Intrapulmonary shunt (Qsp) includes functional shunt (QvA) and anatomical shunt (Qs). The former is caused by the imbalance of V/Q ratio, and the latter is caused by the pulmonary blood flow directly mixed into the pulmonary vein system due to anatomical defects, and also includes capillary shunt at V/Q=0. The Qs/Qt calculation formula is as follows (PA-aDO2×0.0331)/PA-aDO2X0.0331+(CaO2-CvO2). It is used to understand physiological flow and assist in the diagnosis and evaluation of cardiopulmonary diseases.

Basic Information

Specialist classification: Respiratory examination classification: pulmonary function test

Applicable gender: whether men and women apply fasting: not fasting

Tips: Before the examination, the subjects should be explained in detail about the inspection methods and essentials, and do adaptive training. Normal value

Normal people breathe air with Qs/Qt of 2% to 5% and are positively correlated with age.

Clinical significance

Abnormal results:

Increased right-to-left shunt congenital heart disease, atelectasis and lung collapse, lung infection, alveolar hemorrhage, pulmonary edema, ARDS.

Need to check the crowd:

This test can be performed for patients with cardiopulmonary disease for diagnosis and evaluation.

High results may be diseases: throat, atelectasis, congenital heart disease considerations

Requirements for inspection:

(1) Before the examination, the subjects should be explained in detail about the inspection methods and essentials, and adaptive training should be done.

(2) Quiet rest before the measurement of resting ventilation, should be carried out completely under the basal metabolic state, the surrounding environment is quiet, and the breathing is required to be stable.

(3) Since the dead volume can not be directly measured, the dead air volume can be calculated by measuring the minute resting ventilation and the exhaled CO 2 partial pressure, thereby obtaining alveolar ventilation. Clinically, PaCO2 is often used to reflect the adequacy of alveolar ventilation.

(4) Due to the difference in measurement methods and instruments, and the degree of cooperation of the subjects, the maximum range of maximum ventilation is large. The normal range is generally taken as a percentage of the predicted value of ±20%.

(5) The forced vital capacity and the maximum expiratory mid-flow volume were all affected by the degree of forced exhalation during the examination. The former had a greater impact.

(6) The sex, age, height and muscle strength of the subject may affect the results of the above examination.

Not suitable for people:

1 severe heart and lung disease, weak body.

2 mental disorders or can not be well coordinated.

Inspection process

Data were obtained after routine induction and insertion of double lumen bronchial catheter for 20 min after single lung ventilation, and the relevant results were calculated.

Not suitable for the crowd

1 severe heart and lung disease, weak body.

2 mental disorders or can not be well coordinated.

Adverse reactions and risks

Generally no complications and harm.