Phototherapy and Pulmonary Function Testing

1. Phototherapy and Pulmonary Function Testing Phototherapy in Neonatal Care Phototherapy is a therapeutic use of visible light to treat neonatal hyperbilirubinemia (jaundice) by converting unconjugated bilirubin in an infant’s skin into water-soluble isomers that can be excreted without needing full hepatic conjugation. Mechanism & Key Parameters ● The primary mechanism is a photochemical reaction: photons in the blue-green spectrum (typically 420–480 nm) are absorbed by bilirubin, converting it into isomers that the neonate can excrete more easily. ● The effectiveness depends on irradiance (amount of light per area), wavelength, distance between the light source and infant skin, and the surface area exposed. ● Common light sources include LED, fluorescent, halogen, or fiber-optic devices, with variations in beam geometry and heat output. Indications & Clinical Use ● Phototherapy is indicated when bilirubin levels exceed safe thresholds or when rising rapidly, to prevent neurotoxicity (kernicterus) in newborns. ● It is one of the most common interventions in neonatal units and has reduced the need for exchange transfusion. ● Treatment may last from less than 24 hours to several days, depending on the infant’s bilirubin kinetics and response. ● During therapy, infants’ temperatures, hydration, and bilirubin levels must be monitored to avoid complications such as dehydration or overheating. Risks, Side Effects & Considerations ● Phototherapy is generally safe, but some infants may get skin rashes, loose stools, or mild dehydration. ● A rare side effect known as “bronze baby syndrome” can occur in infants with a component of direct hyperbilirubinemia, causing grey-brown skin discoloration. The phenomenon is mostly cosmetic and reversible over weeks. ● Eyes must be protected during therapy to prevent light damage, typically via soft goggles or shields. ● Providers follow conservative exposure times and power settings, adhering to guidelines (e.g., ALARA principle) to minimize any unintentional photothermal or photomechanical damage.

2. Pulmonary Function Testing (PFT) Pulmonary Function Tests (PFTs) are noninvasive diagnostic tools that evaluate how well the lungs work by measuring airflow, lung volumes, and gas exchange. Core Tests & Metrics ● Spirometry is perhaps the most widely used PFT: the patient breathes into a mouthpiece to measure volumes such as forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁). ● Lung volume measurements (total lung capacity, residual volume) assess volumes that remain after complete exhalation or maximal inhalation. ● Diffusion capacity (DLCO) tests how effectively gases (e.g. oxygen) move from lung air into blood. ● Flow rates and forced expiratory flows (e.g. FEF₂₅–₇₅) assess smaller airway function. Indications & Clinical Utility ● PFTs help differentiate between obstructive lung diseases (e.g. asthma, COPD) and restrictive diseases (e.g. pulmonary fibrosis, neuromuscular weakness) by analyzing flow-volume relationships and lung volumes. ● They are used to monitor disease progression, response to therapy (e.g. bronchodilators), and guide management decisions. ● PFTs may be performed before major surgery or in patients with respiratory symptoms (e.g. dyspnea, cough) to assess lung reserve. Procedure & Patient Prep ● Patients may be asked to refrain from bronchodilators prior to the test (unless otherwise instructed), wear loose clothing, and abstain from heavy meals or exercise before testing. ● Nose clips are used so that breathing is via the mouth only, and proper sealing around the mouthpiece is crucial to avoid leaks. ● Multiple attempts are usually required to ensure reproducibility of results (e.g. three acceptable maneuvers). Interpretation & Safety ● Results are compared against predicted normal values based on age, sex, height, and sometimes race, expressed as percentage predicted. ● PFTs are generally safe; risks include transient dizziness, coughing, or shortness of breath during deep maneuvers.

3. ● They are contraindicated or deferred in certain conditions (e.g. recent thoracic surgery, unstable cardiovascular disease, recent eye surgery) due to the strain involved in forced breathing maneuvers.