[Diaphragmatic reserve strength in obese patients]. / Reserva de fuerza del diafragma en pacientes obesos.

Nine obese patients (OB) and seven normal subjects (N) were studied in order to determine diaphragmatic strength reserve, measured in terms of diaphragm Tension/Time Index (TTdi). This index was measured with the patients awake and during the obstructive apnea (OA) episodes. TTdi was 2.7 times superior in the OB (p < 0.0005) and was related with a lower Pdi Max (102 vs 202 cm H2O; p < 0.005) and with a higher Pdi (9 vs 6 cm H2O; p < 0.05). During OA the TTdi was higher than the threshold value to develop diaphragmatic fatigue (0.15-0.20) in three patients. This value was not exceeded in one patient because of striking paradoxical diaphragmatic movements. As for anthropometric data, DPI% range was higher and wider in OB (Table 1). The pCO2 in OB was 40 +/- 6 mmHg. In all patients (Table 3), severe hypoxia and hypercapnial were observed. TTdi evolution in an OA in 4 patients can be appreciated in Figure 3. It can be concluded that the diaphragmatic strength reserve is reduced in OB so that they are more susceptible to develop diaphragmatic fatigue. A fatigant respiratory pattern was also registered during the OA.