A comparative study of clinical signs versus pulse oximetry for prediction of hypoxia in very severe pneumonia in children

INTRODUCTION

Pneumonia remains one of the leading causes of morbidity and mortality among children worldwide, particularly in developing countries. The World Health Organization (WHO) identifies pneumonia as a critical public health problem, as it accounts for 15% of all deaths of children under five years old. This grave statistic underscores the importance of prompt and accurate diagnosis and management of pneumonia, especially in its severe forms.¹

Very severe pneumonia, characterized by features such as central cyanosis, severe respiratory distress, and hypoxia, presents a significant challenge. Hypoxia, a critical and life-threatening condition in pediatric pneumonia, demands rapid detection and immediate therapeutic intervention to prevent fatal outcomes.² Traditionally, clinical signs such as rapid breathing, severe chest indrawing, and cyanosis are used to predict hypoxia. However, these clinical signs can often be subjective and influenced by inter-observer variability.³

In recent years, pulse oximetry has emerged as a pivotal tool in the objective assessment of hypoxia. This non-invasive method provides real-time, quantitative data on arterial oxygen saturation (SpO₂), offering a clear advantage over traditional clinical assessments. Nevertheless, despite its advantages, the widespread implementation of pulse oximetry in resource-limited settings is often hampered by cost and availability issues.^4,5

The urgency in improving pediatric care for pneumonia in low-resource settings has led to a growing body of research focused on comparing the effectiveness of clinical signs versus pulse oximetry in predicting hypoxia. Clinical signs, while cost-effective and widely used, may not always accurately predict hypoxia, which can lead to either underestimation or over-treatment of children with pneumonia.⁶

This study aims to conduct a comprehensive comparative analysis of the efficacy of clinical signs versus pulse oximetry in predicting hypoxia among children with very severe pneumonia. By understanding the reliability and accuracy of clinical signs in comparison to pulse oximetry, this research seeks to provide evidence-based recommendations that can be feasibly implemented in resource-constrained settings.⁷ Moreover, the implications of this study extend beyond clinical practice into the realms of public health policy and healthcare resource allocation. By delineating the capabilities and limitations of clinical signs and pulse oximetry, the study's findings could guide policymakers in resource allocation, particularly in under-resourced medical facilities where the burden of pneumonia is highest.⁸

Overall, given the high prevalence and significant risk of mortality associated with pediatric pneumonia, especially when complicated by hypoxia, this study is positioned to contribute valuable insights into the optimization of diagnostic strategies. The ultimate goal is to enhance the accuracy of hypoxia detection in children with very severe pneumonia, thereby improving treatment outcomes and reducing the global health burden of this critical disease.

METHODS

Study setting

The research was conducted at the department of pediatrics, SPMCHI Hospital, SMS Medical College, Jaipur.

Study duration

Data collection occurred from September 2019 to May 2020.

Study design

This was a hospital-based, cross-sectional comparative observational study.

Participants

The study included children aged 2 months to 5 years presenting with cough or difficulty in breathing, and clinical signs of very severe pneumonia according to F-IMNCI guidelines, admitted to SPMCHI Hospital.

Sample size

The sample size was determined using a 95% confidence level with an alpha error of 0.05, based on a predicted sensitivity of 91.2% for identifying hypoxia through clinical indicators (e.g., head nodding, age-specific tachypnea). With a prevalence of 50.9% hypoxia in severe pneumonia cases within the target age range, and an allowable error of 10%, the required sample was approximately 150 children.

Inclusion criteria

The study targets children aged 2 months to 5 years who are experiencing cough or difficulty in breathing accompanied by at least one of the following severe indicators: central cyanosis, severe respiratory distress (evidenced by a respiratory rate of ≥70/min, severe lower chest indrawing, head nodding, grunting, or stridor in a calm child), or an inability to drink due to respiratory distress.

Exclusion criteria

Children are excluded if they have a history of recurrent nebulization (three or more times), congenital heart disease, severe palmar pallor, cold skin with a capillary refilling time greater than 3 seconds, a weak and fast pulse, axillary temperature below 36°C, meningitis, severe dehydration, severe anemia (hemoglobin less than 7 g/dl), the need for ventilatory support, previous enrollment in the study, or if there is negative consent.

Methodology

Participants meeting the inclusion criteria were selected for further evaluation. Detailed clinical histories and vital signs were recorded for each child. Clinical signs indicative of very severe pneumonia, such as central cyanosis and severe respiratory distress, were meticulously documented. Oxygen saturation levels were measured using a Nonin 9590 Onyx Vantage Finger Pulse Oximeter. The study focused on assessing the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of these clinical signs against pulse oximetry, which served as the reference standard.

Statistical analysis

The study employed statistical software such as statistical package for the social sciences (SPSS) for conducting various tests. Chi-square and Fisher’s exact tests were used to compare proportions among categorical variables. For continuous variables, the student’s t-test (unpaired) was utilized for normally distributed data, and the Mann-Whitney U test was applied for non-normally distributed data. All data analyses were performed using statistical package for the social sciences (SPSS), while Microsoft excel was used for data entry and preliminary data management. Statistical significance was set at a p value of less than 0.05. Odds ratios and 95% confidence intervals, essential for quantifying the association between clinical risk factors and hypoxia, were calculated using SPSS. Diagnostic indices, including sensitivity and specificity, were computed with 95% confidence intervals using the exact binomial method (Clopper-Pearson) in SPSS.

RESULTS

This observational study evaluated 150 children aged 2 months to 5 years admitted with very severe pneumonia, focusing on the correlation between clinical signs and hypoxia. The distribution of the study subjects based on age and gender revealed that 67.3% (101/150) were in the 2-12 months age group, with a male predominance of 71.3% (107/150).

The prevalence of hypoxia differed significantly between age groups. In the younger cohort (2-12 months), 58.4% (59/101) were hypoxic compared to 40.8% (20/49) in the older cohort (>12 months). This difference was statistically significant (p=0.042), suggesting that younger children are at a higher risk of developing hypoxia.

Gender analysis showed no significant difference in hypoxia prevalence between males and females, with 55.8% (24/43) of females and 51.4% (55/107) of males exhibiting hypoxic symptoms (p=0.758). This indicates that gender does not play a critical role in the development of hypoxia among children with very severe pneumonia.

Respiratory rate was a critical indicator of hypoxia in our study. For children aged 2-12 months, a respiratory rate of ≥50 breaths per minute was observed in all hypoxic cases (59/59) with a sensitivity of 100% but a low specificity of 26.2%, indicating that while a high respiratory rate reliably indicates hypoxia, it also frequently suggests hypoxia in non-hypoxic children. As the threshold for respiratory rate increased, the sensitivity decreased to 93.2% for ≥60 breaths per minute and 61% for ≥70 breaths per minute, but the specificity increased significantly to 42.9% and 92.6%, respectively.

The high sensitivity of high respiratory rates suggests its utility as a diagnostic tool, though its specificity is variable. Thus, while respiratory rate is a valuable diagnostic marker, it should be used in conjunction with other clinical assessments to predict hypoxia more accurately.

*Statistically significant.

DISCUSSION

The current study critically evaluates the effectiveness of clinical signs and pulse oximetry in predicting hypoxia among children with very severe pneumonia. Our findings reveal that while clinical signs remain a fundamental aspect of initial assessments in low-resource settings, pulse oximetry significantly enhances diagnostic accuracy.⁹ In the analysis, age emerged as a crucial factor influencing the incidence of hypoxia, with younger children (2–12 months) more frequently hypoxic than older ones. This age-related susceptibility could be attributed to the physiological immaturity of the respiratory systems in younger children. Despite the observed age-related differences, no significant gender disparities were noted, indicating that physiological symptoms of severe pneumonia leading to hypoxia are consistent across genders in pediatric populations.^10,11

Pulse oximetry outperformed clinical signs in specificity and sensitivity, particularly at higher respiratory rate thresholds. This underscores the utility of pulse oximetry as a precise tool in confirming hypoxia, where clinical signs might only suggest its presence. However, the study also highlights the limitations of relying solely on respiratory rates as predictors of hypoxia; while a higher respiratory rate threshold (≥70/min) offers high specificity, it does so at the cost of reduced sensitivity. This finding is critical, as it suggests that while severe cases can be accurately identified, milder but clinically significant cases might be overlooked if pulse oximetry is not available.^12,13

Overall, our research supports previous studies indicating that clinical signs, though valuable, can lead to substantial variability in hypoxia diagnosis due to their subjective nature. The integration of pulse oximetry can mitigate this variability, providing a more standardized approach to assessing hypoxia.¹⁴

CONCLUSION

This study confirms the superiority of pulse oximetry over clinical signs in detecting hypoxia in children with very severe pneumonia. Given its higher accuracy, pulse oximetry should be considered an essential part of the diagnostic process in pediatric pneumonia, especially in settings where rapid and precise assessment of oxygenation is critical. The findings advocate for increased accessibility and use of pulse oximetry in resource-constrained environments, potentially influencing public health policies aimed at reducing childhood mortality from pneumonia.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

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