Respiratory failure diagnosis and differential diagnosis

Respiratory failure diagnosis and differential diagnosis

Chronic respiratory failure decompensated period, according to patients with chronic respiratory diseases or other respiratory dysfunction leading to the history, missing O2 and (or) CO2 retention of clinical manifestations, with the relevant signs, the diagnosis is not difficult. Arterial blood gas analysis of respiratory failure can objectively reflect the nature and extent of the guidance of oxygen therapy, mechanical ventilation various parameters of the regulation, and correct pH balance and electrolytes are important values.

1. PaO2 (PaO2)

Refers to the physical dissolved in the blood oxygen molecules generated by the pressure. PaO2 healthy growth decreased gradually with age, and physiological effects of receptor. According to partial pressure of oxygen and oxygen saturation of the relationship between oxygenated hemoglobin dissociation curve was S shape, when PaO2> 8kPa (60mmHg) above, the flat of the curve, the oxygen saturation of more than 90%, PaO2 change 5.3 kPa (40mmHg ), But little change in oxygen saturation that much oxygen saturation of oxygen-sensitive, but when PaO2 <8kPa below, the steep curve, the slight decline in oxygen pressure, oxygen saturation sharp decline, the PaO2 Less than 8 kPa (60mmHg) as the diagnosis of respiratory failure indicators.

Second, the arterial blood oxygen saturation (SaO2)

Hemoglobin is the oxygen percentage of units, the normal value is 97 per cent. When PaO2 less than 8 kPa (60mmHg), hemoglobin oxygen dissociation curve in a steep section, the oxygen saturation only reflects the state of hypoxia, the severe respiratory failure in the rescue, with the pulse of oxygen saturation detector to help evaluate missing O2 level, adjust the absorption of O2 concentration SaO2 more than 90%, to reduce the trauma of pumping blood for blood gas analysis, which is a reasonable assessment effect of oxygen therapy and play an active role.

3, arterial blood oxygen content (CaO2)

100 ml of blood is the number of oxygen-ml. Including the combination of hemoglobin and oxygen dissolved oxygen in plasma physics combined. CaO2 = 1.34 × SaO2 × Hb +0.003 × PaO2. Healthy CaO2 reference value of 20 ml%. Mixed blood oxygen saturation (SVO2) to 75 percent, its oxygen content CVO2 for 15 ml%, per 100 ml blood by the organization after about 5 ml of oxygen for the organization to use. Hemoglobin reduction, SaO2 lower than normal, blood oxygen content can still be the normal range.

4. PaCO2 (PaCO2)

Refers to the physical dissolved in the blood of the CO2 produced by the pressure. PaCO2 normal for the 4.6 kPa-6kPa (35-45mmHg), more than 6 kPa for inadequate ventilation, less than 4.6 kPa for ventilation may be excessive. Acute lack of ventilation, PaCO2> 6.6kPa (50mmHg), according to Henderson-Hassellbalch formula, pH below 7.20, it will affect circulation and cell metabolism. Chronic respiratory failure due to the body compensatory mechanisms, PaCO2> 6.65kPa (50mmHg) as an indicator of respiratory failure.

5, pH value

For the hydrogen ion concentration in the blood of a negative value. The normal range of 7.35-7.45, an average of 7.40. Below 7.35 for decompensated acidosis, higher than the 7.45 for decompensated alkalosis, but could not explain what is the nature of the acid-base poisoning. Clinical symptoms and the pH is closely related to migration.

6, base excess (BE)

In 38 ℃, CO2 pressure 5.32 kPa (40mmHg), oxygen saturation measured 100 percent condition, blood titration to the pH of pH7.4. It is human metabolic acid-base balance of quantitative indicators, plus acid to BE positive of the metabolic alkalosis; Canadian base of EB was negative, of metabolic acidosis. The normal range of 0 ± 2.3mmol / L. In the correct metabolism of the acid-base imbalance, it can be used as estimated by acid or Kangjian dose drug reference.

7. Buffer base (BB)

Various buffer in the blood of the total content of alkali, including bicarbonate, phosphate, plasma protein salt, salt and other hemoglobin. It reflects human interference buffer against acid-base capability, and acid-base imbalance in the body of the specific circumstances of compensation. Normal for the 45 mmol / L.

8, the actual bicarbonate (AB)

AB is in the actual partial pressure of carbon dioxide and oxygen saturation of human plasma bicarbonate contained in the content. Normal for the 22-27 mmol / L, an average of 24 mmol / L. HCO3-related content and PaCO2, as PCO2 increased plasma HCO3-content has also increased. On the other hand HCO3-alkali plasma one of the buffer, when too much acid in fixed, by HCO3-buffer and pH stability, and HCO3-content reduction. So AB double by respiratory and metabolic effects.

9, the standard bicarbonate (SB)

Means isolated from the blood samples of air in 38 ℃, PaCO2 to 5.3 kPa, oxygenated hemoglobin 100 percent under the conditions, measured by the plasma bicarbonate (HCO3-) content, for the normal 22 - 27mmol / L, An average of 24 mmol / L. SB from respiratory factors, to reflect the increase or decrease its value in HCO3-the number of reserves, so that metabolic factors and extent of the trend. Metabolic acidosis, SB decreased metabolic alkalosis, SB increased. AB> SB, expressed CO2 retention.

10, the combination of carbon dioxide (CO2CP)

Normal for the 22-29 mmol / L, the main base in the reserves. Metabolic acidosis, or respiratory alkalosis, CO2CP lower metabolic alkalosis or respiratory acidosis, while CO2CP increased. However, respiratory and metabolic acidosis with acid poisoning, CO2CP not necessarily increased, due to respiratory acidosis, kidney or to NH4 + H + form from the H +, to compensate for HCO3-absorption, alkali reserve increase, the increase in the CO2CP Certain extent, respiratory acidosis reflect the seriousness of the blood but can not reflect the dramatic changes in CO2, but also by the metabolism of the base or acid poisoning effect, it has its one-sidedness CO2CP, must be integrated with clinical and electrolyte for full consideration.

These indicators to PaO2, PaCO2 and pH most important, reflecting the lack respiratory failure at the O2, CO2 retention, in an acid-base imbalance, such as adding BE will be able to reflect the body compensatory, or without metabolic acid or alkaline Poisoning, and electrolyte imbalance.