Pulse oximetry vs non-invasive blood pressure/oscillometry to record blood pressure in neonates: A prospective observational study.

Aim: To assess the usefulness and efficacy of pulse oximetry (disappearance/reappearance of plethsmographic waves) as a method of non-invasive blood pressure monitoring in neonates. Objective: To investigate the reliability of the plethysmographic wave form of the pulse oximeter to measure the systolic blood pressure. Study Setting: A prospective observational study was done to assess usefulness and efficacy of pulse oximetry (disappearance/reappearance of plethysmographic waves) as a method of non-invasive blood pressure monitoring in neonates. Material and
Methods: The study was conducted among 500 neonates to investigate the reliability of the plethysmographic waveform of the pulse oximeter to measure the systolic blood pressure as it is a easy way to perform and non invasive. Statistical Analysis Used: The results will compare and analyse statistically by Pearson correlation co-efficient. Regression modeling will carried out to explain the relationship of non-invasive blood pressure with mean DP and RP and attempted to predict the non-invasive blood pressure from mean DP/mean RP.
Results: The study results revealed that NIBP systolic and diastolic both correlated with DP and RP of pulse oximetry plethysmograph.
Conclusion: Study concluded that pulse oximetry is a reliable tool in measuring blood pressure in neonates (appearance and disappearance of plethysmogram). Copyright:

Introduction

Measuring blood pressure is of pertinent importance in managing of newborn infants with or without comorbidities, congenital disorders, and/or born preterm. Numerous determinants make blood pressure measurement and interpretation a hurdle in this age group of patients such as variable arm size, differences in gestational age and weight, and audibility issues related to Korotkoff sounds.[12]

In neonates, additional care has to be taken to interpret blood pressure values. However, the most precise, intra-arterial blood pressure measurement is pricey and not available in all clinical settings. It involves entering an artery, strict asepsis, and costly equipment for recording. Even though the measures are accurate, the complications and efforts are tedious.

When considering the standard non-invasive blood pressure (NIBP), automated oscillometric measurement has been used for decades.[345] Finding out arterial blood pressure with the help of pulse oximetry was done by monitoring the disappearance of visual display which takes place on blood pressure cuff inflation, when the reappearance of visual display upon cuff deflation that also is noted, and value is determined by averaging the two ruled out values.[6]

A study was conducted among 46 neonate patients who have undergone cardiac surgery in Seattle to monitor BP using pulse oximeter waveform change. Researchers compared pulse oximeter waveform with an oscillometric measurement and the gold standard, intra-arterial measurement. Simultaneous pressure level measurements were obtained from the blood vessel tubing, the oscillometric device, and therefore the pulse measuring system. Pulse measuring system measurements were obtained with a pressure level cuff proximal to the measuring oximeter probe. They concluded that pulse oximeter waveform change is an accurate and reliable way to measure blood pressure in children non-invasively and is superior to the oscillometric method for small patients.[7]

The technical hurdles of measuring and documenting blood pressure in newborn newborns are significant. Direct measurements from an artery are certainly the most accurate method but have obvious limitations, particularly if repeated observations over a period of hours or days are required. It involves entering an artery, strict asepsis, and expensive equipments for recording. Repeated measurements by indirect means are at best time consuming and tiring for both the baby and observer and at worst upsetting to the baby and, therefore, inaccurate and valueless. Many ingenious methods of indirectly measuring blood pressure have been devised, but all of them have their limitations.[8]

Pulse oximetry is reported as a useful technique to measure systolic blood pressure in newborn infants; oscillometry had the poorest agreement with Doppler findings to detect hypotension.[9] Literature portraying aforementioned findings is scarce in Indian context. In home health monitoring, information on blood arterial oxygen saturation (SpO2) is vital. We also need to figure out what influences the SpO2 measurement. The limits of SpO2 measurement pale in comparison to the benefits of pulse oximeters. Pulse oximeters are widely used and well-known gadgets. They are, however, extremely sensitive to the conditions at the measurement location, as well as other factors and artefacts. As a result, obtaining a high-quality signal is difficult. Family care physicians and primary care physicians are prone to encounter situations to deal with neonatal emergencies. The awareness about alternative measures in obtaining cardinal BP measures of neonates obviously will help them to tackle the emergency to some extend until further reference.[10] Very few studies have been conducted globally in this concern and scarce amount of studies were published within the country, which spearheaded the researcher to conduct this study.

Materials and Methods

This study adopted a quantitative approach using a prospective observational study design. Study subjects were 500 neonates admitted over 1 year and were recruited to the study, using a non probability sampling technique. Neonates, both inborn and out born, was included for the study. Consent was obtained from the parents of study subjects, IEC approval, and setting permission was also availed prior to the study. Sphygmomanometer used to compare with values of waveform measures are calibrated according to the norms.

Brief procedure

A blood pressure cuff of appropriate size (connected to sphygmomanometer) will be tied around the limb. Pulse oximetry probe (NELLCOR) will be applied to the finger/toe of the same limb. No preference for any specific limb to measure the BP will be shown. The pulse oximeter mode will be set to display continuous plethysmographic wave pattern. When a stable plethysmographic wave is obtained, the BP cuff will be inflated slowly by 2 mm Hg increments. The point of disappearance of the plethysmogram wave form will be noted (DP). Pressure will be further raised by 20 mm Hg quickly, and then reduced slowly by increments of 2 mm Hg. The point of reappearance of plethysmogram wave form will be noted (RP). Three readings will be repeated. Mean of DP and RP will be calculated. Simultaneously, BP will taken by NIBP method. The results will be compared and analyzed statistically by Pearson correlation coefficient. Regression modeling will be carried out to explain the relationship of NIBP with mean DP and RP and attempted to predict the NIBP from mean DP/mean RP.

Results

Sociodemographic variables

All study subjects were full term normal or CS delivered. Preterm babies and babies with any kind of genetically affected disorders or other comorbidities were excluded from this study. Regarding gender distribution, subjects were more or less belonging to both genders in same proportion. Table 1 depicts Mean DP, RP, NIMP MAP, and Blood Pressure observed.

Table 1

Descriptive statistics

	n	Minimum	Maximum	Mean	Std. deviation
Mean DP	500	42.00	106.67	76.60	11.78
Mean RP	500	30.00	97.33	54.64	12.39
NIBP Systolic	500	31.00	114.00	74.30	13.16
NIBP Diastolic	500	16.00	74.00	43.07	9.40
NIBP mean arterial pressure	500	21.00	97.00	53.63	12.40

Table 2 showing the correlation between Mean DP Vs NIBP systolic BP, that is, r = 0.317, P < 0.001; Mean DP vs NIBP diastolic BP, that is, r = 0.255, P < 0.001. Similarly, it is showing correlation between Mean RP vs NIBP systolic, that is, r = 0.282, P < 0.001; Mean RP vs NIBP diastolic BP, that is, r = 0.259, P < 0.001.

Table 2

Correlation between Mean DP vs NIBP systolic BP

Correlations (Pearson Correlation)
	NIBP systolic	NIBP diastolic	NIBP mean arterial pressure
Mean DP	0.317(**)	0.255 (**)	0.252 (**)
Mean RP	0.282 (**)	0.259 (**)	0.274 (**)

**Correlation is significant at the 0.01 level (2-tailed).

Tables 3 and 4 showing significant linear relationship of NIBP systolic BP on Mean DP, y = 47.17 + 0.354 × mean DP, where y = mean systolic BP. F = 55.66, P < 0.001.

Table 3

Regression model summary (a)

Model	R	R 2	Adjusted R2	Std. error of the estimate
1	0.317 (a)	0.101	0.099	12.492

aPredictors: (Constant), Mean DP. bDependent Variable: NIBP Systolic

Table 4

Regression analysis (Coefficients (a))

Coefficients (a)
Model	Unstandardized coefficients		Standardized coefficients	t	Sig.	95% Confidence interval for B
	B	Std. error	Beta			Lower bound	Upper bound
1
(Constant)	47.171	3.679		12.823	0.000	39.943	54.399
Mean DP	0.354	0.047	0.317	7.461	0.000	0.261	0.447

aDependent Variable: NIBP Systolic

Tables 5 and 6 showing significant linear relationship of NIBP systolic BP on Mean RP, y = 57.91 + 0.3 × mean RP, where y = mean systolic BP. F = 43.10, P < 0.001.

Table 5

Regression model summary (b)

Model	R	R 2	Adjusted R2	Sth. error of the estimate
1	0.282(a)	0.080	0.078	12.636

aPredictors: (Constant), Mean RP. bDependent Variable: NIBP Systolic

Table 6

Regression analysis (Coefficients (b))

Model	Unstandardized coefficients		Standardized coefficients Beta	t	Sig.	95% Confidence interval for B
	B	Sth. error				Lower bound	Upper bound
1
(Constant)	57.914	2.559		22.634	0.000	52.887	62.941
Mean RP	0.300	0.046	0.282	6.565	0.000	0.210	0.390

aDependent Variable: NIBP Systolic

Tables 7 and 8 showing significant linear relationship of NIBP diastolic BP on Mean DP, y = 27.47 + 0.20 × mean DP, where y = mean systolic BP. F = 34.695, P < 0.001.

Table 7

Regression model summary (b) (Mean DP and NIBP Diastolic)

Model	R	R 2	Adjusted R2	Sth. error of the estimate
1	0.255(a)	0.065	0.063	9.102

aPredictors: (Constant), Mean DP. bDependent Variable: NIBP Diastolic

Table 8

Regression analysis (Coefficients (b))

Model	Unstandardized coefficients		Standardized coefficients Beta	t	Sig.	95% Confidence interval for B
	B	Sth. error				Lower bound	Upper bound
1
(Constant)	27.465	2.680	10.247	0.000	22.199	32.731
Mean DP	0.204	0.035	0.255	5.890	0.000	0.136	0.272

aDependent Variable: NIBP Diastolic

Tables 9 and 10 showing significant linear relationship of NIBP diastolic BP on Mean RP, y = 32.32 + 0.197 × mean RP, where y = mean systolic BP. F = 35.88, P < 0.001.

Table 9

Regression model summary (b) (Mean RP and NIBP Diastolic)

Model	R	R 2	Adjusted R2	Sth. error of the estimate
1	0.259(a)	0.067	0.065	9.092

aPredictors: (Constant), Mean RP. bDependent Variable: NIBP Diastolic

Table 10

Regression analysis (Coefficients (b))

Model	Unstandardized coefficients		Standardized coefficients Beta	t	Sig.	95% Confidence interval for B
	B	Sth. error				Lower bound	Upper bound
1
(Constant)	32.315	1.841	17.553	0.000	28.698	35.933
Mean RP	0.197	0.033	0.259	5.990	0.000	0.132	0.261

aDependent Variable: NIBP Diastolic

Tables 11 and 12 showing significant linear relationship of NIBP mean arterial pressure on Mean DP, y = 33.30 + 0.27 × mean DP, where y = mean AP. F = 33.84, P < 0.001.

Table 11

Regression model summary (b) (Mean DP and NIBP MAP)

Model	R	R 2	Adjusted R2	Sth. error of the estimate
1	0.252(a)	0.064	0.062	12.007

aPredictors: (Constant), Mean DP. bDependent Variable: NIBP Mean Arterial Pressure

Table 12

Regression analysis (Coefficients (b))

Model	Unstandardized coefficients		Standardized coefficients Beta	t	Sig.	95% Confidence interval for B
	B	Sth. error				Lower bound	Upper bound
1
(Constant)	33.301	3.536	9.418	0.000	26.354	40.248
Mean DP	0.265	0.046	0.252	5.817	0.000	0.176	0.355

aDependent Variable: NIBP Mean Arterial Pressure

Tables 13 and 14 showing significant linear relationship of NIBP mean arterial pressure on mean RP, y = 38.64 + 0.27 × mean RP, where y = mean AP. F = 40.48, P < 0.001.

Table 13

Regression model summary (b) (Mean RP and NIBP MAP)

Model	R	R 2	Adjusted R2	Sth. error of the estimate
1	0.274(a)	0.075	0.073	11.933

aPredictors: (Constant), Mean RP. bDependent Variable: NIBP Mean Arterial Pressure

Table 14

Regression analysis (Coefficients (b))

Model	Unstandardized coefficients		Standardized coefficients Beta	t	Sig.	95% Confidence interval for B
	B	Sth. rror					Lower bound	Upper bound
1
(Constant)	38.638	2.416	15.991	0.000	33.890	43.385
Mean RP	0.274	0.043	0.274	6.363	0.000	0.190	0.359

aDependent Variable: NIBP Mean Arterial Pressure

Discussion

Accurate BP measurement is critical in neonates, most common cause for blood pressure fluctuations are physiological variation, anatomical variation, as well as cuff compression variation. The requirements of successful blood pressure monitoring are that the method should be easy to set up, reliable, and give continuous information or enable measurements to be made at frequent intervals with minimal disturbance to the baby.

In this study, NIBP systolic had better correlation with DP (r = 0.317) P < 0.001 compared with RP (r = 0.282) [Figures 1 and 2, respectively]. This study’s findings are consistent with a study conducted among adults and neonates using the same methodology that uses pulse oximeter signal disappearance and reappearance as an alternative method.[11] Langbaum investigated the precision of the plethysmographic waveform of a pulse oximeter in gauging systolic blood pressure in sick neonates in a study. Pulse oximetry waveform analysis is a simple and accurate method to quantify blood pressure in newborns, and it is much more accurate than the oscillometric method.[12]

Figure 1

Relationship between DP and NIBP systolic along with 95% confidence limits

Figure 2

Relationship between RP and NIBP systolic along with 95% confidence interval

Another two studies conducted in Indian setting also reported the significant accuracy of using pulse oximeter in comparison with other NIBP methods.[1314] Studies reported that blood pressure measurement among Takayasu’s arteritis patients also ruled out that this method is a useful alternative for this clinical situation, for which the oscillometric device did not work.[15] However, some systematic reviews warrant further research in this area to validate and develop oscillometric methodology with enhanced accuracy.[16]

Despite the fact that neonates did not become sick or badly impacted during corona virus induced disease (COVID-19), the necessity for monitoring was critical. One potential way to mitigate the likelihood of complications in patients is to have those diagnosed with COVID-19 but not symptomatic enough to necessitate admission monitor their arterial oxygenation at home using pulse oximetry and present for care if they show signs of hypoxemia. Although pulse oximetry’s ease of use and relatively inexpensive make it an enticing prospect for recognizing problems early on, there are key factors with pulse oximetry that patients and providers may not be aware of, which can impede the successful implementation of such monitoring tools. The relevance of basic pulse oximetry use is also highlighted in this study.[17]

The main implication of this study is to provide a strategy for clinicians, researchers, and industry to conduct future clinical research studies in a consistent, evidence-based manner to improve the quality, accuracy, and applicability of future neonatal hemodynamic studies. Study portrays use of pulse oximetry which is a reliable tool in measuring blood pressure in neonates. Studies related to this topic are scarcely published in Indian context in the last two decades, hence it makes a pertinent finding.

Key message

• In neonates, information on blood arterial oxygen saturation (SpO2) is critical.

• Pulse oximetry is a pertinent technique to measure systolic blood pressure in newborn infants.

• Pulse oximetry is a reliable tool in measuring blood pressure in neonates.

• Family physicians need to be aware about this simple and straight forward measure of blood pressure of neonates.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.