68. Respiratory failure.

Lungs ventilation is disturbed due to respiratory apparatus pathological changings. It is useful to differentiate 2 ventilation disturbances types: restrictory and obstructive.

Restrictive type: all pathological states at which lungs respiratory excursions are decreased.

Obstructive: it is determined by air ways constriction and thus aerodynamic resistance increasing.

Probes which allow to determine one or another disorders type:

• lungs vital capacity (its decreasing is a restrictive type feature);

• prolonged expiration volume and duration on Wotchall-Tiffno method (obstructive disorders index);

• respiration reserve (restrictive disorders index);

• maximal lung ventilation (it is reduced both in course of restrictive and obstructive ventilation disorders).

For differential diagnostics one should determine vital lung capacity and prolonged expiration volume. All these indexes determining is performed on spirogram.

69. External respiratory failure. Dyspnea.

Respiratory insufficiency – pathological state at which external respiration system can not provide blood gases normal content (gas homeostasis).

Acute – is developed during several days, hours or even minutes – asphyxy is a bright example.

Chronic – during long time, it is a result of bronchi and lungs pathological states – chronic pneumonia, pneumosclerosis, lungs emphysema.

Compensated – without blood gas content changing.

Decompensated – with gas homeostasis disorders.

Ventilational – due to gases exchange disorders between atmospheric air and lungs alveoles, id est as a result of pulmonary ventilation disorders (hypoventilation):

1. restrictory;

2. obstructive;

3. dysregulatory – respiration central regulation disorders.

Parenchymatous

Obstructive – cough, dyspnea, airways obstruction.

Restrictive – without dyspnea, pulmonary tissue injury.

Dyspnea – feeling of air lack and necessity to enforce breathing connected with it.

Reasons:

1. blood bad oxygenation in lungs (oxygen partial pressure decreasing in inspirited air, pulmonary ventilation and pulmonary circulation disorders);

2. gas transport with blood disorders (anaemia, circulatory insufficiency);

3. thorax and diaphragm movement retardation;

4. acidosis;

5. metabolism enforcement;

6. CNS functional and organic problems (strong emotional influencings, hystery, encephalitis, brain circulation disturbances).

Mechanism. Dyspnea occurs at dominance of influencings activating inspiration or respiratory center sensitivity increasing to them:

1. excitement of receptors stimulating inspiration center – they are activated at pulmonary alveoles volumes strong decreasing (stronger than at maximal expiration); there can be constant impulsating from them at pathology.

2. J-receptors excitement – all pathological processes leading to stagnational phenomena in lungs (pneumonia, heart insufficiency) can cause J-recepors prolonged excitement and respiratory neurons increased stimulation.

3. Reflexes from irritant receptors of airways – specially at obstructive forms but also at pneumonia.

4. Reflexes from aorta and carotid artery baroreceptors (are involved at blood loss, shock, collapse; at arterial pressure equal to 70 mm merc col and lower impulses flow inhibiting inspiration center is activated and depressor center is activated.

5. Reflexes from aorta and carotid artery chemoreceptors oxygen tension decreasing, carbonic dioxide tension increasing, hydrogen level increasing lead to inspiratory center activation.

6. Direct stimulation of medulla oblongata respiratory neurons.

7. Reflexes form respiratory muscles and diaphragm – at lungs elasticity decreasing, superior respiratory ways constriction.

8. Respiratory center stimulation with products of own metabolism: brain circulation disorders lead CO2, acid metabolism products accumulation and oxygen tension decreasing directly in nervous centers.

Inspiratory dyspnea – at inspiration center stimulation, expiratory – expiratory one.