What do you look at when evaluating a patient?
- resp. rate
- breathing pattern
- use of accessory muscles
- breath sounds
- work of breathing
RT Dept. maintains a record or a flow sheet of the following
- Basic pt. info-name, diagnosis, age, ht, wt, IBW
- Initial settings-mode, MV, TV, Peak, Plateau, Compliance, Initial parameters, ET size, ABG's
- Checks-alarms and correct settings
What do you do in your initial assessment
- Listen to breath: adequate volumes & proper tube placement
- Alarms set: apnea, low & high pressure, power failure
- Obtain ABG's: 15 min after
- Chest x-ray: tube placement
- Mode selection: If auto PEEP or PEEP is present harder to assist
- Minute ventilation, tidal volume, and rate: machine tells
- Tubing compliance:
- Alveolar ventilation: affected by closed suction & HME
Three factors to consider with alveolar ventilation
- anatomical deadspace
- normal mechanical deadspace
- added mechanical deadspace
Normal Mechanical Deadspace
- vent circuits volume lost up to 75-150 mls
- rebreathed volume
- caused by artificial nose
- calculated as 1 ml/Ib of IBW
- subtracted from delivered TV to estimate alveolar ventilation
- using an ET tube changes calculated anatomical deadspace-1 ml/kg of IBW
Added Mechanical Deadspace
- must be subtracted to determine actual alveolar ventilation
- exhaled Tv-added-anatomic=alveolar
- final alveolar ventilation calculated (TV-Anatomic)x(f)=minute volume
Peak inspiratory pressure
- highest pressure during inspiration
- used to calculate dynamic compliance
- pressure decreases-leak?
- use insp. pause control
- press. drops during hold
- calculate static compliance
What modes do you have a set pressure in?
- Volume changes with compliance & resistance
What is mean airway pressure affected by?
- peak inspiratory pressure
- end expiratory pressure (PEEP)
- cycle time
- Could affect cardiac output
End expiratory pressure
- measures Auto Peep
- allows longer time to exhale
If pressure limit is activated patient may need
- lung compliance decreased
- pt. is coughing or biting tube
- water may be inline
- pulmonary edema
- pleural effusion
checking for leaks
- check cuff
- check vent circuit
- check humidifiers
- tissue necrosis
- late stage carcinoma
- metabolic disorder
- alcohol/carbon monoxide
- Systemic arterial BP
- CVP-measure at the end of a expiration
- Exam of chest-BS
- Monitor cuff
Monitor cuff pressure
- every 8-12 hrs
- don't exceed 25 mmHg
- Decrease risk of tracheal narcosis, min. leak techn., min. occluding tech.
What causes decrease static compliance?
- pulmonary edema
- pleural effusion
- abdominal distention
How is decrease static compliance easily detected?
- 1. BS, percussion sounds, palpation, x-ray
- 2. decreased compliance implies vent. is less effective
- 3. results in decreased PaO2 and increase PaCO2
- 4. pressure limited vent will need an increase in pressure to deliver an adequate volume.
- if constant or decreased & static is decreased=lung compliance down
- if decreased & static constant=airway resistance increased
When does airway resistance increase?
- increased secretions
- mucosal edema
- airway problem
Calculate airway resistance
- Norm. .6-2.4 cmH2O/l/sec
- ET tube increass to 6 cmH2O/l/sec
- Bronchospasm increases from 3-18 cmH20/l/sec
How do you compensate for airway resistance?
removing obstruction or decreasing flowrate
What do delivery of oxygenation to the dissues depends on?
- arterial oxygen content
- cardiac output
PaO2 desired x FiO2 known/PaO2 known
Selection of PEEP
- adequate for pt. to maintain PaO2
- if more than 50% of FiO2 is needed
Four basic categories of hypoxia
- histotoxic-cells are unable to utilize oxygen
- anemic hypoxia- hemoglobin concentrations lower than norm. unable to transport O2.
- circulatory hypoxia- cardiovascular system fails to transport O2
- hypoxemic hypoxia- hypoventilation, shunting, vent perfusion mismatching and diffussion defects.