def clean_capillary_refill_rate(v):
    """Clean the capillary refill rate (CRR) variable

    Args:
        v (pd.Series): Series containing all CRR values

    Returns:
        v (pd.Series): Series containing all cleaned CRR values
    """
    crr_map = {'Brisk': 0, 'Delayed': 1, 'Normal <3 secs': 0,
            'Abnormal >3 secs': 1}

    # Map strings to integers
    v = v.astype(str).apply(lambda x: crr_map[x] if x in crr_map else None)

    return v