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Published on: February 14, 2021
Breathing cardiovascular variability and baroreflex in mechanically ventilated patients
Andry Van de Louw1, Claire Médigue, Yves Papelier
1Unité de Biologie Intégrative des Adaptations à l'Exercise (INSERM 902/EA 3872, Genopole), ZAC du Bras de Fer, Evry, France. andry.vandelouw@ch-sud-francilien.fr
Summary
Mechanical ventilation alters heart rate and blood pressure variability patterns. Positive pressure ventilation primarily impacts blood pressure mechanically, while its effect on heart rate variability suggests complex neural influences.
Area of Science:
- Cardiovascular Physiology
- Respiratory Mechanics
- Autonomic Nervous System Function
Background:
- During spontaneous breathing, heart rate and blood pressure variability are linked to negative inspiratory airway pressure.
- Mechanical ventilation employs positive inspiratory airway pressure, potentially reversing normal baroreflex-mediated variability patterns.
Purpose of the Study:
- To investigate heart rate (HR) and blood pressure (BP) variability and baroreflex sensitivity in mechanically ventilated patients.
- To determine the influence of positive pressure ventilation on cardiovascular variability and baroreflex function.
Main Methods:
- Recorded ECG (RR intervals), invasive systolic blood pressure (SBP), and respiratory flow signals in 17 mechanically ventilated patients.
- Utilized Complex Demodulation (CDM) for high-frequency (HF) amplitude and phase difference analysis between cardiovascular and ventilatory signals.
- Employed cross-spectral analysis to assess coherence and gain functions between RR and SBP for baroreflex sensitivity indices.
Main Results:
- Systolic blood pressure (SBP) variability showed an inverted pattern during positive pressure ventilation compared to negative pressure breathing.
- In 12 patients, RR-ventilatory phase differences varied, and HF-RR amplitude fluctuated, with lower RR-SBP spectral coherence.
- In 5 patients, RR-ventilatory phase and HF-RR amplitude were stable, but only one mimicked normal respiratory sinus arrhythmia.
Conclusions:
- Positive pressure ventilation exerts a predominantly mechanical effect on SBP variability.
- The influence of mechanical ventilation on HR variability is complex, indicating potential neural contributions.
- Altered cardiovascular variability patterns during mechanical ventilation may reflect changes in baroreflex sensitivity and autonomic control.
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Critical Guidelines for Assessing Ventilation:
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Respiratory depth measures the volume of air inhaled or exhaled during a breath. It can vary from shallow to deep and typically remains consistent when a person is at rest or asleep. Occasionally, individuals will automatically inhale deeply, known as sighing, which inflates the lungs with more air than normal breathing.
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Respiratory depth measures the volume of air inhaled or exhaled during a breath. It can vary from shallow to deep and typically remains consistent when a person is at rest or asleep. Occasionally, individuals will automatically inhale deeply, known as sighing, which inflates the lungs with more air than normal breathing.
To assess respiratory depth, observe the degree of chest excursion or movement: