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.