Fig 1.
Oxygenation index (OI) trend in enrolled patients.
Hatched line represents mean OI in neonates with no lung disease (NLD) and T-bars represent their standard deviation. Open triangles and full grey circles represent the two neonates with meconium aspiration syndrome (MAS). Abbreviations: MAS: meconium aspiration syndrome; NLD: no lung disease; OI: oxygenation index.
Table 1.
Basic characteristics of all enrolled neonates.
Data are expressed as mean (standard deviation) or numbers (%). NLD neonates were intubated for delivery room resuscitation and kept ventilated to reduce their metabolic demand during hypothermia, according to our routine clinical protocol. All patients were discharged home with no respiratory support and with normal neurological exam and brain magnetic resonance imaging.
Fig 2.
Illustrative case of a patient studied through a complete CBS experiment.
Surfactant biophysical properties were studied both under initial adsorption (A) and compression-expansion dynamic cycling (B), mimicking the spontaneous respiratory cycles, at two temperatures (37°C and 33.5°C). Only one of three different replicates of the whole experiment is shown. Acronyms indicate samples obtained before (pre), during (24h, 48h, 72h) and after (post) WBH. Dynamic cycles n°1, 10, and 20 are depicted by black and red circles and green triangles, respectively. This patient had perinatal asphyxia encephalopathy but was not affected by MAS. Abbreviations: γ: surface tension (in mN/m); CBS: captive bubble surfactometry; MAS: meconium aspiration syndrome; WBH: whole body hypothermia.
Fig 3.
Adsorption is measured in terms of surface tension (γ) before and after the injection of surfactant for the following 5’. Panel A and B show experiments at 37°C and 33.5°C, respectively. Different symbols indicate samples obtained before (pre), during (24h, 48h, 72h) and after (post) WBH. T-bars represent the standard deviation of measurements obtained in 10 patients (8 NLD and 2 MAS). Abbreviations: γ: surface tension (in mN/m); MAS: meconium aspiration syndrome; WBH: whole body hypothermia.
Table 2.
Surface tension (γmin) in mN/m achieved during each time point of the initial adsorption from the injection of surfactant (t = 0 s) to the end (t = 300 s) of the experiment. Data are expressed as mean (standard deviation).
Fig 4.
(A) Dynamic compression-expansion cycling. Black and grey columns represent the minimum surface tension (γmin) expressed as mN/m during the whole dynamic experiments at 37°C and 33.5°C, respectively. T-bars represent the standard deviation of measurements obtained in 8 NLD patients. X-axis indicates timepoints: before (pre), during (24h, 48h, 72h) and after (post) WBH. No significant differences are evident over time during WBH within the same patients, neither testing at 37°C, nor at 33.5°C. The black arches indicate the significant differences at the paired comparison between data obtained at the two different temperatures. The respective p-value is also showed. γmin at the two temperatures is not significantly different before WBH, at 24h and 48h of hypothermia. (B) Compressibility. Black and grey columns represent the slope value (ΔΠ/ΔA) expressed as mN/m of the 20th dynamic cycle obtained at 37°C and 33.5°C, respectively. The value was calculated as the slope of the line passing through the minimum and maximum points of the area generated by 20th compression cycle. T-bars represent the standard deviation of measurements obtained in 8 NLD patients. X-axis indicates timepoints: before (pre), during (24h, 48h, 72h) and after (post) WBH. No significant differences are evident over time during WBH within the same patients, neither testing at 37°C, nor at 33.5°C. The black arches indicate the significant differences at the paired comparison between data obtained at the two different temperatures. The respective p-value is also showed. ΔΠ/ΔA at the two temperatures is not significantly different before WBH, at 24h and 48h of hypothermia. Abbreviations: γ: minimum surface tension (in mN/m); MAS: meconium aspiration syndrome; WBH: whole body hypothermia; ΔΠ/ΔA: slope value.
Fig 5.
Correlation plots between cholesterol amount expressed as percentage with respect to PC choline (Chol/choline) and minimal surface tension (γmin) achieved during dynamic cycles at 37°C (A) and 33.5°C (B). The dotted line shows the trend line of values dispersion. Correlation coefficients and p-values are also showed. Red and blue circles indicate MAS patient n.1 and n.2, respectively (filled circle: pre-hypothermia, empty circle: post hypothermia). No significant correlations are evident at the two temperatures, considering the whole population. Abbreviations: γ: minimum surface tension (in mN/m); Chol/Choline: cholesterol amount (in % with respect to total PC-derived choline).
Table 3.
Minimal surface tension, compressibility and cholesterol amounts of samples tested before (pre), during (24h, 48h, 72h) and after (post) WBH at 33.5°C and 37°C.
Data are expressed as mean (standard deviation).
Fig 6.
An illustrative dynamic compression-expansion cycling for the two patients with meconium aspiration syndrome before hypothermia and when the best surfactant performance is achieved during hypothermia.
Panel A and B represent patient 1 and 2, respectively. BAL sampling time-points are indicated as (pre), (48h) and (72h). Experiments were performed at 37°C and 33.5°C. Cycles number 1, 10, and 20 are depicted by black and red circles and green triangles, respectively. Oxygenation, gas exchange data, Δ (minimum surface tension—γmin) during the whole dynamic experiments between measurements tested at 37°C and 33.5°C, compressibility at the 20th cycle (ΔΠ/ΔA), chol/PC choline are shown for each time-point and each patient in the inserted tables. PaCO2 is expressed in mmHg, γmin and ΔΠ/ΔA are expressed as mN/m, cholesterol is expressed as % of surfactant PC. OI, P/F ratio, pH are dimensionless numbers. Abbreviations: γ: surface tension (in mN/m); MAS: meconium aspiration syndrome; OI: oxygenation index; P/F ratio: PaO2/FiO2; WBH: whole body hypothermia.
Table 4.
Basic characteristics of neonates with meconium aspiration syndrome.
Both neonates were severely ill and treated with aggressive ventilatory support, surfactant broncho-alveolar lavage followed by surfactant bolus (more details in the text). PPHN was treated with inhaled nitric oxide.