PULMONARY AND CRITICAL CARE MEDICINE
Pulmonary medicine in America has its roots in the tuberculosis era of the early part of this century as a specialty known initially as phthisiology from "phthisis" or "consumption". It gained the science of mechanically-assisted breathing in the early high-altitude flights of World War II and used it in earnest in the paralyzing polio ear of the early 1950's. Since then the influence of tobacco on the lungs of Americans has dominated the day-to-day workings of the pulmonologist as smoking-induced emphysema, progressing to chronic and sometimes acute respiratory insufficiency, now affects some tens of millions in this country. The pulmonologist is considered an expert in the diagnosis and care of all forms of respiratory distress, both in and out of the hospital; such problems include asthma, chronic bronchitis, pneumonia, pulmonary thromboembolic disease, occupational lung disease, inhalation of toxic substances, near-drowning, chest pain, chronic cough and the non-surgical aspects of chest trauma. Most of the pulmonologists in this country are skilled in fiberoptic bronchoscopy, an endoscopic technique for visualizing and sampling the central airways; it is used in both inpatients and outpatients without general anaesthesia to diagnosis cancer, persistent bleeding, difficult infections and other inflammatory problems in the lungs.
Critical care medicine is a multidisciplinary specialty with overlapping areas of knowledge and responsibility from anaesthesia, surgery and internal medicine. There are a few purely critical care specialists in the United States but most of those with board certification in critical care hold previous certification in pulmonary medicine. A smaller number are certified in cardiology, infectious diseases, emergency medicine, anaesthesia, general surgery, trauma surgery, thoracic surgery and a few other specialties. In a few hospitals critical care specialists are granted the responsibility for care of all intensive care unit patients; in most hospitals, however, they are just available for consultation as is true of any other specialty.
Critical care specialists, sometimes referred to as "intensivists" see patients with the highest care needs in the hospital, those requiring eight or, more commonly, twelve to twenty-four nursing hours per day (A single nurse can care for two patients who are deeded to require twelve hours of care daily, a patient requiring twenty-four hours of care daily must be the only charge of a single nurse or nurses in shifts). Such patients are almost universally cared for in intensive care units (ICU's), coronary care units (CCU's) which specialize more in the intensive care of heart patients, though their beds (and nurses) may be used for non-cardiac patients when other ICU beds are filled and are considered critically ill if their vital signs are unstable or likely to become unstable. This broad definition means that patients with many different types of problems may require ICU care including those with respiratory failure, liver failure, shock, septicemia, head trauma, peritonitis, post-operative instability, etc. In small hospitals one ICU may suffice for all critically ill patients (and may even double as a CCU as well); larger hospitals may require multiple ICUs with subspecialization such as a medical ICU, a neurological ICU, a surgical ICU or even neurosurgical, anaesthesia or cardiovascular surgery ICUs.
Medical-Legal Problems In Pulmonary And Critical Care Patients
Shortness Of Breath:
Since pulmonary patients by definition have or may develop problems breathing it is not surprising that many medical-legal issues derive from disagreement over the promptness or appropriateness of diagnosis and management of shortness of breath. Like pain, shortness of breath is a subjective symptom, the severity of which is determined by the patient and communicated to the physician --the physician cannot "feel" or measure the degree of shortness of breath. Available to the physician since the late 1980s has been pulse oximetry, a rapid, simple, noninvasive measure of oxygen saturation at the bedside. Oxygen saturation has been termed "the fifth vital sign" (after pulse rate, respiratory rate, blood pressure and body temperature) and failure to monitor it, in situations where hypoxemia, or oxygen desaturation is considered likely may lead to legal dispute. Direct measurement of blood oxygen level is more precisely performed with an arterial blood gas (ABG) which is invasive (requiring a potentially-painful arterial puncture) and takes a bit longer (a few minutes for the result in most hospitals, as compared to instantaneously with pulse oximetry). But an ABG gives much more information than pulse oximetry; besides the partial pressure of oxygen in arterial blood (PaO2) an ABG measures the partial pressure of carbon dioxide (paCO2) the pH and, depending on the equipment, the oxygen saturation, the met-hemoglobin concentration and the carboxy-hemoglobin concentration (a direct measure of the amount of carbon monoxide in arterial blood - useful in carbon monoxide poisioning and heavy smoking) of arterial blood.
The evaluation of shortness of breath and the subsequent risk of respiratory failure is complex but usually involves a detailed history, a physicial examination, a chest x-ray, pulmonary function tests (PFTs) - testing measuring variously the static volumes, expiratory flow rates and gas diffusing capacity of the lungs and possible some measure of oxygenating ability as weith an ABG or pulse oximetry. ABGs are sometimes reported with PFTs. In additon, when thromboembolic disease is suspected, a ventilation-perfusion (V/Q) lung scan may be necessary, when structural abnormalities in the chese are suspected, a computerized tomographic (CT)-scan of the chest may be used. Abnormalities seen on chest x-ray or CT scan may prompt fiberoptic bronchoscopy for tissue sampling or surgery itself may be recommended. Legal issues arise when patients or families feel that diagnosis and/or treatment has not been pursued rapidly enough or appropriately.
Failure of the respiratory system to perform its role may be an acute problem, as in severe pneumonia in an otherwise normal patient, a chronic problem as in the emphysema patient with advanced destructive changes of the lungs and marginal pulmonary function characterized as "chronic respiratory insufficiency" or an acute problem added to a chronic one, as with a patient with pulmonary fibrosis, a chronic disorder involving scarring of the lungs, who experiences a myocardial infarction, or heart attack, and develops pulmonary edema as a result. In all of these cases, respiratory failure may be heralded by worsening hypoxemia (falling oxygen level, as demonstrated by oximetry or ABGs), increasing paCo2 and falling pH of the arterial blood. The combination of elevated paCO2 and falling pH is referred to as acute respiratory acidosis and is an important sign of acute respiratory failure.
When the respiratory system is failing the decision to institute mechanical assistance to breathing must be made. Ethical questions of whether to begin or to withhold mechanical ventilation take into account the age and other concomitant illnesses of the patient, and ideally the stated or implicit wishes of the patient, the family and/or the person holding durable power of attorney for health care issues. Unfortunately these data are not always present or clear and legal questions continue to arise related to disagreements between patients, families and caregivers as to appropriateness of ventilatory support.
When mechanical ventilation is considered warranted an invasive procedure called endotracheal intubation must be performed. This involves passage of a flexible, thick plastic cuffed tube through the nose or mouth into the trachea (the endotracheal tube or ET tube) to establish an airway for respiratory assistance. Physicians who are traditionally trained in intubation are pulmonologists, anaesthesiologists and emergency physicians, but in many hospitals the level of training of respiratory therapists (hospital technicans who are trained to deliver aerosol therapy, manage mechanical ventilators and perform pulmonary functions tests including pulse oximetry and measuring ABGs) is such that they routinely perform simple intubations. Invasive as it is, intubation carries risks for the patient, including damage to nasopharyngeal or oropharyngeal mucosa, vocal cord damage, bleeding and even pneumothorax.
Mechanical ventilation itself is an unnatural event. The inspired air/oxygen mix is given under positive pressure, rather than inhaled by negative pressure as occurs normally. Positive pressure to the lungs and thorax carries the risk of barotrauma, or pressure-related damage to the lungs; this can include pneumothorax, and if untreated can be fatal. The air/oxygen mix delivered to the patient must be monitored frequently to assure that the proper degree of oxygenation of arterial blood is being achieved and that excessive respiratory acidosis is avoided. Arterial blood gases are used frequently, and, to allow frequent arterial sampling without the pain of frequent punctures, an arterial cannula or catheter may be placed --usually in the radial artery of one wrist. Again in some hospitals this is done only by physicians, but in some is done by physician's assistants or respiratory therapists. Inherent risks of placement of an arterial catheter include compromise of blood flow to the digits, sometimes resulting in tissue loss, even autoamputation of a digit.
Prolonged mechanical ventilation carries other risks. The ET tube by necessity bypasses the protective mechanisms of the larynx, making aspiration of liquids, oropharyngeal bacteria, etc., more likely, substantially increasing the odds of developing pneumonia if it is not already present (ICUs themselves harbor certain pathogenic bacteria, impossible to eradicate and most patients who are intubated are colonized, if not infected, with these bacteria with a few days of beginning mechanical ventilation). The intake and output of patients on ventilatory support must be precisely monitored, as too much or too little intravascular volume may drastically affect both blood pressure and kidney function. Sedation is a critical issue in this setting, too, as too little sedation will not allow the patient to tolerate mechanical ventilation and too much may cause falling blood pressure, intestinal obstruction and mental status changes. Total muscular paralysis is occasionally called for in patients who cannot otherwise tolerate needed mechanical ventilation; under such paralysis, accidential disconnection from mechanical ventilation may be rapidly fatal and must be guarded against carefully. Prolonged medical paralysis sometimes does not reverse quickly when the medications are stopped and prolonged muscle weakness (sometimes dramatically prolonging the need for mechanical ventilation itself) may ensue. This is a well-recognized complication of paralytic medication; the risk is lessened but not eliminated by the use of monitors that measure muscle response to electrical stimuli.
Deciding when the patient is well enough to be removed from the ventilator is not always easy, this is called weaning and when difficult can involve attempting different modes of ventilation and utilizing various measures of ventilatory independence in addition to ABGs. It is not unusual among the best of physicians to misjudge a patient's readiness for extubation, resulting in the need for reintubation and reinstitution of ventilatory support and then restarting weaning again.
Clots or thromboses that originate in the thighs, during surgery or trauma or sometimes spontaneously, become emboli (singular, embolus) if they break off and float through the venous circulation, to lodge in the pulmonary arterial system. Too many or too large emboli can cause shortness of breath, chest pain, hemoptysis (coughing up blood), tachycardia (rapid heartbeat), inflitrates on chest x-ray, hypoxemia, hypotension (low blood pressure) and even sudden death. The diagnosis first requires consideration of the event; many legal cases have occurred when autopsies show pulmonary emboli and the entity was not even considered during life. A V/Q lung scan gives an approximated risk level of the diagnosis but often a pulmonary arteriogram is required to prove embolization has occurred. This is an invasive procedure, usually done by a radiologist, with the inherent risks of intravascular puncture and constrast dye exposure. pulmonary embolic disease is treated with intravenous anticoagulation in the hospital and usually prolonged oral anticoagulants afterwards. These carry the risks of bleeding if given in too high doses and of recurrent thrombosis and embolization if given in too small ones.
Asthma And Emphysema:
Asthma and emphysema are disorders on a continuum from very mild to severe and involve shortness of breath which may be episodic or unremitting. A timely response to patient's complaints of worsening shortness of breath is required; frequently new infections (a cold, bronchitis, even pneumonia) may herald worsening of the shortness of breath and must be recognized. Both asthma and emphysema require fine-tuning with bronchodilator and steroid medications all of which carry their own risks.