Use PEEP for treating capnothorax.

Sir,

We have gone through the interesting article, “Fast track management of pneumothorax in laparoscopic surgery” by Dr. R. Raveendran and colleagues[1] We would like to share our views in this connection.

When the anaesthesiologist detected no air entry on the left side of the chest, percussion of the chest would have helped in diagnosing pneumothorax. We think that the anaesthesiologist should not skip their clinical skills, even though monitors are useful.

The authors have increased the rate of ventilation to treat hypercapnia. We think that addition of positive end-expiratory pressure (PEEP) would have helped[23] not only to expand the lung but also to reduce entry of CO2 in the pleural cavity by reducing the pressure gradient across the diaphragm during inspiration and expiration. Re-expansion of the lung with PEEP might also mechanically seal the surgically induced tear in the parietal pleura, if present. PEEP would reduce the need for hyperventilation as entry and absorption of CO2 in the pleural cavity is reduced. Hyperventilation may be disturbing for the surgeon during surgery. Intraoperative PEEP would have expanded the lung fully during 2 h, leaving no or minimal capnothorax postoperatively.

Reduction in insufflation pressure reduced the peak inspiratory pressure, which was maintained during surgery. This was a clue that it was a capnothorax and not a pneumothorax due to rupture of the alveoli, in which PEEP is not advisable. PEEP in the presence of capnothorax helps to prevent increase intrapleural pressure by reducing CO2 entry intrapleurally.

If one can monitor the pressure volume loop on the ventilator, it can help to adjust the amount of PEEP needed.[3]

When capnothorax develops during laparoscopy, treatment with PEEP is an alternative to thoracocentesis. It was surprising why the I.V. canula was put in the chest when the patient was stable. Was it just for fast tracking ? When a pneumothorax is caused by highly diffusible gas such as N2O or CO2 without associated pulmonary trauma, spontaneous resolution of the pneumothorax occurs within 30–60 min without thoracocentesis.[2] Putting a needle in the pleural cavity has its own hazards, like risk of infection, vagal stimulation, etc. PEEP is a noninvasive treatment and is effective for the treatment of capnothorax and its pathophysiological consequences.

The surgeon could have looked at movement of the left diaphragm and could have given a clue about diagnosis and severity of pneumothorax when he looked for evidence of injury to the diaphragm.

Some of the anaesthesia ventilators have got the facility for monitoring respiratory mechanics. Sudden reduction in compliance, rise in peak inspiratory pressure, shift of pressure volume loop towards pressure axis along with rise in ETCO2 helps in diagnosing capnothorax early.

The patient did not have desaturation or hypotension because there was no tension pneumothorax as the intra abdominal pressure (IAP) was reduced from 15 to 12 mmHg and the patient was ventilated with air supplemented with oxygen. Moderate hyperventilation and oxygen supplementation suffices in these patients.[3]

This patient did not show signs of desaturation. Dr. Raveendran could get a clue because the airway pressure and ETCO2 were monitored. Many anaesthesiologists are managing patients by using only pulse oximeter. This case once again emphasizes the need to improve monitoring during laparoscopy for early detection and treatment of complications.

Embryonic remnants constitute potential channels of communication between the peritoneal cavity and the pleural and pericardial sacs, which can open when the intraperitoneal pressure increases. Opening of peritoneopleural ducts is associated with, mainly, right-sided pneumothoraces. The pneumothorax on the left side may be associated with parietal pleural damage during laparoscopic urological surgery.[4] The anaesthesiologist should be aware of this fact.