Transdiaphragmatic pressure in young adult Singaporean subjects--normal values and a comparison between different respiratory manoeuvres.

BACKGROUND

Most published normal values for transdiaphragmatic pressure (Pdi) have been from Caucasian subjects and there is no universal agreement regarding the most appropriate manoeuvre for assessing Pdi.

AIMS

The aims of our study were to obtain normal values and to compare the different manoeuvres used to assess Pdi in normal young Singaporean adults.

METHODS

Twenty-four normal subjects (23 Chinese, one Indian) were studied by measuring Pdi during maximal sniffs from functional residual capacity (sniff Pdi), maximal inspiration to total lung capacity (Pdi TLC) and maximal static inspiratory efforts from residual volume (Pdi PImax).

RESULTS

Mean values +/- SD for sniff Pdi, Pdi TLC and Pdi PImax were 101.8 +/- 31.7, 46.8 +/- 26.4 and 83.5 +/- 35.5 cm H2O respectively. Sniff Pdi was significantly higher than Pdi TLC (p < 0.001) and Pdi PImax (p = 0.005). Pdi PImax was significantly higher than Pdi TLC (p < 0.001). Males had significantly higher values for sniff Pdi (p = 0.026) and Pdi PImax (p = 0.022) than females. There was a significant correlation between the different methods of recording Pdi. Sniff Pdi had the highest values, least between- and within-subject variation and most consistent pattern of respiratory muscle recruitment with the lowest proportion of negative gastric pressure (Pg) values (p < 0.001).

CONCLUSIONS

Therefore, sniff Pdi may be better than Pdi TLC and Pdi PImax in assessing diaphragm function. Also, our subjects seemed to have lower sniff Pdi and Pdi PImax, and higher Pdi TLC compared with Caucasian subjects.