Secretions cause atelectasis and pneumonia during the postoperative period, especially in patients with a smoking history, pain, and inefficient cough. Secretion retention in airways may cause obstruction of broncopulmonary units and atelectasis, and this is even more pronounced in smokers and in patients with chronic lung disease. The diagnosis of sputum retention can be clinical and it is characterized by respiratory distress with rapid, shallow, and bubbly breaths. There was a strong association between sputum retention and postoperative pneumonia in patients with chronic obstructive pulmonary disease (COPD), smoking history, and poor analgesia [10]. There is a great importance for physiotherapy in this situation. At least two daily visits should be performed; some patients need more. Another noteworthy point is the hydration of patients for secretion mobilization. Oxygen therapy via a facemask inevitably dries secretions when non-humidified oxygen is used. This causes mucociliary dysfunction and a decreased ability to clear secretions, so humidified oxygen should be used. Sometimes mucolytic agents can be helpful. Chest physiotherapy is a therapeutic modality that should be kept in mind. Postural drainage, percussion, and vibration are applied to the affected lung opening and promote coughing during which physicians should provide adequate analgesia. Despite these interventions, tracheal suctioning can be used in patients who cannot remove secretions. Before suctioning, high oxygen fraction should be used in patients at risk for hypoxemia.

Fiberoptic bronchoscopy may be used for clearance of secretions which has the advantage of direct visualization of the tracheobronchial tree and the ability to take sputum samples for culture when a clinically infection is suspected. Sedation is required for this procedure in nonintubated patients; noninvasive ventilation may be used during the intervention to avoid hypoxemia.

Many comorbid conditions accompany lung cancer surgery. Approximately 50 % of patients with lung cancer also have COPD [11]. Patients with COPD may have ineffective cough, increased secretions, and impaired gas exchange after lung resections, especially hypercapnia secondary to hypoventilation. Some patients may need re-intubation and mechanical ventilation. Pulmonary rehabilitation includes breathing exercise, cough training, and self-management education; psychosocial support has been shown to decrease complications [12, 13]. Preoperative assessment of these patients for targeting reduces postoperative complications and improves survival. Pneumonia is the most significant postoperative complication that increases morbidity and mortality. These interventions may help reduce the incidence, severity, and risks of pneumonia. Smoking cessation and pharmacological therapies such as bronchodilators, mucolytics, and antibiotics if necessary are useful for patients preparing for lung resection and also those with chronic lung disease.

Pulmonary rehabilitation programs can be preoperatively and postoperatively conducted at certain time periods. These programs include breathing and coughing techniques, inspiratory muscle strength, home-based aerobic exercise, and incentive spirometry [14–16]. Spruit et al. showed that patients with poor functional status after lung cancer treatment improved their exercise capacity using a pulmonary rehabilitation program with a 6-min walk [17]. However, after patients are diagnosed as having lung cancer, they often feel that surgery must be planned as soon as possible and thus may refuse a pulmonary rehabilitation program.

The thoracic analgesia is crucial to keep the patient comfortable for reducing postoperative pulmonary complications after surgery. Surgical incision, intercostal nerve injury, and inflammation are major causes of pain after thoracic surgery. Thoracic epidural analgesia is still considered the gold standard for pain relief after thoracotomies, but recently some evidence showed that a paravertebral block had a similar analgesic effect with fewer adverse effects than thoracic epidural analgesia [18]. For reduced complications after thoracic surgery, patients should be able to breathe deeply, cough, and remove secretions and should be mobilized early. Postoperative ineffective pain relief associates with worsened pulmonary complications. Belda reported that a higher postoperative pain score was an independent predictor of postoperative respiratory infections [19]. Recently, multimodal analgesia has been preferred for post thoracotomy pain. In this regimen, regional blocks are combined with opioids, nonsteroidal anti-inflammatory drugs, acetaminophen, selective cyclooxygenase −2 inhibitors, and α2 agonists. Multimodal analgesia is more effective and has fewer adverse effects. When the age and comorbid conditions of these patients are considered, more attention must be paid to the drugs used for analgesia in this population.

In normal conditions, the lower respiratory tract is sterile. Most patients who undergo surgery have a history of smoking with subsequent impairment of mucociliary function and accumulation of secretions in the lung; therefore these patients have facilitating factors for the development of infection.

The source of pathogenic microorganisms responsible for pneumonia in this patient population is not yet clear. Preoperative colonization, colonization during intubation or mechanical ventilation, and aspiration during the perioperative period can cause pneumonia after thoracic surgery [20]. The incidence of airway colonization in patients with lung cancer varied between 10 and 83 % [1, 19, 21]. Taking samples using different methods (bronchoalveolar lavage (BAL), protected specimen brush (PSB), endotracheal aspiration (ETA), spontaneous sputum) and at different times (preoperative, perioperative, or postoperative period) may account for this wide range.

Some studies have been shown that healthy, nonsmoking patients have no airway colonization [22, 23]. Healthy smokers and patients with COPD had bacterial colonization at 29 % and 66 %, respectively [24, 25]. Monso showed that 25 % of 40 stable patients with COPD had airway colonization; the most commonly isolated microorganisms were Haemophilus influenzae and Streptococcus pneumonia [26].

Patients who undergo thoracic surgery have similar colonization patterns to patients with COPD. Although the relationship between airway colonization and ventilator-associated pneumonia has been proven, bronchial colonization and pneumonia in patients after lung cancer surgery are unclear. Several studies investigated this issue. Hirakata et al. investigated the airway colonization patterns in patients with primary lung cancer and nonmalignant lung disease and healthy volunteers [27]. The rate of bacterial colonization was significantly higher in patients with lung cancer (51.9 %) than in those with nonmalignant lung disease (37.3 %) and healthy volunteers (37.8 %), and the Gram-negative colonization was higher in this cancer group than in other patient populations. The pathogenesis of airway colonization in patients with lung cancer is not clear, but centrally located tumors and high body mass index were found to be risk factors for colonization [28]. Smoking and poor pulmonary functions also add risk for colonization in patients with COPD. Furthermore, sampling methods that evaluate the incidence of airway colonization are imperative in this patient population.

Which time period is important to the development of pneumonia with respect to colonization? Sok et al. performed a study to verify the origin of microorganisms that caused pulmonary infections after lung cancer surgery [29]. They obtained samples of sputum 3 days before surgery, during surgery, and 3 days after surgery. The microorganisms that caused infections were isolated as preoperative 18 %, intraoperative 13 %, and postoperative 63 %. They found that the microorganisms which caused pneumonia were the same with microorganisms which were isolated in sputum at the 3rd postoperative day. The authors concluded that the colonization of the airway usually occurs during the postoperative period; the oral cavity and pharynx were the source of pathogens.

Cabello et al. investigated distal airway colonization in patients with pulmonary carcinoma and obtained samples from proximal to the endobronchial lesion using a PSB [22]. They used ≥10² cfu/mL as a cutoff value for colonization and found that 42 % of patients had bronchial colonization. Sixteen of 25 isolated microorganisms were non-potential pathogenic microorganism, and the most isolated potential pathogen microorganism was H. influenza. Similarly, Ionas et al. found 41 % bronchial colonization in patients with resectable lung cancer [28].

Rather than the colonization of the airway, the similarity of microorganisms that colonize the airway and cause pneumonia is a more relevant issue. The correlation between these pathogens is controversial. Ionas reported that there was no relationship between postoperative infectious pulmonary complications and bronchial colonization [28]. Sok demonstrated that postoperative infective complications were caused by Gram-negative bacteria, whereas most of the positive cultures obtained preoperatively were Gram positive [29]. The change in the pattern suggests that the colonization of microorganisms in the early postoperative period may be caused by the aspiration of gastric contents and frequent interventions to the airway in the operating room and ICU. In contrast to these studies, some authors reported a good correlation between microorganisms isolated from patients who developed postoperative pneumonia with the same agents identified preoperatively [1, 19, 21, 30]. Appropriate prophylactic antibiotics and optimal duration of prophylaxis are the most imperative considerations for the prevention of postoperative pneumonia in patients who are colonized with potentially pathogenic microorganisms (PPMs) preoperatively.

The most common preoperatively isolated microorganisms from the airway are H. influenzae, S. pneumonia, and Staphylococcus aureus. Although approximately 50 % of postoperative pulmonary pathogens are not documented, some of the isolated pathogens have been different in various studies. In pneumonia developed during late postoperative period, resistant strains of gram-negative bacteria should be considered as potential pathogens. In the early postoperative period (first week), H. influenzae and S. pneumonia are the most common pathogens, but more resistant microorganisms such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumonia cause pneumonia in the late postoperative period. Cytomegalovirus (CMV) infection in patients with hematologic malignancies, patients who are human immunodeficiency virus positive, and lung transplant recipients is common, but the incidence of CMV infection in other types of cancer patients is not well known. A study performed in a surgical ICU showed that the incidence of CMV infections was around 35.6 % [31]. The essential thing here is to suspect a CMV and make the correct diagnosis, especially in patients under treatment with steroids. Preemptive antiviral therapy is administered in selected patient populations but not in thoracic surgery. Antiviral therapy should be considered for patients with severe pneumonia, ARDS, and resistant to classical antibacterial therapy in postoperative period especially for patients who underwent induction therapy. The widespread use of antibiotics also affects the type of microorganisms that colonize.