Propofol sedation reduces diaphragm activity in spontaneously breathing patients. Ultrasound assessment

BACKGROUND: The diaphragm is the most important respiratory muscle in humans, and the close relationship between inspired volume and diaphragmatic movement in normal subjects has led to investigations into diaphragmatic activity using ultrasound, during spontaneous breathing and sedative drug infusion. METHODS: A total of 36 consecutive patients undergoing diagnostic procedures under deep propofol sedation were studied. Ultrasound measurements included the following: diaphragmatic thickening end-inspiration (TEI) and end-expiration (TEE). Diaphragmatic thickening fraction (DTF) was calculated from [(TEI - TEE) / TEE] at various time points (at T0 basal; at T1 during propofol infusion; at T2 awakening). Oxygen was administered at 4 L/min, and oxygen saturation (SpO2), end tidal CO2 (EtCO2) and respiratory rate (RR) were recorded. RESULTS: TEI, and TEE decreased by 26.7% and 17.4%, respectively, during propofol infusion (T0 versus T1) (P<0.001), and rapidly recovered at T2 (22.7% and 15.8%). At procedure end (T0 versus T2), TEI maintained a significant reduction (10%, P<0.001), whereas TEE recovered completely. DTF decreased by 56.7% at T1 (P<0.001) but increased by 76.9% (P=0.001) at T2. Recovery after awakening (T0 versus T2) did not reach the baseline value, with a 23.4% difference (P<0.001). SpO2 remained above 96% and EtCO2 below 43 mmHg with no desaturation episodes observed. CONCLUSIONS: Our study showed that deep propofol sedation affects muscle activity in healthy patients. While diaphragmatic strength decreased during sedation, there was no clinically relevant effect on SpO2. The study also confirmed that ultrasound is suitable for measuring diaphragm activity during a normal clinical procedure.