الفهرس 
Anatomy of the AirwayOnly 14 pages are availabe for public view
Abstract
The term airway refers to the upper airway, consisting of nasal and oral cavities, pharynx, larynx, trachea, and principal bronchi. The airway in humans is primarily a conducting pathway.
After the airway classification is determined, the anesthesiologist needs to complete the airway examination.
Investigations where concern exists regarding upper airway calibre and function, further information may come from radiographic, endoscopic and physiological evaluation.
An airway assessment score based on criteria of the LEMON method is able to successfully stratify the risk of intubation difficulty.
Positive end-expiratory pressure (PEEP) refers to pressure in the airway at the end of passive expiration that exceeds atmospheric pressure. The application of a small amount of PEEP has been considered physiological. It is generally thought that a PEEP level of 3–5 cm of H2O reproduces the “back pressures” generated by a normal glottis in nonintubated subjects.
Mean airway pressure (MAP) is an average of the airway pressure throughout the respiratory cycle.
The plateau pressure is the pressure applied (in positive pressure ventilation) to the small airways and alveoli which represents the pressure during a period of no gas flow.
The peak pressure is the pressure measured by the ventilator in the major airways, which represents the maximum pressure obtained during active gas delivery.
Airway pressure should be monitored in all ventilated patients, as high airway pressure are associated with ventilator – induced lung damage (barotrauma and volutrauma). In patient with normal lungs, the peak airway pressure should be less than 35 cmH2O.
In cases of increased tidal volume or decreased pulmonary compliance, the PIP and plateau pressure rise together proportionately. If the peak pressure rises with no change in plateau pressure, increased airway resistance should be suspected or high inspiratory gas flow rates.
It should be noted that excessive mean and\or peak airway pressure may be associated with barotrauma or pressure-induced pulmonary injury (volutrauma). In addition, excessive mean airway pressure may also cause decrease in cardiac output and subsequently tissue perfusion and Pneumothorax, a potentially acute life- threating condition.
Management of cases of high airway pressure under anesthesia is careful preoperative identification of patients who are likely to develop intraoperative or postoperative bronchospasm.
Although mild wheezing and elevation of peak inspiratory pressure are relatively common, life threatening bronchospastic attacks under anaesthesia are relatively uncommon A retrospective review of asthmatic patients revealed a surprisingly very few intra or postoperative incidence of bronchospasm.
When the diagnosis of bronchospasm is established during a general anaesthetic, the initial therapy may consist simply of increasing anaesthetic depth. However, the use of profound levels of inhaled anaesthesia may not be practical in severe bronchospasm because of the difficulty in delivering the drugs to the airways and may produce severe hypotension and arrhythmias before achieving the needed bronchodilation.
The secondary management of acute brodchospasm sould address the underlying cause. Conrticosteroids and antihistamines have a role in the secondary treatment of brondchospasm and should be given early if the problem is not settling with initial measures.