Plethysmography is a method of assessing a patient’s volume and changes in their tissue oxygenation. A plethysmograph measures the amplitude of blood vessels, applying an external pressure to the tissue and tracking changes in the resulting waveform. It is used in both cardiac and respiration assessments in order to evaluate the patient’s overall health and decrease the risk for complications.

Preparation for Plethysmography

Before a plethysmograph test can be done, the patient will need to be prepared accordingly. Preparation for the test typically includes:

  • Removing any jewelry that could interfere with the test
  • Receiving reconstituted intravenous fluids containing electrolytes
  • Receiving an intravenous injection of contrast dye
  • Receiving oxygen
  • Having all necessary equipment in place for the test

Plethysmography Procedure

The plethysmography procedure involves the following steps:

  • The patient is placed in a reclined position.
  • The patient’s body is covered with a suitable material to prevent heat loss.
  • The patient’s breathing is monitored using a respiratory indicator.
  • The plethysmograph is connected to the patient’s abdomen and the artery in the arm.
  • The patient’s pulse is monitored on a monitor.
  • The plethysmograph is calibrated to adjust for any changes in the patient’s weight or movements.
  • The plethysmograph is used to measure the amplitude and rate of change in the patient’s pulse.

Types of Plethysmography

  • Arterial Pulse Pressure Plethysmography: This type of plethysmography measures the pulse pressure in the arterial vessels, and it is used to examine and diagnose coronary artery disease. It is also used to assess the risk of abnormal heart rhythms or arrhythmias.

  • Cardiac Output Plethysmography: This type of plethysmography measures the amount of oxygen in the blood and the amount of blood being pumped from the heart.

  • Respiratory Plethysmography: This type of plethysmography measures the respiratory rate and the volume of air each patient inhales and exhales.

  • Peripheral Artery Plethysmography: This type of plethysmography measures the artery diameter and the flow of blood within the peripheral arteries.

  • Pulse Wave Velocity Plethysmography: This type of plethysmography measures the rate at which a pulse wave moves through the blood vessels and it is used to detect vascular stiffness and assess the risk of hypertension.

Risks of Plethysmography

The risks of plethysmography are minimal, as no invasive procedures are required. However, some patients may experience side effects such as dizziness or nausea during the test due to the constriction of the vessels caused by the plethysmograph. In addition, some patients may experience anxiety during the procedure due to the presence of a medical device connected to their arm.

When or Why to Use Plethysmography?

Plethysmography can be used for the diagnosis and monitoring of a variety of cardiovascular and respiratory conditions. It is used to assess and diagnose coronary artery disease, arrhythmias, peripheral arterial disease, hypertension, and respiratory conditions such as asthma and COPD.

Patients suffering from a variety of cardiovascular and respiratory conditions can benefit from plethysmography. The results of the test can provide physicians with valuable information about the cardiac and respiratory systems that can be used to determine the best course of action for treatment.