Abstract
Introduction : Cardiopulmonary exercise testing (CPET) is a method used to diagnose and stratify patients with known disease. The use of breath-by-breath analysis of exhaled air in a stress test helps us to understand the root cause and pathophysiology of pathological patterns causing clinical symptomatology.
Aim : Using CPET to elucidate the role of chest deformity on human physical abilities, to determine the correlation of the measured parameters with the anthropometric index (AI) evaluating the severity of the deformity in patients with pectus excavatum (PE).
Methods : The study included 30 paediatric patients with PE. According to AI, patients were divided into two groups, to patients with AI below 0.12 and patients with AI 0.12 and more. Patients underwent CPET using a breath-by-breath exhaled gas analysis method and continuous monitoring of cardiac parameters. Ventilation and cardiac parameters were statistically processed, the severity of the deformity was correlated with the results using the Pearson index.
Results : The severity of the deformity according to AI had no effect on peak ventilation, VO2peak and WRpeak. By graphical representation and prognosis of the data, we demonstrated the relationship between the severity of the deformity and the efficiency of ventilation, OUES and O2Pulse at the peak of the exercise. Ventilation efficiency expressed as the slope of the VE/VCO2 curve also had a graphically dependent trend without statistical significance.
Conclusion : CPET data obtained suggest that physical fitness parameters in patients with PE have a correlation with the severity of the deformity expressed by AI. The OUES parameter is a promising parameter for assessing the overall physical fitness of these patients and a parameter with potential use in deciding on the appropriateness of a therapeutic intervention.
Key words : cardiopulmonary exercise testing, pectus excavatum, exercise tolerance
Introduction
Cardiopulmonary exercise testing (CPET) is a method used to diagnose and stratify patients with known disease. The use of breath-after-breath analysis of exhaled air in a stress test helps us to understand the root cause and pathophysiology of pathological patterns causing clinical symptomatology. Pectus excavatum (PE) is a congenital deformity of the chest of unknown etiology, in which an abnormal formation of bone-cartilaginous joints of the ribs and sternum occurs, creating a concave depression of the chest wall 1. Frequently present symptoms are lack of endurance, shortness of breath during exercise or chest pain 2. Although pectus excavatum may be part of some less common syndromes, patients are usually healthy.
Examination of patients with PE should include a careful anatomical description, chest CT and determination of the so-called Haller index in case of planned surgical intervention, evaluation of the extent of cardiac compression, measurement of lung function and echocardiography in order to detect the presence of mitral valve prolapse (in 15%) or reduced right ventricular volume. Indications for surgical treatment include two or more of the following: severe symptomatic deformity; deformity progression; paradoxical chest movement when breathing; Haller index greater than 3.25; cardiac compression and / or pulmonary compression; finding a restrictive ventilation disorder; mitral valve prolapse, Tawar’s shoulder block, or other cardiological pathology secondary to cardiac compression 3.
In order to non-invasively monitor patients with PE who are not indicated for surgery, a proposal was submitted to assess the severity of pectus excavatum, the so-called anthropometric index (AI). AI for PE is defined as the B measurement divided by the A measurement (AI = B/A)4. The A and B clinical measurements are carried out with the patient in a horizontal supine position on a flat table parallel to the floor during deep inhalation. The A measurement is defined as the largest anteroposterior diameter at the level of the distal third of the sternum, and the B measurement was the largest depth at the same level 4. A cut-off value for determining the severity of PE was determined to be 0.12 based on measurements and comparisons with the Haller index. Patients with a value greater than 0.12 are patients in whom, similar to Haller’s index, surgery is indicated in the presence of the auxiliary criteria listed above5.
Patients with PE may have various subjectively perceived symptoms. Symptoms often vary in severity and their effect on normal daily activities 6. The severity of the deformity does not necessarily correlate with the severity of the symptoms. Many patients are asymptomatic at a younger age, but begin to experience the first symptoms during puberty and adolescence. This can be caused by a highlighting of the growth spurt error or an increase in physical activity. The most common symptoms are dyspnoea during exercise and loss of endurance 6.
Anatomical abnormalities (decreased chest volume, heart compression) are a possible cause of the patient’s subjective symptoms. The increased respiratory work arising from the partial restriction of chest movements in PE and the reduced oxygen supply to the working muscle as a consequence of the reduced venous return to the right atrium probably also play a role 7. Compression of the sternum results in a reduced sternum volume, which leads to a reduction in maximal oxygen consumption during exercise, a reduction in exercise tolerance, a reduction in tidal volume, vital capacity, which reduces body endurance and causes dyspnoea and compensatory tachypnoea during exercise9.
In addition to somatic problems, patients with PE often have psychological problems based on the perception of physical deformity. Exercise intolerance can also be a manifestation of somatization of psychologically escalating fear of physical activity, which could lead to the discovery of the body (showering, changing clothes) and also a manifestation of exercise, which is based on hypoactivity10.
Stress test by CPET is a suitable examination to reveal the cause and pathophysiology of performance decline in patients with PE7. O2Pulse, VE (minute ventilation) and maximum oxygen consumption (VO2Max, VO2Peak) values ​​may be significantly lower in patients with PE than predicted values ​​for patient height and weight7. Lesbo et al. demonstrated in a sample of 49 adolescents, using the method of repeated breathing of inert gases, that PE significantly reduces exercise tolerance, has an effect on the values ​​of maximum oxygen consumption and cardiac output 11. The study by Rowland et al. confirmed the finding of impaired cardiac function in patients with PE using exercise echocardiography, where patients with PE had a significantly lower cardiac index compared to healthy controls 12. The lower limit of the norm and subnormal values ​​in the exercise examination suggest that the patient requires intervention (surgical, non-surgical). Postoperative measurement of CPET parameters in most cases of symptomatic patients reveals improvement or adjustment of cardiorespiratory parameters13.