Description of the problem:
My patient needs oxygen 24 hours a day, at night with a non-invasive ventilator inhalation to connect the nasal mask inhalation of oxygen, but it feels uncomfortable, as if the airflow is a little too big? Is it possible to expel carbon dioxide from the lungs with nasal mask oxygen?
Ans:
As a therapeutic, first-aid, and resuscitation device, today's ventilators have more and more functions
, more and more perfect performance, and reliability is constantly improving, and most
of the ventilators are computerized, with complete safety
alarms, and are easy to operate.
A
, the classification of the ventilator
fI percussion bed according to the ventilator work from the inspiratory phase to the expiratory phase
change the switching mode of the ventilator is divided into the following categories:
1. Fixed-pressure type (pressure switching type): this type of ventilator pressure
switching mode that is, the management of ventilation through the airway pressure. The pressure is predetermined,
respiratory frequency for air supply, when the air pressure in the lungs reaches a predetermined value after the termination of inhalation
to expiration, the pressure in the lungs down to the set value to send air again. Factors other than
pressure (e.g., volume, inspiratory time, inspiratory flow rate, etc.) are
variable, i.e., airway pressure is an independent parameter, whereas ventilation volume and
flow rate are subordinate to the change, and therefore are related to the patient's lung compliance and airway resistance
force, and when the lung compliance and airway resistance are changed, the tidal volume
must change as well. The advantage is that the pressure is controllable, which helps to judge the efficacy of the ventilator; however, the main disadvantage is that the tidal volume cannot be maintained at a stable
level, which is highly demanding for the doctor's operation.
2. Fixed-volume type (volume conversion type): its basic working process is to preset
tidal volume, peak flow value of the patient ventilation, when the lung inflation expansion
expansion, volume, flow rate to reach a predetermined value immediately stop the supply of air from inhalation
to expiration. As the pressure of the airway decreases, the thorax and lungs elastically retract,
and the gas in the alveoli is expelled from the body. When airflow resistance and compliance change
, the inspiratory pressure changes accordingly
in order to ensure a stable tidal volume. The advantage is that it can keep the ventilation volume stable, easy to adjust, and suitable for
any disease long-term artificial ventilation; the disadvantage is that the pressure is not
stable during the ventilation process, easy to pneumothorax and hypotension.
3. Timing type (time switching type): the basic working process for the predetermined
respiratory cycle, according to the set tidal volume of inhalation, exhalation cut
replacement. It has the characteristics of both fixed-pressure and fixed-volume type, but it has a certain influence on lung compliance and airway
resistance, and when the compliance and airway resistance change
, the inspiratory pressure, volume, and flow rate have to change. This type of ventilator
is generally smaller, mostly used in emergency.
4. Intelligent, comprehensive: these ventilators have a variety of inspiratory
phase conversion mode, a variety of conversion mode on-demand settings, in the computer
intelligent control, the machine automatically adjusts the relevant parameters, to achieve the
gas supply. For example, the pressure safety valve in the volume conversion mode is the pressure conversion
mode, when the pressure exceeds the set safety value, even if it has not yet reached the preset
tidal volume, the safety valve opens, forcing the early termination of inhalation to avoid
barometric injury. The advantages of this type of ventilator are computerized control, which ensures
higher precision, powerful expansion function, easy operation, strong generality
and complete respiratory modes, which is suitable for all kinds of patient treatment.
Second, the basic structure of the ventilator
The ventilator is mainly composed of electronic control and airway two major components.
The airway part is mainly a gas transmission system, including gas supply
(gas storage, pressure support), gas transmission, pressure flow monitoring and
correction. Compressed air and oxygen are mixed in the required proportions for the setup, and then sent to the patient
end at the set air pressure and flow rate through the piping and associated servo valves. The flow sensor feeds the measured actual value to the electronic control
control part and compares it with the setting value of the panel, and uses the error between the two to regulate the inhaled and exhaled gases by
controlling the servo valves.
The main function of the electronic control part is to control the ventilator to ventilate at a certain
frequency, tidal volume, and at the same time, monitor the feedback data from the corresponding sensors
, and alarm when it exceeds the limited range.
Third, through the mode and the scope of application:
Ventilator performance continues to improve and develop, mainly in the ventilation
mode of increasing, for the rescue of patients with respiratory failure to increase the convenience
and the chance of success. The correct and appropriate application of ventilation modes improves
efficacy and reduces complications.
1. Controlled ventilation (CV): the ventilator completely
replaces the patient's spontaneous breathing according to a predetermined respiratory rate, tidal volume, respiratory time ratio, and airway pressure. This mode is mainly used in cases of severe
respiratory depression or with apnea. The advantage is to ensure stable
ventilation and minimize the ventilator load, but it is easy to produce man-machine confrontation for patients with spontaneous
breathing.
2. assisted ventilation (assisted ventilation): patients with spontaneous breathing
inhalation ventilator to provide partial support, that is, the ventilator to send
the process is triggered by the patient's spontaneous respiratory air resulting in a slight decrease in airway pressure
to trigger the sensitivity of the trigger is adjustable, the adult can generally be adjusted to
0.2%, the trigger sensitivity is adjustable to
0.2%. p>
0.2emH20 or so in adults. It is mainly used for partial
ventilatory support in patients who are breathing spontaneously, but if the patient stops breathing spontaneously, the ventilator cannot provide ventilatory support because there is no trigger
.
3. Assist-control ventilation AV CV (assist-control ventila.
tion): this mode is a combination of the characteristics of AV and CV, when the patient
has voluntary breathing can establish the voluntary respiratory rate, and when the voluntary respiratory
frequency is lower than the preset
frequency or air pressure changes are not enough to trigger When the respiratory rate is lower than the preset frequency or the air pressure change is not enough to trigger, the respirator automatically provides respiratory supplementation at the preset frequency and tidal volume.
So
in the trigger for assisted ventilation, no trigger for control ventilation, from
and to ensure that the patient's necessary ventilation.
4. Command minute ventilation MMV (mandatory minute ventila.
tion): according to the patient's gender, age, weight, *** and metabolism
pre-set the amount of ventilation per minute, when the patient's spontaneous respiration triggered by a minute of ventilation
volume does not reach the pre-set volume, the ventilator to provide insufficient part of the ventilation,
i.e., the ventilator does not provide positive-pressure ventilation during autonomous MV> it only provides
continuous airflow for autonomous respiration; when autonomous respiration stops or autonomous
MV< preset MV, the ventilator provides air to ensure that the patient's minute-to-minute
volume of ventilation. This mode is generally used for smooth transition from controlled ventilation to voluntary
respiration during ventilator withdrawal and for anesthesia and postoperative respiratory support.
5. Intermittent mandatory ventilation (IMV) and synchronized intermittent mandatory ventilation (SIMV) (intermittent mandatory ventilation; synchro-
nized intermittent mandatory ventilation). SIMV (intermittent mandatory ventilation; synchro-
nized intermittent mandatory ventilation): Positive-pressure ventilation given by the ventilator to the patient at a set frequency, with the patient allowed to breathe on his or her own in between mechanical ventilation sessions
. Positive-pressure ventilation is given intermittently while the patient is breathing spontaneously, and the airflow for spontaneous breathing is supplied by the ventilator at a constant high-flow rate
. Commanded ventilation can be delivered either incompletely synchronized with the patient's spontaneous respirations
or synchronized (SIMV), and this mode is mainly used for
ventilatory support in ventilator withdrawal and partial respiratory failure.
6. Positive end-expiratory pressure PEEP (positive end-expiration
pressure), continuous positive airway pressure CPAP (continue positive air.
way pressure): PEEP is a procedure in which the patient's airway is artificially inflated at the end of expiration.
Way pressure): PEEP is to artificially raise the airway pressure above atmospheric pressure at the end of the patient's expiration.
CPAP is the maintenance of intra-airway pressure above atmospheric pressure throughout the respiratory cycle (inspiratory and expiratory phases) under conditions of spontaneous respiration.
These two modalities are used in severe asthma, obstructive sleep apnea
arrest syndrome, and respiratory failure. Because they increase peak and mean
airway pressure, there is a potential for barotrauma and circulatory depression.
7. Pressure support ventilation PSV (pressure support ventila.
tion): When the patient breathes spontaneously, the ventilator delivers a preset air
tract pressure (initiated by inspiratory-triggered sensitization), and at the end of the inhalation this pressure is eliminated
and the patient is free to exhale. This mode is better matched to the patient's inspiratory
flow rate, thus reducing the exertion of the respiratory muscles, and can be used either as a long-term ventilatory support for the patient
or as a withdrawal technique.
8. Pressure release ventilation (PRV)
tion: Provides partial ventilation
support by presetting periodic PEEP release, reducing peak airway pressure and the risk of pneumoconiosis, and increasing tidal volume
and minute ventilation.
9. BIPAP (bi level positive air
way pressure): During spontaneous respiration or mechanical ventilation, two different levels of positive airway pressure are given alternately, i.e., the airway pressure periodically switches between high
pressure and low pressure, and each level is independently adjustable
. Each pressure level is independently adjustable. The change in respiratory volume caused by the transition between the two pressure levels
is used to assist mechanical ventilation, thus maintaining positive expiratory pressure while
providing assisted ventilation during inspiration. The advantage is that the patient's spontaneous expiration
inhalation is easy to do little work, less dangerous, and suitable for almost all kinds of patients.
The key is the setting of the value, so it is more demanding on the doctor.
10. Pressure regulated volume control ventilation (pressure
regulated volume control ventilation): this mode of pressure cut
switching mode ventilation, the computer continuous determination of pulmonary thoracic compliance, according to the relationship between volume
volume pressure, calculation of the next ventilation to achieve the preset tidal volume. Based on the volume-pressure relationship, the computer calculates the inspiratory pressure required to reach the preset tidal volume during the next ventilation. The preset inspiratory pressure level is automatically adjusted (always to
75% of the calculated value). The actual tidal volume is matched to the preset tidal volume by continuous measurement and adjustment
with each breath.
11. Volume support ventilation (volume support venfila-
tion): For the combination of PRVCV and PSV, the ventilator automatically adjusts the level of PSV in response to the patient's
lung compliance and airway resistance to ensure the supply of tidal volume. tidal volume supply.