is not improved in contrast to hyperinflation and exercise capacity, a structured rehab program may be considered as a routine follow-up for this LVR-coil procedure.
This pre-experimental study demonstrates that the LVR-coil procedure in severe emphysema patients does not improve daily physical activity in contrast to signs of improvements in exercise capacity, the degree of hyperinflation and psychological factors. Later follow-up data may demonstrate a delayed improvement on physical activity.
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