Effectiveness of pulmonary rehabilitation in patients with interstitial lung disease of different etiology: a multicenter prospective study.

BACKGROUND: Recent evidences show that Pulmonary Rehabilitation (PR) is effective in patients with Interstitial Lung Disease (ILD). It is still unclear whether disease severity and/or etiology might impact on the reported benefits. We designed this prospective study 1) to confirm the efficacy of rehabilitation in a population of patients with ILDs and 2) to investigate whether baseline exercise capacity, disease severity or ILD etiology might affect outcomes. METHODS: Forty-one patients (IPF 63%, age 66.9 ± 11 ys) were enrolled in a standard PR course in two centers. Lung function, incremental and endurance cyclo-ergometry, Six Minutes Walking Distance (6MWD), chronic dyspnea (Medical Research Council scale-MRC) and quality of life (St. George Respiratory Questionnaire-SGRQ) were recorded before and at the end of PR to measure any pre-to-post change. Correlation coefficients between the baseline level of Diffuse Lung Capacity for Carbon monoxide (DLCO), Forced Vital Capacity (FVC), 6MWD, power developed during incremental endurance test, GAP index (in IPF patients only) and etiology (IPF or non-IPF) with the functional improvement at the 6MWDT (meters), at the incremental and endurance cyclo-ergometry (endurance time) and the HRQoL were assessed. RESULTS: Out of the 41 patients, 97% (n = 40) completed the PR course. Exercise performance (both at peak load and submaximal effort), symptoms (iso-time dyspnea and leg fatigue), SGRQ and MRC significantly improved after PR (p < .001). Patients with lower baseline 6MWD showed greater improvement in 6MWD (Spearman r score = - .359, p = .034) and symptoms relief at SGRQ (r = -.315, p = .025) regardless of underlying disease. CONCLUSION: Present study confirms that comprehensive rehabilitation is feasible and effective in patients with ILD of different severity and etiology. The baseline submaximal exercise capacity inversely correlates with both functional and symptom gains in this heterogeneous population.

Dyspnea, chest wall hyperinflation, and rib cage distortion in exercising patients with chronic obstructive pulmonary disease.

PURPOSE: Whether dyspnea, chest wall dynamic hyperinflation, and abnormalities of rib cage motion are interrelated phenomena has not been systematically evaluated in patients with chronic obstructive pulmonary disease (COPD). Our hypothesis that they are not interrelated was based on the following observations: (i) externally imposed expiratory flow limitation is associated with no rib cage distortion during strenuous incremental exercise, with indexes of hyperinflation not being correlated with dyspnea, and (ii) end-expiratory chest wall volume may either increase or decrease during exercise in patients with COPD, with those who hyperinflate being as breathless as those who do not. METHODS: Sixteen patients breathed either room air or 50% supplemental O2 at 75% of peak exercise in randomized order. We evaluated the volume of chest wall (V(cw)) and its compartments: the upper rib cage (V(rcp)), lower rib cage (V(rca)), and abdomen (V(ab)) using optoelectronic plethysmography; rib cage distortion was assessed by measuring the phase angle shift between V(rcp) and V(rca). RESULTS: Ten patients increased end-expiratory V(cw) (V(cw,ee)) on air. In seven hyperinflators and three non-hyperinflators, the lower rib cage paradoxed inward during inspiration with a phase angle of 63.4° ± 30.7° compared with a normal phase angle of 16.1° ± 2.3° recorded in patients without rib cage distortion. Dyspnea (by Borg scale) averaged 8.2 and 9 at the end of exercise on air in patients with and without rib cage distortion, respectively. At iso-time during exercise with oxygen, decreased dyspnea was associated with a decrease in ventilation regardless of whether patients distorted the rib cage, dynamically hyperinflated, or deflated the chest wall. CONCLUSIONS: Dyspnea, chest wall dynamic hyperinflation, and rib cage distortion are not interrelated phenomena.

Prevalence of limb muscle dysfunction in patients with chronic obstructive pulmonary disease admitted to a pulmonary rehabilitation centre.

OBJECTIVE: Assessment of needle electromyography (nEMG) may complement previous data on limb muscle dysfunction (LMD) in patients with chronic obstructive pulmonary disease (COPD). We attempted to quantify the prevalence of LMD and assess its impact on clinical outcomes in patients admitted to a rehabilitation programme. METHODS: One hundred and thirty-two clinically stable patients were consecutively enrolled. They underwent spirometry and the following primary outcomes were evaluated: St. George respiratory questionnaire (SGRQ), functional independence measure (FIM) questionnaire and a 6-min walking test (6MWT). One hundred and fourteen patients underwent nEMG. The frequency of LMD was related to COPD stage and chronic dyspnoea. RESULTS: nEMG detected myopathic signs in 36.8% of the patients. LMD was found even in early stages of COPD. FIM and 6MWT were significantly lower, and SGRQ tended to be higher at each COPD stage in patients with LMD. However, the 6MWT rate of decay across the COPD stages was similar in patients with and without LMD. CONCLUSIONS: LMD might not be restricted to patients with severe airway obstruction and regardless of COPD stage, contributes to functional limitation of these patients. SIGNIFICANCE: The putative role of LMD in motor limitations indicates the need to assess it early onto better organise a specific training programme as part of general pulmonary rehabilitation in COPD patients.

Chest wall kinematics and breathlessness during unsupported arm exercise in COPD patients.

We hypothesised that chest wall displacement inappropriate to increased ventilation contributes to dyspnoea more than dynamic hyperinflation or dyssynchronous breathing during unsupported arm exercise (UAE) in COPD patients. We used optoelectronic plethysmography to evaluate operational volumes of chest wall compartments, the upper rib cage, lower rib cage and abdomen, at 80% of peak incremental exercise in 13 patients. The phase shift between the volumes of upper and lower rib cage (RC) was taken as an index of RC distortion. With UAE, no chest wall dynamic hyperinflation was found; sometimes the lower RC paradoxed inward while in other patients it was the upper RC. Phase shift did not correlate with dyspnoea (by Borg scale) at any time, and chest wall displacement was in proportion to increased ventilation. In conclusions neither chest wall dynamic hyperinflation nor dyssynchronous breathing per se were major contributors to dyspnoea. Unlike our prediction, chest wall expansion and ventilation were adequately coupled with each other.

Blunted respiratory-related evoked potential in awake obstructive sleep apnoea subjects: a NEP technique study.

OBJECTIVE: Respiratory-related evoked potentials (RREP) elicited by transmural pressure in obstructive sleep apnoea (OSA) subjects have reported conflicting data. Different features of pressure stimuli and/or in the timing of stimuli application seem to account for these contradictory results. The negative expiratory pressure (NEP) technique, highly reproducible in terms of rise time and pressure values, allows to minimize the methodological confounding factors. We determined whether the afferent activity from the upper airway (UA) is altered in OSA subjects. METHODS: RREP potentials were examined in 10 OSA and in 12 non-apnoeic awake subjects by means of the NEP technique. RESULTS: All controls showed a cortical response to all pressure stimuli. All OSA subjects showed responses to -5 and -10 cmH(2)O whereas six of them showed no responses to -1 cmH(2)O. The amplitude of the P22, N45 and P85 components of the RREP was significantly reduced in OSA with respect to the controls in response to both the -5 and -10 cmH(2)O stimuli. We found no significant differences in latencies. CONCLUSIONS: Awake OSA subjects had a raised threshold to pressure stimuli and blunted respiratory-related evoked potentials. SIGNIFICANCE: These data indicate a deficit in afferent activity in the UA.

Dyspnea during speech in chronic obstructive pulmonary disease patients: effects of pulmonary rehabilitation.

BACKGROUND: For patients with limited physical activities who use oral communication for most social activities, the assessment of dyspnea during speech activities (DS) may provide relevant measurement criteria. Although speech production is altered by lung disease it has not been included in current dyspnea assessment tools. OBJECTIVES: We evaluated DS in patients with chronic obstructive pulmonary disease (COPD) with the aim of assessing: (i) the responsiveness to treatment of this newly developed evaluative dyspnea tool and (ii) whether DS is an independent measurement of other traditional outcomes. METHODS: We assessed lung function, the 6-min walking test (6'WT), chronic exertional dyspnea (MRC and BDI/TDI), and DS using the speech section of the University of Cincinnati Dyspnea Questionnaire (UCDQ) before and after a pulmonary rehabilitation program in 31 patients with COPD. RESULTS: The following items of the speech section of the UCDQ caused dyspnea: conversation, raising the voice, phoning, speaking to a group, talking in a noisy place, and singing. The mean overall DS score was 60 ± 23% of a maximal potential DS score. Pulmonary rehabilitation reduced each item of DS independently of change in lung function, chronic exertional dyspnea, and 6'WT. CONCLUSIONS: We concluded that DS is responsive to a respiratory rehabilitation program in patients with COPD. Evidence of independent objective measures supports the validity of a routine multivariable assessment including DS. We recommend assessment of DS particularly for patients who rely extensively on speech for communication.

Impact of a rehabilitation program on dyspnea intensity and quality in patients with chronic obstructive pulmonary disease.

BACKGROUND: It has yet to be determined whether the language of dyspnea responds to pulmonary rehabilitation programs (PRP). OBJECTIVE: We tested the hypothesis that PRP affect both the intensity and quality of exercise-induced dyspnea in patients with chronic obstructive pulmonary disease (COPD). METHODS: We studied 49 patients equipped with a portable telemetric spiroergometry device during the 6-min walking test before and 4 weeks after PRP. In a first screening visit, appropriate verbal descriptors of dyspnea were chosen that patients were familiar with during daily living activities. Tidal volume, respiratory frequency, inspiratory capacity, inspiratory reserve volume (IRV) and dyspnea intensity were evaluated by a modified Borg scale every minute during the test. RESULTS: Qualitative descriptors of dyspnea were defined by three different sets of cluster descriptors (a-c) at the end of the exercise test, before and after PRP: a - work/effort (W/E); b - inspiratory difficulty (ID) and chest tightness (CT), and c - W/E, ID and/or CT. The three language subgroups exhibited similar lung function at baseline, and similar rating of dyspnea and ventilatory changes during exercise. The rehabilitation program shifted the Borg-IRV relationship (less Borg at any given IRV) towards the right without modifying the set of descriptors in most patients. CONCLUSIONS: Rehabilitation programs allowed patients to tolerate a greater amount of restrictive dynamic ventilatory defect by modifying the intensity, but not necessarily the quality of dyspnea.

Chest wall kinematics during voluntary cough in neuromuscular patients.

Muscular diseases are characterized by progressive loss of muscle strength, resulting in cough ineffectiveness with its deleterious effects on the respiratory system. Assessment of cough effectiveness is therefore a prominent component of the clinical evaluation and respiratory care in these patients. Owing to uneven distribution of muscle weakness in neuromuscular patients, we hypothesized that forces acting on the chest wall may impact on the compartmental distribution of gas volume resulting in a decrease in cough effectiveness. Pulmonary volumes, respiratory muscle strength, peak cough flow and chest wall kinematics by optoelectronic plethysmography were studied in 8 patients and 12 healthy subjects as controls. Chest wall volume was modeled as the sum of volumes of the rib cage and abdomen. The plot of the volumes of upper to lower rib cage allowed assessment of rib cage distortion. Unlike controls, patients were unable to reduce end-expiratory chest wall volume, and exhibited greater rib cage distortion during cough. Peak cough flow was negatively correlated with rib cage distortion (the greater the former, the smaller the latter), but not with respiratory muscle strength. In conclusion, insufficient deflation of chest wall compartments and marked rib cage distortion resulted in cough ineffectiveness in these neuromuscular patients.

Optoelectronic Plethysmography has Improved our Knowledge of Respiratory Physiology and Pathophysiology.

It is well known that the methods actually used to track thoraco-abdominal volume displacement have several limitations. This review evaluates the clinical usefulness of measuring chest wall kinematics by optoelectronic plethysmography [OEP]. OEP provides direct measurements (both absolute and its variations) of the volume of the chest wall and its compartments, according to the model of Ward and Macklem, without requiring calibration or subject cooperation. The system is non invasive and does not require a mouthpiece or nose-clip which may modify the pattern of breathing, making the subject aware of his breathing. Also, the precise assessment of compartmental changes in chest wall volumes, combined with pressure measurements, provides a detailed description of the action and control of the different respiratory muscle groups and assessment of chest wall dynamics in a number of physiological and clinical experimental conditions.

Chest wall kinematics and Hoover's sign.

BACKGROUND: No attempt has been made to quantify the observed rib cage distortion (Hoover's sign) in terms of volume displacement. We hypothesized that Hoover's sign and hyperinflation are independent quantities. METHODS: Twenty obstructed stable patients were divided into two groups according to whether or not they exhibited Hoover's sign during clinical examination while breathing quietly. We evaluated the volumes of chest wall and its compartments: the upper rib cage, the lower rib cage and the abdomen, using optoelectronic plethysmography. RESULTS: The volumes of upper rib cage, lower rib cage and abdomen as a percentage of absolute volume of the chest wall were similar in patients with and without Hoover's sign. In contrast, the tidal volume of the chest wall, upper rib cage, lower rib cage, their ratio and abdomen quantified Hoover's sign, but did not correlate with level of hyperinflation. CONCLUSIONS: Rib cage distortion and hyperinflation appear to define independently the functional condition of these patients.

Patterns of chest wall kinematics during volitional pursed-lip breathing in COPD at rest.

BACKGROUND: Analysis of chest wall kinematics can contribute to identifying the reasons why some patients benefit from pursed-lip breathing (PLB). MATERIAL AND METHODS: We evaluated the displacement of the chest wall and its compartments, the rib cage and abdomen, by optoelectronic plethysmography (OEP), during supervised PLB maneuver in 30 patients with mild to severe chronic obstructive pulmonary disease (COPD). RESULTS: OEP showed two different patterns. A first pattern characterized the 19 most severely obstructed and hyperinflated patients in whom PLB decreased end-expiratory volumes of the chest wall and abdomen, and increased end-inspiratory volumes of the chest wall and rib cage. Deflation of the abdomen and inflation of the rib cage contributed to increasing tidal volume of the chest wall. The second pattern characterized 11 patients in whom, compared to the former group, PLB resulted in the following: (i) increased end-expiratory volume of the rib cage and chest wall, (ii) greater increase in end-inspiratory volume of the rib cage and abdomen, and (iii) lower tidal volume of the chest wall. In the patients as a whole changes in end-expiratory chest wall volume were related to change in Borg score (r(2)=0.5, p<0.00002). CONCLUSIONS: OEP helps identifying the reason why patients with COPD may benefit from PLB at rest.

Cortical excitability in obstructive sleep apnea syndrome: transcranial magnetic stimulation study.

STUDY OBJECTIVE: To investigate cortical motor area function in patients with obstructive sleep apnea syndrome (OSAS) during the daytime. DESIGN: The day after a nocturnal polysomnography, transcranial magnetic stimulation (TMS) of the motor cortex was performed recording Motor Evoked Potential from the first dorsal interosseous muscle of the dominant hand. We evaluated: 1) the relaxed motor threshold (RMT), 2) the threshold of the cortical silent period (CSP), 3) the duration of CSP elicited by five stimulus intensities (95%,100%,105%,130%, and 150% of RMT). To estimate the influence of waking on TMS, recordings were performed five times in a day. The Epworth Sleepiness Scale (ESS), and Stanford Sleepiness Scale (SSS) were also measured. SETTING: The study was carried out in the Sleep and Evoked Potentials laboratories of the Don C. Gnocchi Foundation (ONLUS IRCCS) Pozzola tico, (Florence), Italy. PATIENTS: 10 patients with OSAS and 10 healthy volunteers. INTERVENTION: N/A Measurements and Results: In OSAS patients, ESS and SSS were significantly higher than in controls. Patients had a longer duration of CSP at 95%,100% and 105% RMT intensity at almost recording hours; with 130% of RMT stimuli intensity OSAS patients were significantly different at 10AM from controls and with 150% of RMT intensity the difference did not reach significativity. PaCO2 was significantly correlated with CSP duration elicited at 10AM with 95%, 100% and 105% of RMT stimulus intensities. CONCLUSIONS: We found alterations of motor cortical excitability in OSAS patients during the daytime. We believe that PaCO2 levels, acting probably on various ion channels or metabolic pathways, may change the excitability of motor cortex modifying excitatory and inhibitory cortical circuits.

Walking modality affects respiratory muscle action and contribution to respiratory effort.

We hypothesized that walking at increased speed or increasing gradient might have different effects on chest wall kinematics and respiratory muscle power components, and contribute differently to respiratory effort sensation. We measured the volumes of chest wall compartments by optoelectronic plethysmography, esophageal, gastric and transdiaphragmatic ( P(di)) pressures, and the sensation of the respiratory effort by a Borg scale in five normal subjects walking both at ascending gradient with constant speed (AG) and at ascending speed with constant gradient (AS). Chest wall kinematics, evaluated by displacement of chest wall compartments, did not show any significant difference between AS and AG. Muscle power, calculated as the product of mean flow and mean pressure, increased similarly, but its partitioning into pressure and velocity of shortening differed in the two modes. A greater increase in the pressure developed by the abdominal muscles ( P(abm)) (4.06-fold), and in the velocity of shortening of both rib cage inspiratory muscles ( v(rcm,i)) (2.01-fold) and the diaphragm ( v(di)) (1.90-fold) was associated with a lower increase in the pressure developed by the rib cage inspiratory muscles ( P(rcm,i)) (1.24-fold) and P(di) (0.99-fold) with AG. Instead, with AS, a lower increase in P(abm) (2.12-fold), v(rcm,i) (1.66-fold) and v(di) (1.54-fold) was associated with a greater increase in P(rcm,i) (1.56-fold) and P(di) (1.97-fold). A combination of P(abm) and v(di) during AG (Wald chi(2)=23.19, P<0.0000), with the addition of P(rcm,i) during AS (Wald chi(2)=29.46, P<0.0000), was the best predictor of Borg score. In conclusion, the general strategy adopted by respiratory centers during different walking modes does not differ in terms of ventilation, chest wall kinematics, and respiratory muscle power production, whereas it does in terms of partitioning of power into pressure and velocity of shortening, and respiratory muscle contribution to respiratory effort sensation. Combinations of different patterns of flow and pressure generation made the respiratory effort sensation similar during AS and AG modes.

Chest wall kinematics and breathlessness during pursed-lip breathing in patients with COPD.

BACKGROUND: Pursed-lip breathing (PLB) is a strategy often spontaneously employed by patients with COPD during distress situations. Whether and to what extent PLB affects operational lung volume is not known. Also, conflicting reports deal with PLB capability of decreasing breathlessness. PARTICIPANTS AND MEASUREMENTS: Twenty-two patients with mild-to-severe COPD were studied. Volumes of chest wall (CW) compartments (rib cage [RC] and abdomen) were assessed using an optoelectronic plethysmograph. Dyspnea was assessed by a modified Borg scale. RESULTS: Compared to spontaneous breathing, patients with PLB exhibited a significant reduction (mean +/- SD) in end-expiratory volume of the CW (VCW) [VCWee; - 0.33 +/- 0.24 L, p < 0.000004], and a significant increase in end-inspiratory VCW (VCWei; + 0.32 +/- 0.43 L, p < 0.003). The decrease in VCWee, mostly due to the decrease in end-expiratory volume of the abdomen (VAbee) [- 0.25 +/- 0.21 L, p < 0.00002], related to baseline FEV(1) (p < 0.02) and to the increase in expiratory time (TE) [r(2) = 0.49, p < 0.0003] and total time of the respiratory cycle (TTOT) [r(2) = 0.35, p < 0.004], but not to baseline functional residual capacity (FRC). Increase in tidal volume (VT) of the chest wall (+ 0.65 +/- 0.48 L, p < 0.000004) was shared between VT of the abdomen (0.31 +/- 0.23 L, p < 0.000004) and VT of the rib cage (+ 0.33 +/- 0.29 L, p < 0.00003). Borg score decreased with PLB (p < 0.04). In a stepwise multiple regression analysis, decrease in VCWee accounted for 27% of the variability in Borg score at 99% confidence level (p < 0.008). CONCLUSIONS: Changes in VCWee related to baseline airway obstruction but not to hyperinflation (FRC). By lengthening of TE and TTOT, PLB decreases VCWee and reduces breathlessness.

Exercise training improves exertional dyspnea in patients with COPD: evidence of the role of mechanical factors.

BACKGROUND: To our knowledge, no data have been reported on the effects of exercise training (EXT) on central respiratory motor output or neuromuscular coupling (NMC) of the ventilatory pump, and their potential association with exertional dyspnea. Accurate assessment of these important clinical outcomes is integral to effective management of breathlessness of patients with COPD. MATERIAL AND METHODS: Twenty consecutive patients with stable moderate-to-severe COPD were tested at 6-week intervals at baseline, after a nonintervention control period (pre-EXT), and after EXT. Patients entered an outpatient pulmonary rehabilitation program involving regular exercise on a bicycle. Incremental symptom-limited exercise testing (1-min increments of 10 W) was performed on an electronically braked cycle ergometer. Oxygen uptake (O(2)), carbon dioxide output (CO(2)), minute ventilation (E), time, and volume components of the respiratory cycle and, in six patients, esophageal pressure swings (Pessw), both as actual values and as percentage of maximal (most negative in sign) esophageal pressure during sniff maneuver (Pessn), were measured continuously over the runs. Exertional dyspnea and leg effort were evaluated by administering a Borg scale. RESULTS: Measurements at baseline and pre-EXT were similar. Significant increase in exercise capacity was found in response to EXT: (1) peak work rate (WR), O(2), CO(2), E, tidal volume (VT), and heart rate increased, while peak exertional dyspnea and leg effort did not significantly change; (2) exertional dyspnea/O(2) and exertional dyspnea/CO(2) decreased while E/O(2) and E/CO(2) remained unchanged. The slope of both exertional dyspnea and leg effort relative to E fell significantly after EXT; (3) at standardized WR, E, and CO(2), exertional dyspnea and leg effort decreased while inspiratory capacity (IC) increased. Decrease in E was accomplished primarily by decrease in respiratory rate (RR) and increase in both inspiratory time (TI) and expiratory time; VT slightly increased, while inspiratory drive (VT/TI) and duty cycle (TI/total time of the respiratory cycle) remained unchanged. The decrease in Pessw and the increase in VT were associated with lower exertional dyspnea after EXT; (4) at standardized E, VT, RR, and IC, Pessw and Pessw(%Pessn)/VT remained unchanged while exertional dyspnea and leg effort decreased with EXT. CONCLUSION: In conclusion, increases in NMC, aerobic capacity, and tolerance to dyspnogenic stimuli and possibly breathing retraining are likely to contribute to the relief of both exertional dyspnea and leg effort after EXT.

Chest wall kinematics in patients with hemiplegia.

Owing to difficulties in measuring ventilation symmetry, good evidence of different right/left respiratory movements has not yet been provided. We investigated VT differences between paretic and healthy sides during quiet breathing, voluntary hyperventilation, and hypercapnic stimulation in patients with hemiparesis. We studied eight patients with hemiparesis and nine normal sex- and age-matched subjects. Right- and left-sided VT was reconstructed using optoelectronic plethysmography. In control subjects, no asymmetry was found in the study conditions. VTs of paretic and healthy sides were similar during quiet breathing, but paretic VT was lower during voluntary hyperventilation in six patients and higher during hypercapnic stimulation in eight patients (p = 0.02). The ventilatory response to hypercapnic stimulation was higher on the paretic than on the healthy side (p = 0.012). In conclusion, hemiparetic stroke produces asymmetric ventilation with an increase in carbon dioxide sensitivity and a decrease in voluntary ventilation on the paretic side.

Inspiratory capacity and decrease in lung hyperinflation with albuterol in COPD.

STUDY OBJECTIVES: Inspiratory capacity (IC) has been proposed as a simple method to assess acute changes in functional residual capacity (FRC) with bronchodilation, assuming that total lung capacity (TLC) is unchanged. This assumption is based on studies using body plethysmography, which may not accurately measure TLC in severely obstructed subjects. The aim of this study is to validate the use of IC measured by optoelectronic plethysmography (OEP) [ICOEP], a noninvasive technique capable of computing changes in absolute lung volumes with great accuracy. MEWTHODS AND MEASUREMENTS: We studied 13 subjects with COPD in clinically stable condition at baseline and after 200 microg of inhaled albuterol. Changes in lung volumes were obtained from changes in chest wall volume (Vcw) measured by OEP and were compared with those measured by standard techniques. RESULTS: Albuterol treatment caused a small but significant increase in FEV(1) and FVC, a significant decrease of Vcw at FRC (VcwFRC), but no changes of Vcw at TLC (VcwTLC) and breathing pattern variables. The reduction of VcwFRC was not correlated with either spirometric or breathing-pattern variables. IC measured with a pneumotachograph was highly correlated with and not significantly different from ICOEP (p < 0.001). CONCLUSIONS: A single dose of inhaled albuterol does not significantly modify VcwTLC in subjects with COPD, thus validating the use of IC to measure changes of FRC in the assessment of reversibility of airway obstruction.

Dissociation between respiratory effort and dyspnoea in a subset of patients with stroke.

Dyspnoea is not a prominent complaint of resting patients with recent hemispheric stroke (RHS). We hypothesized that, in patients with RHS presenting abnormalities in respiratory mechanics, increased respiratory motor output could translate into an increased perception of dyspnoea. We studied eight wheelchair-bound patients with RHS (mean age 62.4 years), previously evaluated by computerized tomography scanning, and a control group of normal subjects, matched for age and sex. We assessed routine spirometry, inspiratory and expiratory muscle pressures, breathing pattern and dyspnoea using a modified Borg scale. In six patients, we also measured oesophageal pressure during the maximal sniff manoeuvre and tidal inspiratory swing, and mechanical characteristics of the lung in terms of dynamic elastance during both quiet breathing and a hypercapnic/hyperoxic rebreathing test. During room air breathing, ventilation and tidal volume were similar in patients and controls, while tidal inspiratory swings of oesophageal pressure, an index of inspiratory motor output, were greater in patients ( P =0.005). Patients also exhibited a greater dynamic elastance ( P =0.013). During rebreathing, dynamic elastance remained higher ( P =0.01) and a greater than normal inspiratory motor output was found ( P =0.03). Responses of ventilation and tidal volume to carbon dioxide tension were normal, and in all patients but one a lower Borg score for the unit change in carbon dioxide tension and ventilation was found. In conclusion, a higher than normal inspiratory motor output was unexpectedly associated with a blunted perception of dyspnoea in this subset of RHS patients. This is likely to be due to the modulation of the integration process of respiratory sensation.