Prevention Of Postoperative Pulmonary Complications With Noninvasive Positive Pressure Ventilation: A Prospective Randomized Control Study

BackgroundAlthough surgical procedures and postoperative care have been improved over time, postoperative pulmonary complications, including atelectasis, pulmonary infection, respiratory failure are still major clinical problems. The overall rates of pulmonary complications after thoracic surgery are around 30%, ranging from 7% to 49% as reported in the literature. Pulmonary complications are the main causes of morbidity and mortality in patient with post-thoracic surgery. The damage of lung function resulting from various impacts of post-thoracic surgery is often initiating factors of pulmonary complications, and conventional management and respiratory therapy (oxygen therapy, Bronchodilator drugs, mucolytic agents, antibiotics, physiotherapy, etc.) often failed to reverse the damage of lung function, and eventually respiratory failure developed in some patients. Invasive mechanical ventilation (ETMV) through tracheal intubation is the traditional management for severe respiratory failure with proven efficacy. However, ETMV is also associated with a number of complications. In last decade, there have been reports about noninvasive positive pressure ventilation (NPPV) on PPCs, showing that NPPV might be effective in managing PPCs. As reported in the literature abroad, NPPV could reduce intubation rate and mortality in post-thoracic surgery patients complicated with respiratory failure, although the results were not consistent between different studies. There is no evidence based on large sample size, prospective, randomized control trial yet. It is unclear whether or not prophylactic use of NPPV in post-thoracic surgery patients can reduce the morbidity of pulmonary complications, which demands further clinical investigation. We hypothesized that NPPV may facilitate the expansion of the lung through positive airway pressure and increased inspiratory drive, which might be beneficial for the prevention and treatment of PPCs in patients of post-thoracic surgery.ObjectivesProspective randomized controlled study was employed to explore the effects and safety of NPPV in preventing PPCs as well as lung re-expansion in post-thoracic surgery patients, which could provide scientific evidence for the use of NPPV in post-thoracic surgery patients.Subjects and methodsSubjects: From August 2008 to January 2009, fifty thoracic surgical patients were enrolled. Inclusion criterion are as following: 1. Patient's approval to participate in the study with NPPV therapy. 2. Patients are conscious and cooperative, able to protect airway, such as effective cough and expectoration. 3. Hemodynamic stability. 4. No contra-indication of NPPV application. The exclusion criterion are as following: 1. Non-cooperative, unconscious status. 2. Hemodynamic instability. 3. Facial trauma or post-surgery. 4. Copious airway secretions and inability of expectoration or high possibility of aspiration. 5. Complicated with upper digestive tract bleeding. 6. Severe hypoxemia (PaO2 <45mmHg) and / or severe acidosis (pH≤7.2). 7. Pneumothorax or pneumomediastinum without adequate drainage.Study design: This is a prospective and randomized control trial. Enrolled patients were randomly divided into conventional treatment group and NPPV group. Conventional treatment including thoracic drainage, oxygen therapy, antibacterials, mucolytic agents and nutritional support; NPPV group were given NPPV therapy on the basis of conventional treatment. Before surgery, the procedure, potential benefits and adverse effect of NPPV were explained to the patient and their family members. After patient's approval to involve in the study, a trial of use of NPPV for one hour was carried out so that the patient can be familiar with the NPPV procedure. The procedure of NPPV application is in accordance with the"Expert Consensus On Clinical Application Of Noninvasive Positive Pressure Ventilation". The actual procedure is as following: 1. Patient's assessment. 2. Obtaining patient's approval. 3. Semi-supine Posture (30 degree to 45 degree) 4. Choosing appropriate nasal or full face masks. 5. setting up airway humidification. 6. Starting Ventilator with initial settings of EPAP4 cmH2O, IPAP 6 ~ 8cmH2O and backup frequency 12 times/Min. The ventilator setting will be adjusted according to patient's comfort and tolerance in the following 5-20 minutes. 7. Close Monitoring and recording parameters related to ventilation.The following parameters, tolerability to NPPV and potential adverse reactions were recorded:1. PPCs rate: Including pulmonary infection, atelectasis, respiratory failure, etc;2. Pulmonary function one week after operation: Including conventional ventilatory function and the residual volume;3. Arterial blood gas in one week (1, 3, 7day after operation);5. Tolerance to NPPV;6. Other adverse reactions during hospitalization.ResultDemographic data and basic information of patients:A total of 50 cases were enrolled, 27 cases of the conventional group (control group, male: 20 and female: 7) and 23 cases in the experimental group (NPPV group, male: 17 and female: 6). Age was 55±12.9 yrs in control group and 59.1±9.7 yrs in NPPV group. Body mass index (KG/M2) was 22.4±3.4 in control group and 22.5±4.1 in NPPV group. Smoking index was 371±463 in control group and 488±498 in NPPV group. There is no significant statistics difference between the two groups (all p> 0.05).Underline diseases demanding operation treatment: 30 cases with pulmonary malignant tumors ( 60%), 11 (20%) with COPD and pulmonary bullae, 3 (6%) with benign lung tumor, 3 (6%) with organized pneumonia, 2 (4%) with bronchiectasis, 1 (2%) with esophageal cancer, and 1(2%) with pericardial cyst.The basic lung function: FEV1 (L): Control group 2.3±0.77, NPPV group 1.95±0.8. FEV1%Pred: Control group 78.5±25.1, NPPV group 76±29. FVC (L): Control 3.09±0.72, NPPV group 2.85±0.86. FVC% Pred: Control 91.3±16.6, NPPV group 89.5±18.4. FEV1/FVC (%): control group 73.3±13.2, NPPV group 68.3±17.3. TLC (L): control group 5.15±1.26, NPPV group 5.96±1.57. RV (L): control group 2.19±0.87, NPPV group 3.03±1.49. FRC (L): control group 3.16±0.95, NPPV group 3.63±1.53. All except for total lung volume (TLC, p=0.012) the pulmonary function parameters before operation were comparable between the two groups (p> 0.05).·Application of NPPV:Respironics BiPAP Synchrony ventilator was used for the study. For NPPV group, the potential benefits and adverse effects of NPPV were explained to the patients and the family member. After obtaining approval from the patients, a trial use of NPPV was carried out for one hour in an attempt to let the patient get used to the NPPV therapy. After operation, NPPV was used as soon as patients were consciousness, operative, able to cough effectively and protect airway, as well as without contra-indications of NPPV. Ventilation mode was PSV+PEEP, with mean IPAP 13±3.2cmH2O (ranging from 7cmH2O to 18cm H2O), EPAP 4cmH2O, Vt 475.5±114.5ml (ranging from 300ml to 700ml), MV 9.1±2L (ranging from 6L to 10L). The total duration of NPPV was 13.5±4.9 hours (ranging from 6.5 to 23 hours). 21 (91%) patients used nasal mask, and 2 (9%) patients used face mask. The tolerance assessment was good in 13 cases (57%), general in 7 (30%) cases, and poor in 3 (13%) cases. No adverse reactions observed in 21 cases (91%), gastrointestinal flatulence in 1 case (4.5%), phobia in 1 case (4.5%).·PPCs and recovery during hospitalization:During hospitalization, total PPCs occurred in 5 cases in NPPV group and 6 cases in control group, showing no statistically significant difference between two groups (p= 0.967). Subgroup analysis with atelectasis (2 cases in NPPV group and 1 in control group, p>0.05), bronchospasm (1 cases in NPPV group and 2 in control group, p>0.05), pneumonia (1 cases in NPPV group and 2 in control group, p>0.05) and acute respiratory failure (1 cases in NPPV group and 1 in control group, p>0.05).Poor re-expansion of the lung was observed in 3 cases in NPPV group and 13 cases in the control group, showing statistically significant difference between the two group (p= 0.008).Stratified analysis of PPCs and recovery during hospitalization:Stratifications were according to underline diseases and types of operation procedure. Subgroups analysis were conducted between: (1)COPD and lung tumor, (2) bullae resection and lobectomy, (3) benign disease and malignant lung disease . The morbidity of PPCs was statistically higher in COPD group than lung tumor group (45.5%VS12.9%, p= 0.038), while no statistical difference were observed between other layers (p= 0.085 and p= 0.273).Multiple factorial logistic regression analysis of PPCs:The following potential risk factors of PPCs were selected for logistic regression analysis: gender, age, smoking status, body mass index, type of operation, anesthesia time, bleeding volume, FEV1, FVC, FEV1/FVC ratio, COPD, hypertension, and diabetes. COPD was shown to be risk factor for PPCs (p= 0.027). FVC was shown to be potential protective factor of PPCs (B =- 1.121, p=0.058).Impact on volume of residual cavity after operation:The volume of residual cavity at one week after operation was significantly lower in NPPV group than conventional group (31.9±71.7ml vs 63.6±78.3ml, p= 0.02). However, this difference disappeared at three months after operation (0.09±0.27ml in NPPV group vs 0ml in conventional group, p= 0.317).·The impact on lung function :At One week after operation, the change of lung function parameters before and after operation were shown to be similar between NPPV and control group (△ FEV1,p=0.313,△FEV1%pred, p=0.943,△FVC, p=0.064,△FVC%pred, p=0.124,△FEV1/FVC, p=0.332).Multiple linear regression analysis of association between the changes of lung function parameters(△FEV1,△FVC) was associated with types of operation, with smaller reduction in bullous resection and wedge resection than in lobectomy.·Impact on patients'arterial blood gases:Repeated measures analysis of variance showed that there was not interaction between arterial blood gas changes and the use of NPPV. The arterial blood gas after operation was similar between two groups (△PaO2, p = 0.401,△OI, p= 0.253,△PaCO2 , p= 0.661).Conclusion: In the current study of prophylactic application of NPPV in post-thoracic surgery patients, the key findings are shown in the following:1. Better lung re-expansion, less volume of residual cavity in one week after operation;2. No effects on postoperative pulmonary complications and lung functions were observed;3. COPD is a risk factor and FVC is a potential protective factor of PPCs;4. Lung function decreased less in patients receiving bullous resection than lobectomy;5. The tolerance to the use of NPPV after surgery was generally good, with gastric distention in only 1 case. No increased pleural leakage was observed.Whether or not NPPV can facilitate lung re-expansion and prevent postoperative pulmonary complications after thoracic surgery demands a further study of large scale, multi-center prospective randomized controlled clinical trial.