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PubMed1991

Use of factor analysis to consolidate multiple outcome measures in chronic obstructive pulmonary disease.

Multiple outcome measures are often used in clinical research and practice. However, the use of multiple measures inflates the probability of a type I error. In this paper, we used factor analysis techniques to reduce multiple outcome measures to a lesser number of orthogonal dimensions. The data were obtained from 119 patients with chronic obstructive pulmonary disease. Each patient had measurements made of 28 variables, including multiple parameters of pulmonary function, exercise tolerance and gas exchange. Factor analysis using a maximum likelihood iterative solution was performed. The factors were then rotated to a varimax solution. The analysis yielded four meaningful factors: exercise tolerance, disease severity, lung volumes and flow rates. Exercise tolerance and disease severity were the most important factors accounting, respectively, for 44 and 13% of the common variance. For further analyses, these composite factors could be used or a representative clinical measure from each factor might be chosen. We conclude that many physiologic measures provide highly correlated information about chronic obstructive pulmonary disease patients. Factor analysis may help reduce these measures into a smaller number of reliable composites.

Aged↗

PubMed2003

Longitudinal trends in exercise capacity and health status after pulmonary rehabilitation in patients with COPD.

Pulmonary rehabilitation (PR) programmes produce initial improvements in exercise tolerance and health status in patients with chronic obstructive pulmonary disease (COPD). However, there is limited data on the longer term effects of PR. This study has examined whether the initial benefits gained in exercise tolerance and health status may be maintained after a 1-year follow-up programme. Sixty-six patients with COPD were assessed with the MRC Dyspnoea Scale and found to be moderately disabled due to dyspnoea (MRC Grades 3 and 4). These patients were then randomised to an 8 week outpatient programme of either exercise training and education (Exercise group) or to education alone (Control group). Exercise performance was assessed with the shuttle walking test and health status assessed with two disease-specific measures, the St Georges Respiratory Questionnaire and the Chronic Respiratory Disease Questionnaire. After PR, all patients were invited to attend monthly follow-up sessions for 1 year. Fifty-six patients were available for follow-up immediately after the programme and were assessed at 6 months and 1 year. This study has shown that the patients in the Exercise group maintained improvements in exercise capacity and health status up to 6 months after an 8 week programme. At 1 year there was a significant difference between the Exercise and Control groups in terms of exercise tolerance due to a considerable decline experienced by the Control group. However, neither group had maintained improvements in health status at 1 year. Further study is required to assess whether benefit may be sustained for a longer period using alternative follow-up strategies.

Activities of Daily Living↗

PubMed1996

Impaired cardiac reserve and exercise capacity in patients receiving long-term thyrotropin suppressive therapy with levothyroxine.

To assess cardiac function and exercise tolerance in patients receiving long term TSH-suppressive therapy with levothyroxine (L-T4), we studied maximal exercise capacity with a bicycle ergometer and left ventricular function at rest and during physical exercise by radionuclide angiography. The evaluation was performed in 10 patients receiving L-T4 therapy (2.31 +/- 0.13 microgram/kg) for 5-9 yr, presenting with effort dyspnea and symptoms of adrenergic overactivity, and 10 matched control subjects. The patients were reassessed after 4 months of administration of the selective beta-adrenergic blocker bisoprolol (4.25 +/- 0.4 mg/day); L-T4 therapy remained unchanged. The results showed that at rest, left ventricular diastolic filling was impaired in the patients (P < 0.05), whereas systolic function was unaltered. During submaximal physical exercise, left ventricular ejection fraction increased in the controls from 58 +/- 2% to 65 +/- 2% (P < 0.001), whereas in the patients it fell from 63 +/- 2% to 53 +/- 2% (P < 0.01), mainly because of increased end-systolic left ventricular volume (P < 0.05). Exercise capacity was markedly reduced in the patients in terms of both peak workload (P < 0.001) and exercise duration (P < 0.001). beta-Adrenergic blockade prevented both the fall in ejection fraction and the increase in end-systolic volume during exercise, and improved exercise tolerance. In conclusion, our data show that long term TSH-suppressive therapy with L-T4 is not as harmless as believed, because it may cause marked impairment of cardiac functional reserve and physical exercise capacity. Administration of a beta-blocking drug for 4 months caused significant improvement of cardiac performance and exercise tolerance.

Adrenergic beta-Antagonists↗

PubMed1989

[The clinical significance of the low level treadmill exercise test in acute myocardial infarction].

To clarify the clinical significance of the exercise test in acute myocardial infarction (AMI), the relationship between the results of exercise test and clinical features was studied. The low level treadmill exercise test (maximum exercise time was 1080 seconds and the maximum oxygen consumption was 7 METs) were performed in 111 patients within 2 months after the onset of AMI. The exercise time, the endpoint of the exercise test, the exercise-induced ST-segment deviation and ventricular premature beats (VPC) were evaluated from the exercise tests. Among the clinical features, age, sex, the severity in the acute period (Killip's classification and Forrester's hemodynamic subset), the findings in cardioangiography (the number of diseased coronary arteries, left ventricular ejection fraction and abnormal wall motion in the left ventricle) and short term prognosis after AMI were evaluated. The prognosis was judged as poor when cardiac death, congestive heart failure, postinfarction angina, the decrease of exercise tolerance and reattack of AMI occurred, or when an aorto-coronary bypass graft or percutaneous transluminal coronary angioplasty was performed. The exercise time was shorter in patients over the age of 60 years (578 +/- 360 seconds) than in younger patients (818 +/- 296 seconds), and also in females (487 +/- 392 seconds) than in males (767 +/- 319 seconds). The patients classed as Forrester's hemodynamic subset IV had shorter exercise time than the others. But, there was no relationship between the exercise time and Killip's classification. Low left ventricular ejection fraction (55% or less) was associated with short exercise time and the apperance of exercise-induced VPC. But the number of diseased coronary artery and abnormal wall motion in the left ventricle were not related to the exercise test. The patients with high exercise tolerance (4.2 METs or more) in the AMI recovery period showed better prognosis than those with low exercise tolerance within one year after AMI (96% vs 50%, p less than 0.0001, respectively). In conclusion, the low level exercise test in AMI was influenced by age, sex and cardiac function, and it was useful in evaluating the short term prognosis after AMI.

Adult↗

PubMed1982

Oral isosorbide dinitrate in angina pectoris: comparison of duration of action an dose-response relation during acute and sustained therapy.

The effects of different oral doses of isosorbide dinitrate administered acutely and four times daily during sustained therapy were studied in 12 patients with angina pectoris. After administration of 30, 60 and 120 mg of isosorbide dinitrate, the average plasma concentrations were higher and the area under the plasma concentration time curve was greater during sustained than during acute therapy (p less than 0.01). Reduction in standing systolic blood pressure was greater during acute than during sustained therapy (p less than 0.001). This reduction in systolic blood pressure was dose-related and persisted for 8 hours during acute therapy, but was not dose-related and was demonstrable for only 4 hours during sustained therapy. Compared with placebo therapy, exercise duration to the onset of angina and to the development of moderate angina increased significantly after each dose of isosorbide dinitrate for 8 hours during acute therapy but for only 2 hours during sustained therapy. During acute therapy, administration of a single dose of 15 or 30 mg of isosorbide dinitrate produced similar improvement in exercise tolerance as did a dose of 60 or 120 mg. During sustained therapy (15 mg four times daily), exercise tolerance increased to the same magnitude as with doses of 30, 60 or 120 mg four times daily. In most patients, near maximal improvement in exercise tolerance occurred after a dose of 15 or 30 mg four times daily. It is concluded that during sustained therapy with isosorbide dinitrate, partial tolerance to the antianginal and circulatory effects develops rapidly.

Administration, Oral↗

PubMed1992

[Dyspnea at rest and after exercise and the mental status of patients with chronic obstructive lung diseases].

Thirty two patients with severe COPD were studied. We evaluated relationships between their psychological status, lung function parameters, exercises tolerance (6 MWD test) and dyspnea at rest and exercise (visual analogue scale). Patients demonstrated increased level of anxiety and psychological tension. In nearly half of the patients depression, low self-esteem and disbelief in the efficiency of therapy were observed. The correlations between the psychological status and the exercise tolerance hasn't been found. The correlation between the high level of depression and impairment of the lung function was found. The high increase in dyspnea score during exercises was connected with low self-esteem, although at rest the dyspnea level in those patients was low.

Adult↗

PubMed1993

Restoration of the pulmonary valve reduces right ventricular volume overload after previous repair of tetralogy of Fallot.

BACKGROUND: Severe pulmonary regurgitation (PR) and associated right ventricular (RV) dilatation are late complications of surgical repair of tetralogy of Fallot (TOF). For the past several years, we have restored pulmonary valve competence with the exclusive use of cryopreserved allografts. METHODS AND RESULTS: Sixteen patients with symptoms of diminished exercise tolerance and echocardiographic evidence of progressive PR with severe RV dilatation underwent placement of allografts in the RV outflow tract at a median age of 12 years (10 years after TOF repair). Abnormal exercise tolerance tests were documented in 10 patients. Additional surgical procedures included pulmonary artery augmentation (n = 6), closure of residual left to right shunts (n = 3), and subendocardial resection for monomorphic ventricular tachycardia (n = 1). Six patients had either preoperative or postoperative balloon dilations of pulmonary artery stenoses. All patients had symptomatic improvement after allograft insertion. At a mean follow-up of 26.4 +/- 3.4 months, the severity of PR improved in all but one patient. In 12 patients (group 1), conduit regurgitation was either trace (n = 11) or mild (n = 1). Four patients (group 2) had moderate conduit regurgitation. In a retrospective analysis, pulmonary artery diameters and cross-sectional areas were significantly smaller in the group 2 patients compared with the group 1 patients. With the exception of one patient, RV end-diastolic diameter (RVEDD/BSA) fell after allograft insertion in each patient (P < .01). The reduction in RVEDD/BSA was significantly greater in group 1 than in group 2 (31.8 +/- 3.4% versus 21.4 +/- 11.0%, P < .05). CONCLUSIONS: Thus, restoration of the pulmonary valve with cryopreserved allografts improved exercise tolerance and diminished RV volume overload in patients with severe PR after previous repair of TOF. Optimal results were achieved in patients who did not have significant residual pulmonary artery distortion.

Child↗

PubMed1991

Exercise performance and breathing patterns in cystic fibrosis: male-female differences and influence of resting pulmonary function.

Despite improved prognosis for patients with cystic fibrosis (CF), they continue to suffer from progressive decline in pulmonary function and exercise tolerance. Beyond puberty, female patients have greater loss of pulmonary function and higher mortality than males, yet no one has studied male-female differences in exercise tolerance among patients. We therefore compared the responses to progressive exercise in 58 male and 52 female patients with CF and analyzed the influence of resting pulmonary function and gender on these responses and on breathing patterns during exercise. Within each of three pulmonary function groups (group 1: FEV1 greater than or equal to 65% predicted; group 2: FEV1 = 50-64% predicted; and group 3: FEV1 less than 50% predicted), female patients had lower exercise tolerance than males. This was reflected in the overall group for each gender: males' peak work load was 130 +/- 64 W, females' 111 +/- 32 W (P = 0.04); males' peak oxygen consumption, 36.9 +/- 11.4 mL/kg/min and females', 31.0 +/- 7.4 mL/kg/min (P = 0.0006). There was no interactive effect between gender and pulmonary function. Neither respiratory rate nor tidal volume differed between sexes. Male and female patients, irrespective of disease severity, employed similar proportions of their ventilatory capacity at exhaustion; group mean minute ventilation to maximum voluntary ventilation ratio ranged from 62.9 to 78.3%, with no apparent relationship to disease severity.

Adolescent↗

PubMed1975

Heat tolerance of exercising lean and obese prepubertal boys.

Seven lean and five obese boys, aged 9-12 yr, exercised in four environments: 21.1, 26.7, 29.4, and 32.2 degrees C Teff. Subjects walked on a treadmill at 4.8 km/h, 5% grade for three 20-min exercise bouts separated by 5-min rest periods. Rectal temperature (Tre), skin temperature (Tsk), heart rate (HR), sweat rate, and oxygen uptake (VO2) were measured periodically throughout the session. Lean boys had lower Tre and HR than obese boys in each of the environments. Increases in Tre were significantly greater for the obese at 26.7 and 29.4 degrees C Teff. No significant differences in Tsk and sweat rate (g-m-2-h-1) were observed between lean and obese boys. Obese boys had significantly lower oxygen consumptions per kg but worked at a significantly higher percentage of VO2max than lean boys when performing submaximal work. Responses of the obese boys to exercise in the heat were similar to those of heavy prepubertal girls studied previously, except that the boys were more tolerant of exercise at 32.2 degrees C Teff than the girls. Lean boys had lower HR than lean girls in each environment, but lower Tre only at 32.2 degrees C Teff.

Adult↗

PubMedDate not supplied

Exercise testing early after myocardial infarction: historic perspective and current uses.

Exercise testing performed earlier than six weeks post-MI is accepted as "standard" medical practice. Although both heart rate-limited and symptom-limited exercise protocols are used with nearly equal frequency, the latter appears more valuable because the prognostic yield is greater without sacrificing patient safety. Treadmill or cycle ergometers are the preferred modes of testing because of higher exercise work loads imposed and increased sensitivity and specificity of results. The physiologic exercise responses to graded work loads among these acute MI survivors include a mean maximal heart rate range of 118 to 136 beats/min, a peak systolic blood pressure between 137 and 170 mmHg, a mean peak double product from 16,000 to 22,400, and a mean maximal work load between 4.8 and 7.0 METS. Exercise findings which are most clinically useful are greater than 1 mm ST segment depression from rest level, presence of angina pectoris during exercise, decrease in systolic blood pressure with increasing work, presence of complex or frequent VEBs, and exercise tolerance less than 4 METS. These exercise findings identify, in recent post-MI survivors, groups of patients that have significantly different estimated future cardiac morbidity and mortality rates. The most consistent indices of multi-vessel coronary heart disease are ST segment depression, angina pectoris, and poor exercise tolerance. The most important role of stress testing in this period post-MI is identification of individuals who urgently need evaluation for coronary bypass surgery. In addition to risk stratification, exercise testing provides valuable information regarding exercise prescription for cardiac rehabilitation, direct psychologic benefit for resuming an active lifestyle, and motivation for exercise participation. Although safety of the early post-MI stress test has not been systematically studied, reports from individual studies indicated low morbidity and mortality. Attesting to this is the frequency with which it is performed as a routine office procedure. Finally, there has been a growing use of this procedure not only among cardiologists but also among internists and family practice physicians.

Angina Pectoris↗

PubMed1997

Effect of extended-release isosorbide mononitrate one hour after dosing in patients with stable angina pectoris. IMDUR Study Group.

The effect of extended-release isosorbide mononitrate (ER-ISMN) on exercise tolerance 1 hour after dosing was compared with that of placebo in a multicenter, randomized, double-blind study of 151 patients with stable effort-induced angina. During a 9- to 24-day placebo run-in, patients underwent Bruce protocol baseline exercise tolerance tests, after which they received ER-ISMN or placebo for 5 days. ER-ISMN patients took 60 mg each morning for the first 4 days and 120 mg on the morning of the fifth day. One hour after dosing, ER-ISMN patients had a significantly greater increase in total exercise time (days 1 to 4: 5 +/- 53 seconds; day 5: 53 +/- 58 seconds) than the placebo-treated patients (days 1 to 4: 14 +/- 37 seconds; day 5: 21 +/- 48) (p <0.001). The times to development of angina and 1-mm ST-segment depression were significantly longer in the ER-ISMN group than in the placebo group. The difference between the groups in mean time to onset of angina was 34 seconds after the 60-mg dose (p = 0.004) and 49 seconds after the 120-mg dose (p <0.001). The mean time to development of a 1-mm ST-segment depression was 51 and 61 seconds longer after the 60-mg and 120-mg ER-ISMN doses, respectively, than after placebo (p <0.001). Treatment-related adverse events were reported in 37% (28 of 75) and 7% (5 of 76) of patients in the ER-ISMN and placebo groups, respectively. As expected, headache was more frequent in the ER-ISMN group than in the placebo group (28% and 1%, respectively). The effects of ER-ISMN (60 mg and 120 mg) are clinically evident 1 hour after dosing, resulting in better exercise tolerance in patients with angina pectoris.

Adult↗

PubMed1994

Dynamic leg exercise improves tolerance to lower body negative pressure.

Lower body negative pressure (LBNP) of 100 mm Hg generates a footward force approximating one body weight for most subjects, yet LBNP may also produce syncope by pooling blood in the lower body. We hypothesized that dynamic leg exercise would improve LBNP tolerance by reducing lower body fluid accumulation. Seven healthy male subjects underwent four supine LBNP tolerance tests: 1) the control condition: conventional, resting LBNP with a saddle (SADL); 2) resting LBNP against a footplate instead of a saddle (FP); 3) cyclic, non-load-bearing ankle plantar- and dorsiflexion movements during LBNP with a saddle (SADLEX); and 4) LBNP with cyclic ankle plantar- and dorsiflexion exercise against the footplate (FPEX). Tolerance tests consisted of reducing chamber pressure in 10 mm Hg decrements every 3 min to -100 mm Hg or presyncope. Tolerance was assessed by integrating the area under the LBNP x time step function. Exercise doubled LBNP tolerance relative to resting LBNP (SADL: 771 +/- 162 mm Hg x min; FP: 819 +/- 212; SADLEX: 1461 +/- 175; FPEX: 1656 +/- 160; p < 0.05). During FPEX, footward force oscillations averaged 215 +/- 14 N (21.9 +/- 1.4 kg), and mean peak force of 872 +/- 26 N (88.9 +/- 2.7 kg; n = 5) was produced by plantarflexing against 100 mm Hg LBNP. Calf volume increased slightly less when exercise accompanied LBNP (SADLEX and FPEX), while heart rate increased more. Therefore, exercise improved tolerance in part by skeletal muscle pumping of venous blood from the legs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2002

[Prognostic significance of treadmill stress-echocardiography in patients with ischemic heart disease].

Prognostic value of treadmill echocardiography was studied in 146 patients (125 men, 21 women, age 58,6-/+9 years) with overt or suspected ischemic heart disease. During 35-/+6 months of follow-up there were 26 cardiac events (11 cardiovascular deaths, 6 myocardial infarctions and 9 revascularization procedures). Independent predictors of events were presence of angina, maximal heart rate, and result of a stress test. Both exercise tolerance and echocardiographical signs of ischemia were related to development of events however the latter had better predictive power. Among patients with exercise tolerance below 7 METS with and without ischemia rates of events were 33 and 11%, respectively. Among patients with exercise tolerance above 7 METS with and without ischemia event rates were 23 and 6.8%, respectively.

Adult↗

PubMed2006

[Pilot experience in Russia with external contrapulsation in patients with coronary heart disease].

AIM: To examine effects of programmed external contrapulsation (ECP) on the clinico-functional status, quality of life (QOL) in patients with coronary heart disease (CHD), stable angina of FC II-IV resistant to medication. MATERIAL AND METHODS: Eighteen patients with CHD, stable angina of FC III-IV (2 females and 16 males, mean age 63.6 +/- 7.4 years) have completed a course of ECP including 35 one-hour procedures 5-6 times a week for 7 weeks. Ten patients had cardiac failure (NYHA FC II-III). Before and after ECP course the patients were examined using QOL assessment by Minnesota questionnaire, complex echo-cardiography, bicycle exercise test, perfusion myocardial scintigraphy with 99m-Tc-4,2-methoxy-isobutilisonitril, 24-h Holter ECG monitoring, enzyme immunoassay for plasma natriuretic propeptides. RESULTS: Significant subjective QOL improvement (p < 0.01) was noticed by all the patients. Anginal attacks and nitrates doses reduced at least 2-fold. Exercise tolerance rose significantly (p < 0.01), bicycle exercise test was positive in 5 patients, the rest stopped the test after achievement of submaximal heart rate (HR) and fatigue. Most of the patients exhibited improvement of myocardial perfusion. Patients with abnormal myocardial contractility showed a moderate trend (p < 0.03) to an increase in left ventricular ejection fraction. By 24-h ECG, mean HR diminished significantly (p < 0.02). CONCLUSION: ECP is highly effective and safe in combined therapy of CHD, stable angina resistant to drug therapy, in impossibility of myocardial revascularization, including patients with cardiac failure. This manifests in a significant abatement of angina, lower doses of nitrates, improvement of exercise tolerance, quality of life, myocardial perfusion and hemodynamic indices.

Coronary Angiography↗

PubMed2003

Intensity-dependent tolerance to exercise after attaining V(O2) max in humans.

The tolerable duration of high-intensity, constant-load cycle ergometry is a hyperbolic function of power, with an asymptote termed critical power (CP) and a curvature constant (W') with units of work. It has been suggested that continued exercise after exhaustion may only be performed below CP, where predominantly aerobic energy transfer can occur and W' can be partially replenished. To test this hypothesis, six volunteers each performed cycle-ergometer exercise with breath-by-breath determination of ventilatory and pulmonary gas exchange variables. Initially, four exercise tests to exhaustion were made: 1). a ramp-incremental and 2). three high-intensity constant-load bouts at different work rates, to estimate lactate (theta(L)) and CP thresholds, W', and maximum oxygen uptake (Vo2 max). Subsequently, subjects cycled to the limit of tolerance (for approximately 360 s) on three occasions, each followed by a work rate reduction to 1). 110% CP, 2). 90% CP, and 3). 80% theta(L) for a 20-min target. W' averaged 20.9 +/- 2.35 kJ or 246 +/- 30 J/kg. After initial fatigue, 110% CP was tolerated for only 30 +/- 12 s. Each subject completed 20 min at 80% theta(L), but only two sustained 20 min at 90% CP; the remaining four subjects fatigued at 577 +/- 306 s, with oxygen consumption at 89 +/- 8% Vo2 max. The results support the suggestion that replenishing W' after fatigue necessitates a sub-CP work rate. The variation in subjects' responses during 90% CP was unexpected but consistent with mechanisms such as reduced CP consequent to prior high-intensity exercise, variation in lactate handling, and/or regional depletion of energy substrates, e.g., muscle glycogen.

Adult↗

PubMed1995

Avoiding unsuspected respiratory side-effects of topical timolol with cardioselective or sympathomimetic agents.

Topical timolol given for the treatment or chronic simple glaucoma may cause unrecognised bronchospasm among elderly people. We recruited 80 patients aged over 60 years, who were without a history of airways disease and already used timolol, into a randomised crossover study comparing the effects on spirometry and exercise tolerance of changing to betaxolol or dipivefrine therapy. Results showed an increase of 13% and 8% in mean peak flow rate and forced expiratory volume in 1 s (FEV1), respectively, when using betaxolol; and of 14% and 11% when using dipivefrine. There was also improved exercise tolerance with both agents. More than a quarter of the patients showed at least a 15% improvement in FEV1 when changed from timolol. Analysis of enrolment symptoms and response to nebulised salbutamol failed to produce a method of identifying these patients. Timolol may impair respiratory function and exercise tolerance of elderly patients even if they have no history of reversible airways disease.

Aged↗

PubMed1992

Evaluation of respiratory function in health and disease.

From a conceptual standpoint, the tests of pulmonary function can be divided into those that assess the ventilatory function of the lungs and those concerned with gas exchange. Tests of ventilatory function reflect alterations of the elastic resistance and flow resistance of the respiratory apparatus. The elastic properties of the lungs are assessed by determining the position and shape of the curve representing the relationship between the pressure across the lungs and absolute lung volume. When there is reduced distensibility of either the lungs or the chest wall, the volume-pressure curve is shifted down and to the right. The slope of the curve is reduced in the patient with pulmonary fibrosis, while it is normal in the patient with obesity. In asthma (or chronic bronchitis) and emphysema, the volume-pressure curve is shifted up and to the left. In emphysema, the slope of the curve is increased, while it is normal in patients with asthma or bronchitis. In practice, lung volume is used as an index of alterations of the volume-pressure characteristics of the lungs and/or chest wall. The vital capacity is often used as a surrogate for the TLC but it is lower than expected in both restrictive and obstructive disorders. The FEV1.0 reflects the degree of expiratory flow limitation. In a restrictive disorder, lung volume and the FEV1.0 are reduced, but the FEV1.0/FVC ratio is normal. In airflow limitation, lung volume, the FEV1.0, and the FEV1.0/FVC ratio are lower than expected. In airflow limitation, the reversibility with inhaled bronchodilator should be determined. Tests of airway responsiveness are indicated when evaluating patients with unexplained chronic cough, chest tightness, or wheezing, particularly if other lung function tests are normal. The adequacy of gas exchange is assessed by determining the arterial blood gas tensions--PaO2 and PaCO2--and the alveoloarterial pO2 gradient--P(A-a)O2. A lower-than-expected PaO2 can result from several different physiologic disturbances. When alveolar hypoventilation is the sole disturbance, the oxygen in the alveoli and in the blood perfusing them virtually comes into equilibrium, so that the P(A-a)O2 is normal. An elevated P(A-a)O2 is caused by either mismatching of ventilation and perfusion, true venous admixture, a diffusion abnormality, or a combination of these disturbances. Because dyspnea on exertion is a cardinal symptom of respiratory disease, exercise tolerance should be assessed. A reduced exercise tolerance may result from ventilatory limitation, impaired gas exchange, cardiac impairment, impaired delivery of the oxygen to the working muscles, or an inability to use the energy.

Acid-Base Imbalance↗

PubMed1984

Hemodynamics of patients with severe chronic obstructive pulmonary disease during progressive upright exercise.

This study evaluated the relationship between the oxygen consumption (VO2) and cardiac output and heart rate during progressive exercise in the upright position in 26 patients with severe chronic obstructive pulmonary disease. Forced expiratory volume in one second (FEV1) was 0.82 +/- 0.21 L, and single-breath carbon monoxide diffusing capacity was 39 +/- 20% predicted. Cardiac outputs were measured by the direct Fick method. The patients as a group had a normal cardiac output for the level of VO2. The mean pulmonary artery pressure in our patients (22.5 +/- 10.1 mmHg) was increased at rest; during exercise, it increased abnormally to 45.5 +/- 18.9 mmHg. The heart rates were increased both at rest and during exercise, and the increase in heart rate for an increase in VO2 was higher than normal. The relative tachycardia observed was probably related to a combination of abnormal arterial blood gases, concomitant bronchodilator administration, deconditioning, and right ventricular dysfunction. The relative tachycardia did not appear to have an adverse effect on exercise tolerance because the ratio of maximal exercise ventilation to the FEV1 exceeded 35 in those patients with observed maximal heart rates above 90% of predicted. The results of this study suggest that improvements in the exercise tolerance of these patients is dependent upon improving their ventilatory capabilities or the efficacy of their ventilation.

Aged↗