Methods to prevent ventilator-associated lung injury: a summary

Mechanical ventilation can cause ventilator-associated lung injury (VALI). This may manifest itself in various forms such as pneumothorax or, at the most extreme level, multi-system organ failure. The exact mechanisms by which the injury occurs are not known but appear to involve the conversion of mechanical stimulation of alveolar membranes into intracellular signalling, with subsequent upregulation of inflammatory mediators that produce the damage. This has been termed biotrauma. Furthermore, disruption of alveolar-capillary membranes may allow the release of these mediators into the systemic circulation that underpins the systemic inflammatory response syndrome. Various protective ventilatory strategies may be employed in order to reduce the lung damage and shall be discussed in this paper.

Pneumothorax

Spontaneous pneumothoraces can occur without obvious underlying lung disease (primary) or in patients with known underlying lung disease (secondary). Management guidelines for spontaneous pneumothorax have been published by major professional organizations, but awareness and application among clinicians seems poor. First episodes of primary spontaneous pneumothorax can be managed with observation if the pneumothorax is small. If the pneumothorax is large or if the patient is symptomatic, manual aspiration via a small catheter or insertion of a small-bore catheter coupled to a Heimlich valve or water-seal device, should be performed. In general, definitive measures to prevent recurrence are recommended after the first recurrence of the pneumothorax, and can be achieved by medical (e.g. talc) or surgical (video-assisted thoracic surgery) pleurodesis. Secondary pneumothoraces should be treated with chest tube drainage followed by pleurodesis after the first episode to minimize any risk of recurrence. Traumatic pneumothoraces may be occult (not seen on an initial CXR) or non-occult. The majority are treated by placement of a chest tube. Selected patients may be treated conservatively, with approximately 10% of these patients eventually requiring chest tube placement. Iatrogenic pneumothoraces have a myriad of causes with transthoracic lung needle biopsy being most common. Transthoracic needle biopsy-related pneumothoraces have CT findings that can predict their occurrence and the need for chest tube placement. Iatrogenic pneumothoraces, regardless of cause, may be managed by observation or small bore chest tube placement, depending upon patient stability and the size of the pneumothorax.

Patient safety: effect of institutional protocols on adverse events related to feeding tube placement in the critically ill1 1No competing interests declared

BACKGROUND

Inadvertent passage of a nasoenteric feeding tube into the tracheobronchial tree can result in pneumothorax. Measures requiring feeding tube passage to 35 cm only followed by a radiograph to verify intraesophageal placement and creation of a specialized placement team were implemented to decrease the incidence of procedure-related pneumothorax. This study evaluates the effectiveness of our safety measures.

STUDY DESIGN

Radiology reports from January 2000 through July 2003 were searched by computer with an algorithm designed to detect feeding tube placements possibly associated with the complication of intrabronchial placement or pneumothorax. Results were manually examined to eliminate false positives and verify causality.

RESULTS

Feeding tubes were placed in 4,190 unique patients during the study period; 87 patients had an intrabronchial malposition, and 9 experienced a pneumothorax caused by their feeding tube. The safety measures resulted in a significant decrease in procedure-related pneumothorax (0.09% versus 0.38%, p < 0.05), and a decrease in pneumothorax among patients with an intrabronchial placement (3% versus 27%, p < 0.05). More than two-thirds of patients with a misplaced tube had an endotracheal tube or tracheostomy, illustrating that such patients are not protected. Repeated malposition in the same patient was surprisingly common; 32% of patients with one intrabronchial misplacement ultimately had multiple misplacements. The risk of pneumothorax increased with misplacement at night (p < 0.05) and increased exponentially with each additional misplacement (p < 0.05).

CONCLUSIONS

Creating a specialized placement team, and initiating the safety measure of limiting feeding tube placement to 35 cm and obtaining a radiograph before full advancement reduced the incidence of procedure-related pneumothorax.

[The combined effect of prenatal steroid prophylaxis, neonatal surfactant therapy and reduction of risk of complications from respiratory life support on survival rate of very low birthweight infants]

INTRODUCTION

Retrospective analysis on some factors possibly influencing survival rate of very low birthweight infants on respiratory life support has been carried out.

AIM

The aim was to find out about roles played by prenatal steroid prophylaxis, neonatal surfactant therapy and methods of reduction of complication risk emanating from respiratory life support in the outcome of treatment.

METHOD

The frequency rate of pneumothorax, pneumomediastinum and bronchopulmonary dysplasia was comparatively examined for all very low birthweight (less than 1500 g) neonates treated by respiratory life support in the I. Department of Obstetrics and Gynecology, Semmelweis University in 1999 (n = 178) and in 1989 (n = 78). Corresponding data were compared using t-tests.

RESULTS

In 100% of the 1999 patients in the focus of the current investigation (178 newborn infants) have received prenatal steroid prophylaxis and 55% of them (98 neonates) have received neonatal surfactant therapy. Respiratory life support resulted in pneumothorax in 7.8% of them (14 patients) and bronchopulmonary dysplasia in 12.3% of them (22 neonates). Frequency rate of complications for the neonates under investigation attributable to respiratory support or initial illness decreased from 38.6% in 1989 to 19.6% in 1999, a difference proven significant by t-test (p < 0.05). Survival rate increased from 34.6% in 1989 to 63.5% in 1999, which is again a significant difference indicated by t-test (p < 0.05). The differences are especially consequential considering that the average gestation age of the infants in the 1999 group was lower than that of the infants in the 1989 group.

CONCLUSION

Decrease in complication rate emanating from respiratory support and increase in survival rate over the 10 year period between 1989 and 1999 can be attributed to the combined effect of improvement in respiratory support therapy applied (aiming to minimise its adverse effects like barotrauma and volutrauma more effectively by refined technological means) and of the introduction of administering prenatal steroid prophylaxis and (if judged necessary) neonatal surfactant therapy. A considerable limitation of this study is the lack of separation of independent variables (the separate effects due to the separate treatments applied), but it is reasonable to believe that improvement was due to a combined effect of all changes in treatments indicated above. It is deemed probable that results can be further improved by finding ways to decrease barotrauma and volutrauma even more effectively than now.

Avoiding chest tube placement after video-assisted thoracoscopic wedge resection of the lung☆

OBJECTIVE

A chest tube is usually placed in the pleural cavity after wedge resection of the lung, even after thoracoscopic procedures. The aim of this study was to determine the validity and safety of postoperative management without chest tube placement for patients undergoing thoracoscopic wedge resection of the lung.

METHODS

Between 1998 and 2002, 93 patients underwent thoracoscopic wedge resection of the lung. In January 2000, we established the following criteria for avoiding chest tube placement: (1) absence of air leaks during intraoperative alternative sealing test, (2) absence of bullous or emphysematous changes on inspection, (3) absence of severe pleural adhesions, and (4) absence of prolonged pleural effusion requiring chest drainage preoperatively. Seventeen of 93 patients did not satisfy the criteria. The other 76 patients were divided into two groups: group 1 consisted of 34 patients who underwent thoracoscopic resection before 1999 and in whom a chest tube was routinely placed in spite of retrospectively meeting the criteria, group 2 consisted of 42 patients who underwent thoracoscopic resection after 2000 and in whom chest tube was not placed. The clinical data were evaluated and analyzed between the two groups.

RESULTS

Two patients in group 1 required new intervention after removal of a chest tube that had been inserted during the operation due to recurrence of a pneumothorax, so did two patients in group 2 after the operation. The rate of late pneumothorax requiring intervention is similar in groups 1 and 2. No differences were found between the two groups with regard to postoperative chest pain and hospital stay. No patients experienced a significant adverse outcome.

CONCLUSIONS

Avoiding the chest tube placement did not increase postoperative morbidity if carefully selected criteria are met.

CT-guided fine-needle aspiration of lung nodules: effect on outcome of using coaxial technique and immediate cytological evaluation

PURPOSE

To evaluate the risk of pneumothorax during CT-guided fine-needle aspiration (FNA) of lung nodules with single needle and coaxial needle techniques and to assess the effect on diagnostic accuracy of immediate cytological examination of lung FNA samples.

MATERIALS AND METHODS

This prospective study analysed 53 patients undergoing transthoracic FNA biopsy of lung. 36 cases were performed by a radiologist using a coaxial technique, with 17 cases performed by a radiologist using a direct single-needle method. Effect of technique on occurrence of pneumothorax was recorded. FNA samples from all the patients in the study were examined immediately on-site by a cytologist or MLSO to determine whether sufficient aspirate had been obtained. Provisional diagnosis at immediate examination was compared to final diagnosis following full pathological evaluation.

RESULTS

Coaxial and non-coaxial groups were comparable for age and gender. Number of pleural passes was significantly lower in coaxial group (P < 0.01). Pneumothorax occurred in six (17%) of the 36 patients biopsied by coaxial technique, compared to four (24%) of the 17 patients by non-coaxial method (P = 0.55). Chest tube placement was required in four patients (11%) in the coaxial group, and two patients (12%) in the non-coaxial group (P = 0.85). A provisional cytological diagnosis was recorded for 74% of the patients in the study. 83% of the provisional reports were accurate on comparison with full pathology report. Specimen size was sufficient in 81% of cases.

CONCLUSIONS

The use of coaxial technique for CT-guided lung FNA biopsy reduced the number of pleural passes but did not significantly reduce the occurrence of pneumothorax. Immediate cytological examination of FNA specimens provided an accurate provisional diagnosis in the majority of cases, and should be routinely employed.

An Audit of Medical Thoracoscopy and Talc Poudrage for Pneumothorax Prevention in Advanced COPD

OBJECTIVES

To prospectively study all patients with COPD and spontaneous pneumothorax (SP) who underwent thoracoscopic talc poudrage (TP) under local anesthesia to determine its efficacy and safety in recurrence prevention.

METHODS

Data on clinical measurements, complications, duration of chest tube drainage, length of hospital stay, and outcome were collected.

RESULTS

Forty-one patients (38 men and 3 women) with a mean (+/- SD) age of 70.7 +/- 7.2 years were treated. All patients had COPD, with a mean FEV(1) of 41 +/- 14% predicted. The majority of SPs measured 20 to 50% in size, and 34% were recurrent. Three grams of talc were insufflated into the pleural cavity without complications. Thirteen patients (32%) complained of pain, 5 (12%) developed fever, 27 (66%) had subcutaneous emphysema, and 7 (17%) had prolonged air leaks. Postoperative chest tube drainage and hospital stay were 4 and 5 days, respectively. Success was 95% after a median follow-up of 35 months. Four patients with FEV(1) of < 40% predicted died within 30 days of the procedure, yielding a mortality rate of 10%. FEV(1) (in liters), FEV(1) (in % predicted), and ischemic heart disease were risk factors that influenced early mortality.

CONCLUSION

Thoracoscopic TP is effective for pneumothorax prevention and can be performed with acceptable mortality in patients with advanced COPD.

An open question

The lungs are surrounded by the pleural membranes. The visceral pleura directly covers the lung and is separated from the parietal pleura by a layer of surfactant, which reduces friction during respiratory movement. A potential space exists between these two layers, and they may become separated by fluid or air. A lung can collapse to the size of a fist under pressure from either. Standard treatment in the field for an open chest wound is an occlusive dressing. The first thing that can be used to occlude the wound is a gloved hand. After placing the dressing, evaluate the breath sounds and determine if they have improved. The dressing should be taped down on three sides, leaving one side open to relieve the pressure during exhalation (one-way valve). "Burping" the dressing involves lifting one side to make sure any pressure buildup is relieved, as occasionally the dressing can become adhered to the skin, which may lead to a tension pneumothorax. If, after ensuring the occlusive dressing is properly in place, the respiratory rate increases, distress level worsens, oxygen saturations fall and breath sounds decrease, then needle decompression is required. A neurovascular bundle is located underneath each rib, and it is important to avoid damage to that bundle by performing a decompression over the top of a rib. If the patient is intubated before the development of a tension pneumothorax, carefully evaluate the breath sounds (especially if the left-side sounds are diminished) to determine if the ET tube needs to be withdrawn a centimeter. The rescuer performing ventilation will usually recognize a tension pneumothorax by the difficulty in bagging the patient. Remember, when you perform a needle thoracentesis, you are creating an open chest wound. Early signs and symptoms of a tension pneumothorax include diminished or absent breath sounds, severe dyspnea, narrowing pulse pressure, tachycardia and restlessness. Neck veins may be distended, but this can be a normal finding in a supine patient. The classic sign is a deviated trachea; the trachea shifts toward the "good" lung as the buildup of pressure collapses the "bad" lung. This is a late sign and suggests the tension pneumothorax has been developing for some time. One sign that does not normally accompany a plain pneumothorax is hypotension. In this case, the persistent low BP, combined with cool, mottled skin and a delayed capillary refill time, led providers to suspect that a hemothorax was developing as well. With endotracheal intubation and pleural decompression, the positive-pressure ventilations allowed the affected right lung to inflate more fully, utilize more of the available alveolar space and "bag out" some of the blood pooling at the base. The patient's vital signs and saturation improved. He needed surgical treatment and removal of the blood in the pleural space before ventilation and oxygenation could normalize.

Ultrasound Guidance Speeds Execution and Improves the Quality of Supraclavicular Block

In this prospective study, we assessed the quality, safety, and execution time of supraclavicular block of the brachial plexus using ultrasonic guidance and neurostimulation compared with a supraclavicular technique that used anatomical landmarks and neurostimulation. It was hypothesized that ultrasonic guidance would increase the proportion of successful blocks, decrease block execution time, and reduce the incidence of complications such as pneumothorax and neuropathy. Eighty patients were randomized into two groups of 40, Group US (supraclavicular block guided in real time by a two-dimensional ultrasonic image, with neurostimulator confirmation of correct needle position) and Group NS (supraclavicular block using the subclavian perivascular approach, also with neurostimulator confirmation). Blocks were performed using bupivacaine 0.5% and lidocaine 2% (1:1 vol) with epinephrine 1:200000 as the anesthetic mixture. The onset of motor and sensory block for the musculocutaneous, median, radial, and ulnar nerves was evaluated over a 30 min period. At 30 min 95% of patients in Group US and 85% of patients in Group NS had a partial or complete sensory block of all nerve territories (P = 0.13) and 55% of patients in Group US and 65% of patients in Group NS had a complete block of all nerve territories (P = 0.25). Surgical anesthesia without supplementation was achieved in 85% of patients in Group US and 78% of patients in Group NS (P = 0.28). No patient in Group US and 8% of patients in Group NS required general anesthesia (P = 0.12). The quality of ulnar block was significantly inferior to the quality of block in other nerve territories in Group NS, but not in Group US; the quality of ulnar block was not significantly different between Groups NS and US. The block was performed in an average of 9.8 min in Group NS and 5.0 min in Group US (P = 0.0001). No major complication occurred in either group. We conclude that ultrasound-guided neurostimulator-confirmed supraclavicular block is more rapidly performed and provides a more complete block than supraclavicular block using anatomic landmarks and neurostimulator confirmation.

IMPLICATIONS

Ultrasound-guided neurostimulator-confirmed supraclavicular block is more rapidly performed and provides a block of better quality than supraclavicular block using anatomic landmarks and neurostimulator confirmation.

Pathogenesis and Treatment of Primary Spontaneous Pneumothorax: An Overview

The exact pathogenesis of primary spontaneous pneumothorax (PSP) remains unknown. Furthermore, various specialists including pulmonologists, surgeons, emergency care physicians, radiologists and others are known to treat this disorder in clinical practice. As a consequence, guidelines on the management of PSP are scarce, and differences in treatment approaches persist. In this paper, evidence on the pathogenesis and on various treatment techniques and strategies is reviewed. An algorithmic treatment approach is proposed.

[Pneumothorax during nasal-CPAP: a predictable complication?]

OBJECTIVE

Pneumothorax (PNX) is a relatively common complication of nasal-CPAP (N-CPAP). Aim of the study was to identify prognostic factors of its onset.

METHODS

Seventy-seven newborns, admitted from January to December 2002 to the Neonatal Intensive Care Unit of Brescia, who were treated with N-CPAP with Infant Flow System as first intention, were included. Gestational age and birth weight were (mean +/- SD) 33.7 +/- 3.02 weeks and 2.047 +/- 684 grams, respectively. Infants were put on N-CPAP at 2.7 +/- 4.1 hours of life. The duration of treatment was 27.7 +/- 27.7 hours.

RESULTS

Fifty-one neonates improved and N-CPAP was discontinued, 26 worsened and required intubation and mechanical ventilation. Eight of them developed PNX (10,3%). No significant differences were found among the three groups (improved, worsened without PNX and worsened with PNX) concerning mode of delivery, gestational age, birth weight and blood gases. The patients with PNX needed a FiO2 28% higher than the initial value after 12 hours of treatment, and 46% higher at 24 hours (p = 0,017). At diagnosis, FiO2 was 53,5% higher than the initial value (p = 0,005).

CONCLUSION

A 40% increase of FiO2, during the first 24 hours of N-CPAP may represent an useful marker to identify the infants at high risk of developing a pneumothorax.

Ventilator auto-triggering in a patient with tuberculous bronchopleural fistula

We report a case of ventilator auto-triggering resulting from tuberculous bronchopleural fistula being managed with chest tube suction. Early recognition of bronchopleural fistula-related auto-triggering is extremely important. Auto-triggering can lead to serious adverse effects, including severe hyperventilation and inappropriate escalation of sedatives and/or neuromuscular blockers (administered to reduce spontaneous breathing efforts). Auto-triggering was confirmed in our patient when tachypnea persisted despite pharmacologic neuromuscular paralysis. Auto-triggering can be reduced or eliminated by decreasing ventilator trigger sensitivity or by decreasing the air leak flow by reducing the degree of chest tube suction.

Which patients are at risk? Evaluation of the morbility and mortality in newborn pneumothorax

This study was conducted to evaluate the morbidity and mortality among the newborns hospitalized for pneumothorax. The data of 83 cases were analysed retrospectively according to gestational age, weight, underlying primary lung pathology, age of admittance, side of pneumothorax, drainage time, need for mechanical ventilation and mortality. Male: Female ratio was 1.6:1. Mean duration of admission was 63.8 hours (2 hours-20 days). 51 patients (61.4%) weighed les than 2500g and 41 patients (49.4%) were preterms. The mean weight was 2280 g (640-5170). Fifty one patients (61.4%) needed mechanical ventilation. The pnemothorax was on the right in 44 (53%), left in 21 (25.7%) and bilateral in 18 patients (21.7%). Overall 32 babies died. Among the non-survivors, 22 (68%) were preterm and there was a defined underlying lung pathology in 24 (75%). Twenty nine (90.6%) of them needed mechanical ventilation. The difference in mortality was significant in the presence of primary lung disease, low birth weight, prematurity and use of mechanical ventilation (P <005).

An evaluation of the supraclavicular plumb-bob technique for brachial plexus block by magnetic resonance imaging

Partly based on magnetic resonance imaging studies, the "plumb-bob" approach for brachial plexus block was designed to minimize the risk of pneumothorax. Nevertheless, the risk of pneumothorax has remained a concern. We analyzed magnetic resonance images from 10 volunteers to determine whether the risk of pneumothorax was decreased with this method. The recommended initial needle direction is anteroposterior through the junction between the lateral-most part of the sternocleidomastoid muscle and the superior edge of the clavicle. If the initial placement is not successful, the brachial plexus may be sought in sectors 20 degrees -30 degrees cephalad or caudad to the anteroposterior line in a sagittal plane through the insertion point. We found that the anteroposterior line reached the pleura in 6 of 10 volunteers without prior contact with the subclavian artery or the brachial plexus, but always with contact with the subclavian vein. To reach the middle of the brachial plexus, a mean cephalad redirection of the simulated needle by 21 degrees was required (range from 41 degrees cephalad to 15 degrees caudad in one case). We conclude that the risk of contacting the pleura and the subclavian vessels may be reduced by initially directing the needle 45 degrees cephalad instead of anteroposterior. If the brachial plexus is not contacted, the angle should be gradually reduced.

IMPLICATIONS

In magnetic resonance images of volunteers, simulated needle passes with the "plumb-bob" approach to the supraclavicular brachial plexus block were analyzed for precision and risk profile. To avoid needle contact with the lung, the subclavian vein, and the subclavian artery, our results suggest a change in the method's initial needle direction.

[Toleration of high altitudes by patients with heart and pulmonary diseases]

The decisive limiting parameter in such patients is the lower oxygen partial pressure in inhaled air. It is, however, still possible for patients with coronary heart disease, high blood pressure or bronchial asthma to tolerate high altitudes without having to experience health problems. Prerequisites, however, are adequate acclimatization, optimal medication and pre-travel stable status. In addition, patients must be informed about emergency measures and how to recognize high-altitude sickness. To prevent pneumothorax leading to rapid decompression during flights, particular attention must be addressed to the problem of trapped air in patients with emphysema or cystic fibrosis.

Patient positioning after fine needle lung biopsy-effect on pneumothorax rate

PURPOSE

To evaluate the efficacy of precautionary positioning in preventing the development of pneumothorax and reducing the rate of chest tube placement after fluoroscopy-guided transthoracic needle biopsy (TTNB).

MATERIAL AND METHODS

One hundred and seven patients who underwent TTNB were randomly assigned to one of two postbiopsy treatment groups: patients were placed with (precautionary positioning group) and without (non-precautionary positioning group) recumbent puncture site either down (n = 59 and 48, respectively) for at least 30 min.

RESULTS

The overall pneumothorax rate was 8.4% (n = 9). Four of the 9 patients needed chest tube insertion. Pneumothorax rate was 8.33% (4/48) and 8.47% (5/59) in the precaution and non-precaution groups, respectively. Rate of chest tube insertion was 6.25% (n = 3) and 1.85% (n = 1) in the precaution and non-precaution groups, respectively. There was no statistically significant difference in the rate of pneumothorax and chest tube insertion between the two groups.

CONCLUSION

Precautionary positioning after TTNB does not reduce the incidence of postbiopsy pneumothorax and rate of chest tube insertion.

Prospective evaluation of safety and efficacy of the supracostal approach for percutaneous nephrolithotomy

OBJECTIVE

To prospectively evaluate the safety and efficacy of the supracostal approach for percu-taneous nephrolithotomy (PCNL), as it is usually avoided because of concerns about potential chest complications.

PATIENTS AND METHODS

Between August 1998 and August 2001, 465 patients underwent PCNL. Supracostal access was obtained in 62 patients (63 renal units), comprising 13% of the procedures. The indications for a supracostal approach were staghorn, upper ureteric, superior calyceal stones and high-lying kidneys. The data were analysed for stone clearance, need for additional punctures and the complications associated with supracostal puncture.

RESULTS

The supracostal was the only access in 63% of the PCNL procedures. Additional punctures were required mainly for staghorn stones (15 of 23). Overall, 90% of the patients were rendered stone-free or had clinically insignificant residuals with PCNL alone. In patients with staghorn stones, they were completely cleared in 84% of renal units. Significant chest complications developed in three (5%) patients, which required insertion of a chest tube. One (2%) patient developed haemothorax secondary to injury of the intercostal artery. All the patients recovered uneventfully.

CONCLUSIONS

These results indicate that supracostal access provides high clearance rates with acceptable complications; it should not be avoided for fear of chest complications. A chest X-ray after surgery should be routine, to detect any complication.

Clinical process improvement: reduction of pneumothorax and mortality in high-risk preterm infants

OBJECTIVE

To develop multidisciplinary clinical process improvement methods using evidence-based medicine to decrease the incidence of pneumothorax in a NICU.

STUDY DESIGN

All inborn infants <28 weeks' gestation (n=79) served as the historical baseline group. A prospective protocol, using evidence-based medicine and a rapid-cycle, multidisciplinary clinical process improvement method, was designed to measure changes in the incidence of pneumothorax in subsequent infants of similar gestational ages.

RESULTS

Sixty consecutive inborn infants <28 weeks' gestational age comprised the study group. In comparison to the historical control group, there was a significant reduction in the incidence of pneumothorax (from 26.6% to 10%, p=0.018) and in mortality (36.7% to 15%, p=0.007) without adversely affecting any other measured outcome variable.

CONCLUSIONS

Introduction of multidisciplinary clinical process improvement methods can significantly decrease the incidence of adverse outcomes in neonatal intensive care units.