Objective: Pulmonary rehabilitation (PR) improves exercise capacity in most but not all COPD patients. The factors associated with treatment success and the role of chest wall mechanics remain unclear. We investigated the impact of PR on exercise performance in COPD with severe hyperinflation. Methods: We evaluated 22 COPD patients (age, 66 ± 7 years; FEV1 = 37.1 ± 11.8% of predicted) who underwent eight weeks of aerobic exercise and strength training. Before and after PR, each patient also performed a six-minute walk test and an incremental cycle ergometer test. During the latter, we measured chest wall volumes (total and compartmental, by optoelectronic plethysmography) and determined maximal workloads. Results: We observed significant differences between the pre- and post-PR means for six-minute walk distance (305 ± 78 vs. 330 ± 96 m, p < 0.001) and maximal workload (33 ± 21 vs. 39 ± 20 W; p = 0.02). At equivalent workload settings, PR led to lower oxygen consumption, carbon dioxide production (VCO2), and minute ventilation. The inspiratory (operating) rib cage volume decreased significantly after PR. There were 6 patients in whom PR did not increase the maximal workload. After PR, those patients showed no significant decrease in VCO2 during exercise, had higher end-expiratory chest wall volumes with a more rapid shallow breathing pattern, and continued to experience symptomatic leg fatigue. Conclusions: In severe COPD, PR appears to improve oxygen consumption and reduce VCO2, with a commensurate decrease in respiratory drive, changes reflected in the operating chest wall volumes. Patients with severe post-exercise hyperinflation and leg fatigue might be unable to improve their maximal performance despite completing a PR program.

1. Programa de Pós-Graduação em Reabilitação e Inclusão e Programa de Pós-Graduação em Biociências e Reabilitação, Curso de Fisioterapia, Centro Universitário Metodista, Instituto Porto Alegre, Porto Alegre (RS) Brasil 2. Unidad de Terapia Intensiva y de Ventilación no Invasiva, Hospital Morales Meseguer. Murcia, España. We would like to highlight the importance of the study entitled “Exercise performance and differences in physiological response to pulmonary rehabilitation in severe chronic obstructive pulmonary disease with hyperinflation”,(1) which was recently published in the JBP. The authors evaluated the impact of pulmonary rehabilitation on exercise tolerance in severe COPD with hyperinflation. That study showed improvement in oxygen consumption, reduced carbon dioxide production, and decreased respiratory drive; however, patients with post-exercise hyperinflation did not improve their maximal performance. We congratulate the authors for the important findings, but some key issues need to be taken into account for a proper clinical extrapolation.

Chronic obstructive pulmonary disease (COPD) patients often show asynchronous movement of the lower rib cage during spontaneous quiet breathing and exercise. We speculated that varying body position from seated to supine would influence rib cage asynchrony by changing the configuration of the respiratory muscles. Twenty-three severe COPD patients (forced expiratory volume in 1 s = 32.5 ± 7.0% predicted) and 12 healthy age-matched controls were studied. Measurements of the phase shift between upper and lower rib cage and between upper rib cage and abdomen were performed with opto-electronic plethysmography during quiet breathing in the seated and supine position. Changes in diaphragm zone of apposition were measured by ultrasounds. Control subjects showed no compartmental asynchronous movement, whether seated or supine. In 13 COPD patients, rib cage asynchrony was noticed in the seated posture. This asynchrony disappeared in the supine posture. In COPD, upper rib cage and abdomen were synchronous when seated, but a strong asynchrony was found in supine. The relationships between changes in diaphragm zone of apposition and volume variations of chest wall compartments supported these findings. Rib cage paradox was noticed in approximately one-half of the COPD patients while seated, but was not related to impaired diaphragm motion. In the supine posture, the rib cage paradox disappeared, suggesting that, in this posture, diaphragm mechanics improves. In conclusion, changing body position induces important differences in the chest wall behavior in COPD patients.

Non‐technical summary Cough is the commonest symptom for which people seek medical advice and has significant impact upon quality of life. Moreover ineffective coughing is associated with significant morbidity and mortality. A better understanding of cough mechanics is important for dealing with the complications of both excessive and impaired cough. This study investigates how the mechanical changes during coughing are influenced by the amount of air inhaled prior to coughing (operating volume), examining chest and abdominal motion, pressures and flow. We have shown that operating volume is the most important determinant of the flow achieved and volume expelled during single voluntary coughs and peals of voluntary coughs. Coughs within a peal appear to have a different motor pattern, producing similar pressures and flows but more rapidly than single coughs and therefore may be more efficient. Future studies investigating cough mechanics should control for the influence of operating volume.

In COPD hyperinflation alters the function of the inspiratory muscles. The zone of apposition of the diaphragm (ZOM) is reduced, thus COPD patients often show paradoxical movement of the lower rib cage. The aim of this study is to investigate if in COPD chest wall and diaphragm asynchronies are altered by posture. 24 severe COPD (FEV1=32.5±7.0%pred) and 12 age-matched controls (CTR) (FEV1=111.1±16.2) were studied during quiet breathing in seated (ST) and supine (SP) positions. Phase shift (θ) between pulmonary rib cage (RCp) and abdominal rib cage (RCa) and θ between RCp and the abdomen (AB) were assessed by opto-electronic plethysmography.The cranio-caudal displacement of the ZOM (ΔZOM) was contemporarily measured by ultrasonography. Neither θ between RCp and RCa or θ between RCp and AB was altered by posture in CTR. Conversely, in COPD patients, θ between RCp and RCa decreased when changing posture from ST to SP (θ=23.7°±19.5, θ=5.2°±18.1 respectively, p<0.001).RCp and AB in COPD showed a behavior similar to CTR while in ST (θ=1.3°±13.3 in COPD, θ=0.1°±4.5 in CTR), but strongly differed in SP (θ= -25.0°±18.2, p<0.001; p<0.01, COPD vs. CTR).Moreover, in COPD ΔZOM was linearly correlated to RCp in ST (r2=0.718±0.140), similarly to control subjects (r2=0.729±0.150), while it was significantly less correlated to RCa (r2=0.510±0.246, p<0.01).In COPD correlation between ΔZOM and both RCp and RCa decreased (r2=0.530±0.244, r2=0.511±0.230 p<0.05) in SP. In COPD the diaphragm and RCa are uncorrelated in ST, but the synchronous action of the rib cage muscles and the diaphragm is similar to healthy. In SP the diaphragm is uncorrelated with both RCp and RCa, so the asynchrony with the rib cage muscles seems to be pronounced.

BACKGROUND:Anaesthesia based on inhalational agents has profound effects on chest wall configuration and breathing pattern. The effects of propofol are less well characterised. The aim of the current study was to evaluate the effects of propofol anaesthesia on chest wall motion during spontaneous breathing and positive pressure ventilation.METHODS:We studied 16 subjects undergoing elective surgery requiring general anaesthesia. Chest wall volumes were continuously monitored by opto-electronic plethysmography during quiet breathing (QB) in the conscious state, induction of anaesthesia, spontaneous breathing during anaesthesia (SB), pressure support ventilation (PSV) and pressure control ventilation (PCV) after muscle paralysis.RESULTS:The total chest wall volume decreased by 0.41 ± 0.08 l immediately after induction by equal reductions in the rib cage and abdominal volumes. An increase in the rib cage volume was then seen, resulting in total chest wall volumes 0.26 ± 0.09, 0.24 ± 0.10, 0.22 ± 0.10 l lower than baseline, during SB, PSV and PCV, respectively. During QB, rib cage volume displacement corresponded to 34.2 ± 5.3% of the tidal volume. During SB, PSV and PCV, this increased to 42.2 ± 4.9%, 48.2 ± 3.6% and 46.3 ± 3.2%, respectively, with a corresponding decrease in the abdominal contribution. Breathing was initiated by the rib cage muscles during SB.CONCLUSION:Propofol anaesthesia decreases end-expiratory chest wall volume, with a more pronounced effect on the diaphragm than on the rib cage muscles, which initiate breathing after apnoea.

We compared the rate of perceived exertion for respiratory (RPE,resp) and leg (RPE,legs) muscles, using a 10-point Borg scale, to their specific power outputs in 10 healthy male subjects during incremental cycle exercise at sea level (SL) and high altitude (HA, 4559 m). Respiratory power output was calculated from breath-by-breath esophageal pressure and chest wall volume changes. At HA ventilation was increased at any leg power output by ∼ 54%. However, for any given ventilation, breathing pattern was unchanged in terms of tidal volume, respiratory rate and operational volumes of the different chest wall compartments. RPE,resp scaled uniquely with total respiratory power output, irrespectively of SL or HA, while RPE,legs for any leg power output was exacerbated at HA. With increasing respective power outputs, the rate of change of RPE,resp exponentially decreased, while that of RPE,legs increased. We conclude that RPE,resp uniquely relates to respiratory power output, while RPE,legs varies depending on muscle metabolic conditions.

Assessment of the presence and severity of acute mountain sickness (AMS) is based on subjective reporting of the sensation of symptoms. The Lake Louise symptom scoring system (LLS) uses categorical variables to rate the intensity of AMS-related symptoms (headache, gastrointestinal distress, dizziness, fatigue, sleep quality) on 4-point ordinal scales; the sum of the answers is the LLS self-score (range 0-15). Recent publications indicate a potential for a visual analogue scale (VAS) to quantify AMS. We tested the hypothesis that overall and single-item VAS and LLS scores scale linearly. We asked 14 unacclimatized male subjects [age 41 (14), mean (SD) yr; height 176 (3) cm; weight 75 (9) kg] who spent 2 days at 3647 m and 4 days at 4560 m to fill out LLS questionnaires, with a VAS for each item (i) and a VAS for the overall (o) sensation of AMS, twice a day (n = 172). Even though correlated (r = 0.84), the relationship between LLS(o) and VAS(o) was distorted, showing a threshold effect for LLS(o) scores below 5, with most VAS(o) scores on one side of the identity line. Similar threshold effects were seen for the LLS(i) and VAS(i) scores. These findings indicate nonlinear scaling characteristics that render difficult a direct comparison of studies done with either VAS or LLS alone.

Peribronchial edema has been proposed as a mechanism enhancing airway responses to constrictor stimuli. Acute exposure to altitude in nonacclimatized lowlanders leads to subclinical interstitial pulmonary edema that lasts for several days after ascent, as suggested by changes in lung mechanics. We, therefore, investigated whether changes in lung mechanics consistent with fluid accumulation at high altitude within the lungs are associated with changes in airway responses to methacholine or exercise. Fourteen healthy subjects were studied at 4,559 and at 120 m above sea level. At high altitude, both static and dynamic lung compliances and respiratory reactance at 5 Hz significantly decreased, suggestive of interstitial pulmonary edema. Resting minute ventilation significantly increased by approximately 30%. Compared with sea level, inhalation of methacholine at high altitude caused a similar reduction of partial forced expiratory flow but less reduction of maximal forced expiratory flow, less increments of pulmonary resistance and respiratory resistance at 5 Hz, and similar effects of deep breath on pulmonary and respiratory resistance. During maximal incremental exercise at high altitude, partial forced expiratory flow gradually increased with the increase in minute ventilation similarly to sea level but both achieved higher values at peak exercise. In conclusion, airway responsiveness to methacholine at high altitude is well preserved despite the occurrence of interstitial pulmonary edema. We suggest that this may be the result of the increase in resting minute ventilation opposing the effects and/or the development of airway smooth muscle force, reduced gas density, and well preserved airway-to-parenchyma interdependence.

Paradoxical inward displacement of the costal margin during inspiration is observed in many chronic obstructive pulmonary disease patients at rest but its importance is unclear. The current authors studied 20 patients (forced expiratory volume in one second 32.6±11.7, functional residual capacity 186±32% predicted) and 10 healthy controls at rest and during symptom-limited incremental exercise. With optoelectronic plethysmography, the phase shift between pulmonary and abdominal ribcage volumes and the percentage of inspiratory time the ribcage compartments moved in opposite directions were quantified, using control data to define the normal range of movement. Eight patients showed lower ribcage inspiratory paradox at rest (P+), while 12 patients did not (P-). This was unrelated to resting lung function or exercise tolerance. Total end-expiratory chest wall volume (EEVcw) increased immediately when exercise began in P+ patients, but later in exercise in P- patients. This difference in EEVcw was mainly due to a greater increase of end-expiratory pulmonary ribcage volume in P+ patients. During exercise, dyspnoea increased similarly in the two groups, while leg effort increased more markedly in the patients without paradox. In conclusion, lower ribcage paradox at rest is reproducible and associated with early-onset hyperinflation of the chest wall and predominant dyspnoea at end-exercise. When paradox is absent, the sense of leg effort becomes a more important symptom limiting exercise.

In this work three ECG derived respiration (EDR) methods based on multi leads ECG are applied to a single lead, to evaluate the capabilities to use this method with wearable devices. Preliminary result shows the R-R interval method applied to two wire single lead ECG is more suitable to extract the fundamental respiratory frequency.

Three-dimensional reconstruction of human diaphragm provide useful information on the functional anatomy of the respiratory system by the analysis of its geometry. The aim of the current work is the development of a new method for the 3D analysis of diaphragm geometry by the combination of free-hand Ultrasound (US) scans with an optoelectronic system of movement analysis for the tracking of the probe. 6 healthy subjects (age=24±2), have been measured with a free-hand US scanning of the abdomen in supine (SP) and seated position (ST), during breath-holding at Functional Residual Capacity (FRC) and Total Lung Capacity (TLC). For one of them, measurements have been repeated in supine position in an MR scan for the validation of the method. Posture has different implications on diaphragm geometry depending on the respiratory volume. At FRC the ray of curvature (ρ) in ST is 101.1±43.1 mm higher than in SP (p=0.006), while at TLC, posture influences the position of the diaphragm with a caudo-cranial displacement from SP to ST of 23.4±16.7mm (p=0.019). Diaphragm geometry at different lung volumes is influenced by the posture. In SP, ρ increases of 105.9±48.3 mm (p=0.008) and there is a cranio-caudal displacement (Δy) of 47.54±15 mm (p=0.002) shifting from FRC to TLC. In ST, Δy=31.1±13.5 mm (p=0.006) while ρ increases not significantly. Percentage errors between MR and US 3D reconstructions are 2.1% and 10.46% for Δy and TLC/FRC ρ ratio, respectively. US 3D reconstruction is a reliable method for the assessment of diaphragm functional anatomy. Posture directly influence diaphragm geometry and hence respiratory mechanics.

Calibrated ultrasound (US) probes, formerly used in neurosurgery for acquiring bone implanted markers, have been recently introduced to perform non-invasive registration during computer assisted orthopaedic surgery total knee replacement. In this study an experimental set-up system to detects the surface of the bone using a 3D US probe navigation procedures non-invasively is presented. Preliminary test shows a reconstruction error of about 0.6 +/- 0.39mm.

An extensive literature reports that in most patients with Chronic Obstructive Pulmonary Disease (COPD), dynamic hyperinflation occurs during constant workload exercise testing. In a recent study (Thorax, 2004;59:210-216), we found that in stable COPD two different patterns can be present during incremental exercise: patients who increase end-expiratory chest wall volume (EEVcw) and patients who try to reduce EEVcw or keep it constant. No previous study has examined the responses in term of EE volumes to different exercise tests in COPD patients. To investigate possible relationships between exercise protocol and pattern of variation of EE volume we examined 10 stable COPD patients who performed both an incremental and a constant workload exercise test on separate days and we compared data at isoworkload.