A study on clinical and arterial blood gas parameters before and after tube thoracostomy among cases of primary and secondary spontaneous pneumothorax

Introduction

Pneumothorax is defined as the presence of air in the pleural space. If air is present in the pleural space,1 one of three events must have occurred: 1) communication between alveolar spaces and pleura; 2) direct or indirect communication between the atmosphere and the pleural space; or 3) presence of gas-producing organisms in the pleural space. From a clinical standpoint, pneumothorax is classified as spontaneous (no obvious precipitating factor present) and traumatic. Primary spontaneous pneumothorax (PSP) is defined as the spontaneously occurring presence of air in the pleural space in patients without clinically apparent underlying lung disease. In secondary spontaneous pneumothorax (SSP) there is an underlying lung pathology that gives rise to the pneumothorax. Emphysema, Bbullous lung disease, cystic fibrosis, idiopathic pulmonary fibrosis, lymphangiomyomatosis are some important pathologies that are associated with SSP. 2, 3

Pneumothorax induces various clinical presentation in patient as well as changes in blood gas. A ball valve mechanism may give rise to tension pneumothorax which leads to circulatory and respiratory compromise. With prolonged collapse, the lung becomes vulnerable to infection, as does the pleura cavity when communication between it and the lung persists. 4

Clinical manifestation of pneumothorax includes chest pain, shortness of breath, signs include tachycardia, tachypnoea, and hypoxia. Blood gas study can reveal decreased partial pressure of oxygen in arterial blood (PaO2), and changes in alveolar-arterial oxygen gradient (AaDO2). 5

Pneumothorax is a respiratory emergency that requires active intervention, various treatment modalities are available for management of pneumothorax. Tube thoracostomy being one of the most commonly used intervention.

The changes that occur post tube thoracostomy in patients with primary and secondary spontaneous pneumothorax, over different time interval, are not well studied.

In our study we intend to study the effect on tube thoracostomy on clinical and arterial blood gas parameters in primary and secondary spontaneous pneumothorax.

Material and Methods

Quantification of pneumothorax

Volume of pneumothorax was determined using the Collins formula from the chest X-ray. Collins et al. 6 have described an alternate method for estimating the percentage of collapse. With their method, the distance between the apex of the partially collapsed lung and the apex of the thoracic cavity (distance A), and the midpoints of the upper (distance B) and lower (distance C) halves of the collapsed lung and the lateral chest wall were measured in centimetres. They found that the percentage pneumothorax size could be calculated by the formula (Figure 1).

% of Pneumothorax= 4.2+4.7(A+B+C)Figure 1

Figure 1

Measuring the volume of pneumothorax.

Arterial blood gas analysis (ABG)

Arterial blood gas analysis was performed before giving chest drain, 1hour and 24 hours after chest drain, and after removal of chest tube after complete expansion of lungs.

Radial artery sampling was done for ABG analysis. The drawn samples are preferably bubble free, it’s processed immediately using EPOC blood gas analyzer available at Department. Supplemental oxygen was given only to those patients who were hypoxic at presentation and those with tension pneumothorax. During subsequent ABG patients were kept at least 20 minutes in room air before drawing blood samples.

Intercostal tube drainage (ICD)

Intercostal tube drainage was done in all patients included in the study as a definitive management of pneumothorax.

Removal of the chest drain

We have removed chest drain when the lung showed complete expansion both clinically and radiologically, bag collection <50 ml/day for 3 consecutive days, minimal or physiological swing.

Result analysis: The data were tabulated using Microsoft Excel software and analysed using following software.

1. Statistica version 6 [Tulsa, Oklahoma: StatSoft Inc., 2001]

2. GraphPad Prism version 5 [San Diego, California: GraphPad Software Inc., 2007]

3. Null hypothesis were:

   1. There is no change in clinical parameters before and after tube thoracostomy among cases of PSP and SSP.

   2. There is no change in ABG parameters before and after tube thoracostomy among cases of PSP and SSP.

Results

We had initially taken 37 cases of primary and secondary spontaneous pneumothorax who were planned for tube thoracostomy. Among them 30 cases were successfully treated with tube thoracostomy only, 7 patient required other modalities of managements apart from tube thoracostomy like decortication surgery. Finally 30 cases (n=30) cases of primary and secondary spontaneous pneumothorax were included in the study who had undergone tube thoracostomy as the only modality of treatment.

The results were: Out of 30 cases 11 cases were primary pneumothorax (36.67%) and 19 cases were of secondary pneumothorax (63.33%). Among 11 cases of primary spontaneous pneumothorax 10 cases were male, 1 case was female, among 19 cases of secondary spontaneous pneumothorax 18 cases were male, 2 cases were female. In our study most number of cases of primary spontaneous pneumothorax belongs to younger age group (15-45 years), whereas most number of cases in SSP group (73.68%) belongs to older age group (46-76 years) (P<0.001). In primary group 72.7% cases were smoker, in secondary group 84.21% cases were smoker. Both groups do not show any significant difference in smoking status. In Secondary pneumothorax group average pack year is 27.17, in primary group it is 9.22 (P=0.002, Chi Square test of Proportion).

Among secondary pneumothorax cases 14 cases had COPD (73.68%), among these cases 4 patients also had past history of pulmonary tuberculosis (31.57)%, 1 patient had granulomatosis with polyangitis (GPA). 1 patient had active Pulmonary Tuberculosis. Multiple aetiological condition was present in same patient. Using Collins formula the mean volume of pneumothorax in primary group is 70.6% (standard deviation (SD) 22.55), and in secondary group it is 60.8 (SD 22.21).

The average duration of intercostal tube drainage in primary group is 9.72 (SD 4.14), in secondary pneumothorax group the average duration is 14.21 (SD 9.94).

Discussion

Our study was a descriptive observational study carried over a period of one year. Patients of Primary and secondary spontaneous pneumothorax requiring tube thoracostomy as management were included in the study. Main objective of our study was to find out the clinical and arterial blood gas parameter changes before and after tube thoracostomy at different time interval, among cases of primary and secondary spontaneous pneumothorax.

In our study population most cases are male (93.33%). Men are more prone to sustain a pneumothorax than women. Studies conducted in USA has shown a male female ratio of 3:1. 7 Higher incidence of spontaneous pneumothorax in men has been attributed to several factors such as higher rates of smoking, 8, 9 taller body habitus,4 and differences in mechanical properties of the lung.10

Primary spontaneous pneumothorax occurs mostly in young patients, (72.3% within 4^th decade of life) SSP in older age group. (73.8% beyond 4^th decade of life) (P=0.001). Literature review has shown most of the cases of PSP occurs in 2^nd and 3^rd decade of life. Roman et al. has found primary spontaneous pneumothorax to occur commonly in young adults. 11, 12

In a study from Scotland 90% of patients with pneumothorax under the age of 35 had no previous history of lung disease while 80% of patients over the age of 50 years had pre-existing lung disease.13 Studies that have focused strictly on primary spontaneous pneumothorax, excluding all other forms of pneumothoraxes, have shown a monophasic age distribution with the peak falling in the 15–35 year age.14, 15

Smoking is a common predisposing factor in both groups.16, 17 But in secondary group number of pack year smoked is more compared to primary group. In our study average pack year in PSP 9.22, in SSP 27.17. This difference is statistically significant (P=0.002). Jansveld et al. has shown smoking as an important risk factor for PSP.18

Change in respiratory rate was found to be earliest among both PSP and SSP group. Significant changes were observed within 1 hour of tube thoracostomy. In SSP group similar early changes were observed in pulse rate and diastolic blood pressure also.

In PSP group (table 10 a) Pre thoracostomy 54.54% cases presented with hypoxemia, among which 27.27% had mild hypoxemia (pO2 60-80 mm of Hg), 18.18% had moderate hypoxemia (pO2 40-59 mm of Hg), 1 case (9.1%) presented with severe hypoxemia (pO2< 40 mm of Hg). After 1 hour of tube thoracostomy only 18.18% cases had mild hypoxemia, no cases had moderate or severe hypoxemia, After 24 hours 9% cases had mild hypoxemia, at removal 1 among 11 cases(9%) developed moderate hypoxemia, that case had developed respiratory failure post pleurodesis.

In SSP group (table 10 b) before tube thoracostomy 68.42% cases presented with hypoxemia, among which 42.11% had mild hypoxemia, 21.05% cases had moderate hypoxemia, 1 case (5.2%) presented with severe hypoxemia. After 1hr of tube thoracostomy 52.56% cases had hypoxemia, 47.36% had mild hypoxemia and 5.2% (1 case) had moderate hypoxemia, after 24 hr 31.51% had hypoxemia, among which 26.31% had mild hypoxemia and 5.2% had moderate hypoxemia. Similar changes were observed at the time of tube removal.

In a study by Norris et al.19 among 12 patients, the PaO₂ was below 80 mm Hg in 9 patients (75%) and was below 55 mm Hg in 2 patients. Our study also showed similar finding.

In both groups after tube thoracostomy there is improvement in hypoxemia, In PSP group only mild hypoxia persisted after 1 hour of tube thoracostomy. In SSP group only 1 case (5.2%) showed persistent moderate hypoxemia, probably due to underlying lung disease.

Change was observed in SpO2 in PSP group before tube thoracostomy and 24 hours after thoracostomy (P<0.05). In SSP group the changes of SpO2 was significant during all measurements. (P<0.05, P<0.01). In PSP group 3 patients presented with hypoxia, in SSP group 4 patients presented with hypoxia, that was corrected within 24 hours.

The present study did not reveal statistically significant changes regarding alteration of pH, pCO2, and AaDO2 among cases of PSP and SSP pre and post thoracostomy. Causes may be owing to the compensatory mechanisms that operate in case of lung collapse due to pneumothorax. However studies with larger sample size are desirable.

So, considering our initial null hypothesis, we have observed significant changes in clinical parameters (respiratory rate, pulse rate, diastolic blood pressure) before and after tube thoracostomy in both primary and secondary spontaneous pneumothorax cases.

Regarding arterial blood gas values peripheral arterial oxygen saturation showed significant changes before and after tube thoracostomy in both primary and secondary pneumothorax cases.

Tube thoracostomy is considered the treatment of choice in pneumothorax 20, 21, monitoring the patients undergoing tube thoracostomy is an integral part of the management. With availability of multiple parameters and modalities choosing the correct one is important.

So the study shows that cases of primary and secondary pneumothorax requiring tube thoracostomy can be best assessed and monitored by clinical parameters like examination of pulse, respiratory rate, blood pressure and non-invasive parameter like pulse oximetry.

Conclusions

The present study shows that there is serial improvement of vital signs like pulse rate, respiratory rate, diastolic blood pressure and oxygen saturation following tube thoracostomy among cases of both primary and secondary spontaneous pneumothorax. There is decrease in tachypnea, tachycardia post tube thoracostomy and improvement of hypoxia. The study also shows that functional improvement following tube thoracostomy among cases of spontaneous pneumothorax can be better assessed by simple clinical parameters like pulse rate, respiration, blood pressure and pulse oximetry compared to arterial blood gas analysis.

Conflicts of Interests

None declared.

Source of Funding

None.

Acknowledgements

Prof. Avijit Hazra., Department of Pharmacology, SSKM Hospital and IPGME&R.