Synergism between the canine left and right hemidiaphragms

Area of Science:

• Respiratory Physiology
• Biomechanics

Background:

• Lung expansion involves coordinated diaphragm and rib cage muscle contraction.
• Previous research suggested additive pressure changes from rib cage muscles.

Purpose of the Study:

• To investigate the interaction between the right and left hemidiaphragms during inspiration.
• To determine if diaphragmatic interactions are additive or synergistic.

Main Methods:

• Anesthetized dogs were used to compare airway opening pressure (DeltaPao) changes.
• Simultaneous phrenic nerve stimulation (measured DeltaPao) was compared to separate stimulation (predicted DeltaPao).
• Radiographic measurements assessed diaphragmatic movement and configuration.

Main Results:

• Measured DeltaPao was consistently greater than predicted DeltaPao.
• This synergistic effect increased with stimulation frequency.
• Diaphragmatic configuration, not load, explained the interaction.

Conclusions:

• The left and right hemidiaphragms exhibit synergistic, not additive, interaction.
• This synergism is present during quiet breathing and amplifies with increased respiratory drive.
• The muscle's configuration is the primary driver of this synergistic interaction.