DYSPNEA & ABNORMAL TYPES OF RESPIRATION

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-

1.Asphyxia

2.Microbial infections

3.Circulatory depression

4.Renal functional derangements

5.Hypo or hyperthermia

6.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-

1.Increased airway resistance

2.Destruction of alveolar walls - reduced diffusing capacity - increased PaCO2 & reduced PaO2

3.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

1.Reduced VC

2.Reduced surface area and increased thickness of respiratory membrane

3.Abnormal VA/Q

Apnea

• Cessation of breathing (generally temporary)

1.Reduction in stimulus to respiratory centre

2.Active inhibition of respiratory neurons- prolongation of Hering-Breuer reflex

3.Decreased ability of respiratory neurons to react to stimuli- narcotics

Dyspnea

• Labored, distressful breathing with conscious effort
• Factors leading to dyspnea -

1.Abnormality of respiratory gases in body fluids

2.Amount work to be performed by respiratory muscles

3.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