A nasogastric (NG) tube is a thin, flexible device inserted through the nose, down the throat, and into the stomach. This tube serves as a pathway for delivering liquid nutrition, fluids, and medications to individuals who are temporarily unable to swallow safely. It can also be used to remove stomach contents for decompression. While insertion is a common procedure in healthcare settings, misplacement into the respiratory tract—the trachea, bronchi, or lungs—is a highly dangerous error. If the tube enters the airway instead of the esophagus, it can lead to severe, life-threatening complications, especially if feeding is administered.
How NG Tubes Can Enter the Lungs
The insertion of a nasogastric tube is often performed using a “blind” technique, meaning the healthcare provider cannot visually guide the tube past the pharynx and larynx. The human airway and the esophagus are situated close to each other, sharing a common pathway at the back of the throat. This natural anatomy presents a vulnerability, making inadvertent misdirection a possibility, and the tube can mistakenly pass through the vocal cords into the trachea.
Several patient-specific conditions significantly increase the risk of this misplacement occurring. Patients who have a decreased level of consciousness or an altered mental status often have a compromised or absent gag reflex and a less effective cough mechanism. These protective reflexes are specifically designed to close the airway and redirect the tube toward the esophagus.
The presence of an endotracheal tube for mechanical ventilation can also increase the risk, as it may prevent the glottis from fully closing during the insertion process. Critical illness or anatomical changes, such as those following a stroke or surgery, can impair the patient’s ability to cooperate or swallow. In a small percentage of blind insertions, the tube may unintentionally enter the respiratory tract, sometimes reaching the smaller bronchial tubes or even the pleural space surrounding the lungs.
Observable Signs and Symptoms of Respiratory Placement
When a nasogastric tube is inserted into the airway of a conscious patient, the body’s protective mechanisms trigger immediate and often dramatic signs of distress. A violent, persistent cough or severe gagging is one of the most reliable indicators that the tube has entered the trachea instead of the esophagus. The tube itself acts as an irritant in the sensitive lining of the airway, causing this reflexive reaction.
The patient may also exhibit difficulty breathing, medically termed dyspnea, and a noticeable decrease in their oxygen saturation levels. A change in the patient’s voice, such as hoarseness or the complete inability to speak, occurs because the tube is passing through or near the vocal cords. In more severe cases, or if the tube is obstructing a significant portion of the airway, the patient’s skin may begin to show cyanosis, a bluish or grayish discoloration that signals poor oxygenation.
These overt signs may be absent in patients who are sedated, unconscious, or critically ill with an impaired neurological status. In these vulnerable populations, the absence of a cough or gag reflex means the tube can be misplaced without any immediate, visible warning. Therefore, reliance solely on patient comfort can lead to dangerous delays, making careful verification protocols even more important.
Acute Medical Risks of Feeding into the Lungs
The most catastrophic consequence occurs when feeding or medication is delivered through the misplaced tube. This action introduces foreign material directly into the delicate lung tissue, leading to a condition known as aspiration pneumonia or chemical pneumonitis. The high-osmolarity and nutrient-dense nature of enteral feeding formula is highly inflammatory to the lung’s alveoli and bronchial lining.
The introduction of formula triggers a rapid, severe inflammatory response, resulting in localized tissue damage and necrosis within the lung. This creates an environment where bacterial pneumonia can quickly develop, potentially leading to respiratory failure and sepsis.
If the tube has advanced past the main airways and punctured the lung tissue or the pleural membrane, air can leak out, causing a pneumothorax, or collapsed lung. Infusion of liquid feed into the pleural space can also result in a “nutrothorax” or hydrothorax, which is the accumulation of the feeding solution in the chest cavity. This fluid buildup compresses the lung, severely limiting its ability to expand and exchange oxygen, compounding the respiratory distress. Administering any substance before confirming tube position is considered a preventable medical safety error, often termed a “never event.”
Protocols for Verification and Safe Removal
To prevent the severe risks associated with misplacement, healthcare professionals must follow strict protocols to confirm the tube’s position before it is used. The gold standard for initial confirmation of NG tube placement is a chest X-ray, which allows for visual confirmation that the tube has followed the esophagus, crossed the diaphragm, and the tip rests safely in the stomach. The X-ray must be interpreted using specific criteria to ensure the tube avoids the contours of the bronchi and is not coiled in the respiratory tract.
A primary, bedside method involves testing the pH level of the fluid aspirated from the tube. Gastric aspirate from the stomach is highly acidic, typically registering a pH between 1 and 5.5. Fluid from the lungs or respiratory tract is generally more alkaline, often with a pH greater than 6. If the pH test result is inconclusive, outside the safe range, or if the healthcare provider cannot obtain an aspirate sample, a confirmatory chest X-ray is mandatory before the tube is used.
If misplacement into the lungs or airway is confirmed, the tube must be removed immediately to prevent further harm. The healthcare provider will stabilize the patient, provide supportive measures such as supplemental oxygen, and closely monitor for signs of respiratory compromise or infection. Patients who have had a substance administered into a misplaced tube may require antibiotics to treat aspiration pneumonia and aggressive supportive respiratory care to manage the resulting inflammation and fluid accumulation.