What Is Diaphragm Flutter

Diaphragm flutter (DF) is a continuous, non-forced high-frequency (>50 Hz) oscillation of the diaphragm that usually occurs during tidal volume breathing in mechanically ventilated patients.

Normally the diaphragm contracts once for each inspiration, with a pattern of electrical and contractile activity that creates a brief sustained contraction with a regular rhythm and force of muscular activity. DF is a dysfunctional form of diaphragmatic contraction involving a series of repetitive electrical impulses leading to a series of oscillations of the diaphragm during inspiration.

Although DF has been described by pulmonary physicians, neurologists, and physiologists for more than 50 years, it has been a poorly understood phenomenon. The condition was considered benign until the middle of the 1990s when 3 reports surfaced describing 11 patients in whom DF was linked to ventilator-associated pneumonia (VAP) and mortality rates > 50% [2-4]. Numerous reports since have confirmed the link between DF, pulmonary complications (pneumonia, atelectasis, pulmonary infiltrates), and prolonged mechanical ventilation.

DF is caused by mechanical forces that can interfere with the normal phasic respiratory activity of the diaphragm as well as by factors that promote the formation of focal seizure activity within the central and/or peripheral nervous systems [1,5,6]. The majority of cases of DF are encountered in mechanically ventilated patients; most cases in non-ventilated patients are associated with metabolic encephalopathy (eg, sepsis) or drug effects (eg, use of sedatives, narcotics).

Clinical Findings:

- DF is characterized by rhythmic, high-pitched expiratory wheezes originating over the anterolateral thoracic wall bilaterally.

- The wheezing may be masked by airway or endotracheal tube secretions.

- An end-expiratory pause with abrupt onset can be seen on the ventilator waveform that is temporally related to the wheezing.

- Paradoxical motion of the abdomen without associated chest excursions can also been seen.

DF is commonly recognized after the endotracheal tube is clamped off or extubated. However, it may be identified only retrospectively from tracings of ventilator graphics after extubation because these wheezes frequently resolve once the patient regains spontaneous respiratory effort without ventilator assistance.

Epidemiology:

- Up to 10% of patients receiving prolonged mechanical ventilation develop DF.

- The incidence of DF increases to almost 40% in patients who are >3-4 weeks postoperatively or receive high doses of sedatives.

- DF is more common in patients with preexisting lung disease.

- DF frequently coincides with the initiation of enteral nutrition.

Diagnosis:

The diagnosis is based on:

- History

- Physical examination

- Ventilator graphics

Other tests sometimes performed include:

- Nerve conduction studies

- Magnetic resonance imaging (MRI)

- Electromyography (EMG) of the diaphragm

- Bronchoscopy

Treatment:

Mechanical ventilation strategies (noninvasive ventilation, volume control, pressure support)

Reduction or adjustment of sedative, narcotic, and paralytic agents when possible

Noninvasive airway vibration/oscillations

Chest physiotherapy

Diazepam/lorazepam if DF persists (not in the presence of hepatic encephalopathy)

Continuous positive airway pressure

Neuromuscular blocking agents

Phrenic nerve paralysis/block

Extracorporeal membrane oxygenation