Anesthetic cause marked alterations in respiratory drive and cause decreased responses to hyper apnea and hypoxemia.
With the use of neuromuscular blocking agents and anesthetic drugs the diaphragm may be relaxed, resulting in reduced functional reserve capacity and thoracic volume with promotion of atelectasis.
Atelectasis the occurs usually involves the dependent areas of the lung and can persist for an extended period of time.
Chest and upper abdominal surgical procedures are associated with a vital capacity reduction of 50% and functional residual capacity by 30%.
Impaired pulmonary function after surgery related to pain, splinting and dysfunction of the diaphragm.
Following upper abdominal or thoracic surgery ribcage excursion and abdominal expiratory activities increase because of decreased CNS output to phrenic nerves inhibiting diaphragmatic stimulation.
These reflex inhibitions arise from sympathetic, vagal and splanchnic receptors.
Epidural anesthesia can block reflex inhibitions.
Protective mechanical ventilation intraoperatively is associated with a decreased incidence of postoperative pulmonary complications.
After noncardiothoracic surgery the best evidence to reduce postoperative pulmonary complications include lung expansion therapy with incentive spirometry, deep breathing exercises and continuous positive airway pressure after abdominal surgery (Lawrence VA).
Probable benefit to reduce postoperative lung complications include nasogastric tube decompression after abdominal surgery, and the use of short-acting neuromuscular blocking agents during anesthesia.
Laparoscopic surgery for abdominal surgery may be beneficial to reduce postoperative pulmonary complications but at present, clinical data is insufficient to make such conclusions.
The benefits of preoperative smoking cessation to decrease pulmonary complications following surgery is still unclear.
There is no benefit from routine use of parenteral or enteral type of hyperalimentation to reduce postoperative pulmonary complications.
Monitoring with pulmonary artery catheterization is also associated with a reduction in pulmonary complications in the perioperative.
Preoperative oral corticosteroids is probably effective in decreasing postoperative pulmonary complications in patients with COPD or who have uncontrolled symptoms.
Lung expansion modalities of the most effective for reducing the risk of postoperative primary complications in high risk patients.
Postoperative respiratory failure is a common indication for invasive mechanical ventilation and accounts for more than 20% of all patients receiving ventilatory support.
To facilitate early extubation and prevent postoperative respiratory failure noninvasive ventilation with positive pressure is utilized to reduce the work of breathing, increase and expiratory lung volume and improve oxygenation.
The use of noninvasive continuous positive airway pressure following abdominal surgery reduces postoperative pulmonary complications, including the need for re intubation.
In patients following lung resection the use of NIV with inspiratory pressure assist decreased re intubation rates by half versus usual care with supplemental oxygen, chest physiotherapy and bronchodilators alone.