The Control of Breathing during Weaning from Mechanical Ventilation (10)

Table 2 shows the individual and group mean data for respiratory system compliance (Crs), VP6, Pimax, P0.i, spontaneous respiratory rate (f), tidal volume (Vt), IVTr, dyspnea score, C02RT, and weaning duration. There was considerable overlap of these variables between groups. At the end of the weaning trial, patients of group 2 had higher respiratory rates (caused by group selection criteria) and smaller tidal volumes (8.7 vs 5.0 ml/kg, p<0.05). Subjects in group 2 tended to be weaker (mean Pimax of group 2=27 cm H20 vs 37 cm H20 in group 1, p = 0.11), while the compliance of the relaxed respiratory system, the severity of airways obstruction (VP6), and indices of pressure output of the respiratory muscles during spontaneous breathing (P01) were similar. Furthermore, average C02RT was the same, ie, 40 mm Hg, in both groups. Whereas all subjects in group 1 tolerated the full 1-h weaning period, the mean duration of the weaning period for group 2 was 13 ± 11 min.
Discussion

Patients with impending respiratory pump failure frequently manifest signs and symptoms of respiratory distress before acute hypercarbia and acidosis can be documented. Dyspnea, tachypnea, and asynchronous chest wall movements may be observed during weaning from mechanical ventilation and often herald the need to reinstate ventilatory support.

Table 2—Physiologic Assessment

PatientNo. Crs, L/cm HjO VP6,Us Pimax, cm HtO Poi.tcm HtO ft VT/kg,fml/kg TVTrf DyspneaScorett CO,RT, mm Hg Wsan Duration, min
Croup 1 1 0.04 1.05 35 5 27 8.8 0.43 17 34 60
2 0.07 0.36 30 2 23 6.1 0.46 9 39 60
3 0.04 0.13 60 6 28 8.1 0.44 11 41 60
4 0.05 0.35 32 6 27 8.9 0.40 11 41 60
5 0.06 0.33 27 6 8 11.4 0.40 15 44 60
Mean 0.05 0.44 37 5.0 23 8.7 0.43 13 40 60
SD 0.02 0.35 13 2.2 9.3 1.9 0.03 3.3 3.6 60
Group 2 6 0.14 0.10 26 8 40 4.4 0.35 15 35 25
7 0.05 0.50 30 5 35 6.5 0.45 19 44 15
8 0.07 0.08 30 4 14 3.9 0.36 19 49 10
9 0.13 0.04 36 5 22 3.0 0.38 20 50 20
10 0.06 0.75 32 5 36 5.6 0.47 18 31 5
11 0.09 0.05 9 4 32 6.5 0.36 39 10
12 0.06 0.20 25 8 30 4.9 0.32 39 10
13 0.04 0.40 25 5 38 5.1 0.49 13 35 20
14 0.10 0.03 32 40 9 37 3
Mean 0.08 0.24 27 4.9 32§ 5.0 0.39 15.8 40 135
SD 0.04 0.26 7.8 1.8 7 1.2 0.06 4.4 6.5 11

Category: Pulmonary Function | Tags: hypothesis, mechanical ventilation, respiratory distress, respiratory muscle