Pulsus paradoxus. It’s an intimidating term and a sign not to be taken lightly. What is it and how do you detect it? In its simplest form, pulsus paradoxus is defined as a drop in peak systolic blood pressure more than 10 mm Hg during inspiration (York et al., 2018). The paradox refers to the variable strength of the pulse palpated on exam and not the drop in blood pressure (Borlaug, 2019). It seems harmless but what makes this sign so ominous is that it may signal cardiac tamponade, a serious life-threatening complication of pericardial effusion that requires immediate treatment.
Why does pulsus paradoxus occur?
To understand pulsus paradoxus we must first review normal cardiac physiology. During normal inhalation, there is a slight decrease in intrathoracic pressure which promotes an increase in venous return and right-sided atrial and ventricular filling. The filling on the right side of the heart pushes the septum to expand into the left side of the heart, decreasing left-sided filling, stroke volume, and typically systolic blood pressure. Exhalation increases intrathoracic pressure and promotes left-sided atrial and ventricular filling. The normal pattern of breathing usually causes a decrease in peak systolic pressure of less than 10 mm Hg during inhalation. However, in restrictive conditions in which the left side of the heart cannot fill adequately with blood, there is an exaggerated drop in systolic blood pressure during inspiration (York et al., 2018). Borlaug (2019) describes pulsus paradoxus as a “direct result of competition between the right and left sides of the heart for limited space; for the right heart to fill more, the left heart must fill less.” This leads to a decrease in left ventricular diastolic volume, a lower stroke volume, and a decrease in systolic pressure during inspiration.
How to Detect Pulsus Paradoxus (Lippincott Advisor, 2020)
There are several ways to detect and measure pulsus paradoxus. You can use a sphygmomanometer (standard blood pressure cuff), palpate the patient’s radial pulse, or observe the intra-arterial waveform if the patient has an arterial line.
- Using a sphygmomanometer
- Make sure the patient is breathing normally.
- Inflate the blood pressure cuff 10 to 20 mm Hg beyond the peak systolic pressure.
- Then deflate the cuff slowly at a rate of 2 mm Hg/second until you hear the first Korotkoff sound during expiration; note the systolic pressure.
- Continue to deflate the cuff, observing the patient’s respirations. In pulsus paradoxus, the Korotkoff sounds will disappear with inspiration and return with expiration.
- Continue to deflate the cuff until the Korotkoff sounds emerge during both inspiration and expiration; note the systolic pressure.
- Subtract the second systolic reading from the first. A difference of more than 10 mm Hg is abnormal. Peripheral pulses may not be palpable or may disappear completely with a drop in systolic blood pressure greater than 20 mm Hg.
- Palpating the patient’s pulse
- Palpate the patient’s radial pulse over several cycles of slow inspiration and expiration.
- A significant decrease in the strength of the pulse during inspiration may indicate pulsus paradoxus.
- Observe the intra-arterial blood pressure waveform
- For a patient in the intensive care unit with an intra-arterial line, you can assess the waveform. With pulsus paradoxus you will see a decrease in the amplitude of the systolic pressure on inspiration.
Medical Causes (Borlaug, 2019)
There are several medical conditions that can cause pulsus paradoxus.
- Cardiac tamponade occurs when fluid accumulated in the pericardial sac prevents the heart from adequately filling with blood. (Check out our recommended resources below for more information about cardiac tamponade.)
- Cardiac pericarditis
- Right ventricular myocardial infarction
- Restrictive cardiomyopathy
- Asthma and chronic obstructive pulmonary disease (COPD) cause wide fluctuations in intrathoracic pressure (as high as 40 mm Hg) that may result in pulsus paradoxus.
- Obstructive sleep apnea
- Tension pneumothorax
- Pulmonary embolism
- Bilateral pleural effusion
- Hypovolemic shock
- Significant obesity
If the patient exhibits pulsus paradoxus, be sure to obtain a thorough medical history (Lippincott Advisor, 2020):
- Chronic cardiac or pulmonary disease
- Recent trauma or cardiac surgery
- Other signs and symptoms such as cough or chest pain
Your physical assessment should include (Lippincott Advisor, 2020):
- Auscultation for abnormal breath sounds
- Vital signs
- Cardiopulmonary assessment
- Obtain an electrocardiogram and laboratory tests such as cardiac enzymes, coagulation studies, electrolytes, and complete blood count
Important Clinical Considerations
- Irregular heart rhythms and tachycardia can cause variations in pulse amplitude and should be ruled out before a diagnosis of pulsus paradoxus is made (Lippincott Advisor, 2020).
- Patients who are intubated and on positive pressure ventilation will not have the normal drop in intrathoracic pressure during inspiration (York et al., 2019).
- Pulsus paradoxus may not occur in patients with tamponade if the diastolic pressure in one of the ventricles is greater than that of the pericardial space, or if there is an intracardiac shunt or valvular leak (Borlaug, 2019).
- Other conditions that will counteract pulsus paradoxus include severe aortic regurgitation, severe left ventricular hypertrophy, and left ventricular dysfunction (York et al., 2019).
- Pulsus paradoxus may not be detectable in patients who have significant hypovolemia with hypotension (York et al. 2019).
- An echocardiogram may be performed to evaluate cardiac motion and to determine the underlying cause. Prepare the patient and monitor the vital signs closely, checking the degree of paradox. An increase in the degree of paradox may indicate a worsening of cardiac tamponade or potential respiratory arrest in severe COPD (Lippincott Advisor, 2020).