Assessment of Respiratory and Heart Rate Variability in Patients with Community-Acquired Pneumonia

The dissertation is devoted to the study of respiratory and heart rate variability in patients with community-acquired pneumonia using a comprehensive non-invasive approach that combines heart rate variability analysis and impedance pneumography. The study aims to assess the diagnostic significance of the dynamics of cardiac and respiratory cycle parameters, unified under the concept of the "cardiorespiratory pattern," in patients with community-acquired pneumonia in comparison with healthy individuals and depending on disease severity. The work examines the features of rhythm variability, their changes during a modified orthoclinostatic test and over the course of inpatient treatment, as well as the correlation of these parameters with clinical, laboratory, and radiological manifestations of the disease. The author identifies a decrease in heart rate and respiratory variability that grows with pneumonia severity, depletion of the adaptive reserves of the regulatory systems, and a lag in the normalization of cardiorespiratory indicators behind clinical and laboratory improvement.

Relevance of the topic. Community-acquired pneumonia (CAP) is currently an urgent medical, social, and economic problem. Despite the advances achieved in the study of clinical, pathogenetic, and therapeutic aspects, the morbidity and mortality from CAP continue to remain at a high level.

According to the official statistics of the Central Research Institute for Organization and Informatization of Public Health of the Ministry of Health of the Russian Federation, in 2002, 441,052 cases of CAP (4.1‰) were registered in Russia. According to the data of foreign epidemiological studies, the incidence of CAP in adults (over 18 years of age) varies over a wide range: in young and middle-aged persons it is 1–11.6‰; in older age groups it is 25–44‰.

Mortality in CAP is lowest (1–3%) in young and middle-aged persons without concomitant diseases. In contrast, in patients over 60 years of age with concomitant diseases (chronic obstructive pulmonary disease, malignant neoplasms, alcoholism, diabetes mellitus, kidney and liver diseases, cardiovascular diseases, etc.), as well as in cases of severe course of CAP (multilobar infiltration, secondary bacteremia, tachypnea exceeding 30/min, hypotension, acute renal failure), this indicator reaches 15–30% [Chuchalin A.G., Sinopalnikov A.I., 2005].

Improving the quality of CAP diagnostics is a necessary prerequisite for increasing the effectiveness of treatment of the disease.

The methods of functional assessment of the cardiorespiratory system widely used in medical practice — ECG, spirography, as well as many others — have limited informativeness because they analyze only averaged indicators without taking into account the characteristics of their variability. But the human organism is a complex dynamic system, and a more complete characterization of its functioning is provided by observations in dynamics.

The use of a mouthpiece or a face mask during spirography, pneumotachometry, and body plethysmography causes a change in the breathing pattern (slowing and deepening of breathing). Therefore, alternative non-invasive devices have been developed that allow dynamic study of respiratory function without interventions on the area of the nose and mouth. Most often, preference is given to inductive plethysmography and impedance pneumography [Hirsch J.A., Bishop B., 1982].

According to modern concepts, pneumonia should be considered not as a localized process, but as a systemic reaction to inflammation in the pulmonary tissue, which manifests itself as dysfunction of neuroendocrine and humoral regulatory mechanisms [Chuchalin A.G. et al., 2002]. The close anatomical and physiological relationship between the respiratory and cardiovascular systems inevitably involves the circulatory organs in the pathological process in CAP [Pokrovsky V.M., 2000; Sazhneva Yu.V., 2001].

In this regard, a comprehensive study of the cardiorespiratory system of CAP patients with the help of simultaneous recording of breathing patterns and cardiovascular activity is of interest.

The study of the functional regulation of cardiac activity is currently carried out using mathematical analysis of heart rate variability (HRV) [Saish A. John, Malik Marek, 1996]. Heart rate variability analysis is the most informative method for the quantitative assessment of the activity of various parts of the autonomic nervous system, the parameters of which are considered as integral indicators of regulatory processes [Skidan V.N., 2004]. Consequently, it is a non-invasive method for monitoring the state of the regulatory systems of the body and a tool for assessing regulatory disorders in various diseases [Ryabykina G.V. et al., 2001].

Assessment of heart rate variability already has important clinical applications: prediction of the risk of severe cardiac arrhythmias and sudden death in ischemic heart disease, prediction of complications in hypertensive disease, early detection of rejection of transplanted myocardium, diabetic neuropathy, study of the effect of drugs on the autonomic regulation of heart rate [Baevsky R.M. et al., 1978; Belogubets V.I. et al., 1994; Hayano J. et al., 1991; Fennell T.G. et al., 1991; Malliani A. et al., 1994; Bernardi L. et al., 1994; Tsuji H. et al., 1994]. The diagnostic significance of studying heart rate variability in patients with chronic obstructive pulmonary disease (COPD) and bronchial asthma (BA) has been established [Marchenko V.N., 1992, 1996]. At the same time, publications on the study of heart rate variability in CAP appeared relatively recently [Sazhneva Yu.V., 2001; Davidovich I.M., Skidan V.I., Kashina T.V., 2004].

At present, a technique has been developed for the simultaneous recording of respiratory and cardiac activity parameters, combining the study of heart rate variability and impedance pneumography with the use of modern mathematical methods for processing biomedical signals and computer technology [Zulkarneev R.Kh., 1997]. It allows a comprehensive, non-invasive, dynamic study of the functional regulation of the cardiorespiratory system and its changes in CAP, assessment of the effectiveness of the course of treatment, and prediction of the dynamics of the pathological process.

Our study is devoted to investigating the diagnostic possibilities of assessing the variability of the temporal and quantitative characteristics of the cardiac and respiratory cycles, combined into the concept of the "cardiorespiratory pattern" (CRP), in patients with community-acquired pneumonia.

Aim of the study.

To evaluate the diagnostic significance of studying the dynamics of the parameters of the cardiac and respiratory cycles, combined into the concept of the "cardiorespiratory pattern" (CRP), in patients with community-acquired pneumonia.

Tasks of the study:

1. To investigate the features of respiratory and heart rate variability in patients with community-acquired pneumonia in comparison with a control group.

2. To study the state of the processes reflecting the functional regulation of the cardiorespiratory system in patients with community-acquired pneumonia with different severity of the disease.

3. To evaluate the dynamics of the parameters of respiratory and heart rate variability in CAP patients during the orthoclinostatic test.

4. To study the dynamics of the indicators of the cardiorespiratory pattern in pneumonia patients during inpatient treatment.

5. To investigate the correlation of the parameters of respiratory and heart rate variability with the severity of clinical and radiological manifestations of pneumonia.

6. To evaluate the significance of studying the variability of the cardiorespiratory pattern for predicting the clinical course of community-acquired pneumonia.

Scientific novelty.

For the first time, it has been shown that in CAP patients there is a decrease in heart rate and breathing variability, correlated with the severity of the disease. By studying the cardiorespiratory pattern during the orthoclinostatic test, a decrease in the adaptive capabilities of the cardiorespiratory system in CAP patients was revealed. A correlation was found between the decrease in respiratory and heart rate variability and the clinical and radiological manifestations of pneumonia. It has been established that during treatment in pneumonia patients, the normalization of the parameters of the cardiorespiratory pattern lags behind the improvement in clinical and laboratory indicators.

Practical significance of the work.

The inclusion in the diagnostic complex of a non-invasive method of dynamic assessment of the cardiorespiratory pattern using the analysis of respiratory and heart rate variability in the early stages of the disease optimizes the algorithm for examining patients with community-acquired pneumonia.

Analysis of the variability of the cardiorespiratory pattern in the dynamics of treatment using a modified orthoclinostatic test makes it possible to assess the functional state of patients in order to monitor the effectiveness of therapy.

The most informative indicators of the cardiorespiratory pattern in patients with community-acquired pneumonia, depending on the severity of the disease, have been identified, and additional diagnostic criteria for the severe course of community-acquired pneumonia have been determined.

Propositions submitted for defense:

1. The parameters of the cardiorespiratory pattern in pneumonia patients differ significantly from those of healthy individuals, which is manifested by a change in the structure of the respiratory cycle (an increase in respiratory rate, a change in the ratio of the phases of the respiratory cycle), a smaller range of variability of respiratory and heart rhythms. In pneumonia patients, a decrease in the reactivity of the regulatory systems of the respiratory and heart rhythms and an increase in sympathetic influences on heart rate variability are observed, which indicates the depletion of the adaptive capabilities of the body.

2. The severity of changes in the cardiorespiratory pattern in CAP patients increases with the severity of the disease; an interdependence of respiratory and heart rate variability and the clinical and radiological manifestations of pneumonia is observed.

3. During inpatient treatment, an improvement in the indicators of the cardiorespiratory pattern is observed, which does not reach complete normalization.

Approbation of the work.

The main propositions of the dissertation were reported at the scientific-practical conferences "Current Issues of Internal Medicine" (Chelyabinsk, 2003, 2006), the International Youth Scientific and Technical Conference "Intelligent Control and Information Processing Systems" (Ufa, 2003), the XIII, XIV, and XV National Congresses on Respiratory Diseases (Moscow, 2003, 2004, 2005), the Republican Conference of Young Scientists of the Republic of Bashkortostan "Medical Science — 2005" (Ufa, 2005), and the II All-Russian Conference with International Participation "Mechatronics, Automation, Control" (Ufa, 2005).

The approbation of the work took place at a meeting of the problem committee "Internal Diseases" with the participation of the departments of propedeutics of internal diseases, faculty therapy, hospital therapy No. 1 and No. 2 of the State Educational Institution of Higher Professional Education "Bashkir State Medical University" and the departments of therapy of the Institute of Postgraduate Education of BSMU on March 25, 2006.

Implementation of the research results.

The complex method for assessing the cardiorespiratory pattern in patients with community-acquired pneumonia has been implemented in the practice of the pulmonology departments of MU GKB No. 21, MU GKB No. 13 in Ufa and the Republican Clinical Hospital named after G. Kuvatov. The main propositions of the dissertation are used in the lecture material and research work at the department of propedeutics of internal diseases of the State Educational Institution of Higher Professional Education "BSMU of Roszdrav".

Publications. Based on the materials of the dissertation, 15 works have been published.

Scope and structure of the dissertation.

The dissertation is presented on 157 typewritten pages, contains 22 figures, 23 tables, and consists of an introduction, a review of the literature, a description of the material and methods of the study, the results of the author's own research, a