Congenital Heart Defects

You have been asked to conduct an educational session regarding the risk factors associated with congenital cardiac defects for a group of newly wed couples who are considering starting a family. Below, discusses behavioral and genetic risk factors; including, pathophysiology, diagnosis, and treatment. 

A congenital anomaly affects 3-5% of all live births in the US, with the most common defect being congenital heart disease (CHD).1 Congenital heart disease is defined as “a gross structural abnormality of the heart or intra-thoracic great vessels that is actually or potentially of functional significance”.2 Congenital heart defects occurs approximately in 9 per 1000 cases in the US, and are a leading cause of death.3 The etiology of congenital heart defects varies and includes chromosomal abnormalities, non-genetic causes, and pregnancy exposure to environmental factors that adversely affect fetal development. Chromosomal abnormalities such as trisomy 21 and chromosome 22q11 micro-deletion represent 8-20% of CHD cases whereas non-genetic causes due to maternal factors such as maternal rubella infection, epileptic disease, maternal use of thalidomide, and obesity represent less than 5%. Congenital heart defects include: patent ductus arteriosus (PDA), atrial septal defects (ASD), and ventricular septal defects (VSD).2

Patent ductus arteriosus (PDA) is associated with morbidities such as intraventricular hemorrhage (IVH), bronchopulmonary dysplasia (BPD), and necrotizing enterocolitis (NEC). PDA is confirmed by echocardiographic parameters for assessment of shunt presence, and is a cyanotic anomaly if shunting of blood occurs from right to left. Usually, PDA develops due to failure of the ductus arteriosus to close at birth and the type of shunt depends on the difference between aortic and pulmonary artery pressure. Specifically, if the pressure in the pulmonary circulation exceeds the pressure in the systemic circulation, blood will be shunted from right to left. Clinical presentation of PDA includes: bounding pulses which a strong pulse that quickly disappears, a continuous murmur like washing machine, enlarged liver, and respiratory distress such as retraction, tachypnea, hypoxemia, and apnea. The most common risk factor associated with PDA is maternal smoking. Treatment includes: indomethacin (Indocin), a prostaglandin inhibitor, surgical clip, and coil.4

Atrial septal defects (ASD) is an acyanotic anomaly with shunting of blood from left to right. The presence of an ASD reflects failure of the foramen ovale to close and/or failure to correctly form the atrial septum. ASD is classified as two types of defects: ostium primum which usually occurs low in the atrial wall where both mitral and tricuspid valves are involved, and ostium secundum, which occurs high in the atrial wall where the foramen ovale is involved, and is the most common type. ASD is due to a difference of pressure between the left and right atria, where blood moves from the left to right atrium through the ASD. Clinical presentation of ASD includes: increase pulmonary blood flow and right ventricular hypertrophy. Mostly, the chest x-ray is normal, and auscultation reveals a systolic murmur. Both ASD and pulmonary valve anomalies are associated with maternal smoking. Treatment includes: surgical correction for closure and/or placement of a plastic prosthesis via open heart surgery.

A ventricular septal defect (VSD) is an acyanotic anomaly which results in a left to right shunt. VSD is classified as either small or large defects, where significant left to right shunt occurs with a large defect. Cardiac output is forced through the lungs due to pulmonary vascular resistance, which normally, is one-fifth of systemic vascular resistance. Large VSD defects can increase pulmonary blood flow to the point where it causes fibrosis of the pulmonary arterioles, which eventually leads to irreversible pulmonary hypertension. This condition is called Eisnmenger’s syndrome and is associated with VSD where pulmonary vascular resistance is larger than systemic vascular resistance which reverses the left to right shunt to a right to left shunt. Treatment includes: surgical correction for large defects during cardiopulmonary bypass, digoxin, furosemide, and pulmonary banding.2

References
1. Madsen NL, Schwartz SM, Lewin MB, Mueller BA. Pre-pregnancy body mass index and congenital heart defects among offspring: a population-based study. Congenit Heart Dis 2013;8(2):131-141
2. Hoffman JI, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol 2002;39(12):1890-1900
3. Sullivan PM, Dervan LA, Reiger S, Buddhe S, Schwartz SM. Risk of congenital heart defects in the offspring of smoking mothers: a population-based study. J Pediatr 2015;166(4):978-984.e2
4. Jain A, Shah PS. Diagnosis, Evaluation, and Management of Patent Ductus Arteriosus in Preterm Neonates. JAMA Pediatr 2015;169(9):863-872

Bronchopulmonary Dysplasia and the RT

Bronchopulmonary dysplasia (BPD), also referred to as chronic lung disease (CLD), is a serious ailment that affects infants after receiving respiratory support either in the form of oxygen therapy or mechanical ventilation. It occurs frequently in premature infants who are under the age of twenty-eight weeks gestational age and have been treated for respiratory distress syndrome (RDS) by means of mechanical ventilation. Diligent set up and monitoring is necessary when delivering positive pressure to a premature infant via mechanical ventilation. Failure to do so may result in trauma and oxygen toxicity to the premature lung, further, leading to acute lung injury and ultimately chronic lung disease. Respiratory therapists (RTs) are the healthcare professionals in charge of providing mechanical ventilation. They are at the forefront when a premature infant is receiving care for RDS. They control the mechanical ventilator settings, know how each one will affect the premature lung, and understand all the risks and complications associated with mechanical ventilation. These factors allow RTs to think strategically about patients and treatments, and that is why they play such an important role in the prevention and management of BPD.
Mechanical ventilation strategies for infants who are at risk for BPD and those who have confirmed BPD differ. However, both are comprised of guidelines regarding optimal setting of multiple mechanical ventilator parameters. One of these guidelines for early treatment is focused on using a smaller tidal volume, recommending it be kept between five and eight milliliters per kilogram.1 This step would decrease the risk of causing trauma, particularly volutrauma, which leads to over distension of the lungs. The use of low FiO2 is another crucial part of this early preventative strategy. Exposing premature infants to lower levels of pure oxygen makes it less likely that they will develop oxygen toxicity. Other components of early treatment include short inspiratory times and using low levels of positive end expiratory pressure (PEEP) to avoid retaining unwanted volumes after expiration, also known as air trapping. The RT must turn to management strategy if BPD is confirmed in a premature infant. This requires delivering larger tidal volumes, and a more involved focus on expiration time, adjusting ventilator parameters to ensure that the expiratory time is sufficient for these infants who usually have expiratory airflow limitation. Whether it is early treatment or late management with mechanical ventilation, it is the RTs job to control all of these specific settings including maintaining the correct breathing rate, pressures, and flows within the circuit. In addition to running the ventilator, the RT is responsible for noticing when premature infants are not responding as expected to the mechanical ventilation strategy.
The future for prevention and treatment of BPD is full of many possibilities. Research has been done on medications that have potential to minimize the effects or occurrence of this disease. Due to infections being involved in the progression of BPD, antibiotics are a viable option. It has been shown that when used prophylactically, azithromycin has the potential to decrease both the incidence of BPD and associated death.2 However, the use of antibiotics when they may not be necessary can lead to complications with infections in the future. More importantly for RTs are the use of bronchodilators and inhaled corticosteroids. There are many forms of both bronchodilators and corticosteroids. This provides RTs with many options and chances to find which medication works best for their individual patients. Bronchodilators have been proven effective in the short-term management of BPD symptoms, but their use for this disease varies greatly. 3 Inflammation caused by mechanical ventilation induced lung injury is a common problem leading to the development of BPD. Inhaled corticosteroids are used to prevent and decrease inflammation for multiple respiratory ailments. Although they seem promising, the pros, cons, and efficacy of these medications require further research.
In short, BPD is a serious disease that affects many premature infants that are already suffering from respiratory ailments. Sustained lung injuries due to mechanical ventilatory support for RDS are the most common cause of BPD development. Currently, specific guidelines for the use of mechanical ventilation are being used to try and prevent or manage this disease. As for the future, it seems involvement of different types of pharmacologic intervention will become more popular. The role of the RT throughout all of this is to provide mechanical ventilation based on evidence-based guidelines, and to lead the way for the use of bronchodilators and inhaled corticosteroids in the management of BPD.

References
1. Walsh BK. Neonatal and Pediatric Respiratory Care, 4th edition. St. Louis, Missouri:    Elsevier; 2015.
2. Nair V, Loganathan P, Soraisham AS. Azithromycin and other macrolides for    prevention of bronchopulmonary dysplasia: a systematic review and meta    analysis. Neonatology 2014;106(4):337-347.
3. Slaughter JL, Stenger MR, Reagan PB, Jadcherla SR. Inhaled bronchodilator use for    infants with bronchopulmonary dysplasia. J Perinatol 2015;35(1):61-66.

Importance of communication in respiratory care

Good communication in health care, specifically respiratory care will significantly improve the outcome of patient care. Just as communication is important throughout our educational experience, it’s also important in our professional careers. We’ve all experienced a time in a classroom setting or within our professional careers where there’s been a misunderstanding or a conflict due to poor communication, right? A large part of establishing good communication skills within respiratory care is dependent upon patient cooperation. In order to achieve effective and efficient patient care, it’s important to understand the role of communication. As a respiratory therapist (RT), there is a myriad of equipment to become familiar with, whether it be a nebulizer or a variation of a mask as with noninvasive ventilation, for example. Utilizing communication techniques, such as “clarification” and “teach back” will help ensure the RT and the patient understand the process of the treatment at hand.
This leads me to the importance of distinguishing the concepts efficiency and effectiveness. Effectiveness is selecting goals and achieving them while efficiency is proper use of resources to achieve a goal or the amount of time needed to produce a particular output. For example, an RT may efficiently communicate cost of a procedure to a patient; yet, this may lead to miscommunication if the steps and outcome of the procedure are not explained as well. In order to prevent miscommunication and obtain effectiveness, proper communication steps should be followed. For example, a patient may think an RT is trying to hurry a procedure at a low cost. Therefore, it’s important for the RT to take the time to properly communicate the procedure, the equipment involved, how it may feel, the outcome of the procedure, and why this procedure is chosen. Thus, the intended and perceived meaning are the same. For example, during oxygen therapy, the RT can explain to the patient that they may feel some dryness or pressure; however, various factors can be adjusted to ensure patient comfort. One outcome of communication, may be the patient’s level of trust with the RT. As a result, communication is efficient and effective.
In short, sources of good communication include: increased efficiency, improved quality, increased responsiveness from the patient, and innovativeness. All of these are needed for a good competitive advantage as well. Some communication skills that are important to apply in the respiratory care profession include: paying attention to your patient, eye contact, showing empathy, and asking for clarification when needed. These skills equate to being a good listener. In order for the patient and the RT to reach an understanding, communication and good listening skills are essential.

References
1. Robert M. Kacmarek, James K. Stoller, Albert J. Heuer. Egan’s Fundamentals of Respiratory Care. 2013:3:51-53.
2. Gareth R. Jones, Jennifer M. George. Contemporary Management. 2011:16:530-31.

Gas laws and the relevance to respiratory care

Gas laws and the relevance to respiratory care

Understanding physics helps us understand how respiratory care equipment works. The study of physics is the interaction between matter and energy. According to the law of conservation of energy, “Energy cannot be created or destroyed: energy can only be transferred1.” There are two types of energy: kinetic and potential. Kinetic energy is in the energy of motion whereas potential energy is stored energy. The three states of matter related to respiratory care in order of greatest to lowest kinetic energy are: gases, liquids, and solids. First, gases are easily compressible and can expand to fill a container. In respiratory care, we can think of the container as the lungs. Next, a liquid assumes the shape of a container and are less compressible. Lastly, a solid which is mostly potential energy is highly structured and maintains shape and volume because of strong molecular bonds.

Furthermore, understanding temperature and pressure effects on the three states of matter and phase changes, helps respiratory therapists understand respiratory care equipment and how to care for patients. For example, properties of a liquid include pressure, buoyancy, and viscosity. When discussing pressure, it is dependent upon density, weight, and height. Buoyancy occurs because the pressure below a submerged object will always exceed the pressure above it. And viscosity discusses the force opposing a fluid’s flow. Understanding the relationship between resistance and pressure as described in Poiseuille’s Law, helps us understand various levels of blood pressure, for example. When comparing the flow of blood and water, blood has a greater viscosity than water; therefore, it takes more driving pressure for blood to move through the arteries than the required pressure to move water through the arteries. If the artery is clogged, the diameter of the artery is decreased which then increases resistance; subsequently, causing an increase in blood pressure2.

Additionally, heat transfer concepts including conduction, convection, evaporation, condensation, and sublimation also help in the design of devices used to care for patients. For example, radiant warmers use the heat transfer principle of convection to warm premature infants. Various gas laws are also applicable in caring for respiratory care patients. Understanding the relationship between pressure and volume as described in Boyle’s law enables respiratory therapists to understand the mechanics of breathing. One particular concept that’s important is humidification which includes, absolute humidity and relative humidity. Absolute humidity is the actual amount of water vapor in a specific volume of gas while relative humidity is the ratio of the absolute humidity to the amount of water vapor that is needed to fully saturate that same volume of gas, expressed as a percentage. Both are essential in preventing airway dryness and irritation. Various respiratory care equipment allows a respiratory therapist to adequately humidify inspired gases during oxygen therapy2. Lastly, Henry’s law describes the diffusion rate, or dissolving of a gas into a liquid, which is relevant to the diffusion of oxygen into the blood and carbon dioxide out of the blood via the alveolar capillary membrane2.

References
1. Robert M. Kacmarek, James K. Stoller, Albert J. Heuer. Egan’s Fundamentals of Respiratory Care. 2013:6:117-25.
2. J.M. Cairo. MOSBY’S Respiratory Care Equipment. 2014:1:4-17.

Humidity, aerosol and medical gas therapy

Understanding of humidity and aerosol therapy and medical gas therapy

Understanding humidity is an important component of choosing appropriate devices to deliver humidity and aerosol treatments safely to the patient. The purpose of humidity therapy is to heat and humidify gas on inspiration and to cool and reclaim water (H2O) from exhaled gas. This is a normal function of the nose. However, when the upper airway is bypassed due to the insertion of an artificial airway in the trachea for mechanical ventilation for example, the nose no longer functions to provide heat and humidification to the respiratory tract. The deficit in temperature and humidity ultimately causes damage to  the respiratory tract. The relative humidity is the ratio between the actual amount of H2O in a given volume of gas and the maximum amount of H2O the gas is capable of holding at a certain temperature. The absolute humidity is the actual amount of H2O in a given volume of gas. Body humidity is the relative humidity at body temperature of 37 degrees celsius expressed as a percentage. So the capacity of H2O at 37 degrees celsius is 44 mg of H2O. Further, there’s a humidity deficit when inspired air is not fully saturated at body temperature, which is the reason why humidity therapy is important1.

To provide humidity therapy for patients with a humidity deficit, hospitals and other medical facilities utilize humidifiers, which is a device that adds molecular water to a gas. If the temperature of the gas is higher, then the capacity of the gas to hold water vapor is also higher. Various devices used to deliver humidification include bubble humidifiers, passover devices, and HME’s (heat and moisture exchange) devices. Bubble humidifiers  generate small gas bubbles by using a diffuser to break up a stream of medical gas as it flows through a tube submerged in a container of water. As the gas bubbles make their way up from under the water, they pick up water vapor from evaporation of the water in the container. The gas then passes through the device to an interface such as nasal prongs or a face mask worn by the patient,  thereby facilitating delivery of humidified gas to the patient. The greater the number of small bubbles produced, the greater the surface area for contact between the water and gas molecules, and the longer the gas and water interaction, the  more opportunity for evaporation to occur. Furthermore, heat will improve water vapor output of  humidifiers. As noted above, heating systems are primarily used for patients with bypassed upper airways as well as those receiving noninvasive mechanical ventilation1.

Sterile water and sterile saline are used to provide bland aerosol therapy. There are many devices that deliver aerosol therapy to patients including large volume jet nebulizers and ultrasonic nebulizers. Some indications for aerosol therapy include upper airway edema, post extubation edema, and the need for sputum specimens. Bland aerosol delivery and cool humidified gas are commonly used in combination to treat croup and post extubation edema, which are upper airway inflammation related.

References
1. Robert M. Kacmarek, James K. Stoller, Albert J. Heuer. Egan’s Fundamentals of Respiratory Care. 2013:35:819-23.
2. J.M. Cairo. MOSBY’S Respiratory Care Equipment. 2014:6:159-66.

Understanding airway pharmacology

Understanding of airway pharmacology

There are several classes of aerosol medications. Some of these include, beta-2-adrenergic bronchodilators, anticholinergic bronchodilators, mucolytics, corticosteroids, non-steroidal anti-asthma drugs, and anti-infective agents. The purpose of aerosol therapy includes, but is not limited to delivering medications to the respiratory tract in order to relieve bronchospasms, treating a pulmonary infection, humidifying inspired gases, and reducing secretions. Aerosol particle size affects the depth of deposition of an aerosol agent, which influences the device used to deliver aerosol medication to treat a specific disease1. For example, if the aerosolized drug therapy is targeting the upper airway, a nebulizer that produces a particle size with a mass median aerodynamic diameter (MMAD) ranging from 5 to >50 µm would be needed whereas, if the lung parenchyma is the target, the nebulizer used should be capable of producing particles in a smaller size range, ideally, less than 0.1µm.

In, a patient with asthma who experiences airway obstruction and airway inflammation, a beta-agonist and an anticholinergic bronchodilator are often used to reverse or improve airflow obstruction. Alternately, corticosteroids and non-steroidal anti-asthma drugs are used to reduce or prevent the airway inflammation associated with asthma. Next, mucolytics are used to reduce mucus viscosity and improve mucociliary clearance in diseases such as cystic fibrosis (CF). Additionally, ribavirin, and tobramycin are used to treat respiratory syncytial virus (RSV) in infants, and cystic fibrosis (CF) patients respectively. Moreover, some of the various anti-infective agents include pentamidine to treat pneumocystis pneumonia (PCP) in AIDS infected patients, for example2.

There are many indications for the use of specific medications, but there are also contraindications and adverse effects that must be considered by the respiratory therapist (RT). For example, patients with CF have a large amount of secretion build up and over time this may lead to respiratory infection. These infections often require hospitalization and intravenous antibiotics. As a result of the infections, a patient with CF will have decreased lung function; at which point, the use of dornase alfa and/or inhaled tobramycin agents is indicated for treatment2.

It’s important to note that the RT should measure vital signs before, during, and after providing an aerosol agent. This is accomplished through monitoring respiratory rate, pulse, breath sounds via auscultation, and patient appearance, i.e., color of their skin and whether or not they are sweating. As previously discussed, a patient with asthma would require a fast-acting bronchodilator for acute exacerbation. After receiving this medication, a patient assessment would include peak flow rate monitoring or spirometry2.

Some of the beta-agonist medications used to treat asthma include, albuterol and levalbuterol. These are known as short-acting beta-agonists (SABA), which is a quick relief rescue agent. Similarly, there are long-term beta-agonists (LABA), which serve as maintenance medication providing long-term control for a patient with asthma. An example of a LABA is salmeterol and formoterol. A SABA may last only 4 hours whereas a LABA my last up to 12 hours. A non-steroidal anti-asthma drug with minimal side effects that is usually used in children is cromolyn sodium. Corticosteroids are usually used for long-term control for a patient with asthma, but systemic corticosteroids administered intravenously or as oral burst therapy may also be used for quick relief 2.

In summary, there are several aerosol agents to provide to patients with obstructed and/or inflamed airways. Some of these medications are available via MDI, DPI, tablets, syrup, nebulization, and intravenously as well. It’s important for the RT to be aware of indications and contraindications for each patient to determine the best agent for a patient to control a disease, such as asthma.

References
1. Mosby’s Medical Dictionary, 8th edition. http://medical-dictionary.thefreedictionary.com/aerosol. 2009.
2. Robert M. Kacmarek, James K. Stoller, Albert J. Heuer. Egan’s Fundamentals of Respiratory Care. 2013:32:359-67; 17:710-20.

Patient assessment and its components

Patient assessment has several components including, lab data, electrocardiogram, pulmonary function testing, and thoracic imaging

The first part of obtaining information about a critically ill patient, is for a respiratory therapist (RT) to obtain a complete blood count (CBC). This requires a venous blood sample in order to examine the formed elements of the blood which include leukocytes (WBC), erythrocytes (RBC), and thrombocytes (platelets). Specifically, an elevated WBC count is often associated with infection; whereas, a decrease in count endangers the patient as a high risk for infection. Next, disease may be associated with abnormal RBC count. Polycythemia is an abnormal increase and anemia is an abnormal decrease in RBC count. Patients with chronic hypoxia (O2 deficiency in the tissues) often have high RBC levels as a result of compensating for extremely low blood oxygen levels. Likewise, patients who suffer from anemia often experience tissue hypoxia as the low RBC count reduces the oxygen carrying capacity of the blood. Lastly, the platelets are helpful in evaluating coagulation (forming a blood clot)1.

Secondly, the RT interprets electrocardiogram (ECG) which is an inexpensive as well as non-invasive method to measure whether a patient shows signs of myocardial disease. This test is for acute symptoms only and is not indicative of future heart problems. The cardiac muscle has three types of cells including, SA and AV nodes (the hearts pacemaker cells), purkinje fibers, and atrial and ventricular cells. All three of these cells are capable of electrical excitation. If there is a defect in any of these three areas, there will be a decrease in cardiac output (volume of blood the heart pumps per minute)1. It’s important for the RT to be able to read the ECG including: atrial and ventricular rates, PR intervals, QRS complexes, T waves, and ST segments. Any variances from the norm will help identify various complications and diseases for a patient. For example, an abnormal ST segment may indicate a life threatening cardiac abnormality as it’s a common indicator of a myocardial infarction (MI)2.

Thirdly, RT’s frequently use pulmonary function testing (PFT) on patients at the bedside. PFT measures flow rates throughout the airways, lung volumes and capacities, and the ability of the lungs to diffuse gases1. Results of these tests help therapists understand whether a patient may have obstructive or restrictive lung diseases or other pulmonary diseases. Specifically, a patient with an obstructive lung disease would show a decreased expiratory flow on their PFT indicative of asthma or emphysema, for example. Alternately, a patient showing a restrictive disease on a PFT would show reduced lung volumes and capacities. A patient with restrictive disease may perhaps have a neuromuscular disease such as ALS. Determining which type of lung disease helps the RT and medical team decide on appropriate therapy for the patient1.

Lastly, thoracic imaging is necessary for the medical team to evaluate the cause and degree of the pulmonary disease. Specifically thoracic imaging includes, x-ray, CT, ultrasound, and MRI scans. There are important steps to take to evaluate the various modes of chest film. These steps include, assessment of the quality of the film and the technique used followed by a disciplined approach to evaluating the image. A chest film can provided evidence of a pleural effusion, pneumothorax, edema, and air bronchograms, for example. Chest films are also helpful in identifying endotracheal tube placement1.

In short, a RT must be diligent in patient assessment as their patients’ lives may be dependent on their knowledge, effort, and accuracy. It’s important to gather as much information as possible to accurately evaluate a critically ill patient. Any missing step may result in more harm than good for a patient.

References
1. Robert M. Kacmarek, James K. Stoller, Albert J. Heuer. Egan’s Fundamentals of Respiratory Care. 2013:16:359-67; 17:373-74; 19:418; 20:451-56.
2. J.M. Cairo. MOSBY’S Respiratory Care Equipment. 2014:9:282-83.

Blood gases and patient devices

Blood gases and patient devices

A significant part of a respiratory therapist’s (RT’s) job is the need to evaluate blood gas results in order to evaluate a patient’s ventilation, oxygenation, and acid base status as indicated by PaCO2; PaO2 and HbO2, pH, and HCO3− values, respectively. Blood gases provide significant information to an RT in order to make clinical decisions on various cardiopulmonary diseases. Furthermore, quality control is the RT’s primary role in analyzing blood gases. For an RT to ensure the blood gas testing is as accurate as possible, there are several important actions to take such as: controlling errors in the total blood gas testing process (i.e., pre-analytical, analytical, and post-analytical errors), record keeping, performance validation, preventive maintenance and function checks, automated calibration, calibration verification by control media, internal statistical quality control, proficiency testing, and remedial action. In short, an RT must follow policies and procedures, test new instruments for repeatability, calibrate devices to indicate if any biases exist, and remediate any errors found1.

There are various devices used for monitoring and measuring a patient’s fraction of inspired oxygen (FiO2), carbon dioxide (CO2) level, oxygen saturation (SpO2), lung volumes, and flows. Firstly, there are two types of electrochemical oxygen analyzers, namely, the galvanic and polarographic, which are used for intermittent or continuous monitoring of FiO2. Additionally, there are electrical oxygen analyzers that respond to change in the percentage of oxygen instead of partial pressure which is based on altitude variations. However, there are several problems with electrical devices including the fact that it cannot be used in the presence of a flammable gas due to the significant amount of heat generated by the electrical device2. Secondly, end tidal CO2 monitoring devices use capnography to display the CO2 concentration as a numeric reading and graphical display of CO2 measurement. CO2 concentration is displayed as millimeters of mercury (mmHg), which is a percentage of CO2. There are several methods to measure end tidal CO2 such as infrared spectroscopy, which is based on CO2 absorption of a specific wavelength of infrared light.

Lung volumes and flow rates are measured through spirometry, body plethysmography, helium dilution, and nitrogen washout techniques. These are different methods for measuring a patient’s inspiratory and expiratory breaths, which help determine various types of lung diseases such as obstruction or restriction. Thermistors are hot wire systems used to measure flow rates Pneumotachometers are devices used to measure flow based on a pressure gradient created by breathing  into the device which has a membrane with a small resistance. Additionally, there are peak flow meters to measure a patient’s expiratory flow rate. Commonly, the peak flow meter is used in the home as a way for patients with asthma to monitor how well their asthma is controlled. Through daily monitoring of peak flow rates, asthmatics can compare daily peak flow values to their personal best. Daily peak flow monitoring in conjunction with an asthma action plan enables individuals with asthma to better control their condition2.

Finally, there are various pressure sensing devices including gravity dependent barometers, mechanical aneroid manometers with pressure gauges on medical gas cylinders, and electromechanical transducers. Measuring pressures are important for RT’s as it’s used to calibrate blood gas analyzers as well as flow, and volume devices.

References
1. Robert M. Kacmarek, James K. Stoller, Albert J. Heuer. Egan’s Fundamentals of Respiratory Care. 2013:18:391-98.
2. J.M. Cairo. MOSBY’S Respiratory Care Equipment. 2014:8:253-59.

Gas laws and the relevance to respiratory care

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Importance of communication in respiratory care

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