FiO Ratio as an oxygenation parameter in

ORIGINAL ARTICLE Bali Medical Journal (Bali Med J) 2016, Volume 5, Number 2: 185-188 P-ISSN.2089-1180, E-ISSN.2302-2914

SpO2/FiO2 Ratio as an oxygenation parameter in pediatric acute respiratory distress syndrome

Published by DiscoverSys and Udayana University/Sanglah Hospital

Dinna Auliawati,1* Ida Bagus Gede Suparyatha,2 Dyah Kanya Wati,2 I Nyoman Budi Hartawan,2 Ida Bagus Subanada2

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ABSTRACT Background: Acute respiratory distress syndrome (ARDS) diagnosis requires an invasive arterial blood sampling to reveal the PaO2 and calculate the PaO2/FiO2 ratio. SpO2/FiO2 ratio has been proposed as a non-invasive alternative to identify oxygenation parameter in pediatric patients with ARDS. Objective: To evaluate sensitivity and specificity of SpO2/FiO2 as an oxygenation parameter to detect ARDS. Methods: We conducted a cross-sectional at the Pediatric Emergency and Intensive Care Department, Sanglah General Hospital, Denpasar, Bali. The inclusion criteria were 1 month to 12 years old patient admitted to our PICU and diagnosed with mild or moderate to severe ARDS based on blood gas analysis which

fulfilled Berlin definition (ESICM 2012). The exlusion criteria were patient with a chronic lung disease and or a cyanotic heart disease. We collected SpO2/FiO2 ratio and calculated its sensitivity and specificity in detecting ARDS. Results: There were 124 patients enrolled. The most common diagnosis was diseases in respiratory system (62.1%). Based on ROC analysis to determine SpO2/FiO2 ratio needed to detect moderate to severe ARDS, the AUC was 0.76 (95%CI 0.677-0.843) and the cut-off point for SpO2/FiO2 ratio was 7 days 3 (2.4) Chest X-Ray Pneumonia 92 (74.2) Not pneumonia 11 (8.8) Normal 21 (17) Respiratory support CPAP, PEEP > 5 cmH2O 49 (39.5) Ventilator, PEEP >5 cmH2O

1 (1)

Hematology

Variables

75 (60.5)

49.7 (20.9) 0.68 (0.2) 192.6 (65.8) 157.8 (59.7)

 

PaO2 was 123,5 (SD 45.9), mean PaCO2 49.7 (SD 20.9), and mean FiO2 0.68 (SD 0.2). Additionally, the mean PaO2/FiO2 ratio was 192 (SD 65.8) and SpO2/FiO2 157.8 (SD 59.7). The most duration from the onset of symptoms until the development of ARDS was 3-7 days (70.2%). Based on the severity, 50.8% suffered from mild ARDS. Most chest x-ray interpretation of subjects came out as pneumonia (74.2%). The respiratory support used by most subjects was ventilator with PEEP ≥ 5cmH2O (60.5%). The pulmonary function characteristics can be seen in Table 2. The curve shown in Figure 1 showed that SpO2/ FiO2 ratio has a good ability to predict mild ARDS. Best cut-off point for SpO2/FiO2 ratio lies under 196. Based on that cut-off point, sensitivity and specificity are calculated (validity test). According to the calculation result for sensitivity, specificity, PPV, and NPV of SpO2/FiO2, it was found that sensitivity of SpO2/FiO2 ratio in predicting moderate to severe ARDS is 88.5% and its specificity is 44.4% (See Table 3).

DISCUSSION Figure 1 ROC curve for SpO2/FiO2 ability to predict PaO2/FiO2 ratio < 200 (moderate to severe ARDS). has normal nutritional status. The diagnosis was grouped based on which organ system dysfunction causing an admission to our hospital, which 62.1% had a respiratory system dysfunction. The mean

Our sample age median was 5 month (IQR 2-19) and most of them were male (55%). It is similar to another study showing the incidence of ARDS among patients admitted to PICU was 2.6%, with the majority of the subjects was under 1 year old and male.12 A different study had a mean age of 3 years, with the male as the majority of patients.13 ARDS incidence varies between studies. One of the factors causing the variation is the difference in the

Published by DiscoverSys and Udayana University/Sanglah Hospital | Bali Med J 2016; 5 (2): 185-188 | doi: 10.15562/bmj.v5i2.338

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ORIGINAL ARTICLE

Table 3  Sensitivity, Specificity, PPV, and NPV of SpO2/FiO2 < 196 to predict moderate to severe ARDS ARDS (n) Variables

Moderate to severe

Mild

Sn (%)

Sp (%)

PPV (%)

NPV (%)

SpO2/FiO2< 196

54

35

SpO2/FiO2 >196

7

28

88.5 (77.8-95.3)

44.4 (31.9-57.5)

60.7 (49.7-70.9)

80 (63.1-91.6)

definition used in determining ARDS. This study applied the Berlin definition issued by the ESICM in 2012. Most ARDS in this study was the result of respiratory system disturbance (62.1%), with pneumonia as the dominating cause. A similar result was observed in a study by Bauer, et.al. in 2006, in which they found that pneumonia is the most common cause of ARDS.14 Additionally, the onset of symptoms found also supported our study, which was 3-7 days. Similarly, Barreira, et al., found that the median of time from the onset of symptom until development of ARDS was 3 days (IQR 2-5).6 In predicting moderate to severe ARDS, SpO2/ FiO2 ratio has a sensitivity of 88.5% and specificity 44.4%. It is important to find out which Berlin definition’s category and at what PaO2/FiO2 ratio value does the SpO2/FiO2 ratio correspond to. In our study, SpO2/FiO2 ratio of < 196 is equal to PaO2/ FiO2 ratio of < 200 in moderate to severe ARDS case. It shows that SpO2/FiO2 ratio can be used as an oxygenation parameter for ARDS. This finding is similar to a study by Khemani, et al, where the sensitivity and specificity for the SpO2/FiO2 ratio of 201 to determine ARDS were 84% and 78%, respectively.13 Whereas Bilan, et al., found that SpO2/FiO2 ratio of 181 has a sensitivity of 71% and a specificity of 82% to detect ARDS.

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STUDY LIMITATION

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The limitation of this study was that it did not consider conditions that might shift the oxyhemoglobin dissociation curve. Additionally, this study did not consider any slight variation in SpO2 estimation between the device of different brand and calibration status.

CONCLUSION The SpO2/FiO2 ratio can be used as an oxygenation parameter in ARDS patients.

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Published by DiscoverSys and Udayana University/Sanglah Hospital | Bali Med J 2016; 5 (2): 185-188 | doi: 10.15562/bmj.v5i2.338