Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Chest Diseases and Tuberculosis

The RSBI was first proposed by Yang and Tobin, and it is expressed by the relationship between respiratory rate and tidal volume measured by a spirometer with the patient breathing spontaneously for 1 minute (RSBI1). Values greater than 105 cycles/ min/L were considered predictive of unsuccessful weaning and extubation. The RSBI was more accurate and powerful in predicting weaning outcome than other traditional indices. Serial measurements of RSBI may be more useful in the weaning process. To study the predictive value of the RSBI measured at initiation and termination of a spontaneous breathing trial in weaning outcome. This study enrolled 84 known cases of COPD who had received mechanical ventilatory support due to acute on top of chronic type II respiratory failure that was evidenced by arterial blood gases analysis. They were admitted in the respiratory ICU in Giza chest hospital from April 2013 till March 2014. They were all subjected to full history taking, thorough clinical examination, twice daily ABG analysis and daily A - P chest x ray. RSBI was measured through the display of MV at the start (RSBIPS1) and after 2h (RSBIPS2) of an SBT while patients were ventilated using PS mode. RSBI was remeasured again using spirometry while patients were breathing spontaneously after 2h (RSBISP1) and again at the end after 4h of the trial (RSBISP2). The arterial to end tidal CO2 gradient was determined at the end of the 4h SBT, and Subsequently alveolar dead space was calculated for each patient. Our patients were further subdivided into 2 groups: Group 1 with successful weaning. Group 2 with failed weaning. This study has demonstrated that RSBIsp2, when remeasured at the end of an SBT, is superior to RSBIsp1 measured initially in predicting extubation outcome. Also successful weaning cases showed statistically significant lower mean value than failure cases. so lower values of RSBIsp2 are more likely to have successful weaning. Cut - off value of RSBIpsv1 was 51 with a diagnostic accuracy of 61.9%, and of RSBIpsv2 was 57 with a diagnostic accuracy of 58.4%.

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