Pulmonary atelectasis after anaesthesia: Pathophysiology and management

Abstract

The pathophysiological basis of pulmonary atelectasis is reviewed and risk factors that enhance lung collapse are discussed. Management strategies to reduce or eliminate risk factors and to prevent collapse are discussed and the rational bases of these strategies are identified.Instability of lung alveoli is a consequence of surface tension and regional differences in alveolar size. The inherent tendency of alveoli to collapse is enhanced by the following risk factors; low lung volume, high closing volume, oxygen therapy, a rapid shallow ventilatory pattern, chronic lung disease, smoking, obesity, postoperative pain following abdominal or thoracic surgery, narcotic induced ventilatory depression, and neurological, neuromuscular, muscular and musculoskeletal diseases associated with mechanical impairment of respiratory function. The primary goal of perioperative respiratory management is prevention of atelectasis. Appropriate management strategies include physiotherapy and delay of elective surgery if substantial improvement in respiratory status can be achieved by specific treatments such as antibiotics, bronchodilators, steroids, and reduction of tobacco use and caloric intake. In selected cases, elective postoperative controlled ventilation may be indicated.KEY WORDS: ANAESTHESIA, COMPLICATIONS, atelectasis; LUNG, atelectasis.LUNG COLLAPSE and infection leading to acute respiratory failure is a major cause of post surgical morbidity and mortality. 1'2 Small area, of "silent" pulmonary atelectasis develop insidiously and frequently precede overt clinical evidence of lung collapse and other associated postanaesthetic pulmonary problems) It is the purpose of this paper to review the pathophysiology and pathogenesis of pulmonary atelectasis and the physiological basis for pulmonary management in the postoperative period. PATHOPHYSIOLOGY AND PATHOGENESIS OF ATELECTASISThe inflated lung is inherently unstable; in other words, it tends to collapse spontaneously, an observation that may be confirmed directly in the apnoeic lung at thoracotomy. The tendency to collapse results from two fundamental physical characteristics of the intact lung and is The first physical characteristic is the presence of surface tension at the gas liquid interface of the alveoli. In an isolated alveolus, assumed to be spherical in shape,* the pressure (P) tending to collapse that alveolus is given by the following expression of Laplace's Law-2T P= r where T = surface tension and r = radius of curvature of the alveolus: This relationship indicates that the pressure tending to collapse the alveolus is directly proportional to the surface tension at the alveolar lining and inversely proportional to the radius (or the size) of the alveolus. *It is recognised that the spherical balloon model is a considerable simplification of alveolar shape. A more precise equation to compute the collapsing pressure within non-spherical objects is given by P = T~/r~ + T2/r2, where r~ and r z are the principal radii of curvature and T~ and T2 correspondi...

High Intraoperative Inspired Oxygen Does Not Increase Postoperative Supplemental Oxygen Requirements

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Pulmonary Atelectasis After Reconstruction With a Rectus Abdominis Free Tissue Transfer

“…Smoking history, duration of anesthetic, age, and types of surgery are also considered to be risk factors. 4,5 Seikaly et al 1 reported that a pectoralis major myocutaneous flap may increase the frequency of postoperative pulmonary atelectasis. In contrast, Schuller et al 2 contradicted this and found no increased incidence of clinically relevant atelectasis in their patients undergoing pectoralis major myocutaneous flap reconstruction.…”

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Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children

“…Most anesthetic agents promote atelectasis formation shortly after induction, leading to a decrease in FRC and ventilation homogeneity and potentially to hypoxemia [39][40][41][42]. Therefore, prevention of atelectasis during anesthesia or sedation is important in all children as atelectasis persists well into the postinterventional period and can have a negative impact on patient recovery [42].…”