Pathophysiology of ventilation disorders and pulmonary gas exchange Spirometry Respiratory system - physiology The main functions at the level of the lungs: • ventilation • diffusion • perfusion Alveolar ventilation VA= (VT-VD) x f VT….tidal volume VD ….dead volume f ….respiratory rate Pathophysiology of respiratory function Ventilation disorders • simple hypoventilation • obstructive ventilatory disorders (constriction of the airways) • restrictive ventilatory disorders (reduction of functional lung parenchyma or limitation of respiratory movements) • mixed ventilation disorders Simple hypoventilation • usually extrapulmonary cause – CNS (poisoning, drugs, accidents) – upper airway obstruction – constriction of the bronchioles – lack of surfactant, fibrotic changes - changes in compliance • Decrease of V‘A= (VT-VD) x f • hypoxemia, hypercapnia Obstructive pulmonary disorders • localized obstruction – bronchial obstruction (foreign body, tumor, inflammation, nodules ..) • generalized obstruction – reversible – asthma bronchiale – irreversible - COPD (emphysema, chronic bronchitis) Obstructive pulmonary disorders Asthma bronchiale • chronic inflammatory disease of the airways characterized by an increased reactivity to different stimuli leading to variable airflow obstruction that is reversible, either spontaneously or after treatment. • 2 to 3% of the population • increasing incidence • multifactorial disease Asthma - Clinical symptoms • difficulty breathing, wheezing breath, cough • Asthma attacks alternating with periods without symptoms • variability – seasonal – diurnal (night and morning attacks) – stress (exercise-induced asthma) Asthma - classification • atopic (allergic) asthma – Genetic predisposition + allergen I.typ hypersen. • non-atopic (non-allergic) asthma – endogenous A. (unknown cause) – Irritative a. (chem. comp., heat, cold) – Aspirin a. (and other drugs) Type 1 hypersensitivity (IgE) Asthma - phase of attack • early (immediate response) – 30 min, mediators of mast cells – increased secretion of mucus, swelling of the mucous membrane – smooth muscle contraction (bronchospasm) • the late response – after 4-6 hours, mediators, neutrophils, eosinophils – inflammation, eventually destruction of the epithelium Asthma – pulmonary function • at the rest – sometimes even without symptoms of obstruction – bronchoprovocation test • in attack - signs of obstruction – reduced dynamic ventilatory parameters – improvement after bronchodilator Treatment of asthma • elimination or reduction of irritative factors • anti-inflammatory therapy • bronchodilator therapy • hyposensitization Chronic obstructive pulmonary disease(CHOPN, COPD) • 5-20% of the adult population • 30 x more common in smokers • Mortality - 5th place • includes: – chronic bronchitis – pulmonary emphysema 1. Chronic bronchitis Clinical definition: disease with hypersecretion of mucus associated with chronic cough for at least three months in a year, for 2 consecutive years, to the exclusion of other pulmonary and cardiac diseases. Chronic bronchitis - etiology • cigarette smoking • occupational exposure (oxides of S, N, formaldehyde) • air pollution • repeated respiratory infections Chronic bronchitis - morphology • hyperplasia and hypertrophy of mucous glands • excess mucus in the airways • inflammatory infiltration and swelling of the airway wall (narrowing) Chronic bronchitis – functional consequences • constriction of small airways → expiratory obstruction - ↓ dynamic parameters → hypoxemia (cyanosis), hypercapnia and respiratory acidosis → normal pulmonary diffusion capacity for O2 2. Emphysema- ethiopathogenesis • imbalance in proteases and antiproteases – ↑ elastase • Smoking → inflammation → neutrophils – ↓ α1-antitrypsin • smoking • genetic defect (MM homozygotes to 40 years) • obstruction of bronchioles Emphysema Healthy lungs Emphysematic lungs COPD – clinical symptoms • increasing difficulty in breathing (years) • shortness of breath, productive cough • mainly bronchitis x mainly emphysema COPD - treatment • Influencing of obstruction (bronchodilator) • Influencing of infection (antibiotics) • Removing mucus (expectorants) • Oxygen therapy • Rehabilitation, spa • Surgical therapy • Substitution of α1-antitrypsin Tobacco smoke Continuous irritation and inflammation of the bronchi Chronic bronchitis Damage of elastin and connective tissue of the lungs Emphysema COPD Restrictive lung disorders • restriction – reduction of functional lung parenchyma or limitation of respiratory movements – limited expansion of the lung: • from external causes (resection, pleural disease, chest wall, neuromuscular system, extreme obesity .....) • change in the lung parenchyma (inflammation, tumor, interstitial lung disease usually combined with impaired diffusion) Restrictive lung disorders Spirometry The terms to describe breathing Definitions of certain pulmonary function parameters Limitation of spirometry • measured only exchanging volumes during breathing (no residual volumes) • measured under the nonphysiological conditions • requires the cooperation of the patient Spirometric values • static = time independent • dynamic = time dependent Principles of spirometers Static lung volumes • TLC - total lung capacity (about 6 l) • RV - residual volume (spirometer can not measure!) • ERC - expiratory reserve volume (about 1.5 liters) • IRV - inspiratory reserve volume (about 2.5 liters) • FRC - functional residual capacity ERV + RV • VC - vital capacity, TLC-RV • tidal volume of about 0.5 l Dynamic parameters • FVC - forced vital capacity ("as much and as quickly as possible") • FEV1 - expiration-second capacity • FEV1/FVC - second capacity for FVC ratio • FEF25-75% - average flow velocity in the middle half of the FVC • PEF - peak expiratory flow rate • Vmax 50%, 25% Vmax - maximal flow after exhalation 50% respectively. 75% of vital capacity Loop flow/volume Volume-time curve Loop flow/volume Spirometry in obstructive disorders • dynamic ventilation parameters ↓ – volumes during forced exhalation • FEV1 ↓, ↓ FEV1/FVC (%), standard 80%, FVC ± ↓ – flow (velocity) • PEF ↓, ↓ MEF 50%, MEF ↓ 75% ↓ 25% MEF • ↓ FEF 25-50% • static lung volumes ↑ – residual volumes • ↑ RV, FRC ↑, ↑ TLC Spirometry in restrictive disorders • static lung volumes ↓ – residual volumes – ↓ RV, FRC ↓, ↓ TLC • Dynamic ventilation parameters ± ↕ – volumes during forced exhalation • ↓ FEV1, ± ↑ FEV1/FVC (%), standard 80%, FVC ↓ – flow (velocity) – PEF ↓, ↓ MEF 50%, MEF ↓ 75% ↓ 25% MEF ± ↑ FEF 25-50% Obstructive diseases FEV1 > 80% predicted normal 65 - 80% mild 50 - 65% moderate < 50% severe Meas Pred %Pred FVC 2.63 3.11 84 FEV1 1.58 2.28 69 FEV1/FVC 60 73 FEF25-75 0.59 2.56 23 PEF 4.90 5.78 85 Meas Pred %Pred FVC 0.96 2.75 35 FEV1 0.94 1.90 49 FEV1/FVC 98 69 FEF25-75 2.25 2.11 107 PEF 2.98 5.40 55 Restrictive diseases Algorithm for spirometry interpretation Obstruction Restriction Peak flow meter • Peak flow meter is a small device that monitors the flow of air through the bronchi and helps to detect any obstruction in the airway. • Peak flow meter measures the ability or peak expiratory flow or peak expiratory flow rate (PEFR or PEF). • PEF is higher in the physiological condition of the patient, at lower values ​​infer constriction. • From changes in the measured values, we can determine the patient's condition, or appropriate therapy.