Cardiac output during exercise in patients with COPD

Utility of Cardiopulmonary Exercise Testing in Chronic Obstructive Pulmonary Disease: A Review

Chronic obstructive pulmonary disease (COPD) is a disease defined by airflow obstruction with a high morbidity and mortality and significant economic burden. Although pulmonary function testing is the cornerstone in diagnosis of COPD, it cannot fully characterize disease severity or cause of dyspnea because of disease heterogeneity and variable related and comorbid conditions affecting cardiac, vascular, and musculoskeletal systems. Cardiopulmonary exercise testing (CPET) is a valuable tool for assessing physical function in a wide range of clinical conditions, including COPD. Familiarity with measurements made during CPET and its potential to aid in clinical decision-making related to COPD can thus be useful to clinicians caring for this population. This review highlights pulmonary and extrapulmonary impairments that can contribute to exercise limitation in COPD. Key elements of CPET are identified with an emphasis on measurements most relevant to COPD. Finally, clinical applications of CPET demonstrated to be of value in the COPD setting are identified. These include quantifying functional capacity, differentiating among potential causes of symptoms and limitation, prognostication and risk assessment for operative procedures, and guiding exercise prescription.

Cardiorespiratory Response during the 1-min Sit-to-Stand Test in Chronic Obstructive Pulmonary Disease

PURPOSE

This study aimed to assess the cardiorespiratory response during a 1-min sit-to-stand test (1STS) in comparison with cycling cardiopulmonary exercise test (CPET) in people with chronic obstructive pulmonary disease (COPD) and in healthy subjects and to evaluate whether 1STS may induce leg fatigue in these individuals.

METHODS

Fourteen people with severe COPD and 12 healthy subjects performed a 1STS and a CPET during which cardiorespiratory response, perception of dyspnea, and leg fatigue were assessed. Quadriceps strength was assessed before and after 1STS, and contractile fatigue was defined as a postexercise fall in quadriceps twitch force greater than 15% of resting values.

RESULTS

In COPD, peak V˙O2, V˙E, and HR achieved during 1STS reached 113%, 103%, and 93% of the corresponding values during CPET, respectively. Decrease in SpO2 from preexercise to peak exercise and the magnitude of dynamic hyperinflation were similar between 1STS and CPET. Borg dyspnea and leg fatigue scores were higher for CPET than 1STS. In healthy subjects, peak cardiorespiratory demand and symptom scores were higher during CPET compared with 1STS. A V˙O2 overshoot during recovery was observed only in people with COPD. After 1STS, the V˙O2 half-time recovery of COPD was 152 ± 25 s compared with 74 ± 18 in healthy subjects (P < 0.01). Ten people with COPD and five healthy subjects were considered as fatiguers.

CONCLUSION

The 1STS induced a similar cardiorespiratory stress to that of CPET and was associated with contractile quadriceps fatigue in people with severe COPD. The V˙O2 overshoot and slower recovery time of cardiorespiratory variables seen in COPD demonstrate the clinical relevance of monitoring the recovery phase of exercise.

Metabolic and cardiorespiratory effects of decreasing lung hyperinflation with budesonide/formoterol in COPD: a randomized, double-crossover, placebo-controlled, multicenter trial

BACKGROUND

Studies suggest that acute decreases in lung hyperinflation at rest improves cardiac function and increases lung vascular perfusion from decompression of a compromised heart. In those studies, changes in resting oxygen uptake induced by medications, an alternative explanation for compensatory increased cardiac function, were not explored.

METHODS

This double-blind, multicenter, double-crossover study enrolled adults with chronic obstructive pulmonary disease, resting hyperinflation, and > 10% improvement in inspiratory capacity after 2 inhalations of budesonide/formoterol 160/4.5 μg. Metabolic, cardiac, and ventilatory function were measured 60 min pre-/post-dose at each visit. Primary endpoint was change in resting oxygen uptake for budesonide/formoterol versus placebo.

RESULTS

Fifty-one patients (median age: 63 years) received treatment. Compared with placebo, budesonide/formoterol significantly increased resting oxygen uptake (mean change from baseline: 1.25 vs 11.37 mL/min; P = 0.007) as well as tidal volume and minute ventilation. This occurred despite improvements in the inspiratory capacity, forced vital capacity, and expiratory volume in 1 s. No significant treatment differences were seen for oxygen saturation, respiratory rate, and resting dyspnea. There was a numerical increase in oxygen pulse (oxygen uptake/heart rate). Correlations between inspiratory capacity and oxygen pulse were weak.

CONCLUSIONS

Budesonide/formoterol treatment in resting hyperinflated patients with COPD results in significant deflation. The increase in oxygen uptake and minute ventilation at lower lung volumes, without changes in heart rate and with minimal improvement in oxygen pulse, suggests increased oxygen demand as a contributor to increased cardiac function.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02533505.

Impaired central hemodynamics in chronic obstructive pulmonary disease during submaximal exercise

It is unknown whether central hemodynamics are impaired during exercise in chronic obstructive pulmonary disease (COPD) patients. We hypothesized that, at a similar absolute V̇o₂ during exercise, COPD patients would have a lower stroke volume and cardiac output compared with healthy controls. Furthermore, we hypothesized that greater static hyperinflation [ratio of inspiratory capacity to total lung capacity (IC/TLC)] and expiratory intrathoracic pressure would be significantly related to the lower cardiac output and stroke volume responses in COPD patients. Clinically stable COPD (n = 13; FEV₁/FVC: 52 ± 13%) and controls (n = 10) performed constant workload submaximal exercise at an absolute V̇o₂ of ~1.3 L/min. During exercise, inspiratory capacity maneuvers were performed to determine operating lung volumes and cardiac output (via open-circuit acetylene rebreathe technique) and esophageal pressure were measured. At similar absolute V̇o₂ during exercise (P = 0.81), COPD had lower cardiac output than controls (COPD: 11.0 ± 1.6 vs. control: 12.2 ± 1.2 L/min, P = 0.03) due to a lower stroke volume (COPD: 107 ± 13 vs. control: 119 ± 19 mL, P = 0.04). The heart rate response during exercise was not different between groups (P = 0.66). FEV₁ (%predicted) and IC/TLC were positively related to stroke volume (r = 0.68, P = 0.01 and r = 0.77, P < 0.01). Last, esophageal pressure-time integral during inspiration was positively related to cardiac output (r = 0.56, P = 0.047). These data demonstrate that COPD patients have attenuated cardiac output and stroke volume responses during exercise compared with control. Furthermore, these data suggest that the COPD patients with the most severe hyperinflation and more negative inspiratory intrathoracic pressures have the most impaired central hemodynamic responses.NEW & NOTEWORTHY Chronic obstructive pulmonary disease leads to cardiac structural changes and pulmonary derangements that impact the integrative response to exercise. However, it is unknown whether these pathophysiological alterations influence the cardiac response during exercise. Herein, we demonstrate that COPD patients exhibit impaired central hemodynamics during exercise that are worsened with greater hyperinflation.

Factors limiting exercise tolerance in chronic lung diseases

The major limitation to exercise performance in patients with chronic lung diseases is an issue of great importance since identifying the factors that prevent these patients from carrying out activities of daily living provides an important perspective for the choice of the appropriate therapeutic strategy. The factors that limit exercise capacity may be different in patients with different disease entities (i.e., chronic obstructive, restrictive or pulmonary vascular lung disease) or disease severity and ultimately depend on the degree of malfunction or miss coordination between the different physiological systems (i.e., respiratory, cardiovascular and peripheral muscles). This review focuses on patients with chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD) and pulmonary vascular disease (PVD). ILD and PVD are included because there is sufficient experimental evidence for the factors that limit exercise capacity and because these disorders are representative of restrictive and pulmonary vascular disorders, respectively. A great deal of emphasis is given, however, to causes of exercise intolerance in COPD mainly because of the plethora of research findings that have been published in this area and also because exercise intolerance in COPD has been used as a model for understanding the interactions of different pathophysiologic mechanisms in exercise limitation. As exercise intolerance in COPD is recognized as being multifactorial, the impacts of the following factors on patients' exercise capacity are explored from an integrative physiological perspective: (i) imbalance between the ventilatory capacity and requirement; (ii) imbalance between energy demands and supplies to working respiratory and peripheral muscles; and (iii) peripheral muscle intrinsic dysfunction/weakness.

Ventilatory and cardiocirculatory exercise profiles in COPD: the role of pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a well-recognized complication of COPD. The impact of PH on exercise tolerance is largely unknown. We evaluated and compared the circulatory and ventilatory profiles during exercise in patients with COPD without PH, with moderate PH, and with severe PH.

METHODS

Forty-seven patients, GOLD (Global Initiative for Chronic Obstructive Lung Disease)stages II to IV, underwent cardiopulmonary exercise testing and right-sided heart catheterization at rest and during exercise. Patients were divided into three groups based on mean pulmonary artery pressure (mPAP) at rest: no PH (mPAP, < 25 mm Hg), moderate PH (mPAP, 25-39 mm Hg),and severe PH (mPAP, ≥ 40 mm Hg). Mixed venous oxygen saturation (S VO 2 ) was used for evaluating the circulatory reserve. Pa CO 2 and the calculated breathing reserve were used for evaluation of the ventilatory reserve.

RESULTS

Patients without PH (n = 24) had an end-exercise S VO 2 of 48%± 9%, an increasing Pa CO 2 with exercise, and a breathing reserve of 22% ± 20%. Patients with moderate PH (n = 14) had an exercise S VO 2 of 40% ± 8%, an increasing Pa CO 2 , and a breathing reserve of 26% ± 15%. Patients with severe PH (n =9) had a significantly lower end-exercise S VO 2 (30% ± 6%), a breathing reserve of 37% ± 11%, and an absence of Pa CO 2 accumulation.

CONCLUSION

Patients with severe PH showed an exhausted circulatory reserve at the end of exercise.A profile of circulatory reserve in combination with ventilatory impairments was found inpatients with COPD and moderate or no PH. The results suggest that pulmonary vasodilation might only improve exercise tolerance in patients with COPD and severe PH.

Autonomic dysfunction in patients with chronic obstructive pulmonary disease (COPD)

It has been recognized that chronic obstructive pulmonary disease (COPD) is a systemic disease which has been shown to negatively affect the cardiovascular and autonomic nerve system. The complexity of the physiologic basis by which autonomic dysfunction occurs in patients with COPD is considerable and the knowledge in this field remains elementary. The purpose of this review is to provide an overview of important potential mechanisms which might affect the autonomic nervous system in patients with COPD. This review aims to summarize the basic research in the field of autonomic dysfunction in patients with COPD. In COPD patients the activity of sympathetic nerves may be affected by recurrent hypoxemia, hypercapnia, increased intrathoracic pressure swings due to airway obstruction, increased respiratory effort, systemic inflammation and the use of betasympathomimetics. Furthermore, experimental findings suggest that autonomic dysfunction characterized by a predominance of sympathetic activity can significantly modulate further inflammatory reactions. The exact relationship between autonomic dysfunction and health status in COPD remains to be elucidated. Treatment aimed to restore the sympathovagal balance towards a reduction of resting sympathetic activity may modulate the inflammatory state, and possibly contributes to improved health status in COPD.

Mechanisms of non-pharmacologic adjunct therapies used during exercise in COPD

Individuals with chronic obstructive pulmonary disease (COPD) are often limited in their ability to perform exercise due to a heightened sense of dyspnea and/or the occurrence of leg fatigue associated with a reduced ventilatory capacity and peripheral skeletal muscle dysfunction, respectively. Pulmonary rehabilitation programs have been shown to improve exercise tolerance and health related quality of life. Additional therapeutic approaches such as non-invasive ventilatory support (NIVS), heliox (He-O(2)) and supplemental oxygen have been used as non-pharmacologic adjuncts to exercise to enhance the ability of patients with COPD to exercise at a higher exercise-intensity and thus improve the physiological benefits of exercise. The purpose of the current review is to examine the pathophysiology of exercise limitation in COPD and to explore the physiological mechanisms underlying the effect of the adjunct therapies on exercise in patients with COPD. This review indicates that strategies that aim to unload the respiratory muscles and enhance oxygen saturation during exercise alleviate exercise limiting factors and improve exercise performance in patients with COPD. However, available data shows significant variability in the effectiveness across patients. Further research is needed to identify the most appropriate candidates for these forms of therapies.

Right atrial pressure affects the interaction between lung mechanics and right ventricular function in spontaneously breathing COPD patients

INTRODUCTION

It is generally known that positive pressure ventilation is associated with impaired venous return and decreased right ventricular output, in particular in patients with a low right atrial pressure and relative hypovolaemia. Altered lung mechanics have been suggested to impair right ventricular output in COPD, but this relation has never been firmly established in spontaneously breathing patients at rest or during exercise, nor has it been determined whether these cardiopulmonary interactions are influenced by right atrial pressure.

METHODS

Twenty-one patients with COPD underwent simultaneous measurements of intrathoracic, right atrial and pulmonary artery pressures during spontaneous breathing at rest and during exercise. Intrathoracic pressure and right atrial pressure were used to calculate right atrial filling pressure. Dynamic changes in pulmonary artery pulse pressure during expiration were examined to evaluate changes in right ventricular output.

RESULTS

Pulmonary artery pulse pressure decreased up to 40% during expiration reflecting a decrease in stroke volume. The decline in pulse pressure was most prominent in patients with a low right atrial filling pressure. During exercise, a similar decline in pulmonary artery pressure was observed. This could be explained by similar increases in intrathoracic pressure and right atrial pressure during exercise, resulting in an unchanged right atrial filling pressure.

CONCLUSIONS

We show that in spontaneously breathing COPD patients the pulmonary artery pulse pressure decreases during expiration and that the magnitude of the decline in pulmonary artery pulse pressure is not just a function of intrathoracic pressure, but also depends on right atrial pressure.

Intercostal muscle blood flow limitation during exercise in chronic obstructive pulmonary disease

RATIONALE

It has been hypothesized that, because of the high work of breathing sustained by patients with chronic obstructive pulmonary disease (COPD) during exercise, blood flow may increase in favor of the respiratory muscles, thereby compromising locomotor muscle blood flow.

OBJECTIVES

To test this hypothesis by investigating whether, at the same work of breathing, intercostal muscle blood flow during exercise is as high as during resting isocapnic hyperpnea when respiratory and locomotor muscles do not compete for the available blood flow.

METHODS

Intercostal and vastus lateralis muscle perfusion was measured simultaneously in 10 patients with COPD (FEV₁ = 50.5 ± 5.5% predicted) by near-infrared spectroscopy using indocyanine green dye.

MEASUREMENTS AND MAIN RESULTS

Measurements were made at several exercise intensities up to peak work rate (WRpeak) and subsequently during resting hyperpnea at minute ventilation levels up to those at WRpeak. During resting hyperpnea, intercostal muscle blood flow increased with the power of breathing to 11.4 ± 1.6 ml/min per 100 g at the same ventilation recorded at WRpeak. Conversely, during graded exercise, intercostal muscle blood flow remained unchanged from rest up to 50% WRpeak (6.8 ± 1.3 ml/min per 100 g) and then fell to 4.5 ± 0.8 ml/min per 100 g at WRpeak (P = 0.003). Cardiac output plateaued above 50% WRpeak (8.4 ± 0.1 l/min), whereas vastus lateralis muscle blood flow increased progressively, reaching 39.8 ± 7.1 ml/min per 100 g at WRpeak.

CONCLUSIONS

During intense exercise in COPD, restriction of intercostal muscle perfusion but preservation of quadriceps muscle blood flow along with attainment of a plateau in cardiac output represents the inability of the circulatory system to satisfy the energy demands of locomotor and respiratory muscles.

The degree of exercise hypoxemia reflects pulmonary artery pressure during early exercise in chronic obstructive pulmonary disease patients

The causes of both exertional pulmonary hypertension and pulmonary hypertension in general in chronic obstructive pulmonary disease (COPD) remain to be elucidated. To further understand the pathophysiology in COPD patients, it may be important to recognize the existence of exertional pulmonary hypertension and to determine the severity of exertional hypoxemia. However, little is known about their relationship. To investigate whether the severity of exertional hypoxemia, as evaluated by the Deltaartery oxygen tension/Deltaoxygen consumption (PaO(2)-slope) correlates with the mean pulmonary artery pressure (Ppa), cardiopulmonary exercise testing with haemodynamics was done in 10 patients with moderate to very severe COPD. The PaO(2)-slope was significantly correlated with the mean Ppa from 25% to 40% of the maximum Watts (Wmax), and was most significant at 30% Wmax (r = -0.904, P<0.0001). In this phase, all parameters, except for the mean Ppa and the mixed venous oxygen tension, were not markedly changed from resting levels. At 30% Wmax, the mean Ppa (mean, 27 mmHg) with no or mild hypoxemia was also significantly correlated with the Deltaartery oxygen saturation/Deltaoxygen consumption (SpO(2)-slope) (r = -0.789, P = 0.004). On stepwise multiple regression analysis, the PaO(2)-slope was the most significant predictor of mean Ppa at 30% Wmax. In conclusion, the PaO(2)-slope and the SpO(2)-slope reflect Ppa during the early exercise phase. Thus, assessment of these parameters could be useful to evaluate the cardiopulmonary haemodynamic pathophysiology of COPD patients.

New Modalities of Pulmonary Rehabilitation in Patients with Chronic Obstructive Pulmonary Disease

Pulmonary rehabilitation has been shown to be an important part of the management of patients with chronic obstructive pulmonary disease (COPD). Exercise training is the corner stone of a comprehensive, multidisciplinary pulmonary rehabilitation in COPD and has been shown to improve health-related quality of life and exercise capacity. Nevertheless, not every COPD patient responds well to pulmonary rehabilitation. Future trials should focus on new additions to conventional pulmonary rehabilitation programmes to optimise its effects on health-related quality of life, exercise capacity, body composition and muscle function in patients with COPD. Therefore, a patient-tailored approach is inevitable. Advantages and disadvantages of new modalities of pulmonary rehabilitation will be outlined in detail, including the following: endurance training and long-acting bronchodilatators; endurance training and technical modalities (inspiratory pressure support and inspiratory muscle training); interval training; resistance training; transcutaneous neuromuscular electrical stimulation; and exercise training and supplements (oxygen, oral creatine, anabolic steroids and polyunsaturated fatty acids). Based on well defined baseline characteristics, patients should most probably be individually selected. At present, these new modalities of pulmonary rehabilitation have been shown to improve body composition, skeletal muscle function and sometimes also exercise capacity. However, the translation to an improved health-related quality of life is mostly lacking, and cost effectiveness and long-term effects have not been studied. Moreover, future trials should study the effects of pulmonary rehabilitation in elderly patients with restrictive pulmonary diseases.

Influence of expiratory flow-limitation during exercise on systemic oxygen delivery in humans

To determine the effects of exercise with expiratory flow-limitation (EFL) on systemic O(2) delivery, seven normal subjects performed incremental exercise with and without EFL at approximately 0.8 l s(-1) (imposed by a Starling resistor in the expiratory line) to determine maximal power output under control (W'(max,c)) and EFL (W'(max,e)) conditions. W'(max,e) was 62.5% of W'(max,c), and EFL exercise caused a significant fall in the ventilatory threshold. In a third test, after exercising at W'(max,e) without EFL for 4 min, EFL was imposed; exercise continued for 4 more minutes or until exhaustion. O(2) consumption (V'(O)(2)) was measured breath-by-breath for the last 90 s of control, and for the first 90 s of EFL exercise. Assuming that the arterio-mixed venous O(2) content remained constant immediately after EFL imposition, we used V'(O)(2) as a measure of cardiac output (Q'(c)). Q'(c) was also calculated by the pulse contour method with blood pressure measured continuously by a photo-plethysmographic device. Both sets of data showed a decrease of Q'(c) due to a decrease in stroke volume by 10% (p < 0.001 for V'(O)(2)) with EFL and remained decreased for the full 90 s. Concurrently, arterial O(2) saturation decreased by 5%, abdominal, pleural and alveolar pressures increased, and duty cycle decreased by 43%. We conclude that this combination of events led to a decrease in venous return secondary to high expiratory pressures, and a decreased duty cycle which decreased O(2) delivery to working muscles by approximately 15%.

Intermittent Exercise Test in Chronic Obstructive Pulmonary Disease Patients: How Do the Pulmonary Hemodynamics Adapt?

PURPOSE

Endurance training is an important component of rehabilitation in patients with chronic obstructive pulmonary disease (COPD). In our study, we investigated the pulmonary hemodynamics' adaptation during a high-intensity intermittent exercise in such patients.

METHODS

Eight patients underwent a 30-min exercise, alternating a 4-min work set at their first ventilatory threshold with a 1-min exercise set at 90% of their maximal tolerated power output. Pulmonary arterial pressure was measured by means of a right heart catheter. Cardiac output was calculated using the Fick's principle applied to oxygen.

RESULTS

VO(2), cardiac output, and ventilation increased during the first minutes of exercise and remained stable thereafter. Heart rate increased significantly and progressively to its maximal value from rest to the end of the test (P < 0.001). After an initial increase, stroke volume decreased significantly (P < 0.05). Pulmonary arterial pressure increased from rest (mean +/- SEM 23.9 +/- 2.1 mm Hg) to the fifth minute of exercise (41.6 +/- 2.8 mm Hg), and decreased significantly thereafter (35.2 +/- 3.3 mm Hg at the 30th minute) (P < 0.001). Total pulmonary vascular resistance decreased from rest to the end of the test (P < 0.001).

CONCLUSION

The high-intensity 1-min bouts of work of our intermittent work exercise are well tolerated without pushing the pulmonary arterial pressure dramatically high in COPD patients.

Influence of expiratory loading and hyperinflation on cardiac output during exercise

Patients with obstructive lung disease are exposed to expiratory loads (ELs) and dynamic hyperinflation as a consequence of expiratory flow limitation. To understand how these alterations in lung mechanics might affect cardiac function, we examined the influence of a 10-cmH2O EL, alone and in combination with voluntary hyperinflation (ELH), on pulmonary pressures [esophageal (Pes) and gastric (Pg)] and cardiac output (CO) in seven healthy subjects. CO was determined by using an acetylene method at rest and at 40 and 70% of peak work. At rest and during exercise, EL resulted in an increase in Pes and Pg (7-18 cmH2O; P < 0.05) and a decrease in CO (from 5.3 ± 1.8 to 4.5 ± 1.4, 12.2 ± 2.2 to 11.2 ± 2.2, and 16.3 ± 3.3 to 15.2 ± 3.2 l/min for rest, 40% peak work, and 70% peak work, respectively; P < 0.05), which remained depressed after an additional 2 min of EL. With ELH, CO increased at rest and both exercise loads (relative to EL only) but remained below control values. The changes in CO were due to a reduction in stroke volume with a tendency for stroke volume to fall further with prolonged EL. There was a negative correlation between CO and the increase in expiratory Pes and Pg with EL ( R = -0.58 and -0.60; P < 0.01), whereas the rise in CO with subsequent hyperinflation was related to a more negative Pes ( R = 0.72; P < 0.01). In conclusion, EL leads to a reduction in CO, which appears to be primarily related to increases in expiratory abdominal and intrathoracic pressure, whereas ELH resulted in an improved CO, suggesting that lung inflation has little impact on cardiac function.

Hemodynamic characterization of patients with severe emphysema

In 120 patients with severe emphysema evaluated for participation in the National Emphysema Treatment Trial, pulmonary hemodynamics and ventricular function were assessed. Pulmonary function tests were (%predicted): FEV(1) = 27%; residual volume = 224.6%; diffusion capacity = 26.7%. In 90.8% of patients, end-expiratory pulmonary artery mean pressure was > 20 mm Hg; in 61.4%, end-expiratory wedge pressure was > 12 mm Hg. Cardiac index was normal. Mean pulmonary artery pressure correlated inversely with arterial PO(2), and severity of emphysema, and directly with wedge pressure. Multiple stepwise regression revealed that arterial PO(2) was not an independent predictor of mean pulmonary artery pressure. No correlation was found between indices of emphysema severity and PA pressures. Diastolic ventricular pressures were increased without evidence of systolic dysfunction. We conclude that (1) elevations of pulmonary vascular pressures are common, (2) pulmonary hypertension may be related to factors other than hypoxia, (3) pulmonary hypertension does not impair resting systemic O(2) delivery, and (4) elevated cardiac diastolic pressures do not represent systolic dysfunction.

Role of CO diffusing capacity during exercise in the preoperative evaluation for lung resection

We conducted a prospective study to evaluate whether lack of an adequate increase in diffusing capacity for carbon monoxide (DL(CO)) during exercise is associated with a greater postoperative complication rate after lung resection. We used the three-equation method (3EQ-DL(CO)), a modification of the single breath DL(CO) technique to determine DL(CO) during exercise in 57 patients undergoing lung resection at Vancouver General Hospital from October 1998 to May 1999. 3EQ-DL(CO) was determined during steady-state exercise at 35% and 70% of the maximal workload reached in a progressive exercise test. Maximal oxygen uptake (VO(2)max), DL(CO) at rest, and the increase in DL(CO) during exercise were compared in relation to postoperative complications. Patients with complications had lower resting values of DL(CO) (R-DL(CO)), a smaller increase in DL(CO) from rest to 70% of maximal workload expressed as a percent of the predicted DL(CO) at rest ([70% - R]-DL(CO)%), and a lower VO(2)max than did patients without complications. Results suggested that (70% - R)-DL(CO)% was the best preoperative predictor of postoperative complications; a cutoff limit of 10% was the best index to identify complications, yielding a complication rate of 100% in patients with (70% - R)-DL(CO)% < 10% as compared with a complication rate of 10% in patients with (70% - R)-DL(CO)% >/= 10% (sensitivity = 78%, specificity = 100%). Patients who do not increase their DL(CO) sufficiently during exercise ([70% - R]-DL(CO)% < 10%) have a greater complication rate after lung resection.

Pulmonary vasodilatation and augmentation of right ventricular function following terbutaline infusion in severe chronic pulmonary disease

Twenty patients with a median age of 61 years and a median forced expired volume in 1 s (FEV1) after bronchodilating therapy of 0.55 l were studied in order to measure the effect of intravenous terbutaline on bronchial tone, cardiac function, pulmonary haemodynamics, gas exchange, and oxygen transport capacity during rest and in 10 patients during exercise. Terbutaline infusion during rest resulted in an increase in heart rate from 84 to 103 beats min-1 (P less than 0.01), a decrease in mean systemic arterial pressure from 95 to 80 mmHg (P less than 0.02), an unchanged mean pulmonary arterial pressure (18 mmHg), an increase in cardiac index from 2.89 to 3.86 l min-1 m-2 (P less than 0.01), an increase in right ventricular ejection fraction from 45 to 53% (P less than 0.01), an increase in left ventricular ejection fraction from 63 to 67% (NS), an unchanged arterial oxygen tension, and an increase in calculated oxygen delivery from 533 to 638 ml O2 min-1 m-2 (P less than 0.01). During exercise terbutaline infusion resulted in an increase in heart rate from 108 to 120 beats min-1 (P less than 0.05), a decrease in mean systemic arterial pressure from 117 to 106 mmHg (P less than 0.01), a decrease in mean pulmonary arterial pressure from 29 to 22 mmHg (P less than 0.01), an increase in cardiac index from 4.53 to 4.64 min-1 m-2 (NS), an unchanged arterial oxygen tension, and an increase in the calculated oxygen delivery from 834 to 856 ml O2 min-1 m-2 (NS). It was concluded that terbutaline augments right ventricular function: increases right ventricular ejection fraction and decreases right ventricular end-diastolic volume, and further decreases pulmonary vascular resistance without decreasing arterial oxygen tension, and increases oxygen delivery in patients with chronic pulmonary disease during rest and exercise.

Exercise tolerance and effects of training in young patients with cystic fibrosis and mild airway obstruction

We evaluated the effects of an 8-week aerobic training (1 hr, three times a week) on physical performance of ten patients with cystic fibrosis (CF) (median age, 12.5 yr; range 11.1-15.3 yr), with mild airway obstruction (FEV1 = 77 +/- 22% pred.), and ten healthy age-matched children (CONTR) (median age, 12.7 yr; range 12.2-15.2 yr). Physical performance was tested with maximal incremental (MAX) and submaximal (SMAX) (fixed workload of 1.7 W/kg during 6 min) exercise tests on a cycle ergometer. These and standard spirometric and anthropometric measurements were performed at the beginning and end of a period with usual daily activity and one with the training program. The kinetics of ventilatory parameters at the onset and end of SMAX were displayed by fitting data on oxygen uptake and minute ventilation by monoexponential curves (least-squares method). At the start and the end of the training period, all children were timed for endurance run to voluntary exhaustion and for sprinting through an obstacle course. A pattern of relative hyperventilation during SMAX and of poor performance in endurance and obstacle runs were evident at the start of the training period in patients with CF. The effects of training on MAX and SMAX were small and partial; the improvement in field test performances was significant only for CF and could be attributed to improvement of skill and motivation.

Oral terbutaline augments cardiac performance in chronic obstructive pulmonary disease

In previous research, we have demonstrated that parenterally administered terbutaline can augment resting cardiac function in patients with chronic obstructive pulmonary disease (COPD). Because the oral form of terbutaline is more widely utilized, a double-blind, randomized, crossover, placebo-controlled trial of the cardiopulmonary effects of oral terbutaline was conducted in ten patients with COPD. Right and left ventricular ejection fractions (RVEF and LVEF) were determined by first pass radionuclide angiography. There were no differences in spirometry and hemodynamic measurements between treatment and placebo days. Following 5 mg of oral terbutaline, there was a small but statistically significant increase in forced expiratory volume in 1 second and in heart rate, but no significant change in forced vital capacity or blood pressure. LVEF improved significantly with terbutaline both at rest (62% +/- 6% vs. 67% +/- 9%, mean +/- SD) and during submaximal steady state exercise (61% +/- 5% vs. 67% +/- 10%). RVEF improved significantly at rest (64% +/- 6% vs. 69% +/- 5%), but not during submaximal steady state exercise (65% +/- 6% vs. 68% +/- 7%). Thus, oral terbutaline produces significant improvement in biventricular systolic pump performance at rest, and increases left ventricular ejection fraction during submaximal exercise in patients with moderate to severe COPD.

Right ventricular dysfunction and the exercise limitation of chronic obstructive pulmonary disease

This study examined right ventricular function during exercise in patients with chronic obstructive pulmonary disease to answer the following questions: Is there a significant correlation between oxygen consumption at maximal exercise and exercise right ventricular ejection fraction? Does the right ventricular ejection fraction response to exercise correlate with exercise changes in pulmonary artery pressure, total pulmonary resistance or pulmonary vascular resistance? Which combinations of cardiac, ventilatory and blood gas variables are the best predictors of oxygen consumption at maximal exercise? Twenty-six patients with stable chronic obstructive pulmonary disease performed symptom-limited supine bicycle exercise with simultaneous hemodynamic and radionuclide ventriculographic measurements. The oxygen consumption at maximal exercise correlated with the exercise right ventricular ejection fraction (n = 21, r = 0.66; p less than 0.005), exercise stroke volume (r = 0.68; p less than 0.001), exercise cardiac output (r = 0.77; p less than 0.00005) and exercise ventilation (r = 0.85; p less than 0.00001). The change in right ventricular ejection fraction from rest to exercise correlated inversely with the change from rest to exercise in total pulmonary resistance (r = -0.51; p less than 0.05) but not with the change in mean pulmonary pressure (r = -0.37) or in pulmonary vascular resistance (r = 0.09). Multivariate analysis showed that the variables giving the highest combined correlation with oxygen consumption were ventilation and right ventricular ejection fraction (r = 0.95, adjusted r2 = 0.88). These results suggest that exercise oxygen consumption of patients with chronic obstructive pulmonary disease is related to right ventricular systolic function, exercise right ventricular dysfunction is related, in part, to abnormal exercise total pulmonary resistance, and exercise limitation in chronic obstructive pulmonary disease occurs as a result of the dynamic interaction between disordered right heart function and ventilation.

Multiple factors limit exercise capacity in cystic fibrosis

Exercise testing was performed in 50 patients with cystic fibrosis to determine whether hemodynamic factors limit exercise capacity in the disease. Prior to exercise testing, lung function and blood gas values were measured. Nutritional status was determined by calculating a weight for height (Wt for Ht) ratio for each subject. A progressive exercise test was used to determine maximum work capacity (Wmax). Cardiac output (Q) (indirect Fick method), and stroke volume (SV) were computed during steady-state exercise at 50% Wmax in 21 of 50 patients. Wmax, SV, Q, and lung function results are expressed as per cent predicted. The mean (+/- SD) Wmax was 75 +/- 23%. Multiple regression analysis showed that maximum voluntary ventilation, resting PaO2, and Wt for Ht accounted for 84% of the variance in Wmax. Although some patients had a reduced SV (mean = 96%) during steady-state exercise, all patients achieved a normal cardiac output (mean = 115%). SV correlated with resting PaO2 but not with lung function. We conclude that exercise capacity in cystic fibrosis is influenced by lung function, nutritional status, and resting hypoxemia, but not by cardiac function; the SV limitation noted in some patients may be due to increased pulmonary vascular resistance related to hypoxemia.