ABSTRACT
INTRODUCTION: Noninvasive ventilation (NIV) is a well-established treatment for acute-on- chronic respiratory failure in hypercapnic COPD patients. Less is known about the effects of a long-term treatment with NIV in hypercapnic COPD patients and about the factors that may predict response in terms of improved oxygenation and lowered CO(2) retention. METHODS: In this study, we randomized 15 patients to a routine pharmacological treatment (n = 5, age 66 [standard deviation ± 6] years, FEV(1) 30.5 [±5.1] %pred, PaO(2) 65 [±6] mmHg, PaCO(2) 52.4 [±6.0] mmHg) or to a routine treatment and NIV (using the Synchrony BiPAP device [Respironics, Inc, Murrsville, PA]) (n = 10, age 65 [±7] years, FEV(1) 29.5 [±9.0] %pred, PaO(2) 59 [±13] mmHg, PaCO(2) 55.4 [±7.7] mmHg) for 6 months. We looked at arterial blood gasses, lung function parameters and performed a low-dose computed tomography of the thorax, which was later used for segmentation (providing lobe and airway volumes, iVlobe and iVaw) and post-processing with computer methods (providing airway resistance, iRaw) giving overall a functional image of the separate airways and lobes. RESULTS: In both groups there was a nonsignificant change in FEV(1) (NIV group 29.5 [9.0] to 38.5 [14.6] %pred, control group 30.5 [5.1] to 36.8 [8.7] mmHg). PaCO(2) dropped significantly only in the NIV group (NIV: 55.4 [7.7] â 44.5 [4.70], P = 0.0076; control: 52.4 [6.0] â 47.6 [8.2], NS). Patients actively treated with NIV developed a more inhomogeneous redistribution of mass flow than control patients. Subsequent analysis indicated that in NIV-treated patients that improve their blood gases, mass flow was also redistributed towards areas with higher vessel density and less emphysema, indicating that flow was redistributed towards areas with better perfusion. There was a highly significant correlation between the % increase in mass flow towards lobes with a blood vessel density of >9% and the increase in PaO(2). Improved ventilation-perfusion match and recruitment of previously occluded small airways can explain the improvement in blood gases. CONCLUSION: We can conclude that in hypercapnic COPD patients treated with long-term NIV over 6 months, a mass flow redistribution occurs, providing a better ventilation-perfusion match and hence better blood gases and lung function. Control patients improve homogeneously in iVaw and iRaw, without improvement in gas exchange since there is no improved ventilation/perfusion ratio or increased alveolar ventilation. These differences in response can be detected through functional imaging, which gives a more detailed report on regional lung volumes and resistances than classical lung function tests do. Possibly only patients with localized small airway disease are good candidates for long-term NIV treatment. To confirm this and to see if better arterial blood gases also lead to better health related quality of life and longer survival, we have to study a larger population.
Subject(s)
Hypercapnia/therapy , Lung/physiopathology , Pulmonary Disease, Chronic Obstructive/therapy , Respiration, Artificial/methods , Respiratory Insufficiency/therapy , Aged , Belgium , Blood Gas Analysis , Female , Forced Expiratory Volume , Humans , Hypercapnia/diagnosis , Hypercapnia/etiology , Hypercapnia/physiopathology , Lung/blood supply , Lung/diagnostic imaging , Male , Middle Aged , Pilot Projects , Prospective Studies , Pulmonary Circulation , Pulmonary Disease, Chronic Obstructive/complications , Pulmonary Disease, Chronic Obstructive/diagnosis , Pulmonary Disease, Chronic Obstructive/physiopathology , Pulmonary Gas Exchange , Respiratory Insufficiency/diagnosis , Respiratory Insufficiency/etiology , Respiratory Insufficiency/physiopathology , Severity of Illness Index , Time Factors , Tomography, X-Ray Computed , Treatment OutcomeABSTRACT
A multidisciplinary pulmonary rehabilitation program has become an important part of the treatment of chronic obstructive pulmonary disease. It can improve both exercise tolerance and health related quality of life in these patients. Exercise training has to be included for the program to be successful. The intensity of the training is of great importance: there is more physiological benefit in high-intensity training, compared to moderate-intensity training. High-intensity training results in reduced levels of blood lactate and pulmonary ventilation at a given heavy work rate. High-intensity training is limited in COPD patients because of exercise-induced dyspnoea. Flow limitation, as a consequence of increased ventilatory demands of exercise, causes a breathing pattern with greater demands on their inspiratory muscles: this results in a pattern of low tidal volume and high-frequency breathing. Increased inspiratory muscle work causes dyspnoea and limitation in exercise intensity. Artificial ventilatory assistance could improve exercise tolerance and hence help severe COPD patients to achieve a higher level of training. It could help to unload and assist the overburdened ventilatory muscles and give a possibility for higher levels of exercise intensity. In this review article we will discuss the effectiveness and feasibility of training with ventilatory aids.
