From the Guidelines
To check for a negative phren sign, have the patient sit or stand comfortably and place your hand firmly over the lower ribs at the costal margin, then ask the patient to take a deep breath in and hold it, and apply firm pressure inward and upward under the costal margin, with the absence of pain indicating a negative sign. This clinical test is used to assess for diaphragmatic irritation, which can occur with conditions like subphrenic abscess or inflammation near the diaphragm 1. The test works because deep inspiration causes the diaphragm to descend, and applying pressure under the ribs can compress an inflamed area if present. If no pain occurs with this compression, it suggests the absence of significant inflammation or irritation of the diaphragm or adjacent structures.
The negative phren sign is particularly useful when evaluating patients with upper abdominal pain or suspected subdiaphragmatic pathology. The procedure for checking the negative phren sign is straightforward and does not require specialized equipment, making it a practical tool for clinicians. However, it's essential to consider the patient's overall clinical presentation and medical history when interpreting the results of this test.
Some key points to consider when performing the negative phren sign test include:
- The patient should be sitting or standing comfortably to minimize any discomfort or anxiety that could affect the test results.
- The clinician should apply firm pressure inward and upward under the costal margin to ensure that the test is performed correctly.
- The absence of pain during the test indicates a negative sign, while the presence of pain suggests a positive sign and potential diaphragmatic irritation.
- The test should be performed in conjunction with other clinical assessments and diagnostic tests to confirm the presence of diaphragmatic irritation or other conditions.
It's also important to note that the negative phren sign test is not a definitive diagnostic tool, but rather a useful clinical test that can help guide further evaluation and management of patients with suspected diaphragmatic irritation or other conditions 1.
From the Research
Checking for Negative Phrenic Sign
To check for a negative phrenic sign, a physical examination of the chest is necessary. The following steps can be taken:
- Inspection: visually examining the chest for any abnormalities or asymmetries 2
- Palpation: using the hands to feel the chest and assess for any tenderness or masses 2
- Percussion: tapping on the chest to assess for any abnormalities in sound 2
- Auscultation: listening to the sounds of the chest with a stethoscope to assess for any abnormalities in breathing sounds 2
Phrenic Nerve Stimulation
Phrenic nerve stimulation can be used to assess the function of the diaphragm. This can be done non-invasively using surface electrodes 3 or invasively using electrodes inserted into the phrenic nerve. The stimulation parameters and electrode positions can be varied to optimize the response of the diaphragm 3.
Physical Examination Techniques
The physical examination of the chest should be conducted in a systematic and thorough manner, using a combination of inspection, palpation, percussion, and auscultation 4, 2. This can help to identify any abnormalities or signs of respiratory disease, including a negative phrenic sign.
Normative Data for Phrenic Nerve Conduction Studies
Normative data for phrenic nerve conduction studies can be used to compare the results of a patient's study to a normal range 5. This can help to identify any abnormalities in the function of the phrenic nerve or diaphragm. The normative limits for M-wave latency, amplitude, and area can be used to assess the results of a phrenic nerve conduction study 5.