Biomedical subjects

F Maltais

Publications and source records attributed to F Maltais.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Local exercise and oxidative stress in chronic obstructive broncho-pneumopathies: preliminary results].

UNLABELLED: The role of altered peripheral muscle function in exercise intolerance of chronic obstructive pulmonary disease (COPD) is now well established. However, the mechanisms underlying this phenomen, have not been determined. One hypothesis is that the oxidative stress, that leads to tissue injury may be involved. A recent study has shown that general exercise caused systemic oxidative stress in COPD patients. However, the origin of this stress was not absolutely clear: airways, muscle, both, or other? The aim of this study was first to determine with a systemic approach, whether systemic oxidative stress occur in patients who perform local exercise and then with a muscular needle biopsy approach, to confirm the muscular origin of this oxidative stress. METHODS: In each approach, 7 COPD patients moderate to severe and 7 age-matched subjects performed an endurance test consisting of dynamic strength of the quadriceps against 40% (systemic approach) or 30% (biopsy approach) of maximal voluntary strength at an imposed regular pace until exhaustion. RESULTS: The results showed in each approach, that endurance test duration was significantly decreased in the COPD patients (p < 0.05). In systemic approach, the results showed that blood vitamin E at rest was significantly decreased in the COPD (p < 0.001), with a significant increase in superoxide anion release by stimulated phagocytes (p < 0.001). Local exercise induced, only in COPD, a significant increase in serum MDA (p < 0.05), which is an index of oxidative stress. In the biopsy approach, the results showed that local exercise induced in COPD an increase in muscular levels of MDA. A significant increase in muscular peroxidase glutathion activity (antioxidant) occurred after exercise only in normal subjects (p < 0.05). In conclusion, this study in COPD, confirms the altered peripheral muscle function, reveals a deficit in blood vitamin E and suggest that local muscular exercise causes a muscular oxidative stress in these patients. Further studies are needed to confirm these results and evaluate the implication of this oxidative stress in the myopathy of COPD.

Aged↗

PubMed2000

Peripheral muscle dysfunction in chronic obstructive pulmonary disease.

Peripheral muscle dysfunction is a common systemic complication of moderate to severe COPD and may contribute to disability, handicap, and premature mortality. In contrast to the lung impairment, which is largely irreversible, peripheral muscle dysfunction is potentially remediable with exercise training, nutritional intervention, oxygen, and anabolic drugs. Therapeutic success is often incomplete, however, and a better understanding of the mechanisms involved in the development of peripheral muscle dysfunction in COPD is needed to help develop innovative and more effective therapeutic strategies.

Aging↗

PubMed2000

Influence of work rate incremental rate on the exercise responses in patients with COPD.

PURPOSE: The peak work rate (Wpeak) measured during a progressive stepwise exercise test is commonly used to select the target training intensity for an exercise training program. In healthy subjects, a greater Wpeak is achieved when a faster rate of increase in work rate is used, whereas VO2 peak is independent of the rate of increase in work rate. This effect might be even more pronounced in chronic obstructive pulmonary disease (COPD) patients, in whom the VO2 kinetics during exercise are slower compared with healthy subjects. METHODS: To investigate this, we studied 10 COPD patients (9 M/1 F, age: 65+/-5 yr [mean +/- SD], FEV1: 33+/-8%). They underwent, on separate days, three stepwise exercise tests on an ergocycle. For each test, increments of 5, 10, or 20 W x min(-1) were used in random order; the investigator was blinded as to which increment was used. VO2, VCO2, heart rate (HR), minute ventilation (VE), breathlessness and leg fatigue at rest, at each work rate, and at maximal capacity were obtained. RESULTS: Wpeak averaged 40+/-13, 53+/-14, and 66+/-19 W for the 5-, 10-, and 20-W protocol, respectively (P < 0.001), whereas VO2 peak was comparable at 0.96+/-0.16, 1.02+/-0.18, and 1.03+/-0.20 L x min(-1). As the rate of increase in work rate became faster, the VO2/work rate relationship shifted to the right. This is exemplified by the VO2 at 40 W, which averaged 0.98+/-0.06, 0.90+/-0.09, and 0.83+/-0.10 L x min(-1) for the 5-, 10-, and 20-W protocol, respectively (P < 0.05). Similar observations were made for the relationship between HR, VE, and symptom scores, and work rate. There was no significant differences in peak values for HR and VE, and symptoms scores. CONCLUSIONS: We conclude that the work rate incremental rate influences the Wpeak achieved, whereas the peak values for VO2, HR, VE, and symptom scores remain comparable. These findings have practical implications for the exercise evaluation of patients with COPD.

Adaptation, Physiological↗

PubMed2000

Oxidative enzyme activities of the vastus lateralis muscle and the functional status in patients with COPD.

BACKGROUND: Enzymatic and histochemical abnormalities of the peripheral muscle may play a role in exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). A study was undertaken to measure the mitochondrial enzyme activity of the vastus lateralis muscle in patients with COPD and to evaluate the relationship between enzyme activities and functional status. METHODS: Fifty seven patients with COPD of mean (SD) age 66 (7) years with forced expiratory volume in one second (FEV(1)) 39 (15)% predicted and peak oxygen uptake (VO(2)) of 14 (4) ml/min/kg and 15 normal subjects of similar age were included in the study. Each subject performed a stepwise exercise test up to maximal capacity during which five-breath averages of VO(2) were measured. Muscle specimens were obtained by percutaneous needle biopsy of the vastus lateralis muscle and the activity of two mitochondrial enzymes (citrate synthase (CS) and 3-hydroxyacyl CoA dehydrogenase (HADH)) was measured. The functional status of the patients was classified according to peak VO(2). RESULTS: CS and HADH activities were markedly reduced in patients with COPD compared with normal subjects (22.3 (2.7) versus 29.5 (7.3) micromol/min/g muscle (p<0.0001) and 5. 1 (2.0) versus 6.7 (1.9) micromol/min/g muscle (p<0.005), respectively). The activity of CS decreased progressively with the deterioration in the functional status while that of HADH was not related to functional status. Using a stepwise regression analysis, percentage predicted functional residual capacity (FRC), the activity of CS, oxygen desaturation during exercise, age, and inspiratory capacity (% pred) were found to be significant determinants of peak VO(2). The regression model explained 59% of the variance in peak VO(2) (p<0.0001). CONCLUSIONS: The oxidative capacity of the vastus lateralis muscle is reduced in patients with moderate to severe COPD compared with normal subjects of similar age. In these individuals the activity of CS correlated significantly with peak exercise capacity and independently of lung function impairment.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1999

Altered expression of myosin heavy chain in the vastus lateralis muscle in patients with COPD.

This study was designed to further characterize peripheral skeletal muscle alterations in patients with chronic obstructive pulmonary disease (COPD) and to evaluate the possible relationship between myosin heavy chain (MyoHC) isoform expression and exercise tolerance in these individuals. MyoHC composition from biopsy of the vastus lateralis muscle was examined in 12 COPD patients (forced expiratory volume in one second (FEV1)=31+/-9% predicted, peak oxygen consumption (V'O2)=15+/-4 mL x kg(-1) x min(-1)) and 10 age-matched normal male subjects (peak V'O2=20+/-5 mL x kg(-1) x min(-1)). The proportion of MyoHC type I was smaller in COPD than in normals (27+/-17% versus 41+/-9%, p<0.05) with an increase in MyoHC type IIa (51+/-15% versus 39+/-9%, p<0.05) and the proportion of MyoHC type IIx being comparable between both groups. A significant relationship was found between peak V'Oo2 mL x kg(-1) x min(-1) and FEV1 % pred (r=0.91, p<0.0001) and the percentage of MyoHC type I (r=0.61, p=0.016). In stepwise multiple regression, only FEV1 % pred was found to be a significant determinant of peak V'O2 (p<0.0001). This variable explained 83% of the total variance of peak V'O2. In summary, this study showed considerable modifications in the phenotypic expression of the myosin heavy chain in the vastus lateralis muscle in patients with chronic obstructive pulmonary disease. An independent effect of myosin heavy chain expression on exercise capacity was not found. These results suggest that chronic inactivity and muscle deconditioning may not be the sole factors explaining peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease.

Aged↗

PubMed1999

Aerobic and strength training in patients with chronic obstructive pulmonary disease.

The purpose of this study was to evaluate whether strength training is a useful addition to aerobic training in patients with chronic obstructive pulmonary disease (COPD). Forty-five patients with moderate to severe COPD were randomized to 12 wk of aerobic training alone (AERO) or combined with strength training (AERO + ST). The AERO regimen consisted of three weekly 30-min exercise sessions on a calibrated ergocycle, and the ST regimen included three series of eight to 10 repetitions of four weight lifting exercises. Measurements of peripheral muscle strength, thigh muscle cross-sectional area (MCSA) by computed tomographic scanning, maximal exercise capacity, 6-min walking distance (6MWD), and quality of life with the chronic respiratory questionnaire were obtained at baseline and after training. Thirty-six patients completed the program and constituted the study group. The strength of the quadriceps femoris increased significantly in both groups (p < 0.05), but the improvement was greater in the AERO + ST group (20 +/- 12% versus 8 +/- 10% [mean +/- SD] in the AERO group, p < 0.005). The thigh MCSA and strength of the pectoralis major muscle increased in the AERO + ST group by 8 +/- 13% and 15 +/- 9%, respectively (p < 0.001), but not in the AERO group (3 +/- 6% and 2 +/- 10%, respectively, p > 0.05). These changes were significantly different in the two study groups (p < 0.01). The increase in strength of the latissimus dorsi muscle after training was modest and of similar magnitude for both groups. The changes in peak exercise work rate, 6MWD, and quality of life were comparable in the two groups. In conclusion, the addition of strength training to aerobic training in patients with COPD is associated with significantly greater increases in muscle strength and mass, but does not provide additional improvement in exercise capacity or quality of life.

Aged↗

PubMed1998

Histochemical and morphological characteristics of the vastus lateralis muscle in patients with chronic obstructive pulmonary disease.

PURPOSE AND METHODS: In this study, we examined the fiber-type proportions, cross-sectional areas (CSA), and capillarization from needle biopsies of the vastus lateralis muscle in 20 patients with chronic obstructive pulmonary disease (COPD) (FEV1 = 37 +/- 11% predicted, peak VO2 = 13 +/- 4 mL.min-1.kg-1) and nine age-matched normal subjects (peak VO2 = 33 +/- 7 mL.min-1.kg-1). The effects of endurance training on these parameters were also evaluated in 11 of the 20 patients with COPD. RESULTS: The proportion of Type I fiber was smaller in COPD than normals (34 +/- 14% vs 58 +/- 16 in normals, P < 0.0005) with a corresponding increase in Type IIb fiber (P = 0.015). The CSA of Type I, IIa, and IIab fibers was also smaller in COPD. The capillary to fiber ratio tended to be reduced in patients, but this difference did not reach statistical significance (P = 0.15). The number of capillary contact for Type I, IIa, and IIab fibers was significantly reduced in COPD compared with normal subjects (P < 0.05). When corrected for the CSA, this parameter was similar for both groups. After training, peak VO2 increased by 11% (P < 0.05), the fiber-type proportion remained unchanged, and the CSA of Type I and IIa fibers increased by 31 and 21%, respectively (P < 0.05). Although the number of capillary contact for each fiber types increased with training, the capillary to fiber ratio and the number of capillary contact for the different fiber types relative to their CSA remain unchanged. CONCLUSIONS: We conclude that in COPD, 1) the vastus lateralis muscle is characterized by a marked decrease in Type I fiber proportion, an increase in Type IIb fiber proportion, a decrease in Type I, IIa, and IIab fiber CSA and by a relatively preserved capillarization; and 2) a 12-wk training program induces a significant increase in Type I and IIa CSA.

Aged↗

PubMed1998

Metabolic and hemodynamic responses of lower limb during exercise in patients with COPD.

Premature lactic acidosis during exercise in patients with chronic obstructive pulmonary disease (COPD) may play a role in exercise intolerance. In this study, we evaluated whether the early exercise-induced lactic acidosis in these individuals can be explained by changes in peripheral O2 delivery (O2). Measurements of leg blood flow by thermodilution and of arterial and femoral venous blood gases, pH, and lactate were obtained during a standard incremental exercise test to capacity in eight patients with severe COPD and in eight age-matched controls. No significant difference was found between the two groups in leg blood flow at rest or during exercise at the same power outputs. Blood lactate concentrations and lactate release from the lower limb were greater in COPD patients at all submaximal exercise levels (all P < 0.05). Leg D02 at a given power output was not significantly different between the two groups, and no significant correlation was found between this parameter and blood lactate concentrations. COPD patients had lower arterial and venous pH at submaximal exercise, and there was a significant positive correlation between venous pH at 40 W and the peak O2 uptake (r = 0.91, P < 0.0001). The correlation between venous pH and peak O2 uptake suggests that early muscle acidosis may be involved in early exercise termination in COPD patients. The early lactate release from the lower limb during exercise could not be accounted for by changes in peripheral O2. The present results point to skeletal muscle dysfunction as being responsible for the early onset of lactic acidosis in COPD.

Acidosis, Lactic↗

PubMed1998

Peripheral muscle weakness in patients with chronic obstructive pulmonary disease.

Peripheral muscle weakness is commonly found in patients with chronic obstructive pulmonary disease (COPD) and may play a role in reducing exercise capacity. The purposes of this study were to evaluate, in patients with COPD: (1) the relationship between muscle strength and cross-sectional area (CSA), (2) the distribution of peripheral muscle weakness, and (3) the relationship between muscle strength and the severity of lung disease. Thirty-four patients with COPD and 16 normal subjects of similar age and body mass index were evaluated. Compared with normal subjects, the strength of three muscle groups (p < 0.05) and the right thigh muscle CSA, evaluated by computed tomography (83.4 +/- 16.4 versus 109.6 +/- 15.6 cm2, p < 0.0001), were reduced in COPD. The quadriceps strength/thigh muscle CSA ratio was similar for the two groups. The reduction in quadriceps strength was proportionally greater than that of the shoulder girdle muscles (p < 0.05). Similar observations were made whether or not patients had been exposed to systemic corticosteroids in the 6-mo period preceding the study, although there was a tendency for the quadriceps strength/thigh muscle CSA ratio to be lower in patients who had received corticosteroids. In COPD, quadriceps strength and muscle CSA correlated positively with the FEV1 expressed in percentage of predicted value (r = 0.55 and r = 0. 66, respectively, p < 0.0005). In summary, the strength/muscle cross-sectional area ratio was not different between the two groups, suggesting that weakness in COPD is due to muscle atrophy. In COPD, the distribution of peripheral muscle weakness and the correlation between quadriceps strength and the degree of airflow obstruction suggests that chronic inactivity and muscle deconditioning are important factors in the loss in muscle mass and strength.

Aged↗

PubMed1998

The diaphragm in emphysema.

Because of hyperinflation, the diaphragm of emphysematous patients operates at a disadvantageous position which affects its mechanical arrangement, modifies the configuration of its zone of apposition, increases its radius of curvature, and decreases its muscle fiber length below optimal configuration. The diaphragm in emphysema therefore displays a suboptimal configuration limiting its ability to function properly but shows no inherent structural insufficiency, unless its contractility is impaired by significant arterial blood gas anomalies or severe malnutrition. The demand imposed on the diaphragm in emphysema is increased by both hyperinflation and air-flow obstruction. With altered performance of the diaphragm and increased demand, force reserve is diminished and diaphragmatic fatigue may occur; this imbalance is targeted in some treatment modalities of emphysema such as pulmonary rehabilitation programs and lung volume reduction surgery.

Biomechanical Phenomena↗

PubMed1997

Intensity of training and physiologic adaptation in patients with chronic obstructive pulmonary disease.

The applicability of high-intensity training and the possibility of inducing physiologic adaptation to training are still uncertain in patients with severe chronic obstructive pulmonary disease (COPD). The purposes of this study were to evaluate the proportion of patients with moderate to severe COPD in whom high-intensity exercise training (30-min exercise session at 80% of baseline maximal power output [Wmax]) is feasible, and the response to training in these patients. We also sought to evaluate the possible influence of disease severity on the training intensity achieved and on the development of physiologic adaptation following endurance training. Forty-two patients with COPD (age = 66 +/- 7 yr, FEV1 = 38 +/- 13% predicted, [mean +/- SD]) were evaluated at baseline and after a 12-wk endurance training program. Each evaluation included a stepwise exercise test on an ergocycle up to the individual maximal capacity during which minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), and arterial lactic acid concentrations were measured. The training consisted of 25 to 30-min exercise sessions on a calibrated ergocycle three times a week, with a target training intensity at 80% of Wmax. The training intensity was adjusted with the objective of reaching the target intensity, but also to ensure that the cycling exercise could be maintained for the specified duration. The training intensity sustained for the duration of each exercise session averaged 24.5 +/- 12.6, 51.7 +/- 17.4, 63.8 +/- 22.4, and 60.4 +/- 22.7% of Wmax at Weeks 2, 4, 10, and 12, respectively. High-intensity training was achieved in zero, three, five, and five patients at Weeks 2, 4, 10, and 12, respectively. A significant increase in VO2max and Wmax occurred with training (p < 0.0002). This improvement in exercise capacity was accompanied by a 6% and 17% reduction in VE and in arterial lactic acid concentration for a given work rate, respectively (p < 0.0001), suggesting that physiologic adaptation to training occurred. The intensity of training achieved, in % Wmax, was not influenced by the initial VO2max, age, or FEV1. The effects of training were compared in patients with an FEV1 > or = 40% or < 40% predicted. Percent changes in VO2max, Wmax, and VE, were significant and of similar magnitude for both groups, whereas the decrease in arterial lactic acid for a given work rate reached statistical significance only in those patients with an FEV1 > or = 40% predicted. We conclude that although most patients were unable to achieve high-intensity training as defined in this study, significant improvement in their exercise capacity was obtained and physiologic adaptation to endurance training occurred. The training intensity expressed as a percent of the individual maximum exercise capacity, and the relative effectiveness of training, were not influenced by the severity of airflow obstruction.

Adaptation, Physiological↗

PubMed1996

Oxidative capacity of the skeletal muscle and lactic acid kinetics during exercise in normal subjects and in patients with COPD.

Early lactic acidosis during exercise and abnormal skeletal muscle function have been reported in chronic obstructive pulmonary disease (COPD) but a possible relationship between these two abnormalities has not been evaluated. The purpose of this study was to compare and correlate the increase in arterial lactic acid (La) during exercise and the oxidative capacity of the skeletal muscle in nine COPD patients (age = 62 +/- 5 yr, mean +/- SD, FEV1 40 +/- 9% of predicted) and in nine normal subjects of similar age (54 +/- 3 yr). Following a transcutaneous biopsy of the vastus laterialis, each subject performed a stepwise exercise test on an ergocycle up to his or her maximal capacity during which 5-breath averages of oxygen consumption (Vo2), and serial La concentration measurements were obtained. From the muscle biopsy specimen, the activity of two oxidative enzymes, citrate synthase (CS) and 3-hydroxyacyl CoA dehydrogenase (HADH), and of three glycolytic enzymes, lactate dehydrogenase, hexokinase, and phosphofructokinase were determined. The La/Vo2 relationship during exercise was fitted by an exponential function in the form La = a + bvo2, where be represents the shape of the relationship. The activity of the oxidative enzymes was significantly lower in COPD than in control subjects (22.8 +/- 3.3 versus 36.8 +/- 8.6 mumol/min/g muscle for CS, and 3.1 +/- 1.1 versus 5.5 +/- 1.4 mumol/min/g for HADH, p < 0.0005) and the increase in lactic acid was steeper in COPD (b = 4.3 +/- 2.0 versus 2.1 +/- 0.2 for normal subjects, p = 0.0005). A significant inverse relationship was found between CS, HADH, and b. No difference was found between the two groups for the glycolytic enzymes. We conclude that in COPD the increase in arterial La during exercise is excessive, the oxidative capacity of the skeletal muscle is reduced, and that these two results are interrelated.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1996

Skeletal muscle adaptation to endurance training in patients with chronic obstructive pulmonary disease.

The purpose of this study was to evaluate the physiologic responses to endurance training in patients with moderate to severe airflow obstruction by specifically looking at changes in skeletal muscle enzymatic activities. Eleven patients (age = 65 +/- 7 yr, mean +/- SD, FEV1 = 36 +/- 11% of predicted value, range = 24 to 54%) were evaluated before and after an endurance training program. Each evaluation included a percutaneous biopsy of the vastus lateralis and a stepwise exercise test on an ergocycle up to his/her maximal capacity. VE, VO2, VcO2, and serial arterial lactic acid concentration were measured during the exercise test. The activity of two oxidative enzymes, citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HADH), and of three glycolytic enzymes, lactate dehydrogenase, hexokinase, and phosphofructokinase was determined. The training consisted of 30-min exercise sessions on a calibrated ergocycle, 3 times a week for 12 wk. The aerobic capacity was severely reduced at baseline (VO2max = 54 +/- 12% of predicted) and increased by 14% after training (p < 0.05). For an identical exercise workload, there was a significant reduction in VE (34.5 +/- 10.0 versus 31.9 +/- 9.0 L/min, p < 0.05) and in arterial lactic acid concentration (3.4 +/- 1.3 versus 2.8 +/- 0.9 mmol/L, p < 0.01) after training. The lactate threshold also increased after training (p < 0.01) while the activity of the three glycolytic enzymes was similar at the two evaluations. In contrast, the activity of CS and HADH increased significantly after training (22.3 +/- 3.5 versus 25.8 +/- 3.8 mumol/min/g muscle for CS, p < 0.05, and 5.5 +/- 2.9 versus 7.7 +/- 2.5 mumol/min/g for HADH, p < 0.01). A significant inverse relationship was found between the percent changes in the activity of CS and HADH, and the percent changes in arterial lactic acid during exercise (p = 0.01). We conclude that endurance training can reduce exercise-induced lactic acidosis and improve skeletal muscle oxidative capacity in patients with moderate to severe chronic obstructive pulmonary disease (COPD).

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1996

A randomized, double-blind, placebo-controlled study of lorazepam as premedication for bronchoscopy.

To our knowledge, no study has clearly demonstrated the advantage of sedative premedication for bronchoscopy. In a double-blind study, we evaluated the efficacy of oral lorazepam as premedication for bronchoscopy. One hundred patients were randomly assigned to receive placebo (group A) or lorazepam (2 mg) (group B) approximately 1.5 h before bronchoscopy. Immediately after the procedure and the following day, a questionnaire addressing the patient's perception of the procedure was administered. Specifically, subjects were asked to grade the bronchoscopy as very easy, easy, difficult, or very difficult to tolerate and if they would agree to a second bronchoscopy if believed necessary. In addition, their recollection of the procedure was graded as clear, indistinct, or not at all. No difference was found between the two groups for age, duration of the bronchoscopy, and the answers to the questionnaire administered immediately after the procedure. Most patients from both groups found their level of sedation adequate. On the following day, however, group B reported with lower frequency that the technique was difficult or very difficult (38.0% vs 65.3% for group A; p < 0.005) and that they would be less reluctant to a repeated bronchoscopy (30.0% vs 57.1% for group A; p < 0.015). Moreover, their recollection of the procedure was now less precise than for those who had received the placebo (p < 0.005). This suggests that the difference observed between the two groups at 24 h was related to the amnesic effect of lorazepam. We conclude that lorazepam, by improving patient's perception of the bronchoscopy, is a useful premedication and may facilitate patient's investigation when a second bronchoscopy becomes necessary.

Bronchoscopy↗

PubMed1995

Pressure support reduces inspiratory effort and dyspnea during exercise in chronic airflow obstruction.

Exercise training has been of limited success in patients with severe chronic airflow obstruction (CAO), in part because of the reduced ventilatory capacity and excessive dyspnea experienced. Pressure support (PS) is a new form of mechanical ventilation which can effectively assist ventilation when applied noninvasively to patients in acute respiratory failure. It was hypothesized that PS might also be used to improve exercise performance, and ultimately physical conditioning, in ambulatory patients with CAO undergoing exercise training. To begin to address this concept, the objectives of the present study were (1) to examine the feasibility of providing PS to exercising patients with CAO and (2) to determine its effects on breathing pattern, inspiratory effort, and dyspnea. Flow and volume, mouth, esophageal, and gastric pressure were measured in seven patients with severe CAO (mean FEV1 = 0.75 +/- SEM 0.09 L) performing constant workload bicycle exercise (33 +/- 6 watts) during control conditions and with the application of PS (approximately 10 cm H2O). PS increased minute ventilation as a result of changes in both tidal volume and respiratory rate. This occurred despite marked reductions in inspiratory effort, as indicated by the pressure-time integrals of esophageal (68 +/- 5% control, p < 0.0005) and transdiaphragmatic pressure (52 +/- 8% control, p < 0.0005). Using a 5-point bidirectional scale to assess changes in dyspnea, breathlessness improved significantly with the addition of PS (2.3 +/- 0.6, p < 0.05) and worsened to a similar degree when it was removed (2.1 +/- 0.5, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Functional outcome of patients with chronic obstructive pulmonary disease and exercise hypercapnia.

Chronic hypercapnia is associated with a poor prognosis in chronic obstructive pulmonary disease (COPD). Some patients are normocapnic at rest but retain CO2 during exercise. The significance of this abnormality on the course of the disease is unknown. Sixteen stable COPD patients (13 males and 3 females, aged 60 +/- 5 yrs, mean +/- SD) who had previously undergone pulmonary function tests and progressive exercise testing with arterial blood sampling at rest and maximal capacity, entered the study. At first evaluation (E1), subjects were normocapnic at rest (arterial carbon dioxide tension (Pa,CO2): 4.9-5.7 kPa, (37-43 mmHg)) and all presented exercise-induced hypercapnia (end-exercise Pa,CO2 > 5.7 kPa (43 mmHg) with a minimal 0.5 kPa (4 mmHg) increase from resting value). The subjects were re-evaluated 24-54 months later (34 +/- 8 months) (second evaluation (E2)). At E2, forced expiratory volume in one second (FEV1) had decreased from 42 +/- 13 to 38 +/- 15% of predicted values, and mean resting Pa,CO2 had increased from 5.2 +/- 0.3 to 5.7 + 0.4 kPa. Maximal exercise capacity (Wmax) decreased between E1 and E2 from 76 +/- 30 to 56 +/- 22 W. Even if Wmax was lower at E2, end-exercise, Pa,CO2 was higher than at E1 (6.6 +/- 0.8 vs 6.4 +/- 0.5 kPa). At E2, eight subjects presented resting hypercapnia (group H), whilst the others remained normocapnic (Group N). Group H subjects had higher Pa,CO2, at Wmax than Group N and lower Wmax than Group N at E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗

PubMed1995

Efficacy of noninvasive CPAP in COPD with acute respiratory failure.

Dynamic hyperinflation and the development of intrinsic positive end-expiratory pressure (PEEPi) are commonly observed in patients with severe chronic obstructive pulmonary disease (COPD) in acute respiratory failure. Previous studies have shown that externally applied PEEP reduces PEEPi and its adverse effects in mechanically-ventilated COPD patients. The purpose of this study was to determine the effects of graded amounts of continuous positive airway pressure (CPAP) on the degree of inspiratory effort, pattern of breathing, gas exchange, and level of dyspnoea in a group of spontaneously breathing, nonintubated COPD patients in acute hypercapnic respiratory failure. Ten COPD patients admitted to the intensive care unit in acute hypercapnic respiratory failure were studied. Inspiratory effort was measured by the tidal excursions of oesophageal (Poes) and transdiaphragmatic (Pdi) pressure. Inspiratory effort and both the pressure-time product for the diaphragm (integral of Pdi-dt) and for the inspiratory muscles (integral of Poes.dt) were measured during the application of 5, 7.5, and 10 cmH2O of CPAP. Dyspnoea, gas exchange and pattern of breathing were also assessed. Inspiratory effort and the pressure-time product both for the diaphragm and the inspiratory muscles fell significantly with CPAP in a dose-dependent fashion. Both the pattern of breathing and level of dyspnoea improved with CPAP. End-expiratory lung volume remained stable at the lower levels of CPAP, with only modest increases at the higher levels. Arterial oxygen tension (Pa,O2) and arterial carbon dioxide tension (Pa,CO2) either improved or remained stable with CPAP. We conclude that the noninvasive application of CPAP to spontaneously breathing patients with severe COPD in acute respiratory failure decreases inspiratory effort and dyspnoea whilst improving breathing pattern. It is conceivable that the early institution of CPAP in this setting may obviate the need for intubation and conventional mechanical ventilation.

Adult↗

PubMed1995

Medical management of emphysema.

In summary, this article attempted to provide a framework for the elaboration of a stepcare medical management plan for patients with COPD. An algorithm describing this approach is presented in Figure 1. Inhaled ipratropium bromide and beta 2-agonist are both effective bronchodilators and may be sufficient in mild disease. For patients with persisting limitation in daily activities, various combinations of beta 2-agonist, ipratropium bromide, and theophylline may be used to potentiate the efficacy of the treatment. If this proves insufficient, a trial of oral corticosteroids can then be instituted. Only those individuals with a reduction in airflow obstruction after this therapy are candidates to receive either low-dose oral or low-dose inhaled corticosteroids in order to maintain the improvement. Inhaled corticosteroids are of no clinical benefit to patients with advanced COPD unresponsive to oral corticosteroids. Arterial blood gas should be analyzed in patients with a FEV1 less than 50% of predicted value and oxygen therapy prescribed according to the prescription guidelines. Pulmonary rehabilitation is indicated in patients with reduced functional status, despite adequate drug treatment.

Clinical Protocols↗