Anesth Pain Med.  2011 Jul;6(3):244-248.

Effects of upper airway obstruction on respiratory mechanics in a variable compliance model

Affiliations
  • 1Department of Anesthesiology and Pain Medicine, Jeju National University College of Medicine, Jeju, Korea. pjcook@jejunu.ac.kr

Abstract

BACKGROUND
Upper airway obstruction is caused by an intrinsic or extrinsic neck mass and vocal cord paralysis. A recognized hazard of prolonged endotracheal intubation is progressive airway occlusion resulting from deposition of secretions. If the obstruction persists, it may be life threatening condition. However, early diagnosis of partial airway obstruction is very difficult because patients are asymptomatic and do not have lesions with abnormal radiological characteristics.
METHODS
In the test lung model, lung compliances were set to normal (25 ml/cmH2O; [control, C25 group]) and to levels seen in chronic obstructive pulmonary disease (40 ml/cmH2O; [C40 group]), and acute respiratory distress syndrome (20 ml/cmH2O; [C20 group] and 15 ml/cmH2O; [C15 group]). A ventilator (Drager Fabius GS, Germany) was attached to a test lung, and a series of endotracheal tubes (ETTs) ranging in size from 7.5 to 2.5 mm in inner diameter (ID) of the connector were used to simulate progressive occlusion. During the lung compliance and the connector size were changed, we measured some respiratory mechanics.
RESULTS
Progressive ETT occlusion induced an increase in the peak inspiratory pressure. In the C40 group, the inspiratory pause pressure spontaneously increased on repeated ventilation. Auto- positive end-expiratory pressure (Auto-PEEP) was observed under the condition of high compliance and occlusion. Dynamic compliance decreased at an ID of 5.5 mm in all groups. Respiratory resistance was inversely proportional to the ID of the connector.
CONCLUSIONS
The dynamic compliance and resistance were significantly changed. However the change of static compliance had little effect on respiratory mechanics.

Keyword

Airway obstruction; Airway resistance; Auto-PEEP; Lung compliance

MeSH Terms

Airway Obstruction
Airway Resistance
Compliance
Early Diagnosis
Humans
Intubation, Intratracheal
Lung
Lung Compliance
Neck
Positive-Pressure Respiration
Positive-Pressure Respiration, Intrinsic
Pulmonary Disease, Chronic Obstructive
Respiratory Distress Syndrome, Adult
Respiratory Mechanics
Ventilation
Ventilators, Mechanical
Vocal Cord Paralysis
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