Crying Pressures Crying PImax and PEmax

Rationale. Mouth pressures generated during crying efforts may provide an index of respiratory muscle strength in awake infants.

Measurements. Firm application of a rubber cushion mask against the face is sufficient to elicit crying efforts in the awake infant (14). An artificial leak in the mask has been used to prevent glottic closure. Airway occlusions are performed at the end or at the beginning of a crying effort to measure crying Pi,max and PE,max, respectively. Only peak crying Pi,max without a pressure plateau is available during crying. Crying PE,max can be measured at a pressure plateau sustained for 1 second.

Advantages. The main advantage is simplicity.

Disadvantages. Disadvantages include the following: (1) no determination of lung volume during the test; (2) gross potential pressure leaks around the mask; (3) artificially high peak crying Pi,max if no needle leak in the mask to prevent glottic closure; and (4) relatively high CVs, 11 ± 4 and 9 ± 3% (mean ± SD), respectively, as shown in one group of healthy infants.

Normal values. Normal values have been provided in a large group of healthy infants from the first month to the end of the second year of life (14). Peak crying Pi,max was 118 ± 21 cm H2O and independent of age and sex. However, overes-timation of peak crying Pi,max may have occurred because glottic closure was not prevented. Crying PE,max was 125 ± 35 cm H2O and was related to body weight.

Clinical application. Crying pressures may be useful in infants with neuromuscular disease (59).

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