BACKGROUND:In patients with COPD, exercise intensity is often limited by the ventilatory system. We hypothesized that by exercising with a smaller muscle mass, ventilatory-limited patients would perform more high-intensity, muscle-specific work. The study objectives were as follows: (1) to determine the limitations of exercising with a smaller muscle mass, compared with conventional two-legged exercise; and (2) to determine the endurance time, using the same muscle-specific intensity, during one-legged vs two-legged exercise.METHODS:Nine patients (mean +/- SD FEV1, 36 +/- 13% of predicted) completed incremental exercise, and nine other patients (mean FEV1, 42 +/- 16% of predicted) completed constant-power exercise. Nine healthy subjects (FEV1, 104 +/- 14% of predicted) completed both tests. All subjects completed tests using two-legged and one-legged pedaling.RESULTS:Peak oxygen uptake (VO2peak) was similar during one-legged and two-legged incremental exercise among patients (difference, 0.03 L/min; 95% confidence interval [CI], -0.10 to 0.16 L/min; p = 0.60), as were ventilation and dyspnea scores. VO2peak was lower during one-legged vs two-legged exercise (-0.57 mL/min; 95% CI, -0.81 to -0.32 mL/min; p < 0.001) among healthy subjects with substantial ventilatory and heart rate reserve. Patients endured one-legged pedaling at a constant power longer than two-legged pedaling (16.97 min; 95% CI, 9.98 to 23.96 min; p < 0.001), resulting in greater work (12.48 kilojoules [kJ]; 95% CI, 2.58 to 22.39 kJ; p = 0.02). Healthy subjects completed similar work (-4.02 kJ; 95% CI, -18.59 to 10.55 kJ; p = 0.54) with one-legged vs two-legged pedaling.CONCLUSION:These observations demonstrate the effectiveness of using one-legged exercise at the same muscle-specific intensity in extending the duration of exercise among patients with COPD. This has important implications for training approaches designed to enhance exercise function among ventilatory-limited patients.

Although the influence of lung volume reduction surgery (LVRS) on incremental- and constant-power exercise is important in the evaluation of this procedure for patients with chronic obstructive pulmonary disease (COPD), it is rarely reported even in large randomised controlled trials. This report describes 39 patients with severe COPD ((mean +/- SE) forced expiratory volume in one second 32 +/- 2% pred, functional residual capacity 195 +/- 6% pred) who participated in a randomised controlled trial of LVRS and who completed incremental exercise tests at 6 months as well as endurance tests (constant power of 25 +/- 1 W) at 3, 9 and 12 months. Peak oxygen uptake (V'O2,pk) was similar between the treatment (n = 19) and control groups (n = 20) at baseline. After LVRS, the treatment group had a significantly greater V'O2,pk (mean difference (95% CI) 1.28 (0.07-2.50) mL x kg x min(-1)) and power (13 (6-20) W). The treatment group achieved a significantly greater minute ventilation (7.1 (2.9-11.3) L x min(-1)) with a greater tidal volume (0.16 (0.04-0.28) L). Baseline endurance was similar between groups. After surgery, there were significant between-group differences in endurance time, which were maintained at 12 months (7.3 (3.9-10.8) min). Lung volume reduction surgery is associated with an increase in exercise capacity and endurance, as compared with conventional medical treatment.

Background: The clinical value of LVRS has been questioned in the absence of trials comparing it with pulmonary rehabilitation, the prevailing standard of care in COPD. Patients with heterogeneous emphysema are more likely to benefit from volume reduction than those with homogeneous disease. Disease specific quality of life is a responsive interpretable outcome that enables health professionals to identify the magnitude of the effect of an intervention across several domains.Methods: Non-smoking patients aged < 75 years with severe COPD (FEV1 < 40% predicted, FEV1/FVC < 0.7), hyperinflation, and evidence of heterogeneity were randomised to surgical or control groups after pulmonary rehabilitation and monitored at 3 month intervals for 12 months with no crossover between the groups. The primary outcome was disease specific quality of life as measured by the Chronic Respiratory Questionnaire (CRQ). Treatment failure was defined as death or functional decline ( fall of 1 unit in any two domains of the CRQ). Secondary outcomes included pulmonary function and exercise capacity.Results: LVRS resulted in significant between group differences in each domain of the CRQ at 12 months ( change of 0.5 represents a small but important difference): dyspnoea 1.9 (95% confidence interval (CI) 1.3 to 2.6; p< 0.0001); emotional function 1.5 ( 95% CI 0.9 to 2.1; p< 0.0001); fatigue 2.0 ( 95% CI 1.4 to 2.6; p< 0.0001); mastery 1.8 ( 95% CI 1.2 to 2.5; p< 0.0001). In the control group one of 27 patients died and 16 experienced functional decline over 12 months. In the surgical group four of 28 patients died and three experienced functional decline ( hazard ratio = 3.1 ( 95% CI 1.3 to 7.6; p= 0.01). Between group improvements ( p< 0.05) in lung volumes, flow rates, and exercise were sustained at 12 months ( RV - 47% predicted ( 95% CI - 71 to - 23; p= 0.0002); FEV1 0.3 l ( 95% CI 0.1 to 0.5; p= 0.0003); submaximal exercise 7.3 min ( 95% CI 3.9 to 10.8; p< 0.0001); 6 minute walk 66 metres ( 95% CI 32 to 101; p= 0.0002).Conclusions: In COPD patients with heterogeneous emphysema, LVRS resulted in important benefits in disease specific quality of life compared with medical management, which were sustained at 12 months after treatment.

STUDY OBJECTIVE:Estimating lung volume using inspiratory capacity (IC) maneuvers is a useful way of tracking dynamic hyperinflation. An understanding of the repeatability of the IC in a clinical setting is important when evaluating an individual's response to a therapeutic intervention that might influence lung volume. This is the first study to determine the repeatability of serial IC measurements of patients with severe COPD undergoing incremental exercise testing in a clinical setting.SUBJECTS AND METHODS:Ten patients with severe COPD, inexperienced in exercise testing, cycled with power increased until they reached symptom limitation. Flow was measured at the mouth using a pneumotachograph. IC maneuvers were performed at 1-min to 3-min intervals. Subjects repeated the exercise test 2 days later. Three methods of calculating IC from flow have been described previously. To determine which method provided the best repeatability, we calculated the following: (1) IC calculated by the integration of inspired flow from the start to the end of the IC maneuver (ICINSP); (2) IC calculated from the difference between the drift-corrected peak inspiratory volume (total lung capacity [TLC]) and the drift-corrected end-expiratory lung volume (EELV) of the six breaths that preceded the IC prompt (ICREG); and (3) IC calculated, after correction of the expiratory part of the signal, as the difference between the mean EELV of the six breaths that preceded the IC prompt and the peak inspiratory volume (ICRATIO). Each individual's IC response was expressed as a function of exercise time and of ventilation.RESULTS:There was a significant (p < 0.05) decrease in the expired volume of the breath before the IC maneuver (0.11 +/- 0.26 L) [mean +/- SD]. ICINSP (1.78 +/- 0.88 L) was significantly less than the IC calculated using the other two methods (ICREG, 1.88 +/- 0.89 L; ICRATIO, 1.86 +/- 0.87 L). ICRATIO improved the repeatability of the serial IC measures by as much as 60% over ICINSP and ICREG.CONCLUSION:Calculating IC as the difference between EELV and TLC was unaffected by unsatisfactory technique, such as a change in breathing pattern immediately before the maneuver. Adjusting expiratory flow based on premaneuver inspiratory to expiratory volume ratio before estimating EELV improved the repeatability coefficient of the IC.

STUDY OBJECTIVE:This study determined whether proportional assist ventilation (PAV) applied during constant power submaximal exercise could enable individuals with severe but stable COPD to increase their exercise tolerance.DESIGN:Prospective controlled study having a randomized order of intervention.SETTING:Pulmonary function exercise laboratory.PARTICIPANTS:Ten subjects with severe stable COPD (mean [SD]: age=59 [6] years; FEV1=29 [7]% predicted; FEV1/FVC=33 [7]%; thoracic gas volume=201 [47]% predicted; diffusion of carbon monoxide=36 [10]% predicted; PaO2=76 [8] mm Hg; and PaCO2=41 [4] mm Hg).INTERVENTION:Each subject completed five sessions of cycling at 60 to 70% of their maximum power. The sessions differed only in the type of inspiratory assist: (1) baseline (airway pressure [Paw]=0 cm H2O); (2) proportional assist ventilation (PAV) (volume assist=6 [3] cm H2O/L, flow assist=3 [1] cm H2O/L/s); (3) continuous positive airway pressure (CPAP) (5 [2] cm H2O); (4) PAV+CPAP; and (5) sham (Paw=0 cm H2O).MEASUREMENTS AND RESULTS:Dyspnea was measured using a modified Borg scale. Subjects reached the same level of dyspnea during all sessions but only PAV+CPAP significantly (p<0.05) increased exercise tolerance (12.88 [8.74] min) vs the sham session (6.60 [3.12] min). Exercise time during the PAV and CPAP sessions was 7.10 [2.83] and 8.26 [5.54] min, respectively. Minute ventilation increased during exercise but only during PAV+CPAP was the end exercise minute ventilation greater than the unassisted baseline end exercise minute ventilation (36.2 [6.7] vs 26.6 [6.4] L/min, respectively; p<0.05).CONCLUSIONS:In this study, PAV+CPAP provided ventilatory assistance during cycle exercise sufficient to increase the endurance time. It is now appropriate to evaluate whether PAV+CPAP will facilitate exercise training.

STUDY OBJECTIVE The objective was to determine whether external chest wall oscillation (ECWO) during sleep (1) reduced spontaneous ventilation while maintaining adequate gas exchange over several hours, (2) influenced the quality and distribution of sleep, and (3) increased the number of respiratory events. DESIGN Prospective controlled study with counterbalanced order of intervention. SETTING Pulmonary function sleep laboratory. PARTICIPANTS Seven healthy volunteers. INTERVENTION One night of ECWO at 1 Hz (I:E = I:I; oscillation mean [SEM] from - 11.1 [0.7] to 6.0 [0.7] cm H2O) and a night during which the cuirass was applied without ECWO. MEASUREMENTS AND RESULTS ECWO resulted in a significant decrease in spontaneous minute ventilation (VE) in all stages of sleep. ECWO was associated with a reduction in the total sleep time and a reduction in rapid eye movement (REM) sleep. The number of stage changes and the sleep efficiency did not change significantly. The mean PCO2 was similar between the control and cuirass nights (44 to 46 mm Hg). There was a significant decrease in the mean PCO2 during stage 1 (41 [2] mm Hg) and stage 2 (42 [2] mm Hg) sleep during the ECWO night. The mean arterial oxygen saturation (SaO2) was maintained at 96 to 97% throughout sleep during the control, cuirass, and ECWO nights. The apnea + hypopnea index increased (p < 0.05) during ECWO mostly due to an increase in the number of hypopneas in stage 2 sleep. During ECWO, 18 of 30 respiratory events were associated with an arousal, whereas only 2 events were associated with an arousal during the control night. CONCLUSIONS ECWO can be tolerated for several hours and will assist ventilation while maintaining normal mean PCO2 and mean SaO2 during sleep. Monitoring of the apnea + hypopnea index and the SaO2 is recommended at the time of application. Clinical trials to define the most appropriate indications for ECWO are now necessary.

Effective gas exchange can be maintained in animals without the need for endotracheal intubation using external chest wall oscillation (ECWO). The clinical application of this technique has been limited by equipment which was either impractical or uncomfortable. We evaluated a prototype of a new oscillator in which an oscillatory profile of negative and positive pressure was imposed on a negative baseline pressure within a cuirass. In seven healthy subjects, we identified an oscillatory cuirass pressure that could effectively ventilate but would not result in severe hypocapnia over 5 min. We then measured the influence of changing the frequency of oscillation (fo) on PaCO2 and spontaneous ventilation. Lastly, we evaluated the capability of this prototype to achieve targeted changes in chamber pressure. Subjects were ventilated with an inspiratory chamber pressure of -20 +/- 4 cm H2O, an expiratory chamber pressure of 5 cm H2O and an inspiratory-expiratory ratio of 1:1 at 9 oscillatory frequencies (fo: 1 to 5 Hz at 0.5-Hz increments). Each subject was ventilated for 5 min with consecutive periods of ECWO being separated from each other by 10 min of unassisted breathing. Oscillatory tidal volume (Vo) was sampled and PaCO2 was determined from the expired carbon dioxide concentration (FECO2) measured at the mouth. The change in PaCO2 (delta PaCO2) was the difference in PaCO2 immediately before and after ECWO. We found that delta PaCO2 and Vo were inversely related to fo. At 1 Hz the delta PaCO2 was -13 +/- 1 mm Hg and Vo was 344 +/- 34 mL in the absence of spontaneous breathing (fb = 0). At 3 Hz and above, at the chamber pressures used, the delta PaCO2 was small (-1 to -2 mm Hg) and the Vo was less than the predicted dead space. Subjects breathed spontaneously but at a frequency below that of their resting fb. With this prototype, chamber pressure changes up to 30 cm H2O could be accurately achieved at 1, 2.5, and 4 Hz. In conclusion, ECWO can provide effective ventilation among healthy adults in the presence or absence of spontaneous breathing, and further studies are warranted to explore its effectiveness in a variety of clinical circumstances.

Although arm activity is poorly tolerated by patients with COPD, the ventilatory response to arm elevation alone is not well understood. We therefore studied the ventilatory response to arm elevation using a customized arm support sling to eliminate the effect of an increase in metabolic activity that might be attributable to independent arm elevation and used leg exercise to increase metabolic activity. During arm elevation at rest, there was a significant decrease in vital capacity (180 ml) and a small decrease in functional residual capacity (120 ml) as measured by body plethysmography. Minute ventilation was unchanged. When supported arm elevation (SAE) was compared with the control arm position (CAP), minute ventilation was unchanged although the pattern of breathing became more rapid and shallow (mean +/- SD, SAE vs CAP: fb = 17.9 +/- 5.3 vs 16.2 +/- 4.8 breaths.min-1; VT = 533 +/- 126 vs 579 +/- 142 ml; p < 0.05). During steady-state leg exercise, the increase in VO2, VCO2 and VE did not differ between SAE and CAP; however, both fb and VT changed toward a more rapid, shallow pattern of breathing (SAE vs CAP: fb = 24.3 +/- 3.0 vs 22.8 +/- 3.5 breaths.min-1; VT = 990 +/- 293 vs 1,081 +/- 309 ml; p < 0.05). During unsupported arm elevation VO2, VCO2, and VE, and fb were significantly greater than during the CAP. Approaches that train arm muscles and strategies that either support arm muscles or allow for frequent rests during upper arm activity may improve the endurance and the quality of life for COPD patients.

The purpose of this study was to determine whether there is a difference in respiratory mechanics and gas exchange between polio survivors and healthy, age-matched controls during wakefulness and sleep. Polio survivors were divided into four groups. The first group included those who had evidence of respiratory muscle involvement originally (PRM) and the second group included those who had bulbar muscle involvement originally (PBM). The third and fourth groups had only limb involvement originally but were separated by absence (PSL) or presence of a scoliosis (PSS) at the time of their evaluation. Each subject completed baseline and one year follow-up measurements of lung volumes, diffusion, flow rates, respiratory muscle strength, central and peripheral chemoreflexes and arterial blood gases. Sleep measurements included a full respiratory polysomnographic study. Fifty polio survivors and 13 controls completed the study. The PRM and PSS groups had an elevated arterial carbon dioxide tension (PaCO2) (mean +/- SE 6.0 +/- 0.4 and 6.0 +/- 0.3 kPa, respectively), reduced vital capacity (2.8 +/- 0.3 and 2.9 +/- 0.3 l, respectively), reduced maximal inspiratory pressure (-5.9 +/- 0.7 and -5.4 +/- 0.8 kPa, respectively) and reduced maximal expiratory pressure (9.8 +/- 1.1 and 9.1 +/- 1.2 kPa, respectively), when compared with non-polio controls. During sleep PRM and PSS groups experienced a higher PaCO2 (6.5 +/- 0.5 and 6.7 +/- 0.4 kPa, respectively) and a lower arterial oxygen saturation (SaO2) (89 +/- 4 and 86 +/- 3%, respectively). There were no differences among groups for diffusion, flow rates and chemoreflexes. All other polio survivors showed essentially normal respiratory function.(ABSTRACT TRUNCATED AT 250 WORDS)

Intermittent positive pressure ventilation reduces inspiratory muscle electromyographic activity among patients with restrictive ventilatory failure. It has therefore been suggested that the reduction of energy expenditure at night could result in improved inspiratory muscle function during the day. Reported successes with nocturnal ventilation have not included measurements of inspiratory muscle endurance. We therefore electively ventilated six (five female, one male) patients (mean +/- SD) aged 36 +/- 13 years in whom respiratory failure (room air PaCO2, 60 +/- 13 mm Hg; PaO2, 44 +/- 11 mm Hg; SaO2, 75 +/- 12 percent) was consequent on restrictive ventilatory disease (vital capacity, 25 +/- 7 percent predicted; FEV1/FVC, 81 +/- 12 percent; total lung capacity, 40 +/- 5 percent predicted; MIPRV -42 +/- 10 cm H2O; MEP, 81 +/- 28 cm H2O). Positive pressure ventilation was administered with a customized closely fitting nasal mask attached to a volume-cycled pressure-limited ventilator. Full respiratory polysomnographic measurements as well as arterial blood gases, pulmonary function, distance walked in six minutes, and inspiratory muscle endurance were measured at baseline and after 3 and 14 months of ventilation. Ventilation improved saturation (baseline on O2; SWS 87 +/- 10, REM 79 +/- 14, ventilator on R/A; SWS 90 +/- 6, REM 89 +/- 5 percent) and transcutaneous Pco2 (baseline on O2; SWS 85 +/- 26, REM 94 +/- 39, ventilator on R/A; SWS 53 +/- 9, REM 58 +/- 9 mm Hg). During ventilation, the quantity and distribution of sleep was similar to that observed prior to ventilation. Daytime gas exchange improved as did the six-minute walking test (initial test = 429 +/- 120 m, three months after ventilation = 567 +/- 121 m), both of these improvements being sustained at 14 months. Inspiratory muscle endurance measured using a pressure threshold load (mean mouth pressure = 45 percent MIPRV) improved from 7.1 +/- 3.4 minutes at baseline to 14.8 +/- 7.6 minutes at 3 months, an improvement sustained at 14 months. There was no change in measured lung volumes or respiratory muscle strength. We conclude that the improvement in nocturnal gas exchange, daytime functioning, and arterial blood gases resulting from nocturnal positive pressure ventilation is associated with an increase in inspiratory muscle endurance sustained at 14 months.