Laryngeal Mask Knowledge Introduction
(Laryngeal Mask Airway
, LMA) is an artificial airway developed by British doctor Brain in 1981 based on dissection of adult throat structures. Officially put into production in 1988, and applied to the clinical. In 1991, it was approved by the FDA for clinical use. In 2003, the number of patients used was more than 100 million.
According to the invention and timing of the laryngeal mask, it is divided into three categories: the first generation is the LMA
; the second is the LMA-Fastrach
(Intubating LMA, ILMA); the third is the double tube Cover (ProSeal-LMA).
The main purpose of the mask:
1. As an airway between the mask
and tracheal intubation
is commonly used in the management of respiratory tract during general anesthesia, and it is possible to maintain spontaneous breathing as well as positive pressure ventilation;
2, for difficult airway treatment. At present, the effectiveness and safety of the third-generation laryngeal mask (double-laryngeal mask) in general anesthesia are greatly improved, and will gradually replace the ordinary mask.
Orthopharynx mask: Orthotic mask consists of three parts: ventilation tube, ventilation hood and inflation tube.
At present, there are three kinds of ordinary masks:
LMA-Classic: It is mainly used for the management of respiratory tract during general anesthesia and the treatment of difficult airways. It is suitable for limbs, body surface, and short operation; it should keep its own breathing; if the lung compliance is good, TV 6-8ml/kg,RR8- 12 times/minute, peak airway pressure is 15-20cmH2O, IPPV can be used.
LMA-Flexible: used in clinical use in 1990. The snorkel can be bent. It is mainly used for eye, nose, throat, head, neck, and oral surgery. It can maintain spontaneous breathing or IPPV. Compared with the LMA-Classic, the ventilator has little effect on the surgical field, and the ventilator is not easily formed into an angle and does not cause obstruction of the ventilator.
LMA-Unique (Laptop Mask): Used in clinical practice since 1998. It is mainly used for airway management in cardiopulmonary resuscitation under emergency situations outside the operating room and emergency room. Because it is a one-time use, it can prevent cross-infection; made of PVC material, its performance is not as good as the above two kinds of ordinary mask.
Use of common mask:
Anesthesia induction and maintenance: The depth of anesthesia needs to be sufficient in the insertion and maintenance phase of the mask to prevent respiratory reflexes. Whether muscle relaxants need to be given should be determined according to the needs of the operation. Anesthesia maintained inhalable O2/N2O/Isoflurane in combination with narcotic analgesics, intraspinal anesthesia, nerve block or local infiltration anesthesia.
Anesthesia monitoring: blood pressure, electrocardiogram, SpO2, and concentration of anesthetic gas.
Placement of common laryngeal mask: Better alignment, less irritation, and less complications with the standard placement method recommended by Brain. The timing of LMA removal was: the end of anesthesia, the patient’s spontaneous breathing, and reflexes of the respiratory tract. When the eye was opened and the opening was fitted, no suction stimulation was given before the LMA was pulled out.
Judgement of correct position of common mask after insertion: After insertion of common mask, judge whether the ventilation is effective or not. The position of the mask is generally judged by thoracic exercise, chest auscultation, end-tidal carbon dioxide monitoring, and the presence or absence of air leaks, and the location of the mask is checked by fiberoptic bronchoscopy (FOB) if necessary. Reported in the literature: After inserting the common mask, check with FOB: 83% can see the glottis, and 54% can see the epiglottis.
Reported in the literature: Oropharyngeal Leak Pressure (OLP) of Oropharyngeal Mask averages 20cmH2O. Therefore, in the use of common laryngeal mask in general anesthesia, should maintain spontaneous breathing, to avoid prolonged use of positive pressure ventilation; especially for patients with poor lung compliance should avoid the use of positive pressure ventilation.
Application of common laryngeal mask in difficult intubation patients:
In the past decade, LMA has attracted extensive attention in the application of difficult airways (difficulty in mask ventilation or/and difficulty in intubation). Mainly applied in the following two aspects:
1. Application of Unexpected Difficulties in Intubation: After induction of anesthesia, it was found that intubation was difficult, especially in the case of an emergency that “cannot be intubated and can not be ventilated through the mask”, LMA can be selected first. After the LMA is successfully inserted, the following three methods can be taken:
(1) The use of LMA can be performed directly on short body surface and extremity surgery while maintaining spontaneous breathing or IPPV;
(2) Tracheal intubation can be performed through the LMA.