ANÁLISIS ENCUESTA A POBLADORES DE SANTA CRUZ

Advances in pulmonary research continue to affect the therapeutic options available to patients with pulmonary diseases.³ Some of these are purely palliative, whereas others may be curative. The more common interventions, as well as some of the newer ones, are described briefly in the following sections.

MEDICAL MANAGEMENT

The medical management of pulmonary disease includes pharma-ceuticals, oxygen therapy, airway adjuncts, mechanical ventilation, bronchial hygiene and other physical therapy techniques, smoking cessation, pulmonary rehabilitation, and social services.

Pharmacologic Therapy

The various medications used to treat pulmonary disease are described in Chapter 5 (Pharmacology); however, oxygen therapy is presented here.

Oxygen Therapy

Oxygen therapy is indicated for the treatment of acute or chronic hypoxemia and can be administered via a variety of devices, which achieve different concentrations (or fractions) of inspired oxygen (FIO2), as indicated in Table 2-12. Alternatively, some patients with COPD on long-term oxygen therapy (LTOT) choose transtracheal oxygen (TTO) delivery via a microcatheter inserted into the anterior tracheal wall, which they feel is more comfortable and less conspicuous than supplemental oxygen via a nasal cannula.

• As with other medications, oxygen is prescribed to provide the proper dose that maximizes benefits while minimizing toxicity;

an increased dose may be indicated during exertion.

• Oxygen sources include compressed gas stored in a cylinder, liquid oxygen stored in a vessel similar to a thermos, and oxygen concentrators that extract oxygen from the air and con-centrate and store it. The first two can be used for ambulation;

however, compressed gas cylinders are bulky and heavy and liquid oxygen canisters, although small and lightweight, may not contain enough oxygen for longer periods of use.

• Oxygen-conserving devices in the form of demand delivery devices, or pulsed-dose systems, sense the onset of inspiration

before delivering a bolus of oxygen, which ceases during expi-ration, thus reducing oxygen wastage.

• Because therapeutic oxygen is stored with all water vapor removed, humidity is often added in order to prevent irritation of the pulmonary mucosa, particularly when flow is 5 L/min or more. In addition, when the upper airway is bypassed (e.g., endotracheal intubation or tracheostomy) or when flow rates exceed 10 L/min, the oxygen may be heated to increase its water vapor–carrying capacity.

• Large-scale clinical trials are needed to define which patients should receive LTOT (e.g., patients with mild, moderate, or severe hypoxemia) and under what conditions (e.g., exercise, airline flights, and sleep).¹⁵

• Heliox, a mixture of 80% helium and 20% oxygen, is sometimes used in emergency rooms and intensive care units for the treat-ment of acute respiratory distress associated with croup, asthma, COPD, bronchiolitis, and respiratory acidosis. Because helium is less dense than nitrogen, it reduces airway turbulence and thus airway resistance, increasing the delivery of oxygen to distal air-ways and decreasing the work of breathing.

The goals of oxygen therapy are to slow the progression of COPD, improve survival, reduce dyspnea, and increase exercise toler-ance by reducing or eliminating exercise-induced hypoxemia and TABLE 2-12: Approximate FIO2Achieved With Various Oxygen

Delivery Devices

Device Oxygen

Flow Rate FIO2

Nasal cannula* 1 L/min 0.24

2 L/min 0.28

3 L/min 0.32

4 L/min 0.36

5 L/min 0.40

6 L/min 0.44

Simple face mask 5-6 L/min 0.35

6-7 L/min 0.45

7-10 L/min 0.55

Partial rebreathing

mask 6-10 L/min 0.40-0.60^{{

Nonrebreathing mask 10 L/min About 0.60-0.80 Aerosol face mask 10-12 L/min 0.35-1.0^{ Venturi mask^} 4-10 L/min 0.24-0.50^jj

Data from Baum GL, Crapo JD, Celli BR, et al. Textbook of Pulmonary Diseases.

6th ed. Philadelphia: Lippincott-Raven; 1998; and Burton GG, Hodgkin JE, Ward JJ. Respiratory Care: A Guide to Clinical Practice. 4th ed. Philadelphia:

Lippincott Williams & Wilkins; 1997.

F^IO2, Fraction of inspired oxygen.

*Estimated F^IO2, assuming normal minute ventilation (typically measured during expiration,_V^E); values may be 10% lower, or more, with increased _VE.

{F^IO2depends on setting.

{Reservoir bag should always be at least one-third to one-half full on inspiration.

}Oxygen flow rates are minimums to be used with specific-sized orifice for desired F^IO2.

jjF^IO2depends on the size of the orifice or the entrainment ports, which vary among manufacturers.

26 CARDIOVASCULAR AND PULMONARY PHYSICAL THERAPY

desaturation. Medicare and other insurers generally cover the cost of oxygen therapy in patients with a PaO2of 55 mm Hg or less, or an oxy-gen saturation (SaO2) no greater than 88% while seated at rest or a PaO2of 56 to 59 mm Hg or Sa_O2of 89% in the presence of cor pulmo-nale or polycythemia. In these patients, survival benefits may be gained only if the oxygen is used continuously, 24 hours/day, and not just when dyspnea develops, so that PaO2remains above 60 mm Hg (SaO2,90%).²⁶In patients who desaturate only during activity (SaO2,88%), the use of supplemental oxygen during activity tends to reduce dyspnea and improve exercise.¹¹

The use of supplemental oxygen carries important implications for physical therapy in all clinical settings:

• If a patient requires oxygen at rest, he/she will definitely need it during exertion and all rehabilitation activities.

• Because the additional demands of rehabilitation activities may cause oxygen desaturation, physical therapists must be able to recognize the signs and symptoms of hypoxemia (see Table 6-13 on page 241).

• Patients with a history of lung disease, especially those with an FEV₁less than 50% or a DL_COless than 60% of the predicted normal value, are likely to exhibit oxygen desaturation during exertion and should have their oxygenation status monitored initially (see pages 17 to 18).

• A drop in oxygen saturation to less than 86% to 90% (chronic ver-sus acute disease, respectively) during activity indicates that the patient needs additional oxygen; an order to institute oxygen therapy or to increase the oxygen dose during exertion should be requested from the physician (be certain to return the flow back to resting level at the end of each treatment session).

• Home physical therapists should be aware of the oxygen ther-apy prescription for their patients and ensure that they are using their oxygen as prescribed.

Airway Adjuncts

There are a variety of different types of accessory airways, which may be used to maintain or protect a patient’s airway, to provide mecha-nical ventilation, or to facilitate airway clearance (Figure 2-18):

• An oral pharyngeal airway is a semirigid oral plastic tube, or open-sided channel shaped to fit the natural curvature of the soft palate and tongue, that holds the tongue away from the back of the throat and thus maintains the patency of the airway.

• A nasal pharyngeal airway, a soft latex or rubber tube inserted through the nose, is commonly used to maintain airway patency and allow nasotracheal suctioning with less mucosal trauma to the nares and pharynx.

• A laryngeal mask airway consists of a semirigid plastic tube with an inflatable rubber cuff with slits that is inserted in the posterior hypopharynx, displacing the tongue anteriorly while keeping the glottis open. Once inflated, it allows limited posi-tive-pressure ventilation, if needed, and permits insertion of an endotracheal tube via fiberoptic bronchoscopy.

• The endotracheal (ET) tube is a semirigid plastic tube inserted into the trachea via the mouth or nose (i.e., an orotracheal tube or a nasotracheal tube) to provide an airway, protect the lungs from aspiration, and allow mechanical ventilation. Adult ET tubes usually have a low-pressure, large-volume inflatable cuff near their distal end to prevent aspiration of secretions;

neonatal and pediatric tubes usually do not have cuffs because of the small size of the airways.

• A transtracheal catheter can be used to provide supplemental oxygen or jet ventilation in emergent situations when other approaches have failed and improvement in oxygenation is crit-ical. A microcatheter is inserted through the anterior tracheal wall with the tip lying just above the carina. It can also serve as an alternative way to provide long-term oxygen therapy.

• The tracheostomy tube, an artificial airway inserted into the trachea via an anterior cervical incision below the level of the vocal cords, is used in patients requiring prolonged mechanical ventilation and those with upper airway obstruc-tion, absence of protective reflexes, or a number of other problems; most have inflatable cuffs to prevent aspiration, which may be deflated to assess a patient’s ability to handle secretions. There are several types, as illustrated in Figure 2-19:

4 A standard tracheostomy tube, shown in Figure 2-18, has a neck flange, body, and usually a cuff; some have a removable inner cannula. Cuffed tracheostomy tubes are used primar-ily with positive-pressure ventilators to reduce the risk of aspiration. They are available in a variety of styles, sizes, and materials. Cuffless tracheostomy tubes permit speech in continuously ventilated patients who are not at risk for aspiration.

A B C D

Figure 2-18: Common airway adjuncts. A, Oropharyngeal tube. B, Nasopharyngeal tube. C, Oral endotracheal tube. D, Tracheostomy tube.

CHAPTER 2 44 Pulmonology 27

4 A fenestrated tracheostomy tube consists of a double nula with an opening in the superior aspect of the outer can-nula so that air can pass through the vocal cords and upper airway when the inner cannula is removed, the tracheal opening is plugged, and the cuff is deflated.

4 Speaking, or phonation, valves, such as the Passy-Muir valve, are one-way valves that can be attached to a standard tra-cheostomy tube during periods of free breathing; they open during inspiration only, while forcing exhalation through the vocal cords and upper airway, thus permitting speech.

4 The Montgomery T-tube is a bifurcated silicone rubber stent that is used to maintain patency of the airways in patients with tumors or injuries causing major airway obstruction.

4 A tracheostomy button is a short, straight, externally plugged tube extending from the anterior neck to the inner tracheal wall, which maintains the tracheal stoma for suc-tioning and emergency ventilation during weaning from prolonged mechanical ventilation.

Mechanical Ventilation

Patients with severe pulmonary dysfunction resulting from primary lung disease or secondary to other disorders often require ventila-tory support. The main indications for mechanical ventilation are acute respiratory failure (66% of patients, including those with acute respiratory distress syndrome, heart failure, pneumonia, sep-sis, complications of surgery, and trauma), coma (15%), acute exacerbation of chronic obstructive pulmonary disease (13%), and neuromuscular disorders (5%).³⁹

Invasive Mechanical Ventilation

Invasive mechanical ventilation involves intubation of the patient or tracheotomy along with the use of an automatic cycling

ventilator to generate air pressure and thus assist or take over the breathing function of the patient. The goals are to improve oxygenation and reduce the work of breathing.

• The main variables that determine the amount of mechanical ventilation provided are the ventilator’s pressure, volume, flow, and time.

• There are many types of positive pressure mechanical ventila-tors that can provide a variety of modes of ventilation, as described in Table 2-13.

4 The vast majority of patients receiving ventilatory assistance undergo assist-control, intermittent mandatory ventilation, or pressure-support ventilation, with the latter two often being used in combination.

4 In addition, dual control modes are now available, which use a feedback loop to allow the ventilator to control pres-sure or volume. In the dual control within-a-breath mode, the ventilator switches from pressure control to volume control during each breath, whereas the dual control breath-to-breath mode operates in either the pressure-support or pressure-control mode, with the pres-sure limit increasing or decreasing as needed to achieve a preset VT.

• The goal of mechanical ventilation is to strike a balance between excessive respiratory muscle rest, which causes deconditioning and muscle atrophy, and excessive stress, which promotes respiratory muscle fatigue.

4 Invasive mechanical ventilation is commonly associated with poor nutrition, psychological depression, poor patient moti-vation, lack of restful sleep, and lack of mobility, which con-tribute to the vicious cycle that often occurs in respiratory failure.

A B

C D E

Figure 2-19: Some types of tracheostomy tubes. A, Fenestrated. B, Portex speaking or talking. C, Passy-Muir valve connected to a tracheostomy tube. D, Montgomery T-tube. E, Tracheostomy button.

28 CARDIOVASCULAR AND PULMONARY PHYSICAL THERAPY

4 Other complications associated with invasive positive pres-sure ventilation include barotrauma, possible pneumothorax, diminished cardiac output, and hypotension.

• Physical therapy treatments for a patient receiving mechanical ventilation invariably trigger the ventilator alarms. Therapists should become familiar with the various ventilator settings (Table 2-14) and alarms so they can differentiate between real clinical problems and activity-induced false alarms.

4 Low-pressure alarms warn of disconnection of the patient from the ventilator or of circuit leaks.

4 High-pressure alarms indicate rising pressures (e.g., exces-sive secretions in the airways, kinked tubing, tubing filled with water, patient–ventilator asynchrony, or splinting of chest because of pain during movement).

4 Condensation of water in the corrugated tubing leading to the patient increases the resistance in the circuit and generates pos-itive end-expiratory pressure (PEEP); if it accumulates near the

endotracheal tube, the patient can aspirate the water, which may be contaminated by bacterial growth. Therefore, this mois-ture should be drained into a receptacle, not back into the sterile humidifier, at the beginning of each treatment session.

• Mechanical ventilation is not a contraindication for aggressive physical therapy, including ambulation, as long as the patient is hemodynamically stable, receiving PEEP of 5 cm H₂O or less, tolerating a weaning mode of ventilation, and does not exhibit abnormal signs and symptoms in response to pre-gait activities (see Chapter 6, pages 261, 278, and 282).⁶Exercise training of both the respiratory and peripheral muscles is recommended to prevent deconditioning and the adverse effects of medications and has been shown to increase muscle strength and ventilator-free time and thus improve functional outcomes. During ambulation mechanical ventilation can be maintained by bagging, sometimes provided by a nurse or respiratory therapist, or with a portable ventilator.

TABLE 2-13: Types and Modes of Positive-Pressure Mechanical Ventilation Type and Mode of Ventilation Description

Conventional Positive-Pressure Ventilation: Volume or Time Cycled, Preset Tidal Volume (VT) Augmented minute or assisted

mechanical ventilation (AMV) or Assist/control (A/C) ventilation (ACV)

Delivers a preset VTwhen the patient triggers the ventilator by spontaneous inspiratory effort;

if less than required or no inspiratory effort is provided, the machine delivers a preset minute ventilation

Controlled mechanical ventilation (CMV), Volume-controlled ventilation (VCV)

Delivers a preset VTat a predetermined rate without regard to patient’s spontaneous breathing pattern

Intermittent mandatory

ventilation (IMV) Allows the patient to breathe spontaneously between the “mandatory” ventilator breaths, which are delivered at the preset rate regardless of the phase of the patient’s spontaneous breathing. Mandatory minute ventilation (MMV) can be used with IMV to ensure a minimal minute ventilation with low IMV rates in case the spontaneous ventilation becomes inadequate

Synchronous intermittent

mandatory ventilation (SIMV) As for IMV, except that SIMV allows the mandatory breaths to be triggered by the patient’s spontaneous inspiratory efforts

Conventional Positive-Pressure Ventilation: Flow or Time Cycled, Preset Peak Pressure Pressure-support ventilation

(PS, PSV) Augments the inspiratory phase of a patient’s spontaneous ventilatory efforts with a preset amount of positive pressure in order to reduce the work of breathing imposed by the endotracheal tube. PSV can be added during volume-controlled ventilation, as in PIMV or PSIMV

Pressure control ventilation (PCV) Delivers a preset number of breaths per minute with fixed inflation pressure and time but allows patient’s pulmonary compliance to determine VT

Pressure control with inverse ratio

ventilation (PCIRV) As for PCV, except with inspiratory time exceeding expiratory time to prevent collapse of the alveolar units; raises the mean airway pressure without increasing the peak inspiratory pressure Positive end-expiratory pressure

(PEEP) Applies a threshold-like resistance at the end of expiration to prevent early closure of the distal airways and alveoli

Continuous positive airway

pressure (CPAP) Maintains pressure, usually above ambient levels during both inspiration and expiration in a spontaneously breathing patient. It is often used to wean patients off mechanical ventilation Airway pressure-release

ventilation (APRV) In spontaneously breathing patients receiving a high level of CPAP, allows brief passive exhalation to occur by periodically releasing the CPAP to a lower level so that functional reserve capacity (FRC) is reduced and CO2is excreted

Proportional assist ventilation (PAV) Delivers positive pressure into the airways of spontaneously breathing patients in direct proportion to instantaneous effort; no preset frequency, Vt, pressures, or flows

High frequency ventilation Uses small tidal volumes at frequencies of >100 breaths/min to increase the kinetic energy of the gas molecules and thus their diffusion movement

CHAPTER 2 44 Pulmonology 29

Noninvasive Mechanical Ventilation

Noninvasive ventilation is a form of ventilatory assistance that does not require intubation, yet provides partial ventilatory support in order to maintain appropriate levels of arterial PO2 and P_CO2 while also unloading the respiratory muscles. It is used most com-monly in patients with chronic or acute respiratory failure, where it has been shown to reduce the need for invasive mechanical ventilation as well as complications and mortality^4,17,18,44; it is also used in the treatment of obstructive sleep apnea, where positive pressure pneumatically splints open the upper airway to prevent collapse.

• Noninvasive positive pressure ventilation employs a positive-pressure ventilator connected to a mask that applies positive air pressure to the nose, mouth, or both. Because the nasal mask permits talking and eating, it is often preferred by patients with chronic disease.

4 Continuous positive airway pressure (CPAP) provides posi-tive pressure throughout the respiratory cycle.

4 Bilevel positive airway pressure (bi-PAP) is similar to CPAP except that the inspiratory and expiratory pressures are set separately and the difference between the two is the driving pressure for ventilation.

4 Airway pressure-release ventilation (APRV) may be added for patients receiving high-level CPAP in order to allow greater passive exhalation to occur by intermittently releasing the CPAP to a lower level; thus, functional reserve capacity (FRC) is reduced and additional CO₂is eliminated.

• Negative-pressure ventilation involves the intermittent applica-tion of subatmospheric pressure, using an airtight enclosure around the thorax, to assist in expanding the chest wall.

4 The tank ventilator, or iron lung, is a rigid tank into which the patient’s entire body, except for the head, is placed.

4 A cuirass is a rigid shell that fits over the patient’s chest and abdomen.

4 The body wrap ventilator consists of a sealed garment that encompasses the chest and abdomen.

• Noninvasive mechanical ventilatory assistance can also be achieved through mechanical displacement of the abdominal contents, in order to augment movement of the diaphragm, or by electrical stimulation of the diaphragm.

4 A rocking bed rocks the patient back and forth, head to toe, through an arc of 45º so that the force of gravity produces movement of the diaphragm.

4 A pneumobelt consists of a rubber bladder, contained in an abdominal corset, that periodically inflates to force the dia-phragm upward.

4 Diaphragm pacing or electrophrenic respiration involves elec-trical stimulation of the phrenic nerve to elicit contraction of the diaphragm, which can be used with patients in whom the neuromuscular apparatus is intact (e.g., those with central alveolar hypoventilation or high cervical spinal cord injuries).

Extracorporeal Ventilation

Ventilatory support can also be provided by extracorporeal mem-brane oxygenation (ECMO), also called extracorporeal life support (ECLS), which involves the circulation of venous blood outside of the body through a carbon dioxide scrubber and membrane oxygenator (thus, it is sometimes referred to as veno-venous ECMO or ECLS), so that it is returned to the body as arterial blood with the desired PaCO2 and PaO2. Alternatively, low-frequency

Ventilatory support can also be provided by extracorporeal mem-brane oxygenation (ECMO), also called extracorporeal life support (ECLS), which involves the circulation of venous blood outside of the body through a carbon dioxide scrubber and membrane oxygenator (thus, it is sometimes referred to as veno-venous ECMO or ECLS), so that it is returned to the body as arterial blood with the desired PaCO2 and PaO2. Alternatively, low-frequency

In document UNIVERSIDAD DIEGO PORTALES FACULTAD DE COMUNICACIÓN ESCUELA DE PERIODISMO (página 117-146)