The use of a respiratory monitor with a capnograph during the interhospital transportation of premature newborns

Mukhametshin R.F., Mukhametshin F.G., Kazakov D.P.

Regional Children's Clinical Hospital No. 1, Ural State Medical Academy, Yekaterinburg, Russia

Correction of ventilator parameters is one of the main tasks of pre-transport training. Isolated monitoring of oxygenation in such a situation cannot be considered sufficient. The purpose of the ventilator is to normalize not only oxygenation, but also CO2 elimination and optimization of lung volumes. The accuracy of assessing the adequacy of the chest excursion is largely determined by the experience of the staff, therefore it is deeply subjective [7]. Since noninvasive monitoring of CO2 in the process of re-education has a number of features and technical difficulties [1-5], capnography can only act as an auxiliary mechanism for monitoring the adequacy of ventilation. With the development of respiratory technology and the evolution of respiratory support regimes, routine measurement of respiratory volume, all associated calculated indicators, as well as respiratory graphical monitoring come to the fore. Many publications [8-10] describe the features of respiratory mechanics indicators in newborns with RDSN. Monitoring and correction of the volume of minute ventilation allows achieving the required PaCO(2), avoiding hyper- and hypoventilation [11-12]. Another important area of use of respiratory monitoring is the optimization of ventilator parameters and the implementation of a protective ventilation strategy [13]. This approach makes it possible to reduce the frequency of IVF in children with RDS on a ventilator. Respiratory monitoring is a useful tool when performing ventilation in newborns [14]. Real-time graphical monitoring allows you to constantly monitor and regulate the patient-respirator relationship [15]. Graphs provide objective information about the effectiveness of pharmacological agents and changes in the patient's condition and allow to optimize the ventilator. Therefore, graphical respiratory monitoring becomes an important tool when performing a ventilator. Respiratory monitoring has great prospects during stabilization and transportation of children to a ventilator [6].

The purpose of this study is to study the safety and effectiveness of the use of respiratory monitoring at the stages of re-education of premature newborns and to assess the possibility of its use in the complex of pre-transport preparation and transportation of a premature newborn.

Materials and methods of research

Design: a prospective, non-randomized, controlled study. The study included premature newborns with an RDSN clinic, weighing less than 2000 grams at birth, on a ventilator, born in maternity hospitals of the Sverdlovsk region in the service area of the CSTO RCN No. 1, re-hospitalized by the CSTO RCN No. 1 team in the CSTO ORITN No. 1 at the age of up to 3 days. Exclusion criteria: congenital malformations, including CHD, abdominal surgical pathology, re-education from the ORITN of the CSTO No. 1 before removal from the ventilator, newborns with hypothermia upon admission to the ORITN. The study included 95 newborns: 46 in the main group and 49 in the control group.The groups do not differ in significant anamnestic data.Statistical processing was performed on a personal computer using software packages Microsoft Office Excel 2003, SYSTAT 10.2, BIOSTAT. Statistical tools: mean, standard deviation of the mean, standard error of the mean, 95% confidence interval, Student's criterion, analysis of variance.

Research methodology: transportation of all newborns was carried out in the Draeger Transport-Incubator-5400 transport system equipped with a Babylog 2 ventilator, against the background of a constant infusion of 10% glucose solution with a Braun Perfusor syringe dispenser. Correction of ventilator parameters and monitoring at the stages of re-education in newborns of the main group was performed on the basis of data from a respiratory monitor with a Novametrix CO2SMO capnograph, model 8100. Flow sensor – pneumotachographic, neonatal, capnographic sensor – infrared, in the main stream. Analyzed parameters: respiratory volume (VT), volume of minute ventilation (VE), minute alveolar ventilation (VA), compliance (C), aerodynamic resistance of the respiratory system (R), pressure (P), volume (V), flow (Fl) curves, pressure-volume (P-V) and volume-flow (V-Fl) loops, exhaled CO concentration2(etCO2). The correction of the ventilator parameters was carried out according to the following algorithm: normalization of respiratory volume (5-6 ml / kg), normalization of minute ventilation (200-300 ml / kg), normalization of the shape of the pressure-volume loop due to the exclusion of upper and lower inflections of the path, selection of the optimal inhalation time along the flow curve. Pulse immortality was also carried out at all stages of re-education. Correction of ventilator parameters and monitoring during transportation in the control group was performed on the basis of visual data (chest excursion volume, auscultation pattern, skin color) and pulse oximetry data.

Analyzed outcomes: the status and CBS of the patient upon admission to the ORITN, radiological signs of emphysema, pneumothorax; results of the intensive stage of treatment: mortality, duration of ventilator, duration of NSAP, duration of the intensive stage of treatment, the need for IVF, the need for repeated intubation, the frequency of VJC 1-2, VJC 3-4, occlusive hydrocephalus, gross PVI, BPD, OAP, SSVO.

Research results and their discussion

The initial parameters of the ventilator in the groups do not differ (Table 2). Correction of respiratory support parameters using a respiratory monitor allowed to significantly reduce the respiratory volume, the volume of minute ventilation, increase the volume of alveolar ventilation and increase EtCO2 (Table 1). Optimization of ventilator parameters in newborns of the main group due to a significant increase in the positive pressure of the end of exhalation made it possible to significantly reduce the fraction of oxygen in the inhaled mixture, peak inhalation pressure and inhalation time (Table 2). At the stage of transportation, the parameters were somewhat tightened, and 60% oxygen was used. This is due to the technical features of the transport respirator (the inability to supply Pip less than 20 cm of water, the inability to regulate FiO2, the inability to regulate ti).

Table 1.

Respiratory monitoring at the stages of re-education

Source Before transportation Transportation
  M (95% CI) M (95% CI) M (95% CI)
etCO2, mm Hg st 22,41 (19,54-25,29) 28,26* (25,89-30,63) 28,96* (26,46-31,45)
VT, ml/kg 7,05 (6,18-7,91) 5,26* (5,00-5,51) 6,33 (5,9-6,76)
VE, ml/kg 388,41 (336,17-441,23) 280,39* (258,3-302,42) 319,71* (289,51-351,72)
VA, ml/kg 201,51 (170,56-233,21) 158,84* (146,83-172,11) 181,32 (167,81-196,14)

* - a significant difference between the stages of re-education.

Table 2.

Ventilator parameters at the stages of re-education

R,
min-1
Fl, l/min Ti, sec Pip, see water.st PEEP, see water.st FiO2, %
Initial data M (95% CI) Main group (n=46) 53,41 (50,44-56,38) 6,26 (5,8-6,72) 0,297 (0,28-0,314) 22,07 (20,39-23,73) 4,24 (3,79-4,69) 52,91 (45,95-59,88)
Control group (n=49) 55,36 (52,92-57,82) 6,00 (5,77-6,24) 0,294 (0,288-0,3) 22,08 (20,86-23,31) 4,27 (4,06-4,47) 58,12 (50,89-65,35)
P 0,307 0,301 0,701 0,987 0,914 0,300
Before transportation M (95% CI) Main group (n=46) 53,00 (50,58-55,43) 6,00 (5,63-6,37) 0,264* (0,255-0,273) 18,33* (17,06-19,59) 6,09* (5,89-6,28) 32,74* (28,42-37,06)
Control group (n=49) 55,51 (53,12-57,89) 5,88 (5,67-6,08) 0,294 (0,289-0,3) 21,18 (20,22-22,15) 4,34 (4,09-4,56) 53,76 (47,97-59,54)
P 0,141 0,557 <0,001 <0,001 <0,001 <0,001
Transportation M (95% CI) Main group (n=46) 49,91* (47,02-52,81) 20,60* (19,65-21,55) 6,56* (6,35-6,76) 60,89* (59,09-62,68)
Control group (n=49) 57,10 (55,27-58,93) 22,04 (20,89-23,04) 4,41 (4,18-4,64) 69,59* (64,55-74,63)
P <0,001 0,057 <0,001 0,002
Upon receipt of M (95% CI) Main group (n=46) 47,89* (44,79-50,99) 6,78 (6,49-7,08) 0,262* (0,256-0,268) 18,62* (17,22-20,03) 6,13* (5,89-6,37) 30,37* (26,47-34,27)
Control group (n=49) 53,06 (49,95-56,17) 7,29* (6,79-7,79) 0,278* (0,272-0,284) 21,47 (20,13-22,81) 5,04* (4,81-5,27) 50,35 (44,05-56,65)
P 0,013 0,007 <0,001 0,003 <0,001 <0,001
Correction of parameters according to the CBS data
M (95% CI)
Main group (n=46) 45,65* (42,17-49,14) 6,71 (6,39-7,03) 0,262* (0,256-0,268) 16,77* (15,67-17,86) 5,93* (5,77-6,09) 25,02* (22,26-27,79)
Control group (n=49) 46,20* (42,15-50,26) 7,27* (6,78-7,75) 0,276* (0,27-0,283) 19,51* (18,04-20,98) 5,00* (4,77-5,23) 34,31* (30,28-38,34)
P 0,309 <0,001 0,001 <0,001 0,052 <0,001

* - the reliability of the differences between the stages of re-education (P<0.05)

** - reliability of differences between groups (P<0.05)

More than 70% of newborns in the main group had reduced peak blood pressure compared to 26.53% of children in the control group. Optimization of parameters in the main group allowed to reduce FiO2 in 69.57% of children compared to 30.61% of children in the control group. In 18.37% of cases, children of the control group required an increase in FiO2, while in the main group FiO2 did not increase in any newborn. Upon admission to the ORITN, newborns of the main group required a significantly lower fraction of oxygen in the inhaled mixture, peak inhalation pressure and inhalation time than newborns of the control group (Table 2).

Indicators of systemic hemodynamics at the stages of re-education between the groups also did not differ significantly. The resulting significant deviations of heart rate, systolic blood pressure, SpO2 and temperature upon admission to the ORITN fell within the normal limits.

Significant differences in the condition of the patients of the studied groups were revealed upon admission to the ORITN. The children of the main group had a significantly lower pH value, pO2, a higher value of pCO2. Significantly more often, the children of the main group had a normal blood gas composition at admission. Significantly more newborns of the main group had normal values of pCO2. A significantly smaller percentage of children in the main group compared with the control group had hypocapnia when they were admitted to the ORITN. Metabolic acidosis and hypoglycemia were also less reliably detected. Radiological signs of emphysema at admission were significantly more often detected in newborns of the main group (Table 3).

Table 3.

Status of the CBS upon receipt

Main group (n=46) Control group (n=49) Difference p
  M (95% CI) M (95% CI) M (95% CI)
pH 7,329 (7.302-7.357) 7,362 (7.326-7.398) -0,032 (-0,077-0,012) 0,154
rSO2, mmHg 43,32 (40.08-46.56) 36,6 (32.65-40.55) 6,72 (1,67-11,77) 0,010
rO2, mmHg 40,39 (40.55-43.57) 47,27 (43.35-51.19) -6,88 (-11,87- -1,89) 0,07
VE, mmol/l -3,91 (-4.97- -2.86) -5,11 (-6.19- -4.03) 1,20 (-0,29-2,69) 0,113
NSO3, mmol/l 20,96 (20.12-21.81) 19,37 (18.24-20.49) 1,37 (-0,25-2,98) 0,096
Lactate, mmol/l 3,22 (2.71-3.73) 3,47 (2.90-4.04) -0,25 (-1,02-0,52) 0,521
Normal pH, % 69,56 (55.75-83.38) 69,39 (56.01-82.76) 11,84 (-9,25-32,94) 0,267
Acidosis, % 30,44 (16.62-44.25) 30,61 (17.24-43.99) -11,84 (-32,94-9,25) 0,267
Normal rSO2, % 80,43 (68.52-92.35) 46,94 (32.46-61.42) 36,65 (15,68-57,62) <0,001
Hypercapnia, % 8,69 (0.24-17.16) 10,2 (1.42-18.99) -5,17 (-16,18-5,85) 0,353
Hypocapnia, % 10,87 (1.52-20.22) 42,86 (28.49-57.22) -31,48 (-51,74- -11,22) 0,003
Metabolic acidosis, % 60,87 (46.22-75.52) 77,55 (65.44-89.66) -16,61 (-38,19-4,96) 0,129

* - significant difference between groups (P<0.05)

In the control group, a significantly larger number of children required parameter correction than in the main group, as well as a significantly larger number of children who had reduced FiO2 according to the CBS analysis. The percentage of newborns transferred to VCHIVL in the groups did not differ. The same number of children in both groups required an increase in Pip (9.3 and 8.16% in the main and control groups, respectively) and a decrease in Pip (46.51% and 57.14% in the main and control groups, respectively). Even after the correction of the ventilator parameters according to the CBS data, there was a significant difference between the groups in the number of children with hypocapnia (19.56% and 40.82% in the main and control groups, respectively) and normocapnia (71.74% and 46.94% in the main and control groups, respectively). Analysis of the results of the intensive stage of treatment revealed a significant reduction in the duration of the ventilator and the duration of the intensive stage of treatment. There is a tendency to decrease the frequency of severe VVC and BPD. (table 4).

Table 4.

Outcomes and complications of the intensive stage of treatment

Main group (n=46) Control group (n=49) Difference p
  M (95% CI) M (95% CI) M (95% CI)
Lethality, % 6,52 (-0.89-13.94) 8,61 (0.22-16.11) 1,64 (-9,12-12,4) 0,763
Duration of the ventilator, day 4,06 (2.99-5.14) 8,33 (5.98-10.69) 4,27 (1,68-6,86) 0,002
The need for VCHIVL, % 15,22 (4.43-26.00) 10,2 (1.42-18.99) -5,01 (-18,66-8,64) 0,468
Duration of VCHIVL, day 4,43 (1.77-7.09) 3,2 (0.24-6.16) -1,23 (-4,74-2,29) 0,454
Duration of nSRAR, day 2,42 (1.66-3.18) 3,0 (2.22-3.78) 0,49 (-0,59-1,57) 0,370
Duration of IT, day 8,34 (6.72-10.15) 14,85 (11.39-18.32) 6,42 (2,58-10,25) 0,001
Pneumothorax, % 4,35 (-1.78-10.47) 2,04 (-2.06-6.14) -2,31 (-9,49-4,88) 0,526
IEL, % 0.00 (0) 2.04 (-2.06-6.14) 2,04 (-2,14-6,23) 0,335
Radiological signs of emphysema, % 2,17 (-2.21-6.55) 8,16 (0.22-16.11) 5,89 (-3,13-15,11) 0,195
BPD, % 8,69 (0.24-17.16) 20,4 (8.71-32.10) 11,71 (-2,69-26,12) 0,110
VJK 3-4, % 15,22 (4.43-26.00) 24,49 (12.01-36.97) 9,27 (-7,09-25,64) 0,264
VJK 1-2, % 30,43 (16.62-44.25) 29,17 (15.83-42.50) -3,35 (-22,08-15,38) 0,723

* - reliability of differences between groups (P<0.05)

The results obtained indicate that the correction of ventilator parameters using a respiratory monitor makes it possible to optimize lung volumes. The increase in REER ensures that the normal value of the functional residual capacity is maintained with the involvement of a significantly larger volume of lung tissue in the gas exchange process, which reduces the volume of ventilation of the dead space and increases alveolar ventilation. This allows you to significantly reduce the need for oxygen and reduce FiO2. Optimization of the pulmonary volume makes it possible, by reducing the respiratory volume and lowering the peak pressure, not to significantly disrupt gas exchange and maintain normal SpO2 at significantly lower oxygen fractions in the inhaled mixture. Maintaining the optimal lung volume and the minimum required respiratory volume throughout transportation can significantly reduce the percentage of hyperventilated children, which ensures earlier removal from the ventilator.

Conclusions

Thus, the correction of the ventilator parameters using respiratory monitoring allows, already at the stage of pre-transport preparation, to significantly reduce the rigidity of the ventilator and FiO2 parameters and normalize gas exchange, thus bringing as close as possible a high level of care to a child in a medical facility with low capabilities, which allows to influence the duration of the ventilator and the intensive stage of treatment. The results of the study demonstrate that the Babylog2 device does not have sufficient "flexibility" in the selection of ventilation parameters in premature newborns and its use requires forced, unjustified tightening of ventilation parameters.

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Published: collection of articles of the 3rd International Congress on Respiratory Support.-Krasnoyarsk, 2009

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