425 Hypoxemia

Su Yang carefully studied Yang Fei's illness.

The first priority at present is to improve the patient's physical condition first, that is, increase the patient's blood oxygen content.

That is, symptomatic treatment.

Acute hypoxic respiratory failure is a common group of life-threatening diseases in the emergency department. In addition to eliminating the cause, different oxygen therapy methods need to be selected according to the severity of the disease.

For transnasal catheters, ordinary masks, oxygen storage masks, high-flow oxygen therapy systems [humidified heating high-flow nasal catheter ventilation, highflow-      cannula, hfnc] and non-invasive mechanical ventilation, patients with severe acute hypoxia and severe hypoxic respiratory failure who are not suitable for the above oxygen therapy methods, they often need to establish artificial airways for advanced and complex respiratory support technologies. However, there are still some debates about such patients in terms of the choice of treatment strategies or the order of use of treatment measures.

Although pulmonary protective ventilation strategies such as small tidal ventilation, controlling platform pressure, optimal end-expiratory pressure (peep) and lowering inspiratory drive pressure (Δp) have been proposed for many years, it has not received due attention in emergency clinical practice. Some patients with severe acute hypoxic respiratory failure have not received appropriate treatment or effectively corrected hypoxemia, and ventilator-induced lung injury (ventilator-induced    -lung-      injury,vili) have also occurred to varying degrees.

Therefore, Su Yang has to think about Yang Fei's treatment, even if it is just a symptomatic treatment.

He first entered the system space and began to search for information.

By looking up a large amount of information, Su Yang found that in the past few years, the use of high-flow nasal catheter oxygen therapy for the treatment of acute non-hypoxemia respiratory failure caused by different causes has been increasing.

A summary of previous research results shows that compared with traditional oxygen therapy, high-flow oxygen therapy has better tolerance, comfort, and reduces breathing difficulties.

Another three studies comparing the intubation rate showed that high-flow oxygen therapy is not inferior to standard oxygen therapy or non-invasive positive pressure ventilation.

In the journal Lancet Respiratory Journal, jean-pierre   -frat and colleagues published a post hoc analysis to include critical respiratory failure patients with acute hypoxemia to compare different noninvasive oxygen therapy methods. The researchers reported that 82 immunized patients with low tracheal intubation risk increased compared to patients who received only high flow oxygen therapy or standard oxygen therapy, p=0.048.

Both high flow oxygen therapy and standard oxygen therapy can reduce the rate of tracheal intubation in patients with immunity and have similar prognosis. Early reports by frat and colleagues showed that high flow oxygen therapy can reduce 90-day mortality in patients with unselected acute hypoxic respiratory failure compared with non-invasive ventilation and standard oxygen therapy.

In view of this, high-flow oxygen therapy should be the focus of future management of acute hypoxic respiratory failure in severe immunosuppressive patients. It is reported that high-flow oxygen therapy is a more comfortable oxygen therapy method compared with standard oxygen therapy.

Yang Fei's previous oxygen therapy was all ordinary oxygen therapy, so Su Yang decided to immediately carry out high-flow nasal catheter oxygen therapy treatment for the patients.

However, Su Yang did not intend to only provide hyperbaric oxygen therapy to the patient. After careful consideration, he decided to give the patient atomized inhalation prostacyclin (iap) treatment during the oxygen therapy.

ino is used in patients with pulmonary hypertension and acute respiratory distress syndrome (ards), but it is costly.

Researchers reported that both Ino and IAP have been shown to reduce pulmonary vascular pressure and improve oxygenation in patients with ards, but controlled trials have not proved the effectiveness of Ino in the treatment of adult ards.

"There is no reason to use ino for adult patients, one is because of the cost issue, and the other is because we have an alternative that is equally effective, but cheaper, potentially less toxic, which is easier to use and does not require complex, expensive, specialized delivery tools, unlike ino," said Dr. Lowson, of the University of Virginia at Charlottesville.

And unlike ino, there are no known toxic metabolites that may lead to lung toxicity.

Dr. Lowson said that Ino has conducted four clinical trials on ards patients. "One study showed no benefit, and three other trials showed a trend of increased mortality in patients with ino treatment. Large clinical studies are needed to compare the therapeutic effects of placebo and prostacyclin on ards patients."

Therefore, Su Yang decided to use prostacyclin (iap), i.e. prostalpin.

This kind of treatment is the first time in the main hospital, so Su Yang did not dare to be careless. He first performed several experimental treatments in the system space until he was sure that the patient would not have any problems. He was relieved.

However, such treatments do not treat the symptoms and root causes, and do not solve the patient's fundamental problems. Hypoxemia will still occur later, and may even bring the patient a risk of death.

Because Su Yang had at least three accidents during the experimental treatment, everything was fine when the patient was treated, but after the treatment was discharged from the hospital, he suddenly became ill and his condition was extremely critical. Once he was even sent to the intensive care unit.

Therefore, Su Yang must find the fundamental problem of the patient and then eliminate future problems forever. Otherwise, no matter how good the treatment is, it will treat the symptoms but not the root cause!

Su Yang performed an angiography on the patient.

However, strangely, the patient did not find any abnormalities after an angiography examination.

It's strange!

How come there is no problem?

Common causes of hypoxemia are:

The partial pressure of inhaled oxygen is too low;

Inadequate alveolar ventilation;

diffusion dysfunction;

Alveolar ventilation/blood flow ratio imbalance;

Divide right to left.

Su Yang investigated one reason and one reason after another, but found no problems.

Strange, what's the problem?

Su Yang thought about it for a long time but couldn't find the answer.

After pondering for a while, he decided to do another experiment, which is to not treat it for the time being, and only conduct symptomatic treatment. That is, the patient is given oxygen treatment when he develops hypoxemia, but no other treatment is done. Then let the subject develop naturally. When the subject explodes again, and it is a big problem, it directly leads to death, a detailed autopsy on the subject will be conducted, and the crux of the problem will be found through the body.

Su Yang's idea is very correct. After systematic training, the experimental subject ages rapidly in the system space. After about a year, the experimental subject becomes ill again, and the condition is dangerous and he dies directly.

He performed an autopsy on the patient and soon found the problem.

In order to verify his guess, he conducted a second experimental subject cultivation, and then performed an angiography examination on the experimental subject on the eve of his death.

Multiprobe CT angiography (TTCE) examination revealed that a huge proximal pulmonary arteriovenous fistula was seen in the patient's thoracic cavity.

Transthoracic echocardiography showed that a large number of microvesicles entered the left heart in the early stage (the third cardiac cycle), and there was no evidence of pulmonary hypertension or enlargement of the ventricular cavity.

After careful study by Su Yang, it was diagnosed that there was a lateral-lateral fistula between the lateral basal segment of the pulmonary artery (diameter 6    mm) and the aneurysm sac, and blood flowed into the enlarged pulmonary vein (diameter 8    mm) and the distal pulmonary artery (diameter 6    mm).

There was no persistent murmur on the left posterior chest wall of the patient.

Obviously, this is a severe hypoxemia after many years of gunshot wounds. The gunshot wound causes a chest penetration injury, and the penetration injury causes a traumatic pulmonary arteriovenous fistula.

However, at this time, the pulmonary arteriovenous fistula is still relatively small and is not easy to detect, so the cause of the patient's hypoxemia cannot be found by doctors from any hospital.

It is easy to see when you grow up, but at that time, the patient's condition was more dangerous!

Although chest penetration trauma is a common acute disease, traumatic pulmonary arteriovenous fistula (pavf) caused by this disease is very rare.

dairywala et al. have reported 1 traumatic pavf and 4 related literature. The clinical manifestations can be acute onset or many years after trauma.

Currently, the diagnosis of congenital and acquired PavF depends on the patient's medical history, physical examination, laboratory examination, chest radiation examination, multi-probe CT scan and TTCE3.

Early symptoms of the patient are related to proximal arteriovenous fistula and large shunts. Pulmonary angiography can be used to treat this disease. Congenital PavF is usually associated with capillary end-end abnormalities, especially in patients with rendu-osler-weber disease.

Traumatic pavf (especially proximal lesions) belongs to lateral-lateral shunt and is secondary to damage to the pulmonary artery and venous walls.

The treatment method for pavf is to close the artery that supplies blood to the aneurysm sac.

The patient has a reverse shunt of the systemic circulation-pulmonary circulation from the tracheal artery in his body, so it is difficult to only close the pulmonary blood supply artery, but not the pulmonary drainage artery (permanent pulmonary artery after the aneurysm sac).

But the pulmonary artery was successfully closed through 2 closures.

Of course, there is another treatment plan, which is different from intravascular closure, that is, the lower lobe of the left lung is removed without preserving the lung parenchyma.

However, after systematic experimental treatment tests, the first treatment plan is still more beneficial to patients, so Su Yang finally chose the first treatment plan.

Therefore, Su Yang chose the following treatment methods:

First, the drainage artery is closed through a closure with a diameter of 10    mm, and then the blood supply artery is closed through a closure with a diameter of 12    mm.

After the operation, the patient increased pao2 to 75    mmhg under normal breathing, and 6% of physiological shunt remained.

After 3 months of follow-up via multi-probe ct angiography, aneurysm sac and drainage vein were reduced.

One year later, TTCE showed that the signs of microbubble flow from right to left disappeared, and the patient's o2 saturation was 96% during normal breathing.

The patient finally recovered completely and had a good living condition.
Chapter completed!