Influence of apnoeic oxygenation in respiratory and circulatory system under general anaesthesia

Abstract

Apnoeic oxygenation is an alternative technique of oxygenation which is recommended in the consecutive oxygen administration with varying flows (2-10 lt/min) through a catheter which is positioned over the keel of the trachea. Apnoeic oxygenation maintains for a significant period of time the oxygenation of blood in breathless conditions. This technique was first applied in 1947 by Draper, Whitehead, and Spencer and it was studied sporadically by other inventors too. However, the international literature shows few studies that have examined closely apnoeic oxygenation and its effects on Hemodynamic image and the respiratory system of the human body. Recently they have begun to arise some studies which deal with the application of this technique in several conditions such as difficult tracheal intubation, ventilation of guinea pigs in campaign conditions where the oxygen supply is limited and calculable, the application of this technique in combination with the use of extracorporeal removal of carbon dioxide (CO2). All the above indicate, the clinical use of this technique.

Keywords: Tracheal apnoeic oxygenation; hemodynamic status; hypercapnic acidosis; oxygenation indices.

Figure 1

Variation of PO₂ in pulmonary capillary with two different approaches.

Figure 2

Transportation of air mass from the air vents to the cuvette.

Figure 3

Variation of alveolar and oral PCO₂ during respiratory circle.

Figure 4

Hydrostatic analogue of the removal of carbon dioxide.

Figure 5

Changes in end expiratory carbon dioxide after sudden changes of alveolar ventilation. During the fall of PCO₂ (hyperventilation) the half change comes in three minutes while during the increase in PCO₂ (hypoventilation) half change comes in 16 minutes.

Figure 6

Changes in concentration of catecholamines in dogs’ plasma during the increase in P_aCO₂ (from 22 to 338 mmHg) at apnoeic oxygenation during one hour. After ventilation 10^’ and return of P_aCO₂ in 24 mmHg, catecholamines decreased in initiate levels.

Figure 7

Distribution of positive pressure from the mechanical ventilation of the lungs within the thoracic cavity. Implementation of intrathoracic pressure on the heart and vascular formations. 
P_{Θ =}P_{intrathoracic,} P_δτ = P_trasnmular, P_{MV =} P_{mechanical ventilation,} C_ΘΤ = compliance of chest wall, C_πν = lungs’ compliance.

Figure 8

Relation of cross section of trachea and probe blow. The remainder space has A-α cross section.