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Mechanical ventilation


1. When is mechanical ventilation indicated?
Mechanical ventilation is indicated for: (1) animals that are unable to maintain Ra02> 50 mmHg. Art., despite breathing oxygen (through a mask, nasal catheters
or in an oxygen tent); (2) animals unable to maintain PaCO2 <50 mm Hg. Art., despite the end of the action of respiratory depressants or thoracocentesis (if clinically indicated). This is called the “50/50” rule. Other indications for mechanical ventilation include: 1) clinical deterioration, which threatens the development of respiratory failure; 2) cardiac arrest and breathing.
2. What devices are used for mechanical ventilation?
For artificial ventilation, both simple devices - Ambu bag attached to the endotracheal tube, and complex - computer respiratory centers for long-term respiratory support are used. In general, the latter provide better control over ventilation parameters (oxygen content, humidity, tidal volume, inspiratory pressure) than a manually controlled respirator.
3. What types of ventilation are commonly used in veterinary medicine?
For volume-limited ventilation, the respirator supplies a certain amount
air into the patient’s airways regardless of the pressure required
for this. With a sudden increase in airway pressure that occurs:
as a rule, during obstruction, an alarm is triggered. During ventilation with pressure limitation, the respirator delivers air up to a pre-set pressure value for inspiration, regardless of volume. Due to the tendency to a decrease in tidal volume due to obstruction of the airways or changes in the pulmonary complex, the PaCO2 value, as well as the tidal volume (by spirometry), need to be monitored more often. According to some reports, the use of pressure-limited ventilation is preferable in small animals (<4 kg).
4. What are the most commonly used ventilation modes? Auxiliary control mode. The breathing apparatus is set for a certain number of breaths in 1 min. The respirator takes a breath when the patient generates negative inspiratory pressure; if the patient does not breathe, the device delivers the gas mixture at the set frequency. An animal with frequent breathing (e.g. shortness of breath) may develop hyperventilation. In this case, use a different ventilation mode.
With synchronized intermittent forced ventilation, the breathing apparatus produces a predetermined number of breaths in 1 min. Respiration can be initiated by negative inspiratory pressure, but if the patient's respiratory rate exceeds that in the device, the latter does not support breathing. This mode is used when the animal is disconnected from the breathing apparatus, since the number of breaths set by the respirator can be slowly reduced.
For spontaneous ventilation, many types of respirators are used; in this case, the breathing apparatus works as an anesthetic device. In veterinary medicine, this ventilation mode is rarely used, but they resort to it to supply the animal with the established oxygen concentration or during constant monitoring of the patient after it is disconnected from mechanical ventilation (IVL).
5. When is intubation recommended for an animal, and when is a tracheostomy recommended?
The choice of method for ensuring airway patency depends both on the underlying disease and on which method the doctor prefers. The advantages of oral methods of providing access to the respiratory tract include simplicity, speed of their implementation and minor tissue injury. The advantages of a tracheostomy are less need for additional funds and less immobilization, as well as maintaining the ability of the animal to ingest food and water through the mouth; disadvantages - surgical intervention in an animal with weakened immunity and the possible need for more careful observation than with general anesthesia (due to the risk of occlusion or displacement of the tracheal tube).
In general, it is advisable for a patient who has to be on mechanical ventilation for more than 36-48 hours to consider performing a tracheotomy.
6. What drug regimens are designed for sedation and anesthesia?
The ideal drug causes minimal inhibition of the cardiovascular system, is easily titrated and economical. Obviously, such a drug does not exist. Pentobarbital (2-16 mg / kg, intravenously every 4-6 hours) was successfully used in many dogs. The principal advantage of pentobarbital is its duration and relatively low cost; disadvantages - a long recovery phase and a lack of withdrawal drugs. Oxymorphone (0.05-0.1 mg / kg, intravenously as needed) is often prescribed in combination with diazepam (0.250.5 mg / kg, intravenously as needed). Opiates usually do not affect the cardiovascular system, but are expensive and require frequent administration. Also use infusion at a constant speed (before the onset of effect) of fentanyl or propofol. Occasionally, muscle relaxants, in particular atracurium (0.2 mg / kg, intravenously), are prescribed to facilitate mechanical ventilation. It is very important to introduce muscle relaxants in combination with good painkillers.
7. What is PEEP?
Positive end-expiratory pressure (PEEP) improves blood oxygenation in patients with hypoxia that persists despite a high concentration of respirable oxygen and normal or decreased PaC02. PEEP prevents full expiration and thereby increases the functional residual capacity, prevents the early closure of small airways and increases the size and number of functioning alveoli, improving the ventilation-perfusion ratio. PEEP also reduces venous return to the heart and cardiac output.
8. What problems are associated with mechanical ventilation?
Mechanical ventilation is not without risk. The main clinical problems are barotrauma and infection. Barotrauma is the result of excessive positive pressure in certain areas of the lungs, which causes their rupture and the formation of pneumothorax (or pneumomediastinum). One of the most common causes of a drop in blood oxygen saturation in a previously stable patient on mechanical ventilation is the development of severe pneumothorax. Pneumothorax is possible in animals with severe lung disease, but its occurrence should not be considered as a significant deterioration in the condition of the animal.
Infection is another serious problem with mechanical ventilation. The infection often spreads to the lungs of the infected upper respiratory tract and oropharynx, as the physiological defense mechanisms of the upper respiratory tract are shunted. In addition, patients on mechanical ventilation have a state of immunodeficiency, and they are also immobilized, which also increases the risk of infection. It is necessary to make every effort to maintain cleanliness and sterility and conduct regular microbiological inoculations (every 24-48 hours). Their results, taking into account the clinical symptoms, determine antibiotic therapy.
Possible consequences of mechanical ventilation include decreased venous return, oxygen intoxication, damage or irritation of the upper respiratory tract, and impaired musculoskeletal function associated with the patient’s prolonged lying position.
9. What is the prognosis for animals on mechanical ventilation?
The prognosis for ventilated animals depends on the underlying disease. So, in a 15-year-old dog with recurrent aspiration pneumonia due to megaesophagus with rapidly progressive respiratory failure, the prognosis is difficult, and in a young dog with a traumatic violation of the chest frame and lung contusion, the prognosis is favorable. According to the author’s experience, the aim of treating such animals should be to ensure survival rates above 30-40%, followed by a good quality of life.
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Mechanical ventilation

  1. Controlled mechanical ventilation (mechanical ventilation, CMV)
    With controlled mechanical ventilation, inhalation is performed automatically and independently of the possibly preserved spontaneous breathing, i.e. There is no synchronization. When breathing in, the respirator does all the work of breathing and adjusts the duration and size of each breath. If PDKV = 0, then the type of ventilation is called IPPV - ventilation with intermittent positive pressure. If
  2. Fundamental principles of mechanical ventilation for newborns and infants
    With mechanical ventilation of a child, it is necessary to take into account the special physiological characteristics of children, especially newborns. When setting ventilation parameters in constant-volume respirators, adjustable in time, the tidal volume (TO> = 40 ml) is set directly. In devices of constant flow, adjustable in time and with limited pressure on the inspiration,
  3. General indications for mechanical ventilation in intensive care
    Despite the numerous works devoted to the indications for mechanical ventilation during intensive care, and the long-term study of this issue, it cannot be recognized as finally resolved. This is a matter of paramount importance, since its effectiveness depends on the timely start of respiratory support. One of the most common mistakes in the treatment of patients with respiratory failure is a late start.
  4. Heating, ventilation, air conditioning. Types of ventilation. Basic requirements for operation
    Heating, ventilation and air conditioning systems are designed to ensure normalized meteorological conditions and clean air in the workplace. According to the method of organizing air exchange, ventilation can be general exchange, local and combined. General ventilation, used in cases where harmful substances are released in small quantities and evenly throughout
  5. Ventilation of the lungs with two phases of positive pressure of the respiratory tract (two-phase ventilation of the lungs)
    A peculiar method of lung ventilation, which can be used both in mechanical ventilation and in mechanical ventilation, is ventilation with two phases of positive airway pressure or two-phase ventilation of the lungs - Biphasic positive airway pressure - BIPAP; on some respirators, this method is referred to as "BiVent" or "BiLevel". At its core, it is controlled ventilation.
  6. Types of ventilation and types of ventilation disorders
    The nature of lung ventilation can vary due to a variety of reasons. Respiration is enhanced during work, changes in the metabolic needs of the body and in pathological conditions. You can optionally enhance breathing. Reduced ventilation can also be either arbitrary or occur as a result of regulatory or pathological factors. Developed physiologically clear
  7. Mechanical asphyxia
    Hypoxia - oxygen starvation of organs and tissues, until the complete cessation of oxygen supply to the body. Asphyxia is the state of the body when, along with a lack of oxygen, carbon dioxide accumulates in it. Mechanical asphyxia arises from the action of an external mechanical factor. According to the pace of development, hypoxia is divided into: acute, developing and leading to
  8. Mechanical processing of materials
    The specific emissions of harmful substances into the atmosphere from the main types of equipment for the mechanical processing of materials should be taken according to the methodology: “Methodology for calculating the emissions (emissions) of pollutants into the atmosphere during the mechanical processing of metals (based on specific indicators), Research Institute Atmosphere,“ Integral ”, C- St. Petersburg, 1997. This section shows the allocation of equipment,
  9. Mechanical processing of materials
    1. In most cases, calculation methods are used to determine the pollutant emissions from technological equipment for machining materials (metals, wood, plastics, fiberglass, etc.) [28]. These methods allow you to determine the mass of harmful substances released into the atmosphere. When process plants are equipped with local suction, the amount of pollutants
  10. MECHANICAL DAMAGE TO TISSUES
    The consequences of mechanical effects on animals can be wounds, bruises, scratches, abrasions on the skin, bruises, lymphatic extravasation, stretching and tearing of tissues, ruptures of internal organs, abdominal hemorrhages, bone fractures, paralysis, paresis, and shell shock. In animals intended for slaughter, mechanical damages received on farms that occur upon delivery to places are detected
  11. MECHANICAL DAMAGE TO PREGNANT WOMEN
    Injuries during different periods of pregnancy complicate the obstetric situation and can pose a direct threat to the life of the pregnant woman herself. According to the generally accepted classification, mechanical damage is distinguished by severity and localization. Mild injuries in the I and II trimester of pregnancy (up to 28 weeks), as a rule, do not affect its course, do not require obstetric and gynecological intervention, and more often
  12. Mechanical methods
    Mechanical condoms include a male condom, female caps, and diaphragms. Sometimes this method is called the barrier. Its essence is to create an obstacle for sperm to enter the uterine cavity and, therefore, to fertilize the egg cell. • Condoms The use of condoms (condoms) is an effective method of male contraception. Right them
  13. Mechanical methods
    For many centuries, a variety of mechanical means have been used to prevent unwanted pregnancies. Male condom During the existence of the Roman Empire, condoms made from the lamb's cecum, goat's bladder, etc., were widely used. The prototype of the male condom was proposed by Fallopius in the XVI century. canvas bag
  14. Mechanical surface preparation of parts
    To remove molding, core mixture and scale from casting surfaces, shot blasting and shot blasting, tumbling are used. The main harmful substance released into the atmosphere is inorganic dust. Calculations of emissions of harmful substances should be made according to the formulas (4.5). Specific emissions of harmful substances into the atmosphere from the main types of equipment during mechanical
  15. Mechanical obstruction
    Mechanical obstruction (impaired patency) of the upper gastrointestinal tract can cause both acute and chronic nausea and vomiting, which depends on the causes of obstruction, which are divided into three categories: disorders in the gastrointestinal cavity, changes in the intestinal wall and disorders from the outside of the gastrointestinal tract. Disorders such as invagination, ulcers of the pyloric stomach, inversion of the intestine or infringement of a hernia lead to the appearance of
  16. Mechanical and physical properties of the soil
    Soil temperature - determines the temperature of the surface layer of the atmosphere, as well as the thermal regime of the premises of basements and first floors of buildings. At a depth of 1 m, the soil no longer has daily temperature fluctuations. At a depth of 7-8 m, the lowest temperature remains in May, the highest - in December. It is of great sanitary importance for storing food in the basement, where in the summer
  17. Hemolytic anemia associated with mechanical damage to the erythrocyte membrane
    The causes of hemolytic anemia associated with mechanical damage to the erythrocyte membrane are presented in table. 42. Hemolytic anemia associated with mechanical damage to the erythrocyte membrane occurs in patients with aortic valve prostheses due to intravascular destruction of red blood cells. Hemolysis is caused by the prosthesis device (mechanical valves) or its dysfunction
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