Effect of Portable NIV on Operational Chest Wall Volumes in COPD

Study Design: This is a randomised crossover trial. Patients will perform two identical exercise tests and the intervention (VitaBreath) will be compared to control condition (pursed-lip breathing) in the same patients. The order of testing will be determined by simple randomisation (sealedenvelope.com). The purpose of this study is to investigate the effect of the VitaBreath device on inspiratory and expiratory thoracoabdominal wall volumes during exercise in patients with COPD. Use of the VitaBreath device will be compared to normal breathing (pursed lip breathing technique). Patients will primarily be recruited from those who participated in our previous study (REC reference: 17/NE/0085 - IRAS project ID: 221120) at North Tyneside General Hospital and will undergo two exercise tests on a cycle ergometer on the same day using both the VitaBreath device and the pursed-lip breathing technique during recovery from exercise. Study interventions: The study will include two visits. During the first visit patients will undergo a clinical assessment, including history, physical examination, ECG and full lung function assessment including spirometry, to ensure that patients are stable. During the second visit patients will perform two intermittent exercise tests lasting 20 minutes each and consisting of 2-min work bouts at 80% of peak work rate (WR peak) as determined in the previous study (REC reference: 17/NE/0085 - IRAS project ID: 221120) with 2-min recovery periods in between work bouts, using either the VitaBreath device or the pursed lip breathing technique during recovery periods. Patients will be given written information explaining the procedure and will provide written informed consent. Assessment Procedures Visit 1 Baseline assessment During the first visit patients will undergo the following baseline assessment: a) medical history and physical examination, b) spirometry and c) resting ECG to assess the resting heart function. Visit 2 Preparation of the patients Upon arrival to the laboratory, and prior to any intervention, adhesive skin markers for Opto-Electronic Plethysmography (OEP) recordings (to assess thoracoabdominal wall dynamic hyperinflation), and set of adhesive optodes for portable cardio-impedance recordings (to assess cardiac output), muscle surface electromyography (to assess muscle recruitment patterns) and near inferred spectroscopy (to assess respiratory muscle oxygen requirement) will be attached on the skin. All procedures will be explained in detail prior each trial. Operational chest wall volumes At baseline, patients will be instructed after 3-4 regular tidal breaths to make two maximal inspiratory capacity (IC) efforts from End Expiratory Chest Wall (EECW) Volume to Total Chest Wall Capacity (TLCCW) in order to assess chest wall volume at TLC (TLCCW) and Inspiratory Reserve Chest wall Volume (IRVcw) at rest. During exercise and recovery, chest wall kinematics will be measured by OEP as follows: the movement of 89 retro-reflective markers placed front and back over the chest wall from clavicles to pubis will be recorded. Each marker will be tracked by eight video cameras (Smart System BTS, Milan, Italy), four in front of the subject and four behind. Subjects will be grasp handles positioned at the mid sternum level which will lift the arms away from the rib cage so that lateral markers can be visualised. Dedicated software reconstructs the three-dimensional coordinates of the markers in real time by stereophotogrametry and calculates total and compartmental chest wall volume and volume variations using Gauss's theorem. The chest wall is modelled as being composed of two compartments-the rib cage and the abdomen. Vcw is the sum of the rib cage volume (Vrc) and abdominal volume (Vab). Non-Invasive assessment of respiratory muscle oxygenation In addition to operational chest wall volumes investigators are going to assess intercostal and abdominal local muscle oxygenation using Near-Infrared Spectroscopy (NIRS). Two NIRS optodes, which will be connected to a NIRO 200 spectrophotometer (Hamamatsu Photonics, Hamamatsu, Japan), will be placed on the skin over the left seventh intercostal space at the midaxillary line and over the upper rectus abdominis respectively, and will be secured using adhesive tape. The left intercostal space will be used to avoid potential blood flow contributions from the liver on the right side of the body. Respiratory muscle electromyography Electromyography (EMG) will be used in order assess respiratory muscle activation. Skin will be cleaned and surface electrodes (Delsys Trigno, Delsys, Boston, MA, USA) will be placed as follows: on the surface over the right seventh intercostal space (EMGic), 2 cm lateral to the umbilicus, over the muscle mass of rectus abdominis (EMGra), over the sternocleidomastoid muscle (EMGster), and on the scalene muscle (EMGsca). EMG data will be recorded at 2000Hz and will be filtered at 25-500 Hz during each trial (Spike 2, Cambridge Electronic Design, Cambridge, UK). Exercise protocol Patients will undergo two intermittent exercise protocols on a cycle ergometer. The exercise protocol will consist of repeated 2-min exercise bouts, separated by 2-min recovery periods in between work bouts in order to allow application of the VitaBreath device. During the 1st min of each recovery period patients will breathe either via the VitaBreath device or adopting the pursed lip breathing technique. During the 2nd min of each recovery period patients will breathe normally. Patients will also score the intensity of their perceived dyspnoea using the Borg 1-10 scale. Cardiac output and stroke volume will be measured non-invasively using a cardio-impedance method (physio-flow) throughout the exercise and recovery periods. Respiratory muscle activation (EMG) and local respiratory muscle oxygen tissue oxygenation (NIRS) will be continuously recorded non-invasively using optodes placed on the skin throughout the exercise and recovery periods. In addition, arterial oxygen saturation will be recorded throughout the exercise and recovery periods using a pulse oximeter. Sample size estimation Estimation of sample size within each breathing modality is based on the results of a study comparing use of the VitaBreath device to pursed lip breathing (PLB). Using the mean difference in the recovery of inspiratory capacity compared to the end of exercise (130 ml) between the VitaBreath device and PLB, the SD (110 ml), an alpha significance level of 0.05 (2-sided) and 80% power, a minimum total sample size of 11 patients is calculated to be sufficient to detect significant differences in the magnitude of change in thoracoabdominal wall dynamic hyperinflation between the VitaBreath device and PLB trials. 12 patients will be recruited in order to perform the trials in a balanced ordering sequence.