Respiratory System John P. McDonough, CRNA, Ed.D., ARNP

Pulmonary System Structures n Lungs n Airways –(upper & lower) n Vasulature n Chest wall

Lungs n Right –upper, middle & lower n Left –upper & lower n Lobes  segment  lobules n Mediastinum –contains heart, great vessels, esophagus

Conducting Airways (upper) n Nasopharynx n Oropharynx n Laryngopharynx

Conducting Airways (lower) n Larynx n Trachea –divides at the carina n Bronchi

Conducting Airways (lower) n Lobar bronchi n Segmental bronchi n Subsegmental bronchi (nonrespiratory)

Gas Exchange Airways (Respiratory Unit) n Subsegmental bronchi (respiratory) n Terminal bronchioles n Alveolar ducts n Alveoli

Bronchial Walls n Epithelial lining –exocrine gland cells, ciliated cells n Smooth muscle n Connective tissue

Alveoli n 25 (birth)  300 (adulthood) million n Where most gas exchange takes place –alveolocapillary membrane n Secretes surfactant

Pulmonary Circulation n Facilitates gas exchange n Delivers nutrients to lung tissue n Reservoir for the left ventricle n Filter for the circulation n Less pressure & resistance than systemic –MAP 18 Vs 90 n 100 ml blood / m 2 n Bronchial circulation  pulmonary

Thoracic Cavity n Chest wall n Diaphragm n Lungs n Pleura –visceral & parietal n Mediastinum n Heart & great vessels

Volumes & Capacities n Alveolar dead space n Alveolar ventilation n Anatomic dead space –1 ml / pound, 33% of each breath n Dead-space ventilation n Functional residual capacity n Minute volume

Volumes & Capacities (continued) n Physiologic dead space n Residual volume n Tidal volume n Total lung capacity n Vital capacity

Control of Ventilation n Voluntary Vs involuntary n Respiratory center (brain stem) n Chemoreceptors

Lung Receptors n Irritant –epithelium of conducting airways n Stretch (Herring-Breuer reflex) –smooth muscle of airways n J-receptors (juntapulmonary) –capillaries of alveolar septa

Chemoreceptors n Monitor pH, Pa CO 2 & Pa O 2 n Central chemoreceptors –near respiratory center –sense change in pH by H + ion in CSF n Peripheral chemoreceptors n H + changes  Pa CO 2 n CO 2 + H 2 O  H 2 CO 3  HCO 3 + H +

Chemoreceptors (continued) n  ventilation  Pa CO 2 n CO 2 diffuses across blood/brain barrier n H +  pH  n Center  rate & depth of respiration n Center sensitive to small changes (1-2 Torr) n Chronic disease will desensitize receptor

Chemoreceptors (continued) n Peripheral receptors n Aortic arch, aortic bodies, carotid bodies n Some sensitivity for Pa CO 2 & pH n Primarily react to Pa O 2 n Marked hypoxia (Pa O 2 <60 Torr) required

Mechanics of Breathing n Muscles are usually for inspiration only n 2 major muscles –intercostal & diaphragm n Accessory muscles n sternocleidomastoid & scalenes

Mechanics of Breathing (continued) n Alveolar surface tension –surfactant reduces it –Law of Laplace P= (2T/r) n Elasticity n Compliance

Airway Resistance (Poiseuille’s Law) n 50-66% occurs in the nose n Next highest, oropharynx & larynx n Should be little in lung conducting airways n Except in: –edema –obstruction –bronchospasm

Gas Transport n Intake of O 2 by Ventilation of the lungs n Diffusion of O 2 across PCM n Systemic capillaries get arterial blood n Diffusion of O 2 into cell n Diffusion of CO 2 into systemic capillaries n Pulmonary capillaries get venous blood n Removal of CO 2 by ventilation of the lungs

Tests of Pulmonary Function n Spirometry –measures volumes and capacities n Diffusing capacity –measure ability for gas transport across PCM n Arterial blood gas analysis n Radiographs –chest x-ray

Arterial Blood Gases n ArtVenous n pH n P CO 2 mm Hg n P O 2 mm Hg n HCO 3 - mEq/L n S O %70-75% n Base Excess-2 to +20 to +4

Effects of Aging n Loss of elastic recoil n Stiffening of the chest wall n Alterations in gas exchange n Increases in flow resistance n All influenced other factors –environmental, disease, body size, race & gender

S/S of Pulmonary Disease n Dyspnea –exertional, orthopnea, PND n Abnormal breathing patterns –Kussmaul, “purse lipped”, Cheyne-Stokes n Hypo/hyperventilation n Cough n Hemoptysis

S/S of Pulmonary Disease (continued) n Cyanosis n Pain n Clubbing n Abnormal sputum

Conditions Caused by Pulmonary Disease n Hypercapnia n Hyoxia n Acute respiratory failure n Pulmonary edema n Aspiration n Bronchiolitis

Conditions Caused by Pulmonary Disease (continued) n Pneumothorax n Plural effusion n Pulmonary fibrosis n Pneumoconiosis

Chronic Bronchitis n Occurs for at least 3 months, in 2 years n 20 X increase in smokers n Inflammation of bronchi (irritants/infection) n Muscle hypertrophy n Mucus gland hyperplasia n Inflammation n H. flu (Haemaphilus influenzae) & Streptococcus pneumoniae are common

Emphysema n Permanent  size of gas exchange airways n Destruction of alveolar walls n Obstruction from anatomical change n Primary- 1-2% of cases –  1 -antitrypsin deficiency (70-80% likelihood) n Secondary most common

S/S of Emphysema n Dyspnea on exertion  at rest n Often no cough and little sputum n Thin patient n Tachypnea n Prolonged expiration

Chronic Obstructive Pulmonary Disease n Includes chronic bronchitis & emphysema n Next to heart disease as cause of death in adults <65 n >33% of all VA patients have COPD n smoking is the primary cause

Asthma n Reactive airways and bronchospasm n Extrinsic (most common) –mast cell activation –triggered by dust, mold, pollen, etc n Intrinsic –no known allergic cause –seen in adults >35 and often severe –triggered by drugs, irritants, infections, cold

Asthma (continued) n Inflammation  hyperresponsiveness n Thickening of airways –edema, vascular congestion,  mucus n Muscle (bronchial) spasm

Asthma (continued) n Sensation of chest constriction n Wheezing (inspiratory & expiratory) n Dyspnea n Cough (often non-productive) n Prolonged inspiration n Tachycardia n Tachypnea