Diaphragm and rectus abdominis thickness preservation is associated with successful extubation

Introduction: Diaphragm and rectus abdominis (RA) atrophy are associated with unsuccessful liberation from invasive mechanical ventilation (IMV) individually. To study the combined impact of diaphragm and RA atrophy in critically ill patients, we undertook to examine prospectively whether the ability to preserve the diaphragm thickness (Tdi) and RA thickness (Tra) as ascertained by ultrasound (US), was associated with early liberation from IMV and more ventilator free hours (VFH). Methods: We included consecutive subjects who were expected to need IMV for > 48 hours (pH < 7.25, creatinine >2.0 mg/dL, serum bicarbonate < 20 mEq/L, BUN >25 mg/dL and HR >110 bpm). Patients younger than 18 yrs., receiving IMV for a procedure, who underwent thoracic or abdominal surgery within 30 days, and with confirmed neuromuscular diseases were excluded. US directed Tdi and Tra was measured at day 0 (day of intubation), day 7 and day 14. Preserved Tdi and Tra was defined as no loss in thickness of muscles when compared to day 0 scans. Successful extubation was defined as not needing re-intubation or tracheostomy during the index hospitalization. Results: 106 patients were screened and 73 were scanned on day 0, 51 at day 7, and 19 were rescanned at day 14. At day 7, 16 patients had preserved both Tdi and Tra, whereas 35 did not. Both the groups were similar in age, comorbidities, and laboratory parameters at the time of intubation except higher PaCO2 (59.4 vs 47, p 0.05) was noted in the group with preserved Tdi and Tra at 7 days. In univariate analysis the group with preserved Tdi and Tra at day 7 had more successful extubations (93.7% vs 65.7%, p 0.04) and more VFH at day 7 (86 vs 0, p 0.01) and day 14 (254 vs 99, p = 0.02). In multivariable analysis, those with preserved Tdi and Tra at day 7 were more likely to achieve successful extubation (aHR 2.4, 95% CI 1.2 to 4.8) and more VFH at day 7 (38.1 hours, 95% CI 4.3 to 71.9) and day 14 (79.50 hours, 95% CI 9.06 to 149.95). Conclusions: Ability to preserve Tdi and Tra at week 1 in critically Ill intubated patients was associated with higher chances of successful extubation and more VFH at weeks 1 and 2. This finding may facilitate future interventional trials aimed at improving respiratory muscle integrity in patients undergoing IMV.