The Preliminary Study On Vibration Of Neonatal Transport Equipment

Background:During the transportation of newborns,the transport incubator will be subjected to vibration caused by the mechanical movement of the ambulance.The harm and adverse effects of vibration on human body have been widely studied and discussed throughout the world.Exposure to vibration may cause adverse reactions in multiple organs and systems of the human body.The effects of vibration on the human body are complex and may depend on the amplitude,frequency,direction,duration of the vibration,and the part of the body to which the vibration is directed.But when it comes to the effects of vibration on newborns,there’s still a lot of research to be done.Studies have suggested that transport may increase mortality in premature infants,the potential link between premature infant mortality and neonatal transport reveals the potential dangers of vibration exposure in the transportation environment.Premature infants whose corrected gestational age has not yet reached 32-34 weeks have limited ability to autonomously adjust and coordinate environmental pressure.Exposure to vibration environments may lead to poor prognosis.ISO-2631 is the international standard in the field of vibration.It sets the maximum Sound Pressure Level（SPL）for the vibration of medical supplies in healthcare facilities and the comfort standard for whole body vibration（WBV）in transport.In 2018,the United States Government Industrial Hygienists Conference developed standards for exposure of industrial employees to WBV,which stated that adults should not be exposed to working environments with ambient vibration greater than 0.87m/s²,but the impact of vibration on newborns has not been regulated and evaluated by international standards.At present stage,the international studies on the impact of vibration factors on newborns during transport is still relatively limited,and there is no research on vibration during neonatal transport in our country,and the domestic neonatal society does not have methods and means to measure the vibration of neonatal environment.There is still a lack of accurate measurement data support for the vibration of the environment in which newborns live.Objective:To establish a standardized monitoring model and measurement standard for measuring the environmental vibration of neonates,to preliminarily explore the vibration of the neonatal transport incubator and its impact on the physiological state of the transferred newborn,and to verify whether the new foreign transport mode of"kangaroo care"transport can be a transport scheme to reduce the vibration of neonatal transport.Methods:Part One:Successful establishment of standardized monitoring model for neonatal environmental vibration and measurement of incubator vibration data in NICU conventional environment1.Study object and groupsThe study object is an imported advanced neonatal incubators,and the research location is set in the Neonatal Intensive Care Unit（NICU）of Shenzhen Children’s Hospital.The sensor is placed in three different locations in the incubator,namely on the incubator chassis（under the mattress）,on the mattress and on the incubator cover.The incubator is placed under the central air conditioning outlet and if the air conditioning is turned on,the wind speed is adjusted to the maximum allowed range.The incubator is preheated in advance and data recording begins after the ambient temperature reaches the set temperature.All vibration data are carried out under the stable running state of the incubator.In the experiment,4 groups were set up according to the switching conditions of the motor and air conditioning:background group,incubator and air conditioner are both off;double-open group,incubator and air conditioner are both running;incubator group,only the incubator is running;air conditioner group,only air conditioner is running.2.Establishment of standardized monitoring of neonatal environmental vibrationAn acceleration sensor（WT901SDCL,WITMOTION,Shenzhen）was used to record the acceleration in the triaxial direction at a specific point position.The X-axis represents the acceleration from the right side of the sensor to the left side and the Y-axis represents the acceleration from rear to front and the Z-axis represents the acceleration from below to above the sensor.The sensor orientation can be defined according to the experimental subject.The acceleration measured by the sensor subtracts the gravitational acceleration at zero（approximately 9.8m/s²）.We obtain a large amount of acceleration data of the three directional axes in a period of time by continuously measuring the acceleration changes of the experimental object in three directions.The global acceleration of this frame can be obtained by using the square root of acceleration of each frame on the three direction axes.Fast Fourier Transform（FFT）was performed on the obtained original acceleration data by using the function algorithm,and the original acceleration data in time domain was converted into frequency domain data and time-frequency domain data.After the results of vibration frequency domain data are obtained,the RMS acceleration of each frequency range is calculated by using one-third octave to divide the frequency band.The root-mean-square acceleration within each frequency range is weighted and the weighted acceleration value of the frequency range is obtained.Finally,the acceleration（m/s²）result is converted into SPL（d B）by the formula and analyzed.Through the above methods,standardized monitoring of neonatal environmental vibration is established.According to ISO-2631,the SPL（d B）of a medical facility should be less than 72d B.Part Two:Effects of vibration factors on the physiological state of sick newborns during interhospital transport1.Study objectsThe neonatal patients who were transferred to the NICU of Shenzhen Children’s Hospital from December 2020 to March 2021,excluding those who used sedative drugs during the transportation,were clearly diagnosed with severe neurological conditions such as neonatal intracranial hemorrhage,and were in a coma,and finally 73 newborns were included.Physiological state was evaluated by the Transport Risk Index（TRIPS）of Physiological Stability（physiological stability）after continuous and uninterrupted measurement of vibration data during transport.Clinical data of patients were collected,including days of age,gestational age,birth weight,admission weight,diagnosis,Apgar score,transport hospital,transport distance and transport time.2.Data acquisition methodAll enrolled neonates were scored using TRIPS scale to assess their physiological status before being tranferred.The newborns were placed in the transport incubator（Aviator,Airborne,USA）and transferred in a supine position on a foam mattress.The newborn is secured in a"nest"on the mattress with a safety belt.After the transfer platform was placed on the ambulance,the acceleration sensor（WT901SDCL,WITMOTION,China）was immediately started to record the 3-axis acceleration of the child’s head in the incubator.The sampling frequency was set at 20Hz.Recording was stopped after the ambulance returns to the hospital.After returning to the ward,TRIPS score was performed again to evaluate the physiological status of the children after transport.3.Vibration data processing methodAfter sorting out the triaxial acceleration data in the transport process,the mathematical calculation was carried out by MATLAB software to obtain the WBV data of the children in the transport process.Measure the acceleration in three different directions at squares of meters per second（m/s²）.Transfer position is supine,where the X-axis represents the acceleration from the right to the left direction of the newborn,the Y-axis represents the acceleration from the hip to the head,and the Z-axis represents the acceleration from the back to the chest.The acceleration measured on the Z-axis will subtract the gravitational acceleration（approximately 9.8m/s²）.The acceleration sensor WT901SDCL is placed on the head side of the incubator.In accordance with the ISO2631-1,the root mean square（RMS）acceleration measures whole-body vibration levels.First,the respective root mean square acceleration of the 3 axes is calculated according to the formula,and then the final WBV is calculated by using the 3-axis root mean square acceleration.The mean and peak of X,Y and Z acceleration were counted respectively and the WBV of each group was counted.Part Three:Exploration of the new"Kangaroo care"transport mode and evaluation of vibration differences compared with traditional"incubator"transport1.Study objects:Our hospital has stipulated that neonatal transport must be carried out through the transport incubator.In order to ensure the safety of neonates,neonatal vibration in Kangaroo care group was measured by neonatal manikin.At the same time of routine inter-hospital neonatal transport,the"Kangaroo care"transport was simulated by the neonatal manikin held by the transport doctor or nurse.20 patients were assigned to routine transport and 20 patients to manikin group.2.Vibration measurement method:The transport vibration was measured by standardized monitoring model of neonatal environmental vibration.In the manikin group,the three-axis acceleration sensor was fixed on the head of the neonatal manikin by 3M double-sided tape.During the actual transport period,the transport doctor or nurse transferred the newborn manikin by Kangaroo care position,that is,the baby was held vertically,and the passenger’s seat backrest adjusted all the way,place the model in an approximate"prone position".After the ambulance started,the acceleration sensor at the newborn incubator and the sensor on the manikin were turned on at the same time,and the sensor recording was stopped at the same time after the ambulance returned to Shenzhen Children’s Hospital.When recording acceleration data,the sensor on the newborn manikin will also record angular velocity and angle data,and conduct posture correction in the later data analysis to ensure that the directions of acceleration vector measured by the two groups are consistent.The subsequent vibration data collection,measurement and data processing methods are the same as in Part Two.Results:Part One:Successful establishment of standardized monitoring model for neonatal environmental vibration and measurement of incubator vibration data in NICU conventional environment1.Group vibration measurement resultsThis study successfully established a standardized monitoring model for neonatal environmental vibration.This part shows the vibration at three different locations of the incubator and the effects of the incubator motor,central air conditioning and mattress on the vibration.In most scenarios,acceleration peaks of vibration occur at 1.25—5Hz and16—20Hz,and these frequencies are close to the resonant frequencies of human body.When the newborn is lying in the incubator,the mattress and the cover plate can effectively reduce the vibration of the incubator motor and the central air conditioning to the patient.The central air conditioning in the NICU will also produce significant vibration on the incubator,but the vibration can be reduced by the incubator cover and the mattress.When the sensor is placed under the mattress,the vibration caused by the incubator motor will exceed the medical environment vibration standard（72d B）,and when the sensor is placed on the incubator cover,the influence of central air conditioning will also cause the vibration of the incubator to exceed the standard.However,when the patient is on the mattress,that is,under the conventional treatment scenario,all vibration values meet the standard.2.Analysis of long-term high-frequency vibration of the double-open group at the position of the mattressConduct frequency domain and time domain vibration analysis on the double-open group of the mattress,which is the condition closest to the actual treatment environment for newborns.The X-axis acceleration changes uniformly throughout the measurement process without significant fluctuation.The maximum vibration frequency of the frequency domain diagram is 25Hz,and there is a secondary vibration amplitude around3Hz,17Hz and 50Hz.The time-frequency diagram shows that the vibration energy reaches the maximum at the 25Hz frequency within 1 hour and 20 minutes,and the 25Hz frequency vibration is converted to 17Hz vibration after 1 hour and 20 minutes.The Y-axis time-domain map showed that the vibration amplitude was uniform overall,and the Y-axis vibration amplitude narrowed after 1 hour and 20 minutes.The frequency diagram shows that the maximum vibration frequency is consistent with the X-axis,about 25Hz,and no other obvious secondary vibration frequency is observed.The time-frequency diagram shows that the main vibration frequency is about 25Hz,and the vibration energy decreases after 1 hour and 20 minutes.The amplitude of the Z-axis time-domain diagram remained consistent throughout the whole process,no obvious fluctuation was observed,and the amplitude was stable.In the frequency diagram,the maximum vibration frequency can be seen at 22Hz and 25Hz,while multiple vibration frequencies can be seen at 16Hz and 17Hz.It can be seen from the time-frequency diagram that there are multiple frequency bands of vibration energy around 20Hz,which are uniformly consistent throughout the whole process.Part Two:Effects of vibration factors on the physiological state of sick newborns during interhospital transport1.Overall situationA total of 73 newborns were included in the neonatal transport study and the vibration values during neonatal transport exceeded the adult health standard threshold.2.Analysis of transportation vibration situationAccording to the final WBV result and reference to ISO-2631 standard,children with WBV between 0.8 and 1.25m/s²were set as the uncomfortable group,and those with WBV between 1.25 and 2.5m/s²were set as the very uncomfortable group.54 cases were included in the uncomfortable group and 19 were included in the very uncomfortable group.The magnitude of vibration during transport was related to speed（P<0.05）,road condition（P<0.05）and driver（P<0.05 related）,independent of gestational age,age after birth,birth weight,admission weight and Apgar score.Different vibration conditions did not cause differences in TRIPS scores.3.Effects of transport road conditions on vibration and physiological stateAccording to the municipal group（n=37）and highway group（n=36）,there were significant statistical differences between the two groups in transport duration（P<0.05）,transport distance（P<0.05）and average transport speed（P<0.05）.The average vibration（P<0.05）and peak vibration（P<0.05）were higher in highway group than municipal group.The vibration differences were mainly reflected in the Z-axis（from back to chest）and X-axis（from right to left）,and the vibration differences of the Y-axis（from hip to head）were not significant.There was no statistical difference in TRIPS before and after transport,and the TRIPS values decreased after transport,after weighting the data,correlation analysis was performed using the Spearman test.There was no correlation between TRIPS score and WBV before transport（P=0.256）,TRIPS score and WBV after transport（P=0.307）,TRIPS score changes and WBV（P=0.333）.The person test was used for correlation analysis of relevant data,and it was found that there was no correlation between admission weight and WBV（P=0.912）,while the correlation between distance and WBV was weak（P=0.111）.There was a positive linear correlation between average speed and WBV（r=0.437,P<0.001）.We conducted multiple regression analysis on the relationship between admission weight,transport distance,average speed and WBV,using stepwise regression method.The model finally included two independent variables,the average speed and the transport distance.The Durbin-Watson statistic was 1.901,satisfying the independence requirement.Residuals are approximately normally distributed,and the data meet the normality requirements.In the regression coefficient test,the two independent variables were statistically significant.The final regression equation is Y（WBV）=0.835-0.002X₁（distance）+0.008X₂（average speed）.4.Effect of transport drivers on vibrationA multi-group rank sum test was used to test the significance of the difference in sample means between each group.There was no statistical difference between the gestational age,age after birth,admission weight,transport distance,transport speed and transport duration of the 7 groups of patients.Using analysis of variance,there were statistical differences in WBV（P<0.05）and partial root mean square acceleration between different groups.From the direction of vibration,the root mean square acceleration of the X-axis and the Y-axis were statistically different（P<0.05）,and not that of the Z-axis（P=0.053）.There were statistical differences between the Y-axis maximum acceleration（P=0.002）,and no statistical differences between the X-axis maximum acceleration（P=0.688）and the Z-axis maximum acceleration（P=0.06）.There were no significant difference in TRIPS scores.Part Three:Exploration of the new"Kangaroo care"transport mode and evaluation of vibration differences compared with traditional"incubator"transportThe WBV of the incubator group was 1.1945±0.1803m/s²,exceeding the adult health standard of 0.87m/s²,while the WBV of the Kangaroo care position group was1.0569±0.1459m/s²,also exceeding the adult health standard of 0.87m/s².P<0.05 was found between the two groups,indicating a statistical difference.There was a statistical difference between the two groups in the X-axis root mean square acceleration,which was greater in the incubator group（0.6599±0.1126m/s²）than in the Kangaroo care position group（0.4448±0.0719m/s²）.There was also a statistical difference between the two groups in the root-mean-square acceleration on the Y-axis,and the incubator group（0.7273±0.1125m/s²）was also greater than the Kangaroo care position group（0.4874±0.1199m/s²）.The RMS acceleration of Z-axis was different from that of X-axis and Y-axis.The Kangaroo care position group（0.8159±0.1365m/s²）was higher than that of incubator group（0.6681±0.1560m/s²）,and the difference was statistically significant.In terms of the maximum acceleration,the maximum acceleration of the Kangaroo care position group on the X-axis was 8.0197±1.6409m/s²,which was significantly higher than that of the incubator group（5.3161±1.1194m/s²）.There was also a statistical difference in the Y-axis maximum acceleration between the two groups,which was7.1854±1.1979m/s²in the Kangaroo care position group and 5.5794±1.3689m/s²in the incubator group.The maximum acceleration of Z-axis in the incubator group was also lower than that in the Kangaroo care position group,and there was a statistical difference between the two groups.The vibration in the three directional axes of the Kangaroo care position group is mainly concentrated below 18Hz,indicating that the main energy of the vibration is less than 20Hz,and the vibration less than 20Hz is in the infrasound range.The energy of vibration attenuates obviously when it exceeds 18Hz.The vibration below 1Hz is mostly interference,and there is an obvious energy peak at 1—3Hz along the Z-axis.Conclusions:1.A standardized monitoring model of neonatal environmental vibration was successfully established,and the measurement results were close to the ISO-2631standard.The vibration of incubator will be affected by incubator motor and central air conditioning,incubator mattresses and incubator covers can effectively reduce vibration.The vibration of the newborn incubator in our department met the standard under normal working scenarios.In some scenarios,the vibration of the incubator exceeded the vibration standard value for medical institutions recommended by the ISO-2631 standard.2.During transport,all neonates were in an uncomfortable state,some of them were in a very uncomfortable state,and were exposed to vibration environment higher than adult health standards.The magnitude of newborn transport vibration was related to the transport speed,driver control conditions and transport road conditions.Newborns during transport were exposed to vibration,but the vibration during transportation did not aggravate the physiological state of newborns.3.Compared with the traditional"incubator"transport,the new foreign"Kangaroo care"transport can reduce the vibration during transport,but its vibration exposure still exceeded the adult health standard.When the"Kangaroo care"was used for neonatal transportation,the whole body vibration experienced by the sick newborns was close to the resonance frequency of the newborn’s body.However,when the neoborns were transferred using"Kangaroo care",the instantaneous vibration peak of the neoborns would be higher than that of incubator transport.