Clinical Reasoning for Gas & Secretion Impairments Flashcards
What Ax findings indicate a secretion impairment?
- Pt subject reports
- Hx of smoking & respiratory disease
- Observe sputum
- Palpation of secretions
- Auscultation of URTN and coarse crackles
- Moist &/or productive cough
- Wheeze?
- Obstructive spirometry results
What Ax findings indicate a gas impairments?
- ABGs show decreased PaO2 & SaO2, but increased PaCO2
- Observe altered breathing pattern
- Observe cyanosis
- Auscultation of no/decreased breath sounds and fine crackles
- Palpation of decreased LBE
- Spirometry results?
- CXR changes
What is the effect of fast inspiration?
- Air flow depends more on airways resistance
- Less resistance = greater flow
- Resistance is less in the non-dependent regions, so airflow is better distributed here
What is the effect of slow inspiration?
- Air flow depends more on lung compliance
- Greater compliance = greater flow
- Compliance is greater in the dependent regions, so airflow is better distributed here
What is closed capacity (CC)?
The lung volume at which the dependent airways begin to close or cease to ventilate. CC increases with age and smoking
What is the relationship btw CC and FRC?
Normally FRC is greater than CC so alveoli are open during tidal breathing. If FRC is less than CC (or CC is greater than FRC) there will be small airway closure during tidal breathing. FRC < CC results in reduced gas exchange and decreased PaO2/SaO2
Gas movement techniques: deep breathing
Deep breaths increase ventilation throughout the lungs. It does this through: increasing tidal volume (Vt), which stretches the alveoli and stimulates surfactant production, which decreases the surface tension to increase lung compliance, which overall increases VA/VE
Gas movement techniques: general positioning
Aims to increase lung volumes generally (most importantly functional residual capacity or FRC). Upright postures such as sitting and standing have the highest FRC. When FRC > CC, we have increased lung compliance, decreased respiratory load, and increased VQ matching and gas exchange. This is good for use with generalised low lung volumes (e.g. post-op pts)
Gas movement techniques: specific positioning
Aims to re-expand areas of localised atelectasis (e.g. lung, lobar or segmental atelectasis/collapse). Position patient so that the problem area is uppermost/non-dependent portion of lung. Gravity will stretch the area open, stimulating surfactant release and increasing local compliance. Once the collapsed region has been passively opened, then you can use generalised positioning (upright) and DBE to maintain FRC. Modified specific positioning has some positions for some lung segments (e.g. ML/LL) that involve a head down tilt (HDT)
Gas movement techniques: mobilisation
This includes from bed to chair (e.g. SOOB), standing up/marching on the spot, walking, or progressive exercise. Mobilisation has several benefits that lead to increases in gas movement (mass movement and gas exchange), including increasing FRC, O2 demand, CO and lung perfusion, and V/Q matching
What are the three main components to the physiology of coughing and huffing?
- 2-Phase Gas-Liquid flow
- Dynamic compression
- Equal pressure point
Explain the 2-Phase Gas-Liquid flow
Explains the interaction of liquid (airway secretions) and gas (air) with a conduit (airway). Responsible for how secretions move towards the mouth. When gas passes through a liquid lined tube (like an airway), the liquid can be moved in two ways:
- Mist flow: the liquid is carried as small droplets in the gas
- Annular flow: the surface of the liquid layer moves in layers
For gas-liquid flow to occur towards the mouth, the expiratory flow rate must be at least 10% greater than inspiratory flow rate (i.e. slow breath in with faster breath out). Cough has higher expiratory flow and uses mist flow, whereas huff has lower flow rates and uses annular flow
Explain dynamic compression
During a forced expiration some parts of airways narrow (called dynamic compression) which leads to high airflow (velocity) and turbulence. This shears the mucus layer for gas-liquid interaction (annular or mist flow). Dynamic compression occurs towards the mouth at the equal pressure point (EPP)
Explain the equal pressure point
The EPP is the point where intrapleural pressure (pressure outside the airway) is equal to the alveolar pressure (pressure inside the airway). When Ppl > Pal the dynamic compression leads to faster flow rate and movement of secretions. The position of EPP can be altered along the airway depending on the volume of breath from which you begin the forced expiration – this will affect where secretions are moved from
Secretion movement techniques: cough
Clears secretions from upper central airways
1. Deep inspiration to TLC
2. Closure of glottis
3. Contraction of abs
4. Opening of glottis and explosive breath
