Low oxygen pressure

Introduction The partial pressure of oxygen is the tension generated by oxygen dissolved in the blood. The arterial partial pressure of oxygen (PaO2) is about 13.3 kPa (100 mmHg), depending on the oxygen partial pressure of the inhaled gas and the respiratory function of the lung. Venous oxygen partial pressure (PvO2) is normally about 5.32 kPa (40 mmHg), which reflects the internal breathing. There are two situations. One is that the patient has a atrioventricular deficiencies and there is pulmonary hypertension. After the left heart pressure is lowered, the right-to-left shunt appears or increases, resulting in a decrease in oxygen partial pressure. The other is the critical ventilated blood flow. In the case of disorders (such as atelectasis), nitroglycerin can aggravate the imbalance of ventilated blood flow in the lungs, causing hypoxemia.

Cause

There are two situations. One is that the patient has a atrioventricular deficiencies and there is pulmonary hypertension. After the left heart pressure is lowered, the right-to-left shunt appears or increases, resulting in a decrease in oxygen partial pressure. The other is the critical ventilated blood flow. In the case of disorders (such as atelectasis), nitroglycerin can aggravate the imbalance of ventilated blood flow in the lungs, causing hypoxemia.

The pathological decrease in pO2 is mainly seen in hypoxemia caused by various diseases, and the pO2 is generally less than 55 mmHg. The following can be seen:

Respiratory central dysfunction, such as idiopathic alveolar hypoventilation syndrome, encephalitis, pulmonary hemorrhage, brain trauma, hypoparathyroidism, CO2 anesthesia or sedative overdose or poisoning. Neuromuscular disorders, such as cervical spine injury, multiple sclerosis, myasthenia gravis, muscle atrophy, etc. Thoracic and diaphragmatic disorders, rib fractures, severe curvature of the spine, diaphragmatic paralysis, acute pancreatitis, high pleural effusion, extreme obesity, etc. Chronic bronchitis, emphysema, bronchial asthma, pulmonary infarction, heart failure, etc. can also cause hypoxemia. Respiratory failure index table.

Blood carbon dioxide partial pressure: refers to the pressure generated by the physically dissolved CO 2 in the blood. This is an indicator of respiratory acid and alkalosis, and it can also help to understand the ventilation of alveoli.

an examination

Related inspection

Oxygen partial pressure

Fio244%, under normal circumstances, PaO2 should be 200~250mmhg, the patient has only 70 mmhg airway pressure is not high, and there is no obvious secretion in sucking, there is no air leakage in manual ventilation, obviously there is oxygen exchange disorder, diffusion disorder, ventilation Blood loss adjustment, or shunt, change fio244% to 67%, spo2 gradually rose to 95%, blood gas analysis showed oxygen partial pressure of 66mmhg, spo2 was 92%, oxygen index was 100 at this time, highly suspected lung injury.

Differential diagnosis

Oxygen partial pressure is the pressure shared by oxygen in the gaseous state, and is classified into the following items: mild failure, moderate failure, and severe failure.

Oxygen saturation (%) 8090 6080 Less than 60 pO2(mmHg) 5055 4050 3040 pCO2(mmHg) 5570 7090 More than 90 fio244%, under normal circumstances, PaO2 should be 200 ~250mmhg, the patient only 70 mmhg airway pressure is not high, and there is no obvious secretion of sucking, there is no leakage of air in the hand-controlled ventilation, there is obviously an oxygen exchange disorder (dispersion disorder, ventilated blood loss, or shunt, change fio244% 67%, spo2 gradually rose to 95%, blood gas analysis showed that the oxygen partial pressure was 66mmhg, spo2 was 92%, the oxygenation index was 100, and the lung injury was highly suspected.

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