Gold standard in Dx of bilat. diaphragmatic paralysis

Gold standard in Dx of bilat. diaphragmatic paralysis (Murray p4833-34)
The “gold standard” diagnostic test is measuring transdiaphragmatic pressure using thin balloon-tipped polyethylene catheters placed in the esophagus and stomach and showing a lack of ability to generate a transdiaphragmatic pressure.
A: Normal esophageal (Pes) and gastric (Pga) pressure tracings. Note Pes becomes more negative and Pga more positive during normal inspiration owing to the action of the diaphragm.
B: Diaphragmatic paralysis where Pes and Pg deflect in the same direction showing no muscular activity of the diaphragm.

Pulmonary function testing in diaphragmatic paralysis

Pulmonary function testing in diaphragmatic paralysis

-MIP and MEP decrease (usually in early asymptomatic)
-MVV decrease next
-then Decrease in lung volume and FVC and FEV1
-DLCO may be decrease because of decrease in lung volume should use DLCO/VA

**VC in upright and supine
Measuring the vital capacity in the upright and supine positions is the most important pulmonary function test.

Normally, vital capacity in recumbency decreases by 10%. In unilateral paralysis, the vital capacity shows a decrease to 70-80% of the predicted level. The decrement is usually slightly more significant in the supine position.

In contrast, patients with bilateral diaphragmatic paralysis show a 50% decrease in vital capacity when they are supine. This decrease is from cephalad displacement of abdominal contents.

**MVV
Maximum Voluntary Ventilation (MVV) is a measure of the maximum amount of air that can be inhaled and exhaled within one minute. For the comfort of the patient this is done over a 15 second time period before being extrapolated to a value for one minute expressed as liters/minute. Average values for males and females are 140-180 and 80-120 liters per minute respectively.

can estimate MMV = 35xFEV1