Respiration is a complex process in which adequate ventilation and perfusion are dependent on pressure gradients of the various components within the system. The normal intrapleural pressure is −3.68 mm Hg (−5 cm H2O).1–4 Conditions that result in an accumulation of air or fluid in the thoracic cavity cause changes to the intrapleural pressure, which results in alterations of respiration. The conditions most commonly encountered in veterinary medicine are pneumothorax, chylothorax, pyothorax, hemo-thorax, and iatrogenic opening of the pleural space for surgical purposes.5–8
It is necessary to reestablish the normal intrapleural pressure to regain adequate ventilation and perfusion. This can be accomplished by intermittent thoracentesis, intermittent evacuation via a thoracostomy tube, or application of continuous suction within the pleural space. The recommended applied pressure for continuous suction systems is −3.68 to −18.39 mm Hg (−5 to −25 cm H2O).2,3,7 Although there are limited data to confirm the desired negative pressure applied for continuous suction, it was reported in 1 study9 that physicians typically use −14.71 mm Hg (-20 cm H2O) as the standard in practice.
Use of an intrapleural pressure lower than −14.71 mm Hg (−20 cm H2O) in humans results in an increase in chest discomfort and a possible increase in complications.10–13 A rare but possibly fatal complication of increased intrapleural negative pressure in humans is reexpansion pulmonary edema.14,15 The incidence of reexpansion pulmonary edema is reportedly between 0.5% and 14%16–20 with a mortality rate of up to 20%.14,17 Clinical signs associated with reexpansion pulmonary edema include cough, thoracic pain, dyspnea, foaming sputum, agitation, tachycardia, and tachypnea. If any of these clinical signs are noted, application of negative pressure should be discontinued and the patient evaluated further.14–16,19,20 Limiting the amount of negative pressure applied to the pleural cavity can reduce the risk of these complications.
No specific data have been provided regarding the recommended amount of pressure generated during intermittent evacuation of the thoracic cavity. It has been suggested that 5 to 10 mL of negative suction volume should be applied with a syringe during evacuation7,8; however, the amount of negative pressure generated with this negative suction volume has not been determined.
To the authors’ knowledge, no studies have been conducted to determine the amount of pressure generated during intermittent evacuation of the thoracic cavity via a thoracostomy tube. The purposes of the study reported here were to determine the negative pressure generated by syringes of various sizes with and without an attached thoracostomy tube and to determine whether the composition of the thoracostomy tube would alter the negative pressure generated. We hypothesized that there would be no difference in the negative pressure generated by syringes of various sizes for a fixed negative suction volume, that the addition of a thoracostomy tube would decrease the negative pressure generated, and that the composition of the thoracostomy tubes would affect the negative pressure generated.
No third-party funding or support was received in connection with this study or the writing or publication of the man uscript. The authors declare that there were no conflicts of interest.
The authors thank Gary Clark for assistance with the statistical analysis.
Monoject syringes, Covidien, Mansfield, Mass.
DPM1B pneumatic transducer, Fluke Biomedical, Everett, Wash.
Feeding tube and urethral catheter, Covidien, Mansfield, Mass.
3-way stopcock, Braun, Bethlehem, Pa.
Surgivet female Luer lock to tapered catheter, Smiths Medical ASD Inc, Saint Paul, Minn.
Surgivet 12F thoracic drainage catheter, Smiths Medical ASD Inc, Saint Paul, Minn.
12F silicone chest tube, Mila, Florence, Ky.
Jorvet 12F silicone chest drainage tube, Jorgensen Labs, Loveland, Colo.
Stata/IC, version 14.2, StataCorp LLC, College Station, Tex.
1. Blom JA. Anatomy and physiology of the lung and airways. In: Blom JA. Monitoring of respiration and circulation. Boca Raton, Fla: CRC Press Inc, 2004;3–23.
2. Randlinsky MG. Thoracic cavity. In: Tobias KM, Johnston SJ, eds. Veterinary surgery small animal. Vol 2. St Louis: Elsevier Saunders, 2012;1787–1812.
3. Rozanski EA, Mooney E. Pneumothorax. In: Bonagura JD, Twedt DC, eds. Kirk's current veterinary therapy. 15th ed. St Louis: Elsevier Saunders, 2014;700–704.
4. West JB. Mechanics of breathing. In: West JB. Respiratory physiology: the essentials. 9th ed. Baltimore: Lippincott Williams & Wilkins, 2012;95–124.
7. Sigrist NE. Thoracostomy tube placement and drainage. In: Silverstein D, Hopper K, eds. Small animal critical care medicine. 2nd ed. St Louis: Elsevier Saunders, 2014;1032–1035.
10. Zielinska-Krawczyk M, Krenke R, Grabczak EM, et al. Pleural manometry—historical background, rationale for use and methods of measurement. Respir Med 2018;136:21–28.
11. Grabczak EM, Krenke R, Zielinska-Krawczyk M, et al. Pleural manometry in patients with pleural diseases—the usefulness in clinical practice. Respir Med 2018;145:230–236.
12. Pannu J, DePew ZS, Mullon JJ, et al. Impact of pleural manometry on the development of chest discomfort during thoracentesis: a symptom-based study. J Bronchology Interv Pulmonol 2014;21:306–313.
13. Feller-Kopman D, Walkey A, Berkowitz D, et al. The relationship of pleural pressure to symptom development during therapeutic thoracentesis. Chest 2006;129:1556–1560.
15. Ziskind MM, Weill H, George RA. Acute pulmonary edema following the treatment of spontaneous pneumothorax with excessive negative intrapleural pressure. Am Rev Respir Dis 1965;92:632–636.
16. Feller-Kopman D, Berkowitz D, Boiselle P, et al. Large-volume thoracentesis and the risk of reexpansion pulmonary edema. Ann Thorac Surg 2007;84:1656–1661.
18. Echevarria C, Twomey D, Dunning J, et al. Does re-expansion pulmonary oedema exist? Interact Cardiovasc Thorac Surg 2008;7:485–489.
21. Knox T, Davie J. Nasogastric tube feeding—which size syringe produces lower pressure and is safest to use? Nurs Times 2009;105:24–26.
23. Blom JA. Physics of fluid transport in tubes. In: Monitoring of respiration and circulation. Boca Raton, Fla: CRC Press Inc, 2004;45–70.
24. Fox RW, McDonald AT, Pritchard PJ. Motion of a fluid particle (kinematics). In: Fox RW, McDonald AT, Pritchard PJ. Introduction to fluid mechanics. 6th ed. Danvers, Mass: John Wiley & Sons Inc, 2004;197–211.