Pulsus paradoxus

Study of Respiratory Variations of Mitral Valve Diastolic Flow in Hemodialysis Patients

The respiratory variations in mitral valve (MV) Doppler flow in hemodialysis (HD) patients have not been investigated and the normal echocardiographic value is used as a reference for HD patients. The present study evaluated the respiratory variation in MV Doppler flow in HD patients to determine if it has a unique pattern. In this prospective cohort study, echocardiography was performed before and 6 h after dialysis. The transmitral spectral Doppler E wave was measured during inspiratory and expiratory phases. The percent changes in the E wave were calculated pre- and post-dialysis. The means of the percent variation in the MV inspiratory and expiratory E wave pre- and post-dialysis were 56 ± 7% and 44 ± 1.1%, respectively, with a significant reduction after dialysis (P = .000). There was a significant positive correlation between post-dialysis ∆E wave % change and post-dialysis % change in weight (r = .318; P = .000). The respiratory changes in the MV E wave in HD patients were higher than the normal reference values. This marked variation could be explained by fluid overloading in HD patients.

Cardiopulmonary interactions-which monitoring tools to use?

Heart-lung interactions occur due to the mechanical influence of intrathoracic pressure and lung volume changes on cardiac and circulatory function. These interactions manifest as respiratory fluctuations in venous, pulmonary, and arterial pressures, potentially affecting stroke volume. In the context of functional hemodynamic monitoring, pulse or stroke volume variation (pulse pressure variation or stroke volume variability) are commonly employed to assess volume or preload responsiveness. However, correct interpretation of these parameters requires a comprehensive understanding of the physiological factors that determine pulse pressure and stroke volume. These factors include pleural pressure, venous return, pulmonary vessel function, lung mechanics, gas exchange, and specific cardiac factors. A comprehensive knowledge of heart-lung physiology is vital to avoid clinical misjudgments, particularly in cases of right ventricular (RV) failure or diastolic dysfunction. Therefore, when selecting monitoring devices or technologies, these factors must be considered. Invasive arterial pressure measurements of variations in breath-to-breath pressure swings are commonly used to monitor heart-lung interactions. Echocardiography or pulmonary artery catheters are valuable tools for differentiating preload responsiveness from right ventricular failure, while changes in diastolic function should be assessed alongside alterations in airway or pleural pressure, which can be approximated by esophageal pressure. In complex clinical scenarios like ARDS, combined forms of shock or right heart failure, additional information on gas exchange and pulmonary mechanics aids in the interpretation of heart-lung interactions. This review aims to describe monitoring techniques that provide clinicians with an integrative understanding of a patient's condition, enabling accurate assessment and patient care.

Usefulness of HVAD Waveforms as Diagnostic Assistance for Cardiac Tamponade

We experienced a 39-year-old male patient who converted paracorporeal left ventricular assist device to HeartWare ventricular assist device (HVAD; Medtronic, Framingham, MA) as bridge-to-transplant indication. On the 10th postoperative day, the HVAD flow waveform presented periodical low pulsatility pattern. Significant pericardial hematoma was observed on the imaging studies, and he showed pulsus paradoxus. He was highly suspected of cardiac tamponade and performed thoracotomy. HVAD waveform might be a useful tool to monitor and early suspect of postoperative cardiac tamponade to consider more intensive examinations and thoracotomy before hemodynamic deterioration, although further large-scale studies are warranted to strengthen our hypothesis.

Respiratory Fluctuation of Peak Systolic Velocities in the Carotid Doppler Waveforms of Patients With Obstructive Airway Disease: Evidence of Pulsus Paradoxus With Experimental Validation

OBJECTIVES

To characterize fluctuations in peak systolic velocities (PSVs) in Doppler waveforms of the carotid artery in patients with and without obstructive airway disease and in volunteers subjected to incremental levels of airway resistance in an experimental model.

METHODS

The PSV variation in common carotid waveforms was measured in 100 patients who had had a carotid ultrasound examination and no respiratory or carotid disease. This was compared to that of patients who had this study during an admission for acute exacerbation of chronic obstructive pulmonary disease (COPD). The PSV variation was correlated with pulmonary function testing. In addition, 14 healthy volunteers were asked to breathe through 5 resistors. Simultaneous recordings were made of Doppler waveforms in the common carotid artery, cardiac activity, and respiration. Peak systolic velocity changes from inspiration to expiration were calculated.

RESULTS

Of the 100 patients without respiratory disease, the magnitude of the PSV variation averaged 6.3 cm/s. Of the 33 patients with COPD, the PSV variation averaged 16.5 cm/s. Nineteen of the 33 patients with COPD had concurrent pulmonary function testing; there was a statistically significant correlation between the PSV variation and forced vital capacity and forced expiratory volume indices. For the volunteers, mean velocity changes were 7.1, 6.6, 8.3, 15.1, and 16.1 cm/s for 0.00-, 2.15-, 3.27-, 3.58-, and 5.77-cm H₂ O/L/s levels of breathing resistance, respectively. There was a statistically significant relationship between an increasing airway load and the decline in PSV during inspiration (P = .02).

CONCLUSIONS

The PSV variation is greater in patients with increased airway resistance. Similar changes are evident in volunteers breathing into resistors. These findings likely reflect pulsus paradoxus.