RESPIRATORY

RESPIRATORY

Physiology

Lung volumesInspiratory reserve volume air that can be breathed in after normal inspirationTidal volume air that moves into the air with each inspiration (tide)Expiratory reserve volume air that can be breathed out after normal expirationResidual volume air in the lung after maximal expiration. Cant be measured through spirometeryLung capacitiesInspiratory Capacity IRV + TVFunctional Residual Capacity ERV + RVVital Capacity IRV + ERV + TVTotal Lung Capacity IRV +ERV + TV+ RV

Physiological dead space VD = VT x PaCO2 PeCO2 --------------------------------- PaCO2Lung and Chest wallAt FRC, inward pull of lung is balanced by outward pull of chest wall, leading to system pressure being atmosphericCompliance change in lung volume for a given change in pressure in pulmonary fibrosis, pneumonia, and pulmonary edema in emphysema and normal aging

MethglobinOxidized from Hb that does not bind to O2 as readily but has affinity for cyanideMethglobinemia may present with cyanosis an chocolate colored bloodTo treat cyanide poisoning, use nitrates to oxidize Hb to methglobinUse Thiosulfate to bind this cyanide forming thiocyanateTx: Methemoglobinemia treatment is Methylene BlueOxygen-Hemoglobin dissociation curveBAT ACEBPGAltitudeTemperatureAcidCO2Exercise in all factors leads to a Right shiftin all factors leads to a Left shift

Pulmonary Vascular ResistancePVR = P pulm artery P L. atrium (wedge pressure)-----------------------------------------------------------Cardiac OutputV/Q mismatchApex of the lung has V/Q of 3 (high O2 content, TB flourishes here)Base of the lung has V/Q of 0.6V/Q 0 = airway obstructionV/Q infinity = blood flow obstructionPathologyRhinosinusitisObstruction of sinus drainage into nasal cavityInflammation and pain over affected areaSuperimposed bacterial infection S. pneumo, H. influenza, M. catarrhalisDeep venous thrombosisPredisposed by Virchow triad:StasisHypercoagulability (defect in Factor V)Endothelial damage (exposed collagen triggers clotting cascade)Homan sign dorsiflexion of foot calf pain.Tx: Heparin for acute management. Warfarin for long term prevention.Pulmonary emboliV/Q mismatch hypoxemia respiratory alkalosis. Sudden onset dyspnea, chest painMay present as sudden deathFAT BATFat emboli long bone fractures. Hypoxemia, neurologic abnormalities, petechial rashAmniotic fluid emboli can lead to DIC, especially postpartumGas emboli nitrogen bubbles percipitate in ascending divers. Treat with hyperbaric oxygen

Pulmonary hypertensionNormal pulmonary artery pressure = 10-14 mmHg. Pulmonary hypertension > 25 mmHg at restResults in arteriosclerosis, medial hypertrophy, and intimal fibrosis of pulmonary arteriesPrimary due to an inactivating mutation in the BMPR2 gene. Poor prognosis.Secondary due to COPD (destruction of lung parenchyma), mitral stenosis, recurrent thromboemboli, autoimmune disease (systemic sclerosis), left to right shunt, sleep apneaSevere respiratory distress cyanosis and RVH death from Cor PulmonaleSleep apneaRepeated cessation of breathing > 10 seconds during sleepNormal PaO2 during the dayNocturnal hypoxia systemic/pulmonary hypertension, arrhythmias (atrial fibrillation/flutter), and sudden deathCentral sleep apnea no respiratory effortObstructive sleep apnea respiratory effort against airway obstruction. Associated with obesity, loud snoringLung cancer