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Artificial ventilation of the lungs
Medical expert of the article
Traditional artificial ventilation of the lungs
Controlled ventilation is carried out when the patient does not have independent breathing or is undesirable in this clinical situation.
In newborns, controlled and auxiliary artificial lung ventilation is carried out exclusively by pressure-controlled ventilators that switch over time, with a continuous flow of gas in the respiratory circuit. These devices can easily compensate for gas leaks in the breathing circuit, which usually occur in ventilation in young children. High gas flow rates in the contour of such respirators ensure the rapid arrival of the necessary volumes of gas when spontaneous breaths occur, which minimizes the work of breathing. In addition, the slowing inspiratory flow provides a better distribution of gas in the lungs, especially when there are areas with non-uniform mechanical properties.
Indications for mechanical ventilation
Indications for mechanical ventilation should be determined individually for each newborn. In this case, the severity of the condition and the course of the disease, the gestational and postnatal age of the child, the clinical manifestations of respiratory and cardiovascular insufficiency, radiographic data, CBS and the gas composition of the blood should be taken into account.
The main clinical indications for IVL in newborns:
- apnea with bradycardia and cyanosis,
- refractory hypoxemia,
- excessive work of breathing,
- acute cardiovascular insufficiency.
Additional criteria can serve as indicators of CBS and gas composition of blood:
- paO2 <50 mm. Gt; Art. At FiO2> 0.6,
- paO2 <50 mm. Hg Art. At CPAP> 8 cm of water,
- paCO2> 60 mm. Gt; Art. And pH <7.25
When analyzing laboratory data, both absolute values and dynamics of indicators are taken into account. The gas composition of the blood can stay for a certain time within the permissible limits due to the voltage of the compensatory mechanisms. Given that the functional reserve of respiratory and cardiovascular systems in newborn children is much lower than that of adults, it is necessary to decide whether to switch to ventilation before the signs of decompensation appear.
The purpose of artificial ventilation is to maintain pO2 at a level of at least 55-70 mm. Gt; Art. (СО2 - 90-95%), раСО2 - 35-50 mm. Gt; The pH is 7.25-7.4.
Modes of ventilation
- FiO2 - 0.6-0.8,
- frequency of ventilation (VR) - 40-60 in 1 min,
- duration of inspiration (Tsh) - 0,3-0,35 s,
- PIP - 16-18 cm of water. Art.
- PEEP - 4-5 cm of water. Art.
Having connected the child to the respirator, first of all pay attention to the excursion of the thorax. If it is insufficient, then after every few breaths increase PIP by 1-2 cm of water until it becomes satisfactory and VT does not reach 6-8 ml / kg.
The child is provided with a comfortable state, eliminating external stimuli (stop manipulation, turn off bright light, maintain a neutral temperature regime).
Assign tranquilizers and / or narcotic analgesics to midazolam - a saturation dose of 150 μg / kg, supporting 50-200 μg / (kghh), diazepam - a saturation dose of 0.5 mg / kg, trimiperidine - a saturation dose of 0.5 mg / kg, supporting a dose of 20-80 μg / (kghh), fentanyl - 1-5 μ / (kghh).
After 10-15 minutes after the onset of ventilation, it is necessary to check the gas composition of the blood and correct the ventilation parameters. Hypoxemia is eliminated by increasing mean airway pressure, and hypoventilation by increasing the respiratory volume.
The "allowable hypercapnia" mode
The regime of "allowable hypercapnia" is established if the risk of development or progression of baro-and volumetrics is high.
Indicative parameters of gas exchange:
- p CO2 is 45-60 mm Hg,
- pH> 7.2,
- VT-3-5 ml / kg,
- SpO2 - 86-90 mm Hg
Hypercapnia is contraindicated in intraventricular hemorrhages, cardiovascular instability and pulmonary hypertension.
Ventilation from ventilator begins with an improvement in the state of gas exchange and stabilization of hemodynamics.
Gradually reduce FiO2 <0.4, PIP <20 cm of water, PEEP> 5 cm of water, VR <15 per min. After this, the child is extubated and transferred to CPAP through the nasal cannula.
The use of trigger modes (B1MU, A / C, RBU) in the period of weaning from the fan makes it possible to obtain a number of advantages, primarily associated with a decrease in the frequency of baroque and volumetrics.
High-frequency oscillatory artificial ventilation of the lungs
High-frequency oscillatory ventilation (IVF) is characterized by a frequency (300-900 in 1 min), a low respiratory volume within the dead space, and the presence of active inspiration and expiration. Gas exchange at VCHO IVL is carried out both by direct alveolar ventilation, and as a result of dispersion and molecular diffusion.
Oscillatory artificial ventilation of the lungs constantly maintains lungs in a straightened state, which not only stabilizes the functional residual capacity of the lungs, but also mobilizes hypoventilated alveoli. At the same time, ventilation efficiency is practically independent of regional differences in the mechanical properties of the respiratory system and is equal to high and low extensibility. In addition, at high frequencies, the air leakage from the lungs decreases, since the inertia of the fistula is always higher than that of the respiratory tract.
The most frequent indications for IVF of IVL in newborns:
- unacceptably rigid parameters of traditional mechanical ventilation (MAP> 8-10 cm H2O),
- presence of air leakage syndromes from the lungs (pneumothorax, interstitial emphysema).
Parameters of VCHO ventilation
- MAP (average airway pressure) directly affects the level of oxygenation. It is established on 2-5 sm of water of ст ст above, than at traditional IVL.
- BIB (oscillation frequency) is usually set in the range of 8-12 Hz. Reducing the frequency of ventilation leads to an increase in the respiratory volume and improves the elimination of carbon dioxide.
- AP (amplitude of oscillations) is usually selected in such a way that the patient is determined by visible vibration of the chest. The higher the amplitude, the greater the tidal volume.
- BIO2 (fractional concentration of oxygen). It is the same as for traditional ventilation.
Correction of parameters VCHO ALV should be performed in accordance with the parameters of the gas composition of the blood:
- at a hypoxemia (p02 <50 mm Hg),
- to increase MAP by 1-2 cm of water, up to 25 cm of water. Art.
- increase B102 by 10%,
- apply the technique of lung dilatation,
- with hyperoxemia (Pa02> 90 mm Hg),
- decrease the O2 to 0.4-0.3,
- with hypocapnia (paco2 <35 mm Hg),
- reduce the AP by 10-20%,
- increase the frequency (by 1-2 Hz),
- with hypercapnia (paC02> 60 mm Hg),
- increase the AP by 10-20%,
- To reduce the oscillation frequency (by 1-2 Hz),
- increase MAP.
Termination of VHF artificial ventilation
When the patient's condition improves gradually (in increments of 0.05-0.1), reduce SO2, bringing it to 0.4-0.3. Also, gradually (in increments of 1-2 cm H2O), MAP is reduced to the level of 9-7 cm of water. Art. After this, the child is transferred either to one of the auxiliary modes of normal ventilation, or to CPAP through nasal cannulas.