A positive sniff test indicates that imaging results showed your diaphragm was elevated when you inhaled, which can suggest that at least part of your diaphragm is paralyzed. This diagnostic test helps medical professionals assess the movement and function of your diaphragm, the primary muscle responsible for breathing.
Understanding the Sniff Test Results
The sniff test is a fluoroscopic examination, meaning it uses X-rays to create a real-time video of your diaphragm's movement. During the test, you're asked to inhale sharply, or "sniff," while the images are captured.
- Positive Sniff Test: As mentioned, a positive result means that instead of moving downwards as it should during inhalation, your diaphragm moves upwards (elevates) or remains still. This paradoxical motion suggests that the muscle is not contracting effectively, possibly due to a phrenic nerve injury or diaphragm paralysis.
- Normal (Negative) Sniff Test: In contrast, a normal or negative sniff test report demonstrates that your diaphragm is moving appropriately. When you inhale, a healthy diaphragm contracts and moves downward, increasing the volume of your chest cavity and drawing air into your lungs.
Why a Sniff Test is Performed
Medical professionals typically order a sniff test when there is a suspicion of diaphragm dysfunction or paralysis, which can lead to breathing difficulties.
Common reasons for performing a sniff test include:
- Unexplained shortness of breath (dyspnea): Especially when it worsens while lying down (orthopnea).
- Elevated diaphragm seen on a chest X-ray: If routine imaging shows one or both sides of the diaphragm are positioned unusually high.
- Suspected phrenic nerve injury: This nerve controls diaphragm movement. Damage to this nerve can result from surgery, trauma, or certain medical conditions.
- Evaluating diaphragm function before surgery: Particularly for procedures that might affect the diaphragm or the phrenic nerve.
The information obtained from a sniff test is crucial for diagnosing the cause of respiratory issues and guiding appropriate treatment strategies.
