Dear Editor

We thank Dr Chan for his comments relating to the recently published guidelines for the diagnosis and management of spontaneous pneumothorces.[1] Dr Chan raises the contentious issue of estimation of the size of a pneumothorax from a plain chest radiograph. We have attempted to use a variation of the method of Axel based on the largest distance from the chest wall to the pleural line and using the assumption that because volume of the lung and the hemi-thorax are roughly proportional to the cube of their diameters, the volume of pneumothorax can be estimated by measuring an average diameter of the lung and the hemithorax, cubing these diameters and finding the ratios.[2]

As Dr Chan rightly points out this is not an exact science as the lungs have a propensity not to maintain a constant shape when they collapse. CT of thorax, when compared with plain radiograph, gives a more accurate estimate of the volume of the pneumothorax. However, while CT may be the only way to give an exact estimate of pneumothorax volume and pattern of lung collapse, it is not often feasible in the emergency room. The correlation co-efficient between CT and plain radiograph is 0.71, p<_0.01.3 thus="thus" while="while" cxr="cxr" is="is" not="not" as="as" effective="effective" ct="ct" it="it" does="does" still="still" provide="provide" a="a" useful="useful" and="and" reasonably="reasonably" accurate="accurate" estimate="estimate" of="of" pneumothorax="pneumothorax" size="size" in="in" most="most" cases="cases" using="using" the="the" method="method" outlined="outlined" current="current" guidelines.="guidelines." we="we" suggest="suggest" that="that" guideline="guideline" an="an" improvement="improvement" on="on" _1993="_1993" guidelines="guidelines" which="which" tended="tended" to="to" underestimate="underestimate" potentially="potentially" importance="importance" pneumothorax.="pneumothorax." choosing="choosing" distance="distance" _2="_2" cms="cms" above="above" volume="volume" usually="usually" _50="_50" gives="gives" emergency="emergency" room="room" physician="physician" easy="easy" use="use" fairly="fairly" reliable="reliable" adhere="adhere" to.="to." has="has" been="been" shown="shown" secondary="secondary" pneumothoraces="pneumothoraces" this="this" are="are" unlikely="unlikely" respond="respond" simple="simple" aspiration="aspiration" will="will" hopefully="hopefully" guidance="guidance" patients="patients" treat="treat" with="with" intercostals="intercostals" tube="tube" drainage.4="drainage.4" supported="supported" by="by" evidence="evidence" now="now" clear="clear" unambiguous="unambiguous" guideline.="guideline." also="also" hope="hope" suggesting="suggesting" _="_" _2cms="_2cms" depth="depth" should="should" be="be" aspirated="aspirated" may="may" reduce="reduce" number="number" needle="needle" injuries="injuries" lung="lung" parenchyma="parenchyma" would="would" have="have" much="much" greater="greater" approximation="approximation" chest="chest" wall="wall" primary="primary" spontaneous="spontaneous" cm="cm" depth.="depth." p="p"/> As Dr Chan points out the American College of Chest Physicians have suggested a different arbitrary system for estimating pneumothorax size suggesting that ‘small’ pneumothoraces were defined by distances <3 cms from apex to cupula of lung and ‘large’ pneumothoraces had distances > 3cms.[5] This seems to have been arbitrarily defined and we are not provided with evidence to support these measurements. Several authors have suggested different distances ranging from 1-4 cms on plain radiograph or more complex equations depending on distances from the pleural line to chest wall at three separate distances or even routine use of CT incorporating even more complex mathematics.[6,7] Dr Chan comments on the lack of evidence regarding CXR classification – we have completed an analysis of the CXR appearances in spontaneous pneumothorax, relating them to the various guidelines, and submitted it as an abstract for the winter meeting of the British Thoracic Society. Bearing in mind that the guidelines are primarily prepared for use by relatively inexperienced and non-specialist junior medical staff, who often have to make management decisions in the middle of the night, we would suggest that the BTS guidelines have combined a fairly robust and accurate scientific approach with an easy to interpret and implement guideline to estimate and treat spontaneous pneumothoraces. Finally, we would again take the opportunity to stress that no matter what the size of a pneumothorax, the decision as to what constitutes appropriate treatment depends not just on the size of a pneumothorax on a chest radiograph, but more importantly, on the clinical status of the patient.

References

(1) Henry M, Arnold T, Harvey J. BTS guidelines for the management of spontaneous pneumothorax. Thorax 2003; 58(Suppl 11):ii39-52.

(2) Axel L. A simple way to estimate the size of pneumothoraces. Invest Radiol 1981;105:1147-1150.

(3) Engdahl O, Toft T, Boe J. Chest radiograph - a poor method for determining the size of a pneumothorax. Chest 1993;103:26-29.

(4) Baumann MH, Strange C, Heffner JE, et al. Management of spontaneous pneumothorax. An American College of Chest Physicians Delphi Consensus Statement. Chest 2001; 119: 590-602.

(5) Archer GJ, Hamilton AAD, Upadhyag R, et al. Results of simple aspiration of pneumothoraces. Br J Dis Chest 1985; 79:177-182.

(6) Collins CD, Lopez A, Mathie A, Wood V, Jackson JE, Roddie ME. Quantification of Pneumothorax size on chest radiographs using intrapleural distances: Regression analysis based on volume measurements from helical CT. Am J Radiol 1995;165:1127-1130.

Dear Editor

The BTS guideline on chest drain management unfortunately fails to recognise the severity of illness of patients who generally require chest drain insertion on an intensive care unit. In our practice chest drainage for pleural effusions only occurs in ventilated patients who require more than 5cm H₂0 PEEP and still have significantly impaired oxygenation limiting their ability to be weaned from ventilation. In this population of patients portable ultrasound guidance is used routinely to reduce the risk of damaging underlying lung but the ventilator is not disconnected as lung recruitment will be lost and hypoxia will rapidly develop.

Dear Editor

I read with interest the latest comprehensive BTS guidelines on chest drain insertion. We would like to share with you some tips and words of caution accumulated by experience from our institute.

During chest drain insertion, we routinely monitor oxygen saturation continuously with or without prior sedation. Patient with secondary pneumothorax i.e. from COAD can deteriorate during chest drain insertion. Furthermore, at the start of the procedure, the nasal oxygen cannula is sited ( but not necessarily turned on) to allow quick delivery of oxygen in an emergency situation. This is particularly true when patients are put in the lateral decubitus position because placing nasal cannula may be more difficult than if the patient is sitting.

In the section on drain removal, as a reminder to junior doctors, it is generally recommended that the suction should be turned off prior to removing the drain because of the theoretical risk of tearing the lung.

Interestingly, there is currently no strong evidence to support removal of chest drains during the Valsalva manoeuvre or expiration; even though the majority of doctors follow this guideline. Physiological understanding suggest that creating a positive intrapleural pressure during chest drain removal may reduce the risk of air entering the pleural cavity. However, study by Bell et al. found no difference in pneumothorax rate whether removal was performed at end inspiration or end expiration.[1] Our experience suggest that important factors influencing post-removal pneumothorax rate are:
(a) speed of chest drain removal to prevent air entering the pleural cavity through the side holes at removal, and
(b) preventing para-drain leakage by digital compression of wound site during removal.

Finally, we have experience of the drain kinking at the point where the tube penetrates the chest wall. The "omental tag of tape" referred by the guidelines can help reduce this occurence. In addition, we found it useful to roll up 2-3 pieces of gauze and place it under (rather than over) the drain right at the point where the tube penetrates the chest wall to bolster the tube and prevent the acute angle it can form with the chest wall, especially with over zealous or tight dressings at that area.

Reference

(1) Bell RL, Ovadia P, Abdullah F, Spector S, Rabinovici R. Chest tube removal: end-inspiration or end-expiration? J Trauma 2001;50:674-7.

Dear Editor

These clinically important papers [1,2] by the Isolde researchers provide excellent data questioning the rationale behind inclusion of patients in the large COPD-studies that have been reported in past few years. Selection of patients on the basis of absence of reversibility means ruling out the easiest measurable variable that may correlate with steroid response. When assessing effects of two weeks prednisolone, or the value of reversibility as a determinant of long-term treatment response to inhaled steroids, one should bear in mind that the Isolde population does not represent the typical patient with COPD that primary care physicians encounter in daily practice. In primary care, one finds all degrees of reversibility, both mild, moderate and indeed some severe COPD, some with and some without significant response. Although highly relevant, the results of the two Isolde papers represent only moderate to severe COPD in absence of reversibility. Therefore, Gross is very right in his editorial to state that we should be openminded about the future; the COOPT-Study which is currently conducted in the Netherlands (Europe) consciously dismissed reversibility as an entry criterion and recruited its population in primary care.[3] Similar to Isolde we performed the two weeks' pretreatment with prednisolone before randomisation and will look at reversibility as a determinant for inhaled steroid response. Results will be available next year, and then we can finally widen our focus to include the field of primary care as well. Don't worry about the fat lady; she will be back.

References

(1) Burge PS, Calverley PMA, Jones PW, et al. Prednisolone response in patients with chronic obstructive pulmonary disease: results from the ISOLDE study. Thorax 2003;58:654–8.

(2) Calverley PMA, Burge PS, Spencer A, et al. Bronchodilator reversibility testing in chronic obstructive pulmonary disease. Thorax 2003;58:659–64.

(3) Chavannes NH, Schermer TRJ, Wouters EF, Van Weel C, Van Schayck CP. Treatment of COPD in general practice: the COOPT study. Eur Respir J 2001;18(Suppl 33):348S.