What is the Mueller maneuver?

What is the Mueller Maneuver

The Mueller maneuver is a maximal inspiratory effort performed against a closed airway (or occluded mouthpiece) that generates negative intrathoracic pressure, used primarily to assess respiratory muscle strength and upper airway collapsibility. 1

Physiological Mechanism

The Mueller maneuver involves contraction of the diaphragm and inspiratory muscles with the goal of creating the largest negative thoracic pressure possible. 1 During this maneuver:

• Mean right atrial pressure decreases dramatically from approximately 7 mm Hg to -17 mm Hg 2
• Left ventricular end-diastolic pressure drops from 12 mm Hg to -3 mm Hg 2
• Systemic vascular resistance and left ventricular peak positive dP/dt increase, while cardiac output and stroke volume decrease 2
• Aortic diastolic pressure decreases while pulse pressure increases, though mean aortic pressure remains relatively unchanged 2

The maneuver was first described by German anatomist and physician Johannes Müller (1801-1858) and represents the physiological opposite of the Valsalva maneuver. 3

Clinical Applications

Respiratory Muscle Testing

The Mueller maneuver is performed at or near residual volume (RV) with subjects seated, using a flanged mouthpiece with a small leak (approximately 2-mm internal diameter, 20-30 mm length) to prevent glottic closure. 1 The test protocol requires:

• Pressure must be maintained for at least 1.5 seconds so that maximum pressure sustained for 1 second can be recorded 1
• The maximum value of three maneuvers that vary by less than 20% should be recorded 1
• An experienced operator must strongly urge subjects to make maximum inspiratory efforts, as careful instruction and encouraged motivation are essential for this unfamiliar maneuver 1

When measured with balloon catheters in the esophagus and stomach, the Mueller maneuver creates negative thoracic pressure but typically does not generate maximum transdiaphragmatic pressure (Pdi). 1 For research purposes requiring maximal Pdi values (up to 240 cm H2O or more), an expulsive maneuver combined with a Mueller maneuver may be necessary, though this is difficult for naive subjects. 1

Sleep Apnea Evaluation

The Mueller maneuver is used during upper airway endoscopy to assess the degree and location of pharyngeal collapse in patients being evaluated for obstructive sleep apnea. 4 The technique involves:

• Rating collapse at three levels (soft palate, lateral pharyngeal wall, and base of tongue) on a five-point scale (0-4) 4
• Despite its subjective nature, independent examiners can achieve reproducible evaluations using this standardized scale 4
• The Mueller maneuver score correlates moderately with apnea-hypopnea index (AHI) severity, matching within ±1 unit 72.1% of the time 4

The maneuver simulates the hemodynamic effects of negative intrathoracic pressure that occur during obstructive apneic events. 3

Imaging Enhancement

In CT pulmonary angiography, a device-assisted Mueller maneuver can prevent transient interruption of contrast (TIC) phenomenon and improve pulmonary artery opacification. 5 Patients using this technique showed:

• Complete absence of TIC phenomenon compared to 12.3% incidence with standard breath-hold commands 5
• Significantly higher pulmonary trunk-to-aortic attenuation ratio (3.86 vs. 2.26) 5
• Better overall contrast enhancement at all vascular levels 5

The trade-off is a higher rate of breathing artifacts (48.1% vs. 30.1%), though these lack clinical consequence. 5

Important Caveats

The Mueller maneuver acutely reduces left atrial filling and left ventricular stroke volume by approximately 10 mL in healthy adults, with corresponding decreases in early diastolic filling velocities and left atrial reservoir strain. 6 These hemodynamic changes:

• Occur through attenuated left atrial passive emptying (decreased by 5 mL) and reduced left ventricular end-diastolic volume (decreased by 11 mL) 6
• Reverse rapidly upon release of the inspiratory effort, with left atrial volumes actually increasing 4 mL above baseline 6
• May reflect acute left atrial stress with recurrent forceful inspiratory efforts 6

For respiratory muscle testing with balloon catheters, this technique is recommended only as a research tool or in specialized respiratory muscle function laboratories, as it requires passage of esophageal/gastric catheters and coordination that is difficult for naive subjects and patients. 1