Indications: 1. Severe ventilation II. Severe ventilation disorder 3. Neuromuscular paralysis. After heart surgery. Increased intracranial pressure. When using large doses of sedatives, neonatal tetanus needs respiratory support. Asphyxia, cardiopulmonary resuscitation. Breathing stops or will stop for any reason.
Second, contraindications: there are no absolute contraindications. Pulmonary bullae, pneumothorax, hypovolemic shock, myocardial infarction and other diseases should be used to reduce the ventilation pressure and increase the frequency.
Three, the basic types and performance of ventilator:
1. Constant volume ventilator: switch from inspiration to expiration according to the preset tidal volume.
2. Constant pressure ventilator: switch from inspiration to expiration according to the preset peak pressure. (Unlike pressure limiting, pressure limiting refers to continuing to supply gas without switching after the airway pressure reaches a certain value. )
3. Timing ventilator: The conversion from inspiration to expiration is determined by the time parameter (inspiration time). Since 1980s, timed, pressure-limited and constant-current ventilators have appeared. This kind of ventilator retains the characteristics of timing and constant volume that can still ensure ventilation when airway resistance increases and lung compliance decreases, and also has the advantage that it is not easy to cause barotrauma because of limited peak pressure. The inspiratory time, expiratory time, inspiratory proportion, inspiratory platform size and oxygen concentration can all be adjusted, and at the same time, it can provide ventilation modes such as IMV (Intermittent Mandatory Ventilation) and CPAP (Continuous Positive Airway Pressure Ventilation), which is the most suitable ventilation mode for infants at present.
Four, commonly used mechanical ventilation methods
1. intermittent positive pressure ventilation (IPPV): the most basic ventilation method. When inhaling, positive pressure is generated, which pushes the gas into the lungs and exhales it according to the body's own pressure.
2. Exhale platform: also called positive end-expiratory pressure breathing (EIppb). After inhalation, before exhalation, the expiratory valve is closed for a period of time, generally not exceeding 5% of the respiratory cycle, which can reduce VD/VT (dead space/tidal volume).
3. Positive End-expiratory Pressure Ventilation (PEEP): Under the premise of intermittent positive pressure ventilation, maintaining a certain pressure in the end-expiratory airway plays an important role in the treatment of respiratory distress syndrome, non-cardiogenic pulmonary edema and pulmonary hemorrhage.
4. Intermittent forced ventilation (IMV) and synchronous intermittent forced ventilation (SIMV): they belong to the auxiliary ventilation mode, and there is continuous airflow in the ventilator pipeline. (spontaneous breathing) give positive pressure ventilation after several spontaneous breaths to ensure the ventilation volume per minute. The respiratory rate of IMV is generally less than 10 beats/min in adults and less than1/2 ~110 in children.
5. Expiratory delay, also known as expiratory delay: it is mainly used for early airway collapse and chronic obstructive pulmonary disease, such as asthma, and should not be used for too long.
6. Take a deep breath or sigh.
7. Pressure support: On the basis of spontaneous breathing, provide certain pressure support, so that the pressure reaches the predetermined pressure peak every time you breathe.
8. Continuous positive airway pressure ventilation (CPAP): In addition to adjusting the CPAP knob, it is necessary to ensure sufficient flow, and the flow should be increased by 3-4 times. The normal value of CPAP is generally 4~ 12cm water column, and it can reach 15 cm water column under special circumstances. (Exhale pressure 4 cm water column).
Verb (abbreviation for verb) Connection between ventilator and human body:
In case of emergency or it is estimated that the indwelling time of intubation will not be too long, newborns and premature infants are generally intubated orally. In other cases, you can choose nasal intubation or tracheotomy.
6. Adjustment of working parameters of ventilator: Four parameters: tidal volume, pressure, flow and time (including breathing frequency and inspiratory-expiratory ratio).
1. tidal volume: tidal volume must be greater than human physiological tidal volume, 6~ 10 ml/kg, while the tidal volume of ventilator can reach/kloc-0 ~15ml/kg, which is often 1~2 times of physiological tidal volume. It should be further adjusted according to chest fluctuation, auscultation of both lungs, reference pressure gauge and blood gas analysis.
2. Respiratory frequency: close to the physiological respiratory frequency. 40~50 times per minute for newborns, 30~40 times per minute for infants, 20~30 times per minute for older children and 0/6 ~ 20 times per minute for adults. Tidal volume * respiratory rate = ventilation per minute
3. Breathing-breathing ratio: generally, it is 1: 1.5 ~ 2, and the expiratory time can be adjusted to 1: 3 or longer for obstructive ventilation disorder and 1 for restrictive ventilation disorder.
4. Pressure: generally refers to the peak airway pressure (PIP). When the lung compliance is normal, the peak inspiratory pressure is generally 10~20 cm water column, and the lung lesions are mild: 20~25 cm water column; Moderate: 25 ~ 30mm water column; Severity: more than 30 cm water column, RDS and pulmonary hemorrhage can reach more than 60 cm water column. But generally below 30, the newborn is 5 cm lower than the above pressure.
5. it is physiological to give children 2~3 cm water column with IPPV. When severe ventilation disorders (RDS, pulmonary edema, pulmonary hemorrhage) occur, PEEP should be increased, which is generally 4~ 10 cm water column, or even more than 20 cm water column in severe cases. When the oxygen concentration exceeds 60%(FiO2 is greater than 0.6), if the arterial oxygen partial pressure is still below 80mm Hg, PEEP should be mainly increased until the arterial oxygen partial pressure exceeds 80mm Hg. Every time PEEP increases or decreases 1~2 mm water column, it will have a great impact on blood oxygen, which will appear in a few minutes. PEEP should be decreased gradually, and the changes of blood oxygen should be monitored. PEEP value can be read from the end-expiratory position of the pressure gauge pointer. (It is better to have a special monitor)
6. Flow rate: at least twice the ventilation rate per minute, generally 4 ~ 10L/min.
7. Further adjustment according to blood gas analysis: firstly, check whether the respiratory tract is unobstructed, the position of tracheal catheter, the air intake of both lungs are good, whether the ventilator delivers air normally and whether there is air leakage.
Adjustment method:
When 1.Pao2 is too low: (1) increase the oxygen concentration (2) increase the PEEP value (3) If the ventilation is insufficient, increase the ventilation per minute, prolong the inhalation time and stay at the end of inhalation.
2. When 2.PAO _ 2 is too high: (1) decrease the oxygen concentration; (2) gradually decrease the PEEP value.
3. When 3.PaCO _ 2 is too high: (1) increase the respiratory frequency; (2) Increasing tidal volume: constant volume type can be directly adjusted, constant pressure type can increase preset pressure, and timing type can increase flow and increase pressure limit.
4. When 4.PaCO 2 is too low: (1) slow down the breathing frequency. Exhale and inhale time can be extended at the same time, but it should be extended mainly, otherwise it will have the opposite effect. If necessary, you can change it to IMV mode. (2) Reduce tidal volume: constant volume type can be directly adjusted, constant pressure type can reduce preset pressure, and timing type can reduce flow and pressure restrictions.
8. Humidification: heating and humidification: the best effect, the water temperature in the box is 50~70 degrees Celsius, the standard pipe length is 1.25m, the outlet gas temperature is 30~35 degrees Celsius, and the humidity is 98~99%. The wetting liquid can only be distilled water. Atomizer: low temperature and great irritation. It is more difficult for patients to accept. Direct intratracheal instillation: especially when there is sputum scab obstruction in the airway, repeated back slapping and sputum aspiration after instillation can often alleviate poor ventilation. Specific methods: Adults drop 2 ml of 0.45~0.9 physiological saline every 20~40 minutes, or at a rate of 4~6 drops/minute, with a total amount of more than 200ml/ day. Children drop 3~ 10 drops every 20~30 minutes, with thin airway secretions, smooth sputum suction and no sputum scab. Artificial nose. A little.
9. Oxygen concentration (FiO2): The oxygen concentration of general machines can be adjusted between 2 1 and 100%. Hypoxemia must be corrected to prevent oxygen poisoning. Generally should not exceed 0.5~0.6. If it exceeds 0.6, the time should be within 24 hours. Objective: To minimize the oxygen concentration in arterial blood when pao 2 > 60 mmhg(8.0 kpa). If cyanosis cannot be relieved after oxygen supply, PEEP can be added. Oxygen of 1.0 can be used during resuscitation, regardless of oxygen poisoning.
X set alarm range: upper and lower limit alarm of airway pressure (generally 30% of the set value), air source pressure alarm and other alarms.
XI。 Unexpected problems: a resuscitator or other simple artificial airbag should be equipped next to the ventilator, and the joint between the airbag and the tracheal catheter should also be prepared. Pay attention to prevent tube detachment, tube blockage, ventilator failure, gas source and power supply failure.
Common complications: pressure injury, circulatory disorder, respiratory infection, atelectasis, laryngotracheal injury.
13. Ventilator evacuation: gradually reduce oxygen concentration, PEEP to 3~4 cm water column, change IPPV to IMV (or SIMV) or pressure support, gradually reduce IMV or support pressure, and finally transition to CPAP or completely evacuate the ventilator. The whole process requires close observation of respiration and blood gas analysis. Indications of extubation: spontaneous breathing, strong cough, good swallowing function, basically normal blood gas analysis results, no laryngeal obstruction, extubation can be considered. Tracheal intubation can be pulled out at one time, and tracheostomy can be pulled out gradually by changing thin tube, half blocking tube and full blocking tube.
Indication of ventilator use
The physiological effects of mechanical ventilation, namely (1) improving ventilation (2) improving ventilation (3) reducing respiratory power consumption, determine that mechanical ventilation can be used to improve the following pathophysiological states.
Ventilation pump failure: decreased impulse transmission and conduction disorder in respiratory center; Mechanical dysfunction of thoracic cavity; Respiratory muscle fatigue.
◎ Ventilation dysfunction: decreased functional residual volume; V/Q ratio imbalance; Increased pulmonary shunt; Diffuse disorder.
◎ To strengthen airway management: keep airway unobstructed to prevent suffocation; When using certain drugs that inhibit breathing. The following conditions can be used to judge whether to carry out mechanical ventilation:
◎ General treatment of respiratory failure is ineffective;
◎ Respiratory frequency is greater than 35 ~ 40 beats/min or less than 6 ~ 8 beats/min;
◎ Abnormal breathing rhythm or weak or disappearing spontaneous breathing;
◎ Respiratory failure with severe disturbance of consciousness;
◎ Severe pulmonary edema;
◎ PaO2 is less than 50mmHg, especially after oxygen inhalation;
PaCO 2 increased progressively and pH decreased dynamically.
Specific indications:
◎ Lung diseases: COPD, ARDS, bronchial asthma, interstitial lung disease, pneumonia, pulmonary embolism, etc.
Central respiratory failure caused by brain inflammation, trauma, tumor, cerebrovascular accident and drug poisoning;
◎ Severe chest disease or respiratory myasthenia;
Cardiopulmonary resuscitation.
Contraindications and relative contraindications:
◎ Pneumothorax and mediastinal emphysema do not drain;
◎ Pulmonary bullae;
◎ Hypovolemic shock supplements blood volume;
◎ Severe pulmonary hemorrhage;
◎ Ischemic heart disease and congestive heart failure.
In addition to the above factors, we should also pay attention to:
◎ Dynamic observation of disease changes. If routine treatment can't stop the progressive development of the disease, get on the computer as soon as possible;
When fatal ventilation oxygenation disorder occurs, there is no absolute contraindication for mechanical ventilation;
◎ Possibility of aircraft exiting;
Social and economic factors.