Respiratory Insufficiency & Other Clinical Conditions

Dr. Niranjan Murthy H L Asst Professor of Physiology SSMC, Tumkur

RESPIRATORY INSUFFICIENCY • Narcosis, other pharmacologic influences, hypoxia, and pathologic processes  reduce excitability of respiratory neurons  respiratory failure

Narcotic drugs & respiratory depression: Leads to reduced PaO2 & increased PaCO2. Carries best prognosis & amenable to Rx. Narcotic drugs also diminish metabolism. Complications of narcotic poisoning(vi) Asphyxia (vii)Microbial infections (viii)Circulatory depression (ix) Renal functional derangements (x) Hypo or hyperthermia (xi) Consequences of therapeutic measures

• Asphyxia- depression of PaO2 and elevation of PaCO2; assisted ventilation. • Circulatory depression- due to central vasomotor depression, hypoxemia, and direct narcotic effects on blood vessels; blood supply of brain is maintained due to hypercapnia induced cerebral vasodilatation; support of circulation. • Hypothermia- due to reduced metabolism & deranged heat regulating mechanisms; hyperthermia in case of infections

• Renal impairment- due to hypotension • Respiratory insufficiency due to pulmonary pathologies: (i) Pulmonary Emphysema (ii) Pneumonia (iii) Atelectasis (iv) Asthma (v) Tuberculosis

Pulmonary Emphysema • Excessive air in lungs • Causes- chronic infections, chronic smoking. • Physiologic abnormalities(i) Increased airway resistance (ii) Destruction of alveolar walls  reduced diffusing capacity  increased PaCO2 & reduced PaO2 (iii) Reduced alveolar capillaries  pulmonary hypertension  right heart failure

Pneumonia • Inflammatory condition of respiratory membrane • Alveoli are filled with fluid and blood cells • Most common- bacterial- pnemococcal • Reduction in total available area for gas exchange • Decreased VA/Q • Hypoxemia and hypercapnia

Atelectasis • Collapse of alveoli / lobe / lung • Causes- (i) Airway obstruction and (ii) lack of surfactant • Hyaline Membrane Disease is fatal

Asthma • • • •

Airway hyper-responsiveness Allergic hypersensitivity- pollen Older people- pollution Histamine, SRS-A, ecf, bradykinin are released from mast cells • Localized edema in walls of airways and spasm of bronchiolar smooth muscles • Reduced PEFR and FEV1 • Increase in FRC and RV

Tuberculosis • • • • • • •

Mycobacterium tuberculosis Tubercle- due to walling off of infection Cavitation- in untreated cases Fibrosis- in late stages Reduced VC Reduced surface area and increased thickness of respiratory membrane Abnormal VA/Q

Apnea •

Cessation of breathing (generally temporary) (ii) Reduction in stimulus to respiratory centre (iii) Active inhibition of respiratory neuronsprolongation of Hering-Breuer reflex (iv) Decreased ability of respiratory neurons to react to stimuli- narcotics

Dyspnea •

Labored, distressful breathing with conscious effort • Factors leading to dyspnea (iii) Abnormality of respiratory gases in body fluids (iv) Amount work to be performed by respiratory muscles (v) State of mind

Disorders of rhythm Cheyne-Stokes respiration: • Periodic breathing • Seen in congestive heart failure, uremia, brain disease and sleep. • Prolongation of circulation time • Increased sensitivity to CO2