 Abstract | | |
Aim: To clarify the epidemiological findings and characteristics of ground glass lesions on chest computed tomography (CT) after blunt trauma. Setting and Design: A medical college hospital and retrospective study. Materials and Methods: We retrospectively investigated all blunt chest trauma patients who were admitted from January 2004 to December 2010. The inclusion criteria were patients with: (1) chest CT examination on arrival, (2) intrathoracic traumatic lesions confirmed by initial CT, and (3) a second chest CT examination within 7 days from admission. We divided the subjects into two groups. A GG group included subjects who had ground glass lesions on initial chest CT and a control group included subjects who did not have the ground glass appearance. Results: The average age in the GG group was significantly lesser than that in the control group. The ratio of improvement for the value of SpO 2 /FiO 2 between on arrival and the second hospital day and ratio of improvement for CT findings between on arrival and the second CT examination in the GG group was greater than in the control group. Conclusion: The ground glass appearance on chest CT after blunt trauma was not rare, and the patients with ground glass lesions were younger and tended to have a better improvement of oxygenation and CT images in comparison with the patients without these characteristic lesions. Keywords: Blunt lung injury, CT, edema, ground glass appearance
How to cite this article:
Yanagawa Y, Sakamoto T. The epidemiological findings and characteristic ground glass appearance on chest CT among patients with blunt lung injury. J Emerg Trauma Shock 2012;5:238-42 |
How to cite this URL:
Yanagawa Y, Sakamoto T. The epidemiological findings and characteristic ground glass appearance on chest CT among patients with blunt lung injury. J Emerg Trauma Shock [serial online] 2012 [cited 2021 Apr 23];5:238-42. Available from: https://www.onlinejets.org/text.asp?2012/5/3/238/99693 |
| Introduction | |  |
The histopathological pattern of pulmonary contusions involves the disruption of alveoli, with subsequent intraalveolar and interstitial edema and hemorrhage. [1] Computed tomography (CT) allows for earlier identification of lung contusions compared with plain roentgenograms because of its high-contrast resolution. CT examinations usually reveal complete resolution of pulmonary contusions, without sequlae, within 1-2 weeks after the trauma. [1] However, we have reported two cases whose pulmonary ground glass lesions induced by a blunt chest trauma observed on CT completely disappeared within a few days following trauma, which led us to hypothesize that these lesions were traumatic lung edema induced by a transient malfunction of the blood-gas barrier in the alveoli. [2],[3]
Animal studies have demonstrated the formation of lung edema immediately after blunt trauma. [4] The lung is particularly vulnerable to injury because the blood-gas barrier is extremely thin. [5] Even among patients with normal chest CT after blunt trauma, radioisotope studies have revealed abnormal results based on the disturbance of the blood-gas barrier. [6] Accordingly, mechanical insults can cause a malfunction of the blood-gas barrier and lead to the formation of lung edema. We have reported only isolated transient ground glass traumatic lesions. [2],[3] However, we have experienced concomitant cases consisting of transient ground glass traumatic lesions and typical lung contusions. We herein provide the first report to investigate the epidemiological findings and characteristics of ground glass lesions on chest CT after blunt trauma.
| Materials and Methods | | |
This retrospective study protocol was approved by our institutional review board, and examinations were conducted according to the standards of Good Clinical Practice and the Helsinki Declaration.
We retrospectively investigated all blunt chest trauma patients who were admitted between January 2004 and December 2010. The inclusion criteria were that a patient (1) had a chest CT examination on arrival, (2) that intrathoracic traumatic lesions were confirmed by initial CT and (3) that a second chest CT examination was performed within 7 days from admission.
We divided the subjects into two groups. The GG group included subjects who had ground glass appearance lesions on initial chest CT and the control group included subjects who did not have ground glass appearance lesions on initial chest CT. The patients' age, sex, physiological data on arrival (blood pressure, heart rate), the abbreviated injury scale (AIS) of the thorax, [7] the sum of the extrathoracic AIS (head, face, abdomen, extremities and external), injury severity score, [7] results of arterial blood-gas analysis, initial CT findings concerning intrathoracic traumatic lesions (lung contusion, pneumothorax, hemothorax), treatment for intrathoracic traumatic lesions, changes in the pattern between initial and second chest CT, comparison of the value of SpO 2 /FiO 2 between on arrival and the second hospital day, the duration of admission and the survival rate were investigated between the two groups.
Nasal cannula oxygen FiO 2 estimation is calculated as follows: each additional increase of oxygen flow per minute increases the FiO 2 levels by about 4%. Reservoir mask: each additional increase of oxygen flow per minute increases the FiO 2 levels by 10%. A change in the pattern between the initial and the second chest CT was defined as follows: if intrathoracic lesions decreased in volume, then the changing pattern was considered improvement; if intrathoracic lesions increased, then the changing pattern was considered deterioration; if intrathoracic lesions did not change, then patients were considered to have no change; if both improvement and deterioration coexisted, then the pattern was defined as mixed.
We performed a subgroup analysis of the GG group by further dividing these subjects into two groups. The improvement group consisted of subjects whose ground glass lesions decreased or subsided on the second chest CT. The deterioration group consisted of subjects whose ground glass lesions increased or did not change. The relationship between age, sex, physiological data on arrival, injury severity score, distribution of ground glass lesions (dorsal or other), treatment, comparison of the value of SpO 2 /FiO 2 between on arrival and the second hospital day, duration of admission and survival rate were investigated between the two groups.
The s statistical analysis was performed using Student's unpaired t-test, contingency table analyses and the χ2 test. Differences with values of P<0.05 were considered to be statistically significant.
| Results | | |
There were 1397 traumatized patients who were admitted during the investigation period. Of these, there were 328 patients who had intrathoracic traumatic lesions confirmed by CT on arrival. Of these, there were 101 cases who underwent a second CT examination within 7 days from admission, and these subjects were enrolled in the present study. Among these subjects, there were 45 subjects in the GG group and 56 in the control group.
[Table 1] shows the background of all subjects. There were no significant differences between the two groups with regard to sex, physiological data, the sum of the extrathoracic AIS, ISS, the results of an arterial blood-gas analysis, type of traumatic lung injuries on arrival and treatment. There were no subjects who underwent CT examination after a blood transfusion. The average age in the GG group was significantly lower and the thoracic AIS was larger than that in the control group.
[Table 2] shows the changes in the pattern comparison between on arrival and the second chest CT, the differences in the values of the SpO 2 /FiO 2 between on arrival and the second hospital day and outcome. There were no significant differences based on the hospital day when the second CT examination was performed, duration of admission and survival rate of all patients. One death in the GG group was caused by brain death due to severe head injury, and the deaths in the control group were caused by brain death due to severe head injury and multiple organ failure due to multiple injuries, respectively. The percentage of patients with an improvement, no change, deterioration and mixed changes on CT examination in the GG group were 57%, 0%, 33% and 10%, respectively, while those in the control group were 24%, 10%, 56% and 10%. These differences between the two groups were statistically significant. Concerning the differences in the values of the SpO 2 /FiO 2 between on arrival and the second hospital day, the average value of the second day in both groups revealed a decrease in the ratio; however, the ratio of improvement (the value of the second hospital day was better than that on arrival) in the GG group was significantly higher than that in the control group. | Table 2: Changes in the pattern of traumatic lung lesions on computed tomography in SpO2/FiO2 between on arrival and the second hospital day and outcome
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[Table 3] shows the results of the subgroup analysis. Three subjects with representative signs of improvement are shown in [Figure 1], [Figure 2] and [Figure 3], and a typical case of a subject with deterioration is shown in [Figure 4]. There were no significant differences between the two groups concerning sex, physiological data on arrival, injury severity score, treatment, ratio of improvement of SpO 2 /FiO 2, duration of admission and survival rate. However, the age in the improvement group was significantly lower than that in the deterioration group. The ratio of the dorsal area in the improvement group was also significantly smaller than that in the deterioration group. | Figure 1: A case of improvement in a patient with ground glass appearance. A 5-year-old male with ground glass appearance in bilateral lungs showed improvement on the second hospital day by room air management
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 | Figure 2: A case of improvement in a patient with the ground glass appearance. A 23-year-old male with ground glass appearance in his right ventral lung showed almost complete subsidence of the appearance on the second hospital day by oxygen therapy
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 | Figure 3: A case of improvement in a patient with ground glass appearance. A 28-year-old female with ground glass appearance in the right lung showed almost complete resolution of the appearance on the second hospital day by room air management
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 | Figure 4: A case of deterioration in a patient with ground glass appearance. A 33-year-old male with ground glass appearance in bilateral lower lungs showed deterioration on the third hospital day after treatment with oxygen therapy and an indwelling chest drainage tube in the left thorax
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| Discussion | | |
This is the first report indicating that a ground glass appearance on chest CT after blunt trauma is not rare (44%), and that the patients with ground glass lesions were younger and tended to have a better improvement in the oxygenation of the blood and CT images in comparison with the patients without such lesions. The limitations of this study are its small sample size and retrospective nature, and this study may also be considered to be somewhat insufficient because of its lack of pathological findings.
In the present study, 32 of the 45 cases (71%) with ground glass lesions showed partial or complete disappearance of the lesions on the second chest CT, which was performed by the seventh hospital day. CT examinations usually reveal complete resolution of pulmonary contusions, without sequlae, within 1-2 weeks after trauma. [1] However, lung edema can subside within 24 h. [8] Given these findings established by previous reports and the current data, it might be concluded that the ground glass lesions that disappeared before the seventh hospital day are likely to be pulmonary edema, rather than contusions. A pathological examination was able to obtain a definite diagnosis. However, most of the ground glass lesions improved soon after injury and, as a result, invasive examinations were not recommended clinically. Accordingly, the ground glass lesions might have also included a small amount of hemorrhaging induced by extremely minor pulmonary contusions.
The average age of patients with ground glass lesions was lesser than that of patients without the lesions. We hypothesized that these pulmonary ground glass lesions were edema induced by a transient malfunction of the blood-gas barrier in the alveoli in addition to peripheral edema around lung contusions. Fu et al. reported that there was a large proportion of very thin interstitial layers (blood-gas barrier) in the capillaries of newborn rabbit lungs in comparison with adult rabbits. [9] The thin layers demonstrated vulnerability to stress failure. [9] The thinner blood-gas barrier in younger patients may contribute to their increased likelihood of developing lung edema due to blunt trauma in comparison with older patients.
The patients with ground glass lesions tended to have greater improvements of oxygenation of their blood and CT images in comparison with the patients without the lesions. When a disturbance of the blood-gas barrier by blunt trauma leads to the formation of lung edema, rapid remodeling of the capillary wall will occur due to rapid changes in the expression of extracellular matrix proteins and growth factors in response to increased wall stress. [10],[11] Accordingly, disturbance of the blood-gas barrier can be repaired immediately and, after the lung edema has subsided, would result in an improvement of oxygenation of the blood and CT image findings.
The ground glass lesions in the dorsal area tended to deteriorate on the chest CT images. One of the causative factors is atelectasis. Atelectasis, the collapse of alveoli, results from alveolar hypoventilation induced when a patient is placed in one position, when periodic sighs are prevented by mechanical ventilation or the cough reflex is prevented due to pain. This complication most commonly involves the posterior segment of the upper lobes and the superior segment of the lower lobes. [12] Another causative factor is deterioration of lung edema. In the supine position, blood flow at the dorsal area increases so that lung edema deteriorates through disturbance of the blood-gas barrier. [13]
The presence of ground glass lesions did not affect the final outcome of patients. Management of respiratory treatment improves outcome, and death due to respiratory failure tends to decrease. [14],[15] We hypothesized that most of the ground glass lesions in our present patients were lung edema based on the transient disturbance of the blood-gas barrier, and ground glass lesions were easily cured. Accordingly, the existence of ground glass lesions did not affect the final outcome of the patients.
The limitations of this study included the fact that the subjects consisted of a variety of patients with different features of ground glass lesions on the chest CT scans (such as range, distribution, attenuation), and these features may have resulted in some differences in the outcomes. In addition, most patients in the present study suffered extrathoracic trauma. Patients presenting with extrathoracic trauma or those receiving massive transfusions tend to be at risk for developing either acute respiratory distress syndrome (ARDS) or acute lung injury (ALI), and this tendency may influence the outcome. In contrast, Miller et al. reported the independent risk factors for ARDS in blunt trauma to include ISS >25, the existence of pulmonary contusion, an age >65 years, hypotension on admission and a 24-h transfusion requirement >10 units. [16] In this study, the average ISS was under 25, the average age was under 65 years and no subjects required a transfusion of over 10 units in either of the two groups. In addition, the average extrathoracic AIS or the rate of transfusion showed no significant difference between the two groups. Moreover, the anatomical severity of chest injury in the GG group was more severe than that in the control group based on the results of thoracic AIS. However, the oxygenation of the blood in the GG group demonstrated a greater improvement than that in the control. Accordingly, the impact of either extrathoracic trauma or transfusion in this study may therefore have been minimized.
| Conclusion | | |
This is the first report to demonstrate that a ground glass appearance on chest CT after blunt trauma is not rare (44%), and that patients with ground glass lesions were younger and tended to have a better improvement in their oxygenation of the blood and CT images in comparison with patients without such lesions.
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Correspondence Address:
Youichi Yanagawa
Department of Traumatology and Critical Care Medicine, National Defense Medical College, 3-2 Namiki Tokorozawa Saitama
Japan
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0974-2700.99693
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3] |
