Unaffected contractility of diaphragm muscle fibers in humans on mechanical ventilation

Area of Science:

• Physiology
• Muscle Biology
• Critical Care Medicine

Background:

• Diaphragm dysfunction is a known complication in patients requiring mechanical ventilation (MV).
• The impact of MV on the intrinsic contractility of sarcomeres, the fundamental contractile units of muscle, remains incompletely understood in humans.

Purpose of the Study:

• To investigate whether mechanical ventilation affects the contractility of sarcomeres within the human diaphragm.
• To compare diaphragm muscle fiber contractility between patients on prolonged MV and those on short-term MV.

Main Methods:

• Diaphragm muscle fibers were obtained from brain-dead organ donors (26 ± 5 h MV) and surgical patients (<2 h MV).
• Muscle fiber cross-sectional area was assessed using immunohistochemistry.
• Contractile performance of permeabilized single muscle fibers was evaluated, measuring maximum specific force, tension redevelopment rate, myosin heavy chain content, and calcium sensitivity.

Main Results:

• No statistically significant differences were observed in slow-twitch or fast-twitch muscle fiber contractility between the prolonged MV group and the short-term MV control group.
• Key contractile parameters, including maximum specific force and cross-bridge cycling kinetics, remained unchanged.

Conclusions:

• Twenty-six hours of mechanical ventilation in humans is not invariably associated with impaired sarcomere contractility in the diaphragm.
• These findings suggest that the fundamental contractile machinery of the diaphragm may be resilient to short-term mechanical ventilation.