Surgery and the Effects on Lung Function

Why can surgery disrupt normal lung function?

• general anesthesia and mechanical ventilation (no spontaneous breathing)

• surgical positioning (can affect where we auscultate)

• surgical incisions, pain and splinting

• drowsiness and reduced mobility

When surgery disrupts lung function, what may be seen?

Reduced lung expansion, impaired secretion clearance, and postoperative pulmonary complications (PPCs)

What are postoperative pulmonary complications (PPCs)?

Respiratory complications that develop following surgery. They may result from the effects of anesthesia, reduced lung volumes, impaired airway clearance, pain, and immobility

Why do PPCs matter?

They can delay recovery, increase hospital length of stay, limit mobility, and increase the need for oxygen or higher levels of care

Examples of PPCs:

• atelectasis

• pneumonia

• respiratory failure

• pleural effusion, pneumothorax, and other respiratory complications

What is PTs focus when looking at PPCs?

Understanding how surgery affects ventilation, airway clearance, and mobility, and how physiotherapy can help prevent or minimize complications

How can surgery and anesthesia lead to PPCs?

Interconnected changes(they may occur simultaneously and not necessarily in a fixed sequence) in ventilation, lung expansion, and secretion:

1. surgery and anesthesia

2. reduced lung volumes and impaired ventilatory mechanics

3. shallow breathing (atelectasis) and reduced cough effectiveness + impaired secretion clearance (retained secretions)

4. V/Q mismatch and increased risk of pneumonia

5. impaired oxygenation

6. reduced activity tolerance and, if severe, respiratory failure

What are pre-operative risk factors for PPCs?

Reduced respiratory reserve (less extra breathing capacity, especially when the body is stressed or activity is increased), reduced physical reserve, and other contributing factors

Examples of reduced respiratory reserve

COPD, poorly controlled asthma, recent respiratory infection, smoking history

Examples of reduced physical reserve

Frailty, poor fitness, low baseline mobility, and older age

Examples of other contributing factors (pre-operative risk)

Obesity, sleep apnea, poor nutrition, previous postoperative problems

Intraoperative Risk Factors for PPCs

General anesthesia, mechanical ventilation, surgical positioning (i.e. supine or side lying), prolonged duration of surgery, and upper abdominal or thoracic surgery (more at risk than extremity surgery)

• these factors can contribute to reduced lung volumes, altered ventilation, and impaired secretion clearance, increasing the risk of PPCs

What should be noted in concerns to the patient during surgery?

The patient is not breathing or clearing secretions in their usual way during surgery

What does general anesthesia do?

Produces a medically induced state that allows surgery to occur safely; it may involve medications that produce unconsciousness (amnesia), analgesia (no pain), and/or muscle relaxation

What are the respiratory effects of anesthesia?

Reduced respiratory drive and muscle activity (spontaneous breathing may be suppressed), altered lung mechanics (reduced lung volumes and increased tendency for airway closure), and impaired cough and secretion clearance (suppressed protective reflexes reduce airway clearance)

What is the effect of general anesthesia on reduced lung volumes and atelectasis?

• reduced respiratory muscle tone: less support for maintaining resting lung volume

• upward displacement of the diaphragm(not using the diaphragm to breathe): abdominal contents push the diaphragm upward, particularly when supine

• compression of dependent lung regions: reduced alveolar volume in dependent regions

What are two related consequences of general anesthesia on reduced lung volumes and atelectasis?

• decreased functional residual capacity (FRC): small airways are more likely to close

• compression of alveoli: may directly cause alveolar collapse

What may increase the risk of atelectasis during surgery?

Decreased FRC and compression of dependent lung regions; these changes begin during general anesthesia and may persist postoperatively, particularly with pain, shallow breathing, and immobility

What is the effect of general anesthesia on impaired airway clearance?

It suppresses the cough reflex and temporarily impairs mucociliary clearance, reducing the ability to remove secretions

How does impaired airway clearance increase the risk of PCCS?

By increasing the likelihood of atelectasis (retained secretions may obstruct an airway (i.e. mucus plugging), preventing ventilation of distal alveoli and causing collapse) and pneumonia (impaired secretion clearance can promote the accumulation of microorganisms, increasing infection risk)

What is important to note about retained secretions?

They can contribute to atelectasis (mucus plugging) and pneumonia (infection) BUT, they do not always lead to these complications (lots of times people are fine)

What kind of pressure is associated with spontaneous breathing?

Negative pressure

Spontaneous Breathing

• Diaphragm contracts and moves downward

• chest expands, drawing air into the lungs

• ventilation tends to favour dependent lung regions

What kind of pressure is associated with mechanical ventilation?

Positive pressure

Mechanical Ventilation

• ventilator pushes air into the lungs

• diaphragm is reduced or absent during controlled ventilation

• ventilation may shift toward non-dependent lung regions

What can different mechanisms of lung expansion do?

Alter the distribution of ventilation within the lungs

What are mechanical ventilation’s effects on regional ventilation

• positive pressure ventilation: the ventilator pushes air into the lungs

• reduced diaphragmatic activity: during controlled ventilation, the diaphragm is inactive or minimally active

• compression of dependent lung regions: gravity and surrounding tissues reduce lung expansion, particularly in supine patients

• reduced regional compliance: compressed or collapsed dependent lung regions are harder to inflate

When someone is lying supine and is on a mechanical ventilator, where would the air in the lungs tend to go?

In the anterior portion of the lungs, (the non-dependent portion)

What can contribute to V/Q mismatch and impaired oxygenation?

Reduced ventilation to dependent lung regions, despite continued perfusion

What respiratory effects of surgery can the combination of general anesthesia, mechanical ventilation, and surgical positioning have?

Decreased lung volumes (FRC), decreased ventilation to dependent lung regions, increased risk of atelectasis, and V/Q mismatch and impaired oxygenation

Following a 4-hour surgery under general anesthesia in the supine position, which lung regions would you expect to have reduced ventilation, and what might you hear on auscultation?

• posterior area of lungs (at the anatomical base) would be the dependent region

• auscultation: decreased breath sound intensity over bilateral posterior lung bases; FIC may be present, particularly if small airways reopen during inspiration

Following a 5-hour surgery in the left side-lying position, which lung regions would you expect to have reduced ventilation, and what might you hear on auscultation?

• dependent region: left side (particularly basal/dependent regions)

• auscultation: decreased breath sound intensity over the left/dependent lung, FIC may also be present

Why is it important to consider surgical incision types?

Upper abdominal and thoracic incisions can affect structures involved in breathing and coughing (much more likely than incisions at the extremities)

Types of incisions used in thoracic and abdominal surgeries

Median sternotomy, thoracotomy, midline abdominal incision, and clamshell incision

Median sternotomy

Incision through the sternum (does not really cut through respiratory muscles (still painful to deep breath/cough))

Thoracotomy

Incision between the ribs (common for lung surgeries)

Midline abdominal incision

Incision through the abdominal wall (issue since we need abs for a forceful cough)

Clamshell incision

Bilateral incision across the chest

Guarding

Pain-related protection that limits movement or breathing

How surgical incisions affect lung function

1. pain and guarding

2. muscle disruption/inhibition

3. restricted chest/abdominal expansion

Pain and guarding

• shallow breathing and reduced chest expansion

• reluctance to deep breath, cough, or mobilize

Muscle disruption/inhibition

• decreased intercostal and/or abdominal muscle function

• decreased chest wall movement and cough effectiveness

Restricted chest/abdominal expansion

• limits deep inspiration and lung expansion

What is the overall effect of surgical incisions affecting lung function?

Decreased lung volumes and impaired cough which increases the risk of atelectasis and retained secretions

Why does incision location matter?

Upper abdominal and thoracic incisions are particularly relevant because they are close to or involve structures important for breathing and coughing

clinical takeaway: the type and location of the incision can help predict postoperative respiratory impairments

Goal for physiotherapy before surgery

• educate and prepare the patient

• teach breathing and support/splinted cough

• identify risks and consider - p

Goal for physiotherapy after surgery

• promote lung expansion

• support effective coughing and secretion clearance

• encourage early mobilization

• coordinate pain management to facilitate participation