feature: Trend Detection & Alert Suppression Windows

2026-06-18 21:18:13 +08:00
parent e6f7989298
commit 3c54feb38a
31 changed files with 2751 additions and 18 deletions
@@ -0,0 +1,62 @@
+using StackExchange.Redis;
+
+public static class TrendCalculator
+{
+    // NEWS2-relevant codes that support trend detection.
+    public static readonly IReadOnlyList<string> TrendCodes = new[]
+    {
+        "HEART_RATE", "RESP_RATE", "SYSTOLIC_BP", "TEMP_C", "SPO2"
+    };
+
+    public static bool IsTrendCode(string observationCode) =>
+        TrendCodes.Contains(observationCode);
+
+    public static string HistoryKey(Guid encounterId, string code) =>
+        $"trend:{encounterId}:{code}";
+
+    public static RedisKey[] AllHistoryKeys(Guid encounterId) =>
+        TrendCodes.Select(c => (RedisKey)HistoryKey(encounterId, c)).ToArray();
+
+    /// <summary>
+    /// Computes rate of change (units per minute) between the oldest and newest
+    /// entries within the window. Returns null if fewer than 2 entries or window exceeded.
+    /// </summary>
+    public static decimal? ComputeRatePerMinute(
+        IReadOnlyList<TrendHistoryEntry> entries,
+        int windowMinutes)
+    {
+        if (entries.Count < 2) return null;
+
+        var newest = entries[^1];
+        var oldest = entries[0];
+
+        var deltaMinutes = (newest.RecordedAt - oldest.RecordedAt).TotalMinutes;
+        if (deltaMinutes <= 0 || deltaMinutes > windowMinutes) return null;
+
+        return (newest.Value - oldest.Value) / (decimal)deltaMinutes;
+    }
+
+    /// <summary>
+    /// Returns true if the rate exceeds the configured threshold.
+    /// For SPO2 and SYSTOLIC_BP, checks negative rate (decline) as clinically significant.
+    /// </summary>
+    public static bool ExceedsThreshold(
+        string observationCode,
+        decimal ratePerMinute,
+        decimal thresholdPerMinute) =>
+        observationCode switch
+        {
+            "SPO2" or "SYSTOLIC_BP" => ratePerMinute <= -thresholdPerMinute,
+            _ => ratePerMinute >= thresholdPerMinute
+        };
+
+    public static string DescribeTrend(
+        string observationCode, decimal ratePerMinute, decimal currentValue) =>
+        observationCode switch
+        {
+            "SPO2" or "SYSTOLIC_BP" =>
+                $"Rapid decline: {observationCode} falling at {Math.Abs(ratePerMinute):F2}/min (current {currentValue})",
+            _ =>
+                $"Rapid rise: {observationCode} rising at {ratePerMinute:F2}/min (current {currentValue})"
+        };
+}