In my daily work, the answer is clear. It’s knife. Maybe needle decompression while waiting for the knife. Last week I was attending a conference in Mountain Medicine, and we discussed the issue. One big difference on the mountain or other similar setting, is that you don’t have a lot of fancy equipment. So if your patient is alive, he is breathing spontaneously.
There’s no positive pressure ventilation. You haven’t got that option. That means a tension pneumothorax will take longer to build up, and that venting out even a little bit of the trapped air will help the patient for some time. This would be a setting where I might go for a needle instead of a knife.
And usually in a setting with a lot of noise around you, a patient fully clothed to protect from the wind and weather and no fancy diagnostic tools, your decision to relieve a possible tension pneumothorax will be based on very limited clinical information. Definitely a setting where I would go for a needle instead of a knife. I wouldn’t want to slash open the chest of someone in the middle of the mountain without even a clear diagnosis.
Is needle decompression effective?
So, how effective is needle decompression in spontaneously breathing patients with a tension pneumothorax? According to this US Army study done on our friends – the pigs – quite effective. No difference compared to a proper thoracostomy with a drain. And clearly more effective than doing nothing. All the untreated pigs died quickly.
The tension pneumothorax was induced by continuously pumping air into the pleural cavity at 3 ml/kg/min of the anaesthetised but spontaneously breathing pigs. The influx of air continued throughout the study, also after the needle or drain was in place. The needle or drain was left in situ during the study. And all needles allowed flows of over 3 L/min, so more than adequate for releaving this pneumothorax. Apart from 2 pigs in the Cook Needle Thoracostomy group, all treated pigs survived the 4 hour observation period. So 100% survival in both the standard iv catheter needle decompression group and, not surprisingly, the chest tube group.
Where did they get the insufflattion rate from? I don’t know. Does the insufflation rate accurately simulate a tension pneumothorax build-up in a spontaneously breathing patient/pig? Hard to say, but it sounds reasonable. It provided a slowish buildup of pressure, that took little relief to reverse. And I did like the measurements in this article. Graphs of how CVP, Sats, mean intrathoracic pressure and midline shift (amongst others). It’s interesting to see how the numbers progress during a tension pneumothorax, when it’s unrelived and when it’s treated. Keep in mind that the numbers on the x-axis start at zero with the intervention. 5 minutes elapse from baseline before they start insufflating air, then another 5 minutes before the intervention is initiated. So point zero is 5 minutes into the developing tension pneumothorax.
The above screenshot shows graphs from the 14G iv cannula (14-NT), the Cook catheter (C-NT), the chest tube (CT) and the untreated control group. Profiles of all groups for central venous pressure (CVP), mean arterial pressure (MAP), mean intrapleural pressure (MIP), heart rate (HR), tidal volume (TV), cardiac output (CO). 5 minutes elapse from baseline before they start insufflating air, then another 5 minutes before the intervention is initiated. So point zero is 5 minutes into the developing tension pneumothorax.
If you do use a needle, make sure it’s long enough. In a remote setting, all you will have available might be an i.v. cannula. Make it reach. I do think the differentiation between ventilated and spontaneously breathing patients is an important point. But this pig study from a calm laboratory is very different from the prehospital setting. As a HEMS doctor, Cliff Reid has a keen interest in what works in a prehospital setting, so go read more on needle decompression in these excellent posts at Resus.me.
The US Army study lives here:
Needle versus tube thoracostomy in a swine model of traumatic tension hemopneumothorax, Prehosp Emerg Care, 2009.