versión impresa ISSN 1807-5932
Clinics v.62 n.2 São Paulo 2007
The impact of noninvasive ventilation during the physical training in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD)
O impacto da ventilação não-invasiva no treinamento físico em pacientes com doença pulmonar obstrutiva crônica moderada a grave
Andreza Toledo; Audrey Borghi-Silva; Luciana Maria Malosá Sampaio; Karla Paiva Ribeiro; Vilmar Baldissera; Dirceu Costa
Federal University of São Carlos - São Carlos/SP, Brazil. Email: firstname.lastname@example.org
OBJECTIVE: To evaluate the influence of physical training with or without noninvasive ventilation at 2 levels of pressure in the airways (BiPAP®) in patients with chronic obstructive pulmonary disease.
METHODS: Eighteen patients with FEV1 = 34 ± 8% of predicted values, mean age of 68 ± 9 years were randomly distributed into 2 groups, one group performing physical training on a treadmill and the other group performing physical training associated with BiPAP® (physical training+B), for 30 minutes, 3 times a week for 12 weeks. The training velocity was based on a test of cardiopulmonary force performed pre- and postintervention, which registered the values for heart rate, systolic blood pressure, diastolic blood pressure, peripheral oxygen saturation, blood lactate, sensation of dyspnea, respiratory muscle strength, and analysis of gases expired such as oxygen consumption and the production of carbon dioxide.
RESULTS: For both groups, there was a significant improvement in dyspnea and peripheral oxygen saturation at identical levels of physical exercise, in distance walked during the physical training, and in respiratory muscle strength (P < 0.05). Only the physical training+B group had a significant improvement in heart rate, systolic blood pressure, and oxygen consumption after training (P < 0.05). Significant reductions of blood lactate were observed at identical levels of exercise in physical training+B when compared to isolated physical training (from 1.3 ± 0.7 mMol/L versus 2.5 ± 0.9 mMol/L, (P < 0.05), respectively).
CONCLUSION: Physical training associated with BiPAP® enhanced the oxidative muscular capacity and could be an adjunctive recourse for physical rehabilitation in patients with chronic obstructive pulmonary disease.
KEYWORDS: Chronic obstructive pulmonary disease (COPD). Physical training. BiPAP®. Noninvasive ventilation. Cardiopulmonary test.
OBJETIVO: Avaliar a influência do treinamento físico, com e sem ventilação não invasiva com dois níveis de pressão nas vias aéreas (BiPAP®), em pacientes com doença pulmonar obstrutiva crônica.
MÉTODOS: Dezoito pacientes com VEF1=34±8% do previsto, idade média de 68±9 anos, foram randomicamente distribuídos em dois grupos, um grupo realizando treinamento físico em esteira e outro grupo realizando treinamento físico associado ao BiPAP® (treinamento físico+B), durante 30 minutos, 3 vezes por semana, por 12 semanas. A velocidade do treinamento foi baseada no teste cardiopulmonar realizado pré e pós-intervenção, com registro dos valores de freqüência cardíaca, pressão arterial sistólica, pressão arterial diastólica, saturação periférica de oxigênio, lactato sanguíneo, sensação de dispnéia, força muscular respiratória e análise de gases expirados como consumo de oxigênio, produção de dióxido de carbono.
RESULTADOS: Em ambos os grupos houve melhora significativa na dispnéia e saturação periférica de oxigênio no mesmo nível de esforço, na distância percorrida no teste cardiopulmonar e na força muscular respiratória (p<0,05). Somente o grupo treinamento físico+B teve melhora significativa de freqüência cardíaca, pressão arterial sistólica e consumo de oxigênio após treinamento (p<0,05). Além disso, significativa redução do lactato sanguíneo foi observada para o mesmo nível de exercício no grupo treinamento físico+B quando comparado com treinamento físico isolado (1,3±0,7 e 2,5±0,9mMol/L, p<0,05, respectivamente).
CONCLUSÃO: O treinamento físico associado com BiPAP® aumenta a capacidade muscular oxidativa, e pode ser um recurso coadjuvante da reabilitação física de pacientes com doença pulmonar obstrutiva crônica.
UNITERMOS: Doença pulmonar obstrutiva crônica (DPOC). Treinamento físico. BiPAP®. Ventilação não invasiva. Teste cardiopulmonar.
Patients with chronic obstructive pulmonary disease (COPD) present a greater limitation in physical exercise due to dyspnea.1-3 Increased airway resistance, insufficient ventilation, hyperinsuflation, respiratory muscle mechanical disability, and gas exchange abnormalities associated with the symptoms of dyspnea contribute to the ventilatory limitation during effort in these patients.1,4,5
Physical training, in general, has the objective of improving the efficiency of the capacity of the uptake system, transport, and metabolism of oxygen6 and is essential in the treatment of patients with COPD, as its objective is to improve tolerance for physical exercise, respiratory muscle effort, and endurance as well as reduce the symptoms of dyspnea.7-11
According to Bourjeily & Rochester,12 physical training should have a duration of 6 to 12 weeks at a frequency of 3 times per week. Some studies have demonstrated that 6 weeks of physical training can provide an increased functional capacity for these patients,7,9,13 although the short period of physical training may be a limiting factor12 for serious cases. In patients with greater functional limitations, the use of noninvasive ventilation (NIV) at 2 pressure levels (BiPAP®) used as an adjunct to physical training has been studied in patients with COPD. It is believed that positive pressure is available during the auxiliary inspiratory phase of ventilation in the patient and reduces the work of the respiratory musculature, diminishing the intrinsic positive end expiratory pressure (PEEPi) through the constant application of expiratory support.14-17
Costes et al18 conducted a physical training program using an ergometric bicycle for 8 weeks associated with NIV (BiPAP®) and observed a significant increase in the oxygen consumption (VO2) compared to physical training alone. However, Bianchi et al19 did not find additional effects from proportional assisted ventilation support when associated with a physical training program for patients with COPD.
We hypothesized that physical training on a treadmill with BiPAP compared to physical training without BiPAP would improve the respiratory variables in moderate/severe COPD.
MATERIALS AND METHODS
Eighteen individuals of both sexes were referred to the Respiratory Physical Therapy Service at the Federal University of São Carlos (UFSCar) between February and December 2004 by medical prescription with a clinical and spirometric diagnosis of COPD. The patients underwent a general evaluation and specific respiratory system testing of pulmonary function (spirometry) using a portable spirometer (Vitalograph, Hand Held 2021) in an acclimatized room (22ºC to 24ºC). The technical procedures, criteria of acceptability, and reproducibility were performed according to specifications adopted by the American Thoracic Society.20 The reference values of Knudson et al21 were used.
The criteria for inclusion in the study were the following: Patients should present a forced expiratory volume on first second (FEV1) < 60% and FEV1/FVC < 70% of the predicted20 as well as should be clinically stable for a minimum period of 6 months and present no associated cardiovascular diseases, orthopedic diseases, reactive hypertension relative to effort, nor neuromuscular disorders that would impede the performance of the experimental procedures in this study.
After having the objectives and procedures that would be performed explained to them, patients signed a Term of Consent for participation in the proposed program in accordance with the recommendations of Resolution 196/96 of the National Health Council of Brazil. This study was approved by the Committee for Ethical Research on Human Beings of the institution.
Before and after the treatment, patients underwent the following evaluations:
Respiratory Muscle Strength. Respiratory muscle strength was obtained using an analogic manovacumeter with a cm H2O scale, (Ger-ar; SP, Brasil). Maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax) were measured according to the method described by Black and Hyatt,22 in which the individual uses a nose clip while remaining in an orthostatic position. PImax was measured from residual volume after maximum expiration, and PEmax was measured close to total pulmonary capacity, after maximum inspiration. The individuals were instructed to maintain pressure for more than 1 second, and each maneuver was performed a minimum of 3 times, with the highest value used for the analysis.23
Cardiopulmonary Physical Testing (CPT). Cardiopulmonary physical testing (CPT) was carried out on an Inbramed Milenium treadmill model ATL (RS, Brazil) using an increasing speed protocol, beginning at 2 km/h, for 2 minutes, with increments of 0.5 km/h at every 2 minutes. Continuous monitoring was done throughout the test using a Nonin 8400A pulse oximeter (Plymouth, USA) for peripheral oxygen saturation (SpO2), heart rate (HR) using a frequencymeter (Polar Precision Performance, Kemple, Finland), and an electrocardiogram monitor using an Ecafix TC 500 (SP, Brazil). Also were recorded were the SpO2, HR, and sensation of dyspnea using a Borg CR10 modified scale.24 The systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured on the left upper arm using an sphygmomanometer by indirect method. Blood samples were collected from the earlobe for blood lactate analysis. Blood lactate was measured at rest and every 2 minutes during the test.The interruption criteria for CPT were an intense sensation of dyspnea, arrhythmia, increase in HR above the maximum predicted for the age of the individual, or drops in SpO2 < 80%.
Blood Lactate Dosage after aseptic cleaning of the region with alcohol; a puncture in the earlobe was made with a disposable lancet. The first drop of blood was discarded to avoid contamination by lactate eliminated through sweat. Each arterial blood sample was collected in a capillary tube previously treated with 25 ml of heparin. The blood was deposited into 2 mL Eppendorf tubes containing 50 ml of 1% sodium fluoride as a glycolysis preservative. The blood was stored at -10ºC for later analysis. Blood lactate concentration was performed using a portable electrochemical lactometer (YSI model 1500 Sport lactometer, Yellow Springs Inc. USA) using the electro-enzymatic method.
Analysis of Expired Gas. Analysis of expired gas was performed using a metabolic system (MedGraphis Model VO2000, St Paul MN, USA), operated by microcomputer (Pentium II) using Aerograph software for capture and storage of signals. The VO2000 measured microsamples of expired gas at the rate of 20 in 20 seconds, and the metabolic data generated were plotted in graphs and tables. The variables analyzed were VO2 (L/min) and VCO2 (L/min), expressed at standard temperature and pressure dry (STPD).
Treatments. The patients were divided randomly into 2 groups, one undergoing physical training on a treadmill (PT) and the second undergoing PT associated with the use of bi-level NIV (PT+B), using a BiPAP® (S-Respironics Inc., Pennsylvania-USA). Through a nasal mask, inspiratory pressure levels (IPAP) between 10 and 15 cm H2O and expiratory pressure levels (EPAP) between 4 and 6 cm H2O were applied to the airways, adjusted in accordance with the tolerance and comfort reported by each patient. The inspiratory level was set at 5 cm H2O and was increased gradually by 2 cm H2O every minute to a maximum of 15 cm H2O. Expiratory pressure was set at 3 cm H2O and was increased gradually by 1 cm H2O every minute to a maximum of 6 cm H2O. The gradual increase in both the inspiratory and expiratory pressures was aimed at increasing comfort and compliance in volunteers. These values were set in an arbitrary manner and designed to provide what would be considered by most patients as mild expiratory pressure and moderate inspiratory pressure support.
For both groups, the protocol was administered in 30-minute sessions, 3 days a week on alternate days, for 12 weeks. The intensity of the applied training corresponded to 70% of the maximum speed reached by each patient at the pretreatment CPT.
Statistical Analysis. Due to the non-normal distribution of the data, the Wilcoxon and Mann Whitney nonparametric tests were used for intragroup and intergroup comparisons, respectively, with the level of significance set at level of significance of P d" 0.05.
The anthropometric and demographic characteristics of the study population are presented in Table 1. All patients had moderate to severe COPD, as evidenced by reduced forced expiratory volume in 1 second (FEV1), and force vital capacity (FVC) in both groups. No significant differences were found between the groups, characterizing the homogeneity of the sample.
Regarding cardiopulmonary variables (HR, SBP, DBP), SpO2, sensation of dyspnea and blood lactate pre-and posttreatment, for both the PT and the PT+B group, there was a significant increase of SpO2 (85% ± 8% to 89% ± 8% and 81% ± 4% to 87% ± 4%; respectively) and decrease of dyspnea (4.2 ± 2.1 to 1.4 ± 1.4 and 4.0 ± 1.5 to 1.5 ± 1.8, respectively) (Table 2). However, the HR (110.7 ± 15.2 to 103.7 ± 11.5 bpm), SBP (164.4 ± 22.9 to 140.0 ± 21.9 mm Hg), and blood lactate (1.7 ± 0.7 to 1.3 ± 0.7mMol/L) were significantly reduced only for the PT+B group. In the posttreatment evaluation, lower values of blood lactate were obtained in the PT+B group when compared PT alone (2.5 ± 0.9 versus 1.3 ± 0.7 mMol/L). Neither of the groups studied presented any significant alterations for DBP.
Regarding values for peak physical exercise, the intra- and intergroup analysis did not reveal significant alterations in variables for HR, SBP, DBP, SpO2, sensation of dyspnea, blood lactates, or VCO2 (Table 3). However, intragroup analysis revealed a significant increase in VO2 only in the PT+B group (0.9 ± 0.3 to 1.3 ± 0.3 L/min). A significant increase in respiratory muscle strength was found for both groups (Figure 1).
Regarding the walking distance in CPT, a statistically significant increase occurred in both groups (Figure 2).
Our main findings in this study regarding intragroup analysis at identical levels of physical exercise in CPT were: 1) a significant increase of SPO2 and a decrease of the sensation of dyspnea in both groups; 2) significant reductions of HR, SBP, and blood lactate only in the PT+B group; and 3) a significant reduction of blood lactate in the PT+B group when compared to PT alone. Regarding the peak values in CPT, the intragroup analysis showed a significant increase in oxygen consumption only for the PT+B group.
In our study, both the group undergoing PT alone and the group undergoing PT+ BiPAP® presented significant improvements in SpO2, sensation of dyspnea, respiratory muscle strength, and the distance walked in CPT. The results of the present study are in accordance with those obtained by other authors,11,25,26 who observed an increase in respiratory muscle strength, improvement in physical capacity, and a reduction in dyspnea in patients with COPD undergoing PT.
Physical exercise has been described as having an essential role in the rehabilitation of patients with COPD. Dyspnea leads to progressive physical deconditioning, causing losses in strength and peripheral muscle endurance, in addition to metabolic and gas exchange abnormalities.1 Regarding the period of physical training, reported studies show that PT programs produce physiological effects in these patients after a minimum of 6 to 8 weeks. Some12 show that this 6 to 8 week period may be relatively short for producing physiological adaptations. For this reason, we opted for a training period of 12 weeks, with the objective of evaluating whether the training period could also be an additional factor influencing the results obtained between groups.
Our results agree with a number of reports showing that NIV can produce additional effects during exercise in patients with COPD. Keilty27 observed a significant improvement in dyspnea symptoms during a submaximal test with the application of pressure support in patients with COPD. Other studies, which have investigated the role of NIV associated with physical training, have also shown beneficial effects, such as better exercise tolerance,18,28,29 a reduction in dyspnea,18 an increase in arterial oxygenation,28 and an increase in respiratory muscle strength.17,30,31
In this study, we found that only the group that underwent PT with BiPAP® ventilation support had a significant reduction in SBP, HR, and blood lactate at the same intensity of exercise. The attenuation of these cardiovascular responses can be explained by the increase in muscular oxidation capacity, slowing the cardiovascular adjustments through metaboreflex response. Costes et al,18 in associating PT with NIV, observed a significant increase in oxygen consumption, but they found that there was no significant difference in blood lactate among the patients studied.
The use of NIV associated with physical exercise has been a useful option in patients with COPD and greater ventilatory limitation during physical exercise because it is a method that can offer respiratory assistance. In our patients with COPD, the use of BiPAP® associated with PT on a treadmill significantly reduced the blood lactate, at the same exercise intensity as the CPT exercise. Regarding blood lactate, our results are in agreement with the studies by Borghi-Silva13 and Pires Di Lorenzo et al,32 who, studied patients with a greater degree of obstruction and observed a significant reduction of blood lactate only in the group that performed physical training associated with bi-level NIV. These results can be explained by the improvement in the oxidative muscle capacity due to the greater availability of oxygen to the tissue; even though we did not observe differences between groups for SpO2, the PT+B group presented lower pretreatment base values; that is, they were more hypoxemic.
The benefits of the use of BiPAP® associated with physical exercise can probably be accounted for by the reduction of work for the diaphragm muscle, given the dynamic coupling of neuroventilation and the reduction of hyperinsuflation during physical effort. Aside from this, in diversion of blood flow from the peripheral muscle to the ventilatory muscle limits the continuity of physical exercise.33 It is possible that NIV can diminish mid-intrathoracic pressure and improve cardiac output, which could result in attenuation of the response of cardiovascular variables and in a lower production of blood lactate when this intervention is associated with PT on a treadmill. These results were concomitantly obtained with the increase of oxygen consumption at peak exercise.
A first limitation of this study is the small number of patients studied, given the strict criteria for inclusion in this study. Another limitation was the impossibility of obtaining breath-to-breath ventilatory and metabolic data because the equipment evaluated these variables in averages of 20 seconds. In addition, it was not possible to evaluate the flow limitation and dynamic hyperinflation during exercise, which would have supplied an important evaluation of the noninvasive ventilation during the physical exercise. Despite these limitations, differences between the interventions studied can be observed with the methodology applied in this study.
Finally, we conclude that physical training associated with the application of 2 levels of pressure in the airways provided an improved aerobic capacity in our patients, and this adjunct therapy can be a useful recourse during physical rehabilitation of patients with COPD who present a moderate-to-severe COPD and dyspnea in response to effort.
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Received for publication on July 5, 2006.
Accepted for publication on November 14, 2006.